JP2000130269A - Catalyst bult-in muffler of engine with exhaust gas recirculating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR cooler from being clogged with soot in exhaust gas without enlarging the EGR cooler. SOLUTION: Exhaust gas is returned to an intake passage for recirculation through an EGR pipe 12 and an EGR cooler by an exhaust gas recalculation device 11. A cylindrical muffler main body 19 is provided on the way of an exhaust pipe 18, and a catalyst 23 is provided inside the muffler main body. The catalyst purifies exhaust gas, and an outlet chamber 27 for allowing purified exhaust gas to flow is formed inside the muffler main body. An EGR gas intake 19a is formed on the peripheral wall of the muffler main body so as to face the outlet chamber, and an exhaust gas introducing part 12a of the EGR pipe is connected to the intake. The exhaust gas introducing part of the EGR pipe is inserted from the EGR gas intake to the outlet chamber, and it is preferable that the end of the exhaust gas introducing part is bent toward the catalyst at a specified radius of curvature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffler for suppressing exhaust noise of an engine having an exhaust gas recirculation device. More specifically, the present invention relates to a muffler in which a catalyst is provided.

[0002]

2. Description of the Related Art Conventionally, as an exhaust gas recirculation device, as shown in FIG. 7, an exhaust pipe 1a and an intake pipe 1b of an engine 1 are communicatively connected by an EGR pipe 2, and the exhaust gas flowing through the EGR pipe 2 is connected to the EGR pipe 2. EGR to adjust flow rate
A valve 4 is provided.
There is known an EGR pipe 2 on which an EGR cooler 3 is provided. The inlet end of the EGR pipe 2 is connected to the exhaust pipe 1a immediately after the exhaust manifold 1c, and the outlet end of the EGR pipe 2 is connected to the intake pipe 1b just before the intake manifold 1d.
Connected to. The EGR valve 4 includes a valve case 4a for slidably holding an umbrella type valve (not shown) for opening and closing the EGR pipe 2, and a diaphragm 4 for holding the umbrella type valve.
b for accommodating the diaphragm b.
Although not shown, the inside of the diaphragm case 4c is partitioned into an atmospheric pressure chamber and a compressed air supply / discharge chamber by the diaphragm 4b.
The compressed air supply / discharge chamber is connected to an air tank 7 through an air pipe 6. In the middle of the air line 6, there is provided an inflow adjusting valve 8 for adjusting the amount of compressed air flowing into the compressed air supply / discharge chamber.

The EGR cooler 3 is a water-cooled heat exchanger, and has a cylindrical cooler body 3a having both ends closed, and the cooler body 3a is connected to an inlet gas chamber 3b, a cooling water chamber 3c and an outlet gas chamber. 3d, a pair of cooling water partition plates 3e,
3e, a pair of cooling water partition plates 3 inserted through the cooling water chamber 3c.
e, 3e, and has many thin tubes 3f whose both ends communicate with the inlet gas chamber 3b and the outlet gas chamber 3d. The inlet side gas chamber 3b is connected to the EGR pipe 2 on the exhaust pipe 1a side.
And the outlet side gas chamber 3d is connected to the E on the side of the intake pipe 1b.
Connected to GR pipe 2. The cooling water chamber 3c is configured to allow engine cooling water to pass through. This cooler 3
Thus, the exhaust gas flowing from the EGR pipe 2 into the thin tube 3f is cooled by the engine cooling water, and the density of the exhaust gas returned to the intake pipe 1b is increased.

On the other hand, the engine 1 is provided with a rotation sensor 9a for detecting the rotation speed of the crankshaft of the engine, and the fuel injection pump is provided with a load sensor 9b for detecting the load on the engine 1 based on the position of the control rack. . The control input of the controller 5 is connected to the respective detection outputs of the rotation sensor 9a and the load sensor 9b, and the control output of the controller 5 is connected to the inflow control valve 8. Further, the controller 5 is provided with a memory (not shown), and the memory stores an optimal change in the opening degree of the inflow amount adjusting valve 8 with respect to a change in the rotation speed and load of the engine 1 as a map.

