WO2022180744A1 - Exhaust device for engine, work machine, and method for manufacturing catalyst pipe - Google Patents

Abstract

[Problem] To make the structure of an exhaust device easier by simplifying the structure of a catalyst pipe. [Solution] An exhaust device for an engine comprises exhaust pipes 31, 32 connected to an engine main body, a catalyst pipe 34 connected to the exhaust pipes 31, 32, and a catalyst 33 housed in the catalyst pipe 34, the catalyst pipe 34 including an inlet tube body 51 connected to the exhaust pipes 31, 32, an inner tube body 52 that is disposed on the exhaust-directional downstream side of the inlet tube body 51 and that covers the outer periphery of the catalyst 33, an outlet tube body 53 that is disposed on the exhaust-directional downstream side of the inner tube body 52 and that is provided with an outlet port 66 for exhaust gas, and an outer tube body 54 disposed on the outer periphery of the inner tube body 52 and fixed to the inlet tube body 51 and the outlet tube body 53.

Description

Method for manufacturing engine exhaust system, work machine and catalyst pipe

The present invention relates to an engine exhaust system, a working machine, and a method for manufacturing a catalyst pipe.

Conventionally, engines are provided with an exhaust system for discharging the exhaust gas generated during the combustion process. An exhaust system includes an exhaust pipe for passing exhaust gas, a catalyst for purifying the exhaust gas, a muffler for reducing exhaust noise, and the like. For example, an exhaust gas generated during a combustion process passes through an exhaust pipe, a catalyst, and a muffler in order, and then is discharged to the outside of the engine.

　The catalyst is usually housed in a pipe-shaped member. For example, Patent Document 1 discloses a relay pipe portion arranged downstream of a main pipe portion, a catalyst holding cylinder arranged downstream of the relay pipe portion and holding a catalyst, and a catalyst holding cylinder arranged downstream of the catalyst holding cylinder. an exhaust introduction pipe arranged downstream of the guide cylinder; a holding member holding the exhaust introduction pipe; an exhaust system comprising: a catalyst case;

JP 2014-185592 A

However, in Patent Document 1, the structure for housing the catalyst is lengthened and complicated, so it was difficult to easily manufacture the exhaust system. Therefore, there is a possibility that the manufacturing cost of the exhaust device will increase.

In view of the above background, an object of the present invention is to facilitate the manufacture of an exhaust system by simplifying the structure of the catalyst pipe.

One aspect of the present invention for solving the above problems is an exhaust system (5) for an engine (1), comprising exhaust pipes (31, 32) connected to an engine body (3), and A connected catalyst pipe (34) and a catalyst (33) housed in the catalyst pipe are provided, and the catalyst pipe includes an introduction cylinder (51) connected to the exhaust pipe and the introduction cylinder an inner cylindrical body (52) disposed on the downstream side in the exhaust direction of the catalyst and covering the outer periphery of the catalyst; and a lead-out cylinder disposed on the downstream side of the inner cylindrical body in the exhaust direction and provided with an exhaust gas outlet (66). and an outer cylinder (54) arranged on the outer periphery of the inner cylinder and fixed to the introduction cylinder and the lead-out cylinder.

According to this aspect, by simplifying the structure of the catalyst pipe, it is possible to facilitate the manufacture of the exhaust system. Therefore, the manufacturing cost of the exhaust device can be kept low.

In the above aspect, the inner cylinder may be welded to the introduction cylinder and slidably fitted to the lead-out cylinder.

According to this aspect, when the catalyst thermally expands and extends in the longitudinal direction of the catalyst pipe, the inner cylindrical body slides against the lead-out cylindrical body, thereby absorbing the length of the extended catalyst. be able to. Therefore, breakage of the catalyst and the catalyst pipe can be suppressed.

In the above aspect, the lead-out cylinder has a first diameter-reduced portion (63) that decreases in diameter from the downstream side in the exhaust direction toward the upstream side, and the inner cylinder has a diameter smaller than the first diameter-reduced portion. The outer cylindrical body may be slidably fitted in the lead-out cylinder on the upstream side in the exhaust direction, and the outer cylinder may be welded to the lead-out cylinder on the downstream side in the exhaust direction from the first diameter-reduced portion.

According to this aspect, the airtightness of the catalyst pipe is sufficiently ensured while adopting a configuration in which the inner cylinder is slidably fitted into the lead-out cylinder (that is, a configuration in which the inner cylinder and the lead-out cylinder are not fixed). and the exhaust gas leakage can be suppressed.

In the above aspect, the outer cylinder has a second diameter-reduced portion (69) that decreases in diameter from the downstream side toward the upstream side in the exhaust direction, and the outer cylinder includes the introduction cylinder and the inner cylinder. It may be welded to the introduction cylindrical body on the exhaust direction upstream side of the welded portion of the body and the second diameter-reduced portion.

According to this aspect, the airtightness of the catalyst pipe can be further improved, and leakage of exhaust gas can be more effectively suppressed.

In the above aspect, the catalyst pipe may further include a cover body (56) arranged on the outer periphery of the introduction cylinder.

According to this aspect, the introduction cylinder becomes less visible from the outside. For this reason, even if the introduction cylinder discolors due to the inflow of high-temperature exhaust gas, the user is less likely to feel discomfort.

In the above aspect, the catalyst pipe further includes a cover body (55) welded to an upstream end portion of the introduction cylinder in the exhaust direction, and an upstream end portion of the cover body in the exhaust direction is connected to the lid. The end portion of the cover body on the downstream side in the exhaust direction may be welded to the outer cylindrical body.

According to this aspect, it is possible to increase the strength of the catalyst pipe as a whole by using the cover body. Therefore, deformation and breakage of the catalyst pipe can be suppressed.

In the above aspect, the exhaust system further includes a muffler (41) disposed downstream of the catalyst pipe in the exhaust direction, and the lead-out cylinder has a connection flange (67) connected to the muffler. It may be provided on the outer circumference of the outlet.

According to this aspect, since the muffler can be easily attached to the catalyst pipe, any muffler can be selected according to the application of the engine.

In the above aspect, fixing pieces (61, 70) for fixing the catalyst pipe and the muffler may protrude from the outer peripheral surfaces of the introduction cylinder and the outer cylinder.

According to this aspect, the muffler can be fixed to the catalyst pipe in good balance, and the fixing strength between the catalyst pipe and the muffler can be increased.

