JP2011231681A - Exhaust system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust system for an internal combustion engine, in which thermoacoustic effect by a thermoacoustic stock that is disposed in an exhaust branch pipe is sufficiently exerted in a wide range of engine speed.SOLUTION: The exhaust system for the internal combustion engine includes: the exhaust branch pipe having one end thereof communicating to an exhaust passage of the internal combustion engine and the other end being closed; a pipe length changer for varying the length of the exhaust branch pipe; a thermoacoustics stack disposed in the exhaust branch pipe, for converting the energy of air column vibration in the exhaust branch pipe into heat energy; and a controller for resonance control to vary the pipe length by the pipe length changer based on the engine speed of the internal combustion engine, so that the pipe length has a length that allows the air column in the exhaust branch pipe to resonate.

Description

  The present invention relates to an exhaust system for an internal combustion engine.

  Japanese Patent Application Laid-Open No. 2007-154792 discloses an air column that is generated when a thermoacoustic stack is disposed inside an exhaust branch pipe having one end communicating with an exhaust passage of an internal combustion engine and the other end closed, and receiving exhaust pulsation of the internal combustion engine. An energy recovery device is disclosed in which vibration energy is converted into thermal energy by a thermoacoustic stack and recovered.

JP 2007-154792 A

  In order to efficiently convert air column vibration energy into heat energy by the thermoacoustic stack, it is necessary to resonate the air column in the pipe. The frequency at which the air column resonates is a predetermined value determined by the pipe length and the like. On the other hand, the frequency of the exhaust pulsation changes according to the engine speed. For this reason, the above-described conventional apparatus has a problem that a sufficient effect can be obtained only in a narrow engine rotational speed range in which the exhaust pulsation frequency is close to the predetermined resonance frequency of the exhaust branch pipe.

  The present invention has been made in view of the above points, and is an exhaust system for an internal combustion engine that can sufficiently exhibit the thermoacoustic effect of the thermoacoustic stack disposed in the exhaust branch pipe in a wide engine rotational speed range. The purpose is to provide.

In order to achieve the above object, a first invention is an exhaust system for an internal combustion engine,
An exhaust branch pipe with one end communicating with the exhaust passage of the internal combustion engine and the other end closed;
Conduit length varying means for varying the conduit length of the exhaust branch pipe;
A thermoacoustic stack disposed in the exhaust branch pipe and capable of converting energy of air column vibration in the exhaust branch pipe into thermal energy;
Control for performing resonance control in which the pipe length is changed by the pipe length varying means based on the rotational speed of the internal combustion engine so that the pipe length becomes a length at which the air column in the exhaust branch pipe resonates. Means,
It is characterized by providing.

The second invention is the first invention, wherein
At least a part of the exhaust branch pipe can function as an EGR passage for performing EGR for recirculating exhaust gas of the internal combustion engine to an intake system,
An EGR catalyst for purifying the recirculated exhaust gas is installed in the middle of the exhaust branch pipe,
A rise in the bed temperature of the EGR catalyst is suppressed by executing the resonance control when the EGR is not being executed.

  According to the first aspect, the pipe length of the exhaust branch pipe in which the thermoacoustic stack is arranged can be changed based on the rotational speed of the internal combustion engine. For this reason, the thermoacoustic effect by a thermoacoustic stack can fully be exhibited in a wide engine-speed range.

  According to 2nd invention, when EGR is not performed, the raise of the bed temperature of an EGR catalyst can be suppressed by the thermoacoustic effect by a thermoacoustic stack.

It is a figure for demonstrating the exhaust system of Embodiment 1 of this invention. It is a figure which shows the structure of a pipe line switching valve, an EGR passage, and a bypass passage. It is a figure which shows a state in case EGR is stopping and an engine speed is high. It is a figure which shows a state in case EGR is being stopped and an engine speed is medium. It is a figure which shows a state when EGR is stopping and an engine speed is low. It is a figure which shows a state in case EGR is stopping and the air column in a pipe line is not resonated. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the exhaust system of Embodiment 2 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining an exhaust system according to Embodiment 1 of the present invention. An internal combustion engine 10 shown in FIG. 1 is an in-line four-cylinder internal combustion engine mounted on a vehicle or the like. However, the number of cylinders and the cylinder arrangement of the internal combustion engine in the present invention are not limited to this. Although not shown, each cylinder of the internal combustion engine 10 is provided with a piston, an intake valve, an exhaust valve, and the like.

