JP3085192B2 - Engine exhaust gas purifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an exhaust gas purifying apparatus suitable for use in removing x, and more particularly to an exhaust gas purifying apparatus for an engine capable of regenerating an exhaust gas purifying catalyst as required by controlling the temperature of the exhaust gas purifying catalyst. About.

[0002]

2. Description of the Related Art There is an engine such as an internal combustion engine (hereinafter referred to as an engine) mounted on an automobile that burns a lean air-fuel mixture. In such an engine, the amount of NOx in exhaust gas during lean operation is increased. Increase. Therefore, in order to purify exhaust gas in such an engine, a lean NOx catalyst or lean N
In some cases, an Ox catalyst and a three-way catalyst are installed in combination.

In such a lean NOx catalyst, a NOx absorbent that absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean, and releases the absorbed NOx when the oxygen concentration in the inflowing exhaust gas decreases, is provided in the exhaust passage. The NOx generated when the lean mixture is burned is absorbed by the NOx absorbent, and the air-fuel ratio of the exhaust gas flowing into the NOx absorbent is temporarily rich before the NOx absorption capacity is saturated. In some cases, NOx is reduced from the NOx absorbent and released.

Since sulfur is contained in fuel and lubricating oil of an engine, the exhaust gas also contains sulfur such as sulfate (hereinafter simply referred to as sulfur), and this sulfur also absorbs NOx together with NOx. Absorbed by the agent. However, this sulfur is not released from the NOx absorbent even if the air-fuel ratio of the exhaust gas flowing into the NOx absorbent is made rich, so that the amount of sulfur in the NOx absorbent gradually increases, and this sulfur is absorbed. As the amount increases, the amount of NOx that can be absorbed by the NOx absorbent gradually decreases, and eventually the NOx absorbent can hardly adsorb NOx.

[0005] The sulfur absorbed by the NOx absorbent is NO
When the x-absorbent is heated, it is decomposed and released from the NOx absorbent, and at this time, when the air-fuel ratio is made rich or stoichiometric, the sulfur released from the NOx absorbent becomes unburned HC in the exhaust gas. It is immediately reduced by CO and CO. Therefore, for example, in the technique disclosed in Japanese Patent Application Laid-Open No. 6-66129, attention is paid to such characteristics, and when a specific condition is satisfied, the NOx absorbent is heated to perform a rich operation or a stoichiometric operation. NO
It is configured to release sulfur from the x-absorbent, further reduce it, and discharge it. The specific conditions in this case are:
This is because the amount of sulfur absorbed by the NOx absorbent has reached a predetermined amount, and the temperature of the NOx absorbent is raised by operating an electric heater installed in the exhaust system.

[0006]

However, the above-described conventional exhaust gas purifying apparatus for an engine has the following problems. That is, the regeneration time of the lean NOx catalyst (that is, the release time of sulfur from the NOx absorbent) is NOx
It is set when the amount of sulfur absorbed by the absorbent reaches a predetermined amount. However, since the amount of sulfur absorbed cannot be directly detected, the lean NO
Even if the x catalyst cannot be regenerated and the amount of sulfur absorbed exceeds the absorption limit and the lean NOx catalyst can hardly adsorb NOx, the regeneration may not be performed.

That is, in the prior art, it is considered that the amount of the absorbed sulfur corresponds to the traveling distance of the vehicle, and when the traveling distance of the vehicle reaches a predetermined distance, the amount of the absorbed sulfur reaches the predetermined amount. It is estimated that the lean NOx catalyst has been regenerated based on the estimation. However, the amount of sulfur absorbed by the NOx absorbent does not always correspond to the traveling distance of the vehicle, and varies according to the fuel used and the operating condition of the engine. Therefore, the accuracy of the estimated amount of sulfur is not sufficient. The regeneration time of the lean NOx catalyst cannot be properly determined, and the time point of sulfur removal regeneration may be delayed.

Further, there is another problem that the fuel efficiency is deteriorated because the air-fuel ratio is changed from lean to rich or stoichiometric during running. Furthermore, in order to raise the temperature of the NOx absorbent,
Since a heating means such as an electric heater is provided in the exhaust system, an extra device is required for the apparatus, and there is a problem that the configuration of the apparatus becomes complicated and a cost increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been proposed for a lean NOx catalyst by a simple device configuration without causing an increase in cost and without deteriorating fuel consumption during traveling. An engine exhaust gas purifying system that ensures the removal of catalytic performance reducing substances such as sulfur before a large amount of catalytic performance reducing substances adhere to them, thereby ensuring exhaust gas purification performance. The purpose is to provide.

[0010]

According to the present invention, there is provided an exhaust gas purifying apparatus for an engine according to the present invention, comprising: an exhaust gas purifying catalyst disposed in an exhaust passage of the engine; Engine start detecting means for detecting, catalyst temperature increasing means for supplying fuel to the exhaust passage or upstream of the catalyst to increase the temperature of the exhaust gas purifying catalyst, and based on detection information from the engine start detecting means. Immediately after the start of the engine, the catalyst temperature raising means is operated and the air-fuel ratio is reset.
The starting catalyst regeneration control means for regenerating the catalyst by switching to a stoichiometric state or a stoichiometric state is provided.

According to a second aspect of the present invention, there is provided an exhaust gas purifying apparatus for an engine according to the first aspect, wherein
Catalyst temperature detecting means for detecting the temperature;
Immediately after the start of the engine based on the detection information from the output means
During the warm-up operation, the amount of fuel added to the combustion chamber of the engine is increased.
Fuel supply control means for controlling the fuel supply; and means for raising the temperature of the catalyst through the fuel supply control means.
Immediately after starting the gin,
By further performing control to add increased, by burning fuel to supply fuel to the exhaust passage or the catalyst upstream and the start catalyst regeneration control means, the catalyst temperature detected hand
Based on the stage and the detection information from the engine start detection means, through the fuel supply control means to start Dogo of the engine
Empty due to fuel supply in the exhaust passage or upstream of the catalyst
The fuel ratio is rich or stoichiometric .

[0012] exhaust gas purifying device for an engine of the present invention described in claim 3 is the apparatus of claim 2, wherein said catalyst temperature
Temperature means based on the detection information from the catalyst temperature detection means and the engine start detection means, when the temperature of the catalyst at the time of starting the engine is equal to or lower than a first predetermined temperature,
Until the temperature of the catalyst reaches a second predetermined temperature higher than the first predetermined temperature, the catalyst is added to the warming-up fuel increase to further increase the fuel by a certain amount. And

According to a fourth aspect of the present invention, there is provided the exhaust gas purifying apparatus for an engine according to the second or third aspect.
When the temperature of the catalyst at the time of starting the engine is equal to or higher than a first predetermined temperature based on detection information from the catalyst temperature detecting means and the engine start detecting means, After the end of the fuel supply control for use, the fuel is increased so that the air-fuel ratio becomes rich or stoichiometric until the temperature of the catalyst reaches a second predetermined temperature higher than the first predetermined temperature. It is characterized by having.

According to a fifth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an engine according to the first aspect of the present invention, wherein the catalyst temperature raising means introduces secondary air into the exhaust passage so that the inside of the exhaust passage is formed. or it is characterized by containing unburned fuel combustion catalyst secondary air supply means for heating to raise the temperature of the exhaust gas purifying catalyst to promote the in the catalyst upstream.

According to a sixth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an engine according to the first aspect, wherein the exhaust gas purifying catalyst is constituted as an exhaust gas purifying lean NOx catalyst. Catalyst temperature detecting means for detecting a temperature, catalyst temperature increasing means for raising the temperature of the lean NOx catalyst to a predetermined temperature or higher immediately after the start of the engine, based on detection information from the engine start detecting means,
Based on the detection information from the catalyst temperature detecting means, is characterized in that the temperature of the lean NOx catalyst and a start catalyst regeneration control means for playback of the lean NOx catalyst upon reaching the predetermined temperature .

[0016]

[0017]

According to a seventh aspect of the present invention, there is provided an exhaust gas purifying apparatus for an engine, wherein the exhaust gas purifying lean NOx catalyst is disposed in an exhaust passage of the engine, and engine start detecting means for detecting start of the engine. A catalyst temperature detecting means for detecting a temperature of the lean NOx catalyst, and a start-up time of the engine based on detection information from the engine start detecting means.
A catalyst temperature raising means for raising the temperature of the lean NOx catalyst to a predetermined temperature or more later;
Fuel supply means for supplying fuel to the upstream side of the catalyst, and the lean N based on detection information from the catalyst temperature detection means.
When the temperature of the Ox catalyst reaches the predetermined temperature, the lean NO
a start catalyst regeneration control means for playback of the x catalyst, provided the playback time setting means for setting the time of the reproduction of the lean NOx catalyst according to the start catalyst regeneration control means, the regeneration time setting means, when said start-up based on the engine OPERATION time after the last of the lean NOx catalyst regeneration by the catalyst regeneration control means it is characterized by being configured to set the current of the lean NOx catalyst regeneration time.

