JP4645570B2 - Engine exhaust gas purification device - Google Patents

Description

  The present invention relates to an engine exhaust gas purification apparatus suitable for use in a vehicle.

Conventionally, a technique for purifying exhaust gas discharged from an engine with a three-way catalyst is known. However, this three-way catalyst is not activated until it reaches a certain temperature and cannot fully exhibit its purification ability.
Therefore, in recent years, a technology that shortens the time until the three-way catalyst is activated by mounting the three-way catalyst close to the engine to supply high-temperature exhaust gas directly to the three-way catalyst has been widely used. It has been.

In addition, when the purification by this three-way catalyst is not sufficient, many hydrocarbons (HC) are contained in the exhaust gas. After this HC is adsorbed and then the temperature of the three-way catalyst is raised to some extent In recent years, a technology for a catalyst (so-called HC trap catalyst) that desorbs and purifies adsorbed HC has also been widely used.
As an example of such a technique, the technique of the following patent document 1 is mentioned.

In general, a three-way catalyst layer that functions as a three-way catalyst is formed on the HC trap catalyst, or a three-way catalyst is disposed downstream of the HC trap catalyst. The exhaust gas is purified by chemically changing HC, nitrogen oxide (NOx) and carbon monoxide (CO) to nitrogen (N ₂ ), carbon dioxide (CO ₂ ) and water (H ₂ O). ing.

Therefore, in the technique of Patent Document 1, the control for increasing the oxygen concentration in the exhaust gas is performed by measuring the timing at which HC is desorbed from the HC trap catalyst, that is, the exhaust gas is desorbed from the HC trap catalyst in a timely and lean atmosphere. Control that facilitates purification of HC is required.
JP-A-9-85078

However, when a three-way catalyst is provided upstream of the HC trap catalyst, even if the exhaust gas atmosphere is made lean by reducing the fuel injection amount in the engine, the exhaust gas atmosphere supplied to the HC trap catalyst is made lean. There is a problem that a time lag until it is realized. Hereinafter, this problem will be described in more detail.
The three-way catalyst generally carries an oxygen storage agent (hereinafter referred to as “OSC agent”). This is to store oxygen in the exhaust gas when the exhaust gas is in a lean atmosphere, and to release the stored oxygen into the exhaust gas when the exhaust gas is in a rich atmosphere. The purification performance can be kept high.

However, even if the exhaust gas atmosphere in the engine is leaned in order to make the exhaust gas atmosphere in the HC trap catalyst lean, the OSC agent stores oxygen, so that the exhaust gas supplied to the HC trap catalyst becomes somewhat lean. This period is required.
For this reason, in the prior art as shown in Patent Document 1, the oxidation of HC desorbed from the HC trap catalyst is delayed by the amount of delay in leaning the exhaust gas reaching the HC trap catalyst, and the exhaust gas performance is reduced. There is a problem to do.

In order to alleviate such problems, it is conceivable to increase the leaning period by increasing the timing of leaning or to increase the degree of leaning, but in that case, a large torque shock occurs during leaning As a result, problems that impair drivability occur.
The present invention has been devised in view of such problems, and it is possible to quickly change the air-fuel ratio of the exhaust gas supplied to the HC adsorption catalyst and improve exhaust gas performance without generating a large torque shock. An object of the present invention is to provide an exhaust gas purification device for an engine.

  In order to achieve the above object, an exhaust gas purification apparatus for an engine according to the present invention (Claim 1) includes an engine having a first cylinder provided with a first fuel injection device and a second cylinder provided with a second fuel injection device. An exhaust gas purifying device for purifying exhaust gas from the engine, the first oxygen storage catalyst being connected to the first cylinder of the engine and capable of storing oxygen contained in the exhaust gas from the first cylinder, and the engine A second oxygen storage catalyst which is a catalyst connected to the second cylinder and capable of storing oxygen contained in the exhaust gas from the second cylinder, and is connected to the downstream side of the first and second oxygen storage catalysts. HC adsorption catalyst which is a catalyst for adsorbing the contained hydrocarbon, and fuel into the two cylinders by the second fuel injection device when the hydrocarbon adsorbed on the HC adsorption catalyst is desorbed from the HC adsorption catalyst Control that prohibits injection And a partial fuel cut executing means for executing the partial fuel cut that, the second oxygen storage catalyst, the oxygen storage capacity than the first oxygen storage catalyst is characterized in that it is set to be lower.