  An intake passage 14 is connected to the intake side of the internal combustion engine 10 via an intake manifold 12. A throttle valve 16 for adjusting the intake air amount and a fuel injector 18 for injecting fuel are installed in the intake passage 14. The configuration is not limited to the illustrated configuration, and a fuel injector may be provided for each cylinder, and fuel may be injected into the intake port or cylinder of each cylinder.

  An exhaust passage 22 is connected to the exhaust side of the internal combustion engine 10 via an exhaust manifold 20. An exhaust purification catalyst 24 for purifying exhaust gas is installed in the middle of the exhaust passage 22. From the exhaust passage 22 between the exhaust manifold 20 and the exhaust purification catalyst 24, an EGR passage 26 for performing EGR (Exhaust Gas Recirculation) for recirculating a part of the exhaust gas to the intake side is branched. An EGR catalyst 28 for purifying exhaust gas that recirculates (hereinafter referred to as “EGR gas”) is installed in the middle of the EGR passage 26.

  The other end of the EGR passage 26 is connected to the pipeline switching valve 30. One end of the EGR passage 32 and one end of a bypass passage 34 longer than the EGR passage 32 are further connected to the pipe switching valve 30. The other end of the EGR passage 32 and the other end of the bypass passage 34 are connected to a pipe switching valve 36. One end of an EGR passage 38 is further connected to the pipe switching valve 36. The other end of the EGR passage 38 is connected to the intake passage 14. An EGR cooler 40 for cooling EGR gas and an EGR valve 42 for adjusting the exhaust gas recirculation amount are installed in the middle of the EGR passage 38.

  The system of the present embodiment further includes an ECU (Electronic Control Unit) 50 that controls the operation of various actuators including the throttle valve 16, the fuel injector 18, the pipe switching valves 30, 36, and the EGR valve 42, and an internal combustion engine. And a crank angle sensor 48 that outputs a signal synchronized with the rotation of the crankshaft of the engine 10. The ECU 50 can detect the crank angle and the engine speed based on the output of the crank angle sensor 48.

  Although not shown, the system of the present embodiment includes an air flow meter that detects the intake air amount, a vehicle speed sensor that detects the speed of the vehicle, an accelerator position sensor that detects the amount of operation of the accelerator pedal by the driver of the vehicle, and the like. It is equipped with various sensors. The ECU 50 controls the operation of the internal combustion engine 10 by detecting engine operation information using the sensors described above and driving the actuators based on the detection results. In particular, in the present embodiment, the ECU 50 executes EGR by opening the EGR valve 42 in a predetermined operation region. During the execution of EGR, the EGR rate is controlled by controlling the opening degree of the EGR valve 42. On the other hand, the EGR valve 42 is closed in the operation region where EGR is not executed.

  FIG. 2 is a diagram showing the configuration of the pipeline switching valves 30, 36, the EGR passage 32 and the bypass passage 34. As shown in FIG. 2, a thermoacoustic stack 44 is installed inside the EGR passage 32. Further, a thermoacoustic stack 46 is installed inside the end portion of the bypass passage 34 on the pipe switching valve 36 side. The thermoacoustic stacks 44 and 46 are members having a large number of pores (small diameter passages), and for example, a metal mesh made of stainless steel or the like can be preferably used. The thermoacoustic stacks 44 and 46 have a function of converting air column vibration energy (sonic energy) into thermal energy by a thermoacoustic effect. That is, heat is transferred between the gas flowing in the pores of the thermoacoustic stacks 44 and 46 by the vibration of the air column in the pipelines and the wall surfaces of the pores, so that heat is generated along the axial direction of the pipelines. A temperature gradient is generated in the acoustic stacks 44, 46.

  FIG. 2 shows a state when the EGR is being executed. When EGR is being executed, the ECU 50 controls the pipe switching valves 30 and 36 to the state shown in FIG. That is, the pipeline switching valve 30 is in a state in which the EGR passage 26, the EGR passage 32, and the bypass passage 34 are in communication, and the pipeline switching valve 36 is in a state in which the EGR passage 32, the bypass passage 34, and the EGR passage 38 are in communication. Is done. During execution of EGR, as indicated by an arrow in FIG. 2, the EGR gas from the EGR passage 26 can escape through the EGR passage 32 to the EGR passage 38. Further, a part of the EGR gas flows to the EGR passage 38 via the bypass passage 34.