According to an eighth aspect of the present invention, in the exhaust gas purifying apparatus for an engine according to the seventh aspect of the present invention, the regeneration time setting means is configured to perform actual regeneration with respect to a previous set time of the lean NOx catalyst regeneration time. the if execution time of performing is insufficient, so on the basis of the OPERATION time of the engine after the lack of time and the previous lean NOx catalyst regeneration, to set the current of the lean NOx catalyst regeneration time It is characterized by being constituted.

According to a ninth aspect of the present invention, in the exhaust gas purifying apparatus for an engine according to the sixth aspect, the engine is a V-type engine having two left and right banks.
The catalyst regeneration means is constituted by fuel supply control means for controlling so as to enrich or stoichiometric the air-fuel ratio to the cylinder of one bank and to lean the air-fuel ratio to the cylinder of the other bank. It is characterized by.

According to a tenth aspect of the present invention, there is provided an exhaust gas purifying apparatus for an engine according to the sixth aspect, wherein the engine is a direct injection engine for directly injecting fuel into a combustion chamber. It is characterized in that the regeneration control means is constituted by fuel supply control means for injecting fuel into the combustion chamber in the exhaust stroke to enrich or stoichiometric the air-fuel ratio to fuel supply. The exhaust gas purifying apparatus for an engine according to the present invention according to the eleventh aspect is the first aspect.
In the above-described apparatus, the start-time catalyst regeneration control means activates the catalyst temperature raising means immediately after the start of the engine based on the detection information from the engine start detection means, and thereafter makes the air-fuel ratio rich or stoichiometric. In this case, the catalyst is regenerated . Claim 12
The exhaust gas purifying apparatus for an engine according to the present invention described above includes an exhaust gas purifying lean N disposed in an exhaust passage of the engine.
Ox catalyst, engine start detecting means for detecting the start of the engine, cooling water temperature detecting means for detecting the cooling water temperature of the engine, and starting of the engine based on the detection information from the engine start detecting means. Immediately thereafter, control for increasing the amount of fuel to the combustion chamber of the engine for warm-up operation is performed, and based on the detection information from the cooling water temperature detecting means and the engine start detecting means, the engine is started when the engine is started. When the cooling water temperature is equal to or lower than the first predetermined temperature, the second cooling water temperature is higher than the first predetermined temperature.
Of to reach a predetermined temperature allowed to warm to the lean NOx catalyst by performing a further quantity of fuel increase as added to the fuel increase for air 該暖, when starting of the engine
The cooling water temperature of the engine at the first predetermined temperature
In the above cases, the fuel should be added to the warm-up fuel.
Immediately after performing a certain amount of fuel increase, the cooling water
The temperature reaches a second predetermined temperature higher than the first predetermined temperature
Until the air-fuel ratio becomes rich or stoichiometric
By increasing the fuel, the lean NOx catalyst is raised.
The fuel supply control device is characterized in that it has a fuel supply control means for heating. According to a thirteenth aspect of the present invention, the exhaust gas purifying apparatus for an engine is disposed in an exhaust passage of the engine.
Lean NOx catalyst for purifying exhaust gas and starting of the engine
Start detection means for detecting the temperature of the engine, and cooling of the engine
A cooling water temperature detecting means for detecting a water temperature;
Based on the detection information from the motion detection means.
Fuel to the combustion chamber of the engine for warm-up operation immediately after operation.
First fuel supply control means for performing an increase control;
Detection means and detection information from the engine start detection means
On the basis of the
If the cooling water temperature is equal to or lower than the first predetermined temperature, the first fuel
Immediately after the warming-up fuel increase by the fuel supply control means ends, the
A second predetermined temperature at which the cooling water temperature is higher than the first predetermined temperature;
Until the air / fuel ratio becomes rich or stoichiometric.
The lean NOx is increased by increasing the fuel
And second fuel supply control means for raising the temperature of the catalyst.
It is characterized in that that.

[0022]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an exhaust gas purifying apparatus for an engine according to a first embodiment of the present invention; FIG. The configuration of an engine (internal combustion engine) provided with the present exhaust gas purifying device is as shown in FIG. 3. The engine 70 is of a spark ignition type, and in the case of this embodiment, fuel is contained in a combustion chamber. As a direct injection engine. An intake passage 2 and an exhaust passage 3 are connected to the combustion chamber 1 so that they can communicate with each other. The communication between the intake passage 2 and the combustion chamber 1 is controlled by an intake valve 4, and the exhaust passage 3 and the combustion chamber 1 are connected to each other. Is the exhaust valve 5
Communication control.

In the intake passage 2, an air cleaner 6 and a throttle valve 7 are provided in order from the upstream side.
The exhaust passage 3 is provided with an exhaust gas purifying catalytic converter 9 as an exhaust gas purifying catalyst and a muffler (muffler) (not shown) in order from the upstream side. The intake passage 2 is further provided with a surge tank 2a.

The opening of the throttle valve 7 changes in accordance with the amount of depression of an accelerator pedal (not shown). The throttle valve 7 is further opened and closed by an idle speed control motor (ISC motor), not shown. Thus, the opening of the throttle valve 7 can be changed without depressing the accelerator pedal during idling.

An injector (fuel injection valve) 8 is arranged so that its opening faces the combustion chamber 1 so as to directly inject fuel toward the combustion chamber 1 in the cylinder. Naturally, the injectors 8 are provided for each cylinder. For example, if the engine 70 of the present embodiment is an in-line four-cylinder engine, four injectors 8 are provided.

With this configuration, the air sucked through the air cleaner 6 according to the opening degree of the throttle valve 7 is sucked into the combustion chamber 1 by opening the intake valve 4, and the air sucked inside the combustion chamber 1 And the fuel directly injected from the injector 8 are mixed, and the ignition plug 35
Is ignited at an appropriate timing to cause combustion and generate an engine torque. Then, the air-fuel mixture is discharged to the exhaust passage 3 as exhaust gas, and the CO, HC, and NOx in the exhaust gas are exhausted by the catalytic converter 9. After purifying the two harmful components, they are muffled by mufflers and released to the atmosphere.

In particular, as will be described later, the present engine is an engine capable of performing a saving operation while keeping the air-fuel ratio lean. At the time of the lean operation, NOx in the exhaust gas cannot be reduced only by the three-way catalyst. 9 is a combination of a lean NOx catalyst 9A and a three-way catalyst 9B. By the way, the engine will be further described.
The intake air flow flowing into the inside is formed so as to form a vertical vortex (reverse tumble flow), and in the combustion chamber 1, the intake air flow forms such a vertical vortex. Fuel can be collected only in the vicinity of the spark plug 35 disposed in the center of the top of the chamber 1 and an extremely lean air-fuel ratio state can be achieved in a portion separated from the spark plug 35. Only the vicinity of the spark plug 35 is ignited. By setting the air-fuel ratio to be easy to perform, fuel consumption can be suppressed while achieving stable combustion.

In particular, since this engine is an in-cylinder injection engine, there is no restriction on the timing of fuel injection, and fuel injection can be performed at a timing most suitable for realizing the above-described uneven distribution of fuel. It is known that the optimal fuel injection timing in this case is the latter stage of the compression stroke in which the air flow is weak. In order to obtain a high output from the engine, the combustion may be performed by bringing the entire combustion chamber 1 into an air-fuel mixture with an optimum output air-fuel ratio. In this case, too, the atomization and vaporization of the fuel is sufficient. By performing the fuel injection at such a timing as to be performed, a high output can be obtained efficiently. It is known that the optimum fuel injection timing in this case is set so as to end the fuel injection at the beginning or the first half of the intake stroke so as to promote the atomization and vaporization of the fuel by utilizing the intake flow. ing.

Various sensors are provided to control the engine 70. First, intake passage 2
On the side of the air cleaner, an air flow sensor 11, which detects the intake air amount from Karman vortex information, an intake air temperature sensor 12, which detects the intake air temperature, and an atmospheric pressure sensor 13, which detects the atmospheric pressure, are provided at the portion where the air cleaner is provided. The throttle valve is provided with a potentiometer type throttle sensor 14 for detecting the opening of the throttle valve 7, an idle switch 15 for detecting an idling state, and the like.

On the exhaust passage 3 side, an oxygen concentration sensor 17 (hereinafter simply referred to as an O ₂ sensor 1) for detecting an oxygen concentration (O ₂ concentration) in the exhaust gas is provided upstream of the catalytic converter 9.
7) is provided. Further, as other sensors, a water temperature sensor 19 for detecting an engine cooling water temperature and a crank angle sensor 21 for detecting a crank angle as shown in FIG. 2 (the crank angle sensor 21 also serves as a rotation speed sensor for detecting an engine rotation speed). ) And a TDC sensor (cylinder discrimination sensor) 22 for detecting the top dead center of the first cylinder (reference cylinder) are provided in the distributor, respectively.

