CN1392920A - Exhaust system of IC engines - Google Patents

Abstract

An exhaust system of an engine having a gas purifier with a casing, to which an exhaust pipe is welded, comprises a first exhaust pipe (3) and the exhaust gas purifier (4) having a casing 20 made of first and second casing halves welded to each other. An upstream end (3b) of the first exhaust pipe 3 is connected to an exhaust manifold via a spherical joint (6) whereas a downstream end (3a) of the first exhaust pipe (3) is welded to the first casing half forming the top part of the casing (20) such that its welded joint (W1) does not overlap the welded joint (W2) between both casing halves. This configuration preventing both welded joints (W1, W2) from overlapping keeps the strength unreduced, and exhaust gas flows into the casing (20) only through the first exhaust pipe (3).

Description

engine exhaust system

technical field

The present invention relates to an exhaust system of an engine, and more particularly, to an exhaust system comprising an exhaust gas cleaner having a housing on which an exhaust pipe is welded.

Background technique

A conventional exhaust system for forming an exhaust passage for releasing combusted exhaust gases from an engine combustion chamber to the atmosphere is equipped with an exhaust gas cleaner for cleaning the exhaust gas, to which an exhaust pipe communicating with the exhaust port of the engine is connected. device.

For example, Japanese Patent Publication No. 11-13461 discloses a technique of coupling an exhaust gas discharge pipe coming out of each cylinder of a three-cylinder engine to a catalyst housing containing a catalyst (corresponding to the housing of the exhaust gas purifier). body). The catalyst housing consists of two split housing elements with flanges welded to each other. An exhaust outlet pipe from the first cylinder is welded at the junction of these housing elements, and an exhaust outlet pipe extending from the second cylinder and collecting the exhaust outlet pipe from the third cylinder is welded to one of the housing elements. An O2 sensor mount is formed on the other housing element.

In the conventional technique reviewed above, since the exhaust gas output pipe from the first cylinder is welded to the weld seam of the two housing elements of the catalyst housing, the weld seams overlap and their strength decreases at the overlap. On the other hand, the vibration of the engine is transmitted to the exhaust gas output pipe, and the load generated by the vibration acts on the weld between the catalyst housing and the exhaust gas output pipe, generating a stress. Therefore, there is a problem that cracks are easily generated at the overlapping portion where the strength is reduced due to the load due to the vibration of the exhaust gas outlet pipe acting on the weld. In addition, since the mount for the O2 sensor is welded to the weld between two housing elements, there is a problem that the O2 sensor is limited to the position of the other housing element.

disclosure of invention

Under these conditions, a common object of the inventions described in claims 1 to 4 is to increase the durability of an engine exhaust system having an exhaust gas cleaner with a housing on which an exhaust pipe is welded. . An object of the invention recited in claim 2 is to improve exhaust efficiency. An object of the invention recited in claim 3 is to ensure a greater degree of freedom in the placement of the oxygen concentration sensor on the housing. An object of the invention recited in claim 4 is to prevent thermal damage from being generated by the exhaust gas sensor and to improve the durability of the sensor and the catalyst. An object of the invention recited in claim 5 is to make coupling of the exhaust pipe downstream of the exhaust gas cleaner easier.

According to the invention as recited in claim 1 there is provided an engine exhaust system having an upstream exhaust duct allowing exhaust gases to flow from the engine, a housing consisting of two housing halves welded together and a downstream exhaust pipe having a downstream end welded to the housing, wherein the upstream end is connected to the upstream exhaust pipe through a ball joint, and the downstream end is welded to one of the shells body half so that its welds do not overlap with those of the housing half, and the exhaust gas flows into the housing only through the downstream exhaust pipe.

According to the invention recited in claim 1, since part of the vibration of the engine transmitted to the upstream exhaust pipe is absorbed by the ball joint by relative sliding along the spherical shape between the upstream exhaust pipe and the downstream exhaust pipe, it is prevented from reaching as only Some exhaust pipes that introduce exhaust gas into the downstream exhaust pipe of the exhaust pipe in the shell do not have a large load generated by this vibration to act on the weld between the downstream exhaust pipe and the shell, which can prevent the Cracks appear. Even when vibration that cannot be effectively absorbed by the ball joint is transmitted to the downstream exhaust pipe and the load generated by the vibration acts on the weld, not only because the transmitted vibration is attenuated by the ball joint compared to a structure without the ball joint, but also Because the weld seam between the downstream end of the downstream exhaust pipe and the casing halves does not overlap with the weld seam connecting the two casing halves, the weld seam maintains high strength, greatly reducing the generation of cracks in the weld seam.

