JP2005315109A - Exhaust emission control system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology which can suppress a deterioration in exhaust emission even when a supercharger for executing supercharge by energy of exhaust gas is mounted in an internal combustion engine. <P>SOLUTION: In an internal combustion engine 1 having a plurality of cylinder groups 2a, 2b, exhaust passages 5a, 5b are branched off to one cylinder group 2a side and the other cylinder group 2b side. A supercharger 7 is mounted to execute supercharge only by exhaust gas circulating in the exhaust passages 5b on the other cylinder group 2b side. When the internal combustion engine 1 starts, only a cylinder 2 of one cylinder group 2a is activated by interrupting a cylinder 2 of the other cylinder group 2b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine, and more particularly, to an exhaust gas purification system for an internal combustion engine having a supercharger that supercharges with the energy of exhaust gas.

  In an internal combustion engine having a plurality of cylinder groups, the cylinders of one cylinder group and the cylinders of another cylinder group can be operated separately, and the cylinders of some cylinder groups can be operated in a low-load operation region or the like. There is something that operates with a pause.

In addition, when a turbocharger that supercharges with the energy of exhaust gas such as a turbocharger is installed in such an internal combustion engine, for example, in Patent Document 1, a cylinder group that is always operating and a cylinder group that is deactivated In the exhaust passage branched to the side, a first catalyst is provided in the working side exhaust passage, and a second catalyst is provided downstream of the joining portion of the working side exhaust passage and the pause side exhaust passage. A technique of installing a supercharger between the second catalyst is disclosed.
Japanese Patent Publication No. 3-12653 Japanese Patent Publication No. 60-22180 Japanese Patent Publication No. 60-22179 JP 2000-64868 A JP 58-158339 A

  When an internal combustion engine is equipped with a supercharger that supercharges with the energy of the exhaust, if the exhaust is used for supercharging by the supercharger before it flows into the exhaust purification catalyst, the heat capacity of the supercharger As a result, the temperature of the exhaust purification catalyst at the time of starting the engine is hindered. As a result, the exhaust gas purification ability at the time of starting the engine is lowered, and exhaust emission may be deteriorated.

  The present invention has been made in view of the above problems, and suppresses deterioration of exhaust emission at the time of engine start-up even in a case where a supercharger that is supercharged by the energy of exhaust gas is installed in an internal combustion engine. It is an object to provide a technology that can be used.

  According to the present invention, in an internal combustion engine having a plurality of cylinder groups, supercharging is performed only by exhaust gas that branches an exhaust passage between one cylinder group and another cylinder group and flows through an exhaust passage on the other cylinder group side. In this way, when the internal combustion engine is started, the cylinders of the other cylinder group are deactivated and only the cylinders of the one cylinder group are operated, so that the exhaust from the cylinders of the one cylinder group is performed. This promotes the temperature rise of the exhaust purification catalyst provided in the exhaust passage.

More specifically, the exhaust gas purification system for an internal combustion engine according to the present invention is:
In an exhaust gas purification system for an internal combustion engine that has a supercharger that supercharges by energy of exhaust gas and that can operate a cylinder of one cylinder group and a cylinder of another cylinder group separately in a plurality of cylinder groups,
A first exhaust passage having one end connected to a cylinder of the one cylinder group;
A second exhaust passage having one end connected to a cylinder of the other cylinder group and having the other end connected in the middle of the first exhaust passage;
An exhaust purification catalyst installed on the downstream side of the connection point with the second exhaust passage in the first exhaust passage;
A catalyst temperature detection device for detecting the temperature of the exhaust purification catalyst;
With
The supercharger is supercharged by the energy of exhaust gas flowing through the second exhaust passage,
When the internal combustion engine is started, if the temperature of the exhaust purification catalyst detected by the catalyst temperature detection device is lower than a specified catalyst temperature, the cylinders of the other cylinder group are deactivated and only the cylinders of the one cylinder group are deactivated. Is operated.

  Here, the specified catalyst temperature is a temperature at which it can be determined that the exhaust purification catalyst has been activated, and may be a temperature determined in advance through experiments or the like.