The detection signals from these sensors are input to an electronic control unit (ECU) 23. The ECU 23 receives a voltage signal from an accelerator position sensor 24 for detecting the amount of depression of the accelerator pedal, a voltage signal from a battery sensor 25 for detecting the voltage of the battery, a cranking switch 20 for detecting the start time, or an ignition switch (key switch). Is also input.

The hardware configuration of the ECU 23 is as shown in FIG. 2. The ECU 23 has a CPU 27 as its main part.
Intake air temperature sensor 12, atmospheric pressure sensor 13, a throttle sensor 14, O ₂ sensor 17, water temperature sensor 19, via a detection signal input interface 28 and the A / D converter 30 from an accelerator position sensor 24 and a battery sensor 25 inputs At the same time, detection signals from the airflow sensor 11, the crank angle sensor 21, the TDC sensor 22, the idle switch 15, the cranking switch 20, the ignition switch, and the like are input via the input interface 29.

Further, the CPU 27 has a ROM for storing program data and fixed value data via a bus line.
31, a RAM 32 that is updated and rewritten sequentially, a free running counter 48, and a battery backup RAM (not shown) that is backed up while the battery is connected by holding the stored contents while the battery is connected. It gives and receives.

The data in the RAM 32 is erased and reset when the ignition switch is turned off. The fuel injection control signal based on the calculation result by the CPU 27 is transmitted to the solenoid (injector solenoid) 8a of the injector 8 (more precisely, as shown in FIG. 4) via four injection drivers (fuel injection valve driving means) 34. Transistor 8b for injector solenoid 8a)
Output to

Further, when this ECU 23 is shown in detail,
As shown in FIG. That is, as shown in FIG. 4, the ECU 23 includes a CPU 27, a ROM 31, and a RAM 3.
It comprises a microcomputer having two and a plurality of ports 46, and has a cylinder discriminating external register (flip-flop) 47, a free-running counter 48, registers 49 to 52, comparators 53 to 56 and RS flip-flops 57 to 57. 60 and the like.

The output signal of the air flow sensor 11 is input to an interrupt terminal INT2 of the CPU 27, and the crank phase signal from the crank angle sensor 21 is shaped into a rectangular wave by a waveform shaping circuit as an input interface.
7 is input to an interrupt terminal INT1. Further, the cylinder discrimination signal from the cylinder discrimination sensor 22 is shaped into a rectangular wave by a waveform shaping circuit as an input interface,
, The intake air temperature sensor 13, the atmospheric pressure sensor 13, O
The signals from the _two sensors 17, the water temperature sensor 19, etc. are adjusted to an appropriate level by a level adjustment circuit as an input interface, are converted from analog to digital by the analog / digital converter 30, and are input to the port 46. ing.

The injector 8 is controlled by a switching transistor 8b to turn on and off power supplied from a DC power supply (battery) to a valve opening / closing injector solenoid 8a. Focusing on fuel injection control (air-fuel ratio control), a fuel injection control signal calculated by the CPU 27 is output via the driver 34,
For example, four injectors 8 are sequentially driven.

In particular, due to the characteristics of the in-cylinder injection engine described above, in this engine, as a mode of fuel injection, late injection in which fuel injection is performed in the second half of the compression stroke in order to realize operation by lean combustion (lean operation). In order to realize an operation based on stoichiometric air-fuel ratio (stoichiometric) combustion (stoichiometric operation), a first-stage injection mode is provided in which fuel injection is terminated at the beginning or at the beginning of the intake stroke. During the stoichiometric operation, if the amount of fuel to be supplied is large, the fuel injection may be started from the latter or last stage of the exhaust stroke and may be ended in the early or early stage of the intake stroke.

Further, in order to realize the operation by rich combustion (rich operation), the fuel injection is performed in the latter or final stage of the exhaust stroke in the stoichiometric operation by extending the injection time. Therefore, during rich operation, fuel is generally injected from the latter half of the exhaust stroke to the earlier half of the intake stroke. For such fuel injection control (injector drive control), the CPU
In 27, a fuel supply control means 101 for selecting an injection mode and setting a fuel injection amount is provided.

As shown in FIG. 1, the fuel supply control means 101 has a function of performing control at the time of starting (starting time control means).
102 and a function (control means during normal operation) 103 for performing control during normal operation after start-up are provided, and the control means 102 at start-up is applied to the present exhaust gas purification apparatus. The start time control means 102 includes a signal (start detection information) from the cranking switch 20 or an ignition switch (key switch) for detecting the start time as the engine start detection means, and a water temperature sensor (water temperature) also used as the catalyst temperature detection means. Based on a detection signal (water temperature detection information) from 19, a detection signal from an accelerator position sensor 24 (accelerator opening information), and a detection signal from a vehicle speed sensor 10 (vehicle speed information), selection of an injection mode and fuel The setting of the injection amount is performed.

The start-time control means 102 includes a warm-up fuel supply control means (second fuel supply control means ) for warming up the engine at the start .
(1) fuel supply control means) 104; and a catalyst temperature raising fuel supply control means (second fuel supply control means) as a catalyst temperature raising means for raising a required temperature of the catalyst 9 at the time of startup.
And a catalyst regeneration enrichment means 106 as a start-up catalyst regeneration control means for guiding a fuel in an air-fuel ratio rich state or a stoichiometric state to the catalyst heated to a required temperature for a predetermined time to activate and regenerate the catalyst. Is provided. The start time control means 102 and a reproduction time setting means 10 described later
7 and the like constitute a starting catalyst regeneration control means 100.

When the warm-up fuel supply control means 104 receives a start signal from the cranking switch 20 or an ignition switch (key switch), the engine coolant temperature Tw detected by the water temperature sensor 19 at this time.
The fuel increase control for warm-up is performed such that the fuel injection amount is increased from the amount during normal operation only for a time corresponding to. That is,
As shown by the curves A1 and B1 in FIGS. 5 and 6, the fuel injection amount is increased only one time immediately after the start, compared to the normal fuel injection amount indicated by the straight line S, so that the intake air to the engine is enriched or stoichiometric. By promoting combustion, the fuel supply is controlled so that the engine is quickly warmed up to a predetermined temperature range.

The period during which the combustion is increased (warm-up period) is in accordance with the engine cooling water temperature Tw. For example, if the water temperature Tw is low, the fuel increase period is reduced as shown by the curve A1 in FIG. If the water temperature Tw is high,
As shown by the curve B1, the fuel increase period becomes shorter. This means that if the water temperature Tw is high, the engine temperature is high,
This is because there is no need to warm up.

In the catalyst temperature increasing fuel supply control means 105,
This is to raise the temperature of the lean NOx catalyst 9A of the catalyst 9, and this temperature rise is caused by the lean NOx catalyst 9A.
This is performed in order to decompose the sulfur content (hereinafter, simply referred to as sulfur) such as sulfate absorbed therein and to release the sulfur component from the lean NOx catalyst 9A. That is, sulfur SO ₂ in the exhaust gas surface in O ₂ of the platinum Pt in the catalyst ^- absorption react with SO _3, and the then the NOx absorbent in the lean NOx catalyst 9A while the SO ₃ is further oxidized Then, while being bonded to barium oxide BaO, it diffuses into the NOx absorbent in the form of sulfate ions SO ₄ ²⁻ . Further, the sulfate ion SO ₄ ²⁻ binds to the barium ion Ba ²⁺ and is fixed to the NOx absorbent in the form of a sulfate salt of barium sulfate BaSO ₄ . Since such sulfates are stable, NOx
It is difficult to decompose simply by making the air-fuel ratio of the exhaust gas flowing into the NOx absorbent rich like the release of NOx. NO
The larger the amount of sulfate attached to the x absorbent, the smaller the amount of NOx that can be absorbed by the NOx absorbent.

However, sulfate has a property that it is easily decomposed when heat is applied. For example, the sulfate ion SO ₄ ^2- in the NOx absorbent changes into the form of SO _{3 when} heated,
Released from the Ox absorber. Therefore, the catalyst temperature increasing fuel supply control means 105 further increases the amount of fuel supplied to the engine to promote the enrichment or stoichiometry of the intake air, thereby promoting the combustion of the engine and reducing the exhaust gas from the engine. The temperature of the lean NOx catalyst 9A in the exhaust passage 3 is increased by increasing the temperature.

The amount of fuel for raising the temperature of the catalyst 9A is added to the amount of fuel for warming up by the warming-up fuel supply control means 104 as shown by a curve A2 in FIG. This additional fuel increase for increasing the catalyst temperature is performed until the water temperature Tw reaches a predetermined temperature during warm-up.
If the warm-up time (fuel increase time for warm-up) is long, the additional fuel can be sufficiently increased to raise the temperature of the catalyst to a predetermined temperature, but if the warm-up time is short, the additional fuel cannot be sufficiently increased and the catalyst needs to be increased. Cannot rise to temperature.