  When the EGR is stopped, the EGR valve 42 is closed, so that EGR gas does not flow through the EGR catalyst 28. However, according to experiments conducted by the present inventors, it has been found that even when the EGR is stopped, the bed temperature of the EGR catalyst 28 may rise excessively and exceed the reference temperature for preventing catalyst deterioration and the like. (Especially during high loads with large intake air volume). The cause of the excessive rise in the bed temperature of the EGR catalyst 28 during EGR stoppage is not necessarily clear, but one reason is that exhaust gas is exhausted due to exhaust pulsation in the exhaust passage 22 even during EGR stoppage. As a result of repeatedly entering and leaving the EGR catalyst 28, it is considered that a catalytic reaction occurs and the bed temperature rises.

  As a result of intensive studies to prevent an excessive increase in the bed temperature of the EGR catalyst 28 while the EGR is stopped, the present inventors have found that a method of arranging a thermoacoustic stack in the EGR passage is effective. . While the EGR is stopped, the air column in the EGR passage vibrates in response to the exhaust pulsation in the exhaust passage 22. For this reason, in the thermoacoustic stack arranged in the EGR passage, the energy of the air column vibration is converted into thermal energy by the thermoacoustic effect, and a temperature gradient is generated. In this way, the energy received by the EGR catalyst 28 is reduced by absorbing the energy of the air column vibration in the EGR passage by the thermoacoustic stack, so that an increase in the bed temperature of the EGR catalyst 28 can be suppressed.

  In order to fully exhibit the thermoacoustic effect by the thermoacoustic stack, it is necessary to resonate the air column (generate a standing wave). The frequency at which the air column in the pipeline resonates is determined by the length of the pipeline and the presence or absence of branching. For this reason, normally, the resonance frequency of the air column in the EGR passage is a predetermined value determined by the length of the EGR passage and the like. In order for the air column in the EGR passage to resonate, the resonance frequency and the exhaust pulsation frequency must be close to each other. The frequency of exhaust pulsation is determined by the engine speed. Therefore, in the case of a configuration in which the thermoacoustic stack is simply arranged in the EGR passage, it must be within a predetermined engine rotation speed range in which the resonance frequency of the air column in the EGR passage and the exhaust pulsation frequency are close to each other. The thermoacoustic effect by a thermoacoustic stack is not fully demonstrated. For this reason, there is a problem in that the increase in the bed temperature of the EGR catalyst 28 cannot be sufficiently suppressed in other engine rotation speed ranges.

  On the other hand, the exhaust system of the present embodiment is configured to change the resonance frequency of the air column in the duct by making the length of the duct where the thermoacoustic stack is located variable. Yes. Then, by changing the pipe length according to the engine rotational speed so that the resonance frequency and the exhaust pulsation frequency are close to each other, the thermoacoustic effect can be sufficiently exhibited in a wide engine rotational speed range. Hereinafter, this point will be described with reference to FIGS.

  FIG. 3 is a diagram showing a state where the EGR is stopped and the engine speed is high. When the EGR is stopped and the engine rotation speed is in a relatively high range (hereinafter referred to as “high rotation range”), the ECU 50 sets the pipe switching valves 30 and 36 to the state shown in FIG. Control. That is, in this case, the pipeline switching valve 30 is in a state in which the EGR passage 26 and the EGR passage 32 are communicated to close the bypass passage 34. Further, the pipeline switching valve 36 is in a state of closing the EGR passage 32 (in the illustrated configuration, the bypass passage 34 and the EGR passage 38 are simultaneously closed). In this state, the EGR passage 26 and the EGR passage 32 are connected as a pipeline through the pipeline switching valve 30. This pipe length is set to such a length that the resonance frequency is close to the exhaust pulsation frequency in the high rotation range. Therefore, the air column in the pipeline formed by connecting the EGR passage 26 and the EGR passage 32 via the pipeline switching valve 30 resonates due to the exhaust pulsation, and a standing wave is generated. A thermoacoustic stack 44 is located near the closed end of the conduit. Generally, the thermoacoustic effect can be sufficiently exhibited by arranging the thermoacoustic stack near the closed end. Therefore, in the state shown in FIG. 3, the energy of the air column vibration is efficiently absorbed by the thermoacoustic stack 44 and converted into thermal energy, and a temperature gradient is generated in the thermoacoustic stack 44. As a result, the energy received by the EGR catalyst 28 is reduced, so that an increase in the bed temperature of the EGR catalyst 28 can be reliably suppressed.