  Further, in the exhaust gas purifying apparatus for an engine according to the second aspect of the present invention, in the content of the first aspect, the first and second oxygen storage catalysts are each a three-way catalyst, and the warming-up of the engine First control means for controlling the first fuel injection device so that the exhaust gas from one cylinder periodically repeats the lean air-fuel ratio and the rich air-fuel ratio; and the exhaust gas from the second cylinder is lean after the engine is warmed up Second control means for controlling the second fuel injection device to periodically repeat the air-fuel ratio and the rich air-fuel ratio, the second control means being leaner than the first control means and the rich air-fuel ratio. And the inversion period is shortened or the inversion amplitude is reduced.

  According to a third aspect of the present invention, there is provided an exhaust gas purification apparatus for an engine according to the present invention, wherein the first control means is a first exhaust gas that is an air-fuel ratio of the first exhaust gas discharged from the first cylinder. First exhaust gas air-fuel ratio detection means for detecting an air-fuel ratio, and the exhaust gas from the first cylinder is made into a lean air-fuel ratio and a rich air-fuel ratio based on the first exhaust gas air-fuel ratio detected by the first exhaust gas air-fuel ratio detection means Feedback control means for feedback-controlling the first fuel injection device so as to periodically repeat the above, the second control means from the second cylinder in a reversal period shorter than the reversal period by the feedback control means An open-loop control means for performing open-loop control of the second fuel injection device so that the exhaust gas of the engine periodically repeats a lean air-fuel ratio and a rich air-fuel ratio That.

According to the exhaust gas purification apparatus of the present invention, the exhaust gas performance can be improved without changing the air-fuel ratio of the exhaust gas supplied to the HC adsorption catalyst quickly and generating a large torque shock. (Claim 1)
Further, when each of the first and second oxygen storage catalysts is a three-way catalyst, the first exhaust gas periodically repeats the lean air-fuel ratio and the rich air-fuel ratio in the first cylinder and the second cylinder after the engine is warmed up. In controlling the second fuel injection device, the oxygen storage capacity of the second oxygen storage catalyst is reduced by making the inversion cycle of the lean air-fuel ratio and the rich air-fuel ratio on the second cylinder side shorter than that on the first cylinder side. Even so, it is possible to prevent the exhaust gas purification ability of the second oxygen storage catalyst from being lowered. (Claim 2)
Furthermore, the first cylinder side is set to feedback control based on the detection output of the first exhaust gas air-fuel ratio detection means, and the second cylinder side is subjected to open loop control with an inversion period shorter than the inversion period by the feedback control, so that the oxygen storage capacity is increased. Suitable control can be applied to each of the first cylinder provided with the relatively high first oxygen storage catalyst and the second cylinder having a relatively low oxygen storage capacity. In particular, the oxygen storage capacity of the second oxygen storage catalyst is reduced. Even if high exhaust gas purification performance can be ensured, exhaust gas purification performance can be improved comprehensively. (Claim 3)

Hereinafter, an engine exhaust gas purification apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing the overall configuration, and FIG. 2 is a schematic flowchart showing the control contents. 3 is a schematic graph showing the action and effect.
As shown in FIG. 1, one intake manifold 11 and two exhaust manifolds 12 and 13 are connected to a vehicle engine (hereinafter simply referred to as “engine”) 10.

The engine 10 is a V-type 6-cylinder gasoline engine. In FIG. 1, one engine 14A in the first cylinder group 14 in the first bank B ₁ and the second cylinder group 15 in the second bank B ₂ are used. 1 cylinder 15A.
The first and second cylinder groups 14 and 15 are provided with a first injector (first fuel injection device) 35 and a second injector (second fuel injection device) 36, respectively.