Therefore, when the warm-up time is short, as shown in FIG. 6, in addition to the additional fuel increase during warm-up (see curve B2), after the warm-up is completed, a curve such as a so-called rich spike is formed. As shown by C, fuel is temporarily added to make the air-fuel ratio rich or stoichiometric. Since the warm-up time is in accordance with the engine coolant temperature Tw, the catalyst temperature increasing fuel supply control means 105 of the present embodiment, for example, sets the coolant temperature Tw to a first set value (first
Of when a given temperature) Tw ₁ or more, as shown in FIG. 6, performs the rich spike after warm-up completion, the water temperature T
When w is less than the _first set value Tw1, as shown in FIG. 5, this rich spike is not performed and only the additional fuel increase during warm-up is performed. In any case, the water temperature Tw is equal to the second set value (second predetermined temperature) Tw ₂ (> T
When w ₁ ) is reached, the rich spike and the additional fuel increase are ended.

In the catalyst regeneration enriching means 106, when the NOx absorbent in the lean NOx catalyst 9A is sufficiently heated, the engine is operated in a rich or stoichiometric air-fuel ratio to purify exhaust gas. Lean NOx catalyst 9
A is to be reproduced. That is, when the temperature of the NOx absorbent rises sufficiently, the sulfate ions SO ₄ ²⁻ in the NOx absorbent change into the form of sulfur oxide SO ₃ and are released from the NOx absorbent, but this is harmful as it is. .

Therefore, the catalyst regeneration enriching means 106 removes the exhaust gas from the rich operation or the stoichiometric operation when the temperature of the NOx absorbent rises (when the water temperature Tw becomes equal to or higher than the second set value Tw ₂ ). Sulfur SO released from the NOx absorbent by flowing into the lean NOx catalyst 9A
₃ is immediately reduced by unburned HC and CO in the exhaust gas to make it harmless and then released together with the exhaust gas. Thereby, the lean NOx catalyst 9A
Regenerates to a state where NOx can be sufficiently absorbed.

The catalyst regeneration enrichment means 106
, The time Tra during which the air-fuel ratio is made rich or stoichiometric for catalyst regeneration is set by the regeneration time setting means 107, and the catalyst regeneration enriching means 106 is used for the set regeneration time Tra. The regeneration of the catalyst is performed, and after the regeneration time Tra elapses, the operation shifts to the normal operation.

Of course, during the rich operation, as described above,
The enrichment is realized by extending the injection time by performing the fuel injection in the latter or final stage of the exhaust stroke with respect to the stoichiometric operation. As shown in FIG. 7, for example, the regeneration time setting means 107 is configured to set the regeneration time Tra according to the integrated value Td of the running time since the previous catalyst regeneration. In the present apparatus, the catalyst is always regenerated at the time of starting. Therefore, the integrated value Td of the running time after the previous regeneration is the integrated value of the running time from the previous start to the stop of the engine (that is, the engine operation). Hours) .

However, the regeneration of the catalyst by the catalyst regeneration enriching means 106 is performed in the case where the driver performs a start operation after the start, even if the regeneration time Tra has not elapsed, and the catalyst regeneration is terminated. It is supposed to shift to. This is designed so that the enrichment or stoichiometry of the fuel for catalyst regeneration does not impair the operation feeling during normal operation. Here, the start operation by the driver is detected by using the accelerator opening θ _ACC and the vehicle speed V, and the accelerator opening θ _ACC becomes a predetermined value θ ₀ (θ ₀
Is a positive value close to 0) or the vehicle speed V is a predetermined value V ₀
When (V ₀ is a positive value close to 0) or more, the driver performs the start operation.

As described above, in some cases, the regeneration of the catalyst cannot be performed for the set regeneration time Tra, so that the regeneration time setting means 107 detects the actual regeneration time Trr and compares the actual regeneration time Trr with the actual regeneration time Trr. Set playback time Tra
Correction means 1 for calculating the difference ΔTr (= Tra−Trr) from the above and adding the difference ΔTr to the reproduction time Tra based on the integrated value Td of the traveling time [Tra = Tra (Td) + ΔTr].
07A is provided.

As a result, the reproduction time setting means 107
Will always set the required playback time
ing. Also, during catalyst regeneration, this can be recognized by the driver.
The catalyst regeneration indicator lamp 108 is provided
You. The normal operation control means 103 will be described.
In the normal operation control means 103, the injection mode is set to the engine
Revolution speed (rotation speed) Ne and accelerator pedal depression amount θ _ACC
The target output torque T of the engine is set based on
In accordance with the gin rotation speed Ne and the target output torque T,
Select either injection mode or late injection mode.
Set selectively. For example, if the engine speed Ne is low
In the region where the target torque T is also low, the latter injection mode is set,
One of the rotation speed Ne and the target torque T must be low
For example, the injection mode is set to the former period.

Regarding the fuel injection amount, the fuel injection time (which is the driving time of the injector and is referred to as the injector driving pulse width in actual control) Pw (n) [mse
c], and in both the first-stage injection mode and the second-stage injection mode, the intake air amount (intake air amount per stroke) Q _AIR and the target air-fuel ratio (A / F, hereinafter A
F), and is calculated by, for example, the following equation (1).

[0056] _{Pw (n) = {Q AIR} × α AIR / (α FUEL × AF)} × (1 / G INJ) × K × 1000 + T D ··· (1) Note that in the above equation (1), Q _AIR is an intake air amount per stroke [liter / stroke], which can be calculated based on a detection signal from the air flow sensor 11;
α _AIR is the air density, α _FUEL is the fuel density, and G _INJ is the injector gain [cc / sec]. K is various fuel correction coefficients. T _D is the injector dead time (dead time) [msec]. It should be noted that the first of the above equation (1)
The term relates to the basic drive time Tb, and the various fuel correction coefficients K are detected by the engine cooling water temperature detected by the water temperature sensor 19, the intake air temperature detected by the intake air temperature sensor 12, and detected by the atmospheric pressure sensor 13. It is set according to the set atmospheric pressure or the like.

Since the exhaust gas purifying apparatus for an engine according to the first embodiment of the present invention is configured as described above, the catalytic converter 9 is regenerated every time the engine is started, for example, as shown in FIG. . In other words, the engine start control according to the regeneration of the catalyst converter 9 is started, first, (step from the detection information from the water temperature sensor 19, which whether the cooling water temperature Tw is the second set value Tw ₂ or more is determined A10).

Immediately after the engine is turned off, the cooling water temperature Tw becomes equal to or higher than the second set value Tw ₂ , and step A 70
Proceeds to, since normally the cooling water temperature Tw is not in a second set value Tw ₂ or more, the routine proceeds to step A20, whether the cooling water temperature Tw is one less than the first set value Tw ₁ is determined . Here, when the cooling water temperature Tw is determined to be less than a first set value Tw _1, the routine proceeds to step A30, As shown in FIG. 5, combined with the warming-up fuel increase and the fuel increase for warm Do it. For example, the fuel correction coefficient K for increasing the warm-up fuel set to a characteristic corresponding to the curve A1 shown in FIG.
The fuel correction coefficient K for increasing the fuel for temperature rise is integrated in _AS , and the fuel injection time is set so that the fuel injection amount increases. Note that the fuel correction coefficient K for increasing the temperature-raising fuel
Is a value slightly larger than 1 (K = 1 to 2).

Such an increase in the temperature-raising fuel causes the temperature of the exhaust gas to rise due to the promotion of combustion, and raises the temperature of the catalyst 9. However, after the determination in step A40, the cooling water temperature Tw becomes the second temperature.
The fuel increase for temperature increase is performed until the set value Tw ₂ becomes equal to or more than the set value Tw ₂ . On the other hand, when the cooling water temperature Tw is determined not to be lower than the first set value Tw _1, the routine proceeds to step A50, in the form such as a so-called rich spike, as shown by curve C in FIG. 5, temporarily add fuel To make the air-fuel ratio rich or stoichiometric.

Such a rich spike can also be performed in step A
After the determination of 60, the cooling water temperature Tw becomes the second set value Tw ₂
Repeat until the above is reached. Thus, the cooling water temperature Tw
Becomes greater than or equal to the second set value Tw ₂ , the sulfur content (sulfate ion SO ₄ ²⁻ ) in the lean NOx catalyst 9A becomes (for example, S
(In the form of O ₃ ) to be released from the lean NOx catalyst 9A.

At this point, the catalyst regeneration enrichment means 10
According to 6, the rich operation of the engine for catalyst regeneration is performed (step A70). During this catalyst regeneration, the catalyst regeneration indication lamp 108 is turned on. That is, even if the sulfur is released from the lean NOx catalyst 9A, this sulfur is harmful in the form of, for example, sulfur oxide SO ₃ . Therefore, the catalyst regeneration enrichment means 106 converts the exhaust gas from the rich operation into the lean NOx catalyst 9 when the temperature of the NOx absorbent rises.
By flowing into A, the released sulfur SO ₃ is immediately reduced by the unburned HC and CO in the exhaust gas to make it harmless and then released together with the exhaust gas.

