JP4371227B2 - Exhaust gas purification device for multi-cylinder engine - Google Patents

Description

  The present invention relates to an exhaust purification device for a multi-cylinder engine, and more particularly to an exhaust purification device for a multi-cylinder engine provided with an exhaust control valve for closing an exhaust pipe downstream of a catalyst.

  An exhaust control valve is provided on the downstream side of the catalyst in the engine exhaust system, and the exhaust control valve is closed during engine cold start to suppress the discharge of unburned components such as HC and CO, and to the exhaust system due to an increase in exhaust pressure A technology has been proposed in which the exhausted exhaust gas is returned to the cylinder of the engine and re-combusted at the next combustion, or the catalyst is heated up and activated at an early stage by raising the exhaust gas temperature (for example, Patent Document 1). , 2).

In the technology disclosed in Patent Document 1, some cylinders of a multi-cylinder engine are deactivated to increase the amount of oxygen in exhaust gas, while the air-fuel ratio of the remaining cylinders is enriched to increase the content of unburned matter. By closing the exhaust control valve, the reaction between these oxygen and unburned substances is promoted, and the catalyst is activated early by increasing the exhaust temperature.
In the technique disclosed in Patent Document 2, each cylinder of a multi-cylinder diesel engine is divided into a plurality of cylinder groups, and an exhaust shutter valve is provided in an exhaust pipe for each cylinder group. When the temperature decreases, the shutter valve is closed to increase the pressure of the exhaust gas, and the fuel injection amount is increased by increasing the work amount in the compression stroke, thereby increasing the temperature.

However, in these exhaust purification devices, exhaust gas cannot be discharged when the exhaust control valve or the shutter valve is fixed, and therefore, there is a problem that the engine is unable to start due to engine stall. There is also a countermeasure focusing on such problems (for example, refer to Patent Document 3). In the technique of Patent Document 3, a bypass passage is formed so as to bypass the shutter valve provided in the exhaust pipe of the engine. A bypass valve (relief valve) is provided in the bypass passage, and when the exhaust pressure rises to a set value or more due to the fixed shutter valve, the bypass valve is opened and exhaust gas is discharged through the bypass passage.
JP 2002-221029 A JP 59-77047 A Japanese Patent Laid-Open No. 05-231195

However, even in the technique disclosed in Patent Document 3 described above, when the shutter valve and the bypass valve are fixed simultaneously, the same result as in the techniques of Patent Documents 1 and 2 can be obtained, and the vehicle can be caused to run because the engine cannot be started. For example, there is a problem that it is impossible to take a countermeasure such as a driver self-propelled at a repair shop.
The present invention has been made in order to solve such problems, and the object of the present invention is to prevent the engine from starting even if the exhaust pressure increasing valve provided in the exhaust pipe of the engine is fixed. It is an object of the present invention to provide an exhaust emission control device for a multi-cylinder engine that can prevent a situation of falling into a cylinder.

  In order to achieve the above object, the invention of claim 1 is directed to an exhaust emission control device for a multi-cylinder engine in which the cylinders of a multi-cylinder engine are divided into two cylinder groups and each cylinder group has an exhaust pipe. A first exhaust pipe, a second exhaust pipe for the second cylinder group, a first catalyst provided in the first exhaust pipe, a second catalyst provided in the second exhaust pipe, and the first catalyst An exhaust control valve that is provided downstream and closes the first exhaust pipe at the time of engine cold start, a failure detection means that detects closed adhering of the exhaust control valve, and a first combustion state that operates at least only the first cylinder group And a combustion control means for controlling to switch between the second combustion state in which only the second cylinder group is operated, the exhaust control valve is closed at the time of engine cold start, and the first combustion state is set by the combustion control means. On the other hand, the first combustion state at engine cold start When stuck closed the exhaust control valve is detected by the failure detection means when there are those switching to the second combustion state by the combustion control means.

Therefore, at the time of engine cold start, the engine is operated in the first combustion state with the exhaust control valve closed, and the exhaust gas discharged from the first cylinder group flows through the first exhaust pipe and passes through the first catalyst. At this time, reduction of unburned components and temperature increase of the catalyst are achieved by closing the exhaust control valve.
On the other hand, when the exhaust control valve is closed, the exhaust pressure in the first exhaust pipe rises abnormally due to the exhaust gas that has lost its destination. Therefore, even if cranking is continued, the first cylinder group is prevented from being exhausted and operates. The engine is switched to the second combustion state by the combustion control means at this time. Even when the exhaust control valve is fixed, the second exhaust pipe can circulate the exhaust gas without any influence. Therefore, the second cylinder group operates without trouble and the engine starts.