A surge tank 16 is formed on the upstream side of the intake manifold 11, and the downstream side is connected to each intake port 17 of the first cylinder group 14 and each intake port 18 of the second cylinder group 15.
Further, a throttle valve (not shown) is provided upstream of the surge tank 16 so that the amount of fresh air flowing into the first and second cylinder groups 14 and 15 can be adjusted. The throttle valve is mechanically connected to an accelerator pedal (not shown), and an idle switch 19 is provided on the accelerator pedal.

The idle switch 19 is a switch that is turned on when the accelerator pedal is not depressed, and is electrically connected to an ECU 40 described later.
The first exhaust manifold 12 has an upstream side connected to each exhaust port 21 of the first cylinder group 14 and a downstream side connected to a first three-way catalyst (first oxygen storage catalyst) 23.
On the other hand, the second exhaust manifold 13 has an upstream side connected to each exhaust port 24 of the second cylinder group 15 and a downstream side connected to a second three-way catalyst (second oxygen storage catalyst) 24.

The exhaust gas discharged from the first cylinder group 14 is referred to as a first exhaust gas G _EX1, and the exhaust gas discharged from the second cylinder group 15 is referred to as a second exhaust gas G _EX2 .
These first and second three-way catalysts 23 and 24 are respectively carbon monoxide (CO), hydrocarbon (HC) and hydrocarbons contained in the first and second exhaust gases G _EX1 and G _EX2 discharged from the engine 10. The exhaust gas is purified by chemically changing the nitrogen compound (NOx) to nitrogen (N ₂ ), carbon dioxide (CO ₂ ), and water (H ₂ O).

A first upstream O ₂ sensor (first exhaust gas air-fuel ratio detecting means) 25 is provided upstream of the first three-way catalyst 23. The first upstream O ₂ sensor 25 detects the first exhaust gas air-fuel ratio AF _1A that is the air-fuel ratio of the first exhaust gas G _EX1 supplied to the first three-way catalyst 23. The detection result by the first upstream O ₂ sensor 25 is read by the ECU 40 described later as a voltage value.

Similarly, a second upstream O ₂ sensor (second exhaust gas air-fuel ratio detection means) 26 is provided upstream of the second three-way catalyst 24. The second upstream O ₂ sensor 26 detects a second exhaust air / fuel ratio AF _2A that is the air / fuel ratio of the second exhaust gas G _EX2 supplied to the second three-way catalyst 24.
A first downstream O ₂ sensor 27 is provided on the downstream side of the first three-way catalyst 23. The first upstream O ₂ sensor 27 detects the air-fuel ratio AF _1B of the first exhaust gas G _EX1 that is supplied to the HC trap catalyst 29 described later via the first three-way catalyst 23. The detection result by the first downstream O ₂ sensor 27 is read by the ECU 40 described later as a voltage value.

Similarly, a second downstream O ₂ sensor 28 is provided on the downstream side of the second three-way catalyst 24. The second upstream O ₂ sensor 28 detects the air-fuel ratio AF _2B of the second exhaust gas G _EX2 that is supplied to the HC trap catalyst 29 described later through the second three-way catalyst 24. The detection result by the second downstream O ₂ sensor 28 is also read by the ECU 40 described later as a voltage value.

It should be noted that the voltages indicating the detection results by the first and second upstream O ₂ sensors 25 and 26 and the first and second downstream O ₂ sensors 27 and 28 have higher air-fuel ratios AF _1A , AF _1B , AF _2A , and AF _2B are low, that is, the atmosphere is rich (the amount of O ₂ decreases). On the other hand, the lower the value, the air-fuel ratios AF _1A , AF _1B , AF _2A , AF _2B is high, that is, the atmosphere is leaner (the amount of O ₂ is increased).

The first three-way catalyst 23 is connected to an HC trap catalyst (HC adsorption catalyst) 29 via a first exhaust pipe 31. Similarly, the HC trap catalyst 29 is connected to the second three-way catalyst 24 via the second exhaust pipe 32. As shown in FIG. 1, the first exhaust pipe 31 and the second exhaust pipe 32 merge upstream of the HC trap catalyst 29.
The first and second three-way catalysts 23 and 24 each carry ceria as an OSC agent, and can store O ₂ contained in the exhaust gases G _EX1 and G _EX2. Yes.