Therefore, the following effects are provided. Since the vibration of the engine transmitted to the upstream exhaust pipe is absorbed by the ball joint, even the vibration that the ball joint cannot absorb is transmitted to the downstream exhaust pipe that is the only exhaust pipe that introduces the exhaust gas into the casing, not only because of the transmitted The vibration itself is attenuated to a certain extent by the ball joint, and because the weld between the downstream exhaust pipe and the shell has high strength, the cracks generated at the weld are greatly reduced, with the upstream exhaust pipe welded thereon The exhaust system of the casing has been improved in durability.

The invention recited in claim 2 is based on the exhaust system recited in claim 1, wherein said casing is located at a height lower than said upstream end, and one of said casing halves constitutes the top of said casing.

According to the invention recited in claim 2, since the downstream exhaust pipe extends downward from its upstream end and is coupled to the first casing half forming the top of the casing at a height lower than the upstream end, the first exhaust pipe can be shortened. and the arc decreases.

Therefore, in addition to the effects of the invention described in claim 1, the short and small arc structure of the first exhaust pipe can reduce the flow path resistance, make the exhaust gas in the exhaust system discharge smoothly, and improve the exhaust efficiency, simplifying the downstream The layout of the exhaust pipe.

The invention of claim 3 is based on the engine exhaust system of claim 2, characterized in that the exhaust gas purifier includes a catalyst housed in a housing, and an exhaust gas inlet leading from the downstream exhaust pipe to the housing is located at Upstream of the catalyst, the upstream portion of the other half of the housing upstream of the catalyst forms a mount for mounting an oxygen concentration sensor for detecting the oxygen concentration in the exhaust gas.

According to the invention recited in claim 3 , the oxygen concentration sensor detects the oxygen concentration in the exhaust gas introduced into the casing from the exhaust gas inlet located upstream of the catalyst at a position upstream of the catalyst. However, since the mounting seat for installing the oxygen concentration sensor is formed on the part upstream of the catalyst on the housing half, which is different from the housing half on which the downstream exhaust pipe is connected, the mounting seat is located on the housing half. The location limitation of the upstream part of the catalyst has been improved.

Therefore, in addition to the effect described in claim 2, the following effect is provided in that the mounting seat provided in the casing half not connected to the downstream exhaust pipe reduces the limitation on the positioning itself, providing the position of the oxygen concentration sensor Provides greater freedom. From the perspective of its detection accuracy and response, the selection of the best position of the oxygen concentration sensor is optimized.

The invention according to claim 4 is based on the engine exhaust system according to claim 3, characterized in that the weld joint connecting the downstream end and the half of the casing is located upstream of the above catalyst, a heat insulating cover covering the outside of the casing Fastened to the housing at multiple fixing points upstream of the catalyst.

According to the invention recited in claim 4, since the heat insulating cover is provided outside the case, thermal damage to the components surrounding the case can be avoided. Additionally, since the welds are located in the housing upstream of the catalyst and the heat shield is secured to the housing at multiple fixed points upstream of the catalyst, the housing is in close proximity to the downstream exhaust pipe and one of the housing halves due to the additional stiffness of the heat shield. The location of the weld seam in between increases stiffness.

Therefore, in addition to the effects of the invention described in claim 3, the following effects are provided. That is, thermal damage to elements surrounding the housing can be prevented by the heat insulating cover. In addition, in the part of the casing located upstream of the catalyst, since the heat insulation cover fixed at multiple fixed points upstream of the catalyst can suppress the vibration transmitted from the downstream exhaust pipe, the vibration of the entire casing can be suppressed, and the storage in the Durability of the catalyst in the housing.

The invention recited in claim 5 is based on the engine exhaust system recited in claim 1, characterized in that a second exhaust pipe is coupled to the downstream end of the housing, and a coupling flange is provided on the second exhaust pipe. A third exhaust pipe is connected to the above-mentioned second exhaust pipe by fastening elements, and the above-mentioned second exhaust pipe is bent so as to guide a straight line perpendicular to the joint surface of the above-mentioned coupling flange to deviate from the above-mentioned shell direction of the body axis.

