JP2003148197A - Exhaust emission control device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely control the exhaust gas flowing into an HC adsorbing catalyst to the reduction side while HC is desorbed from the HC adsorbing catalyst. SOLUTION: The exhaust emission control device comprises a three-way catalyst 25 including an oxygen absorbing material, disposed on the upstream side of the HC adsorbing catalyst 27, and a desorption determining means 42 for determining whether the operation condition is switched to the desorption operation condition in which the quantity of HC desorbed from the HC adsorbing material of the HC adsorbing catalyst 27 exceeds the quantity of HC adsorbed in the HC adsorbing material. When it is determined that the engine is in the desorption operation condition by the desorption determining means 42, the oxygen emission control is executed for controlling the exhaust gas on the upstream side of the HC adsorbing catalyst 27 to the reduction side so that oxygen is emitted from the oxygen absorbing material. Before the operation is switched to the oxygen emission control, the initial control is executed for reducing the quantity of oxygen absorbed in the oxygen absorbing material of the three-way catalyst 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust purification system for an engine having an upstream catalyst and an HC adsorption catalyst in an exhaust passage, and more particularly to a measure for optimizing the degree of reduction of exhaust gas flowing into the HC adsorption catalyst. It is related.

[0002]

2. Description of the Related Art Conventionally, there has been known an engine exhaust purification system in which an upstream catalyst and an HC adsorption catalyst are arranged in an exhaust passage to adjust the amount of oxygen flowing into the HC adsorption catalyst. This upstream catalyst is composed of a three-way catalyst containing an oxygen storage substance and is arranged close to the engine, and is activated earlier after the engine is started. The above HC adsorption catalyst is generally H
It contains a C adsorbent, an oxygen storage material, and a catalytic metal.
The HC adsorbent has a property of adsorbing HC (hydrocarbon) in exhaust gas at a low temperature such as cold start of an engine, and desorbing the adsorbed HC along with a temperature rise of the HC adsorbent. ing. The oxygen storage substance has a property of storing oxygen on the oxidation side (lean side) and releasing oxygen on the reduction side (rich side), such as cerium oxide. The catalytic metal is activated when the temperature exceeds a predetermined temperature, and H in the exhaust gas
It has a characteristic of decomposing C, CO and NOx to purify exhaust gas.

When the engine is started, the upstream catalyst is activated early, while the HC adsorbing catalyst initially only adsorbs HC to the HC adsorbing material and adsorbs H.
C is not detached. Then, when the temperature of the HC adsorbent rises and reaches a predetermined temperature, desorption of the adsorbed HC is started. Immediately after the start of the desorption of HC, the catalyst metal is still in an unactivated state, and therefore, as disclosed in, for example, JP-A-10-61426 and JP-A-11-82111, the A technique is known in which the exhaust gas in the HC adsorption catalyst is made into an oxygen rich state by controlling the fuel ratio to the lean side, and the oxygen in the exhaust gas is used to decompose HC. On the other hand, by controlling the air-fuel ratio to the rich side during desorption of HC, the exhaust gas in the HC adsorption catalyst is controlled to the rich side to release oxygen from the oxygen storage material, and the released oxygen causes the above HC adsorption. It has been proposed to decompose the HC desorbed from the material.

[0004]

However, in the conventionally proposed control, the air-fuel ratio is controlled to the rich side during the desorption of HC adsorbed on the HC adsorbent,
At this time, oxygen is also released from the oxygen storage substance of the upstream catalyst, and this oxygen flows into the HC adsorption catalyst. Therefore, it is difficult to accurately control the exhaust gas flowing into the HC adsorption catalyst to the reduction side. There was a problem.

The present invention has been made in view of the above points, and an object of the present invention is to obtain H from an HC adsorption catalyst.
The purpose is to control the exhaust gas flowing into the HC adsorption catalyst during desorption of C to the reduction side with high accuracy.

[0006]

In order to achieve the above object, the present invention is designed to release oxygen stored in an oxygen storage material contained in an upstream catalyst before the start of desorption operation. It is a thing.

Specifically, the first solution means is an HC adsorbent which is disposed in the exhaust passage of the engine and adsorbs HC while desorbing the adsorbed HC as the temperature rises, and oxygen on the oxidizing side. The amount of HC desorbed from the HC adsorbent, which contains an oxygen storage substance that occludes and releases oxygen on the reducing side, and a catalyst metal that oxidizes HC desorbed from the HC adsorbent, Oxygen is released from the oxygen storage substance when the determination means determines whether or not the desorption operation state has exceeded the amount adsorbed to the HC adsorbent, and when the determination means determines the desorption operation state. As described above, the reduction degree control means for controlling the exhaust gas on the upstream side of the HC adsorption catalyst or in the HC adsorption catalyst to the reduction side and the exhaust passage on the upstream side of the HC adsorption catalyst are arranged to store oxygen on the oxidation side. , Oxygen storage that releases oxygen on the reducing side An upstream catalyst containing, and a stored oxygen amount reduction means for reducing the amount of oxygen stored in the oxygen storage substance of the upstream catalyst before it is determined by the determination means that the state has transitioned to the desorption operation state. Is equipped with.

The second solving means is the same as the first solving means, wherein the stored oxygen amount reducing means is upstream in a predetermined period immediately before the transition time to the desorption operation state judged by the judging means. It is configured to reduce the oxygen concentration in the exhaust gas upstream of the catalyst or inside the upstream catalyst to 0.1% or less.

A third solving means is the above-mentioned first or second solving means, wherein the reduction degree control means sets a reference value of the degree of reduction of the exhaust gas upstream of the HC adsorption catalyst or in the HC adsorption catalyst. The stored oxygen amount reducing means controls the reduction degree of the exhaust gas upstream of the upstream catalyst or inside the upstream catalyst so that the reduction degree becomes a target value that is set to a value larger than the reference value. Is configured.

A fourth solving means is the above-mentioned first solving means, wherein the reduction degree controlling means is arranged so that the oxygen concentration of the exhaust gas on the upstream side of the HC adsorption catalyst or in the HC adsorption catalyst becomes a predetermined value or less. It is configured to control the air-fuel ratio of the engine.

The fifth solving means is the above-mentioned fourth solving means, wherein the control of the air-fuel ratio by the reduction degree controlling means is
One-sided weighted feedback control that sets the correction value of the feedback value toward the reduction side to be larger than the correction value of the oxidation side, or one-sided feedback that corrects the feedback value toward the reduction side when the exhaust gas is on the oxidation side from the reference It is done by control.