In the above aspect, the lead-out cylinder has a tapered portion (64) whose diameter decreases from the upstream side toward the downstream side in the exhaust direction, and the tapered portion has a mounting boss (64) for mounting the temperature sensor (36). 65) may be provided.

According to this aspect, the temperature of the exhaust gas immediately after passing through the catalyst can be accurately detected, so the temperature of the catalyst can be accurately estimated.

In order to solve the above problems, one aspect of the present invention is a working machine (P) having an exhaust system for the engine.

According to this aspect, by keeping the manufacturing cost of the exhaust system of the engine low, it is possible to keep the manufacturing cost of the work machine as a whole low.

In one aspect of the present invention for solving the above problems, an introduction cylinder (51) provided with exhaust gas introduction ports (58, 59), and a catalyst disposed downstream of the introduction cylinder in the exhaust direction, an inner cylindrical body (52) covering the outer periphery of (33); a lead-out cylindrical body (53) disposed on the downstream side of the inner cylindrical body in the exhaust direction and provided with an exhaust gas lead-out port (66); A method for manufacturing a catalyst pipe (34) comprising an outer cylinder (54) arranged on the outer circumference of the cylinder and a cover body (56) arranged on the outer circumference of the introduction cylinder, the method comprising: a step of fixing the tubular body and the inner tubular body; a step of fixing the introduction tubular body and the outer tubular body; a step of fixing the outer tubular body and the cover body; and a step of fixing the body are sequentially performed.

By manufacturing the catalyst pipes in this order, the catalyst pipes can be manufactured easily, so the manufacturing cost of the exhaust system can be kept low.

According to the above aspect, by simplifying the structure of the catalyst pipe, it is possible to facilitate the manufacture of the exhaust system.

1 is a side view showing a V-type engine according to a first embodiment of the present invention; FIG. 1 is a rear view showing a V-type engine according to a first embodiment of the present invention; 1 is a perspective view showing an engine body and an air cleaner according to a first embodiment of the present invention; FIG. 1 is an exploded perspective view showing a V-type engine according to a first embodiment of the present invention; 1 is an exploded perspective view showing a V-type engine according to a first embodiment of the present invention; BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows the catalyst pipe which concerns on 1st Embodiment of this invention 1 is a sectional view showing a muffler according to a first embodiment of the invention; A side view showing a V-type engine according to a second embodiment of the present invention. A bottom view showing a V-type engine according to a second embodiment of the present invention. FIG. 2 is an exploded perspective view showing a V-type engine according to a second embodiment of the present invention; FIG. 2 is an exploded perspective view showing a V-type engine according to a second embodiment of the present invention;

(First embodiment)
<V-type engine 1>
First, a horizontal type V-type engine 1 (hereinafter abbreviated as "engine 1") according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 7. FIG. Hereinafter, for convenience of explanation, the right side of the drawing in FIG. 1 is defined as the front side (front side) of the engine 1 . In this specification, when it is described as "fixed by a bolt (not shown)", it means a case where it is fixed by a normal bolt having a threaded portion only on one side, and a case where it is fixed by a normal bolt having a threaded portion on both sides. including both cases where it is fixed by a stud bolt with

　1 and 2, the engine 1 is a general-purpose engine used as a power source for the work machine P. For example, the working machine P is a cutting machine such as a concrete cutter, a floor processing machine such as a floor leveling machine, a high-pressure washer, a generator, or the like. The engine 1 is configured by an OHV air-cooled two-cylinder engine. In other embodiments, the engine 1 may be an engine of a type other than the OHV type (for example, an OHC type engine), or an engine of a type other than an air-cooled type (for example, a water-cooled engine). It may be an engine with three or more cylinders. Furthermore, in other embodiments, the engine 1 may be a multi-cylinder engine (for example, an in-line engine) other than the V-type engine, or may be a single-cylinder engine.

The engine 1 has an engine body 3 , an air cleaner 4 arranged above the engine body 3 , and an exhaust device 5 arranged behind and above the engine body 3 . The constituent elements of the engine 1 will be described in order below.

<Engine body 3>
3 and 4, the engine body 3 includes a crankcase 7, a first cylinder bank 8 extending upward to the right from the crankcase 7, a second cylinder bank 9 extending upward to the left from the crankcase 7, contains.

A crankshaft 11 is rotatably supported in the central portion of the crankcase 7 . The crankshaft 11 is rotatably provided around a rotation axis X extending in the front-rear direction. That is, the engine 1 is a horizontal type engine in which the rotation axis X of the crankshaft 11 extends horizontally. A PTO shaft 12 (power take-off shaft: an example of an output portion) is provided at the rear end portion of the crankshaft 11 . The PTO shaft 12 is connected to a working portion of the working machine P (for example, a blade of a concrete cutter), and is configured to rotate according to the rotation of the PTO shaft 12 . The PTO shaft 12 protrudes rearward from a rear surface 7a (side surface) of the crankcase 7 and extends in the front-rear direction. A pair of left and right first fixed bosses 13 are provided on the upper portion of the rear surface 7a of the crankcase 7 .

The first and second cylinder banks 8 and 9 are arranged in the left-right direction (the width direction of the engine body 3). The first and second cylinder banks 8 and 9 are provided obliquely above the crankcase 7, respectively.

A piston (not shown) is housed in the lower part (cylinder) of the first and second cylinder banks 8, 9 so as to be able to reciprocate. The piston is connected to the crankshaft 11 via a connecting rod (not shown).

The upper portions (cylinder heads) of the first and second cylinder banks 8 and 9 define combustion chambers (not shown) together with the pistons. An intake port (not shown) that communicates with the combustion chamber is opened in the upper left and right inner surfaces of the first and second cylinder banks 8 and 9 . An exhaust port 19 communicating with the combustion chamber is opened in the upper rear surface of the first and second cylinder banks 8 and 9 , and a flange surface 20 is formed around the exhaust port 19 . A temperature sensor 21 (see FIG. 4) is arranged above the first cylinder bank 8 to detect its temperature. Note that in other embodiments, the temperature sensors 21 may be arranged in both the first and second cylinder banks 8 and 9, or the temperature sensors 21 may be arranged in the first and second cylinder banks 8 and 9. It doesn't have to be.

