JP2007255371A - Injection control method of reducing agent for exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent reduction in the effect due to exhaust gas recirculation, by operating a reducing agent injection valve, when a cylinder nearest to a communicating position of a recirculating pipe is on an exhaust stroke. <P>SOLUTION: In this injection control method, an internal combustion engine has a plurality of cylinders, and has an exhaust manifold having a pipe aggregation part of aggregating respective pipes individually communicating with respective exhaust ports corresponding to the respective cylinders and the recirculating pipe communicating with the exhaust manifold and recirculating exhaust gas to an intake system, and is formed by arranging the reducing agent injection valve of injecting a reducing agent for exhaust gas into the exhaust manifold in a first part among two parts of sandwiching the pipe aggregation part, and is formed by communicating the recirculating pipe with a second part existing in the opposite direction of the first part. When recirculating the exhaust gas to the intake system, when the cylinder positioned on the recirculating pipe side more than the pipe aggregation part is on the exhaust stroke, the reducing agent injection valve is operated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an injection control method of a reducing agent for exhaust gas injected into an exhaust system in order to purify exhaust gas of an internal combustion engine.

  Conventionally, for example, an internal combustion engine mounted on a vehicle such as an automobile, particularly a diesel engine, is provided with a catalyst for purifying exhaust gas, and exhaust gas is sucked in order to reduce nitrogen oxides in the exhaust gas. One having an exhaust gas recirculation device for recirculation to the system is known. In recent years, in such a configuration, the catalyst further absorbs nitrogen oxides, and its function is reduced due to the absorption amount exceeding the limit amount, so that at least the nitrogen absorbed by the catalyst is reduced. In order to reduce oxides, an exhaust gas reducing agent is injected into the exhaust system.

As what injects such a reducing agent, the thing of patent document 1 is known, for example. In the device disclosed in Patent Document 1, an exhaust manifold and an exhaust pipe are communicated with each other through an exhaust collecting pipe, and a reducing agent injection valve for injecting a reducing agent for exhaust gas is attached in the vicinity of the communicating portion of the exhaust manifold with the exhaust collecting pipe. A recirculation line that recirculates exhaust gas to the intake manifold is connected to the end portion of the exhaust manifold opposite to the exhaust manifold connection site, and the cylinder close to the exhaust manifold communication site is exhausted during the exhaust stroke. By atomizing the reducing agent for gas, the atomized reducing agent for exhaust gas is put on the exhaust flow and flows downstream. By adopting such a configuration, the exhaust gas reducing agent is prevented from flowing into the recirculation pipeline.
JP 2001-280125 A

  Usually, if it is a diesel engine, the fuel which the diesel engine uses is used as a reducing agent for exhaust gas. In the above-mentioned Patent Document 1, since the exhaust gas reducing agent, that is, the fuel is injected when the cylinder close to the reducing agent injection valve discharges the exhaust gas, the fuel is exhausted in a state where the exhaust gas has a high exhaust temperature. It comes in contact with the gas. Therefore, the fuel can be atomized effectively, and if the exhaust gas temperature is high, a part of the fuel may burn, and most of the fuel diffuses and stays in the exhaust manifold together with the exhaust gas.

  Thus, in a state where the fuel is contained in the exhaust gas and diffused and stays in the exhaust manifold, the exhaust gas containing the fuel is discharged when the other cylinders exhaust the exhaust gas in the exhaust stroke. Will flow into the recirculation line. For this reason, unburned fuel is mixed in the intake air, which may impair the original exhaust gas recirculation effect.

  Therefore, the present invention aims to eliminate such problems.

  That is, the exhaust gas reducing agent injection control method according to the present invention includes a plurality of cylinders and a plurality of exhaust pipes each having a pipe collecting portion in which pipes communicating individually with the exhaust ports corresponding to the respective cylinders are gathered. A recirculation pipe for recirculating the exhaust gas to the intake system, communicating with the branch pipe and the exhaust multi-branch pipe, and exhausting a reducing agent for exhaust gas into the first part of the two parts sandwiching the pipe collecting portion In an internal combustion engine in which a reducing agent injection valve for injecting into a multi-branch pipe is provided and a reflux pipe is connected to a second part opposite to the first part, the exhaust gas is returned to the intake system. During execution, the reducing agent injection valve is operated when a cylinder located on the reflux line side of the pipe line collecting part is in the exhaust stroke.

