JP2003166436A - Exhaust emission control device for multicylinder engine of cylinder injection type and spark ignition type - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for a multicylinder engine of cylinder injection and spark ignition type which promotes purification of exhaust gas when an engine temperature is low and activating catalyst early, while improving engine fully opening performance. <P>SOLUTION: A dual type exhaust manifold system collecting exhaust gas passages into a plurality of exhaust gas passages using cylinders whose ignition order is not continuous as one set is adopted in the multicylinder engine of cylinder ignition type and spark ignition type. Exhaust gas from a cylinder set in a part is separated from exhaust gas from a remaining cylinder set in a plurality of exhaust gas passages to lead these exhaust gases up to just upstream side of exhaust gas purifying catalyst in this condition. When starting the engine in a cold condition (S10), two-step combustion is performed in the cylinder set (#2, #3 cylinders) in a part (S14), and two-step combustion is not performed and compression process injection only is performed in the remaining cylinder set (#1, #4 cylinders) (S12). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification apparatus for a cylinder injection type spark ignition type multi-cylinder engine, and more particularly to an exhaust gas purification technology at a cold start and a temperature raising technology of an exhaust purification catalyst.

[0002]

Related Background Art Generally, an exhaust system of an automobile engine is provided with a catalytic converter immediately after the exhaust manifold or under the floor. It simultaneously purifies and reduces HC (hydrocarbons), CO (carbon monoxide), and NOx (nitrogen oxides).

In recent years, an in-cylinder injection spark ignition multi-cylinder engine has been put into practical use, which can be operated even at a super lean air-fuel ratio by injecting fuel in a compression stroke. In the cylinder injection type spark ignition multi-cylinder engine,
Fuel injection timing can be set freely, for example, fuel is injected in the compression stroke (main injection) in a situation where the catalytic converter is not active, such as when the engine is cold starting (low temperature) where the exhaust gas temperature is low. The residual O ₂ (residual oxygen) and unburned HC are injected by additional injection (sub-injection) after the expansion stroke.
Alternatively, CO is discharged, and these residual O ₂ and unburned HC or CO are reacted in the exhaust system (the region from the exhaust port including the exhaust valve to the catalytic converter) to promote exhaust gas purification, and the reaction heat thereof. There is known a two-stage combustion technology for early activation of a catalytic converter.

Various manifold systems are known as exhaust systems. Usually, a clamshell type exhaust manifold system or, for example, two exhaust gas passages (dual) between cylinders whose ignition order is not continuous.
In summary, a dual-type exhaust manifold system is adopted, which uses exhaust inertia or exhaust pulsation to improve the full-open performance and obtain high output.

[0005]

By the way, when performing the above-mentioned two-stage combustion, the reaction between the residual O ₂ and the unburned HC or CO proceeds most immediately after the exhaust, that is, in the exhaust system in the vicinity of the exhaust valve, and the exhaust gas is most advanced. Experiments have confirmed that the temperature rises rapidly near the exhaust valve. However, if the exhaust temperature rises rapidly in the vicinity of the exhaust valve in this way, exhaust gas purification is promoted, but usually there is a certain distance to reach the catalytic converter. There is a problem that heat is radiated through the manifold and the exhaust pipe, the temperature of the catalytic converter is not sufficiently raised, and the catalyst cannot be activated early. In particular, when the above-mentioned dual type exhaust manifold system is adopted, there is an advantage that the fully open performance can be improved and a high output can be obtained, while the provision of the dual portion increases the heat radiation area and the heat capacity, and As the amount of heat increases, the above problem becomes remarkable.

The present invention has been made in order to solve such problems, and an object thereof is to promote exhaust gas purification at low temperature and early activation of a catalyst while improving the engine full opening performance. An object of the present invention is to provide a feasible in-cylinder injection type spark ignition type multi-cylinder engine exhaust purification device.