Thus, while purifying the exhaust gas, the lean NOx catalyst 9A is regenerated to a state where it can sufficiently absorb NOx. The rich operation of the catalyst regeneration engine, that is, the regeneration of the catalyst, is performed only for the time (regeneration time) Tra for which the air-fuel ratio set by the regeneration time setting means 107 is rich or stoichiometric. In the determination of step A80,
When the regeneration time Tra has elapsed since the start of the regeneration of the catalyst, the regeneration is terminated and the operation shifts to the normal operation.

If the driver performs a start operation before the regeneration time Tra elapses, the catalyst regeneration is immediately terminated and the operation shifts to a normal operation. That is, the accelerator opening θ _ACC exceeds the predetermined value θ ₀ or the vehicle speed V becomes the predetermined value V
_{If the value} exceeds _{0, it} is determined that the driver has performed the starting operation, and the operation immediately shifts to the normal operation in the determination of step A90.

By the way, in order to set the next playback time Tra, as shown in FIG.
The difference ΔTr is calculated by subtracting the actually performed reproduction time Trr from ra (step B10). The integrated value Td of the traveling time is calculated while integrating until the engine stop is determined in step B30 (step B20). On the other hand, when the current reproduction control is started, as shown in FIG. 10, a reproduction time Tra is set corresponding to the integrated value Td of the previous travel time (step C10), and the reproduction time Tra is calculated previously. The obtained difference ΔTr is added and corrected to obtain the final reproduction time Tra.
(= Tra + ΔTr).

The reproduction is performed for the reproduction time Tra thus set. In this way, in the exhaust gas purifying apparatus of the present engine, sulfur can be released from the lean NOx catalyst 9A easily and at low cost only by changing a part of the fuel injection software. Not when driving,
Since this can be realized by fuel injection control at the start,
The fuel efficiency is not deteriorated by making the air-fuel ratio rich or stoichiometric during running.

Further, since the temperature of the catalyst is raised together with the warm-up, the temperature can be raised without a sense of incongruity, and when the temperature rise of the catalyst at the same time as the warm-up is insufficient, the temperature of the catalyst is surely raised by the rich spike. be able to. Then, during catalyst regeneration, the catalyst regeneration display lamp 108 is lit, so that the driver can recognize this and can consciously perform catalyst regeneration.

Next, a description will be given of an exhaust gas purifying apparatus for an engine according to a second embodiment of the present invention. This embodiment is performed to reduce the amount of HC and CO in exhaust gas at the time of engine start. It uses a secondary air introduction system. That is, at the time of cold start of the engine, as described in the first embodiment, the engine is operated by increasing the fuel for warm-up and increasing the air-fuel ratio in order to smoothly start the engine. Therefore, there is a high possibility that the exhaust gas contains a large amount of HC and CO due to lack of oxygen. Therefore, a secondary air introduction system has been developed as a technique for oxidizing HC and CO in such exhaust gas by supplementing insufficient oxygen to the exhaust passage.

FIG. 11 is a schematic view showing an engine having a secondary air introduction system. In FIG. 11, the same reference numerals as those in FIG. 3 denote the same parts. As shown in FIG. 11, an exhaust gas purifying catalytic converter 9 is provided in the exhaust passage 3 of the engine. The catalytic converter 9 is disposed below the vehicle floor on the downstream side of the exhaust passage 3 and has a lean NOx
It comprises a catalyst 9A and a three-way catalyst 9B.

For the secondary air introduction system, an air cleaner (not shown) separate from the air cleaner section of the engine
Is introduced by an air pump 81 and sent as secondary air into the exhaust passage 3 upstream of the catalytic converter 9. The air pump 81
Is composed of an electric air pump. The supply of the secondary air to the exhaust passage 3 is controlled by an air control valve 82.
It is constituted so that it may be performed. The air control valve 82 is operated by the intake negative pressure in the intake passage 3, and is controlled to be opened and closed by a control unit 84 via a solenoid 83. Reference numeral 85 in FIG. 11 denotes a check valve for preventing secondary air backflow.

When the secondary air is supplied into the exhaust passage 3, the air control valve 82 is opened by the solenoid 83, and at the same time, the switch of the air pump 81 is turned on by the control unit 84, and
When the next air is not supplied into the exhaust passage 3, the air control valve 82 is closed by the solenoid 83, and at the same time, the switch of the air pump 81 is turned off by the control unit 84.

The control unit 84 controls the supply of the secondary air to the exhaust passage 3 during the cold start of the engine. Therefore, as shown in FIGS. 11 and 12, each detection signal from the water temperature sensor 19 for detecting the cooling water temperature and the cranking switch 20 for detecting the start of the engine is sent to the control unit 84.

By the way, such a secondary air introduction system copes with the fact that a large amount of HC and CO is generated in the exhaust gas due to an increase in the amount of fuel for warm-up at the time of cold start of the engine. However, if secondary air is supplied at such a low temperature start, excessive reaction heat is generated by the catalyst, and the temperature of the catalyst is raised. In particular,
When the temperature of the catalyst is increased by introducing the secondary air,
When the amount of the next air introduced is large, the effect of increasing the temperature increases as the temperature may exceed the allowable temperature of the catalyst.

Therefore, in the exhaust gas purifying apparatus of the present engine, as shown in FIG. 12, secondary air introduction control means (catalyst temperature increasing means) as a catalyst temperature increasing means for raising the required temperature of the catalyst 9 at the time of starting. A secondary air supply means) 115 is provided.
The next air introduction is used. In other words, the present exhaust gas purifying apparatus uses the lean N
By raising the temperature of the Ox catalyst to a predetermined temperature state and then supplying a rich or stoichiometric air-fuel mixture, a catalyst performance deteriorating substance such as sulfur adhering to the lean NOx catalyst is removed to remove the lean NOx catalyst. The regeneration is performed. If the temperature of the catalyst has not risen when the engine is started, secondary air is introduced as a catalyst temperature raising means.

On the other hand, since the original introduction of the secondary air is performed at the time of the cold start of the engine, it substantially coincides with the temperature rising timing of the catalyst. Therefore, the introduction of the secondary air is intended to reduce the amount of HC and CO that are increased in the exhaust gas due to an increase in the fuel for warming up.
It is possible to simultaneously raise the temperature of the catalyst. That is, in general, when the engine is started in a cold state, secondary air is introduced to increase the amount of fuel for warming up, and HC,
Although it is necessary to reduce CO, at the same time, the catalyst temperature is usually low when the engine is started in a cold state. Therefore, from the viewpoint of regenerating the catalyst, it is necessary to raise the temperature of the catalyst.

Therefore, by introducing secondary air at the time of cold start of the engine, it is possible to reduce HC and CO which increase in exhaust gas due to an increase in fuel for warm-up, and to raise the temperature of the catalyst. Can be done simultaneously. The secondary air introduction is performed at the same time as the fuel increase for warm-up is performed as intended, but in the present apparatus, another purpose of the secondary air introduction is to raise the temperature of the catalyst. In consideration of the period during which the warm-up fuel is increased (specifically,
(Time to end fuel increase for warm-up).

That is, the period during which the warm-up fuel is increased (warm-up period) is generally the engine coolant temperature T at the time of starting.
In the present apparatus, during the warm-up period, the amount of fuel for warm-up is increased while detecting the coolant temperature Tw of the engine until the coolant temperature Tw reaches the predetermined temperature Tw _2. It is supposed to do it. Of course, when increasing the fuel for warm-up, secondary air is introduced at the same time. The predetermined temperature Tw ₂ corresponds to the second set value Tw ₂ of the first embodiment.

Then, the cooling water temperature Tw becomes the predetermined temperature Tw ₂
Is reached, the increase of the fuel for warm-up and the introduction of the secondary air are stopped, and the enrichment means for catalyst regeneration 1 is stopped as in the first embodiment.
Activate 06. Accordingly, the introduction of the secondary air generally becomes longer as the cooling water temperature Tw becomes lower, and the introduction amount becomes larger. The operation of the catalyst regeneration enrichment means 106 causes the engine to operate in a state where the air-fuel ratio is rich or in a stoichiometric state. Thus, the exhaust gas containing unburned components such as HC and CO by such an operation causes a lean NOx catalyst. 9
A, and the sulfur content SO released from the NOx absorbent
₃ is immediately reduced by unburned HC and CO in the exhaust gas to make it harmless and then released together with the exhaust gas.

Of course, at the time of the rich operation, as described above, the fuel injection is performed in the latter or final stage of the exhaust stroke with respect to the stoichiometric operation to extend the injection time, thereby realizing the rich operation. The time for operating the catalyst regeneration enrichment means 106, that is, the regeneration time, is performed in the same manner as in the first embodiment.

Since the exhaust gas purifying apparatus for an engine according to the second embodiment is configured as described above, the catalyst is regenerated at the time of starting, for example, as shown in FIG. In other words, the engine start control according to the regeneration of the catalyst converter 9 is started, first, (step from the detection information from the water temperature sensor 19, which whether the cooling water temperature Tw is the second set value Tw ₂ or more is determined B10).