  In the present invention, the reducing agent for exhaust gas may be a liquid containing HC, and specifically includes fuels such as gasoline and light oil. In this case, if the ease of supply is taken into consideration, it is necessary to match the fuel used in the internal combustion engine. That is, if the internal combustion engine is a spark ignition type fuel that uses gasoline as fuel, the exhaust gas reducing agent is gasoline, and if the internal combustion engine is a diesel engine that uses light oil as fuel, exhaust gas reduction. As the agent, light oil is applied.

  With this configuration, when the exhaust gas is recirculated to the intake system and the cylinder located on the recirculation line side of the exhaust manifold branch line is in the exhaust stroke in the operating state of the internal combustion engine, The exhaust gas reducing agent is injected into the exhaust multi-branch pipe from the reducing agent injection valve. The injected exhaust gas reducing agent is mixed into the exhaust gas and flows toward the pipe assembly of the exhaust multi-branch pipe. In this case, since the cylinder located closer to the reflux line than the line collection part is in the exhaust stroke, the exhaust gas discharged from this cylinder becomes a resistance against the exhaust gas that is about to flow into the return line. Therefore, it becomes possible to prevent the exhaust gas mixed with the reducing agent for exhaust gas that has become fine particles or atomized from flowing into the intake system.

  In order to more effectively prevent the exhaust gas mixed with the exhaust gas reducing agent from flowing into the intake system, the reducing agent injection valve is operated when the cylinder closest to the communication position of the reflux line is in the exhaust stroke. A configuration is preferred.

  Since the present invention is configured as described above, the exhaust gas reducing agent injected into the exhaust gas to reduce the exhaust gas in the operating state of the internal combustion engine that recirculates the exhaust gas to the intake system. Can be prevented from flowing into the intake system, and the exhaust gas reductant can reliably prevent the effect of exhaust gas recirculation from being reduced.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  This embodiment is applied to a multi-cylinder, for example, in-line four-cylinder diesel engine 100 having a turbocharger 1 as an internal combustion engine. The body 2 itself of the diesel engine 100 may be widely known in the field, and the reduction for injecting the turbocharger 1, the exhaust gas recirculation device 3, and the exhaust gas reducing agent to the body 2. It is provided with a reducing agent addition valve 4 and an exhaust gas purification device 5 which are agent injection valves.

  Specifically, the diesel engine 100 includes a main body 2 having a first cylinder 21 to a fourth cylinder 24 in series, and exhaust ports P1, P2, P3, and P4 corresponding to the first cylinder 21 to the fourth cylinder 24, respectively. An exhaust multi-branch pipe 6 in which the branch pipes 61, 62, 63, 64, which are individually communicating pipes, are gathered by a pipe gathering portion 65 constituting a connection end with the turbocharger 1, and each cylinder 21, An intake multi-branch pipe 7 communicating with the intake ports P5, P6, P7, P8 of 22, 23, and 24; a turbocharger 1 disposed between the exhaust multi-branch pipe 6 and the intake multi-branch pipe 7; An exhaust gas purifying device 5 for purifying exhaust gas discharged from the charger 1 and a reducing agent addition valve 4 attached to a first portion 66 of the exhaust multi-branch pipe 6 are provided.

  The main body 2 includes a fuel injection valve 8 that injects fuel directly into each of the first cylinder 21 and the fourth cylinder 24. In FIG. 1, for convenience of drawing, the fuel injection valve 8 is shown only in the fourth cylinder 24. An intake multi-branch pipe 7 constituting an intake system is attached to the main body 2, and a throttle body 8 having a throttle valve 81 is attached to the intake multi-branch pipe 7. An intake pipe IP having an intercooler 9 and connected to the outlet of the compressor 11 of the turbocharger 1 is connected to the throttle body 8. In addition, at a portion of the intake multi-branch pipe 7 on the side of the fourth cylinder 24, one of EGR pipes 32, which is a reflux pipe constituting the apparatus 3, via an EGR valve 31 constituting the exhaust gas recirculation apparatus 3. The ends are connected. An intake air pipe AP having an air cleaner AC is connected to the inlet of the compressor 12 of the turbocharger 1.