[0007]

In order to achieve the above-mentioned object, in the invention of claim 1, a compression stroke injection mode in which fuel is injected in a compression stroke and fuel is injected in a compression stroke and an expansion stroke or an exhaust stroke. In an exhaust gas purification device for a cylinder injection type multi-cylinder engine having a two-stage combustion mode, an exhaust gas purification catalyst provided midway in the exhaust pipe of the multi-cylinder engine, and a cylinder in which the ignition order of the multi-cylinder engine is not continuous A plurality of cylinder groups that are paired with each other, a plurality of exhaust gas passages that individually guide the exhaust gas discharged from each of the cylinder groups directly upstream of the exhaust purification catalyst, and the multi-cylinder engine is in cold start. When it is determined that the cold start is determined by the cold start determination means for determining that, and the cold start determination means, some cylinder groups are controlled in the two-stage combustion mode, and It is characterized in that a control means for controlling the remaining cylinders set in the compression stroke injection mode.

That is, a dual-type exhaust manifold system in which a plurality of exhaust gas passages (for example, two (dual)) are grouped into a cylinder injection type spark ignition type multi-cylinder engine and cylinders whose ignition order is not continuous is combined is adopted. In this case, the exhaust gas from some of the cylinder groups and the exhaust gas from the other of the remaining cylinder groups are guided to a position immediately upstream of the exhaust gas purification catalyst in a state of being separated by a plurality of exhaust gas passages. Two-stage combustion is performed in the cylinder set, and only the compression stroke injection is performed in the other cylinder sets without performing the two-stage combustion.

Therefore, at the time of cold start, high-concentration unburned HC or CO discharged from some cylinder groups and high-concentration O ₂ discharged from the remaining cylinder groups pass through a plurality of exhaust gas passages. Are independently supplied immediately upstream of the exhaust purification catalyst, O ₂ and unburned HC or CO react with each other immediately upstream of the exhaust purification catalyst, and the exhaust gas temperature rapidly rises. The high-temperature exhaust gas containing heat is supplied to the exhaust purification catalyst with almost no heat radiation.

As a result, while adopting the dual type exhaust manifold system to improve the engine full-open performance, at the time of cold start, exhaust purification is promoted and the temperature of the exhaust purification catalyst is raised efficiently and promptly. It becomes possible to achieve early activation. Further, the invention of claim 2 is characterized in that the compression stroke injection mode and the two-stage combustion mode are controlled so that the output per combustion is substantially equal.

That is, in the two-stage combustion mode, the fuel is additionally injected in the expansion stroke or the exhaust stroke, but the additional injected fuel does not contribute to the expansion work, that is, the engine output, while the two-stage combustion is performed. In the mode as well, since the fuel is injected in the compression stroke as in the case of the compression stroke injection mode, it is possible to control the fuel so that the output per combustion is substantially equal.

Therefore, even when the compression stroke injection mode and the two-stage combustion mode are simultaneously performed at the cold start, the output torque generated for each cylinder is made substantially equal to keep the engine rotation speed substantially constant. It is possible to prevent deterioration of drivability. Further, in the invention of claim 3, the plurality of exhaust gas passages are formed by an inner pipe and an outer pipe which are arranged substantially concentrically, and the exhaust gas containing high concentration carbon monoxide discharged from a part of the cylinder set. Is introduced into the inner pipe, and the exhaust gas containing high-concentration O ₂ discharged from the other remaining cylinder groups is introduced into the space between the outer pipe and the inner pipe.

Therefore, the exhaust gas containing a high concentration of unburned HC or CO discharged from some of the cylinder groups is maintained at a high temperature by flowing through the inner pipe having a high heat insulation effect, and is discharged from the other remaining cylinder groups. Exhaust gas containing a high concentration of O ₂ flows in the outer tube having a large surface area, whereby the exhaust gas is cooled well and the reaction of O ₂ is suppressed. As a result, the reaction rapidly progresses immediately upstream of the exhaust purification catalyst in the presence of high temperature and sufficient O _2, and the temperature of the exhaust purification catalyst rises even earlier and the exhaust purification catalyst is activated earlier.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. First, the first embodiment will be described. Referring to FIG. 1, there is shown a schematic configuration diagram of an exhaust gas purification apparatus for a cylinder injection type spark ignition type multi-cylinder engine mounted on a vehicle according to the present invention. Hereinafter, the configuration of the exhaust gas purification apparatus will be described. .