A second fixed boss 22 is provided on the inner side of the flange surface 20 in the left-right direction on the upper rear surfaces of the first and second cylinder banks 8 and 9 . A third fixed boss 23 is provided above the flange surface 20 on the rear surface of the upper portion of the first cylinder bank 8 . An L-shaped mounting plate 24 (see FIG. 4) is fixed to the third fixed boss 23 with a bolt (not shown). A fourth fixed boss 25 is provided above the flange surface 20 on the rear surface of the upper portion of the second cylinder bank 9 .

<Air cleaner 4>
Referring to FIG. 3, the air cleaner 4 has a flat shape (plate shape) elongated in the left-right direction and the front-rear direction. The air cleaner 4 is arranged between the first and second cylinder banks 8 and 9 of the engine body 3 . The air cleaner 4 is connected to the intake ports (not shown) of the first and second cylinder banks 8 and 9 via intake pipes (not shown), and the air cleaned by the air cleaner 4 passes through the intake ports. into a combustion chamber (not shown).

<Exhaust device 5>
The exhaust device 5 is a device for discharging exhaust gas discharged from the engine body 3 to the outside of the engine 1 . Hereinafter, when describing upstream or downstream, it means upstream or downstream in the exhaust direction (that is, the direction in which the exhaust gas flows in the exhaust device 5). A dashed-dotted line arrow appropriately attached to each figure indicates the exhaust direction.

4 and 5, the exhaust system 5 includes first and second exhaust pipes 31 and 32, a catalyst 33, a catalyst pipe 34, an oxygen sensor 35, a temperature sensor 36, first and second 2 reinforcing members 37 and 38, a heat shield member 39, and an engine muffler 41 (hereinafter abbreviated as "muffler 41"). The constituent elements of the exhaust device 5 will be described in order below.

<First and Second Exhaust Pipes 31, 32>
4 and 5, the first and second exhaust pipes 31 and 32 of the exhaust system 5 are arranged rearward of the engine body 3 and arranged in the left-right direction. The inner diameters of the first and second exhaust pipes 31 , 32 are larger than the inner diameters of the exhaust ports 19 of the first and second cylinder banks 8 , 9 . The length of the second exhaust pipe 32 is longer than the length of the first exhaust pipe 31 .

The first exhaust pipe 31 extends upward while curving. A first fixed flange 44 is provided on the outer periphery of the lower end (upstream end) of the first exhaust pipe 31 . The first fixed flange 44 is fixed to the flange surface 20 of the first cylinder bank 8 with a pair of bolts (not shown). Thereby, the lower end of the first exhaust pipe 31 is connected to the exhaust port 19 of the first cylinder bank 8 .

The left portion (upstream portion) of the second exhaust pipe 32 extends from left to right while curving. A central portion in the left-right direction of the second exhaust pipe 32 extends linearly from left to right. The right portion (downstream portion) of the second exhaust pipe 32 extends upward while curving. A second fixed flange 47 is provided on the outer periphery of the left end (upstream end) of the second exhaust pipe 32 . The second fixed flange 47 is fixed to the flange surface 20 of the second cylinder bank 9 with a pair of bolts (not shown). Thereby, the left end of the second exhaust pipe 32 is connected to the exhaust port 19 of the second cylinder bank 9 .

<Catalyst 33>
4 and 5, the catalyst 33 of the exhaust device 5 has a columnar shape elongated in the left-right direction. That is, in this embodiment, the longitudinal direction of the catalyst 33 is the left-right direction. For example, the catalyst 33 is composed of a three-way catalyst. The catalyst 33 purifies the exhaust gas by chemically converting harmful components of the exhaust gas discharged from the engine body 3 through the first and second exhaust pipes 31 and 32 into harmless components.

<Catalyst pipe 34>
Referring to FIG. 1 , catalyst pipe 34 of exhaust system 5 is arranged behind air cleaner 4 and adjacent to air cleaner 4 . The catalyst pipe 34 is arranged above the PTO shaft 12 and protrudes rearward (laterally) beyond the rear surface 7 a (side surface) of the crankcase 7 . The outer surface of the catalyst pipe 34 (the surface opposite to the surface facing the engine body 3) is covered with a cover member (not shown).

Referring to FIG. 2, the catalyst pipe 34 is arranged adjacent to the first and second cylinder banks 8,9. The catalyst pipe 34 extends in the left-right direction from the upper end side (front end side) of the first cylinder bank 8 to the upper end side (front end side) of the second cylinder bank 9 . The catalyst pipe 34 is accommodated within the width W of the engine body 3 when viewed in the front-rear direction (the axial direction of the crankshaft 11).

4 to 6, catalyst pipe 34 has a cylindrical shape elongated in the left-right direction. That is, in this embodiment, the longitudinal direction of the catalyst pipe 34 is the left-right direction. Note that, in other embodiments, the catalyst pipe 34 may have a shape other than a cylindrical shape (for example, a square tube shape). The catalyst pipe 34 is arranged downstream of the first and second exhaust pipes 31 and 32 . The catalyst pipe 34 accommodates the catalyst 33 .

The catalyst pipe 34 includes an introduction cylinder 51 , an inner cylinder 52 , an outlet cylinder 53 , an outer cylinder 54 , a lid 55 and a cover 56 . The arrow M in FIG. 4 indicates the lateral range of the catalyst pipe 34 (the range from the left end of the lead-out cylinder 53 to the right end of the cover 56). The inner diameters of the introduction cylinder 51, the inner cylinder 52, and the discharge cylinder 53 (that is, the inner diameter of the portion of the catalyst pipe 34 through which the exhaust gas flows) larger than the inner diameter of

The introduction cylinder 51 extends in the left-right direction. First and second exhaust gas introduction ports 58 and 59 are provided on the lower surface of the introduction cylinder 51 at intervals in the left-right direction. The upper end (downstream end) of the first exhaust pipe 31 is connected to the first inlet 58 on the right side (upstream side) of the catalyst 33 . The right end (downstream end) of the second exhaust pipe 32 is connected to the second inlet 59 on the right side (upstream side) of the catalyst 33 .

A first mounting boss 60 is provided on the front surface of the introduction cylinder 51 (the surface facing the first and second introduction ports 58 and 59). The first mounting boss 60 is arranged on the left side of the first introduction port 58 and on the right side of the second introduction port 59 . That is, the first mounting boss 60 is arranged between the first introduction port 58 and the second introduction port 59 in the left-right direction. A fixed piece 61 protrudes rearward from the outer peripheral surface of the introduction cylinder 51 . Note that the fixing piece 61 is omitted except for FIG.