Immediately after the engine is turned off, the cooling water temperature Tw becomes equal to or higher than the second set value Tw ₂ , and step B 70
Proceeds to normally the cooling water temperature Tw is not in a second set value Tw ₂ or more, the program proceeds to step B30, is performed by combining the fuel increase and the secondary air introducing warm-up. By increasing the warming-up fuel and introducing the secondary air, the catalyst 9
Generates a large reaction heat and the temperature of the catalyst rises. However, after the determination in step A40, the cooling water temperature Tw becomes the second temperature.
The warm-up fuel increase and the secondary air introduction are performed until the set value Tw ₂ or more is reached. This is because the rise coolant temperature with Atsushi Nobori of the catalyst, when the cooling water temperature Tw becomes the second set value Tw ₂ or more, it is determined that the Atsushi Nobori of the catalyst is completed, the engine while converting exhaust gases The fuel increase for warming-up and the introduction of the secondary air, which are both used for warming-up and for raising the temperature of the catalyst, are ended.

As described above, when the cooling water temperature Tw becomes equal to or higher than the second set value Tw ₂ , the sulfur content (sulfate ion SO ₄ ²⁻ ) in the lean NOx catalyst 9A changes (for example, into the form of SO ₃ ). As a result, the lean NOx catalyst 9A is released. At this time, the rich operation of the catalyst regeneration engine is performed by the catalyst regeneration rich means 106 (step B70). During this catalyst regeneration, the catalyst regeneration indication lamp 108 is turned on.

That is, even if released from the lean NOx catalyst 9A, this sulfur is harmful in the form of, for example, sulfur oxide SO ₃ . Therefore, the catalyst regeneration enriching means 106, when raising the temperature of the NOx absorbent, can be blended into the exhaust gas by the rich operation to the lean NOx catalyst 9A, unburned in the exhaust gas sulfur SO ₃ released It is immediately reduced by HC and CO to make it harmless and then released together with the exhaust gas.

As a result, while purifying the exhaust gas, the lean NOx catalyst 9A is regenerated to a state where it can sufficiently absorb NOx. The rich operation of the catalyst regeneration engine, that is, the regeneration of the catalyst, is performed only for the time (regeneration time) Tra for which the air-fuel ratio set by the regeneration time setting means 107 is rich or stoichiometric. In the determination of step B80,
When the regeneration time Tra has elapsed since the start of the regeneration of the catalyst, the regeneration is terminated and the operation shifts to the normal operation.

If the driver performs the start operation before the regeneration time Tra has elapsed, the catalyst regeneration is immediately terminated and the operation shifts to the normal operation. That is, the accelerator opening θ _ACC exceeds the predetermined value θ ₀ or the vehicle speed V becomes the predetermined value V
If it exceeds _{0, it} is determined that the driver has performed the starting operation, and the operation immediately shifts to the normal operation in the determination of step B90.

Note that the regeneration time of the catalyst at each start-up is not limited to the setting as in each embodiment, and the control may be simplified by performing it for a fixed time set in advance. In this case, even before a certain time elapses,
When the driver performs the starting operation, the regeneration of the catalyst is terminated. In consideration of such a situation, it is desirable to set the time for regenerating the catalyst at each start-up (the above-mentioned fixed time) to be somewhat longer.

In each embodiment, the temperature of the catalyst 9 is used as a substitute.
In addition, since the engine coolant temperature is used, the catalyst 9
Although a dedicated sensor for detecting the temperature is not required, the catalyst 9
High temperature sensor that directly detects temperature (see the chain line block in Fig. 2)
) May be used to directly control the temperature of the catalyst.
In this case, a new high-temperature sensor is required,
Temperature Tw of cooling water for judgment₁, Tw_TwoFor judgment corresponding to
Catalyst temperature tw₁, Tw _TwoAnd set the same
Control can be performed in the same way,
Based on the control, catalyst regeneration can be performed more appropriately
There are advantages.

In each embodiment, the in-cylinder injection engine has been described as an example.
It can be widely applied to engines in which Ox generation is a problem. In particular, when the engine is a V-type engine having two banks on the left and right sides, the fuel supply control means makes the air-fuel ratio of the cylinder of one bank rich or stoichiometric during the catalyst regeneration, and the cylinder of the other bank By controlling the air-fuel ratio to be lean, the fuel supply control means can function as catalyst regeneration means.

That is, with this configuration, unburned substances are generated in the exhaust gas from the cylinder of one bank,
The unburned substances reduce the sulfur released from the lean NOx catalyst, and the lean NOx catalyst is regenerated. Further, at this time, the fuel consumption of the entire engine is suppressed by the lean operation of the other bank, and the lean NO.
It is possible to regenerate the x catalyst.

The point that the catalyst is regenerated when the engine is started is not limited to the lean NOx catalyst but can be widely applied to an exhaust gas purification catalyst.

[0090]

As described above in detail, according to the exhaust gas purifying apparatus for an engine according to the first aspect of the present invention, immediately after starting , the temperature of the exhaust gas purifying catalyst is raised together with the warming-up of the engine.
Since the air-fuel ratio is made rich or stoichiometric, regeneration by activation of the catalyst can be realized at each start.

Therefore, the catalyst is always kept in a state where the amount of the substance having reduced catalytic performance such as sulfur is small, and it is not necessary to estimate the amount of the substance having reduced catalytic performance attached to the catalyst. Therefore, the catalyst can be automatically activated and regenerated with a simple device configuration without increasing the cost. Furthermore, since the regeneration is performed by activating the catalyst at the time of starting, regeneration of the catalyst is not required during traveling, and it is not necessary to enrich or stoichiometric the air-fuel ratio for regeneration of the catalyst during traveling. It is possible to regenerate the catalyst without deteriorating. In the catalyst temperature raising means, the exhaust gas purifying catalyst is used.
When the temperature of the medium rises, fuel is supplied to the exhaust passage or upstream of the catalyst.
By burning the supplied fuel.
Therefore, it is necessary to install a heating means such as an electric heater in the exhaust system.
And simplifying the equipment configuration and reducing equipment costs
Said that the regeneration of the catalyst can be realized appropriately as described above.
The effect will be obtained.

According to the exhaust gas purifying apparatus for an engine of the present invention , the warm-up operation is performed immediately after the engine is started.
Additional fuel in addition to the
The temperature of the catalyst is raised by the
Enrich or stoichiometric air-fuel ratio according to temperature condition
To promote the regeneration of the catalyst.
It can be performed easily and reliably.

According to the third aspect of the present invention, when the catalyst temperature at the start of the engine is equal to or lower than the first predetermined temperature, the catalyst temperature is lower than the first predetermined temperature. Until the high second predetermined temperature is reached, the fuel is further increased by a certain amount by adding to the increase in the fuel for warm-up. Therefore, the supply of the fuel for raising the temperature of the catalyst into the exhaust passage or upstream of the catalyst is appropriately performed. As a result, the temperature of the catalyst can be raised quickly and appropriately.

According to the fourth aspect of the present invention, when the catalyst temperature at the time of starting the engine is equal to or higher than the first predetermined temperature, the warm-up fuel supply control means controls the warm-up by the warm-up fuel supply control means. Immediately after the end of the fuel supply control, the fuel is increased so that the air-fuel ratio becomes rich or stoichiometric until the catalyst temperature reaches a second predetermined temperature higher than the first predetermined temperature. By appropriately supplying the fuel for raising the temperature of the catalyst to the upstream side of the catalyst, the temperature of the catalyst can be raised quickly and appropriately.

According to a fifth aspect of the present invention, in the exhaust gas purifying apparatus for an engine according to the first aspect of the present invention, the secondary air is introduced into the exhaust passage so that the secondary air is not exhausted in the exhaust passage or upstream of the catalyst. Since the temperature of the catalyst is raised by promoting the combustion of the fuel, there is no need to install a heating means such as an electric heater in the exhaust system. Playback can be realized.

According to the exhaust gas purifying apparatus for an engine of the present invention, the lean NOx catalyst is regenerated every time the engine is started. A small number of states can be maintained, and the catalyst performance can be ensured without changing the hardware configuration of the device and therefore increasing the cost by only partially changing the content of the fuel supply control. become.

According to the exhaust gas purifying apparatus for an engine of the present invention, immediately after starting, the engine is warmed up and the temperature of the exhaust gas purifying catalyst is increased and supplied to the exhaust passage or upstream of the catalyst. Since the supply of fuel to the heated catalyst by increasing the amount of fuel to be performed is performed, regeneration by activation of the catalyst can be realized at every start. As a result, the catalyst is always kept in a state where the amount of the catalyst performance-reducing substance such as sulfur is small, and it is not necessary to estimate the amount of the catalyst performance-lowering substance attached to the catalyst. Therefore, the catalyst can be automatically activated and regenerated with a simple device configuration without increasing the cost. Moreover, because the playback of the catalyst during startup, the catalyst regeneration is not required during traveling, that enriching or stoichiometric the air-fuel ratio for the regeneration of the catalyst it is also not required during driving, thereby deteriorating the fuel consumption The regeneration of the catalyst can be performed while preventing the occurrence of such a problem. In addition to this, the previous lean NOx
Based on the engine OPERATION time after catalyst regeneration, since setting the time of the lean NOx catalyst regeneration time, there is just enough properly perform benefit the regeneration of the catalyst at the start. An exhaust gas purifying apparatus for an engine according to the present invention according to claim 8.
According to the setting, when the previous lean NOx catalyst regeneration time was set
Time is not enough for the actual playback
If this occurs, this shortage time and the previous lean NOx catalyst
Based on the operating time of the engine after birth,
Since the NOx catalyst regeneration time is set,
The advantage is that the regeneration of the catalyst
is there.