A cylinder injection type spark ignition type multi-cylinder engine (hereinafter, simply referred to as an engine) 1 is, for example, a fuel injection in an intake stroke by switching a fuel injection mode to an intake stroke injection mode or a compression stroke injection mode ( An in-cylinder injection spark ignition type 4-cylinder gasoline engine capable of performing fuel injection (compression stroke injection) in the compression stroke together with intake stroke injection is adopted. This in-cylinder injection type engine 1 facilitates operation at a stoichiometric air-fuel ratio and operation at a rich air-fuel ratio (rich air-fuel ratio operation) by switching the fuel injection mode and controlling the air-fuel ratio. It is possible to realize lean air-fuel ratio operation (lean air-fuel ratio operation). Further, in the in-cylinder injection type engine 1, it is also possible to select a two-stage combustion mode in which fuel injection in the compression stroke and fuel injection (two-stage combustion) after the expansion stroke are performed.

As shown in the figure, the cylinder head 2 of the engine 1 is provided with an electromagnetic fuel injection valve 6 together with a spark plug 4 for each cylinder, whereby the fuel is directly injected into the combustion chamber. It is possible. An ignition coil 8 that outputs a high voltage is connected to the spark plug 4. A fuel supply device (not shown) having a fuel tank is connected to the fuel injection valve 6 via a fuel pipe 7. More specifically, the fuel supply device is provided with a low-pressure fuel pump and a high-pressure fuel pump, which supplies the fuel in the fuel tank to the fuel injection valve 6 at a low fuel pressure or a high fuel pressure. Can be injected from the fuel injection valve 6 toward the combustion chamber at a desired fuel pressure.

An intake port is formed in the cylinder head 2 in a substantially upright direction for each cylinder, and one end of an intake manifold 10 is connected so as to communicate with each intake port. The intake manifold 10 is provided with an electromagnetic throttle valve 14 that adjusts the intake air amount. Further, the cylinder head 2 is formed with an exhaust port in a substantially horizontal direction for each cylinder, and one end of an exhaust manifold 12 is connected so as to communicate with each exhaust port. As the exhaust manifold 12, here, a dual type exhaust manifold system as shown in FIG. 2 is adopted.

As shown in the figure, the exhaust manifold 12 consisting of a dual type exhaust manifold system has a cylinder set of # 2 cylinders and # 3 cylinders in which the ignition order is not continuous (some cylinder sets are referred to as # 2 below. , # 3 cylinder)
Exhaust gas from the # 1 cylinder and exhaust gas from the # 4 cylinder group (the other remaining cylinder groups, hereinafter referred to as # 1 and # 4 cylinders) merge to form two pipe lines (dual). Multiple exhaust gas passages) (when the combustion order is # 1 → # 3 → # 4 → # 2). Thus, when the exhaust manifold 12 is composed of the dual type exhaust manifold system, it is possible to reduce exhaust interference and obtain a large effect of exhaust inertia or exhaust pulsation. As a result, when the engine 1 is warm, the engine 1
It is possible to obtain a high output by improving the full-open performance of the.

An exhaust pipe 2 is provided at the other end of the exhaust manifold 12.
0 is connected, and a three-way catalyst (exhaust gas purification catalyst) 30, for example, is interposed in the exhaust pipe 20 as a catalytic converter. As shown in FIG. 2, the exhaust pipe 20 corresponds to a dual type exhaust manifold system. The exhaust pipe 20 has a branch pipe 20a in which the exhaust gas from the # 1 and # 4 cylinders flows from the upstream portion and from the # 2 and # 3 cylinders. It is separated into a branch pipe 20b through which exhaust gas flows, and the branch pipe 20a and the branch pipe 2 are separated.
0b is formed by a bifurcated pipe line (a plurality of exhaust gas passages) that joins immediately upstream of the three-way catalyst 30. That is, in the exhaust pipe 20, exhaust gas from the # 1 and # 4 cylinders and # 2 and # 4
Exhaust gas from the three cylinders is branched pipe 20a and branch pipe 20b
After each of them independently flows to immediately upstream of the three-way catalyst 30, they are mixed immediately upstream of the three-way catalyst 30.