The second three-way catalyst 24 is set to have a lower oxygen storage capacity than the first three-way catalyst 23. More specifically, the oxygen storage capacity of the second three-way catalyst 24 and the first three-way catalyst 23 is set to be different by the following method.
[A] Setting focusing on dynamic oxygen storage capacity ・ Absolute amount of OSC agent ・ Supporting form of OSC agent (surface layer or inner layer)
-Positional relationship between OSC agent and catalyst noble metal-Particle size of OSC agent [B] Setting focusing on static oxygen storage capacity-Absolute amount of OSC agent-Type of OSC agent In other words, catalyst noble metal on OSC agent The OSC agent may be supported separately from the catalyst noble metal. In general, when the catalyst noble metal is supported on the OSC agent (the former), The oxygen storage capacity is higher than when the OSC agent is supported separately from the catalyst noble metal (the latter).

In addition, when the amount of the OSC agent is constant, the reaction area can be increased by reducing the area of the gap between the particles of the OSC agent by reducing the particle size of the OSC agent. The oxygen storage capacity can be improved.
As a material used as an OSC agent, a composite oxide of ceria / zirconia is generally used, but an additive for changing the blending ratio of ceria and zirconia or improving heat resistance (for example, The properties of the OSC agent can be appropriately changed by adding yttrium or the like. In general, the oxygen storage capacity can be increased by increasing the blending ratio of ceria.

  In the present embodiment, ceria is mainly used as the OSC agent, and heat resistance is improved by adding zirconia to the ceria. Further, the oxygen storage capacity of the first and second three-way catalysts 23 and 24 is individually set by changing the addition method of the zirconia or adding other additives not limited to zirconia. I can do it.

In the present embodiment, particularly focusing on the absolute amount of the OSC agent, the amount of ceria supported on the second three-way catalyst 24 is made smaller than the amount of ceria supported on the first three-way catalyst 23. Thus, the oxygen storage capacity of the first three-way catalyst 23 is set to be higher than the oxygen storage capacity of the second three-way catalyst 24.
The HC trap catalyst 29 adsorbs hydrocarbons (HC) contained in the third exhaust gas G _EX3 where the first exhaust gas G _EX1 and the second exhaust gas G _EX2 merge, and then the HC trap catalyst 29 is heated. Then, the adsorbed HC is released into the third exhaust gas _GEX3 .

Further, the HC trap catalyst 29 is formed with a three-way catalyst layer (not shown), and chemically changes CO, HC and NOx contained in the third exhaust gas G _EX3 to N ₂ , CO ₂ and H ₂ O. Thus, the third exhaust gas G _EX3 can be purified.
The HC trap catalyst 29 is provided with an HC trap catalyst temperature sensor 37 that detects the temperature of the HC trap catalyst 29. The detection result of the HC trap catalyst is read by the ECU 40 as needed.

Furthermore, this engine 10, the cooling water temperature T _W coolant temperature sensor 33 for detecting are provided to the detection result is adapted to be written at any time read by ECU 40.
The ECU 40 is an electronic control unit having an interface, a memory, a CPU, etc., all not shown, and all of them as software include a partial F / C execution unit (partial fuel cut execution means) 41, a feedback control unit (feedback control). Means) 42 and a forced modulation control unit (open loop control means) 43.

  Among these, the partial F / C execution unit 41 efficiently and without generating a large torque shock when the HC adsorbed on the HC trap catalyst 29 is desorbed from the HC trap catalyst 29. Executing partial fuel cut (partial fuel cut; hereinafter referred to as “partial F / C”), which is control for prohibiting fuel injection into the second cylinder 15 by the second injector 36 to supply oxygen to It is.

More specifically, the partial F / C execution unit 41 executes the partial F / C when all of the following four conditions are satisfied.
[Condition 1] Cooling water temperature T _W is equal to or lower than threshold temperature T _W1 [Condition 2] Idle switch 19 is ON [Condition 3] Temperature T _HCT of HC trap catalyst 29 exceeds lower limit threshold T _MIN [Condition 4] The temperature T _HCT of the HC trap catalyst 29 is _lower than the upper limit threshold T _MAX . These four conditions are referred to as partial F / C execution conditions.