  In the present invention, when the temperature of the exhaust purification catalyst is lower than the specified catalyst temperature at the time of starting the engine, the cylinders of the other cylinder groups are deactivated and only the cylinders of the one cylinder group are operated. Exhaust gas from the cylinder flows into the exhaust purification catalyst without being used for supercharging by a supercharger (hereinafter simply referred to as a supercharger) that is supercharged by the energy of the exhaust gas.

  Therefore, according to the present invention, the temperature increase of the exhaust purification catalyst can be promoted at the time of engine start. As a result, deterioration of exhaust emission can be suppressed.

  In the present invention, after operating only the cylinders of one cylinder group at the time of starting the engine, the cylinders of the other cylinder groups are operated when the temperature of the exhaust purification catalyst rises to a specified catalyst temperature or higher. preferable.

  According to such control, after the temperature of the exhaust purification catalyst rises and the exhaust purification capability becomes high, the exhaust from the cylinders of other cylinder groups, that is, the exhaust used for supercharging by the supercharger is generated. In addition to the exhaust from the cylinders of one cylinder group, it flows into the exhaust purification catalyst. In this case, the influence of the exhaust from the cylinders of one cylinder group on the exhaust purification capability of the exhaust purification catalyst is small, and the exhaust can be more suitably purified.

  Further, in the present invention, when the engine temperature detecting device for detecting the temperature of the internal combustion engine is further provided, the temperature of the internal combustion engine becomes equal to or higher than the specified engine temperature after operating only the cylinders of one cylinder group when starting the engine. The cylinders of the other cylinder groups may be operated when the pressure rises to.

  Here, the prescribed engine temperature can be determined that when the fuel is injected into the cylinders of the other cylinder group, the temperature in the cylinders of the other cylinder group increases as the fuel is sufficiently atomized. The temperature may be a temperature determined in advance by an experiment or the like.

  If the fuel injected into the cylinders of the other cylinder group is sufficiently atomized, the amount of unburned fuel component contained in the exhaust gas from the cylinders of the other cylinder group is reduced. Therefore, according to the control as described above, it is possible to suppress the deterioration of the exhaust emission even when the cylinders of other cylinder groups are operated and the exhaust is discharged from the cylinders.

  In the present invention, the exhaust purification catalyst is the first exhaust purification catalyst, and the heat capacity of the first exhaust passage is higher than that of the first exhaust purification catalyst at the upstream side of the connection portion with the second exhaust passage. It is preferable to further install a small second exhaust purification catalyst.

  According to such a configuration, only the exhaust from the cylinders of one cylinder group flows into the second exhaust purification catalyst, and since the heat capacity is smaller than that of the first exhaust purification catalyst, the second exhaust purification catalyst The purification catalyst is activated earlier than the first exhaust purification catalyst. Therefore, it is possible to further suppress the deterioration of the exhaust emission when the engine is started.

  An example of the supercharger in the present invention is a turbocharger. In this case, the turbocharger turbine is disposed in the first exhaust passage.

  According to the exhaust gas purification system for an internal combustion engine according to the present invention, even when a supercharger that is supercharged by the energy of exhaust gas is installed in the internal combustion engine, deterioration of exhaust emission can be suppressed.

  Hereinafter, specific embodiments of an exhaust gas purification system for an internal combustion engine according to the present invention will be described with reference to the drawings.

<Schematic configuration of internal combustion engine and its intake / exhaust system>
Here, a case where the present invention is applied to a diesel engine for driving a vehicle will be described as an example. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its intake / exhaust system according to the present embodiment.

  The internal combustion engine 1 is a V-type 6-cylinder engine having six cylinders 2 from # 1 to # 6. In this embodiment, the cylinders # 1, # 3, and # 5 are the first cylinder group 2a, the cylinders # 2, # 4, and # 6 are the second cylinder group 2b, and the first cylinder group 2a and the first cylinder group 2a are the same. The two-cylinder group 2b is arranged in a V shape. Each cylinder 2 is provided with a fuel injection valve 3 for injecting fuel into a combustion chamber in the cylinder 2.