  FIG. 4 is a diagram illustrating a state where the EGR is stopped and the engine speed is medium. When the EGR is stopped and the engine rotation speed is in a medium range (hereinafter referred to as “medium rotation range”), the ECU 50 sets the pipe switching valves 30 and 36 to the state shown in FIG. Control. That is, in this case, the pipeline switching valve 30 is in a state where the EGR passage 26 and the bypass passage 34 are connected to close the EGR passage 32. Further, the pipeline switching valve 36 is in a state of closing the bypass passage 34 (in the configuration shown, the EGR passage 32 and the EGR passage 38 are simultaneously closed). In this state, the EGR passage 26 and the bypass passage 34 are connected as a pipeline through the pipeline switching valve 30. For this reason, in this state, the pipe length becomes longer than the state shown in FIG. This pipe length is set to such a length that the resonance frequency is close to the exhaust pulsation frequency in the middle rotation range. Therefore, the air column in the pipeline formed by connecting the EGR passage 26 and the bypass passage 34 via the pipeline switching valve 30 resonates due to the exhaust pulsation, and a standing wave is generated. A thermoacoustic stack 46 is located near the closed end of the conduit. For this reason, in the state shown in FIG. 4, the energy of the air column vibration is efficiently absorbed by the thermoacoustic stack 46 and converted into thermal energy, and a temperature gradient is generated in the thermoacoustic stack 46. As a result, the energy received by the EGR catalyst 28 is sufficiently reduced, and an increase in the bed temperature of the EGR catalyst 28 can be reliably suppressed.

  FIG. 5 is a diagram illustrating a state where the EGR is stopped and the engine speed is low. When the EGR is stopped and the engine rotation speed is in a relatively low range (hereinafter referred to as “low rotation range”), the ECU 50 sets the pipe switching valves 30 and 36 to the state shown in FIG. Control. That is, in this case, the pipeline switching valve 30 is in a state where the EGR passage 26 and the bypass passage 34 are connected to close the EGR passage 32. Further, the pipe switching valve 36 is in a state in which the bypass passage 34 and the EGR passage 32 are communicated to close the EGR passage 38. In this state, the EGR passage 26, the bypass passage 34, and the EGR passage 32 are connected as a pipe line via the pipe switching valve 30 and the pipe switching valve 36. For this reason, in this state, the pipe line length becomes longer than the state shown in FIG. This pipe length is set to such a length that the resonance frequency is close to the exhaust pulsation frequency in the low rotation range. Therefore, the air column in the pipeline formed by connecting the EGR passage 26, the bypass passage 34, and the EGR passage 32 via the pipeline switching valve 30 and the pipeline switching valve 36 resonates due to exhaust pulsation, and standing waves are generated. appear. A thermoacoustic stack 44 is located near the closed end of the conduit. Therefore, in the state shown in FIG. 5, the energy of the air column vibration is efficiently absorbed by the thermoacoustic stack 44 and converted into thermal energy, and a temperature gradient is generated in the thermoacoustic stack 44. As a result, the energy received by the EGR catalyst 28 is sufficiently reduced, and an increase in the bed temperature of the EGR catalyst 28 can be reliably suppressed.

  According to the present embodiment, when the EGR is stopped as described above, the thermoacoustic effect by the thermoacoustic stack 44 or 46 is sufficiently obtained in any of the high rotation region, the medium rotation region, and the low rotation region. Since it can be exhibited, an increase in the bed temperature of the EGR catalyst 28 can be reliably suppressed.