Here, the grounds for defining these conditions 1 to 4 will be described.
Condition 1 is a condition for determining that the engine 10 is in a cold state. That is, when the engine 10 is in a cold state, a large amount of HC is contained in the first and second exhaust gases G _EX1 and G _EX2 discharged from the engine 10, but this large amount of HC is adsorbed by the HC trap catalyst 29. Is done. Thereafter, when the temperature of the HC trap catalyst 29 is increased, HC adsorbed on the HC trap catalyst 29 is desorbed. Therefore, when the engine 10 is in the cold state, this condition 1 is set assuming that it is assumed that the partial F / C control is necessary.

Condition 2 is a condition set to determine that the torque output from the engine 10 is not particularly required and that there is no problem even if the partial F / C is executed.
Conditions 3 and 4 are conditions set to determine whether or not the temperature T _HCT of the HC trap catalyst 29 is within a predetermined temperature range where HC is desorbed from the HC trap catalyst 29. In the present embodiment, the lower limit threshold T _MIN and the upper limit threshold T _MAX are set to about 100 ° C. and about 350 ° C., respectively.

The feedback control unit 42 performs well-known O ₂ sensor feedback control after the engine is warmed up (substantially after the activation of the first three-way catalyst 23), and is detected by the first upstream O ₂ sensor 25. Based on the first exhaust gas air-fuel ratio AF _1A , the fuel injection amount injected from the first injector 35 is feedback-controlled. In this case, as is well known, the air-fuel ratio of the exhaust gas upstream of the first three-way catalyst 23 periodically repeats the lean air-fuel ratio and the rich air-fuel ratio, and the average air-fuel ratio is close to the theoretical air-fuel ratio. It is controlled to become. In the present embodiment, the first control cycle t _1, which is the reversal cycle between the lean air-fuel ratio and the rich air-fuel ratio, is about 2 seconds during idling, and the rotational speed increases (exhaust gas flow rate increases) during traveling. Shortens accordingly.

Further, the forced modulation control unit 43 leans in the second control cycle t ₂ that is shorter than the first control cycle t ₁ after the engine is warmed up (substantially after the activation of the second three-way catalyst 24). The second injector 36 is subjected to open loop control so that the inversion of the air-fuel ratio and the rich air-fuel ratio is repeated. Since this modulation control is already a known technique as described in, for example, Japanese Patent Application Laid-Open No. 2006-77735, detailed description thereof is omitted here. In the present embodiment, the second control cycle t ₂ is set to about 0.1 to 1 second (1 to 10 Hz), and more preferably set to about 1 second (10 Hz).

Since the exhaust gas purification apparatus for an engine according to an embodiment of the present invention is configured as described above, the following operations and effects are achieved.
In step S11 in the flowchart of FIG. 2, ECU 40 includes a detection result T _W by the cooling water temperature sensor 33, with reads a detection result T _HCT by HC trap catalyst temperature sensor 37, detects the state of the idle switch 19.

Then, the partial F / C execution unit 41 has the cooling water temperature T _W equal to or lower than the threshold value T _W1 (condition 1), the idle switch 19 is turned on (condition 2), and the temperature T _HCT of the HC trap catalyst 29 is the lower limit. It is determined whether or not any of the conditions between the threshold value T _MIN and the upper threshold value T _MAX (conditions 3 and 4) is satisfied (step S12). If these four conditions are satisfied, the partial F / C Assuming that the condition is satisfied (Yes route in step S12), partial F / C is executed (step S13).

In addition, the partial F / C execution part 41 does not perform this partial F / C, when any one of said conditions 1-4 is not satisfy | filled (No route of step S12). That is, under the condition that HC is separated from the HC trap catalyst 29 such that the cooling water temperature T _W is equal to or lower than the threshold value T _{W1 and} the temperature T _HCT of the HC trap catalyst 29 is between the lower limit threshold T _MIN and the upper limit threshold T _MAX. If the idle switch 19 is not on, partial F / C is not executed. As described above, even if the HC is separated, the partial F / C is executed only under a limited condition. Therefore, the exhaust gas supplied to the HC trap catalyst 29 when the partial F / C is executed. From the viewpoint of exhaust gas purification, it is desirable to make the gas lean quickly.