According to the exhaust gas purifying apparatus for an engine according to the ninth aspect of the present invention, at the time of catalyst regeneration, the air-fuel ratio of the cylinder of one bank is made rich or stoichiometric, and the air-fuel ratio of the other bank is reduced. Since the control is performed so as to make the fuel ratio lean, unburned substances are generated in the exhaust gas from the cylinder of one bank, and the unburned substances reduce the sulfur released from the lean NOx catalyst. Processed
The lean NOx catalyst is regenerated. Also, at this time,
By the lean operation of the other bank, the fuel consumption of the whole engine is suppressed, and there is an advantage that the lean NOx catalyst can be regenerated while suppressing the fuel consumption of the whole engine.

According to the exhaust gas purifying apparatus for an engine of the present invention, immediately after the engine is warmed up, the characteristics of the direct injection engine are changed to inject fuel into the combustion chamber in the exhaust stroke. Therefore, fuel can be supplied to the catalyst, and there is an advantage that the exhaust gas purifying catalyst can be regenerated without hindering normal combustion of the engine. According to the exhaust gas purifying apparatus for an engine of the present invention, the temperature of the catalyst is raised by the catalyst temperature raising means immediately after the start of the engine, and thereafter the fuel supplied to the exhaust passage or to the upstream side of the catalyst is provided. To promote the regeneration of the catalyst, the regeneration of the catalyst can be performed easily and reliably. Claim 12
According to the exhaust gas purifying apparatus for an engine of the present invention described above,
If the coolant temperature of the engine is relatively low (below the first predetermined temperature) immediately after the start of the engine, it is added to the fuel increase for warm-up until the temperature reaches the second predetermined temperature higher than the first predetermined temperature. As described above, the fuel amount is further increased by a certain amount, so that the temperature of the lean NOx catalyst surely rises and the lean NOx catalyst increases.
x Catalyst regeneration is promoted. Therefore, the catalyst is always kept in a state where the amount of the catalyst performance-reducing substance such as sulfur is small, and it is not necessary to estimate the amount of the catalyst performance-lowering substance attached to the catalyst. Therefore, the catalyst can be automatically activated and regenerated with a simple device configuration without increasing the cost. Furthermore, since the regeneration is performed by activating the catalyst at the time of starting, regeneration of the catalyst is not required during traveling, and it is not necessary to enrich or stoichiometric the air-fuel ratio for regeneration of the catalyst during traveling. It is possible to regenerate the catalyst without deteriorating. Then, the temperature rise of the exhaust gas purifying catalyst is performed by supplying fuel in the exhaust passage or upstream of the catalyst,
Since this is done by burning the supplied fuel,
There is no need to provide a heating means such as an electric heater in the exhaust system, and the effect that the above-described appropriate regeneration of the catalyst can be achieved while simplifying the device configuration and reducing the device cost can be obtained. Further, according to the exhaust gas purification device for an engine of the present invention of claim 12 wherein a relatively high coolant temperature of the engine immediately after the start of the engine (the first
If the temperature is equal to or higher than the predetermined temperature, the period of the fuel increase for warming-up is shortened. Therefore, the total amount of additional fuel increasing by adding a certain amount of fuel increasing in addition to the fuel increasing for warm-up is not sufficient. Immediately after this (after the end of the fuel increase for warm-up), the air-fuel ratio becomes rich or stoichiometric until the coolant temperature reaches the second predetermined temperature higher than the first predetermined temperature. To increase the fuel
The temperature of the lean NOx catalyst surely rises, the regeneration of the lean NOx catalyst is promoted, and the same effect as described above (claim 12) can be obtained. According to the exhaust gas purifying device for an engine of the present invention according to claim 13, when the cooling water temperature at the start of the engine is below a first predetermined temperature, immediately after the end of warm-up for fuel increase, the cooling water The lean NOx catalyst is heated by increasing the fuel so that the air-fuel ratio becomes rich or stoichiometric until the temperature reaches a second predetermined temperature higher than the first predetermined temperature. In addition, the enrichment or stoichiometry of the air-fuel ratio can be quickly and reliably and appropriately performed, and the regeneration of the lean NOx catalyst is promoted. Therefore, the catalyst is always kept in a state where the amount of the catalyst performance-reducing substance such as sulfur is small, and it is not necessary to estimate the amount of the catalyst performance-lowering substance attached to the catalyst. Therefore, the catalyst can be automatically activated and regenerated with a simple device configuration without increasing the cost. Furthermore, since the regeneration is performed by activating the catalyst at the time of starting, regeneration of the catalyst is not required during traveling, and it is not necessary to enrich or air-fuel ratio for regeneration of the catalyst during traveling, thereby reducing fuel consumption. It is possible to regenerate the catalyst without deteriorating. Since the temperature of the exhaust gas purifying catalyst is increased by increasing the amount of fuel and burning the increased amount of fuel, there is no need to install a heating means such as an electric heater in the exhaust system, and the device configuration is simplified. Thus, it is possible to obtain the effect that the catalyst regeneration can be appropriately performed as described above while reducing the apparatus cost.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a main configuration of an exhaust gas purifying apparatus for an engine as a first embodiment of the present invention.

FIG. 2 is a control block diagram of the engine in the exhaust gas purifying apparatus for an engine as the first embodiment of the present invention.

FIG. 3 is an overall configuration diagram of an engine system in an exhaust gas purifying apparatus for an engine as a first embodiment of the present invention.

FIG. 4 is a hardware block diagram showing a control system of an engine system in the exhaust gas purifying apparatus for an engine according to the first embodiment of the present invention.

FIG. 5 is a diagram showing an increase characteristic of a fuel injection amount immediately after starting in an exhaust gas purifying apparatus for an engine as a first embodiment of the present invention.

FIG. 6 is a diagram showing an increase characteristic of a fuel injection amount immediately after starting in the exhaust gas purifying apparatus for the engine as the first embodiment of the present invention.

FIG. 7 is a diagram illustrating the setting of the regeneration operation time in the exhaust gas purification device for an engine as the first embodiment of the present invention.

FIG. 8 is a flowchart illustrating the operation of the exhaust gas purifying apparatus for an engine as the first embodiment of the present invention.

FIG. 9 is a flowchart illustrating the operation of the exhaust gas purifying apparatus for an engine as the first embodiment of the present invention.

FIG. 10 is a flowchart illustrating the operation of the engine exhaust gas purification device as the first embodiment of the present invention.

FIG. 11 is an overall configuration diagram of an engine system in an exhaust gas purification device for an engine according to a second embodiment of the present invention.

FIG. 12 is a block diagram schematically showing a configuration of a main part of an exhaust gas purifying apparatus for an engine according to a second embodiment of the present invention.

FIG. 13 is a flowchart illustrating an operation of the exhaust gas purifying apparatus for an engine according to the second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Combustion chamber 2 Intake passage 2a Surge tank 3 Exhaust passage 4 Intake valve 5 Exhaust valve 6 Air cleaner 7 Throttle valve 8 Injector (fuel injection valve) 8a Injector solenoid 8b Injector solenoid transistor 9 Exhaust gas purifying catalytic converter 9A Lean NOx catalyst 9B Three Source catalyst 11 Air flow sensor 12 Intake air temperature sensor 13 Atmospheric pressure sensor 14 Throttle sensor 15 Idle switch 17 Oxygen concentration sensor 19 Water temperature sensor (Catalyst temperature detecting means) 20 Cranking switch (Engine start detecting means) 21 Crank angle sensor 22 TDC sensor ( Cylinder discrimination sensor) 23 Electronic control unit (ECU) 24 Accelerator position sensor 25 Battery sensor 27 CPU 29 Input interface 31 ROM 32 RAM 34 Dora Bar (fuel injection valve driving means) 35 Spark plug 46 Microcomputer port 47 External register (flip-flop) for cylinder discrimination 48 Free running counter 49-52 Register 53-56 Comparator 57-60 RS flip-flop 70 Internal combustion engine (engine) 81) Air pump 82 Air control valve 83 Solenoid 84 Control unit 85 Secondary air backflow prevention check valve 100 Start catalyst regeneration control means 101 Fuel supply control means 102 Start control means 103 Normal operation control means 104 Warm-up fuel supply Control means ( first fuel supply control means
Stage, warm-up operation control means) 105 Catalyst temperature fuel supply control means (second fuel supply control means) as catalyst temperature rise means 106 Catalyst regeneration enrichment means as start-time catalyst regeneration control means 107 Regeneration time setting Means 107A Correction means 108 Catalyst regeneration indication lamp 115 Secondary air introduction control means (secondary air supply means for catalyst temperature increase) as catalyst temperature increase means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02D 41/04 330 F02D 41/04 330M 41/06 330 41/06 330B (56) References JP-A-8-82213 (JP, A) JP-A-4-183922 (JP, A) JP-A-7-63047 (JP, A) JP-A-8-61052 (JP, A) JP-A-8-296485 (JP, A) JP-A-8 JP-A-303290 (JP, A) JP-A-7-139340 (JP, A) Japanese Patent 2,658,575 (JP, B2) Japanese Patent 2,598,585 (JP, B2) Japanese Patent 2,658,575 (JP, B2) WO 96/22457 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F01N 3/08-3/38 F01N 9/00-11/00 F02D 41/00-41/40