[0005] In the exhaust gas recirculation device configured as described above, when the engine 1 is running at medium speed and medium load, the controller 5 compares each detection output of the rotation sensor 9a and the load sensor 9b with the map stored in the memory. To turn on the inflow control valve 8. As a result, a sufficient amount of exhaust gas can be supplied to the intake pipe 1b, so that the temperature of the combustion gas in the combustion chamber of the engine 1 decreases, the reaction between nitrogen and oxygen is suppressed, and the emission of NOx can be reduced. On the other hand, during continuous full-load running (uphill) or high-speed steady running of the engine 1, the controller 5 compares the detection outputs of the rotation sensor 9 a and the load sensor 9 b and a map of the memory and calculates the inflow amount adjusting valve 8. Turn off. Thus, the inflow of exhaust gas into the engine 1 requiring a relatively large amount of air can be stopped. As a result, the shortage of air due to the EGR of the engine 1 during high-speed, high-load running is eliminated, and the emission of black smoke from the engine 1 can be reduced.

[0006]

However, in the above-mentioned conventional exhaust gas recirculation apparatus, since the inside diameter of the small tube in the EGR cooler is small, the small tube may be clogged with soot in the exhaust gas. For this reason, when the inside diameter of the thin tube is increased, there is a problem that the cooling efficiency is reduced. When the entire length of the thin tube is increased to prevent this, there is a problem that the EGR cooler becomes large. An object of the present invention is to provide a muffler with a built-in catalyst for an engine with an exhaust gas recirculation device, which can prevent clogging of the EGR cooler due to soot in exhaust gas without increasing the size of the EGR cooler. It is another object of the present invention to provide a muffler with a built-in catalyst for an engine with an exhaust gas recirculation device that can recirculate exhaust gas to the engine more efficiently.

[0007]

The invention according to claim 1 is
As shown in FIG. 1 and FIG.
And an engine with an exhaust gas recirculation device that recirculates to the intake passage 14 via the EGR cooler 13. The characteristic configuration is that a cylindrical muffler main body 19 provided in the middle of the exhaust pipe 18 and an outlet chamber 27 provided inside the muffler main body 19 to purify the exhaust gas and at least the purified exhaust gas flows into the muffler main body 19 are provided. The catalyst 23 to be formed and the EGR pipe 1 formed on the peripheral wall of the muffler main body 19 and facing the outlet chamber 27
And an EGR gas intake 19a to which the second exhaust gas introduction section 12a is connected.

In the muffler with a built-in catalyst according to the first aspect, when the engine 11 is running at medium speed and medium load, the catalyst 23
The clean exhaust gas that has passed through the
The engine 1 flows into the pipe 12 and passes through the intake passage 14.
1 is supplied. At this time, since the exhaust gas passage area of the catalyst 23 is large, the purified exhaust gas that has passed through the catalyst 23 and flowed into the outlet chamber 27 hardly drops in pressure. Further, since the soot in the exhaust gas is collected by the catalyst 23, the exhaust gas flowing into the EGR pipe 12 hardly contains soot, and the EGR cooler 13 does not clog.

The invention according to claim 2 is the invention according to claim 1, and further includes an EGR pipe 12 as shown in FIG.
The exhaust gas introduction part 12a is inserted into the outlet chamber 27 from the EGR gas intake 19a, and the end of the exhaust gas introduction part 12a is formed to be curved toward the catalyst 23 with a predetermined radius of curvature. In the muffler with a built-in catalyst according to the second aspect, the end of the exhaust gas introduction portion 12a is formed to be curved toward the catalyst 23 with a predetermined radius of curvature.
Part of the purified exhaust gas that has passed through the catalyst 23 is smoothly
It flows into the R pipe 12. As a result, the exhaust gas can be returned to the engine 11 more efficiently.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 3,
The exhaust gas recirculation device 11 is configured to recirculate exhaust gas to an intake pipe 14 via an EGR pipe 12 and an EGR cooler 13, and a muffler 17 for suppressing exhaust noise of a diesel engine 16 is provided in the exhaust pipe 18. The muffler 17 has a cylindrical muffler main body 19 whose both ends are sealed by a pair of first and second end plates 21 and 22.
The catalyst 23 is accommodated in the inside (FIG. 1). Examples of the catalyst 23 include a monolith catalyst having a ceramic carrier and a metal carrier. The catalyst 23 is held by a pair of brackets 24, 25, and the outer peripheral surfaces of these brackets 24, 25 are fixed to the inner peripheral surface of the muffler main body 19. The catalyst 23 in the present embodiment is an oxidation catalyst formed by dispersing and supporting Pt or Pd on a porous alumina carrier (not shown) formed in a honeycomb shape. This catalyst 2
3, the interior of the muffler main body 19 has an inlet chamber 26 and an outlet chamber 27.
It is divided into and.