According to a second aspect of the present invention, in the first aspect of the present invention, the first exhaust pipe and the second exhaust pipe are communicated with each other in a communication passage that is provided in the communication passage, and in the first exhaust pipe. And an exhaust switching valve that opens the communication passage when the pressure becomes equal to or higher than a predetermined pressure, and the failure detection means detects the closed adhering of the exhaust switching valve together with the closing adhering of the exhaust control valve.
Therefore, when the pressure in the first exhaust pipe becomes a predetermined value or more by closing the exhaust control valve, the exhaust switching valve is opened, and the exhaust gas flowing through the first exhaust pipe passes through the communication path to the second exhaust pipe side. However, when the exhaust gas switching valve is closed and fixed, an abnormal increase in the exhaust pressure is unavoidable. . Here, if the failure detection means detects that the exhaust control valve is closed and stuck together, the engine is switched from the first combustion state to the second combustion state based on this detection. Even in this case, it becomes possible to avoid the inability to start the engine.

The invention of claim 3 further comprises engine rotation speed detection means for detecting the engine rotation speed according to claim 1, wherein the failure detection means is detected by the engine rotation speed detection means even if a predetermined period has elapsed after starting. It is detected that the exhaust control valve is closed and fixed when the engine rotational speed is equal to or lower than the predetermined rotational speed.
Accordingly, when the engine speed is equal to or lower than the predetermined rotation speed even after a predetermined period has elapsed after starting in the first combustion state, the failure detection means detects that the exhaust control valve is closed and switches to the second combustion state. Since the sticking of the exhaust control valve is detected based on the engine rotational speed in this way, the configuration is simplified without the need for an opening degree sensor for detecting the opening degree of the exhaust control valve, and the opening degree Since the sensor is provided, the type of the exhaust control valve is not limited.

According to a fourth aspect of the present invention, in the third aspect, the predetermined period is set longer as the engine temperature is lower.
Therefore, the lower the engine temperature, the worse the engine startability and the more time it takes to start, but the predetermined period is set to a longer time accordingly. Therefore, the engine start determination reflecting the current engine startability, and hence accurate It is possible to detect sticking of the exhaust control valve.

According to a fifth aspect of the present invention, in the first to fourth aspects, the first and second cylinder groups are divided for each cylinder in which combustion does not continue.
Therefore, since the first cylinder group and the second cylinder group operate without continuous combustion, engine output fluctuation is reduced.

  As described above, according to the exhaust purification system for a multi-cylinder engine of the first aspect of the invention, when the engine is cold started, the first cylinder group is operated in the first combustion state and the exhaust control valve is closed. While reducing the unburned components and increasing the temperature of the catalyst, the exhaust control valve is switched to the second combustion state that is not affected by the exhaust control valve when the exhaust control valve is closed and closed. Even if it exists, an engine can be started by operation | movement of a 2nd cylinder group, and appropriate countermeasures, such as a driver | operator self-propelling to a repair shop by this, can be implemented.

According to the exhaust emission control device for a multi-cylinder engine of the second aspect of the invention, in addition to the first aspect, in addition to detecting that the exhaust control valve is closed and stuck, the exhaust switch valve is also detected. Even in this case, the engine can be started.
According to the exhaust purification device for a multi-cylinder engine of the invention of claim 3, in addition to claim 1, since the sticking of the exhaust control valve is detected based on the engine speed, the opening degree of the exhaust control valve is detected. Therefore, the configuration of the exhaust control valve can be arbitrarily set without considering the installation of the opening sensor.

According to an exhaust emission control device for a multi-cylinder engine of a fourth aspect of the invention, in addition to the third aspect, since the predetermined period is set to be longer as the engine temperature is lower, the engine start determination reflecting the current engine startability As a result, accurate detection of the exhaust control valve sticking can be realized.
According to the exhaust emission control device for a multi-cylinder engine of the fifth aspect of the invention, in addition to the first to fourth aspects, each cylinder of the first cylinder group and the second cylinder group operates without causing continuous combustion. Thus, stable vehicle running performance can be obtained by reducing engine output fluctuation.