  FIG. 6 is a diagram illustrating a state where the EGR is stopped and the air column in the pipeline is not resonated. In this case, the pipe switching valve 30 is in a state where the EGR passage 26, the EGR passage 32, and the bypass passage 34 are communicated with each other. Further, the pipe switching valve 36 is in a state in which the bypass passage 34 and the EGR passage 32 are communicated to close the EGR passage 38. In this state, since the EGR passage 32 and the bypass passage 34 form a loop through the pipe switching valve 30 and the pipe switching valve 36, the closed end is not formed. For this reason, the air column in the pipeline does not resonate. When the bed temperature of the EGR catalyst 28 is low and the bed temperature of the EGR catalyst 28 needs to be raised, the ECU 50 may control the pipe switching valves 30 and 36 to the state shown in FIG.

  In the present embodiment, there are the following advantages during execution of EGR. During EGR, EGR gas flows through the thermoacoustic stacks 44 and 46 as shown in FIG. For this reason, heat dissipation improves and the temperature of EGR gas can be lowered more.

  FIG. 7 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above-described function. According to the routine shown in FIG. 7, it is first determined whether or not the EGR valve 42 is closed, that is, whether or not the EGR is stopped (step 100). If it is determined that the EGR valve 42 is closed (EGR is stopped), next, whether the engine speed is in the high, medium or low speed range. Judgment is made (step 102).

  If it is determined in step 102 that the engine speed is in the high speed range, the pipe switching valves 30 and 36 are controlled to the state shown in FIG. As a result, the pipe length is shortened and the resonance frequency is increased, so that the resonance frequency becomes close to the exhaust pulsation frequency in the high rotation range. For this reason, the air column in the pipe can be resonated to sufficiently exhibit the thermoacoustic effect by the thermoacoustic stack 44, and the rise in the bed temperature of the EGR catalyst 28 can be reliably suppressed.

  On the other hand, if it is determined in step 102 that the engine speed is in the middle rotation range, the pipe switching valves 30 and 36 are controlled to the state shown in FIG. As a result, the pipe length becomes medium and the resonance frequency becomes medium, so that the resonance frequency becomes close to the exhaust pulsation frequency in the middle rotation range. For this reason, the air column in the pipe line can be resonated to sufficiently exhibit the thermoacoustic effect by the thermoacoustic stack 46, and the rise in the bed temperature of the EGR catalyst 28 can be reliably suppressed.

  If it is determined in step 102 that the engine speed is in the low speed range, the pipe switching valves 30 and 36 are controlled to the state shown in FIG. As a result, the pipe length becomes longer and the resonance frequency becomes lower, so that the resonance frequency becomes close to the exhaust pulsation frequency in the low rotation range. For this reason, the air column in the pipe can be resonated to sufficiently exhibit the thermoacoustic effect by the thermoacoustic stack 44, and the rise in the bed temperature of the EGR catalyst 28 can be reliably suppressed.

  Although omitted in this embodiment, a heat exchanger is provided at one or both ends of the thermoacoustic stacks 44 and 46 to circulate the heat medium, and the heat medium is generated by the temperature gradient generated in the thermoacoustic stacks 44 and 46. May be configured to be heated or cooled. Further, the heated or cooled heat medium may be circulated through a heat exchanger for exchanging heat with the object, and the object may be heated or cooled.

  In the first embodiment described above, the EGR passage 26, the pipeline switching valve 30, the EGR passage 32, the bypass passage 34, and the pipeline switching valve 36 are the "exhaust branch pipe" and the "variable pipe length" in the first invention. It corresponds to “means”. Further, the “control means” according to the first aspect of the present invention is realized by the ECU 50 executing the processes of steps 102, 104, 106 and 108 described above.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 8. The description will focus on the differences from the first embodiment described above, and the same matters will be simplified or described. Omitted. FIG. 8 is a diagram for explaining the exhaust system according to the second embodiment of the present invention.

  As shown in FIG. 8, in the exhaust system of the present embodiment, an EGR passage 26 branched from the exhaust passage 22 is connected to the intake passage 14. A first EGR valve 52, a second EGR valve 54, and a third EGR valve 56 are arranged in this order in the middle of the EGR passage 26 and downstream of the EGR catalyst 28. A thermoacoustic stack 58 is disposed adjacent to the upstream side of the first EGR valve 52. A thermoacoustic stack 60 is disposed adjacent to the upstream side of the second EGR valve 54. Further, a thermoacoustic stack 62 is disposed adjacent to the upstream side of the third EGR valve 56.