An upstream pipe 18a of the exhaust pipe 18 is inserted through the first end plate 21, and a downstream pipe 18b of the exhaust pipe 18 is inserted through the second end plate 22. The entrance chamber 26 is partitioned into first and second chambers 26a and 26b by an entrance-side partition plate 28, and the exit chamber 27 is divided into third and fourth chambers by an exit-side partition plate 29.
It is partitioned into chambers 27a and 27b. The distal end of the upstream pipe 18a is connected to the inlet-side partition plate 28, and the downstream pipe 18a
The base end of b is connected to the outlet-side partition plate 29. Further, a plurality of first ventilation holes 18c are formed in a portion of the upstream pipe 18a inserted into the first chamber 26a, and a second communication port communicating the first and second chambers 26a and 26b is formed in the inlet-side partition plate 28. Stoma 2
8a are formed. The exit side partition plate 29 has the third and fourth
A third vent hole 29a communicating the chambers 27a and 27b is formed, and a plurality of fourth vent holes 18d are formed in a portion of the downstream pipe 18b inserted into the fourth chamber 27b. Further, an EGR gas intake 19a is formed in the peripheral wall of the muffler main body 19 so as to face the third chamber 27a of the outlet chamber 27.

An exhaust gas inlet 12a, which is a base end of the EGR pipe 12, is connected to the EGR gas intake 19a (FIG. 1), and an exhaust gas outlet 12b, which is a distal end of the EGR pipe 12, has an intake pipe 14 just before an intake manifold 16a. (FIG. 3). The exhaust gas introduction part 12a is inserted into the third chamber 27a from the EGR gas intake 19a, and an end of the exhaust gas introduction part 12a is formed to have a predetermined radius of curvature toward the catalyst 23 (FIG. 1). An opening 12c at the end of the exhaust gas introduction portion 12a is formed to face the catalyst 23. A fixed flange 31 is welded to the outer peripheral surface of the muffler main body 19 so as to surround the EGR gas intake 19a, and a mounting flange 32 is welded to the outer peripheral surface of the exhaust gas introduction portion 12a. The exhaust gas introduction part 12a is connected to the EGR gas intake 19
a into the third chamber 27a, and the bolt 33 is screwed into the fixing flange 31 via the mounting flange 32, whereby the exhaust gas introduction portion 12a is fixed to the muffler body 19.

The entrance side partition plate 28, the bracket 2
5. Drain holes 28b, 25a, 29b and 22a are formed between the lower end of the outlet-side partition plate 29 and the second end plate 22 and the muffler body 19, respectively (FIG. 1). Second head plate 22
As an example, the water drain hole 22a is formed by providing a concave portion having a relatively small radius of curvature at the lower end of the second end plate 22, as shown in FIG. The other drain holes 28b, 25a and 29b are formed in the same manner as the drain hole 22a.

The EGR pipe 12 is provided with an EGR valve 34 for adjusting the flow rate of exhaust gas flowing through the EGR pipe (FIG. 3). The EGR valve 34 is an EGR pipe 1
It has a valve case 34a for slidably holding an umbrella-type valve element (not shown) for opening and closing the valve 2, and a diaphragm case 34c for accommodating a diaphragm 34b for holding the umbrella-type valve element. Although not shown, the inside of the diaphragm case 34c is partitioned by a diaphragm 34b into an atmospheric pressure chamber and a compressed air supply / discharge chamber, and the compressed air supply / discharge chamber is connected to an air tank 37 through an air pipe 36. An inflow adjusting valve 38 for adjusting the amount of compressed air flowing into the compressed air supply / discharge chamber is provided in the middle of the air pipe 36.