[First embodiment]
Hereinafter, a first embodiment of an exhaust emission control device for a multi-cylinder engine embodying the present invention will be described.
FIG. 1 is an overall configuration diagram showing an exhaust emission control device for a multi-cylinder engine according to a first embodiment. The engine of this embodiment is configured as an in-line four-cylinder engine whose ignition order is set to # 1- # 3- # 4- # 2. The intake side of the engine 1 has a general configuration, and intake air introduced from an air cleaner (not shown) is diverted to each cylinder by an intake manifold 2 after passing through an air flow meter and a throttle valve, and is provided at an intake port of each cylinder. Fuel is injected from the fuel injection valve and introduced into the cylinder.

  On the other hand, the exhaust side of the engine 1 is divided into two types of cylinder groups in which cylinders in which combustion does not continue are combined, and independent exhaust pipes 3 and 4 are provided for each cylinder group. More specifically, the cylinders # 2 and # 3 are set as the first cylinder group and the cylinders # 1 and # 4 are set as the second cylinder group as cylinders in which combustion does not continue. The exhaust ports of the # 2 and # 3 cylinders are joined by the first exhaust manifold 3a and connected to the common first exhaust pipe 3. Similarly, the exhaust ports of the # 1 and # 4 cylinders are the second exhaust. The manifolds 4a join together and are connected to the common second exhaust pipe 4. The first and second exhaust pipes 3 and 4 are disposed substantially parallel to each other, and the downstream sides of the first and second exhaust pipes 3 and 4 are joined together and connected to a common downstream exhaust pipe 5.

  The first exhaust pipe 3 is provided with a first catalyst 6, and the exhaust gas discharged from the # 2 cylinder and the # 3 cylinder is purified by the first catalyst 6. A butterfly-type exhaust control valve 7 is provided at a position downstream of the first catalyst 6 in the first exhaust pipe 3, and the exhaust control valve 7 is driven by an exhaust control actuator 8 to pass through the first exhaust pipe 3. Can open and close. The first exhaust pipe 3 is connected to the second exhaust pipe 4 via a communication passage 9 at a position between the first catalyst 6 and the exhaust control valve 7, and a poppet relief valve 10 is connected to the communication passage 9. (Exhaust switching valve) is provided. The relief valve 10 is urged by a spring (not shown) to close the communication passage 9 from the second exhaust pipe 4 side, and always receives the pressure of the exhaust gas flowing through the first exhaust pipe 3 through the communication passage 9. When the exhaust pressure exceeds a set value, the communication passage 9 is opened. A second catalyst 11 is provided on the downstream side of the relief valve 10 in the second exhaust pipe 4, and the exhaust gas discharged from the # 1 cylinder and the # 4 cylinder is purified by the second catalyst 11.

  On the other hand, an ECU (electronic control unit) 21 having a storage device (ROM, RAM, etc.), a central processing unit (CPU), a timer counter, etc. provided for storage of control programs and control maps is installed in the vehicle. Yes. On the input side of the ECU 21, an ignition switch 22 provided in the driver's seat of the vehicle, a water temperature sensor 23 for detecting the coolant temperature THw, and a crank angle sensor 24 (engine) for outputting a pulse signal of a predetermined cycle as the engine 1 rotates. Various sensors such as a rotational speed detecting means) are connected, and on the output side of the ECU 21, the exhaust control actuator 8, a warning light 25 provided on an instrument panel of the vehicle, a fuel injection valve and an ignition plug of an engine (not shown) Etc. are connected.

The ECU 21 performs fuel injection control and ignition timing control based on detection information from various sensors to operate the engine 1 and operates only the # 2 and # 3 cylinders, and # 1 The second combustion state in which only the cylinder and the # 4 cylinder are operated can be arbitrarily switched (combustion control means).
Further, in the present embodiment, the ECU 21 controls the exhaust control valve 7 for the purpose of suppressing the emission of unburned components and early activation of the catalyst when the engine 1 is cold started, and at this time, the exhaust control valve 7 and the relief valve Limp home control that enables the minimum required engine operation is performed when 10 is closed and fixed simultaneously, and these controls will be described in detail below.

  The ECU 21 executes the cold start control routine shown in FIG. 2 at a predetermined control interval. Here, when the engine is stopped, the ECU 21 holds the exhaust control valve 7 in an open state. On the other hand, since the first exhaust pipe 3 is at atmospheric pressure when the engine is stopped, the relief valve 10 is moved by a spring. The valve is kept closed. First, in step S2, the ECU 21 determines whether or not the ignition switch 22 is turned on. In the subsequent step S4, the ECU 21 determines whether or not the cooling water temperature THw is lower than a preset cooling state determination value THw0. When the determination of No (No) is made in step S, the routine is once ended.