From such a viewpoint, when the partial F / C is executed using FIG. 3, the change in the air-fuel ratio AF _2B of the second exhaust gas G _EX2 supplied to the HC trap catalyst 29 is shown in this embodiment and the prior art. And will be described.
FIG. 3 shows the detection result by the second upstream O ₂ sensor 26 and the detection result by the second downstream O ₂ sensor 28 continuously, where t ₀ is the partial F / C. Indicates the point in time. T _PFC represents the execution period of the partial F / C.

When the partial F / C is executed, it is detected by the second upstream O ₂ sensor 26 that the second exhaust gas G _EX2 suddenly becomes lean (see the alternate long and short dash line L ₁ ).
Then, in the prior art, after a lapse of t _a seconds from the partial F / C is performed, the second downstream O ₂ sensor 28, the second exhaust gas G _EX2 supplied to the HC trap catalyst 29 is leaner it is detected (see the dotted line L _3).

On the other hand, in the present embodiment, the second exhaust gas G _EX2 supplied to the HC trap catalyst 29 is lean after t _b seconds (however, t _a > t _b ) after the partial F / C is executed. it has been detected that reduction (see the solid line L _2).
That is, in the present embodiment, the amount of O ₂ contained in the second exhaust gas G _EX2 supplied to the HC trap catalyst 29 in an extremely short period (t _b seconds) after executing the partial F / C compared to the conventional case. Can be increased.

That is, when the first and second three-way catalysts 23 and 24 are activated, a large amount of HC is not adsorbed by the HC trap catalyst 29, but when the engine 10 is cold-started. The first and second three-way catalysts 23 and 24 are not activated, so that the exhaust gases G _EX1 and G _EX2 containing a large amount of HC pass through the first and second three-way catalysts 23 and 24. End up. In such a case, the HC trap catalyst 29 purifies the third exhaust gas _GEX3 released to the atmosphere by adsorbing a lot of HC.

Thereafter, the HC trap catalyst 29 HC trap catalyst 29 is heated by the heat contained in the third exhaust gas G _EX3, the three-way catalyst layer formed on the HC trap catalyst 29, included in the third exhaust gas G _EX3 Purification is performed by chemically changing CO, HC and NOx to N ₂ , CO ₂ and H ₂ O.
In the present embodiment, partial F / C is executed, the atmosphere of the second exhaust gas G _{EX2 is} quickly made lean, and the third exhaust gas G containing a large amount of O ₂ with respect to the HC trap catalyst 29 (ie, in a lean atmosphere). By supplying _EX3 , the oxidation of HC desorbed from the HC trap catalyst 29 can be rapidly promoted, and the performance of the third exhaust gas _GEX3 released to the atmosphere can be improved. In addition, when the exhaust gas supplied to the HC trap catalyst 29 is made lean to purify the HC separated from the HC trap catalyst 29, a method of executing partial F / C when the idle switch 19 is on is used. Therefore, there is no problem that a large torque shock occurs or the drivability is greatly impaired.

Since the second three-way catalyst 24 is set to have a lower oxygen storage capacity than the first three-way catalyst 23, the air-fuel ratio of the second exhaust gas G _EX2 supplied to the second three-way catalyst 24 is set. When the fluctuation period of AF _2A is long, the exhaust gas purification ability is reduced, but the inversion of the lean air-fuel ratio and the rich air-fuel ratio is repeated in the second control period t ₂ shorter than the first control period t _1. Thus, by performing open loop control of the second injector 36, it is possible to improve the purification efficiency of the second exhaust gas _GEX2 in the second three-way catalyst 24, and to lower the oxygen storage capacity, the second three-way catalyst 24. It is possible to avoid a situation where the exhaust gas purification capacity of the engine is reduced.