As shown in the figure, an O ₂ sensor 22 is provided in the exhaust pipe 20 immediately upstream of the three-way catalyst 30, and the three-way catalyst 30 has a high temperature sensor 32 for detecting the catalyst temperature. Is provided. The ECU 60 is an input / output device,
A storage device, a central processing unit (CPU), a timer counter, and the like are provided, and the ECU 60 performs comprehensive control of the exhaust gas purification device including the engine 1.

Various sensors such as the O ₂ sensor 22 and the high temperature sensor 32 are connected to the input side of the ECU 60, and the detection information from these sensors is input. Then, one of the fuel injection modes such as the intake stroke injection mode, the compression stroke injection mode, and the two-stage combustion mode is selected based on these various detection information. On the other hand, various output devices such as the fuel injection valve 6, the ignition coil 8 and the throttle valve 14 are connected to the output side of the ECU 60, and these various output devices include the selected fuel injection mode and various sensors. Signals such as the fuel injection amount, the fuel injection timing, and the ignition timing, which are calculated according to the detection information from the class, are output, respectively, whereby the fuel injection valve 6 injects an appropriate amount of fuel at an appropriate timing, and the ignition is performed. Spark ignition is performed by the plug 4 at an appropriate timing.

The operation of the exhaust gas purifying apparatus according to the present invention constructed as above will be described below. Referring to FIG. 3, a control routine of the cold state control according to the present invention is shown in a flow chart, which will be described below based on the flow chart. In step S10, it is determined whether or not the exhaust emission control device is in a cold state. Here, for example, the high temperature sensor 3
Based on the temperature information from 2, it is determined whether or not the catalyst temperature TCAT is equal to or higher than a predetermined temperature T0 (for example, the temperature corresponding to the semi-active state). Instead of determining the catalyst temperature, the ON state of the ignition switch may be detected to determine whether or not the engine 1 has just started.
It may be possible to determine whether or not the cooling water temperature Tw of the engine 1 or the oil temperature Toil is equal to or higher than a predetermined temperature (cooling start time determination means). When the determination result is false (No) and it is determined that the exhaust emission control device is not in the cold state but in the warm state, the process proceeds to step S18.

In step S18, normal control is executed for all cylinders. That is, an appropriate fuel injection mode is selected according to the operating state of the engine 1, and the same control is performed in all cylinders based on information from various sensors. on the other hand,
When the determination result of step S10 is true (Yes) and it is determined that the exhaust emission control device is in the cold state, step S
12, the compression stroke injection mode is selected for the # 1 and # 4 cylinders, and the compression stroke injection is performed with a lean air-fuel ratio.

Further, in step S14, # 2, # 3
The two-stage combustion mode is selected in the cylinder to perform the two-stage combustion. In other words, for the # 2 and # 3 cylinders, fuel injection for main combustion (main injection) is performed at a lean air-fuel ratio in the compression stroke, and additional fuel injection (sub-injection) is performed after the expansion stroke (expansion stroke or exhaust stroke). )I do. At this time, #
Air-fuel ratio of compression stroke injection in cylinders 1 and 4 and # 2 and #
The lean air-fuel ratio is substantially the same as the air-fuel ratio of the compression stroke injection in the three cylinders, and the overall air-fuel ratio including the additional injection amount in the # 2 and # 3 cylinders is set to 16 for example. At this time, the overall air-fuel ratio is feedback-controlled based on the output information of the O ₂ sensor 22.