That is, in the first solving means, the judging means judges whether or not the desorption operation state in which the amount of HC desorbed from the HC adsorbent exceeds the amount adsorbed to the HC adsorbent has been entered. Before it is determined that the HC adsorption catalyst has transitioned to the desorption operation state, the stored oxygen amount reduction means reduces the amount of oxygen stored in the oxygen storage substance of the upstream catalyst. When the determination means determines that the desorption operation state has been entered, the reduction degree control means controls the exhaust gas upstream of the HC adsorption catalyst or in the HC adsorption catalyst to the reduction side (rich side).
At this time, since the amount of oxygen stored in the oxygen storage material of the upstream catalyst is reduced, even if the exhaust gas controlled to the reduction side flows into the upstream catalyst, most of the oxygen is released from this oxygen storage material. Not done. Therefore, the exhaust gas, which is controlled to the reduction side with high accuracy, flows into the HC adsorption catalyst arranged on the downstream side of the upstream catalyst.
The amount of oxygen released from the oxygen storage substance of the C adsorption catalyst can be accurately controlled, and the treatment of HC using this oxygen can be performed efficiently.

That is, when the exhaust gas controlled to the reduction side flows into the upstream catalyst in the desorption operation state, for example, when the upstream catalyst is not yet activated, oxygen is removed from the oxygen storage substance of the upstream catalyst. Even if is released, this released oxygen will flow out from the upstream catalyst because it does not react with HC in the exhaust gas. Therefore, by reducing the amount of oxygen stored in the oxygen storage substance of the upstream catalyst before shifting to the desorption operation state, excess oxygen flows into the HC adsorption catalyst when shifting to the desorption operation state. Are prevented. As a result, the exhaust gas whose degree of reduction is accurately controlled can be made to flow into the HC adsorption catalyst.

On the other hand, for example, when the upstream catalyst is already activated, if oxygen is stored in the oxygen storage substance of the upstream catalyst, this oxygen is released and reacts with HC in the exhaust gas, so Exhaust gas HC flowing out of the catalyst
It becomes difficult to control the concentration with high accuracy. Therefore, by reducing the amount of oxygen stored in the oxygen storage substance of the upstream catalyst before shifting to the desorption operation state, the HC in the exhaust gas in the upstream catalyst hardly reacts with the released oxygen, Since it flows out from the catalyst, the amount of HC flowing into the HC adsorption catalyst can be accurately controlled.

In the second solving means, the first means is used.
In the means for solving the above problem, the stored oxygen amount reducing means controls the amount of oxygen in the exhaust gas upstream of the upstream catalyst or inside the upstream catalyst within a predetermined period immediately before it is determined by the determination means that the HC adsorption catalyst has transitioned to the desorption operation state. The oxygen concentration is reduced to 0.1% or less. That is, by reducing the oxygen concentration in the exhaust gas upstream of the upstream catalyst or inside the upstream catalyst to 0.1% or less, oxygen is released from the oxygen storage substance of the upstream catalyst, so that the desorption operation state is set. Before the transition, the oxygen storage capacity of the oxygen storage material of the upstream catalyst can be promptly and surely reduced. Further, by limiting the control of the exhaust gas upstream of the upstream catalyst or inside the upstream catalyst to the reduction side within a predetermined period, the exhaust gas is controlled to the reduction side for a period longer than necessary. To prevent.

Further, in the third solving means, the first
Alternatively, in the second solving means, the target value of the degree of reduction of exhaust gas upstream of the upstream catalyst or inside the upstream catalyst is HC
Since the reduction degree is set to a value higher than the reference value of the degree of reduction of the exhaust gas on the upstream side of the adsorption catalyst or in the HC adsorption catalyst, oxygen is immediately released from the oxygen storage substance of the upstream catalyst, and the stored oxygen The period during which the oxygen concentration in the exhaust gas is reduced by the amount reducing means can be shortened.

In the fourth solving means, the first
When the determination means determines that the HC adsorption catalyst has transitioned to the desorption operation state, the reduction degree control means determines that the oxygen concentration of the exhaust gas upstream of the HC adsorption catalyst or in the HC adsorption catalyst is predetermined. The air-fuel ratio of the engine is controlled so that it is below the specified value. In other words, in order to reduce the amount of oxygen stored in the oxygen storage substance of the upstream catalyst before shifting to the desorption operation state, in order to reduce the amount of oxygen stored in the oxygen storage substance of the upstream catalyst, after the transition to the desorption operation state, the upstream side of the HC adsorption catalyst or When the exhaust gas in is controlled to the reduction side, oxygen is hardly released from the upstream catalyst, and the feedback of the air-fuel ratio control, which takes a long time to respond, can be avoided as much as possible. As a result, the exhaust gas can be controlled to the reducing side with high accuracy immediately after the shift to the desorption operation state.

In the fifth solving means, the fourth means
In the means for solving the above, in the control of the air-fuel ratio by the reduction degree control means, biased feedback control or one-sided feedback control is performed. That is, when in the desorption operation state, the weighted feedback control that sets the correction value of the feedback value in the reduction side direction to be larger than the correction value in the oxidation side direction, or the reduction of the feedback value when the exhaust gas is on the oxidation side of the reference value Since the air-fuel ratio control of the engine is performed by the one-sided feedback control that corrects in the lateral direction, the HC
The exhaust gas upstream of the adsorption catalyst or in the HC adsorption catalyst can be reliably controlled to the reduction side.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

An engine exhaust gas purification apparatus according to an embodiment of the present invention purifies exhaust gas from a gasoline engine of a cylinder injection type engine. In the above gasoline engine, a plurality of cylinders 2 and a piston 3 reciprocatingly fitted in each cylinder 2 are provided in an engine body 1, and a combustion chamber 4 is provided above the cylinder 2 by the piston 3. It is compartmentalized. A spark plug 6 connected to an ignition circuit 5 is mounted in the combustion chamber 4 at a predetermined position above the combustion chamber 4 as desired.

In the periphery of the combustion chamber 4, the combustion chamber 4
An injector 7 as a fuel supply means for directly injecting fuel is installed therein. A fuel supply circuit having a high-pressure fuel pump, a pressure regulator and the like (not shown) is connected to the injector 7, and the fuel from the fuel tank is adjusted to an appropriate pressure by the fuel supply circuit and supplied to the injector 7. It has become.
Further, the fuel supply circuit is provided with a fuel pressure sensor 8 for detecting the fuel pressure.

The combustion chamber 4 communicates with an intake passage 10 via an intake port provided with an intake valve 9. An air cleaner 11 for filtering intake air, an air flow sensor 12 for detecting an intake air amount, an electric throttle valve 13 for narrowing the intake passage 10, and a surge tank 14 are arranged in this intake passage 10 in this order from the upstream side. It is set up. The electric throttle valve 13 is opened and closed by being driven by a motor 15 without interlocking with an accelerator pedal (not shown). Further, the electric throttle valve 13
A throttle opening sensor 16 for detecting the valve opening of the surge tank 14 is provided at the installation portion of the above, and an intake pressure sensor 17 for detecting the intake pressure is provided at the installation portion of the surge tank 14.