According to the invention described in claim 5, the coupling plane of the second exhaust pipe coupling flange deviated from the housing axis of the exhaust gas cleaner due to bending is directed in a direction deviated from the housing axis, and the coupling surface can be oriented not to face a The element arranged axially towards the exhaust gas cleaner.

Therefore, in addition to the effects of the invention described in claim 1, the following effects are provided. That is, the coupling plane of the coupling flange is directed in a direction deviated from the axis of the housing due to the bending of the second exhaust pipe, so that the coupling surface is oriented not towards an element arranged axially towards the exhaust gas cleaner, when the second row When the air pipe is connected to the third exhaust pipe, even if the fuel tank is arranged to face the exhaust gas cleaner at a relatively short distance in the axial direction, the tool for fixing the fastening element can be brought close to the coupling flange without interfere with the component. This makes it easier to couple the coupling flange and the third exhaust pipe with the fastening member, and can improve the efficiency of coupling the second exhaust pipe and the third exhaust pipe.

In the terminology used herein, the terms "upper" and "lower" refer to directions and locations relative to an engine exhaust system when secured in place in an automobile or other vehicle and equipment. Similarly, the terms "upward" and "downward" are used with respect to the direction of flow of exhaust gas.

Brief description of the drawings

1 is a plan view schematically showing a part of an engine exhaust device to be mounted on a vehicle to which the present invention is applied;

Figure 2 is a side elevational view schematically showing a portion of the engine exhaust of Figure 1;

Fig. 3 is a sectional view of a ball joint;

Fig. 4 is a part of the exhaust gas purifier taken along the direction perpendicular to the dividing surface of the housing;

Fig. 5 is a partial cross-sectional view of the heat-insulating cover taken along the direction indicated by arrow V in Fig. 4;

Fig. 6 is the view of the exhaust gas purifier housing taken along the direction perpendicular to its dividing plane;

Figure 7 is a sectional view showing the connection of the exhaust pipe to the housing;

Fig. 8 is a perspective view showing the positional relationship between the exhaust system and the fuel tank in Fig. 1;

Figure 9 is a plan view similar to Figure 1, showing the positional relationship between the exhaust system and the fuel tank in Figure 1; and

Fig. 10 is a side view similar to Fig. 2, showing the positional relationship between the exhaust system and the fuel tank in Fig. 1 .

The best way to realize the invention

Embodiments of the present invention will now be described with reference to FIGS. 1 to 10 .

Referring first to Fig. 1 and Fig. 2, Fig. 1 is a plan view schematically showing a part of a one-line four-cylinder engine exhaust system according to an embodiment of the present invention installed in a vehicle, and Fig. 2 is a side elevation view thereof, The exhaust system 1 is configured to purify exhaust gas, which is combustion gas released from a combustion chamber of an engine (not shown) having reciprocating pistons, and release it into the atmosphere, along an upstream The sequence to the downstream direction includes an exhaust manifold 2 connected to the engine cylinder head E, a first exhaust pipe 3, an exhaust gas purifier 4 and a second exhaust pipe 5, and includes a third exhaust pipe 40 and An auxiliary air return duct 41 (best shown in its entirety in FIGS. 8 to 10 ) is provided downstream of them. Downstream of them, the exhaust system also includes, a main return duct and a tailpipe (neither shown), the exhaust gases being directed through the path defined by these elements and discharged into the atmosphere from the tailpipe.

The exhaust manifold 2 is composed of four branch pipes 21 to 24, which are connected through a cylinder head E to a shaft rotating along the crankshaft of the engine, and a collecting pipe 2a which unites these branch pipes 21 to 24 into a single pipe. The exhaust port of each cylinder is aligned with the axial direction of the cylinder (along the direction shown by arrow A in Figure 1). The downstream end 2a1 of the collecting pipe 2a is connected with the upstream end 3a of the first exhaust pipe 3 through a ball joint 6 which will be explained later, while the downstream end of the first exhaust pipe 3 is connected with the housing 20 of the exhaust gas cleaner 4 . Thus, the exhaust manifold 2 upstream of the ball joint 6 forms an upstream exhaust pipe, while the first exhaust pipe 3 downstream of the ball joint 6 forms a downstream exhaust pipe.