  When executing EGR, the first EGR valve 52, the second EGR valve 54, and the third EGR valve 56 are all opened. The amount of EGR is controlled by adjusting the opening degree of one of them (usually, the third EGR valve 56).

  While EGR is stopped, the following control is performed. In the high rotation range, the first EGR valve 52 is closed. The second EGR valve 54 and the third EGR valve 56 may be open or closed. In the state where the first EGR valve 52 is closed, the length of the pipe line including the EGR catalyst 28 becomes shorter and the resonance frequency becomes higher, so that the resonance frequency becomes close to the exhaust pulsation frequency in the high rotation range. For this reason, it is possible to resonate the air column in the pipe line and to sufficiently exert the thermoacoustic effect by the thermoacoustic stack 58 located in the vicinity of the closed end of the pipe line, and to reliably increase the bed temperature of the EGR catalyst 28. Can be suppressed.

  In the middle rotation range, the first EGR valve 52 is opened and the second EGR valve 54 is closed. The third EGR valve 56 may be open or closed. In the state where the first EGR valve 52 is opened and the second EGR valve 54 is closed, the length of the pipe line including the EGR catalyst 28 becomes medium and the resonance frequency becomes medium. Close to the exhaust pulsation frequency. For this reason, it is possible to resonate the air column in the pipe line and to sufficiently exert the thermoacoustic effect by the thermoacoustic stack 60 located near the closed end of the pipe line, and to reliably increase the bed temperature of the EGR catalyst 28. Can be suppressed.

  In the low rotation range, the first EGR valve 52 and the second EGR valve 54 are opened, and the third EGR valve 56 is closed. In the state where the first EGR valve 52 and the second EGR valve 54 are opened and the third EGR valve 56 is closed, the length of the pipe line including the EGR catalyst 28 becomes long and the resonance frequency becomes low. It becomes close to the exhaust pulsation frequency. For this reason, the air column in the pipe line can be resonated so that the thermoacoustic effect by the thermoacoustic stack 62 located in the vicinity of the closed end of the pipe line can be sufficiently exerted, and the rise in the bed temperature of the EGR catalyst 28 is ensured. Can be suppressed.

  Since Embodiment 2 is the same as Embodiment 1 except for the points described above, further description is omitted. In the second embodiment, the EGR passage 26, the first EGR valve 52, the second EGR valve 54, and the third EGR valve 56 correspond to the “exhaust branch pipe” and the “pipe length variable means” in the first invention. .

  In Embodiments 1 and 2 described above, the configuration in which the thermoacoustic stack is disposed in the EGR passage has been described as an example. However, in the present invention, the thermoacoustic stack is disposed in the exhaust branch pipe other than the EGR passage. It is also applicable to.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake manifold 14 Intake passage 16 Throttle valve 20 Exhaust manifold 22 Exhaust passage 24 Exhaust purification catalyst 26, 32, 38 EGR passage 28 EGR catalyst 30 Pipe line switching valve 34 Bypass path 36 Pipe line switching valve 42 EGR valve 44, 46 Thermoacoustic stack 52 1st EGR valve 54 2nd EGR valve 56 3rd EGR valve 58, 60, 62 Thermoacoustic stack

Claims (2)

An exhaust branch pipe with one end communicating with the exhaust passage of the internal combustion engine and the other end closed;
Conduit length varying means for varying the conduit length of the exhaust branch pipe;
A thermoacoustic stack disposed in the exhaust branch pipe and capable of converting energy of air column vibration in the exhaust branch pipe into thermal energy;
Control for performing resonance control in which the pipe length is changed by the pipe length varying means based on the rotational speed of the internal combustion engine so that the pipe length becomes a length at which the air column in the exhaust branch pipe resonates. Means,
An exhaust system for an internal combustion engine, comprising: At least a part of the exhaust branch pipe can function as an EGR passage for performing EGR for recirculating exhaust gas of the internal combustion engine to an intake system,
An EGR catalyst for purifying the recirculated exhaust gas is installed in the middle of the exhaust branch pipe,
The exhaust system for an internal combustion engine according to claim 1, wherein an increase in the bed temperature of the EGR catalyst is suppressed by executing the resonance control when the EGR is not executed.

Images