The inner tubular body 52 extends in the left-right direction. The inner cylinder 52 is arranged on the left side (downstream side) of the introduction cylinder 51 . The inner circumference of the right end of the inner cylinder 52 is fixed to the outer circumference of the left end of the introduction cylinder 51 by welding. The inner cylindrical body 52 covers the outer circumference of the catalyst 33 . The inner peripheral surface of the inner cylindrical body 52 is fixed to the outer peripheral surface of the catalyst 33 by welding.

The lead-out cylinder 53 extends in the left-right direction. The lead-out cylinder 53 is arranged on the left side (downstream side) of the inner cylinder 52 . A first reduced diameter portion 63 whose diameter is reduced from the left side (downstream side) to the right side (upstream side) is provided on the right side portion of the lead-out cylinder 53 . The left side of the inner cylindrical body 52 is slidably fitted to the right end of the lead-out cylindrical body 53 on the right side (upstream side) of the first reduced diameter portion 63 . A tapered portion 64 whose diameter decreases from the right side (upstream side) to the left side (downstream side) is provided in the central portion of the lead-out cylinder 53 in the left-right direction. A second mounting boss 65 is provided on the front surface of the tapered portion 64 . An exhaust gas outlet port 66 is provided at the left end of the outlet cylinder 53 , and a connection flange 67 is provided on the outer circumference of the outlet port 66 . The connection flange 67 is fixed to the left end of the lead-out cylinder 53 by welding.

The outer cylindrical body 54 extends in the left-right direction. The outer cylindrical body 54 is arranged on the outer circumference of the inner cylindrical body 52 . A right side portion of the outer cylindrical body 54 is provided with a second reduced diameter portion 69 whose diameter is reduced from the left side (downstream side) to the right side (upstream side). The inner periphery of the right end portion of the outer cylinder 54 is located on the right side (upstream side) of the welded portion between the introduction cylinder 51 and the inner cylinder 52 and the second reduced diameter portion 69, and the outer periphery of the left side of the introduction cylinder 51. fixed by welding. The inner circumference of the left end portion of the outer cylinder 54 is fixed to the outer circumference of the right side of the lead-out cylinder 53 on the left side (downstream side) of the first reduced diameter portion 63 of the lead-out cylinder 53 by welding. A fixing piece 70 protrudes rearward from the outer peripheral surface of the outer cylindrical body 54 . Note that the fixing piece 70 is omitted except for FIG.

The lid body 55 includes a closing piece 73 and a projecting piece 74 that projects rightward from the closing piece 73 . The closing piece 73 is fixed to the inner periphery of the right end (upstream end) of the introduction cylinder 51 by welding. As a result, the lid 55 covers the right end of the introduction cylinder 51 . The projecting piece 74 is fixed to the closing piece 73 by welding.

The cover body 56 extends in the left-right direction. The cover body 56 is arranged on the outer periphery of the introduction cylinder 51 . The right end (upstream end) of the cover body 56 is fixed to the protruding piece 74 of the lid body 55 by welding. The left end (downstream end) of the cover body 56 is fixed by welding to the outer periphery of the right side of the outer cylindrical body 54 on the left side (downstream side) of the second reduced diameter portion 69 of the outer cylindrical body 54 . there is

A notch 76 is provided on the front surface of the cover body 56 at a position corresponding to the first mounting boss 60 of the introduction cylinder 51 . Holes 78 are provided on the rear surface of the cover body 56 at positions corresponding to the fixed pieces 61 of the introduction cylinder 51 . Note that the holes 78 are omitted except for FIG.

<Oxygen sensor 35>
Referring to FIG. 4, oxygen sensor 35 of exhaust system 5 is a sensor that detects the oxygen concentration of the exhaust gas discharged from engine body 3 through first and second exhaust pipes 31 and 32 . The oxygen sensor 35 is arranged on the right side (upstream side) of the catalyst 33 . The oxygen sensor 35 is attached to the first mounting boss 60 of the introduction cylinder 51 of the catalyst pipe 34, and is arranged between the first introduction port 58 and the second introduction port 59 of the introduction cylinder 51 in the left-right direction. there is

<Temperature sensor 36>
Referring to FIG. 4 , temperature sensor 36 of exhaust device 5 is a sensor that detects the temperature of the exhaust gas that has passed through catalyst 33 . For example, the catalyst 33 can be protected by stopping the operation of the engine 1 when the temperature of the exhaust gas detected by the temperature sensor 36 exceeds a predetermined threshold. That is, the temperature sensor 36 is a sensor for protecting the catalyst. The temperature sensor 36 is arranged on the left side (downstream side) of the catalyst 33 . The temperature sensor 36 is attached to the second attachment boss 65 of the lead-out cylinder 53 of the catalyst pipe 34 .

<First and Second Reinforcing Members 37, 38>
4 and 5, the first and second reinforcing members 37 and 38 of the exhaust device 5 are arranged rearward of the engine body 3 and arranged in the left-right direction. The first and second reinforcing members 37 and 38 are arranged between the catalyst pipe 34 and the heat shield member 39 .

The first reinforcing member 37 includes a vertically extending base portion 81 and a projecting portion 82 projecting forward from the lower right portion of the base portion 81 . The right side portion of the first reinforcing member 37 is fixed to the outer peripheral surface of the first exhaust pipe 31 by welding. The left side portion of the first reinforcing member 37 is fixed to the outer peripheral surface of the second exhaust pipe 32 by welding.

The second reinforcing member 38 extends vertically. The upper part of the second reinforcing member 38 is fixed to the outer peripheral surfaces of the lead-out cylinder 53 and the outer cylinder 54 of the catalyst pipe 34 by welding. A lower portion of the second reinforcing member 38 is fixed to the outer peripheral surface of the second exhaust pipe 32 by welding.

<Heat shield member 39>
4 and 5, the heat shield member 39 of the exhaust device 5 is arranged behind the engine body 3 and extends in the left-right direction. A heat shield member 39 is arranged between the catalyst pipe 34 and the air cleaner 4 .