3, the ball joint 6 includes an upstream flange 7 welded to the outer circumference of the collecting pipe 2a, and a downstream flange 8 welded to the outer circumference of the upstream end 3a of the first exhaust pipe 3, the The first exhaust pipe 3 is a double pipe structure consisting of an inner pipe 31 and an outer pipe 32, both of which are cylindrical pipes. The downstream flange 8 forms a spherical seat 8a defining a spherical seat surface convex in the downstream direction, while the upstream flange 7 forms a flat seat 7a defining a plane.

The ball joint 6 includes a spherical gasket 9 positioned between the upstream and downstream flanges 7, 8 for engagement with the outer circumference of the downstream end 2a1. The spherical packing 9 has a planar portion 9a disposed at an upstream position and a spherical portion 9b disposed at a downstream position, the planar portion 9a defining a plane in contact with the planar seat 7a, the spherical portion 9b defining a contact with the planar seat 7a. The spherical surface that the spherical seat 8a contacts.

The upstream flange 7 forms two bolt holes 12 that allow the bolts 11 inserted into the two through holes 10 formed in the downstream flange 8 to pass through, thereby tightening and fixing the bolt 11 to the upstream flange 8 with a nut 14. rim 7 while compressing a coil spring 13 surrounding the bolt 11 between the head of the bolt 11 and the downstream flange 8 . The diameter of each through hole 10 is larger than the outer diameter of the bolt 11 so as to provide a clearance allowing relative sliding between the spherical seat 8a and the spherical portion 9b. When the vibrations of the engine are transmitted to the manifold 2, these vibrations are absorbed by the sliding motion along the spherical surface occurring between the spherical seat 8a and the spherical portion 9b at the ball joint 6, thus preventing or suppressing the vibrations from going to the first exhaust pipe 3 transmission.

As shown in FIG. 2 , the exhaust gas cleaner 4 coupled to the first exhaust pipe 3 is positioned at a height lower than the upstream end 3 a of the first exhaust pipe 3 when the exhaust system 1 is fixed to the vehicle. The exhaust gas purifier 4 has a housing 20 containing a three-way catalyst 15 for purifying NOx (nitrogen oxide), HC (hydrocarbons) and CO (carbon monoxide) in the exhaust gas. The first exhaust pipe A downstream end 3b extending downward from the upstream end 3a is welded to the housing 20 at a weld seam W1 thus formed (see FIGS. 4 to 7).

More specifically, referring to FIGS. 4 and 5, the shell 20 made of sheet metal has an upstream portion 20a located upstream of the upstream end surface 15a of the substantially cylindrical catalyst 15, a substantially frusto-conical profile and positioned downstream of the downstream portion 20a. part 20b, and a substantially cylindrical central part 20c located between the upstream part 20a and the downstream part 20b in the flow direction of the exhaust gas, the housing 20 consists of substantially semicylindrical first and second housing halves 21, 22 are formed, the two halves 21, 22 being two divisions along a division plane P passing through the substantially horizontal axis L1 of the cylinder of the central portion 20c (see FIG. 7). In this embodiment, as shown in Figures 1 and 2, since most of the housing 20 above the horizontal plane including the top of the housing 20 is defined by the first housing half 21, the first housing half 21 and the second housing half The housing halves 22 form an upper housing half and a lower housing half, respectively.

As shown in FIG. 6, the first and second casing halves 21, 22 have flanges 21a, 22a along their peripheral edges, except for a downstream portion 20b forming a groove which will be described below. The body halves 21, 22 are joined together by welding their flanges 21a, 22a along the entire circumference. Since the flange 21a of the first housing half 21 protrudes further outward than the flange 22a of the second housing half 22, the second housing half 22 is welded to the first housing half along its outer peripheral edge. The bottom surface of the flange 21a of 21. The weld shown in Figure 6 is indicated by the reference numeral W2. The protrusions B1, B2 belonging to the flange 21a of the upstream portion 20a of the first housing half 21 and the protrusions B3, B4 of the flange 21a belonging to the downstream portion 20b form a total of four bolt holes C1 to C4, wherein each two are substantially Positioned symmetrically with respect to a plane including the axis L1 and vertically across the dividing plane P. These bolt holes C1 to C4 accommodate four bolts D1 to D4 (see FIG. 4 ) which fix a heat insulating cover 30 to be described later on the casing 20, covering the casing 20 through a gap. external.

