Engine exhaust device

An engine exhaust device includes: a first catalyst; a second catalyst; and a connecting member shaped into a tube and forming a part of the exhaust path, and connecting the first catalyst to the second catalyst. A downstream end surface of the first catalyst and an upstream end surface of the second catalyst form a dihedral angle within a range from 60 degrees to 120 degrees. A part of the upstream end surface of the second catalyst is close to and faces a part of a side surface of the first catalyst. On a cross-section including a central axis of the first catalyst and being parallel to a central axis of a second catalyst, a length of the part of the side surface of the first catalyst is longer than or equal to 10% and shorter than 50% of an entire length of the first catalyst.

TECHNICAL FIELD

The present disclosure relates to an engine exhaust device.

BACKGROUND ART

A plurality of catalysts for purifying exhaust gas are conventionally arranged in series upstream of an exhaust path with a high exhaust gas temperature of a vehicle engine, such as a diesel engine or a gasoline engine.

It is known that, at this time, one or more of the catalysts, which is/are located upstream in the flow of exhaust gas, is/are placed lateral to the other(s), which is/are located downstream in the flow of exhaust gas, to reduce the area for the catalysts (see, e.g., Patent Document 1).

Patent Document 1 discloses disposing a first exhaust gas treatment unit substantially perpendicular to a second exhaust gas treatment unit in a housing so that a side surface of the second exhaust gas treatment unit overlaps at least 50% of the upstream part of the first exhaust gas treatment unit.

CITATION LIST

Patent Document

PATENT DOCUMENT 1: Japanese Unexamined Patent Publication (Japanese Translation of PCT Application) No. 2012-529592

SUMMARY OF THE INVENTION

Technical Problem

However, in Patent document 1, the exhaust gas, which has passed through the second exhaust gas treatment unit, flows into the first exhaust gas treatment unit. At this time, it is difficult to obtain a uniform flow of exhaust gas between the overlap and the other positions. This may reduce the efficiency in using the first exhaust gas treatment unit at the overlap. In addition, the overlap causes a non-uniform flow of exhaust gas, which may increase the flow rate of the exhaust gas in some positions, in which the flow resistance may increase to decrease the output. Further, the overlap is so small that the mountability of control devices such as various sensors may decrease in a space between the first and second exhaust gas treatment units.

It is an object of the present disclosure to provide a compact engine exhaust device including a plurality of catalysts and exhibiting excellent efficiency in use, function, and performance of a catalyst, and mountability of control devices.

Solution to the Problem

In order to achieve the object, the present disclosure is directed to the following engine exhaust device, including a plurality of catalysts. A part of a side surface of a first catalyst is close to and faces a part of an upstream end surface of a second catalyst. The part of the side surface of the first catalyst has a length shorter than a predetermined range.

Specifically, an engine exhaust device according to a first aspect of the present disclosure includes: a first catalyst provided in an exhaust path of the engine to purify exhaust gas discharged from the engine; a second catalyst placed downstream of the first catalyst in a flow of the exhaust gas to purify the exhaust gas, which has passed through the first catalyst; and a connecting member shaped into a tube and forming a part of the exhaust path, and connecting the first catalyst to the second catalyst. A downstream end surface of the first catalyst and an upstream end surface of the second catalyst form a dihedral angle within a range from 60 degrees to 120 degrees. A part of the upstream end surface of the second catalyst is close to and faces a part of a side surface of the first catalyst. On a cross-section including a central axis of the first catalyst and being parallel to a central axis of a second catalyst, a length of the part of the side surface of the first catalyst is longer than or equal to 10% and shorter than 50% of an entire length of the first catalyst.

According to the first aspect, the part of the side surface of the first catalyst is close to and faces the part of the upstream end surface of the second catalyst. The part of the first catalyst, which is close to and faces the part of the upstream end surface of the second catalyst, has a length shorter than the predetermined range. As a result, the exhaust device achieves a compact size, and exhibits improved efficiency in use, function, and performance of a catalyst, and mountability of control devices.

According to a second aspect, in the first aspect, the connecting member includes: a first opening located upstream in the flow of the exhaust gas; a second opening located downstream in the flow of the exhaust gas; and a bend connecting the first opening to the second opening. The first catalyst is inserted in a downstream end surface of the first catalyst first into the connecting member through the first opening. The second catalyst is inserted in an upstream end surface of the second catalyst first into the connecting member through the second opening.

According to the second aspect, the first and second catalysts are inserted into the connecting member. This configuration requires no connecting flange, which is needed if the first and second catalysts are connected to the upstream and downstream ends of the connecting member. This contributes to downsizing of the exhaust device.