  One end of a first exhaust branch pipe 4a is connected to each cylinder 2 of the first cylinder group 2a. The other ends of the first exhaust branch pipes 4a are connected to each other at the collecting portion, and the collecting portion of the first exhaust branch pipes 4a is connected to one end of the first exhaust passage 5a. On the other hand, one end of the second exhaust branch pipe 4b is similarly connected to each cylinder 2 of the second cylinder group 2b. The other ends of the second exhaust branch pipes 4b are connected to each other at the collecting portion, and the collecting portion of the second exhaust branch pipes 4b is connected to one end of the second exhaust passage 5b. The other end of the second exhaust passage 5b is connected to the middle of the first exhaust passage 5a, and the exhaust is released into the atmosphere from the other end of the first exhaust passage 5a.

  A turbine housing 7b of a turbocharger (turbo supercharger) 7 is installed in the middle of the second exhaust passage 5b. The compressor housing 7a of the turbocharger 7 is installed in the middle of an intake passage 6 connected to each cylinder 2 of the second cylinder group 2b via an intake branch pipe.

  A compressor wheel 7c and a turbine wheel 7d are provided inside the compressor housing 7a and the turbine housing 7b, respectively. In the turbocharger 7, the turbine wheel 7d is rotated by the exhaust gas discharged from each cylinder 2 of the second cylinder group 2b and flowing into the turbine housing 7b. As the turbine wheel 7d rotates, the compressor wheel 7c rotates, so that intake air (air) flowing into the compressor housing 7a is supercharged to each cylinder 2 of the second cylinder group 2b. That is, the turbocharger 7 according to the present embodiment supercharges with the energy of the exhaust discharged from each cylinder 2 of the second cylinder group 2b.

A first exhaust purification catalyst 8 is installed in the first exhaust passage 5a on the downstream side of the connection point with the second exhaust passage 5b. In addition, a second exhaust purification catalyst 9 is installed in the first exhaust passage 5a upstream of the connection portion with the second exhaust passage 5b and in the vicinity of the connection portion with the first exhaust branch pipe 4a. Yes. The second exhaust purification catalyst 9 is a catalyst having a smaller heat capacity than the first exhaust purification catalyst 8. Examples of the first and second exhaust purification catalysts 8 and 9 include an oxidation catalyst, an NOx storage reduction catalyst, and a filter carrying these catalysts.

  An exhaust temperature sensor 10 that outputs an electrical signal corresponding to the temperature of the exhaust gas flowing through the first exhaust passage 5a is installed in the first exhaust passage 5a downstream of the first exhaust purification catalyst 8. The internal combustion engine 1 is also provided with a water temperature sensor 11 that outputs an electrical signal corresponding to the temperature of the cooling water flowing through the internal combustion engine 1.

  The internal combustion engine 1 configured as described above is provided with an ECU 12 for controlling the internal combustion engine 1. The ECU 12 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver. The ECU 12 is connected to various sensors such as the exhaust temperature sensor 10 and the water temperature sensor 11 through electric wiring, and these output signals are input to the ECU 12. Then, the ECU 12 estimates the temperature of the first exhaust purification catalyst 8 from the detection value of the exhaust temperature sensor 10. Further, the ECU 12 estimates the temperature of the internal combustion engine 1 from the detection value of the water temperature sensor 11.

  In addition, each fuel injection valve 3 is electrically connected to the ECU 12, and the fuel injection from each fuel injection valve 3 can be separately controlled by the ECU 12.

  In such a configuration, since the heat capacity of the turbocharger 7 is large, the temperature of the exhaust gas from the cylinder 2 of the second cylinder group 2b is lowered by passing through the turbine housing 7b. Therefore, when the first exhaust purification catalyst 8 is not activated, if the exhaust discharged from the cylinder 2 of the second cylinder group 2b and passing through the turbine housing 7b flows into the first exhaust purification catalyst 8, the first exhaust This raises the temperature of the purification catalyst.