The upper right portion of the heat shield member 39 is fixed to the cover body 56 of the catalyst pipe 34 with a bolt (not shown). The lower right portion of the heat shield member 39 is fixed together with the lower portion of the base portion 81 of the first reinforcing member 37 to the second fixed boss 22 (see FIG. 3) of the first cylinder bank 8 by bolts (not shown). . The upper left portion of the heat shield member 39 is fixed to the upper portion of the second reinforcing member 38 with a bolt (not shown). The lower left portion of the heat shield member 39 is fixed together with the lower portion of the second reinforcing member 38 to the second fixed boss 22 (see FIG. 3) of the second cylinder bank 9 with bolts (not shown).

<Muffler 41>
1 and 2, the muffler 41 of the exhaust system 5 is arranged downstream of the catalyst pipe 34. As shown in FIG. The muffler 41 is not welded to the catalyst pipe 34 and is separable from the catalyst pipe 34 . In another embodiment, the muffler 41 may be fixed to the catalyst pipe 34 by welding or the like. 5 and 7, the muffler 41 has a muffler body 94, a plurality of partition walls 95, 96, an inflow pipe 97, a communication pipe 98, and a discharge pipe 99.

Referring to FIG. 1, the muffler body 94 is arranged adjacent to the catalyst pipe 34 behind and below the catalyst pipe 34 . The muffler main body 94 protrudes rearward (laterally) from the rear surface 7a (side surface) of the crankcase 7 . The outer surface of the muffler body 94 (the surface opposite to the surface facing the engine body 3) is covered with the aforementioned cover member (not shown).

Referring to FIG. 2, the muffler main body 94 is arranged parallel to the catalyst pipe 34, and extends from the upper end side (front end side) of the first cylinder bank 8 to the upper end side (front end side) of the second cylinder bank 9. extending in the direction The upper portion of the muffler body 94 overlaps the lower portion of the catalyst pipe 34 when viewed in the front-rear direction. Left and right side portions of the muffler main body 94 overlap upper portions of the first and second cylinder banks 8 and 9 when viewed in the front-rear direction. The muffler main body 94 is contained within the width W of the engine main body 3 when viewed in the front-rear direction.

With reference to FIGS. 5 and 7, the muffler body 94 has a cylindrical shape elongated in the left-right direction. That is, in this embodiment, the longitudinal direction of the muffler main body 94 is the left-right direction. In other embodiments, the muffler main body 94 may have a shape other than a cylindrical shape (for example, a square tube shape).

The muffler main body 94 includes a cylindrical portion 101 extending in the left-right direction and a pair of lid portions 102 covering openings at both ends of the cylindrical portion 101 . A fixing bracket 104 protrudes forward from the central portion in the left-right direction of the outer peripheral surface of the tubular portion 101 . The fixed bracket 104 is fixed to a pair of left and right first fixed bosses 13 of the crankcase 7 with a pair of bolts (not shown). A pair of left and right fixed stays 105 protrude forward from left and right side portions of the outer peripheral surface of the tubular portion 101 . The right fixed stay 105 is fixed to the mounting plate 24 fixed to the first cylinder bank 8 with bolts (not shown). The left fixed stay 105 is fixed to the fourth fixed boss 25 of the second cylinder bank 9 with a bolt (not shown). A pair of left and right fixing pieces (not shown) protrude from the outer peripheral surface of the cylindrical portion 101 . The right fixed piece is fixed to the fixed piece 61 of the introduction cylinder 51 of the catalyst pipe 34 with a bolt (not shown). The left fixed piece is fixed to the fixed piece 70 of the outer cylindrical body 54 of the catalyst pipe 34 with a bolt (not shown).

A plurality of muffler chambers 111 to 113 are formed inside the muffler main body 94 . The plurality of muffler chambers 111 to 113 are a first muffler chamber 111 formed at the left end of the muffler body 94, a second muffler chamber 112 formed at the right end of the muffler body 94, the first muffler chamber 111 and the second muffler chamber 112. and a third silencer chamber 113 formed between the two silencer chambers 112 . The volumes of the plurality of sound deadening chambers 111 to 113 decrease in order of the volume of the first sound deadening chamber 111, the volume of the second deadening chamber 112, and the volume of the third deadening chamber 113. FIG. That is, the volume of the first sound deadening chamber 111>the volume of the second sound deadening chamber 112>the volume of the third sound deadening chamber 113. An exhaust gas inlet 109 is provided at the left end of the first silencer chamber 111 . The inlet 109 is configured by a hole provided in the left lid portion 102 .

The plurality of partition walls 95 and 96 includes a first partition wall 95 that partitions the first and third noise reduction chambers 111 and 113 in the horizontal direction, and a second partition wall 96 that partitions the second and third noise reduction chambers 112 and 113 in the horizontal direction. and includes A large number of small holes 115 are provided in the second partition wall 96 over the entire area, and the second sound deadening chamber 112 and the third sound deadening chamber 113 communicate with each other through the large number of small holes 115 .

The inflow pipe 97 is arranged on the left side of the muffler body 94 (outside in the width direction of the engine body 3). The inflow pipe 97 is curved in a U shape so as to protrude leftward (outward in the width direction of the engine body 3). A connection flange 117 is provided at the front end (upstream end) of the inflow pipe 97 . The connection flange 117 is fixed to the connection flange 67 of the outlet cylinder 53 of the catalyst pipe 34 with a pair of bolts (not shown). The rear end (downstream end) of the inflow pipe 97 is connected to the inflow port 109 of the first silencer chamber 111 of the muffler body 94 . A pipe cover (not shown) is attached to the outer peripheral surface of the inflow pipe 97 .

The communicating pipe 98 extends in the left-right direction. The communicating pipe 98 is supported by the first and second partition walls 95 and 96 by passing through the first and second partition walls 95 and 96 . A communication port 121 that communicates with the first silencer chamber 111 is provided at the left end (upstream end) of the communication pipe 98 . A cap 122 is fixed to the right end (downstream end) of the communicating pipe 98 by welding. Thereby, the right end of the communicating pipe 98 is covered with the cap 122 . A large number of communication holes 123 communicating with the second silencer chamber 112 are provided in the outer peripheral portion of the communication pipe 98 . With the configuration as described above, the first sound deadening chamber 111 and the second sound deadening chamber 112 communicate with each other through the communicating pipe 98 .