The intake passage 10 on the downstream side of the surge tank 14 is an independent passage branched for each cylinder 2. The downstream end of each independent passage branches into two and communicates with the intake port. A swirl valve 18 is provided on one side thereof. When the swirl valve 18 is driven by the actuator 19 to be in the closed state, intake air is supplied into the combustion chamber 4 only from the other branch passage, so that a strong intake swirl is generated in the combustion chamber 4. ing.
This intake swirl will be weakened as the swirl valve 18 opens. A swirl valve opening sensor 20 that detects the opening of the swirl valve 18 is provided at the installation portion of the swirl valve 18. Instead of the swirl valve 18, a tumble valve for generating a tumble flow may be installed.

The combustion chamber 4 communicates with an exhaust passage 22 through an exhaust port provided with an exhaust valve 21, and the upstream end of the exhaust passage 22 is branched for each cylinder 2. In the exhaust passage 22, a first oxygen concentration sensor 24 for detecting the oxygen concentration in the exhaust gas, HC (hydrocarbon), CO (carbon monoxide), and NOx in the exhaust gas are arranged in this order from the upstream side.
A three-way catalyst 25 as an upstream catalyst having a function of purifying all (nitrogen oxides), a second oxygen concentration sensor 26 for detecting the oxygen concentration in exhaust gas on the downstream side of the three-way catalyst 25, and exhaust gas HC that adsorbs and purifies HC in gas
An adsorption catalyst 27 and a third oxygen concentration sensor 28 that detects the oxygen concentration in the exhaust gas on the downstream side are arranged.

The first to third oxygen concentration sensors 24 and 2
Reference numerals 6 and 28 detect the degree of reduction of the exhaust gas as an exhaust air-fuel ratio obtained based on the oxygen concentration, and its output is largely inverted (changed) between the lean side and the rich side with the stoichiometric air-fuel ratio as the boundary. Λ sensor, which provides excellent detection accuracy in the vicinity of the stoichiometric air-fuel ratio. Based on the detection values of the oxygen concentration sensors 26 and 28, H corresponding to the component concentration of the reducing agent component such as HC or CO that affects the release of oxygen from the oxygen storage substance described later.
The degree of reduction of the exhaust gas on the upstream side or the downstream side of the C adsorption catalyst 27 is estimated. The first to third oxygen concentration sensors 24, 26, 28 may be configured by linear oxygen sensors whose output changes linearly according to the air-fuel ratio, instead of the λ sensor.

The exhaust air-fuel ratio is an expression method that represents the air-fuel ratio of the mixture of fuel and air that corresponds directly to the exhaust gas state from the existing state of the oxygen concentration and reducing agent concentration of the exhaust gas. When the fuel ratio is 14.7, it corresponds to the theoretical air-fuel ratio, and the oxygen concentration at this time is substantially 0 to 0.5%. When the exhaust air-fuel ratio is 14.7 or less with this as a boundary, the oxygen concentration decreases or is fixed to zero, and the reducing agent concentration increases. On the other hand, when the exhaust air-fuel ratio is 14.7 or more, the oxygen concentration increases and the reducing agent concentration decreases.

The three-way catalyst 25 has a catalyst metal such as palladium (Pd) or platinum (Pt) supported on alumina or the like and a binder made of zirconium (Zr) or the like, and is heated to a predetermined temperature. By activating, HC and CO in the exhaust gas are oxidized and purified, and NOx in the exhaust gas is reduced and purified. This purifying function is remarkably exhibited near the stoichiometric air-fuel ratio. The three-way catalyst 25 also contains an oxygen storage material such as cerium oxide (CeO2) or a complex oxide of cerium Ce and a rare earth element such as praseodymium Pr. This oxygen storage material stores oxygen when the exhaust gas is on the oxidation side (lean side),
It has a characteristic of releasing the stored oxygen when the exhaust gas is on the reducing side (rich side). The three-way catalyst 25 uses the released oxygen in addition to oxygen in the exhaust gas for oxidizing HC and CO in the exhaust gas.

The HC adsorbing catalyst 27 has a function of adsorbing HC discharged especially during cold start and purifying exhaust gas, and as shown in FIG. 2, a honeycomb structure made of cordierite is used. And a HC adsorbent 27b carried on the wall surface of the through hole formed in the carrier 27a,
It is constituted by a three-way catalyst layer 27c supported by being coated on the surface thereof.

The above-mentioned HC adsorbent 27b is the H gas in the exhaust gas.
A so-called β-type zeolite in which a large number of pores having a pore size suitable for adsorbing and holding C, that is, a pore size of about 7.2 angstrom is formed, is made to impregnate and carry silver (Ag), The HC in the exhaust gas is adsorbed at a low temperature such as during cold start of the
C is eliminated. The silver is supported in order to enhance the HC adsorbing action of β-type zeolite so that the HC can be retained at a higher temperature.

The three-way catalyst layer 27c has a catalytic metal such as palladium (Pd) or platinum (Pt) supported on alumina or the like and a binder made of zirconium (Zr) or the like, and is heated to a predetermined temperature. By activating by
It has a function of oxidizing HC and CO in the exhaust gas and reducing NOx in the exhaust gas to purify it. This purifying function is remarkably exhibited near the stoichiometric air-fuel ratio.

The three-way catalyst layer 27c is heated to a predetermined temperature and activated to generate oxygen in a high oxygen atmosphere in which the oxygen concentration in the exhaust gas is high (for example, an atmosphere having an oxygen concentration of 0.5% or more). An oxygen storage material that has the function of releasing the stored oxygen as the oxygen concentration in the exhaust gas decreases and becomes a low oxygen atmosphere, such as cerium oxide (CeO2) or cerium Ce and praseodymium Pr. It contains an oxygen storage material such as a complex oxide with a rare earth element. In other words, the oxygen storage material has a property of storing oxygen when the surrounding exhaust gas is on the oxidizing side (lean side) and releasing the stored oxygen when the surrounding exhaust gas is on the reducing side (rich side). is doing.

In the three-way catalyst layer 27c, the HC desorbed from the HC adsorbent 27b is oxidized and purified at a relatively low temperature by the oxidizing action using the oxygen released from the oxygen storage material. It has become. The above HC
The adsorption catalyst 27 is composed of the material forming the three-way catalyst layer 27c and H
It may be configured such that the C adsorbent 27b is integrally mixed.