The EGR cooler 13 is a water-cooled heat exchanger, and has a cylindrical cooler body 13a having both ends closed, and the cooler body 13a is connected to an inlet gas chamber 13b and a cooling water chamber 13a.
c and a pair of cooling water partitioning plates 13e, 13e partitioned into an outlet side gas chamber 13d, and a pair of cooling water partitioning plates 13e, 13e inserted through the cooling water chamber 13c and held at both ends by an inlet side gas chamber 13b and an outlet. And a large number of thin tubes 13f communicating with the side gas chamber 13d. The inlet gas chamber 13b is connected to the EGR pipe 12 on the exhaust pipe 18 side, and the outlet gas chamber 13d is connected to the EGR pipe 12 on the intake pipe 14 side. The cooling water chamber 13c is configured to allow engine cooling water to pass through. The cooler 13 cools the exhaust gas flowing from the EGR pipe 12 into the thin tube 13f by the engine cooling water, thereby increasing the density of the exhaust gas recirculated to the intake pipe 14.

The engine 11 is provided with a rotation sensor 39 for detecting a rotation speed of a crankshaft (not shown) of the engine, and a fuel injection pump (not shown) is provided with a control rack (not shown) depending on the position thereof. A load sensor 40 for detecting a load on the engine 11 is provided. The control input of the controller 41 includes a rotation sensor 39 and a load sensor 40.
Are respectively connected, and the control output of the controller 41 is connected to the inflow amount regulating valve 38. Further, the controller 41 is provided with a memory (not shown), and the memory stores an optimal change in the opening degree of the inflow amount adjusting valve 38 with respect to a change in the rotation speed and load of the engine 11 as a map.

The operation of the muffler with a built-in catalyst constructed as described above will be described. When the engine 11 is running at medium speed and medium load,
The controller 41 includes a rotation sensor 39 and a load sensor 40.
Is compared with the map stored in the memory, and the inflow control valve 38 is turned on. In this state, the high-temperature and high-pressure exhaust gas discharged from the engine 11 first expands and decelerates in the first chamber 26a when entering the first chamber 26a through the upstream pipe 18a and the first ventilation hole 18c. Further, when the exhaust gas enters the second chamber 26b through the second ventilation hole 28a, the speed is also reduced, and the pressure wave of the exhaust gas is attenuated to mute. Next, the exhaust gas is supplied to the second chamber 2.
6b flows into the catalyst 23, carbon monoxide and hydrocarbons in the exhaust gas are purified into harmless carbon dioxide and water vapor, and soot in the exhaust gas is oxidized and purified on the catalyst 23. The purified exhaust gas flows into the third chamber 27a, a part of which flows into the EGR pipe 12 from the end of the exhaust gas introduction portion 12a, and is supplied to the engine 11 through the intake pipe 14 and the intake manifold 16a.

At this time, since the flow rate of the exhaust gas in the first and second chambers 26a and 26b is small, the pressure is high, and since the total pore area of the catalyst 23 is large, it passes through the catalyst 23 and passes through the third chamber 27a. The purified exhaust gas flowing into the tank hardly drops in pressure. Further, since the exhaust gas flowing into the EGR pipe 12 contains almost no soot, the thin tube 1 of the EGR cooler 13
3f does not cause clogging. Further, the end of the exhaust gas introduction portion 12a is formed to be curved toward the catalyst 23 with a predetermined radius of curvature, and the opening 1 at the end of the exhaust gas introduction portion 12a is formed.
Since 2c is formed facing the catalyst 23, a part of the purified exhaust gas flows into the EGR pipe 12 smoothly.

As a result, a relatively large pressure difference is generated between the third chamber 27a and the intake pipe 14, and a sufficient amount of exhaust gas can be supplied to the engine 11 by the pressure difference. The temperature of the combustion gas is lowered, the reaction between nitrogen and oxygen is suppressed, and the emission of NOx can be reduced. The remaining portion of the purified exhaust gas that has flowed into the third chamber 27a enters the third chamber 27b through the third vent hole 29a, and further flows into the downstream pipe 18b through the fourth vent hole 18d. The exhaust noise is further reduced by increasing the flow velocity and decreasing the pressure thereof, and further reducing the pressure wave of the exhaust gas. The heat of the exhaust gas is transmitted to the atmosphere through the muffler body 19 having a large area.