When the compression stroke injection is performed in the # 1 and # 4 cylinders and the two-stage combustion is performed in the # 2 and # 3 cylinders as described above, the exhaust gas discharged from the # 2 and # 3 cylinders contains Due to the additional injection that does not contribute to the expansion work, a high concentration of unburned HC or CO is contained, while the exhaust gas discharged from the # 1 and # 4 cylinders contains a high concentration of O ₂ . That is, the exhaust gas containing high concentration unburned HC or CO flows through the branch pipe 20b, and the exhaust gas containing high concentration O ₂ flows through the branch pipe 20a.

Further, a high concentration of unburned H 2 is contained in the branch pipe 20b.
Since some residual O ₂ is contained together with C or CO, the exhaust gas in the branch pipe 20b is heated to some extent by the reaction of a part of the unburned HC or CO with the residual O ₂ , while the branch pipe 20a is Since it is cooled by the running wind of the vehicle, the reaction of O ₂ is suppressed in the branch pipe 20a and a high concentration of O ₂ is retained.

Therefore, in practice, the exhaust gas discharged from the # 2 and # 3 cylinders and flowing through the branch pipe 20b contains high-temperature and high-concentration unburned HC or CO, while # 1, # 4.
In the exhaust gas discharged from the cylinder and flowing through the branch pipe 20a,
It will contain a low temperature and high concentration of O ₂ . And
As described above, since the branch pipe 20a and the branch pipe 20b are configured so as to join immediately upstream of the three-way catalyst 30, the high temperature and high concentration unburned HC or CO flowing alone in the branch pipe 20b is included. The exhaust gas and the exhaust gas containing O ₂ at a low temperature and a high concentration, which has flowed alone through the branch pipe 20 a, are mixed immediately upstream of the three-way catalyst 30. As a result, the three-way catalyst 3
Immediately upstream of 0, the reaction between unburned HC or CO and O ₂ proceeds, and the exhaust gas temperature rises rapidly.

When the reaction proceeds immediately upstream of the three-way catalyst 30 and the exhaust gas temperature rises rapidly in this manner, exhaust gas purification is promoted by a synergistic effect, and the high temperature exhaust gas radiates the exhaust heat. Soon after, the three-way catalyst 30 is immediately reached, the temperature of the three-way catalyst 30 rapidly rises, and the three-way catalyst 30
The early activation of is promoted. Therefore, even when the three-way catalyst 30 is arranged under the floor of the vehicle or the like, it is possible to quickly raise the temperature, and it is necessary to improve the heat resistance as compared with the case where the catalyst is arranged immediately below the exhaust manifold. It can be reduced and the exhaust gas performance can be improved by rapidly raising the temperature in the cold state.

As described above, the air-fuel ratio of the compression stroke injection in the # 1 and # 4 cylinders and the air-fuel ratio of the compression stroke injection in the # 2 and # 3 cylinders are substantially the same lean air-fuel ratio. Even if the stroke injection mode and the two-stage combustion mode are simultaneously performed, the combustion stability is ensured, and the output torque (output per combustion) of the engine 1 generated for each cylinder is made substantially equal to the engine rotation speed Ne. It can be maintained at a substantially constant value, and deterioration of drivability can be prevented.

In step S16, based on the temperature information from the high temperature sensor 32, it is determined whether or not the catalyst temperature TCAT is equal to or higher than a predetermined temperature T1 (for example, 300 ° C.). That is,
Here, it is determined whether or not the three-way catalyst 30 has been sufficiently activated. When the determination result is false (No) and it is determined that the three-way catalyst 30 is not yet sufficiently activated, steps S12 and S14 are repeatedly executed to continue the catalyst temperature increase. On the other hand, when the determination result is true (Yes) and the catalyst temperature TCAT is determined to be equal to or higher than the predetermined temperature T1, the process proceeds to step S18 described above, and the normal control is performed for all the cylinders.