An EGR passage 29 for recirculating a part of the exhaust gas to the intake system is connected to the exhaust passage 22.
The EGR passage 29 has an upstream end connected to the upstream side of the first oxygen concentration sensor 24 in the exhaust passage 22, and a downstream end connected between the throttle valve 13 and the surge tank 14 in the intake passage 10. . EGR passage 29
Includes an EGR valve 3 whose opening degree is electrically adjustable.
0 and a lift sensor 31 that detects the lift amount of the EGR valve 30 are provided. The EGR passage 29, the EGR valve 30, and the lift sensor 31 constitute exhaust gas recirculation means.

In the exhaust passage 22, a part of the intake air is introduced from the intake passage 10 to the HC adsorption catalyst 2 in the exhaust passage 22.
7 is connected to a secondary air supply passage 32 that is sent to the upstream side. The opening and closing of the secondary air supply passage 32 is controlled according to a control signal output from a control unit (ECU) 34 that controls the engine. A flow control valve 33 is provided.

The control unit 34 includes an air flow sensor 12, a throttle opening sensor 16, an intake pressure sensor 17, a swirl valve opening sensor 20, oxygen concentration sensors 24, 26 and 28, and a lift sensor for the EGR passage 29. The output signal from 31 is input. Also,
The control unit 34 includes a water temperature sensor 35 that detects an engine cooling water temperature, an intake air temperature sensor 36 that detects an intake air temperature, and an atmospheric pressure sensor 3 that detects an atmospheric pressure.
7, the detection signals output from the rotation speed sensor 38 that detects the rotation speed of the engine and the accelerator opening sensor 39 that detects the opening (accelerator operation amount) of the accelerator pedal are input.

The control unit 34 includes a desorption determination means 42, a fuel injection control means 40, an ignition timing control means 41, an initial determination means 43, and a correction means 44.

The desorption determining means 42 determines the HC based on the elapsed time and the operation history measured after the engine is started.
By deducing the temperature _THCE of the adsorption catalyst 27 and comparing this temperature _THCE with a preset reference temperature, the desorption amount of HC desorbed from the HC adsorbent 27b is adsorbed by the HC adsorbent 27b. The timing of transition to the desorption operation state in which the amount of adsorbed HC exceeds a certain amount is estimated in advance, and it is determined whether or not the transition to the desorption operation state has occurred.

That is, as shown in FIGS. 3 (a) and 3 (b), after the engine is cold started, only the HC is adsorbed by the HC adsorbent 27b and the HC is not desorbed from the HC adsorbent 27b. Continues, and the temperature _THCE of the HC adsorption catalyst 27 gradually rises with the passage of time. When the amount of adsorbed HC gradually increases and the temperature _THCE of the HC adsorbing catalyst 27 reaches a certain temperature, desorption of HC from the HC adsorbent 27b starts. At this time, adsorption to and desorption from the HC adsorbent 27b are performed in parallel. When the temperature T _HCE of the HC adsorption catalyst 27 further rises, H
The C adsorption catalyst 27 is the HC desorbed from the HC adsorbent 27b.
The desorption operation state is shifted to a desorption operation state in which the desorption amount exceeds the adsorption amount of HC adsorbed on the HC adsorbent 27. The temperature at this time is _{defined as the} desorption operation start temperature _THC2 . Further, the HC adsorption catalyst 2
When the temperature _{THCE of} 7 rises, the HC adsorbent 27b
Is completed. The temperature _THCE at this time is _defined as the desorption operation completion temperature _THC3 . The desorption operation start temperature T _HC2 is, for example, 150 ° C., and the desorption operation completion temperature T _HC3 is, for example, 250 ° C.

That is, the temperature T _HCE of the HC adsorbing catalyst 27 gradually rises with the passage of time, but since the rising speed varies depending on the history after the engine is started, the desorption determining means 42 causes the engine start to start. The temperature T _HCE of the HC adsorption catalyst 27 is derived based on the subsequent history and the transition time T2 at which the temperature T _HCE of the HC adsorption catalyst 27 reaches the desorption operation start temperature T _HC2 is estimated. Then, so as to determine whether the transition to the desorption operation state according to whether the temperature T _HCE of the HC adsorption catalyst 27 has reached the desorption operation start temperature T _HC2.

The desorption determination means 42 is based on the oxygen concentration detected by the third oxygen concentration sensor 28 arranged on the downstream side of the HC adsorption catalyst 27, based on the oxygen concentration from the HC adsorbent 27b. It may be configured to determine whether or not the desorption amount is higher than the adsorption amount in the desorption operation state.

The initial decision means 43 derives an initial control start time T1 which is a predetermined period before the transition timing T2 to the desorption operation state based on the history after the engine is started, and the initial control start time T1. initial operation with estimating the initial control start temperature T _HC1 is the temperature of the HC adsorption catalyst 27, a and less than desorption operation start temperature T _HC2 at a temperature T _HCE initial control start temperature T _HC1 more HC adsorption catalyst 27 at It is configured to determine whether or not the state has been entered. This predetermined period is set to, for example, several seconds.

The fuel injection control means 40 is configured to control the fuel injection state of the fuel injected from the injector 7 according to the operating state of the engine.

In the fuel injection control means 40, the temperature _THCE of the HC adsorption catalyst 27 derived by the desorption determination means 42 is _{equal to} or higher than the initial control start temperature _THC1 and the desorption operation start temperature _THC2.
When it is determined that the temperature is lower than 0 ° C, the degree of reduction O _X1 of the exhaust gas on the upstream side of the three-way catalyst 25 detected by the first oxygen concentration sensor 24 becomes the degree of reduction equivalent to the combustion at the air-fuel ratio of 14.0. Is configured to execute initial control for controlling the fuel injection amount. In the initial control, the three-way catalyst 25
By setting the target value of the degree of reduction O _X1 of the exhaust gas on the upstream side of the three-way catalyst 25 to the degree of reduction equivalent to the combustion at the air-fuel ratio of 14.0, the oxygen concentration in the exhaust gas on the upstream side of the three-way catalyst 25 becomes 0. The reduction side (rich side) of 1% or less is controlled. That is, in the initial control, the exhaust gas is controlled to be on the reducing side, so that the oxygen stored in the oxygen storage substance of the three-way catalyst 25 is released. That is, this initial control constitutes a stored oxygen amount reducing means for reducing the amount of oxygen stored in the oxygen storage substance of the three-way catalyst 25 before the transition time to the desorption operation state.