On the other hand, when the engine 11 is running continuously under a full load (uphill) or at a high speed steady running, the controller 41 compares the detection outputs of the rotation sensor 39 and the load sensor 40 and a map of the memory to calculate the inflow amount. The control valve 38 is turned off. As a result, it is possible to stop the flow of exhaust gas into the engine 11 that requires a relatively large amount of air. As a result, the shortage of air due to the EGR of the engine 11 during high-speed, high-load running is eliminated, so that the emission of black smoke from the engine 11 can be reduced.

If sulfur is contained in the exhaust gas of the engine 16, sulfate is generated by the reaction in the catalyst 23, and when this sulfate is combined with dew water,
Sulfuric acid may be generated. However, since the dew water is discharged out of the muffler main body 19 through the drain holes 28b, 25a, 29b and 22a, no sulfuric acid is generated, so that the muffler 17 does not rust.

FIG. 4 shows a second embodiment of the present invention.
4, the same reference numerals as those in FIG. 1 indicate the same parts. In this embodiment, the front end of the upstream pipe 68a of the exhaust pipe 68 is directly connected to one bracket 24 holding the catalyst 23 without the inlet chamber and the first end plate. That is, the catalyst 23 is accommodated such that one end face thereof is opposed to the tip of the upstream pipe 68a, and the other end face of the catalyst 23 is divided into the third and fourth chambers 27a and 27b by the outlet partition plate 29. Room 2
7 is formed. In addition, an enlarged portion 68e that gradually expands toward the catalyst 23 without forming the first ventilation hole is provided at the distal end portion of the upstream pipe 68a. Reference numeral 25 in FIG.
Reference numerals a, 29b, and 22a denote drain holes for discharging dew water from the muffler main body 19. These drain holes 25
a, 29b and 22a are formed in the same manner as in the first embodiment. Except for the above, the configuration is the same as that of the first embodiment. In the muffler with a catalyst configured as described above, the exhaust gas passing through the upstream pipe 68a of the exhaust pipe 68 is smoothly guided to the catalyst 23 by the enlarged portion 68e. Can suppress the rise,
Exhaust gas can be evenly passed through the catalyst 23. Other than the above is substantially the same as the first embodiment,
The description of the repetition is omitted.

FIGS. 5 and 6 show a third embodiment of the present invention. 5 and 6, the same reference numerals as those in FIGS. 1 and 2 indicate the same parts. In this embodiment, there is no inlet-side partition plate, and a cone body 88e that gradually expands from the upstream pipe 88a toward the catalyst 23 is provided at the tip of the upstream pipe 88a inserted into the inlet chamber 96 (FIG. 5). One end of the cone body 88e is connected to the distal end of the upstream pipe 88a, and the other end is bonded to the inner peripheral surface of the entrance chamber 98 of the muffler body 19. This cone body 88e divides the entrance chamber 96 into an inside of the cone body 88e and a resonance sound absorbing chamber 96a outside the cone body 88e. A plurality of first ventilation holes 88c are formed in a portion of the upstream pipe 88a inserted into the inlet chamber 96, and the interior of the upstream pipe 88a and the resonance sound absorbing chamber 96a communicate with each other through these first ventilation holes 88c. You. Reference numerals 88f, 25a, 29b, and 91 in FIG. 5 denote drain holes for discharging the dew condensation water from the muffler main body 19. The drain holes 88f, 25a and 29b are formed in the same manner as in the first embodiment. The drain hole 91 is formed at the lower end of the muffler main body 19 so as to face the fourth chamber 27b near the second end plate 22, and the drain hole 91 has a short pipe 9 projecting downward.
2 is inserted. Except for the above, the configuration is the same as that of the first embodiment.

In the muffler with a built-in catalyst constructed as described above, when high-temperature and high-pressure exhaust gas discharged from the engine enters the inlet chamber 96 through the upstream pipe 88a, a part of the exhaust gas is supplied to the first vent hole. From 88c to the resonance sound absorbing chamber 96
Since the gas enters the air outlet and expands, exhaust noise can be reduced. The exhaust gas whose exhaust noise is reduced is guided by the cone body 88e and smoothly flows into the catalyst 23 as shown by the solid arrow in FIG. Operations other than those described above are substantially the same as those in the first embodiment, and thus, repeated description will be omitted.