That is, if it is determined that the three-way catalyst 30 has been fully activated, the objective is achieved and no longer # 1.
It is not necessary to perform different fuel injection modes for the # 4 cylinder and the # 2 and # 3 cylinders, and an appropriate fuel injection mode is selected according to the operating state of the engine 1 and information from various sensors is displayed. Based on this, the same control is performed in all cylinders. next,
A second embodiment will be described.

In the second embodiment, the description of the common parts with the first embodiment will be omitted, and only the structure and operation different from those of the first embodiment will be described. In the second embodiment, as shown in FIGS. 4 (a) and 4 (b), the exhaust pipe 20 'is replaced by an exhaust pipe 20' in contrast to the first embodiment, and the exhaust pipe 20 'is not a bifurcated conduit. A double pipe line (a plurality of exhaust gas passages) including an outer pipe 20′a and an inner pipe 20′b having a diameter slightly smaller than that of the outer pipe 20′a up to immediately upstream of the three-way catalyst 30.
It consists of. Specifically, the exhaust pipe 20 'is the outer pipe 2
The exhaust gas from the # 1 and # 4 cylinders independently flows through the passage between the 0'a and the inner pipe 20'b to just upstream of the three-way catalyst 30, and the # 2 and # 3 cylinders inside the inner pipe 20'b. The exhaust gas from the exhaust gas is configured to flow independently upstream of the three-way catalyst 30. 4 (b) shows a cross section taken along the line AA of FIG. 4 (a), and reference numeral 21 'denotes an outer pipe 20'a and a constant gap (passage width) around the inner pipe 20'b. It is a support member that supports the exhaust gas flow substantially concentrically so as not to interfere with the exhaust gas flow.

In the exhaust gas purifying apparatus according to the second embodiment thus constructed, the control is performed based on the control routine of FIG. 3 as in the case of the first embodiment, but the compression is performed in the # 1 and # 4 cylinders. When stroke injection is performed and two-stage combustion is performed in the # 2 and # 3 cylinders, the outer pipe 20'a and the inner pipe 2
Exhaust gas containing a high concentration of O ₂ flows through the passage between 0'b and 0'b, and exhaust gas containing a high concentration of unburned HC or CO flows within the inner pipe 20'b.

At this time, the inner tube 20'b is replaced by the outer tube 2 '.
Since it is surrounded by 0'a, the exhaust gas containing a high concentration of unburned HC or CO flowing in the inner pipe 20'b does not directly exchange heat with the outside air, and is kept at a good high temperature. It is sent immediately upstream of the catalyst 30. On the other hand, the exhaust gas containing a high concentration of O ₂ flowing through the passage between the outer pipe 20′a and the inner pipe 20′b is well cooled by the traveling wind of the vehicle because the surface area of the outer pipe 20′a is large. Thus, the reaction of O ₂ is further suppressed, and the high concentration of O ₂ is sent to the upstream of the three-way catalyst 30 while being well maintained.

Therefore, in the second embodiment, # 2 and # 3 are used.
The exhaust gas discharged from the cylinders and flowing in the inner pipe 20'b contains unburned HC or CO at a higher temperature and a higher concentration, while the exhaust pipes 20 'are discharged from the # 1 and # 4 cylinders.
In the exhaust gas flowing through the passage between a and the inner pipe 20′b,
As the temperature becomes lower, a high concentration of O ₂ will be contained.

As a result, the exhaust gas containing unburned HC or CO flowing in the inner pipe 20'b, the outer pipe 20'a and the inner pipe 2
When the exhaust gas containing O ₂ flowing through the passage between the three-way catalyst 0'b and 0'b is mixed immediately upstream of the three-way catalyst 30, the reaction is further performed immediately upstream of the three-way catalyst 30 in the presence of high temperature and sufficient O _2. Occurs, the exhaust gas temperature rises extremely rapidly, and the temperature of the three-way catalyst 30 rises even more rapidly.
Early activation of 0 is achieved.