In the above initial control, the target value of the degree of reduction O _X1 of the exhaust gas on the upstream side of the three-way catalyst 25 is set to a degree of reduction corresponding to combustion at an air-fuel ratio of 13.0 or more and 14.5 or less. Is preferred. If the target value of the degree of reduction O _X1 is set to the degree of reduction equivalent to combustion at an air-fuel ratio of less than 13.0, HC
While a large amount of HC flows into the adsorption catalyst 27, a part of the HC that has flowed into the HC adsorption catalyst 27 is adsorbed on the HC adsorption material 17b because the adsorption capacity of the HC adsorption material 27b has not yet increased in the initial control stage. Without it, it will be leaked. On the other hand, if the target value of the degree of reduction O _X1 is set to the degree of reduction equivalent to the combustion with the value of the air-fuel ratio exceeding 14.5, it means that oxygen is not released quickly from the oxygen storage substance of the three-way catalyst 25. , It becomes impossible to shorten the time of initial control. Therefore, the target value of the reduction degree O _X1 is set to 13.0.
It is preferable to set the degree of reduction equivalent to ˜14.5.

When the HC adsorbing catalyst 27 is in an operating state in which the HC adsorbing catalyst 27 adsorbs and desorbs HC, the fuel injection control means 40 is in the period from the intake stroke to the ignition timing, and in the latter half of the compression stroke or later. The fuel injection is performed in each of the injection and the early injection before this, and the injector 7 is controlled so as to perform the divided injection at least twice. The fuel injection control means 40 may be configured to perform the split injection in the entire operating region during cold operation, and in the high load region, the fuel is injected only in the intake stroke in order to satisfy the engine output requirement. It may be configured to perform injection. Further, it is not always necessary to directly inject the fuel, and the injector 7 may be arranged in the intake port to supply the mixture of intake air and fuel into the combustion chamber 4. Good.

When it is judged that the fuel injection control means 40 is in the desorption operation state, the exhaust gas contacting the HC adsorption catalyst 27 has an oxygen concentration of 0.5 when the initial control is stopped. The oxygen release control is performed so that the fuel injection amount is feedback-controlled so as to be on the reducing side (rich side) of not more than%. In other words, this oxygen release control constitutes the reduction degree control means. In the oxygen release control, the degree of reduction O _X2 of the exhaust gas on the upstream side of the HC adsorption catalyst 27 detected by the second oxygen concentration sensor 26 is controlled to be the degree of reduction equivalent to the combustion at the air-fuel ratio of 14.5. The oxygen concentration of the exhaust gas contacting the HC adsorption catalyst 27 is controlled to 0.5% or less. That is, in the oxygen release control, the degree of reduction of the exhaust gas corresponding to combustion at the air-fuel ratio of 14.5 is set as the reference value O _X20 of the degree of reduction on the upstream side of the HC adsorption catalyst 27.

In the above oxygen release control, the oxygen concentration contained in the exhaust gas is controlled to 0.5% or less because the oxygen concentration contained in the exhaust gas contacting the HC adsorption catalyst 27 is 0%. This is because if controlled to the oxidation side (lean side) exceeding 0.5%, it becomes difficult for oxygen to be released from the oxygen storage substance contained in the HC adsorption catalyst 27. That is, in the oxygen release control, the degree of reduction of the exhaust gas with respect to the oxygen storage substance of the HC adsorption catalyst 27 is controlled.

In the above oxygen release control, the HC adsorption catalyst 27
The degree of reduction O _X2 of the exhaust gas upstream of the air-fuel ratio is 14.
5 is higher than the reference value O _X20 equivalent to combustion, the feedback value Qfb2 of the fuel injection amount is reduced by the correction value β1, and conversely, when the reference value O _X20 equivalent to combustion at the air-fuel ratio of 14.5 or less, By increasing the feedback value Qfb2 of the fuel injection amount by the correction value β2, control is performed so that the degree of reduction on the upstream side of the HC adsorption catalyst 27 becomes the reference value O _X20 . At this time, the correction value β1 is changed to the correction value β2
HC adsorption catalyst 2 by setting the value smaller than
The exhaust gas on the upstream side of 7 can be easily controlled to the reducing side (rich side). That is, the oxygen release control is a one-sided weighted feedback control in which the correction value of the feedback value in the reduction side direction is set to be larger than the correction value in the oxidation side direction.

In the above oxygen release control, it is preferable to control the air-fuel ratio in the combustion chamber 4 of the engine to be not less than 13.5 and not more than 15.0. When the air-fuel ratio is less than 13.5, the exhaust gas in the HC adsorbing catalyst 27 becomes the reducing side to promote the release of oxygen from the oxygen storage material, but the amount of HC discharged from the engine increases too much and the HC adsorbing material increases. Since some HC has been desorbed from 27a, the HC cannot be completely purified. On the other hand, when the air-fuel ratio exceeds 15.0, unreacted oxygen flowing out from the three-way catalyst 25 arranged on the upstream side flows into the HC adsorption catalyst 27, so that the exhaust gas flowing into the HC adsorption catalyst 27 is discharged. This is because it will be difficult to reliably control the reduction side.

In the above oxygen release control, it is more preferable to control so that the air-fuel ratio in the combustion chamber 4 of the engine is 14.0 or more and less than 14.7.

The target value of the reduction degree O _X1 on the upstream side of the three-way catalyst 25 in the initial control is the HC in the oxygen release control.
It is set to a value larger than the reference value O _X20 of the reduction degree on the upstream side of the adsorption catalyst 27 (on the side where the reduction degree is strong). this is,
By increasing the degree of reduction of the exhaust gas on the upstream side of the three-way catalyst 25, oxygen can be promptly released from the oxygen storage substance of the three-way catalyst 25, and the time for initial control can be shortened. Is.

The ignition timing control means 41 includes the ignition circuit 5
A control signal is output to control the ignition timing of the air-fuel mixture according to the operating state of the engine. That is, the ignition timing control means 41 basically sets the ignition timing to M
Although controlled to BT, in the cold operation state of the engine,
When it is confirmed by the desorption determination means 42 that the degree of desorption of HC is large during the split injection, the ignition timing is retarded by a predetermined amount as compared with the MBT, if necessary. Is configured.

The correction means 44 uses the reduction degree O _X3 detected by the third oxygen concentration sensor 28 in the oxygen release control.
Based on the above, the control by the fuel injection control means 40 is corrected. That is, the degree of reduction equivalent to combustion (corresponding to the theoretical air-fuel ratio) at the air-fuel ratio of 14.6 to 14.7 is H.
It is set as a reference value O _X30 on the downstream side of the C adsorption catalyst 27, and the correction means 44 uses the reference value corresponding to combustion when the reduction degree on the downstream side of the HC adsorption catalyst 27 is from air-fuel ratio 14.6 to 14.7. It is configured to correct the feedback value Qfb3 of the fuel injection amount so that the value becomes O _X30 .