In the first to third embodiments,
Although a monolith catalyst was used as the catalyst, a granular pellet catalyst may be used. In the first to third embodiments, the water-cooled EGR cooler is used.
An R cooler may be used. Further, in the first to third embodiments, the exhaust gas discharge portion of the EGR pipe is connected to the intake pipe immediately before the intake manifold, but may be connected to the intake manifold. Further, in the first to third embodiments,
Although the EGR valve has been described in which the diaphragm is deformed by the supply and discharge of compressed air to drive the valve body, the diaphragm is deformed by negative pressure (vacuum pump) to drive the umbrella type valve body. An EGR valve configured to drive a valve element such as a butterfly valve by using an air cylinder instead of the diaphragm may be used.

[0026]

As described above, according to the present invention, the muffler body is provided in the middle of the exhaust pipe to purify the exhaust gas, and at least the catalyst for forming the outlet chamber into which the purified exhaust gas flows into the muffler body. Provided inside the muffler main body, forming an EGR gas intake port on the muffler main body peripheral wall facing the outlet chamber,
Further, since the exhaust gas introduction portion of the EGR pipe is connected to the EGR gas intake, the clean exhaust gas that has passed through the catalyst flows into the EGR pipe from the exhaust gas introduction portion and is supplied to the engine through the intake passage. At this time, since the exhaust gas passage area of the catalyst is large, the purified exhaust gas that has passed through the catalyst and flowed into the outlet chamber hardly drops in pressure, and soot in the exhaust gas is collected by the catalyst and flows into the EGR pipe. The exhaust gas contains little soot and the EGR cooler does not clog.
As a result, a relatively large pressure difference is generated between the outlet chamber and the intake passage, and the pressure difference can supply a sufficient amount of exhaust gas to the engine, so that the temperature of the combustion gas in the combustion chamber of the engine decreases. The reaction between nitrogen and oxygen is suppressed, and N
Ox emissions can be reduced. Further, if the exhaust gas introduction portion of the EGR pipe is inserted from the EGR gas intake into the outlet chamber, and the end of the exhaust gas introduction portion is formed to have a predetermined radius of curvature toward the catalyst, the purified exhaust gas that has passed through the catalyst can be removed. A part flows into the EGR pipe smoothly. As a result, the exhaust gas can be returned to the engine more efficiently.

[Brief description of the drawings]

FIG. 1 is an enlarged vertical sectional view of a part A in FIG. 3 showing a muffler with a built-in catalyst according to a first embodiment of the present invention.

FIG. 2 is a view taken in the direction of arrow B in FIG. 1;

FIG. 3 is a configuration diagram of an engine including the muffler and the exhaust gas recirculation device.

FIG. 4 is a longitudinal sectional view corresponding to FIG. 1 and showing a second embodiment of the present invention.

FIG. 5 is a longitudinal sectional view corresponding to FIG. 1, showing a third embodiment of the present invention.

FIG. 6 is an enlarged sectional view of a portion C in FIG. 5;

FIG. 7 is a configuration diagram corresponding to FIG. 3 showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Exhaust gas recirculation apparatus 12 EGR pipe 12a Exhaust gas introduction part 13 EGR cooler 14 Intake pipe (intake passage) 16 Engine 17, 67, 87 Muffler 18, 68, 88 Exhaust pipe 19 Muffler main body 19a EGR gas intake 23 Catalyst 27 Exit chamber

Claims (2)

[Claims] In an engine with an exhaust gas recirculation device for recirculating exhaust gas to an intake passage (14) through an EGR pipe (12) and an EGR cooler (13), the engine is provided in the middle of an exhaust pipe (18, 68, 88). Muffler body (19)
A catalyst (23) provided inside the muffler body (19) to purify the exhaust gas and form an outlet chamber (27) into which at least the purified exhaust gas flows into the muffler body (19); (19) A catalyst characterized by comprising an EGR gas intake port (19a) formed on the peripheral wall facing the outlet chamber (27) and connected to an exhaust gas introduction section (12a) of the EGR pipe (12). Built-in muffler. 2. An exhaust gas introduction section (12a) of an EGR pipe (12).
Is inserted from the EGR gas inlet (19a) into the outlet chamber (27), and the end of the exhaust gas introduction part (12a) is formed to be curved toward the catalyst (23) with a predetermined radius of curvature. 2. The muffler with a built-in catalyst according to 1.