Although the description is finished above, the embodiment of the present invention is not limited to the above embodiment. For example, in the above embodiment, the compression stroke injection is performed in the # 1 and # 4 cylinders,
Although the two-stage combustion is performed in the # 2 and # 3 cylinders, the cylinder groups for performing the compression stroke injection and the two-stage combustion may be alternately switched for each predetermined stroke or each predetermined rotation speed. With this configuration, the cylinders that perform the two-stage combustion can be made uniform and even, and the spark plug 4 can be prevented from being contaminated.

Further, in the above embodiment, the cylinder injection type spark ignition type four cylinder gasoline engine is adopted, but the engine 1 may be a cylinder injection type spark ignition type V6 cylinder gasoline engine. In this case, the exhaust manifold system is grouped into banks to form a dual type exhaust manifold system, one bank (some cylinder groups) performs two-stage combustion, and the other bank (other cylinder groups) performs compression stroke injection. Should be done.

Further, in the above embodiment, as soon as it is determined that the exhaust purification system is in the cold state based on the determination result of step S10 in FIG. 3, the compression stroke injection is performed in the cylinders # 1 and # 4. Although two-stage combustion is performed in the # 2 and # 3 cylinders, for example, when the temperature of the exhaust system is extremely low, such as during cold start, the two-stage combustion is performed in all cylinders for a predetermined period. It is also possible to warm up the portion immediately upstream of the three-way catalyst 30 to some extent, then perform compression stroke injection in the # 1 and # 4 cylinders, and perform two-stage combustion in the # 2 and # 3 cylinders.

Further, in the above embodiment, the three-way catalyst is used as the exhaust purification catalyst, but instead of the three-way catalyst, for example, an oxidation catalyst, a reduction catalyst, a lean NOx catalyst, an HC trap or the like may be used. . That is, the present invention can be applied to purification means such as a catalyst that needs to be activated or heated early in a cold state.

[0041]

As described in detail above, according to the exhaust gas purifying apparatus for a cylinder injection type spark ignition type multi-cylinder engine of claim 1 of the present invention, the exhaust gas passage is formed by grouping cylinders whose ignition orders are not continuous. A dual type exhaust manifold system is adopted in which a plurality of (for example, two (dual)) are combined, and exhaust gas from one cylinder group and exhaust gas from the other remaining cylinder groups are separated by a plurality of exhaust gas passages. In this state, the exhaust gas is guided directly upstream of the exhaust purification catalyst, and during cold start, some cylinder groups perform two-stage combustion, while the remaining cylinder groups do not perform two-stage combustion but only compression stroke injection. since so as to implement, while improving full throttle performance by adopting a dual-type exhaust manifold system, at the time of cold-start, O ₂ and unburned HC
Alternatively, CO can be made to react immediately upstream of the exhaust purification catalyst to raise the temperature of the exhaust purification catalyst efficiently and promptly, and the exhaust purification catalyst can be promoted and the exhaust purification catalyst can be activated early.

According to the exhaust gas purifying apparatus for a cylinder injection type spark ignition type multi-cylinder engine of claim 2, the compression stroke injection mode and the two-stage combustion mode have substantially the same output per combustion. Since it is controlled, even if the compression stroke injection mode and the two-stage combustion mode are simultaneously performed at the cold start, the output torque generated for each cylinder is made substantially equal and the engine rotation speed is kept substantially constant. It is possible to prevent deterioration of drivability.

According to the exhaust gas purifying apparatus for a cylinder injection type spark ignition type multi-cylinder engine of claim 3, a plurality of exhaust gas passages are formed by an inner pipe and an outer pipe which are arranged substantially concentrically, and a part of them is formed. The exhaust gas containing a high concentration of unburned HC or CO discharged from the cylinder group is flown into the inner pipe having a high adiabatic effect, and the exhaust gas containing a high concentration of O ₂ discharged from the remaining cylinder group is discharged to a large surface area. Since it is made to flow in the pipe, the exhaust gas containing high concentration unburned HC or CO can be maintained at a high temperature and the exhaust gas containing high concentration O ₂ can be cooled well to suppress the reaction of O ₂ . The reaction immediately upstream of the exhaust purification catalyst can be made to progress rapidly to raise the temperature of the exhaust purification catalyst much earlier.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an exhaust emission control device for a cylinder injection type spark ignition multi-cylinder engine according to the present invention which is mounted on a vehicle.