The discharge pipe 99 extends in the left-right direction. The exhaust pipe 99 passes through the pair of lid portions 102 of the muffler body 94 and the first and second partition walls 95 and 96, thereby connecting the pair of lid portions 102 and the first and second partition walls 95 and 96 of the muffler body 94. Supported. A large number of outer peripheral holes 127 communicating with the third noise reduction chamber 113 are provided on the outer peripheral portion of the discharge pipe 99 . Both left and right ends of the discharge pipe 99 protrude to both sides of the muffler main body 94 in the left and right direction. A pair of openings 125 are provided at both left and right ends of the discharge pipe 99 . A lid member 126 is fixed by welding to an opening 125 formed at the right end of the discharge pipe 99 . As a result, the opening 125 formed at the right end of the discharge pipe 99 is closed by the lid member 126 . An opening 125 formed at the left end of the exhaust pipe 99 is not closed by a lid member 126 and communicates with the external space S on the left side of the muffler body 94 . With the configuration described above, the third silencer chamber 113 and the external space S on the left side of the muffler main body 94 communicate with each other through the exhaust pipe 99 .

The right edge 99a of the discharge pipe 99 is provided on the outer periphery of the opening 125 formed at the right end of the discharge pipe 99, and the left edge 99b (downstream edge) of the discharge pipe 99 is provided on the outer periphery of the discharge pipe 99. It is provided on the outer circumference of the opening 125 formed at the left end. Left and right edge portions 99a and 99b of the discharge pipe 99 protrude to both sides of the muffler main body 94 in the left and right direction. Left and right edge portions 99a and 99b of the discharge pipe 99 form a continuous wave shape in the circumferential direction of the discharge pipe 99. As shown in FIG.

<Flow of Exhaust Gas>
When the engine 1 is driven, exhaust gas is discharged from the exhaust ports 19 of the first and second cylinder banks 8 and 9 . After passing through the first and second exhaust pipes 31 and 32, the exhaust gas discharged from the exhaust port 19 flows into the introduction cylinder 51 of the catalyst pipe 34 via the first and second introduction ports 58 and 59. . The exhaust gas that has flowed into the introduction cylinder 51 of the catalyst pipe 34 passes through the introduction cylinder 51, the inner cylinder 52, and the discharge cylinder 53 of the catalyst pipe 34 in order, and then exits the catalyst pipe 34 through the discharge port 66. It is discharged from the cylinder 53 . As the exhaust gas passes through the catalyst pipe 34 in this manner, the exhaust gas is purified by the catalyst 33 accommodated in the catalyst pipe 34 .

The exhaust gas discharged from the outlet cylinder 53 of the catalyst pipe 34 flows into the inflow pipe 97 of the muffler 41 . After passing through the inflow pipe 97 , the exhaust gas flows through the inflow port 109 into the first silencer chamber 111 of the muffler 41 . The exhaust gas that has flowed into the first noise reduction chamber 111 passes through the first noise reduction chamber 111 and then flows into the communication pipe 98 of the muffler 41 through the communication port 121 . After passing through the communication pipe 98 , the exhaust gas that has flowed into the communication pipe 98 flows into the second muffler chamber 112 of the muffler 41 through a large number of communication holes 123 . After passing through the second silencer chamber 112 , the exhaust gas flows into the third silencer chamber 113 of the muffler 41 through the small holes 115 of the second partition 96 . The exhaust gas that has flowed into the third silencer chamber 113 passes through the third silencer chamber 113 and then flows into the exhaust pipe 99 of the muffler 41 through the many outer perimeter holes 127 . The exhaust gas that has flowed into the exhaust pipe 99 passes through the exhaust pipe 99 and is then discharged to the external space S on the left side of the muffler body 94 through an opening 125 formed at the left end of the exhaust pipe 99 . Exhaust noise is reduced by passing the exhaust gas through the muffler 41 in this way.

<Effects of the first embodiment>
The catalyst pipe 34 includes an introduction cylinder 51 connected to the first and second exhaust pipes 31 and 32, an inner cylinder 52 arranged downstream of the introduction cylinder 51 and covering the outer circumference of the catalyst 33, and an inner cylinder A lead-out cylinder 53 arranged on the downstream side of the body 52 and provided with an exhaust gas outlet 66, and an outer cylinder arranged on the outer periphery of the inner cylinder 52 and fixed to the lead-in cylinder 51 and the lead-out cylinder 53. a body 54; By adopting such a configuration, the structure of the catalyst pipe 34 can be simplified, and the manufacturing of the exhaust system 5 can be facilitated. Therefore, the manufacturing cost of the exhaust device 5 can be kept low.

In addition, the inner cylindrical body 52 is welded to the introduction cylindrical body 51 and slidably fitted to the lead-out cylindrical body 53 . By adopting such a configuration, when the catalyst 33 thermally expands and extends in the left-right direction, the inner cylindrical body 52 slides against the lead-out cylindrical body 53, and the extension of the catalyst 33 is reduced. length can be absorbed. Therefore, breakage of the catalyst 33 and the catalyst pipe 34 can be suppressed.

In addition, the inner cylinder 52 is slidably fitted into the lead-out cylinder 53 on the upstream side of the first diameter-reduced portion 63 of the lead-out cylinder 53 , and the outer cylinder 54 is the first contraction of the lead-out cylinder 53 . It is welded to the lead-out cylinder 53 on the downstream side of the diameter portion 63 . By adopting such a configuration, while adopting a configuration in which the inner cylinder 52 is slidably fitted into the lead-out cylinder 53 (that is, a configuration in which the inner cylinder 52 and the lead-out cylinder 53 are not fixed), the catalyst It is possible to sufficiently ensure the airtightness of the pipe 34 and suppress the leakage of the exhaust gas.

In addition, the outer cylinder 54 is welded to the introduction cylinder 51 on the upstream side of the welded portion between the introduction cylinder 51 and the inner cylinder 52 and the second reduced diameter portion 69 of the outer cylinder 54 . By adopting such a configuration, the airtightness of the catalyst pipe 34 can be further improved, and leakage of exhaust gas can be suppressed more effectively. Furthermore, a space is formed between the inner cylindrical body 52 and the outer cylindrical body 54, thereby facilitating temperature adjustment. Therefore, the function of the catalyst 33 can be maintained, and a heat insulation effect to the outside can be expected.

In addition, the catalyst pipe 34 has a cover body 56 arranged on the outer circumference of the introduction cylinder 51 . By adopting such a configuration, the introduction cylinder 51 becomes less visible from the outside. Therefore, even if the introduction cylinder 51 is discolored due to the inflow of high-temperature exhaust gas, the user is less likely to feel discomfort.