<Cylinder operation control at engine start>
Therefore, in this embodiment, the cylinder operation control described below is performed when the engine is started.
FIG. 2 is a flowchart showing a cylinder operation control routine when starting the engine according to this embodiment. This routine is stored in advance in the ECU 12, and is repeated every predetermined time.

  In this routine, first, in S101, the ECU 12 determines whether or not a start command for the internal combustion engine 1 has been issued. As a case where it is determined that a start command has been issued, a case where an ignition switch is turned on can be exemplified. If an affirmative determination is made in S101, the ECU 12 proceeds to S102, and if a negative determination is made, the ECU 12 once ends the execution of this routine.

  In S102, the ECU 12 determines whether or not the temperature of the first exhaust purification catalyst 8 is lower than the specified catalyst temperature T1. Here, the specified catalyst temperature T1 is a temperature at which it can be determined that the first exhaust purification catalyst 8 has been activated, and is a temperature determined in advance by experiments or the like. If an affirmative determination is made in S102, the ECU 12 proceeds to S103, and if a negative determination is made, the ECU 12 proceeds to S104.

  The ECU 12 that has proceeded to S103 performs fuel injection in the cylinder 2 of the first cylinder group 2a without performing fuel injection in the cylinder 2 of the second cylinder group 2b. That is, the cylinder 2 of the second cylinder group 2b is deactivated and only the cylinder 2 of the first cylinder group 2a is operated. Thereafter, the ECU 12 once terminates execution of this routine.

The ECU 12 that has proceeded to S104 executes fuel injection in both the cylinders 2 of the first cylinder group 2a and the second cylinder group 2b. That is, both the cylinders 2 of the first cylinder group 2a and the second cylinder group 2b are operated. Thereafter, the ECU 12 once terminates execution of this routine.

  In the routine described above, if the temperature of the first exhaust purification catalyst 8 is lower than the specified catalyst temperature T1 when the engine is started, the cylinder 2 of the second cylinder group 2b is deactivated and the cylinder 2 of the first cylinder group 2a is deactivated. Only the exhaust from the cylinders 2 of the first cylinder group 2 a flows into the first exhaust purification catalyst 8. Since the exhaust from the cylinder 2 of the first cylinder group 2a does not pass through the turbocharger 7 (turbine housing 7b), the exhaust flows into the first exhaust purification catalyst 8 while maintaining a high temperature.

  Therefore, according to the present embodiment, it is possible to promote the temperature rise of the first exhaust purification catalyst 8 at the time of engine startup. As a result, deterioration of exhaust emission can be suppressed.

  In the present embodiment, the second exhaust purification catalyst 9 having a smaller heat capacity than the first exhaust purification catalyst 8 is installed in the first exhaust passage 5a on the upstream side of the connection portion with the second exhaust passage 5b. . The second exhaust purification catalyst 9 is only supplied with exhaust from the cylinders 2 of the first cylinder group 2a, and has a smaller heat capacity than the first exhaust purification catalyst 8, so that the second exhaust purification catalyst 9 is the first exhaust purification catalyst 9. It is activated earlier than the exhaust purification catalyst 8. Therefore, it is possible to further suppress the deterioration of the exhaust emission when the engine is started.

  In the present embodiment, when only the cylinder 2 of the first cylinder group 2a is operated at the time of starting the engine and then the temperature of the first exhaust purification catalyst 8 rises to the specified catalyst temperature T1 or higher, the second cylinder group 2b The cylinder 2 is preferably operated.

  According to such control, after the temperature of the first exhaust purification catalyst 8 rises and the exhaust purification capability becomes high, the exhaust is discharged from the cylinder 2 of the second cylinder group 2b and passes through the turbocharger 7 (turbine housing 7b). Exhaust exhaust flows into the first exhaust purification catalyst 8 in addition to the exhaust from the cylinders 2 of the first cylinder group 2a. In this case, the influence of the exhaust from the cylinder 2 of the second cylinder group 2b on the exhaust purification capability of the first exhaust purification catalyst 8 is small, and the exhaust can be more suitably purified.

