JP2006022787A - Exhaust emission control system for v-eight internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technique for inhibiting a reducing agent added from a reducing agent addition valve from adhering onto a wall surface of an exhaust pipe and for allowing the reducing agent to more surly reach an exhaust emission control device in a V-eight internal combustion engine. <P>SOLUTION: In the V-eight internal combustion engine in which a combustion interval between two cylinders (#5, #7) in the same bank is a crank angle of 90 degrees, when the reducing agent is supplied to the exhaust emission control device, the reducing agent is added (t1-t2) from the reducing agent addition valve in synchronization with valve opening periods of exhaust valves of the predetermined two cylinders (#5, #7). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust purification system for a V-type 8-cylinder internal combustion engine.

  In order to purify NOx in the exhaust gas of an internal combustion engine, it is known to provide a NOx catalyst in the exhaust system of the internal combustion engine. Here, for example, in the case of an NOx storage reduction catalyst, the purification performance deteriorates as the amount of NOx stored increases. Therefore, fuel as a reducing agent is supplied to the NOx storage reduction catalyst, and NOx stored in the catalyst is reduced and released (hereinafter referred to as “NOx reduction treatment”). Further, it is known that SOx poisoning in which the purification performance deteriorates due to the SOx in the exhaust gas being stored in the NOx catalyst, and in order to eliminate this SOx poisoning, a reducing agent is added to the NOx catalyst. May be supplied (hereinafter referred to as “SOx poisoning recovery process”).

  In addition, a technique is known in which a particulate filter (hereinafter referred to as “filter”) is provided in an exhaust system of an internal combustion engine in order to collect particulate matter in the exhaust gas of the internal combustion engine. Even in such a filter, when the amount of collected particulate matter increases, the back pressure in the exhaust increases due to clogging of the filter and the engine performance decreases, so by increasing the exhaust temperature upstream of the filter, The collected particulate matter is oxidized and removed (hereinafter referred to as “filter regeneration process.” In addition, the NOx reduction process, the SOx poisoning recovery process, and the filter regeneration process are combined to provide “NOx reduction process”. That said.)

  Then, as a method for raising the exhaust temperature upstream of the filter in the regeneration process, an oxidation catalyst having an oxidizing ability is arranged upstream of the filter, and fuel as a reducing agent is supplied to the oxidation catalyst during the regeneration process. Thus, there is known a method of causing an oxidation reaction of fuel in the oxidation catalyst and increasing the exhaust temperature on the upstream side of the filter.

  Here, in order to supply fuel as a reducing agent to the above NOx catalyst or filter, a technique is known that includes a fuel addition valve on the upstream side of the NOx catalyst or filter. Regarding the technology, a fuel addition valve is attached to an exhaust port of a cylinder that is closest to an exhaust manifold pipe in the exhaust manifold and farthest from an opening of the EGR pipe, and fuel is added in accordance with the opening timing of the exhaust valve of the cylinder. Has been proposed. As a result, the fuel added from the fuel addition valve is prevented from adhering to the exhaust manifold or flowing into the EGR pipe, and is efficiently supplied to the NOx catalyst and the filter (for example, Patent Document 1). reference.).

However, even in the above-described prior art, it may be difficult to sufficiently suppress the fuel added from the fuel addition valve from adhering to the wall surface of the exhaust system. As a result, it may be difficult to ensure that the fuel added from the fuel addition valve reaches the NOx catalyst or the filter.
JP 2001-280125 A JP 2002-106332 A

  An object of the present invention is to prevent the reducing agent added from the reducing agent addition valve from adhering to the wall surface of the exhaust pipe in the V-type 8-cylinder internal combustion engine, thereby more reliably reducing the reducing agent. It is to provide a technology that can be reached.

  In order to achieve the above object, in the V-type 8-cylinder internal combustion engine in which the combustion interval between two predetermined cylinders in the same bank is a crank angle of 90 degrees, when supplying the reducing agent to the exhaust purification device, The greatest feature is that the reducing agent is added from the reducing agent addition valve in synchronization with the opening period of the exhaust valves of the two predetermined cylinders.