Referring to FIGS. 4 to 6, the upstream portion of the first housing half 21 belonging to the upstream portion 20a includes a substantially flat slope 21b inclined toward the downstream direction from a portion near the upstream end of the flange 21a, while the second housing half 22 belongs to The upstream portion of the upstream portion 20a includes an inclined surface 22b inclined downstream from a portion near the upstream end of the flange 22a, and two inclined downwards along a direction perpendicular to the axis L1 on the dividing plane P (hereinafter referred to as "vertical direction"). ) side slopes 22c close to each other.

The downstream ends of the first and second housing halves 21, 22 are formed with semicircular grooves for forming fitting holes for receiving the second housing coupled with the downstream end of the downstream portion 20b of the housing 20. Exhaust pipe 5. The peripheral edge of the fitting hole and the outer peripheral surface of the second exhaust pipe 5 are joined together by welding their entire circumferences at the weld W3. As shown in Figures 8 to 10, a coupling flange 16 arranged downstream of the end of the second exhaust pipe 5 forms an exhaust channel downstream of the second exhaust pipe 5; The coupling flange 42 at the upstream end of the third exhaust pipe 40 is connected with the coupling flange 16 through three bolts 45 and nuts 46 as fasteners, thereby continuously coupling the second exhaust pipe 5 to the third exhaust pipe 40 on.

Referring to FIG. 7, a cylindrical boss portion is formed on an inclined surface 21b of the first housing half 21 to define a hole as a discharge inlet through which exhaust gas flows into the housing 20. Referring to FIG. The outer pipe 32 of the first exhaust pipe 3 is engaged with the outer circumference of the boss portion 24, and they are welded over the entire circumferential length to form a weld W1. In this case, the weld W1 is selected not to overlap the weld W2 of the casing 20 .

In the casing 20, the upstream end surface of the catalyst 15 having a plurality of thin air passages allowing the exhaust gas to flow therethrough is located slightly downstream of the downstream end of the hole 23 in the axial direction of the axis L1 of the casing 20, and the first exhaust pipe 3 The axis L2 of the downstream end 3b is generally directed towards the center of the upstream end face 15a.

As shown in FIG. 5, at the upstream portion of the second housing half 22, a side slope 22c forms a mounting seat 27 having an insertion hole 26 for installing an oxygen concentration sensor 25 therein. The oxygen depth sensor 25 is used to detect the oxygen concentration in the exhaust gas as a characteristic of the exhaust gas. This oxygen concentration sensor 25 is fixed to the mounting seat 27 such that its detection portion occupies a sufficient position immediately after entering the hole 23 from the viewpoint of detection accuracy and response.

Referring to FIGS. 4 and 5, in the exhaust gas purifier 4, the heat insulating cover 30 covering the outside of the housing 20 through a gap is formed by a first housing half 21 and a second housing half 22 connected respectively. A cover half 31 and a second cover half 32 are formed. The first cover half 31 covers it along with the outer contour of the first housing half 21, and the upstream part of the first cover half 31 covering the upstream part 20a of the housing 20 has a first surrounding welded to the housing 20. An exhaust pipe 3 partially covers the surrounding portion 31a of the upstream portion. The surrounding portion 31a has an extended side portion 31b which is gradually extended in the vertical direction from the central portion of the first cover half 31 toward the flange 21a of the first housing half 21 in the upstream direction. The first cover half 21 forms a plurality of ventilation holes at the position where the temperature of the catalyst 15 is the highest in the exhaust gas purifier 4, so that the hot air in the gap between the housing 20 and the heat insulating cover 30 is surrounded by the relatively cooler exhaust gas purifier 4. temperature instead. Overheating of the housing 20 is thereby avoided. The second cover half 32 covers the central and downstream portions of the second casing half 23 with their outer contours, the downstream end of which reaches a position close to the coupling flange 16 of the second exhaust pipe 5 .