The fuel injection control means 40 confirms that the temperature _THCE of the HC adsorption catalyst 27 is _{equal to} or higher than the desorption completion temperature _THC3 at which desorption of HC from the HC adsorbent 27b is completed. It is configured to shift from the oxygen release control to the warm operation control in which the fuel injection amount corresponding to the operation state is feedback-controlled. That is, in the warm operation control, the feedback values Qfb2 and Qfb3 are reset to zero, and the fuel injection is performed based on the degree of reduction O _X1 of the exhaust gas upstream of the three-way catalyst 25 detected by the first oxygen concentration sensor 24. The amount is controlled.

Further, the fuel injection control means 40, for example, in the stratified charge combustion region during the warm operation, causes the injector 7 to collectively inject the fuel at a predetermined timing of the compression stroke so as to be in the vicinity of the ignition plug 6. In addition to burning the fuel of the air-fuel mixture in a distributed state, the combustion control is performed in a stratified combustion mode in which the air-fuel ratio of the air-fuel mixture in the combustion chamber 4 is in a lean state of about 30. Further, in the uniform fuel combustion region during the warm operation, the fuel injection control means 40 collectively injects combustion from the injector 7 in the intake stroke, and makes the average air-fuel ratio of the entire combustion chamber 4 approximately the theoretical air-fuel ratio (A /F=14.7), the combustion control in the uniform combustion mode is executed. In the medium-load medium-speed rotation region of the engine, the fuel may be injected by being divided into an intake stroke and a compression stroke.

-Control Operation- The control operation of the engine exhaust gas purification apparatus configured as described above will be described with reference to the flow charts shown in FIGS.

First, when the control operation is started, in step ST11, the air flow sensor 12, the first to third oxygen concentration sensors 24, 26 and 28, the water temperature sensor 35,
Intake air temperature sensor 36, atmospheric pressure sensor 37, rotation speed sensor 3
8 and each data corresponding to the detection value of the accelerator opening sensor 39 is input, and the process proceeds to step ST12. In step ST12, the target torque Tr of the engine is set from a preset map based on the accelerator opening and the engine speed, and the process proceeds to step ST13. In step ST13, the basic injection amount Qb of fuel and the basic opening Th ₀ of the electric throttle valve 13 are set from a preset map using the target torque Tr and the engine speed as parameters, and step ST1
Move to 4 and drive the electric throttle valve 13 to step S
Move to T15. The basic injection amount Qb and the basic opening Th ₀ of the electric throttle valve 13 are set so that the air-fuel ratio in the combustion chamber 4 of the engine becomes the stoichiometric air-fuel ratio.

In step ST15, the temperature _THCE of the HC adsorption catalyst 27 is derived from the operation history and the like, and the initial control start time T1 which is a predetermined period before the transition time T2 to the desorption operation state is estimated. HC at control start time T1
The initial control start temperature _THC1 which is the temperature of the adsorption catalyst 27 is estimated. Then, the process proceeds to step ST16 and the HC adsorption catalyst 27
Temperature T _HCE it is determined whether or not lower than the initial control start temperature T _HC1 in, when lower than the initial control start temperature T _HC1, the process proceeds to step ST17. In step ST17, the basic injection amount Qb is set to the final injection amount Qp, the process proceeds to step ST18, and it is determined whether or not the injection timing is reached, and when the injection timing comes, the process proceeds to step ST19 and the fuel injection control is executed. . At this time, the air-fuel ratio in the combustion chamber 4 of the engine is set to the stoichiometric air-fuel ratio and the injection control is executed.

On the other hand, when the temperature T _HCE of the HC adsorption catalyst 27 becomes _{equal to} or higher than the initial control start temperature T _HC1 , the determination at step ST16 becomes NO, and the process proceeds from step ST16 to step ST20. In step ST20, the temperature T of the HC adsorption catalyst 27
Based on the _HCE , it is determined whether or not the operation state is such that HC is desorbed from the HC adsorbent 27b. That is, the derived H
It is determined whether the temperature T _HCE of C adsorption catalyst 27 is a leaving operating below the starting temperature T _HC2, it is determined whether or not shift to the desorption operation state.

In step ST20, when the temperature of the HC adsorption catalyst 27 is in the initial operation state below the desorption operation start temperature _THC2 , the determination in step ST16 is YE.
It becomes S, and proceeds to step ST21. In step ST21, the reduction degree O _X of the exhaust gas on the upstream side of the three-way catalyst 25 is added by adding the initial adjustment injection amount Qpre to the basic injection amount Qb.
₁ executes an initial control for setting to the injection control the final injection amount Qp to be burned considerable reduction of the air-fuel ratio 14.0. Then, the process proceeds to step ST18 and the fuel is injected in step ST19 at the injection timing.

That is, in the initial control, the degree of reduction O _X1 of the exhaust gas on the upstream side of the three-way catalyst 25 is controlled to the degree of reduction equivalent to the combustion at the air-fuel ratio of 14.0, so that the exhaust gas has an oxygen concentration of 0. It is controlled to the reduction side (rich side) of 1% or less. As a result, in the initial control, the three-way catalyst 25
Oxygen stored in the oxygen storage material is rapidly released.
Further, by limiting the initial control to within the predetermined period immediately before the transition to the desorption operation state, it is possible to prevent the exhaust gas from being controlled to the reducing side for a period longer than necessary. It is possible to suppress wasteful consumption of fuel.

On the other hand, when the temperature _THCE of the HC adsorption catalyst 27 is _{equal to} or higher than the desorption operation start temperature _THC2 , the determination in step ST20 becomes NO and the routine proceeds to step ST22, where the temperature _THCE of the HC adsorption catalyst 27 is above. and it determines whether less than desorption operation completion temperature T _HC3 a leaving operation start temperature T _HC2 more. That is, it is determined whether or not the desorption operation state in which the desorption amount of HC desorbed from the HC adsorbent 27b exceeds the adsorption amount of HC adsorbed to the HC adsorbent 27b. HC adsorption catalyst 27
When the temperature _{THCE of} is within the above range and is in the desorption operation state, the determination in step ST22 is YES and the process proceeds to step ST23.

In step ST23, the degree of reduction O _X2 of the exhaust gas on the upstream side of the HC adsorption catalyst 27 detected by the second oxygen concentration sensor 26 is higher than the reference value O _X20 (equivalent to combustion at an air-fuel ratio of 14.5). It is determined whether (the degree of return is strong). Then, when the degree of reduction O _X2 of the exhaust gas on the upstream side of the HC adsorption catalyst 27 is higher than the reference value O _X20 , the process proceeds to step ST24 and the feedback value of the fuel injection amount.
Qfb2 is reduced by the correction value β1 and the process proceeds to step ST25.
On the other hand, the degree of reduction O _{X2 of the} exhaust gas is the reference value O _X on the upstream side.
_{When X20} or less, the process proceeds to step ST26, the feedback value Qfb2 of the fuel injection amount is increased by the correction value β2, and the process proceeds to step ST25. That is, in the desorption operation state, the fuel injection amount is increased / decreased so that the degree of reduction is equivalent to the combustion at the air-fuel ratio of 14.5, and the exhaust gas on the upstream side of the HC adsorption catalyst 27 is controlled to the rich side. ing.