More specifically, an exhaust manifold is provided for each bank in the V-type 8-cylinder internal combustion engine, and includes a branch pipe portion connected to an exhaust port of each cylinder in each bank and a collecting pipe portion in which the branch pipe portions are gathered.
An exhaust pipe through which the exhaust from the internal combustion engine flowing out of the collecting pipe portion of the exhaust manifold passes;
An exhaust gas purification device that is provided in the exhaust pipe and purifies exhaust gas from the internal combustion engine;
A reducing agent addition valve that is attached to the exhaust pipe upstream of the exhaust purification device and adds a reducing agent to the exhaust gas that passes through the exhaust pipe, and supplies the reducing agent to the exhaust purification device,
An exhaust purification system of a V-type 8-cylinder internal combustion engine in which combustion is performed at a crank angle interval of 90 degrees in two predetermined cylinders in the same bank,
When supplying a reducing agent to the exhaust purification device,
The reducing agent is added by the reducing agent addition valve during the opening period of the exhaust valve in the two cylinders where combustion is performed at the crank angle interval of 90 degrees.

  Here, the present invention provides a reducing agent addition valve for performing a NOx reduction process of the exhaust purification device by supplying a reducing agent to the exhaust purification device of the internal combustion engine, which is located on the downstream side of the exhaust manifold. It is assumed to be placed in a pipe.

  Conventionally, by supplying a reducing agent to the exhaust purification device as described above, when performing the NOx reduction processing, the reducing agent addition valve is synchronized with the valve opening period of the exhaust valve of the cylinder of each bank. There is a case where control for adding the reducing agent into the exhaust gas is performed. However, in such a case, the reducing agent added from the reducing agent addition valve cannot be sent to the downstream side in a sufficiently strong exhaust flow, so that the reducing agent adheres to the wall surface of the exhaust pipe or flows backward. In some cases, it is difficult to reliably supply the exhaust gas purification apparatus. As a result, the NOx reduction process or the like may not be performed sufficiently, or the consumption efficiency of the reducing agent in the NOx reduction process may deteriorate.

  On the other hand, in a V-type 8-cylinder internal combustion engine, the combustion intervals of the cylinders in each bank may not be equal from the viewpoint of suppressing vibrations. When the combustion intervals of the cylinders in each bank are equal, the combustion intervals of the cylinders in the same bank are 180 degrees crank angle, whereas when the combustion intervals are unequal as described above, the same The combustion interval between two cylinders in the bank may be 90 degrees crank angle.

  When the combustion interval between two cylinders in the same bank is 90 degrees crank angle, the valve opening timings of the exhaust valves of the two cylinders partially overlap. Therefore, during the overlap period, the internal combustion engine to the exhaust manifold The exhaust flow rate of the exhaust gas flowing into the exhaust pipe via the exhaust gas becomes larger than usual.

Therefore, in the present invention, when the combustion interval between two predetermined cylinders in the same bank is 90 degrees crank angle, the reducing agent addition valve is synchronized with the opening period of the exhaust valves of the two cylinders. A reducing agent was added to the exhaust. In this way, the reducing agent added from the reducing agent addition valve is sent to the downstream side by the strong exhaust flow in the overlap period of the opening timings of the exhaust valves of the two cylinders. It can suppress adhering to the wall surface of a pipe | tube, or backflow, and can make this reducing agent reach an exhaust gas purification apparatus more reliably.

  Further, in the present invention, the exhaust valve opening period in the two cylinders in which combustion is performed at the crank angle interval of 90 degrees, in the period in which the valve opening timings of the exhaust valves in the two cylinders overlap, You may make it supply a reducing agent to the said exhaust gas purification apparatus by adding a reducing agent from a reducing agent addition valve.