The upstream end of the cover body 56 is welded to the lid body 55 , and the downstream end of the cover body 56 is welded to the outer cylindrical body 54 . By adopting such a configuration, the strength of the catalyst pipe 34 as a whole can be increased using the cover body 56 . Therefore, deformation and breakage of the catalyst pipe 34 can be suppressed.

A connection flange 67 connected to the muffler 41 is provided on the outer periphery of the outlet port 66 of the outlet cylinder 53 . By adopting such a configuration, the muffler 41 can be easily attached to the catalyst pipe 34 , so any muffler 41 can be selected according to the application of the engine 1 .

Fixing pieces 61 and 70 for fixing the catalyst pipe 34 and the muffler 41 protrude from the outer peripheral surfaces of the introduction cylinder 51 and the outer cylinder 54 . By adopting such a configuration, the muffler 41 can be fixed to the catalyst pipe 34 in a well-balanced manner, and the fixing strength between the catalyst pipe 34 and the muffler 41 can be increased.

A second mounting boss 65 for mounting the temperature sensor 36 is provided on the tapered portion 64 of the lead-out cylinder 53 . By adopting such a configuration, the temperature of the exhaust gas immediately after passing through the catalyst 33 can be accurately detected, so the temperature of the catalyst 33 can be accurately estimated.

<Manufacturing Method of Catalyst Pipe 34>
Next, an example of a method for manufacturing the catalyst pipe 34 will be described. In another embodiment, the catalyst pipe 34 may be manufactured in a different order than the manufacturing method described below.

First, the inner circumference of the right end of the inner cylinder 52 to which the catalyst 33 is welded and the outer circumference of the left end of the introduction cylinder 51 are fixed by welding. Next, the inner periphery of the right end of the outer cylinder 54 and the outer periphery of the left end of the introduction cylinder 51 are fixed by welding. Next, the left end of the cover body 56 and the outer periphery of the right side of the outer cylinder 54 are fixed by welding, and the right end of the cover body 55 and the cover body 56 welded to the introduction cylinder 51 are fixed by welding. Next, the inner periphery of the left end portion of the outer cylindrical body 54 and the outer periphery of the right end portion of the lead-out cylindrical body 53 are fixed by welding.

By manufacturing the catalyst pipes 34 in this order, the catalyst pipes 34 can be manufactured easily, so that the manufacturing cost of the exhaust device 5 can be kept low.

(Second embodiment)
<V-type engine 131>
A vertical type V-type engine 131 (hereinafter simply referred to as "engine 131") according to a second embodiment of the present invention will now be described with reference to FIGS. 8 to 11. FIG. Hereinafter, for convenience of explanation, the left side of the drawing in FIG. 8 is defined as the front side (front side) of the engine 131 . In addition, the description overlapping with that of the first embodiment will be omitted as appropriate.

8 and 9, the engine 131 has an engine main body 133, an air cleaner 134 arranged above the engine main body 133, and an exhaust device 135 arranged below and in front of the engine main body 133. The constituent elements of the engine 131 will be described in order below.

<Engine body 133>
8 and 9, the engine body 133 includes a crankcase 137, a first cylinder bank 138 extending forward left from the crankcase 137, a second cylinder bank 139 extending forward right from the crankcase 137, contains.

A crankshaft 141 is rotatably supported in the central portion of the crankcase 137 . The crankshaft 141 is rotatably provided around a rotation axis Y extending in the vertical direction. That is, the engine 131 is a vertical type engine in which the rotation axis Y of the crankshaft 141 extends vertically. A PTO shaft 142 (power take-off shaft: an example of an output section) is provided at the lower end of the crankshaft 141 . The PTO shaft 142 protrudes downward from the lower surface 137a of the crankcase 137 and extends vertically. A mounting member 143 is fixed to the lower front surface of the crankcase 137 with a pair of left and right bolts (not shown).

An engine mount 144 is arranged below the crankcase 137 . Crankcase 137 is attached to work implement P via engine mount 144 . For example, the working machine P is a riding lawn mower.

10 and 11, a support plate 145 (an example of a support member) is fixed to the first and second cylinder banks 138, 139 with a plurality of bolts (not shown). A first fixed plate 146 is fixed to the first cylinder bank 138 with a pair of bolts (not shown). A first connecting plate 147 is fixed to the first fixing plate 146 with a pair of bolts (not shown). A second fixing plate 148 (an example of a fixing member) is fixed to the second cylinder bank 139 with a pair of bolts (not shown). A second connecting plate 149 is fixed to the second fixing plate 148 with a pair of bolts (not shown).

<Air cleaner 134>
Referring to FIG. 8, air cleaner 134 has a cylindrical shape (canister shape) extending in the left-right direction. The air cleaner 134 is not arranged between the first and second cylinder banks 138 and 139 of the engine body 133 and is positioned above the first and second cylinder banks 138 and 139 .

<Exhaust device 135>
10 and 11, the exhaust system 135 includes first and second exhaust pipes 161 and 162, a catalyst 163, a catalyst pipe 164, an oxygen sensor 165, a temperature sensor 166, a muffler 167, It has

<Catalyst pipe 164>
Referring to FIG. 8, catalyst pipe 164 of exhaust system 135 is located in front of first and second cylinder banks 138 and 139 and is vertically separated from air cleaner 134 . The catalyst pipe 164 is positioned above the lower surface 137a of the crankcase 137. As shown in FIG.

10 and 11, a fixed stay 169 protrudes upward from the right side (one side in the longitudinal direction) of the outer peripheral surface of the catalyst pipe 164 . The fixed stay 169 is fixed to the second fixed plate 148 with bolts (not shown). A pair of left and right fixing pieces 170 protrude rearward from both left and right sides (both sides in the longitudinal direction) of the outer peripheral surface of the catalyst pipe 164 . The left fixed piece 170 is fixed to the first cylinder bank 138 with a bolt (not shown). The right fixing piece 170 is fixed to the second cylinder bank 139 with a pair of bolts (not shown). A pair of boss portions 171 are provided on both left and right sides of the outer peripheral surface of the catalyst pipe 164 . The pair of boss portions 171 are fixed to the support plate 145 with a pair of bolts (not shown).