  When the determination of Yes (affirmative) is made in any of steps S2 and S4, that is, when it is determined that the engine 1 is in the cold start, the ECU 21 proceeds to step S6 and sets the exhaust control valve 7 to the valve closing side. Switch. In the subsequent step S8, fuel injection control and ignition timing control are executed for the # 2 and # 3 cylinders that are the first cylinder group, and further in step S10, the engine rotation obtained from the crank angle signal from the crank angle sensor 23 is executed. It is determined whether or not the speed Ne has reached the complete explosion determination value Ne0. As is well known, the complete explosion determination value Ne0 is an index for determining whether or not the engine start has been completed. Since the engine 1 at this time only operates for two cylinders, it is assumed that all cylinders are in operation. Instead of a typical complete explosion determination value Ne0, a slightly lower dedicated complete explosion determination value Ne0 may be applied.

  When the exhaust control valve 7 and the relief valve 10 are operating normally without sticking, the exhaust control valve 7 closed immediately after the exhaust gas from the # 2 and # 3 cylinders flows through the first catalyst 6. Therefore, when the exhaust pressure in the first exhaust pipe 3 exceeds the set value of the relief valve 10, the relief valve 10 is opened, and the exhaust gas escapes to the second exhaust pipe 4 side through the communication path 9. And is discharged to the outside through the second catalyst 11 and the downstream exhaust pipe 5.

  As a result, the exhaust control valve 7 is closed to suppress the discharge of unburned components such as HC and CO, and the exhaust gas exhausted from the # 2 and # 3 cylinders is returned to the cylinder due to the increase in exhaust pressure. By recombusting at the time of the next combustion, the emission of unburned components is further suppressed. On the other hand, the temperature of the first and second catalysts 6 and 11 is increased by the exhaust gas temperature and activated early. . In addition, since the operating cylinders are two cylinders, the fuel consumption during cold start, which consumes a large amount of fuel as the air-fuel ratio becomes rich, is halved, and the THC exhausted from the combustion chamber to the exhaust pipe is also halved. To do.

  Thus, when the desired exhaust gas flow based on the operation of the exhaust control valve 7 and the relief valve 10 is achieved at the cold start, the engine speed Ne is completed by the operation of the # 2 cylinder and the # 3 cylinder. In order to reach the explosion determination value Ne0, the ECU 21 determines Yes in step S10, and proceeds to step S12. In step S12, it is determined whether or not the fluctuation amount α of the engine rotational speed Ne is less than the allowable value α0. If the fluctuation amount α is less than the allowable value α0, that is, if it is estimated that the # 2 cylinder and the # 3 cylinder are combusting stably without causing misfire or the like, a Yes determination is made in step S12. Then, the process proceeds to step S14, and it is determined whether the required activation time T1 has elapsed from the complete explosion determination in step S10.

  The required activation time T1 is set in advance as the time required for the second catalyst 11 to be heated to the activation temperature (for example, 15 to 20 seconds), and the ECU 21 determines Yes in step S14 when the activation required time T1 has elapsed. A determination is made, the exhaust control valve 7 is opened in step S16, the fuel injection control and the ignition timing control are executed for all the cylinders in the subsequent step S18, and then the routine is terminated.

  As the exhaust control valve 7 is opened, the exhaust pressure in the first exhaust pipe 3 decreases, so that the relief valve 10 is closed and the engine 1 returns to normal control for operating all cylinders, and the # 2 cylinder And the exhaust gas from the # 3 cylinder flows through the first exhaust pipe 3 and the exhaust gas from the # 1 cylinder and # 4 cylinder flows through the second exhaust pipe 4 independently of each other. At this time, since the first catalyst 6 is activated, even if the exhaust pressure of the first exhaust pipe 3 is reduced due to the opening of the exhaust control valve 7, a sufficient purifying action is achieved. Since the second catalyst 11 is also activated, a sufficient purifying action is exerted on the exhaust gases of the # 1 cylinder and the # 4 cylinder that circulate through the second exhaust pipe 4.