FIG. 2 is a diagram showing a dual type exhaust manifold system and an exhaust pipe according to the first embodiment.

FIG. 3 is a flowchart showing a control routine of cold state control according to the present invention.

FIG. 4 is a view showing a dual type exhaust manifold system and an exhaust pipe according to a second embodiment.

[Explanation of symbols]

1 engine 6 Fuel injection valve 12 Exhaust manifold 20, 20 'exhaust pipe 20a, 20b Branch pipe 20'a outer tube 20'b inner tube 30 three way catalyst 32 High temperature sensor 60 ECU (electronic control unit)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/02 330 F02D 41/02 330A 330H 41/34 41/34 H 41/36 41/36 AB ( 72) Inventor Tetsuo Chamoto 5-3-33, Shiba, Minato-ku, Tokyo Within Mitsubishi Motors Corporation (72) Inventor Kiyoshi Hatano 5-33-3, Shiba, Minato-ku, Tokyo Within Mitsubishi Motors Corporation (72) ) Inventor Katsuyuki Maeda 16 580 Horikawa-cho, Sachi-ku, Kawasaki-shi, Kanagawa Sanryo Engineering Co., Ltd. (72) Inventor Seiji Shioda 580 Horikawa-cho, Sachi-ku, Kawasaki, Kanagawa Prefecture (Reference) 3G004 AA01 AA08 BA03 BA06 DA02 DA14 DA21 DA25 EA05 FA04 3G091 AA02 AA17 AA24 AA28 AA29 AB02 AB03 AB05 AB10 BA03 BA14 BA15 BA19 CB02 CB03 CB05 CB06 CB07 DA01 DA02 DB10 DC01 EA16 EA17 EA18 EA26 EA34 FA02 FA04 FA12 FA13 FB02 FB10 FB11 FB12 FC04 FC07 HA36 HB02 3G301 HA01 HA04 HA18 JA01 JA26 KA02 KA05 LB04 MA11 MA19 MA23 MA26 MA16 NA08 PD02Z PD12 PD16

Claims (3)

[Claims] 1. An exhaust of a cylinder injection type spark ignition multi-cylinder engine having a compression stroke injection mode for injecting fuel in a compression stroke and a two-stage combustion mode for injecting fuel in a compression stroke and an expansion stroke or an exhaust stroke. In the purification device, an exhaust purification catalyst provided in the middle of an exhaust pipe of the multi-cylinder engine, a plurality of cylinder groups in which cylinders in which the ignition order of the multi-cylinder engine is not continuous are grouped, and from each of the cylinder groups A plurality of exhaust gas passages that individually guide exhausted exhaust gas directly upstream of the exhaust purification catalyst; a cold start determination means for determining that the multi-cylinder engine is in cold start; When it is determined by the determining means that the engine is in the cold start state, some cylinder groups are controlled in the two-stage combustion mode, and other cylinder groups are controlled in the compression stroke injection mode. Cylinder injection type spark-ignition multi-cylinder engine exhaust purification device, characterized in that it comprises a stage, a. 2. The in-cylinder injection type spark ignition according to claim 1, wherein the compression stroke injection mode and the two-stage combustion mode are controlled so that the output per combustion is substantially equal. Exhaust purification device for multi-cylinder engine. 3. The plurality of exhaust gas passages are formed by an inner pipe and an outer pipe that are arranged substantially concentrically, and the exhaust gas containing a high concentration of carbon monoxide discharged from a part of a set of cylinders is the inner pipe. The in-cylinder according to claim 1 or 2, wherein exhaust gas containing high-concentration oxygen that is introduced into the inside and is discharged from the other remaining cylinder groups is introduced into the space between the outer pipe and the inner pipe. Exhaust gas purification device for injection-type spark ignition multi-cylinder engine.