  Further, an exhaust multi-branch pipe 6 constituting an exhaust system is attached to the main body 2. In the exhaust multi-branch pipe 6, branch pipes 61, 62, 63, 64 connected to the cylinders 21, 22, 23, 24 are gathered at a pipe collecting portion 65. Since it is an inline 4-cylinder, the pipe collecting portion 65 is present at a position between the branch pipe 62 from the second cylinder 22 and the branch pipe 63 of the third cylinder 23 when viewed on a plane. It is. The exhaust multi-branch pipe 6 is configured such that exhaust gas is discharged to the outside of the exhaust multi-branch pipe 6, that is, to the turbocharger 1 from the pipe collecting portion 65. Therefore, the inlet of the turbine 12 of the turbocharger 1 is connected to the pipe line collecting portion 65. An exhaust gas purification device 5 is connected to the outlet of the turbine 12.

  The reducing agent addition valve 4 is attached to an end portion on the first cylinder 21 side which is the first portion 66 of the two portions sandwiching the pipe collecting portion 65 of the exhaust multi-branch pipe 6. In other words, the reducing agent addition valve 4 injects fuel, which is a reducing agent, toward the pipe collecting portion 65 toward the end portion located in the vicinity of the branch pipe 61 communicating with the exhaust port P1 of the first cylinder 21. It is attached to do. Since the reducing agent addition valve 4 injects fuel, it is connected to a fuel supply path (not shown) connected to each fuel injection valve 8.

  With respect to the arrangement of the reducing agent addition valve 4, the EGR pipe is connected to the second portion 67 in the direction opposite to the first portion 66 of the exhaust multi-branch pipe 6, that is, the end portion on the fourth cylinder 24 side. The other end of 32 is connected. With this structure, the exhaust multi-branch pipe 6 and the intake multi-branch pipe 7 are selectively communicated with each other via the EGR pipe 32 and the EGR valve 31. In addition, the connection part of the intake multi-branch pipe 7 and the EGR pipe 32 is not particularly restricted.

  The exhaust gas purification device 5 has a configuration in which an oxidation catalyst 51, a NOx occlusion reduction catalyst 52, and a diesel particulate filter 53 are arranged in series in a casing 54 with a space therebetween. As each of the catalysts 51 and 52 and the diesel particulate filter 53, those well known in the art can be widely used.

  An electronic control unit ECU for controlling the operation of the diesel engine 100 having such a configuration detects the operation state and controls the operation of at least the fuel injection valve 8, the reducing agent addition valve 4, and the EGR valve 31. To do. As shown in FIG. 2, the electronic control unit ECU is mainly composed of a microcomputer system including a central processing unit CPU, a storage device MEM, an input interface IIF, and an output interface OIF. Basically, the fuel injection control is executed in accordance with the operating state of the diesel engine 100, that is, the engine speed, the opening degree of the throttle valve 81, etc., and the operating state determined based on the detection result. It is. In this embodiment, in order to control the operation of the reducing agent addition valve 4, the input interface IIF has a cylinder discrimination signal output from the cam position sensor PS for detecting the rotational state of the diesel engine 100. A crank angle reference position signal and an engine speed signal are input. On the other hand, the output interface OIF outputs a fuel injection signal to the fuel injection valve 8, a reducing agent injection signal to the reducing agent addition valve 4, and an open / close signal to the EGR valve 31, respectively. ing. In FIG. 2, the basic sensors necessary for controlling the operation of the diesel engine 100 may be the same as those in the field, and thus illustration and description thereof are omitted.

  In the above configuration, the reducing agent addition valve 4 performs an exhaust gas recirculation operation in which a part of the exhaust gas is recirculated (recirculated) to the intake system, specifically, the intake multi-branch pipe 7. Are controlled as described below. When the exhaust gas recirculation operation is being performed, the EGR valve 31 is opened according to the operating state of the diesel engine 100. Usually, the diesel engine 00 is in a transient operation due to acceleration or the like, or in an idling operation. If there is, it will be closed.