  If the fluctuation amount α of the engine rotational speed Ne is greater than or equal to the allowable value α0, that is, if it is estimated that combustion is unstable due to misfire or the like although the # 2 and # 3 cylinders are operating, step The determination of No is made in S14 and the process proceeds directly to step S16. In other words, even if the second catalyst 11 does not reach the activation temperature and the purification performance is somewhat insufficient, it is assumed that the discharge of unburned components as a whole is less than continuing unstable combustion in the two cylinders. Immediately return to normal control.

  Note that the return timing to the normal control may be determined in consideration of the combustion state of the # 2 cylinder and the # 3 cylinder and the activation state of the second catalyst 11. For example, when the determination of No is made in step S14, the process does not proceed directly to step S16, but waits until the temperature increase required time T3 set as the time during which the second catalyst 11 is heated to some extent elapses (for example, You may make it transfer to step S16 after progress of the temperature increase required time T3 by making the said activity required time T1 into the upper limit for 0.5 to 20 seconds. In this manner, the unstable combustion in the two cylinders is minimized, and the second catalyst 11 exhibits a certain degree of purification performance when returning to the normal control for operating all the cylinders. The emission of unburned components due to these factors can be suppressed in a well-balanced manner.

  On the other hand, when the exhaust control valve 7 and the relief valve 10 are closed and fixed at the same time, more specifically, when the relief valve 10 is closed and fixed, exhaust gas flows from the first exhaust pipe 3 through the communication passage 9 to the second exhaust pipe 4. If the exhaust control valve 7 cannot be forced to open, the exhaust pressure in the first exhaust pipe 3 abnormally rises due to exhaust gas that has lost its destination. Even if the cranking is continued, the # 2 and # 3 cylinders are prevented from being exhausted and the engine 1 is not started without starting operation. Therefore, in this case, since the engine rotational speed Ne does not reach the complete explosion determination value Ne0, the ECU 21 makes a negative determination in step S10 and proceeds to step S20 (failure detection means).

  In step S20, it is determined whether or not the required start time T2 has elapsed from the start of cranking, and the routine is terminated while the determination is No. The required start time T2 is set as the time required for engine start. In the present embodiment, cooling is performed from the viewpoint that the engine startability deteriorates as the engine temperature decreases and time is required for start. The required start time T2 is extended as the water temperature THw is lower. More specifically, the water temperature region below the cooling determination value THw0 is subdivided in a map (not shown), and the required startup time T2 is set to a longer value as the cooling water temperature THw is lower (for example, 0.5-3. Within 0 sec).

  Then, the determination in step S10 is repeated until the required start time T2 elapses. If the complete explosion determination is not made in step S10 even if the required start time T2 elapses, it is considered that the engine cannot be started, and a Yes determination is made in step S20. In step S22, the warning lamp 25 is turned on, and in step S24, fuel injection control and ignition timing control are executed for the # 1 and # 4 cylinders. In step S26, the # 2 and # 3 cylinders are executed. After stopping the fuel injection control and the ignition timing control for, the routine is terminated.

  Even when the exhaust control valve 7 and the relief valve 10 are fixed, the exhaust gas can flow through the second exhaust pipe 4 without any influence. The engine 1 starts without running. The engine operation for two cylinders at this time is the minimum necessary to be implemented as limp home control, but the vehicle can be driven, and the driver who recognizes the engine trouble by displaying the warning light 25 Take measures such as driving the vehicle and traveling to a repair shop.

  As described above, in the exhaust emission control device of the multi-cylinder engine 1 of the present embodiment, each cylinder of the engine 1 is divided into the # 2 cylinder, the # 3 cylinder, the # 1 cylinder, and the # 4 cylinder, and the exhaust pipes 3 independent of each other. , 4 and catalysts 6, 11, an exhaust control valve 7 is provided in the first exhaust pipe 3, and a relief valve 10 is provided in a communication passage 9 that communicates both the exhaust pipes 3, 4. At the start of operation, only the # 2 and # 3 cylinders are operated and the exhaust control valve 7 is closed to reduce the unburned components and raise the temperature of the catalysts 6 and 11, while the exhaust control valve 7 and the relief valve 10 When the engine cannot be started due to the sticking of the engine, only the # 1 cylinder and the # 4 cylinder are operated. Therefore, even if the exhaust control valve 7 and the relief valve 10 are stuck, the operation of these # 1 cylinder and # 4 cylinder The engine 1 can be started by Who can implement the appropriate measures, such as self-propelled to the repair shop.