  That is, as described above, when the combustion interval between the two cylinders reaches a crank angle of 90 degrees, the opening timings of the exhaust valves of the two cylinders partially overlap. In the overlap period, the exhaust flow rate of the exhaust gas flowing into the exhaust pipe increases more reliably.

  Therefore, if the reducing agent is added by the reducing agent addition valve during the period when the opening timings of the exhaust valves in the two cylinders overlap, the reducing agent added from the reducing agent addition valve can be more reliably applied. Can be prevented from adhering to the wall surface of the exhaust pipe or flowing backward, and can reach the exhaust purification device more reliably.

  In the present invention, the exhaust valve opening period in the two cylinders where combustion is performed at the crank angle interval of 90 degrees is a period in which the sum of the exhaust flow rates of the exhaust gas from the two cylinders is greater than a predetermined value. The reducing agent may be supplied to the exhaust purification device by adding a reducing agent from the reducing agent addition valve.

  That is, the exhaust flow rate of the exhaust gas flowing into the exhaust pipe is more reliably increased during the period when the valve opening timings of the exhaust valves of the two cylinders overlap. However, even within the overlap period, the exhaust flow rate of the exhaust gas flowing into the exhaust pipe changes one by one. Further, the exhaust flow rate of the exhaust gas flowing into the exhaust pipe during the overlap period also changes depending on the operating state of the internal combustion engine. Therefore, in the present invention, the reducing agent is added to the exhaust gas by the reducing agent addition valve during a period in which the exhaust flow rate of the exhaust gas from the two cylinders actually exceeds a predetermined value.

  By doing so, the reducing agent can be added to the exhaust gas by the reducing agent addition valve during the period when it is confirmed that the exhaust flow rate of the exhaust gas by the two cylinders actually exceeds a predetermined value. Therefore, it is possible to more reliably prevent the reducing agent added from the reducing agent addition valve from adhering to the wall surface of the exhaust pipe or to flow backward, and to reach the exhaust purification device more reliably.

  Here, the predetermined value means that the reducing agent added from the reducing agent addition valve can surely reach the exhaust purification device if the exhaust gas flow rate of the exhaust gas passing through the exhaust pipe is larger than that. The exhaust flow rate may be used as a threshold value. Further, for example, it may be a substantially maximum value in the exhaust flow rate of exhaust from a cylinder that does not perform combustion at a crank angle interval of 90 degrees. These values may be obtained experimentally in advance.

  Note that the period during which the exhaust flow rate of the exhaust gas passing through the exhaust pipe is larger than the predetermined value may be experimentally obtained in advance and stored in relation to the crank angle. Further, a sensor for detecting the exhaust flow rate may be provided in the exhaust pipe, and it may be determined from the output of the sensor that the exhaust flow rate is greater than a predetermined value.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  In the present invention, in the V-type 8-cylinder internal combustion engine, the reducing agent added from the reducing agent addition valve is prevented from adhering to the wall surface of the exhaust pipe, and the reducing agent reaches the exhaust purification device more reliably. Can be made.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its exhaust system and control system according to this embodiment. The internal combustion engine 1 shown in FIG. 1 is a V-type 8-cylinder diesel engine.

  The internal combustion engine 1 includes two banks, a first bank 1a and a second bank 1b. The first bank 1a includes four cylinders 2a, # 1, # 3, # 5, and # 7. The second bank 2b is provided with four cylinders 2b # 2, # 4, # 6, and # 8. Each cylinder 2a, 2b is provided with exhaust valves 3a, 3b for exhausting exhaust gas after combustion. The internal combustion engine 1 is provided with a crank position sensor 13 that detects an angle (crank angle) of a crankshaft (not shown) that is an output shaft of the internal combustion engine 1.

  The exhaust valves 3a and 3b are connected to the exhaust manifolds 5a and 5b through the exhaust ports 4a and 4b. The exhaust manifolds 5a and 5b are branch pipe portions 6a and 6b for connecting to the exhaust ports 4a and 4b, and a set for collecting exhaust introduced from the branch pipe portions 6a and 6b and passing them downstream. It has the pipe parts 7a and 7b.