<Muffler 167>
Referring to FIG. 11, a muffler 167 of an exhaust device 135 includes a muffler body 172, a plurality of partition walls (not shown), an inflow pipe 173, and a communication pipe ( not shown) and an exhaust tube 174 .

A pair of left and right fixed brackets 176 protrude rearward from the central portion in the left-right direction of the outer peripheral surface of the muffler main body 172 . The pair of left and right fixing brackets 176 are fixed to the mounting member 143 with a pair of left and right bolts (not shown). A pair of left and right fixed stays 177 protrude upward from left and right side portions of the outer peripheral surface of the muffler main body 172 . The left fixed stay 177 is fixed to the first connection plate 147 with a pair of bolts (not shown). The right fixed stay 177 is fixed to the second connection plate 149 with a pair of bolts (not shown).

<Effects of Second Embodiment>
The PTO shaft 142 protrudes from the lower surface 137a of the crankcase 137, and the catalyst pipe 164 is arranged above the lower surface 137a of the crankcase 137. As shown in FIG. By adopting such a configuration, it is possible to prevent the catalyst pipe 164 from protruding below the lower surface 137 a of the crankcase 137 in the vertical type engine 131 . Therefore, interference between the catalyst pipe 164 and the engine mount 144 can be suppressed.

A fixed stay 169 fixed to the second fixing plate 148 is provided on the right side (one side in the longitudinal direction) of the catalyst pipe 164, and both sides (both sides in the longitudinal direction) of the catalyst pipe 164 are provided with a fixed stay 169. A pair of left and right fixing pieces 170 fixed to the first and second cylinder banks 138 and 139 and a pair of left and right boss portions 171 fixed to the support plate 145 are provided. By adopting such a configuration, the catalyst pipe 164 can be fixed to the engine body 133 with good balance using a simple configuration. Therefore, it is not necessary to fix the catalyst pipe 164 to the frame around the engine body 133, and the fixing work of the catalyst pipe 164 can be facilitated.

This completes the description of the specific embodiments, but the present invention can be widely modified without being limited to the above embodiments.

1 V-type engine 5 exhaust system 33 catalyst 34 catalyst pipe 36 temperature sensor 41 muffler 51 introduction cylinder 52 inner cylinder 53 discharge cylinder 54 outer cylinder 55 lid 56 cover 58 first inlet 59 second inlet 61 Fixed piece 63 First reduced diameter portion 64 Tapered portion 65 Second mounting boss 66 Outlet 67 Connection flange 69 Second reduced diameter portion 70 Fixed piece P Working machine

Claims (11)

1. An exhaust system for an engine,
   an exhaust pipe connected to the engine body;
   a catalyst pipe connected to the exhaust pipe;
   a catalyst housed in the catalyst pipe,
   The catalyst pipe is
   an introduction cylinder connected to the exhaust pipe;
   an inner cylinder disposed on the downstream side of the introduction cylinder in the exhaust direction and covering the outer periphery of the catalyst;
   a lead-out cylinder disposed on the downstream side of the inner cylinder in the exhaust direction and provided with an exhaust gas lead-out port;
   An exhaust system for an engine, comprising: an outer cylinder disposed on the outer circumference of the inner cylinder and fixed to the lead-in cylinder and the lead-out cylinder.
2. The engine exhaust system according to claim 1, wherein the inner cylinder is welded to the introduction cylinder and is slidably fitted to the lead-out cylinder.
3. The lead-out cylinder has a first diameter-reduced portion whose diameter is reduced from the downstream side in the exhaust direction toward the upstream side,
   The inner cylindrical body is slidably fitted in the lead-out cylindrical body upstream of the first reduced diameter portion in the exhaust direction, and the outer cylindrical body is disposed downstream of the first reduced diameter portion in the exhaust direction. 3. The engine exhaust system according to claim 2, wherein the exhaust system is welded to the lead-out cylinder.
4. The outer cylindrical body has a second reduced diameter portion that decreases in diameter from the downstream side in the exhaust direction toward the upstream side,
   4. The apparatus according to claim 3, wherein the outer cylinder is welded to the introduction cylinder on an upstream side in the exhaust direction of the welding part of the introduction cylinder and the inner cylinder and the second reduced diameter part. Exhaust system of the described engine.
5. The engine exhaust system according to any one of claims 1 to 4, characterized in that said catalyst pipe further comprises a cover body arranged on the outer circumference of said introduction cylinder.
6. The catalyst pipe further includes a cover welded to the upstream end of the introduction cylinder in the exhaust direction,
   An end portion of the cover body on the upstream side in the exhaust direction is welded to the lid body, and an end portion of the cover body on the downstream side in the exhaust direction is welded to the outer cylindrical body. 3. An exhaust system for the engine described in .
7. The exhaust system further includes a muffler disposed downstream of the catalyst pipe in the exhaust direction,
   The engine exhaust system according to any one of claims 1 to 6, wherein a connection flange connected to the muffler is provided on the outlet cylinder on the outer periphery of the outlet port.
8. The engine exhaust system according to claim 7, characterized in that fixing pieces for fixing the catalyst pipe and the muffler protrude from the outer peripheral surfaces of the introduction cylinder and the outer cylinder.
9. The lead-out cylinder has a tapered portion that decreases in diameter from the upstream side toward the downstream side in the exhaust direction,
   The engine exhaust system according to any one of claims 1 to 8, wherein the tapered portion is provided with a mounting boss for mounting a temperature sensor.
10. A work machine comprising the engine exhaust system according to any one of claims 1 to 9.
11. an introduction cylinder provided with an introduction port for exhaust gas;
    an inner cylinder disposed on the downstream side of the introduction cylinder in the exhaust direction and covering the outer circumference of the catalyst;
    a lead-out cylinder disposed on the downstream side of the inner cylinder in the exhaust direction and provided with an exhaust gas lead-out port;
    an outer cylindrical body arranged on the outer periphery of the inner cylindrical body;
    A method for manufacturing a catalyst pipe comprising a cover body arranged on the outer periphery of the introduction cylinder,
    a step of fixing the introduction cylinder and the inner cylinder;
    a step of fixing the introduction cylinder and the outer cylinder;
    a step of fixing the outer cylindrical body and the cover body;
    A method for manufacturing a catalyst pipe, characterized by sequentially performing a step of fixing the lead-out cylinder and the outer cylinder.

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