In the desorption operation state, since the oxygen storage amount of the oxygen storage material of the three-way catalyst 25 is reduced, oxygen is hardly released, and the HC in the exhaust gas does not react with oxygen. Even when the catalyst 25 is not activated, excess oxygen does not flow out from the three-way catalyst 25. Further, when the three-way catalyst 25 is already activated, the HC in the exhaust gas flows out of the three-way catalyst 25 without reacting with the released oxygen.
The amount of HC flowing into 7 can be controlled accurately.

In step ST25, the degree of reduction O _X3 of the exhaust gas on the downstream side of the HC adsorption catalyst 27 is higher than the reference value O _X30 on the downstream side (corresponding to combustion at the air-fuel ratio of 14.6 to 14.7) ( The degree of return is strong). Then, when the reduction degree O _X3 of the exhaust gas on the downstream side of the HC adsorption catalyst 27 is higher than the reference value O _X30 on the downstream side, the process proceeds to step ST27, and the reduction degree O _X3 previously detected by the third oxygen concentration sensor 28. There determines whether higher than the reference value O _X30 of the downstream, reducing the degree of O _X3 is proceeds only step ST28 when higher than the reference value O _X30 of the downstream side,
The feedback value Qfb3 of the fuel injection amount is reduced by the correction value γ1. When the reduction degree O _X3 detected by the third oxygen concentration sensor 28 last time is equal to or less than the reference value O _X30 on the downstream side, the process proceeds to step ST29 and the feedback value Qfb3
Proceeds to step ST30 without correcting.

On the other hand, in step ST25, when the reduction degree O _X3 of the exhaust gas on the downstream side of the HC adsorption catalyst 27 is less than or equal to the downstream reference value O _X30 , step ST 25
In step 31, the feedback value Qfb3 of the fuel injection amount is increased by the correction value γ2, and the process proceeds to step ST30. That is, only when the reduction degree O _X3 is continuously higher than the reference value O _X30 on the downstream side corresponding to the combustion at the air-fuel ratio of 14.7, that is, when the rich side is continuously controlled, the feedback value Qfb3 is obtained. Correction value γ
By setting 1 to a value smaller than the correction value γ2 for increasing correction, the exhaust gas on the upstream side of the HC adsorption catalyst 27 is easily controlled to the reduction side (rich side) with an oxygen concentration of 0.5% or less. .

In step ST30, whether the degree of reduction O _X1 of the exhaust gas detected by the first oxygen concentration sensor 24 is higher than the degree of reduction reference value O _X10 on the upstream side of the three-way catalyst 25 (the degree of reduction is strong). Determine whether or not. The degree of reduction O _X1 of the exhaust gas is the reduction degree reference value O on the upstream side of the three-way catalyst 25.
When it is lower than _{X10, the} determination in step ST30 is YES, the process proceeds to step ST32, the feedback value Qfb1 of the fuel injection amount is reduced by the correction value α, and the process proceeds to step ST33. On the other hand, when the reduction degree reference value O _X10 or less, the process proceeds from step ST30 to step ST34, the feedback value Qfb1 is increased by the correction value α, and step ST33
Move on to.

In step ST33, the basic injection amount Qb is set.
The final injection amount Qp is derived by adding the above-mentioned respective feedback values Qfb1, Qfb2, Qfb3 to step ST18, and in step ST18, the fuel injection control is executed in accordance with the injection timing.

As shown in FIG. 3 (c), as described above, in the initial control in the initial operating state (between time T1 and time T2), the air-fuel ratio is controlled to the reduction side corresponding to 14.0 and the desorption is performed. In the oxygen release control in the separated operation state (between time T2 and time T3), the air-fuel ratio is controlled to the reduction side corresponding to 14.5.

On the other hand, in step ST22, when the temperature T _HCE of the HC adsorption catalyst 27 becomes _{equal to} or higher than the desorption operation completion temperature T _HC3 , that is, when it is determined that the desorption operation state has ended, step ST35 Go to the feedback value
Qfb2 and feedback value Qfb3 are set to zero, and the process proceeds to step ST30. Then, in the same manner as above, steps ST32 and ST34
At step ST33, the feedback value Qfb1 is increased or decreased by the correction value α, and the final injection amount Qp is derived at step ST33. In other words, the final injection amount Qp is derived by only feedback value Qfb1 which is determined based on the degree of reduction O _X1 of the exhaust gas at the upstream side of the three-way catalyst 25, migrated it from oxygen controlled release in warm operation control Becomes And step
In ST18, in accordance with the injection timing, step ST19
In, fuel injection control is executed. In the warm operation control, feedback control of the fuel injection amount corresponding to the operation state is executed.

[0071]

Other Embodiments of the Invention
In the oxygen release control, the exhaust gas is not limited to the reducing side by increasing the fuel injection amount, but the exhaust gas is reduced to the reducing side by reducing the air supply amount from the secondary air supply passage 32. It may be configured to control.

Further, in the above embodiment, in the initial control, the target value of the degree of reduction of the exhaust gas on the upstream side of the three-way catalyst 25 is based on the upstream side reference value on the upstream side of the HC adsorption catalyst 27 in the oxygen release control. Is not limited to a configuration in which the value is set to a large value, and any configuration may be used as long as it is set on the return side.

Further, the above embodiment is not limited to the structure in which the exhaust gas is controlled to the reducing side by the air-fuel ratio control of the engine in the initial control, and the control by the secondary air or the like can be applied.

Further, in the above embodiment, in the oxygen release control, instead of the one-sided weighted feedback control in which the increase correction value β2 of the fuel injection amount feedback value Qfb2 is set to a value larger than the reduction correction value β1, the HC adsorption catalyst 27 is replaced. One-sided feedback control may be performed in which the feedback value is corrected toward the reduction side only when the exhaust gas on the upstream side is on the oxidation side of the reference value O _X20 .