The first and second cover halves 31, 32 have four fixing portions F1 to F4 and G1 to G4, respectively, which form four bolt holes C1 to C4 corresponding to the four bolt holes C1 to C4 of the flange 21a of the first housing half 21. bolt holes (not shown). Among them, two upstream fixing portions F1 and F2 of the first cover half 31 are formed in the two extended side portions 31b, and downstream two fixing portions F3 and F4 are formed at the downstream end. The upstream fixing portions G1 and G2 of the second cover half 32 are formed in positions corresponding to the fixing portions F1 and F2 in a part along the flange 21a extending in the upstream direction from the front end covering the central portion of the second cover half 32, And the two downstream fixing portions G3 and G4 are formed at positions corresponding to the fixing portions F3 and F4. Thus, with the protrusions B1 to B4 being sandwiched between the fixing portions F1 to F4 of the first cover half 31 and the fixing portions G1 to G4 of the second cover half 32, the bolts D1 to D4 are inserted and held by the nuts H1 to H4. Fasten, thereby connecting the casing 20 and the heat insulating cover 30 together.

In the bolt holes C1 to C4 which are fixing parts of the casing 20 which fixes the heat shield cover 30 with the fixing means bolts D1 to D4 and nuts H1 to H4, the positions of the upstream bolt holes C1 to C2 are located at the catalyst 15 as shown in FIG. Upstream of the upstream end surface 15a, and they are located in the range S occupied by the weld W1 in the axial direction of the axis L1. Therefore, the positions of the bolt holes C1 to C2 are close to the welding seam W1 of the first exhaust pipe 3 and the housing 20 .

Referring to FIGS. 8 to 10, in a vehicle equipped with an engine, a fuel tank 43 is positioned at a position opposite to the exhaust gas cleaner 4 in the axial direction of the axis L1 of the housing 20 at a relatively short distance from the exhaust gas cleaner 4. subsequent location. The third exhaust pipe 40 bends around the fuel tank 43 and is coupled to the auxiliary air return pipe 41 located beside the fuel tank 43 . Reference numeral 44 denotes two brackets for fixing the third exhaust pipe 40 to the vehicle body.

The second exhaust pipe 5 bends slightly downward from the upstream end associated with the exhaust gas purifier toward the auxiliary air return pipe 41 in a direction deviated from the axis L1 of the housing 20 (see FIGS. 9 and 10 ). Thus, the coupling face 16a of the coupling flange 16 is oriented away from the fuel tank 43, whereas a line perpendicular to the coupling face 16a points in this deviating direction. Thus, as shown in FIGS. 9 and 10 , in this embodiment, the second exhaust pipe 5 is bent such that the coupling surface 16 a faces a vertically lower position of the auxiliary return pipe 41 close to the fuel tank 43 .

Therefore, when the third exhaust pipe 40 having the coupling flange 42 is coupled to the second exhaust pipe 5, a tool for fastening the nut 46 to the bolt 45, such as a socket wrench, can be removed from the fuel tank 43. The bottom extends to a coupling flange 42 coupled to the coupling flange 16 with three bolts 45 inserted into the coupling flange 16 and nuts 46 fastening the bolts 45 without interfering with the fuel tank 43 .

The operation and effect of the embodiment having the above structure will be described below.

After the engine is started, the exhaust gas passing through the exhaust passage is purified by the exhaust gas purifier 4, and then discharged into the atmosphere. Vibrations generated by the movement of the engine are transmitted to the exhaust system 1 . Part of the vibration transmitted to the exhaust manifold 2 is absorbed by relative sliding along the spherical surface between the spherical seat 8a and the spherical portion 9b of the ball joint 6, and avoids being transmitted to The first exhaust pipe 3 of the exhaust pipe. Therefore no large load due to such vibration acts on the weld between the first exhaust pipe 3 and the housing 20, and cracks in the weld W2 can be avoided. In addition, even when vibrations that cannot be effectively absorbed by the ball joint 6, such as large vibrations beyond the sliding range between the exhaust manifold 2 and the first exhaust pipe 3 of the ball joint 6, or in the axial direction of the flow direction of the collecting pipe 2a When the vibration generated at the downstream end 2a of the exhaust manifold 2 is transmitted to the first exhaust pipe 3 and the load generated by the vibration acts on the weld, these vibrations themselves are also absorbed by the ball joint 6 compared with the structure without the ball joint 6. weakened, and the weld W1 between the downstream end 3b of the first exhaust pipe 3 and the first casing half 21 and the weld W1 connecting the first and second casing halves 21, 22 of the casing 21 W2 overlaps. Therefore, the weld W1 has high strength, and the possibility of cracks is greatly reduced.