  Exhaust pipes 9a and 9b are connected downstream of the exhaust manifolds 5a and 5b. The exhaust pipes 9a and 9b are connected to a muffler (not shown) at the ends. Further, in the middle of the exhaust pipes 9a and 9b, filters 10a and 10b for purifying particulate matter and NOx in the exhaust are provided.

  The filters 10a and 10b in this embodiment are obtained by supporting a NOx storage reduction catalyst on a wall flow type particulate filter made of a porous base material. However, the filters 10a and 10b do not necessarily have a configuration in which the NOx storage reduction catalyst is supported on the particulate filter. For example, the filters 10a and 10b are provided in series with the particulate filter on which the NOx storage reduction catalyst is not supported. Alternatively, it may be configured of a storage reduction type NOx catalyst. Further, a NOx catalyst other than the NOx storage reduction catalyst may be used.

  Here, the filters 10a and 10b correspond to the exhaust purification device in the present embodiment. In addition, when performing NOx reduction processing or the like for the filters 10a and 10b in the present embodiment, fuel as a reducing agent may be supplied from the upstream side of the filter, but in this embodiment, during NOx reduction processing or the like. The fuel addition valves 12a and 12b for adding fuel as a reducing agent are provided facing the exhaust pipes 9a and 9b.

  The internal combustion engine 1 configured as described above and its exhaust system are provided with an electronic control unit (ECU) 35 for controlling the internal combustion engine 1 and the exhaust system. The ECU 35 is a unit that controls the exhaust gas purification devices 10a and 10b of the internal combustion engine 1 in addition to controlling 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.

Sensors related to control of the operating state of the internal combustion engine 1 such as the crank position sensor 13 are connected to the ECU 35 via electric wiring, and their output signals are input to the ECU 35. On the other hand, a fuel injection valve (not shown) in the internal combustion engine 1 is connected to the ECU 35 via an electrical wiring, and the fuel addition valves 12a and 12b in this embodiment are connected via an electrical wiring. Is controlled by.

  The ECU 35 includes a CPU, a ROM, a RAM, and the like. The ROM stores a program for performing various controls of the internal combustion engine 1 and a map storing data. In addition to the NOx reduction processing routine for reducing and releasing NOx occluded in the filters 10a and 10b, the SOx poisoning recovery processing routine, the filter regeneration processing routine (all of which are omitted) are also stored in the ROM of the ECU 35. Is one of the programs.

  Next, processing such as NOx reduction processing of the filters 10a and 10b in the present embodiment will be described. During the NOx reduction process for the filters 10a and 10b, fuel as a reducing agent is added from the fuel addition valves 12a and 12b. At this time, the fuel addition from the fuel addition valve 12a is performed in synchronization with the opening timing of the exhaust valve 3a of any cylinder 2a in the first bank 1a. The fuel addition from the fuel addition valve 12b is performed in synchronization with the opening of the exhaust valve 3b of any cylinder 2b in the second bank 1b. This is because the fuel added from the fuel addition valves 12a and 12b is sent to the downstream side by the exhaust flow discharged from the cylinders 2a and 2b, and reliably supplied to the filters 10a and 10b.

  However, when the exhaust gas flow rate of the exhaust gas discharged from the cylinders 2a and 2b is not sufficient, a strong exhaust gas flow cannot be formed, and the fuel added from the fuel addition valves 12a and 12b is reliably supplied to the filters 10a and 10b. It becomes difficult to supply to. In this case, the fuel added from the fuel addition valves 12a and 12b may adhere to the wall surfaces of the exhaust pipes 9a and 9b or may flow backward.