  In step S10, the exhaust control valve 7 and the relief valve 10 are fixed based on the starting condition of the engine 1 during cranking (specifically, whether or not the engine speed Ne has reached the complete explosion determination value Ne0). Therefore, the opening degree sensor for detecting the opening degree of the exhaust control valve 7 and the relief valve 10 is not required, and as a result, the configuration of the entire exhaust gas purification device can be simplified. In addition, the poppet type relief valve 10 is difficult to detect the opening degree by the opening degree sensor, but since there is no need to detect the opening degree itself, the exhaust control valve 7 and the relief valve are not considered without considering the opening degree sensor. There is also an advantage that the ten types can be arbitrarily set using, for example, a reed valve.

In addition, this description does not prevent detecting the closed sticking of the exhaust control valve 7 and the relief valve 10 by the opening sensor, and needless to say, the closing sticking may be detected by the opening sensor.
On the other hand, in step S20, since it is determined that the engine cannot be started based on the required start time T2 obtained from the coolant temperature THw, the engine start determination reflecting the current engine startability, and hence the accurate exhaust control valve 7 and relief are performed. The sticking detection of the valve 11 can be realized. For example, if the required start time T2 is too short, it is determined that the engine can be started, but the engine cannot be started (closed and fixed), and the operation with two cylinders # 1 and # 4 continues as limp home control. On the other hand, if the required start time T2 is too long, there is a problem that cranking is continued even though the engine cannot be started, causing wasteful battery consumption. Can be prevented.

Furthermore, since the cylinders (# 2, # 3 and # 1, # 4) in which combustion does not continue are set as the first and second cylinder groups, the catalyst temperature rises due to the operation of the # 2 cylinder and the # 3 cylinder, During the limp home control by the operation of the # 1 cylinder and the # 4 cylinder, the combustion of the two cylinders is performed at equal intervals, the engine output fluctuation is reduced, and stable vehicle running performance can be obtained.
In the present embodiment, the second catalyst 11 is provided on the downstream side of the relief valve 10 of the second exhaust pipe 4. However, as shown by the broken line in FIG. 1, the second catalyst 11 is upstream of the relief valve 10 of the second exhaust pipe 4. It may be provided on the side or may be provided on the downstream side exhaust pipe 5. However, when the second catalyst 11 is provided on the upstream side of the relief valve 10, during the operation by the # 2 cylinder and the # 3 cylinder, the rise by the exhaust gas guided to the second exhaust pipe 4 through the communication passage 9 is achieved. Since the temperature action cannot be obtained, it is desirable that the second catalyst 11 be installed on the downstream side of the relief valve 10.

  Further, in this embodiment, each cylinder of the in-line four-cylinder engine 1 is divided into the first and second cylinder groups. For example, in the V-type engine or the horizontally opposed engine shown in FIG. This bank may be the first cylinder group, and the other bank may be the second cylinder group. Even in this case, if the exhaust system configuration and control similar to those of the present embodiment are performed, the same effects can be obtained. And since the said structure can apply the existing exhaust layout as it is, another advantage that manufacturing cost can be reduced is also acquired.

[Second Embodiment]
Next, a second embodiment in which the present invention is embodied in another exhaust gas purification apparatus for a multi-cylinder engine will be described.
FIG. 4 is an overall configuration diagram showing an exhaust emission control device for a multi-cylinder engine according to a second embodiment. The exhaust emission control device of this embodiment is obtained by changing the configuration of the first and second exhaust pipes 3 and 4 as compared with that of the first embodiment. This is exactly the same as in the first embodiment. Therefore, common parts are denoted by the same member numbers, description thereof is omitted, and differences are mainly described.

  In short, in the exhaust purification apparatus of the present embodiment, the first exhaust pipe 3 and the second exhaust pipe 4 have a double structure. That is, the second exhaust pipe 4 is formed corresponding to the # 1 cylinder and the # 4 cylinder, and the second exhaust pipe 4 extends rearward of the vehicle and also plays the role of the downstream exhaust pipe 5 of the first embodiment. . The first exhaust pipe 3 corresponding to the # 2 cylinder and the # 3 cylinder is inserted into the second exhaust pipe 4 through the opening 31 formed on the upstream side of the second exhaust pipe 4 to be behind the vehicle. The downstream end of the first exhaust pipe 3 is opened in the middle of the second exhaust pipe 4.