Thereby, the following effects are ensured. That is, since the vibration of the engine transmitted to the exhaust manifold 2 is absorbed by the ball joint 6, even the vibration that the ball joint 6 cannot absorb is transmitted to the first exhaust pipe which is the only exhaust pipe for introducing exhaust gas into the housing 20. 3. Not only because the transmitted vibration itself is weakened to a certain extent by the ball joint 6, but also because the welding seam W1 between the first exhaust pipe 3 and the casing 20 has high strength, which greatly reduces the vibration transmitted to the first row The exhaust system having the casing 20 on which the first exhaust pipe 3 is welded is improved in durability due to cracks generated at the weld W1 due to the vibration of the air pipe 3 .

Since the first exhaust pipe 3 extends downward from its upstream end 3a and is coupled to the first housing half 21 forming the top of the housing 20 at a height lower than the upstream end 3a, the first exhaust pipe 3 can be shortened and The arc decreases. The short and small arc structure of the first exhaust pipe 3 can reduce flow path resistance, make exhaust gas in the exhaust system discharge smoothly, improve exhaust efficiency, and increase the effect of simplifying the layout of the first exhaust pipe.

The oxygen concentration sensor 25 detects the oxygen concentration in the exhaust gas introduced into the housing 20 from the hole 23 located upstream of the catalyst 15 at a position upstream of the catalyst 15 . However, since the mounting seat 27 for installing the oxygen concentration sensor 25 is formed on the part upstream of the catalyst 15 on the second casing half 22, the second casing half 22 is different from the one on which the first exhaust pipe 3 is welded. The position limitation of the first housing half 21 , the mounting seat 27 in the upstream part of the catalyst 15 of the housing 20 is improved.

Therefore, the mounting seat 27 can be arranged on the half of the housing that is not connected to the downstream exhaust pipe, which reduces the restriction on the position of the mounting seat 27 and provides greater freedom for the position of the oxygen concentration sensor 25 . This is effective for properly placing the oxygen concentration sensor 25 to optimize its detection accuracy and response.

Since the heat insulating cover 30 is provided to cover the exterior of the housing 20, thermal damage to components surrounding the housing 20 can be avoided. In addition, since the weld seam is located upstream of the upstream end surface 15a of the catalyst 15 in the casing 20 and the heat insulating cover 30 is fixed to the casing with bolts D1, D2 and nuts H1, H2 and bolt holes C1, C2 as two fixing points upstream of the catalyst 15. On the body 20, the shell 20 has increased rigidity at the position close to the weld W1 between the first exhaust pipe 3 and the first shell half 21, and if the heat insulating cover 30 is added, the rigidity will be improved. In addition, since the bolt holes C1 and C2 are located within the range S occupied by the weld W1 in the direction of the axis L1 and are close to the weld W1 and the mounting seat 27, the vibration transmitted from the first exhaust pipe 3 can be effectively weakened, and the It can effectively prevent the oxygen concentration sensor 25 installed on the mounting base 27 from vibrating.

Accordingly, the following effects are provided. That is, thermal damage to elements surrounding the casing 20 can be prevented by the heat insulating cover 30, and at the portion of the casing 20 upstream of the catalyst 15, the vibration transmitted from the first exhaust pipe 3 can be provided by the user positioned upstream of the catalyst 15. The bolts D1, D2 and nuts H1, H2 are used to suppress the heat insulation cover 30, which can prevent the overall vibration of the casing 20 and improve the durability of the catalyst 15 housed in the casing 20.

The downstream end of the second exhaust pipe 5 associated with the housing 20 is provided with a coupling flange 16 for connecting the third exhaust pipe 40 to the second exhaust pipe 5 with bolts 45, the second exhaust The pipe 5 is bent, and the straight line perpendicular to the coupling plane 16a of the coupling flange 16 is guided to a direction deviated from the axis L1 of the housing 20, so that the coupling surface 16a of the coupling flange of the second exhaust pipe 5 is bent away from the exhaust gas purifier 4 The axis L1 of the shell Hugh 20. It is thus possible to orient the coupling surface 16 a not completely towards the fuel tank 43 , which is positioned in the axial direction L1 towards the exhaust gas cleaner 4 .