  On the other hand, in the V-type 8-cylinder diesel engine in the present embodiment, the combustion intervals of the cylinders in each bank may be set at unequal intervals from the viewpoint of preventing vibrations. As a result, the opening timing of the exhaust valve in each cylinder also becomes unequal intervals. Here, FIG. 2 illustrates an exhaust valve opening timing pattern of each cylinder in each bank of the V-type 8-cylinder diesel engine. 2 (a) to 2 (d), the horizontal axis indicates the crank angle, and each square has the cylinder number at which the exhaust valve starts to open at the crank angle indicated by the left end of each square. ing. The width of each square is 90 degrees, but this does not mean that the valve opening period of each cylinder is a 90 degree crank angle, and merely indicates the exhaust valve opening timing of each cylinder.

  In the internal combustion engine 1 in this embodiment, the exhaust valve opening timing pattern is as shown in FIG. That is, in the first bank 1a, since the combustion interval between the # 5 cylinder 2a and the # 7 cylinder 2a is a 90 degree crank angle, the exhaust valve opening timing interval is also as shown in FIG. The crank angle is 90 degrees. On the other hand, in the second bank 1b, similarly, since the combustion interval between the # 8 cylinder 2b and the # 4 cylinder 2b is a crank angle of 90 degrees, the exhaust valve opening timing as shown in FIG. The interval is also 90 ° crank angle (hereinafter, the combustion of the cylinders 2a and 2b when the combustion interval is 90 ° crank angle is referred to as “continuous combustion”).

  The exhaust valve opening timing pattern of the V-type 8-cylinder engine is not limited to that of FIG. 2A, but is not shown, but continuous combustion is performed only in one of the first bank 1a and the second bank 1b. There is a pattern in which continuous combustion is not performed in the other bank. Actually, when continuous combustion is performed in at least one of the first bank 1a and the second bank 1b, the control of this embodiment described later may be applied to the continuously burned cylinder.

Here, when continuous combustion as described above is performed, the valve opening periods of the exhaust valves of the two cylinders overlap. Then, during the period when the valve opening periods of the exhaust valves of the two cylinders overlap, the exhaust gas flow increases because the exhaust gas discharged from the two cylinders merges. As a result, a strong exhaust flow can be formed. In the present embodiment, the fuel added from the fuel addition valves 12a and 12b is supplied to the filters 10a and 10b by using the strong exhaust flow formed when the continuous combustion as described above is performed.

  FIG. 3 shows the change in the exhaust flow rate due to exhaust from each cylinder and the timing of fuel addition from the fuel addition valves 12a and 12b in the case of the exhaust valve opening timing pattern shown in FIG. FIG. 3A is a graph of the exhaust flow rate due to the exhaust from the cylinder in the first bank 1a, and FIG. 3B is the second bank 1b. In each graph, the horizontal axis indicates the crank angle, and the vertical axis indicates the exhaust flow rate. Note that the graph shown in FIG. 3 is a change in the exhaust flow rate due to the exhaust from each cylinder. Therefore, in reality, the change is accompanied by a certain delay with respect to the opening and closing of the exhaust valve of each cylinder. In the following description, for convenience, it is assumed that the change in the exhaust flow rate occurs substantially simultaneously with the opening and closing of the exhaust valve of each cylinder. In addition, when the delay becomes large depending on the configuration of the internal combustion engine, control is performed in consideration of the delay period from the opening / closing of the exhaust valve of each cylinder until the change in the exhaust flow rate accompanying the opening / closing. .

  Here, in FIG. 3A, the exhaust from the # 5 cylinder 2a and the opening timing of the exhaust valve of the # 7 cylinder 2a overlap, so that the exhaust from the two cylinders partially overlap. I understand that In this case, as indicated by a broken line in the figure, in the period when the opening timings of the exhaust valves of the # 5 cylinder 2a and the # 7 cylinder 2a overlap, the exhaust from the # 5 cylinder 2a and the exhaust from the # 7 cylinder 2a The exhaust gas merges, and the total exhaust flow rate temporarily increases significantly.

  Further, in FIG. 3B, the exhaust from the # 8 cylinder 2b and the exhaust from the # 4 cylinder 2b partially overlap, but in this case as well, as shown by the broken line in the figure, During the period when the opening timings of the exhaust valves of the 8 cylinder 2b and the # 4 cylinder 2b overlap, the exhaust from the # 8 cylinder 2b and the exhaust from the # 4 cylinder 2b merge, and the exhaust flow rate as a total is temporarily Increase significantly.