  In the present embodiment, when only the cylinder 2 of the first cylinder group 2a is operated at the time of starting the engine and then the temperature of the internal combustion engine 1 rises to the specified engine temperature T2 or higher, the second cylinder group 2b The cylinder 2 may be operated.

  Here, the specified engine temperature T2 means that when the fuel is injected into the cylinder 2 of the second cylinder group 2b, the temperature in the cylinder 2 of the second cylinder group 2b is such that the fuel is sufficiently atomized. It is a temperature at which it can be determined that the temperature has risen, and may be a temperature determined in advance through experiments or the like.

  If the fuel injected into the cylinder 2 of the second cylinder group 2b is sufficiently atomized, the amount of unburned fuel component contained in the exhaust from the cylinder 2 of the second cylinder group 2b decreases. Therefore, according to the control as described above, even when the cylinder 2 of the second cylinder group 2b is operated and the exhaust gas is discharged from the cylinder 2, the deterioration of the exhaust emission can be suppressed.

  In the present embodiment, the internal combustion engine 1 is not limited to the V-type 6-cylinder engine, and may be any engine having a plurality of cylinders. Further, the turbocharger 7 only needs to be supercharged by exhaust energy from the cylinder 2 of the second cylinder group 2b. For example, a complex supercharger may be used instead of the turbocharger.

The figure which shows schematic structure of the internal combustion engine which concerns on the Example of this invention, and its intake-exhaust system. The flowchart figure which shows the cylinder operation control routine at the time of engine starting which concerns on the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 2a ... First cylinder group 2b ... Second cylinder group 3 ... Fuel injection valve 4a ... First exhaust branch pipe 4b ... Second exhaust branch pipe 5a ... First exhaust passage 5b Second exhaust passage 6 Intake passage 7 Turbocharger 7a Compressor housing 7b Turbine housing 7c Compressor wheel 7d Turbine wheel 8 First Exhaust purification catalyst 9 ... second exhaust purification catalyst 10 ... exhaust temperature sensor 11 ... water temperature sensor 12 ... ECU

Claims (5)

In an exhaust gas purification system for an internal combustion engine that has a supercharger that supercharges by energy of exhaust gas and that can operate a cylinder of one cylinder group and a cylinder of another cylinder group separately in a plurality of cylinder groups,
A first exhaust passage having one end connected to a cylinder of the one cylinder group;
A second exhaust passage having one end connected to a cylinder of the other cylinder group and having the other end connected in the middle of the first exhaust passage;
An exhaust purification catalyst installed in the first exhaust passage on the downstream side of a connection point with the second exhaust passage;
A catalyst temperature detecting device for detecting the temperature of the exhaust purification catalyst;
With
The supercharger is supercharged by the energy of exhaust gas flowing through the second exhaust passage,
When the internal combustion engine is started, if the temperature of the exhaust purification catalyst detected by the catalyst temperature detection device is lower than a specified catalyst temperature, the cylinders of the other cylinder group are deactivated and only the cylinders of the one cylinder group are deactivated. An exhaust gas purification system for an internal combustion engine characterized by operating the engine.   2. The cylinders of the other cylinder group are operated when the temperature of the exhaust purification catalyst rises to the specified catalyst temperature or higher after operating the cylinders of the one cylinder group. An exhaust purification system for an internal combustion engine as described. An engine temperature detection device for detecting the temperature of the internal combustion engine;
After operating the cylinders of the one cylinder group, when the temperature of the internal combustion engine detected by the engine temperature detection device rises to a specified engine temperature or higher, operate the cylinders of the other cylinder group The exhaust gas purification system for an internal combustion engine according to claim 1. The exhaust purification catalyst is a first exhaust purification catalyst,
A second exhaust purification catalyst installed in the first exhaust passage on the upstream side of the connection point with the second exhaust passage and having a smaller heat capacity than the first exhaust purification catalyst; The exhaust gas purification system for an internal combustion engine according to any one of claims 1 to 3.   The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the supercharger is a turbocharger in which a turbine is disposed in the second exhaust passage.

Images