  On the other hand, the reducing agent addition valve 4 is operated when a cylinder located closer to the EGR pipe 32 than the pipe collecting portion 65 of the exhaust multi-branch pipe 6 is in the exhaust stroke. In this embodiment, the pipe collecting portion 65 is located at substantially the center in the lateral direction of the exhaust multi-branch pipe 5 in plan view, and as described above, the first cylinder 21 side first side is located. Since the reducing agent addition valve 4 is attached to the part 66 and the EGR pipe 32 is connected to the second part 67 on the fourth cylinder 24 side, the third cylinder 23 or the fourth cylinder 24 is in the exhaust stroke. The reducing agent addition valve 4 is operated. In this embodiment, the case where the third cylinder 23 is in the exhaust stroke will be described.

  Drive control of the reducing agent addition valve 4, in other words, fuel injection control will be described with reference to FIG. This injection control is executed when the exhaust gas recirculation operation is executed, that is, when the EGR valve 31 is opened at an opening degree corresponding to the operating state. When the valve is closed, unlike the injection control described below, the reducing agent addition valve 4 is actuated (driven) to inject fuel at the set cycle in the set operating state. Is. Therefore, the execution of the exhaust gas recirculation operation is detected (determined) based on the output of the control signal of the EGR valve 31. In the diesel engine 100 of this embodiment, for example, the exhaust stroke is executed in the order of the first cylinder 21, the third cylinder 23, the fourth cylinder 24, and the second cylinder 22.

  First, in step S1, it is determined based on the cylinder discrimination signal and the crank angle reference position signal whether the third cylinder 23 is in the exhaust stroke (determination condition). If it is determined in step S1 that the third cylinder 23 is in the exhaust stroke, a drive signal is output to the reducing agent addition valve 4 in step S2 to operate the reducing agent addition valve 4. On the other hand, if it is determined in step S1 that the third cylinder 23 is not in the exhaust stroke, step S1 is repeatedly executed. In step S3, it is determined whether or not the EGR valve 31 is open. If the result of the determination is open, the process returns to step S1, and if it is determined that it is not open, that is, closed, this control is terminated.

  When the diesel engine 100 is started and the EGR valve 31 is opened and the exhaust gas recirculation operation is executed, injection control of the fuel that is the exhaust gas reducing agent is executed. And when the 1st cylinder 21, the 2nd cylinder 22, and the 4th cylinder 24 are exhaust strokes, since it differs from the determination conditions in step S1, step S1 is performed again. When it is determined in step S1 that the third cylinder 23 has reached the exhaust stroke, the reducing agent addition valve 4 is operated in step S2 to inject fuel into the exhaust multi-branch pipe 6.

  The injected fuel mixes with the exhaust gas staying in the exhaust multi-branch 6 and diffuses toward the inside of the exhaust multi-branch 6, and part of it burns. In this case, since the third cylinder 23 is in the exhaust stroke, the exhaust gas is jetted into the exhaust multi-branch pipe 6 from the branch pipe 63 communicating with the exhaust port P3 of the third cylinder 23. As a result, the discharged exhaust gas acts like a wall made of gas between the reducing agent addition valve 4 and the second portion 67 that is the connection portion of the EGR pipe 32, and the exhaust gas mixed with fuel. Is prevented from flowing into the EGR pipe 32. That is, most of the exhaust gas mixed with fuel moves toward the pipe collecting portion 65, but a part of the exhaust gas is transferred from the first cylinder 21 to the fourth by the EGR valve 31 being opened. It tries to move in the direction of the cylinder 24, that is, toward the connection part of the EGR pipe 32, but the movement is blocked by the exhaust gas layer formed by the exhaust gas ejected from the branch pipe 63 of the third cylinder 23 or the exhaust gas flow. It will be.