[0075]

As described above, according to the invention of claim 1, the amount of oxygen stored in the oxygen storage material of the upstream catalyst is reduced before the HC adsorption catalyst shifts to the desorption operation state. Since it is set, it is possible to prevent excess oxygen from flowing into the HC adsorption catalyst during the desorption operation state, and easily and accurately control the degree of reduction of the exhaust gas that contacts the HC adsorption catalyst. can do. That is, since oxygen is not released from the oxygen storage substance of the upstream catalyst, it is possible to prevent excess oxygen from flowing into the HC adsorption catalyst while the upstream catalyst is not activated yet, while the upstream catalyst is not activated. When already activated, the concentration of HC flowing out from the upstream catalyst can be accurately estimated.

According to the second aspect of the invention, the oxygen storage capacity of the oxygen storage substance of the upstream catalyst can be promptly and surely reduced before shifting to the desorption operation state, and more than necessary. It is possible to prevent the exhaust gas from being controlled to the reduction side for a long period.

According to the third aspect of the invention, the period during which the oxygen concentration in the exhaust gas is reduced by the stored oxygen amount reducing means can be shortened.

According to the invention of claim 4, the feedback of the air-fuel ratio control, which takes a long time to respond, can be avoided as much as possible, and the exhaust gas is accurately transferred to the reducing side immediately after the transition to the desorption operation state. Can be controlled.

Further, according to the fifth aspect of the present invention, the exhaust gas on the upstream side of the HC adsorption catalyst can be reliably controlled to the reducing side in the desorption operation state.

[Brief description of drawings]

FIG. 1 is an overall view showing an overall configuration of an engine exhaust gas purification apparatus according to an embodiment.

FIG. 2 is a sectional view partially showing the structure of an HC adsorption catalyst.

FIG. 3A is a characteristic diagram showing the operation of the HC adsorption catalyst, FIG. 3B is a characteristic diagram showing a temperature change of the HC adsorption catalyst, and FIG. 3C is a characteristic diagram showing a change in the air-fuel ratio. It is a characteristic view to show.

FIG. 4 is a flowchart showing the first half of the control operation of the exhaust emission control system for the engine according to the embodiment.

FIG. 5 is a flowchart showing the latter half of the control operation of the engine exhaust gas purification apparatus according to the embodiment.

[Explanation of symbols]

22 Exhaust passage 25 Three-way catalyst (upstream catalyst) 27 HC adsorption catalyst 27b HC adsorbent 42 Desorption determination means (determination means)

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) F01N 3/24 F01N 3/24 R 3/28 301P 3/28 301 F02D 41/06 305 F02D 41/06 305 41/14 310E 41/14 310 310L B01D 53/36 103Z 101B (72) Inventor Yashiko Kato Shinchi 3-1, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) Masahiko Shigets Fuchu-cho, Aki-gun, Hiroshima Prefecture Shinchi 3-1, Mazda Co., Ltd. (72) Inventor Hisaya Kawabata Fuchu-cho, Aki District, Hiroshima Prefecture Shinchi 3-1, Mazda Co., Ltd. F-term (reference) 3G091 AA02 AA11 AA17 AA23 AA24 AA28 AB02 AB03 AB10 BA03 BA14 BA15 BA19 BA19 BA32 CA13 CA22 CA26 CB02 CB03 CB05 CB07 CB08 DA01 DA02 DA04 DB10 DC01 DC03 EA00 EA01 EA05 EA06 EA07 EA23 EA30 EA31 EA34 FA02 FA04 FB02 FB10 FB11 FB12 FC07 GA16 GB01X GB04Y GB06W GB07W GB09Y GB10X GB10Y GB16X GB17X HA08 HA09 HA18 HA19 HA36 HA37 HA42 HB03 HB05 3G301 HA01 HA04 HA06 HA13 H A17 JA25 JA26 JB09 LA03 LB04 MA01 MA11 MA18 MA26 NA06 NA07 NA08 ND01 NE01 NE06 NE11 NE12 NE13 NE14 NE15 PA01B PA01Z PA07B PA07Z PA09B PA09Z PA10B PA10Z PA11B PA11Z PB08B PB08Z PD04A PD04B PD04Z PD09A PD09B PD09Z PE01B PE01Z 4D048 AA18 AB07 CC32 DA01 DA02 DA03 DA20 EA04

Claims (5)

[Claims] 1. An H which is arranged in an exhaust passage of an engine and which adsorbs HC while desorbing adsorbed HC as the temperature rises.
C adsorbent, an oxygen storage material that stores oxygen on the oxidation side and releases oxygen on the reduction side, and H desorbed from the HC adsorption material.
Judgment to determine whether or not the HC adsorption catalyst containing a catalyst metal that oxidizes C and the desorption operation state in which the desorption amount of HC from the HC adsorbent exceeds the adsorption amount to the HC adsorbent When the transition to the desorption operation state is determined by the means and the determination means, the exhaust gas in the upstream side of the HC adsorption catalyst or in the HC adsorption catalyst is controlled to the reduction side so that oxygen is released from the oxygen storage substance. Reducing degree control means, an upstream catalyst that is disposed in the exhaust passage on the upstream side of the HC adsorption catalyst, contains an oxygen storage material that stores oxygen on the oxidation side and releases oxygen on the reduction side, and deoxidizes by the determination means. An engine exhaust comprising: a stored oxygen amount reducing means for reducing the amount of oxygen stored in the oxygen storage substance of the upstream catalyst before it is determined that the operating state has shifted to the separated operation state. Purification device. 2. The exhaust gas amount reducing means according to claim 1, wherein the stored oxygen amount reducing means exhausts the upstream of the upstream catalyst or the inside of the upstream catalyst within a predetermined period immediately before the transition timing to the desorption operation state determined by the determining means. An engine exhaust purification device, which is configured to reduce the oxygen concentration in gas to 0.1% or less. 3. The reduction degree control means according to claim 1 or 2, wherein the reduction degree control means sets a reference value of the degree of reduction of exhaust gas on the upstream side of the HC adsorption catalyst or in the HC adsorption catalyst. The control unit is configured so that the degree of reduction of exhaust gas upstream of the upstream catalyst or inside the upstream catalyst is controlled to a target value that is set to a value greater than the reference value. Engine exhaust purification device. 4. The reduction degree control unit according to claim 1, wherein the air-fuel ratio of the engine is controlled so that the oxygen concentration of the exhaust gas on the upstream side of the HC adsorption catalyst or in the HC adsorption catalyst becomes a predetermined value or less. An engine exhaust gas purification device characterized in that it is configured. 5. The air-fuel ratio control by the reduction degree control means according to claim 4, wherein the one-sided weighted feedback control for setting the correction value of the feedback value in the reduction side direction to be larger than the correction value in the oxidation side direction, or the exhaust gas An exhaust emission control device for an engine, characterized in that it is carried out by a one-sided feedback control for correcting a feedback value toward a reduction side when it is on an oxidation side with respect to a reference.