  The first exhaust pipe 3 is provided with a first catalyst 6 on the upstream side and an exhaust control valve 7 on the downstream side. A communication passage 9 is provided between the first catalyst 6 and the exhaust control valve 7. Has been. Therefore, the inside of the first exhaust pipe 3 and the inside of the second exhaust pipe 4 communicate with each other via the communication passage 9 and communicate with the outer surface of the first exhaust pipe 3 in the second exhaust pipe 4. A reed valve 32 (exhaust gas switching valve) is provided so as to close the passage 9. The function of the reed valve 32 is the same as that of the relief valve 10 of the first embodiment. When the exhaust pressure of the first exhaust pipe 3 exceeds a set value, the communication passage 9 is opened. A second catalyst 11 is provided on the downstream side of the reed valve 32 of the second exhaust pipe 4.

  The operation state of the exhaust emission control device when the ECU 21 executes the cold start control routine is the same as that of the first embodiment. When the engine 1 is cold started, the first cylinder group # 2 cylinder and Only the # 3 cylinder is operated and the exhaust control valve 7 is closed to reduce the unburned components and raise the temperature of the catalysts 6 and 11, while the exhaust control valve 7 and the reed valve 32 are stuck and the engine cannot be started. Only the # 1 cylinder and # 4 cylinder, which are the second cylinder group, can be operated to start the engine 1.

  In addition, in the present embodiment, since the outer periphery of the first exhaust pipe 3 is surrounded by the second exhaust pipe 4, the first exhaust pipe 3 is associated with the operation of the # 2 cylinder and the # 3 cylinder. When exhaust gas circulates in the interior, the first and second exhaust pipes 3 and 4 have a heat insulation effect to prevent heat radiation to the outside, thereby increasing the heat of the exhaust gas to the temperature of the first catalyst 6. It is possible to obtain an advantage that early activation can be realized through effective use, and the temperature rise of the second catalyst 11 can be promoted.

[Third embodiment]
Next, a third embodiment in which the present invention is embodied in another multi-cylinder engine exhaust purification device will be described.
FIG. 5 is an overall configuration diagram showing an exhaust emission control device for a multi-cylinder engine according to a third embodiment. The exhaust emission control device of the present embodiment has a configuration of the exhaust system changed on the premise that the turbocharger 41 is attached as compared with that of the first embodiment, and the switching state of the valve is also controlled at the time of cold start shown in FIG. Since it is different from the routine, these differences will be explained mainly.
The engine 1 is configured as an in-line four-cylinder engine, and the # 2 cylinder and # 3 cylinder are set as a first cylinder group, and the # 1 cylinder and # 4 cylinder are set as a second cylinder group. A first catalyst 6 is provided in the first exhaust pipe 3 corresponding to the # 2 cylinder and the # 3 cylinder, and an exhaust control valve 7 is provided downstream of the first catalyst 6. One end of a communication passage 9 having an exhaust switching valve 42 is connected to the first exhaust pipe 3 upstream of the first catalyst 6, and the other end of the communication passage 9 corresponds to the # 1 cylinder and the # 4 cylinder. The second exhaust pipe 4 is connected. A turbocharger 41 and a second catalyst 11 are provided in the second exhaust pipe 4 on the downstream side of the connection point, and the first exhaust pipe is provided between the turbocharger 41 and the second catalyst 11. 3 is connected. The exhaust gas switching valve 42 is an electromagnetic valve that is driven and controlled by the ECU 21 in the same manner as the exhaust gas control valve 7.

  In the exhaust emission control device configured as described above, after the # 2 cylinder and the # 3 cylinder are operated at the time of cold start of the engine 1 as in the first embodiment, the normal control for operating all the cylinders is resumed. When the exhaust control valve 7 and the exhaust switching valve 42 are fixed together, the # 1 cylinder and the # 4 cylinder are operated instead of the # 2 cylinder and the # 3 cylinder. Basically, the exhaust control valve 7 functions as a normally closed wastegate valve, and only opens as the exhaust pressure rises. When the # 2 and # 3 cylinders are in operation, the exhaust switching valve 42 is closed. Thus, the exhaust gas can be guided to the first exhaust pipe 3 side to accelerate the activity of the first catalyst 6 and the exhaust gas flowing out from the exhaust control valve 7 can accelerate the activity of the second catalyst 11. I can plan. When all cylinders are in operation, the exhaust gas switching valve 42 is similarly opened, and exhaust gas from all cylinders is supplied to the turbocharger 41 so as to ensure a supercharging pressure.