  Therefore, even when the exhaust gas recirculation operation is being performed, the fuel can be appropriately injected into the exhaust gas in accordance with the state of the exhaust gas purification device 5. Further, since the reducing agent addition valve 4 is driven in the exhaust stroke of the third cylinder 23, the fuel is repeatedly injected during execution of the exhaust gas recirculation operation at a predetermined interval as long as the engine speed is the same. can do. As a result, the catalysts 51 and 52 of the exhaust gas purification device 5 can be reduced without impeding the combustion effect due to the exhaust gas recirculation, and the exhaust gas purification ability can be reliably prevented from being lowered. .

  In this embodiment, since fuel is used as the reducing agent for exhaust gas, the fuel injected from the reducing agent addition valve 4 burns at the temperature of the exhaust gas in the exhaust multi-branch pipe 6. There is. As described above, when at least a part of the injected fuel burns and the temperature of the exhaust gas rises, the temperature in the exhaust gas purification device 5 can be raised. For this reason, the temperature of each catalyst 51, 52 of the exhaust gas purification device 5 can be raised, and for example, after the start, each catalyst 51, 52 can be activated early.

  In the above embodiment, the description has been given of the case where the reducing agent addition valve 4 is operated when the third cylinder 23 is in the exhaust stroke, but instead of the third cylinder 23, the connection portion of the EGR pipe 32 is provided. The reducing agent addition valve 4 may be operated when the fourth cylinder 24 which is the closest cylinder is in the exhaust stroke. Even in this case, the exhaust gas wall (exhaust gas flow) is formed in the exhaust multi-branch pipe 6 by the exhaust gas ejected from the branch pipe 64 communicating with the exhaust port P4 of the fourth cylinder 24. The exhaust gas mixed with the exhaust gas reducing agent (fuel) can be reliably suppressed from flowing into the EGR pipe 32.

  Further, in the above embodiment, the exhaust multi-branch pipe 6 in which the pipe collecting portion 65 is provided at a position approximately in the middle of the branch pipes 62 and 63 of the second cylinder 22 and the third cylinder 23 has been described. As long as at least the branch pipe 64 corresponding to the fourth cylinder 24 is located closer to the connection part of the EGR pipe 32 than the pipe collecting part 65 suffices.

  Furthermore, in the above embodiment, the in-line four-cylinder diesel engine 100 has been described. However, in-line three-cylinder, in-line five-cylinder, in-line six-cylinder diesel engines, and such in-line multi-cylinders are arranged in parallel. The present invention may be applied to a V-type diesel engine or a horizontally opposed diesel engine. Even in such an odd-numbered cylinder engine, the exhaust multi-branch pipe may have a structure in which the branch pipe of the cylinder closest to the EGR pipe connection part is positioned closer to the EGR pipe connection part than the pipe assembly portion. That's fine.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows schematic structure of embodiment of this invention. The block diagram which shows schematic structure of the electronic control apparatus of the embodiment. The flowchart which shows the outline of the control procedure of the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Diesel engine 4 ... Reductant addition valve 6 ... Exhaust multi-branch pipe 7 ... Intake multi-branch pipe 21 ... 1st cylinder 22 ... 2nd cylinder 23 ... 3rd cylinder 24 ... 4th cylinder 32 ... EGR pipe 65 ... Pipe line Aggregation part 66 ... first part 67 ... second part

Claims (2)

Provided with a plurality of cylinders and an exhaust multi-branch pipe and a multi-exhaust multi-branch pipe having a pipe collecting section in which pipes communicating individually with the exhaust ports corresponding to the respective cylinders are gathered into the intake system. And a reductant injection valve for injecting a reducing agent for exhaust gas into the exhaust multi-branch pipe at the first part of the two parts sandwiching the pipe assembly. In the internal combustion engine in which the reflux line is communicated with the second part in the opposite direction to the part,
An exhaust gas reductant injection control method for operating a reductant injection valve when a cylinder located closer to the recirculation line than the line collection part is in an exhaust stroke during recirculation of exhaust gas to the intake system.   2. The exhaust gas reducing agent injection control method according to claim 1, wherein the reducing agent injection valve is operated when the cylinder closest to the communication position of the reflux line is in the exhaust stroke.

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