  Therefore, in the NOx reduction processing according to this embodiment, the fuel addition timing from the fuel addition valve 12a is the opening timing of the exhaust valves of the # 5 cylinder 2a and the # 7 cylinder 2a in FIG. It is between time t1 and time t2. Similarly, the fuel addition timing from the fuel addition valve 12b is between time t3 and time t4, which is the opening timing of the exhaust valves of the # 8 cylinder 2b and # 4 cylinder 2b in FIG. 3B.

  In this way, fuel is supplied from the fuel addition valves 12a and 12b during the period including the overlap period of the opening timing of the exhaust valves in the # 5 cylinder 2a and # 7 cylinder 2a, or the # 8 cylinder 2b and # 4 cylinder 2b. Since the fuel can be added, the fuel added from the fuel addition valves 12a and 12b can be sent to the downstream side by using the strong exhaust flow formed by joining the exhausts discharged from the continuously combusting cylinders. Thereby, it can suppress that the fuel added from the fuel addition means 12a, 12b adheres to the wall surface of exhaust pipe 9a, 9b, and can make a fuel reach filter 10a, 10b reliably.

  Next, FIG. 4 shows another aspect of the change in the exhaust flow rate due to the exhaust from each cylinder and the timing of fuel addition from the fuel addition valves 12a and 12b corresponding thereto. The change in the exhaust flow rate due to the exhaust from each cylinder shown in FIG. 4 is the same as that shown in FIG.

In this embodiment, the fuel addition timing from the fuel addition valve 12a in the NOx reduction process of the filter 10a is the overlap of the opening timings of the exhaust valves of the # 5 cylinder 2a and # 7 cylinder 2a in FIG. The period is between time t5 and time t6. Similarly, the fuel addition timing from the fuel addition valve 12b is between time t7 and time t8, which is the overlap period of the opening timings of the exhaust valves of the # 8 cylinder 2b and # 4 cylinder 2b in FIG. 3B. And

  In this way, the fuel addition valve 12a, using only the strong exhaust flow formed by joining the exhaust discharged from the # 5 cylinder 2a and the # 7 cylinder 2a, or the # 8 cylinder 2b and the # 4 cylinder 2b, The fuel added from 12b can be sent downstream. Thereby, it can suppress more reliably that the fuel added from the fuel addition means 12a, 12b adheres to the wall surface of exhaust pipe 9a, 9b, and can make a fuel reach filter 10a, 10b more reliably.

  Next, FIG. 5 shows still another aspect of the change in the exhaust flow rate due to the exhaust from each cylinder and the timing of fuel addition from the fuel addition valves 12a and 12b. The change in the exhaust flow rate due to the exhaust from each cylinder shown in FIG. 5 is the same as that shown in FIG.

  In FIG. 5A, the fuel addition timing from the fuel addition valve 12a indicates the total exhaust flow rate when the exhaust from the # 5 cylinder 2a and the exhaust from the # 7 cylinder 2a merge. Is set between the time point t9 and the time point t10, which is greater than F1. Similarly, in FIG. 5 (b), the total exhaust flow rate when the exhaust from the # 8 cylinder 2b and the exhaust from the # 4 cylinder 2b are merged is determined as the fuel addition timing from the fuel addition valve 12b. The time is set between the time point t11 and the time point t12 that are larger than F1.

  Here, F1 reliably suppresses the adhering to the wall surface of the exhaust pipe 9a and the back flow when the fuel from the fuel addition valve 12a is sent to the exhaust with a larger exhaust flow rate and sent downstream. It is an exhaust flow rate as a threshold value that can be more reliably supplied to the filter 10a, and is a value obtained experimentally in advance. Also, the values from the time point t9 to the time point t12 are experimentally obtained in advance as a time point when the sum of the exhaust flow rates from the two cylinders exceeds F1 or falls below F1, and is stored in relation to the crank angle. You may keep it.