Even in the exhaust purification device of the present embodiment configured as described above, the engine 1 can be started by operating the # 1 cylinder and the # 4 cylinder when the exhaust control valve 7 and the exhaust switching valve 52 are simultaneously fixed. The same effect as each embodiment can be obtained.
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in each of the above embodiments, the exhaust purification device of the in-line 4-cylinder engine and the V-type engine is embodied. However, the cylinder arrangement of the engine 1 is not limited to this and can be arbitrarily changed.

  In the above embodiment, the first exhaust pipe 3 and the second exhaust pipe 4 are connected by the communication passage 9 to provide the relief valve 10. In addition to the exhaust control valve 7 being closed and fixed, the relief valve 10 is closed. For example, in the first embodiment shown in FIG. 1, the communication passage 9 and the relief valve 10 may be omitted. In this case, the exhaust pressure is increased while circulating the exhaust gas of the # 2 cylinder and the # 3 cylinder by keeping the exhaust control valve 7 at a minute opening degree without fully closing at the time of cold start. And in such a configuration, when the exhaust control valve 7 is fixed on the closed side, the engine cannot be started immediately, but if the same control as in the first embodiment is performed and the # 1 cylinder and the # 4 cylinder are operated, Inability to start the engine can be avoided.

1 is an overall configuration diagram illustrating an exhaust emission control device for a multi-cylinder engine according to a first embodiment. It is a flowchart which shows the cold start time control routine which ECU performs. It is a figure which shows another example of 1st Embodiment which applied this invention to the V-type engine. It is a whole block diagram which shows the exhaust gas purification apparatus of the multicylinder engine which made the exhaust pipe of 2nd Embodiment the double structure. It is a whole block diagram which shows the exhaust gas purification apparatus of the multicylinder engine provided with the turbocharger of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 3 1st exhaust pipe 4 2nd exhaust pipe 6 1st catalyst 7 Exhaust control valve 9 Communication path 10 Relief valve (exhaust switching valve)
11 Second catalyst 21 ECU (failure detection means, combustion control means)
24 Crank angle sensor (engine speed detection means)
32 Reed valve (exhaust gas switching valve)
42 Exhaust selector valve

Claims (5)

In an exhaust emission control device for a multi-cylinder engine, the cylinders of the multi-cylinder engine are divided into two cylinder groups and each cylinder group has an exhaust pipe.
A first exhaust pipe for the first cylinder group;
A second exhaust pipe for the second cylinder group;
A first catalyst provided in the first exhaust pipe;
A second catalyst provided in the second exhaust pipe;
An exhaust control valve provided downstream of the first catalyst and closing the first exhaust pipe at the time of engine cold start;
A failure detecting means for detecting closed adhering of the exhaust control valve;
Combustion control means for controlling to switch between a first combustion state in which only at least the first cylinder group is operated and a second combustion state in which only the second cylinder group is operated;
The exhaust control valve is closed when the engine is cold started, and the first combustion state is set by the combustion control means. On the other hand, the exhaust gas is detected by the failure detection means when the engine is cold and the first combustion state is established. An exhaust purification device for a multi-cylinder engine, wherein when the control valve is detected to be closed, the combustion control means switches to the second combustion state. A communication path communicating between the middle of the first exhaust pipe and the middle of the second exhaust pipe;
An exhaust switching valve that is disposed in the communication passage and that opens the communication passage when the pressure in the first exhaust pipe exceeds a predetermined pressure;
2. The exhaust gas purifying apparatus for a multi-cylinder engine according to claim 1, wherein the failure detecting means detects the closed adhering of the exhaust control valve and detects the closed adhering of the exhaust switching valve. An engine rotation speed detecting means for detecting the engine rotation speed;
The failure detection means detects that the exhaust control valve is closed and fixed when the engine rotation speed detected by the engine rotation speed detection means is equal to or lower than a predetermined rotation speed even after a predetermined period has elapsed after starting. 2. An exhaust emission control device for a multi-cylinder engine according to claim 1.   4. The exhaust gas purification apparatus for a multi-cylinder engine according to claim 3, wherein the predetermined period is set longer as the engine temperature is lower.   The exhaust purification device for a multi-cylinder engine according to any one of claims 1 to 4, wherein the first and second cylinder groups are divided for each cylinder in which combustion does not continue.

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