Thus, according to the exhaust gas purifying apparatus for an engine according to an embodiment of the present invention to quickly change the air-fuel ratio AF ₃ of the exhaust gas G _EX3 supplied to the HC trap catalyst 29, the exhaust gas is discharged to the atmosphere G _EX3 Can be efficiently purified.
In addition, after the engine is warmed up, the second injector 36 is subjected to open-loop control at a second control cycle t ₂ that is shorter than the first control cycle t ₁ , thereby reducing the reduction in the exhaust gas purification capacity of the second three-way catalyst 24. Can be efficiently compensated.

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and various modifications can be made without departing from the spirit of the present invention.
In the above-described embodiment, the case where the engine 10 is a V-type 6-cylinder gasoline engine has been described as an example. However, the present invention is not limited to this. For example, an in-line type engine may be used, and the present invention can be applied to an engine having two or more cylinders without being limited to six cylinders.

1 is a schematic block diagram showing an overall configuration of an engine exhaust gas purification apparatus according to an embodiment of the present invention. It is a typical flowchart which shows the control content of the exhaust gas purification apparatus of the engine which concerns on one Embodiment of this invention. It is a typical graph which shows the effect | action and effect of the exhaust gas purification apparatus of the engine which concerns on one Embodiment of this invention.

Explanation of symbols

10 Engine 14 First cylinder group (first cylinder)
15 2nd cylinder group (2nd cylinder)
23 First three-way catalyst (first oxygen storage catalyst)
24 Second three-way catalyst (second oxygen storage catalyst)
25 First upstream O ₂ sensor (first exhaust gas air-fuel ratio detecting means)
29 HC trap catalyst (HC adsorption catalyst)
35 1st injector (1st fuel-injection apparatus)
36 Second injector (second fuel injection device)
41 Partial F / C execution part (partial fuel cut execution means)
42 Feedback control unit (feedback control means)
43 Forced modulation controller (open loop control means)

Claims (3)

An exhaust gas purification device for purifying exhaust gas from an engine including a first cylinder provided with a first fuel injection device and a second cylinder provided with a second fuel injection device,
A first oxygen storage catalyst which is connected to the first cylinder of the engine and is a catalyst capable of storing oxygen contained in exhaust gas from the first cylinder;
A second oxygen storage catalyst which is connected to the second cylinder of the engine and is a catalyst capable of storing oxygen contained in the exhaust gas from the second cylinder;
An HC adsorption catalyst that is connected to the downstream side of the first and second oxygen storage catalysts and adsorbs hydrocarbons contained in the exhaust gas;
Partial fuel that performs partial fuel cut, which is control for prohibiting fuel injection into the two cylinders by the second fuel injection device when hydrocarbons adsorbed on the HC adsorption catalyst are desorbed from the HC adsorption catalyst Cutting execution means,
The exhaust gas purifying apparatus for an engine, wherein the second oxygen storage catalyst is set to have an oxygen storage capacity lower than that of the first oxygen storage catalyst. Each of the first and second oxygen storage catalysts is a three-way catalyst;
First control means for controlling the first fuel injection device so that the exhaust gas from the first cylinder periodically repeats a lean air-fuel ratio and a rich air-fuel ratio after the engine is warmed up;
A second control means for controlling the second fuel injection device so that the exhaust gas from the second cylinder periodically repeats a lean air-fuel ratio and a rich air-fuel ratio after the engine is warmed up;
2. The engine according to claim 1, wherein the second control means is configured to shorten the inversion period of the lean air-fuel ratio and the rich air-fuel ratio or to make the inversion amplitude smaller than the first control means. Exhaust gas purification equipment. The first control means includes first exhaust gas air-fuel ratio detection means for detecting a first exhaust gas air-fuel ratio that is an air-fuel ratio of the first exhaust gas discharged from the first cylinder;
The first fuel injection device is configured so that the exhaust gas from the first cylinder periodically repeats a lean air-fuel ratio and a rich air-fuel ratio based on the first exhaust gas air-fuel ratio detected by the first exhaust gas air-fuel ratio detection means. Feedback control means for feedback control,
The second control means opens the second fuel injection device so that the exhaust gas from the second cylinder periodically repeats the lean air-fuel ratio and the rich air-fuel ratio with an inversion period shorter than the inversion period by the feedback control means. The engine exhaust gas purification apparatus according to claim 2, further comprising an open loop control means for performing loop control.

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