  In this way, the fuel from the fuel addition valves 12a and 12b can be more reliably suppressed from adhering to the wall surfaces of the exhaust pipes 9a and 9b and backflow, and added from the fuel addition valves 12a and 12b. The fuel can be supplied to the filters 10a and 10b more reliably.

  Here, the value of F1 may be set, for example, as the maximum value of the exhaust flow rate due to the exhaust from each cylinder 2a, 2b when continuous combustion is not considered. Further, it may be varied according to the operating state of the internal combustion engine 1.

  In the above embodiment, the example in which the turbine housing of the centrifugal supercharger is not provided between the collecting pipe portions 7a and 7b of the exhaust manifold and the exhaust pipes 9a and 9b has been described. You may take the structure in which the housing was provided.

It is a figure which shows schematic structure of the internal combustion engine which concerns on the Example of this invention, its exhaust system, and a control system. It is a figure shown about the pattern of the exhaust valve opening timing of each cylinder which concerns on the Example of this invention. It is a time chart which shows the change of the exhaust flow rate of the exhaust_gas | exhaustion from each cylinder which concerns on the Example of this invention, and the time of fuel addition. It is a time chart which shows another example of the change of the exhaust flow volume of the exhaust gas from each cylinder concerning the example of the present invention, and the timing of fuel addition. It is a time chart which shows the further another example of the change of the exhaust flow volume of the exhaust gas from each cylinder which concerns on the Example of this invention, and the time of fuel addition.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 1a ... 1st bank 1b ... 2nd bank 2a, 2b ... Cylinder 3a, 3b ... Exhaust valve 4a, 4b ... Exhaust port 5a, 5b ... Exhaust Manifold 6a, 6b ... Branch pipe part 7a, 7b ... Collecting pipe part 9a, 9b ... Exhaust pipe 10a, 10b ... Filter 12a, 12b ... Fuel addition valve 13 ... Crank position sensor 35 ... ECU

Claims (3)

An exhaust manifold which is provided for each bank in the V-type 8-cylinder internal combustion engine, and has a branch pipe connected to an exhaust port of each cylinder in each bank and a collecting pipe in which the branch pipes are gathered;
An exhaust pipe through which the exhaust from the internal combustion engine that has flowed out of the collecting pipe portion of the exhaust manifold passes,
An exhaust gas purification device that is provided in the exhaust pipe and purifies exhaust gas from the internal combustion engine;
A reducing agent addition valve that is attached to the exhaust pipe upstream of the exhaust purification device and adds a reducing agent to the exhaust gas that passes through the exhaust pipe, and supplies the reducing agent to the exhaust purification device,
An exhaust purification system of a V-type 8-cylinder internal combustion engine in which combustion is performed at a crank angle interval of 90 degrees in two predetermined cylinders in the same bank,
When supplying a reducing agent to the exhaust purification device,
An exhaust purification system for a V-type 8-cylinder internal combustion engine, wherein a reducing agent is added by the reducing agent addition valve during an opening period of an exhaust valve in two cylinders that perform combustion at a crank angle interval of 90 degrees. .   Of the opening periods of the exhaust valves in the two cylinders in which combustion is performed at the crank angle interval of 90 degrees, the reduction agent is added from the reducing agent addition valve during a period in which the opening timings of the exhaust valves in the two cylinders overlap. The exhaust purification system of a V-type 8-cylinder internal combustion engine according to claim 1, wherein a reducing agent is supplied to the exhaust purification device by adding an agent.   Among the valve opening periods of the exhaust valves in the two cylinders where combustion is performed at the crank angle interval of 90 degrees, during the period when the total exhaust flow rate of the exhaust gas from the two cylinders is greater than a predetermined value, the reducing agent addition valve The exhaust purification system of a V-type 8-cylinder internal combustion engine according to claim 1, wherein the reducing agent is supplied to the exhaust purification device by adding a reducing agent.

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