Claims (13)

(57) [Claims] 1. An exhaust gas purifying catalyst disposed in an exhaust passage of an engine, an engine start detecting means for detecting start of the engine, and supplying fuel to the exhaust passage or upstream of the catalyst. Catalyst temperature raising means for raising the temperature of the exhaust gas purifying catalyst; and operating the catalyst temperature raising means immediately after starting the engine and enriching the air / fuel ratio based on the detection information from the engine start detection means. wherein the <br/> and a start catalyst regeneration control means for regeneration of the catalyst by the exhaust gas purification device for an engine. 2. A catalyst temperature detecting means for detecting a temperature of the catalyst, and a fuel increase to a combustion chamber of the engine for warm-up operation immediately after the start of the engine based on detection information from the engine start detecting means. Fuel supply control means for controlling the temperature of the catalyst, and the catalyst temperature raising means controls the fuel supply control means to further increase the fuel amount in addition to the fuel increase amount for the warm-up operation immediately after the start of the engine. Thereby, the fuel is supplied to the inside of the exhaust passage or the upstream side of the catalyst to burn the fuel, and the catalyst regeneration control means at the time of starting is based on the detection information from the catalyst temperature detecting means and the engine start detecting means. After the start of the engine, the air-fuel ratio is made rich or stoichiometric by fuel supply through the fuel supply control means into the exhaust passage or upstream of the catalyst. The exhaust gas purifying apparatus for an engine according to claim 1, characterized in that: 3. The method according to claim 2, wherein the catalyst temperature raising means is configured to detect the temperature of the catalyst at the time of starting the engine at a first temperature or lower based on detection information from the catalyst temperature detecting means and the engine start detecting means. In this configuration, the fuel is added to the warm-up fuel increase until the temperature of the catalyst reaches a second predetermined temperature higher than the first predetermined temperature, so that a further constant fuel increase is performed. 3. The method according to claim 2, wherein
An exhaust gas purifying apparatus for an engine as described in the above. 4. The method according to claim 1, wherein the catalyst temperature raising means is configured to detect the temperature of the catalyst at the time of starting the engine at a first predetermined temperature or higher based on detection information from the catalyst temperature detecting means and the engine start detecting means. End of the warm-up fuel supply control
Thereafter , the fuel is increased so that the air-fuel ratio becomes rich or stoichiometric until the temperature of the catalyst reaches a second predetermined temperature higher than the first predetermined temperature. The exhaust gas purifying apparatus for an engine according to claim 2 or 3, 5. The exhaust gas purifying catalyst, wherein the catalyst temperature raising means introduces secondary air into the exhaust passage to promote the combustion of unburned fuel in the exhaust passage or upstream of the catalyst. The exhaust gas purifying apparatus for an engine according to claim 1, further comprising a catalyst temperature increasing secondary air supply means for increasing the temperature of the exhaust gas. 6. The exhaust gas purifying catalyst is configured as an exhaust gas purifying lean NOx catalyst, based on catalyst temperature detecting means for detecting the temperature of the lean NOx catalyst, and detection information from the engine start detecting means. A catalyst temperature raising unit that raises the temperature of the lean NOx catalyst to a predetermined temperature or higher immediately after the start of the engine; and, based on detection information from the catalyst temperature detection unit, the temperature of the lean NOx catalyst reaches the predetermined temperature. characterized in that it includes a start catalyst regeneration control means for playback of said lean NOx catalyst when it reaches the exhaust gas purifying apparatus according to claim 1, wherein the engine. 7. An exhaust gas purifying lean NOx catalyst disposed in an exhaust passage of an engine, engine start detecting means for detecting start of the engine, and catalyst temperature detecting means for detecting a temperature of the lean NOx catalyst. A catalyst temperature raising means for raising the temperature of the lean NOx catalyst to a predetermined temperature or higher immediately after the start of the engine based on detection information from the engine start detection means; a fuel supply means capable of supplying fuel to the upstream side, based on the detection information from the catalyst temperature detecting means, start catalyst temperature of the lean NOx catalyst is play the lean NOx catalyst upon reaching the predetermined temperature Regeneration control means; and regeneration time setting means for setting a regeneration time of the lean NOx catalyst by the start-time catalyst regeneration control means. Based on the engine OPERATION time after the last of the lean NOx catalyst regeneration with perturbed catalyst regeneration control means, characterized in that it is configured to set the current of the lean NOx catalyst regeneration time of the engine Exhaust gas purification device. 8. The reproduction time setting means according to claim 1, wherein
If the execution time of performing the actual reproduction the set time of the Ox catalyst regeneration time is insufficient, on the basis of the said engine OPERATION time after this lack of time and the previous lean NOx catalyst regeneration 8. The exhaust gas purifying apparatus for an engine according to claim 7, wherein the present lean NOx catalyst regeneration time is set. 9. The V-type engine having two left and right banks, wherein the starting catalyst regeneration control means enriches or stoichiometrics the air-fuel ratio to the cylinders of one bank to cause the other bank to recharge. Characterized by being constituted by fuel supply control means for performing control so as to make the air-fuel ratio to the cylinder lean.
An exhaust gas purifying apparatus for an engine according to claim 6. 10. An in-cylinder injection engine in which the engine directly injects fuel into a combustion chamber, wherein the starting catalyst regeneration control means injects fuel into the combustion chamber during an exhaust stroke to supply fuel. 7. The exhaust gas purifying apparatus for an engine according to claim 6, further comprising fuel supply control means for enriching or stoichiometric air-fuel ratio. 11. The start-time catalyst regeneration control means activates the catalyst temperature raising means immediately after the start of the engine, based on the detection information from the engine start detection means, and thereafter activates an idle state.
The exhaust gas purifying apparatus for an engine according to claim 1, wherein the catalyst is regenerated by making the fuel ratio rich or stoichiometric . 12. An exhaust gas purifying lean NOx catalyst disposed in an exhaust passage of the engine, engine start detecting means for detecting the start of the engine, and a coolant temperature for detecting a coolant temperature of the engine. Detecting means, based on detection information from the engine start detecting means, for performing fuel increase control to a combustion chamber of the engine for warm-up operation immediately after the start of the engine; When the coolant temperature of the engine at the time of starting the engine is equal to or lower than a first predetermined temperature based on the detection information from the engine start detection means, the coolant temperature is higher than the first predetermined temperature. until it reaches the second predetermined temperature was raised to the lean NOx catalyst by performing a further quantity of fuel increase as added to the fuel increase for air 該暖, the engine At the time of start-up
The cooling water temperature of the engine at the first predetermined temperature or lower.
In the case above, add it to the fuel increase for warm air
Immediately after a certain amount of fuel increase, the cooling water temperature
The temperature reaches a second predetermined temperature higher than the first predetermined temperature
Until the air-fuel ratio becomes rich or stoichiometric.
Increase the temperature of the lean NOx catalyst by increasing the charge
An exhaust gas purifying apparatus for an engine, comprising: a fuel supply control means for causing the exhaust gas to be purified. 13. An engine disposed in an exhaust passage of the engine.
Lean NOx catalyst for purifying exhaust gas, engine start detecting means for detecting start of the engine, and cooling water temperature detecting means for detecting the temperature of cooling water of the engine
If, on the basis of the detection information from the engine start detection means, said
Immediately after the start of the engine, the engine
First fuel supply control means for controlling an increase in fuel to the firing chamber
From the cooling water temperature detecting means and the engine start detecting means.
At the time of starting the engine based on the detection information of
When the engine coolant temperature is below the first predetermined temperature
Is the end of the warm-up fuel increase by the first fuel supply control means.
Immediately after the cooling water temperature is higher than the first predetermined temperature.
Until the second predetermined temperature is reached, the air-fuel ratio is rich or
By increasing the fuel so that it becomes a toy kio,
Second fuel supply control means for raising the temperature of the lean NOx catalyst;
Engine exhaust gas characterized by having
Purification device.