Therefore, the following effects can be provided. That is, since the second exhaust pipe 5 is bent to guide the coupling plane 16a of the coupling flange 16 to a direction deviated from the axis L1 of the housing 20, the coupling surface 16a is oriented not to face the fuel tank 43, which is positioned at The axial direction L1 faces the exhaust gas purifier 4, and when the second exhaust pipe 5 is coupled with the third exhaust pipe 40, even if the fuel tank 43 is arranged to face the exhaust gas purifier 4 at a relatively short distance in the axial direction L1, A socket wrench for fastening the nut 46 to the bolt 45 can also be brought close to the coupling flange 42 without interfering with the fuel tank 43 . Therefore, it is easier to connect the coupling flange 16 and the coupling flange 42 of the third exhaust pipe 40 with the bolts 45 and nuts 46 , and the efficiency of coupling the second exhaust pipe 5 and the third exhaust pipe 40 can be improved.

A modified structure of an embodiment partially modified from the above-described embodiment will be described below.

Although the axis L1 of the exhaust gas cleaner 4 is oriented in a substantially horizontal direction in the foregoing embodiments, the present invention is also applicable to an exhaust gas cleaner 4 having a vertical axis. Although the first exhaust pipe 3 is described as directly welded to the first housing, this embodiment is modified to couple the first exhaust pipe 3 with a flange welded to the first housing half 21 . It is also possible to use three or more upstream fixing points instead of two for fixing the insulating cover 30 to the housing 20 . Although the exhaust gas purifier 4 includes a three-way catalyst 15, the catalyst is not limited to the three-way, but may be, for example, only used to purify NOx, or an exhaust gas purifier 4 without a catalyst may also be used.

Although the engine is mounted on a vehicle in the foregoing embodiments, the exhaust system of the present invention can be used in any vehicle or equipment equipped with an engine. In addition, although the second exhaust pipe is bent so that the entire coupling surface area of the coupling flange does not face the fuel tank in the foregoing embodiments, it is sufficient that at least a part of the coupling surface does not face the fuel tank to prevent the fastening for fixing. The tooling of the element interferes with the fuel tank.

Claims (5)

1. engine exhaust system, has a upstream exhaust pipe that allows waste gas to flow out from motor, one has the catalytic converter of a housing that is made of two case half that weld together, and one have a downstream row tracheae that is welded to the downstream on this housing, it is characterized in that:

Above-mentioned upstream extremity connects with above-mentioned upstream exhaust pipe by a spherical joint, above-mentioned downstream is welded on one of them case half, make its weld seam not overlapping, and above-mentioned waste gas only flow in the above-mentioned housing by above-mentioned downstream row tracheae with the weld seam of above-mentioned case half.

2. vent systems according to claim 1, wherein above-mentioned housing are positioned at a height that is lower than above-mentioned upstream extremity, and above-mentioned one of them case half has constituted the top of above-mentioned housing.

3. vent systems according to claim 2, wherein above-mentioned catalytic converter comprises that one is received in the catalyzer in the above-mentioned housing, one exhaust gas entrance that leads to above-mentioned housing from above-mentioned downstream row tracheae is positioned at the upstream of above-mentioned catalyzer, a upstream portion that is positioned at another above-mentioned case half of above-mentioned catalyzer upstream forms a fitting seat, is used to install an oxygen concentration sensor that is used to detect oxygen in waste gas.

4. engine exhaust system according to claim 3, the weld seam that wherein connects above-mentioned downstream and above-mentioned one of them case half is positioned at the upstream of above-mentioned catalyzer, and an insulation cover that covers above-mentioned outside is fixed on the above-mentioned housing at a plurality of immovable points that are positioned at above-mentioned catalyzer upstream.

5. vent systems according to claim 1, wherein a second exhaust pipe is connected to above-mentioned housing downstream, one connecting flange is arranged on the downstream of above-mentioned second exhaust pipe, with fastener one the 3rd outlet pipe is connected on the above-mentioned outlet pipe, above-mentioned second exhaust pipe bending is directed to the direction that departs from above-mentioned housing axis with a straight line perpendicular to above-mentioned connecting flange conjunction plane.

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