According to a third aspect, in the second aspect, the bend of the connecting member includes: a first wall facing the downstream end surface of the first catalyst; and a second wall smoothly connected to the first wall, and facing the upstream end surface of the second catalyst. The first wall includes: a wall transition smoothly extending from the second opening; a wall slope smoothly connected to the wall transition, and rising up toward the first catalyst; and a wall step smoothly connected to the wall slope and the second wall.

According to the third aspect, out of the first wall facing the downstream end surface of the first catalyst, the wall step continuous with the second wall facing the upstream end surface of the second catalyst protrudes more than the wall transition toward the first catalyst. This can reduce the concentrated flow of exhaust gas, which has passed through the first catalyst and reaches the wall step, toward the end of the second catalyst, at which the wall transition exists. This can also promote the flow of exhaust gas to the part of the second catalyst, which is close to and faces the part of the first catalyst. Such features improve the uniformity of the flow of exhaust gas, which has passed through the first catalyst, so that the exhaust device can exhibit improved efficiency in use, function, and performance of the second catalyst, and mountability of control devices.

According to a fourth aspect, in the third aspect, the wall step rises up with a curvature radius from the bottom of the connecting member, when the connecting member is viewed from the second opening so that the first opening is located on the right.

According to the fourth aspect, the exhaust gas, which has passed through the first catalyst, reaches the wall step and is diffused into the space inside the connecting member along the surface of the wall step curving with the curvature radius. Accordingly, the flow rate of exhaust gas to the second catalyst can be decreased. The exhaust gas, which has been diffused into the connecting member, flows into the second catalyst, thereby providing a uniform flow of exhaust gas inside the second catalyst. This can also decrease a rise in the flow resistance of the exhaust gas in the second catalyst. Accordingly, the exhaust device exhibits improved efficiency in use, function, performance of the whole catalysts including the part of the second catalyst close to and facing the part of the first catalyst, and mountability of control devices.

According to a fifth aspect, in the fourth aspect, the wall transition rises up with a curvature radius from the bottom of the connecting member, when the connecting member is viewed from the second opening so that the first opening is located on the right. The wall transition has a greater curvature radius than the wall step.

According to the fifth aspect, the exhaust gas, which has passed through the first catalyst, reaches the wall transition and is diffused into the connecting member along the gently curving wall transition. The wall transition curves more gently than the wall step. This can further decrease the flow rate of exhaust gas near the upstream end surface of the second catalyst to provide a uniform flow of exhaust gas from the inside of the connecting member into the second catalyst. This can also effectively decrease a rise in the flow resistance to allow the exhaust device to exhibit more improved efficiency in use, function, and performance of the second catalyst, and mountability of control devices.

According to a sixth aspect, in any one of the third to fifth aspects, the connecting member includes: a first connecting member provided with the first opening and a part of the second opening closer to the first opening; and a second connecting member provided with the other part of the second opening. The first wall and the second wall are provided in the second connecting member.

According to the sixth aspect, the connecting member is divided into the first and second connecting members to be molded. This can achieve accurate molding of the connecting member in a complicated shape. In addition, the first and second walls, which guide the flow of exhaust gas, are formed in the second connecting member. This configuration can provide a smooth wall surface without forming any division on the walls, thereby reducing the turbulence of the exhaust gas. A part of the second opening closer to the first opening is connected from the first opening through a wall surface of the bend bending with a small curvature radius. Thus, the stress tends to concentrate on the surface of the bend. The division between the first and second connecting members is formed away from such a position, in which the stress tends to concentrate. This can improve the durability of the connecting member.

Advantages of the Invention

As described above, the engine exhaust device according to the present disclosure achieves a compact size, and exhibits improved efficiency in use, function, and performance of a catalyst, and mountability of control devices.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present disclosure will now be described in detail with reference to the drawings. The following description of a preferred embodiment is merely an example in nature, and is not intended to limit the scope, applications or use of the present disclosure.

First Embodiment

An engine E, to which an exhaust gas purifier1(an engine exhaust device) according to a first embodiment is applied, is an inline-four gasoline engine mounted in a vehicle. The engine E is horizontally placed in the front of an FF vehicle.

Note that the engine, to which the exhaust gas purifier1according to the first embodiment is applied, is not limited to the four-cylinder gasoline engine. The purifier is also applicable to any other engine such as a multi-cylinder engine or a diesel engine. The engine is applicable not only to the FF vehicle, but also to any other vehicle, such as an FR vehicle, an MR vehicle, an RR vehicle, a 4WD vehicle, or a motorcycle, which employs various layouts.

As shown inFIG. 1, the engine E includes a cylinder block E1and a cylinder head E2. Although not shown in detail, first to fourth cylinders, which are defined by the cylinder block E1and the cylinder head E2, are arranged in this order in series, perpendicular to the drawing plane ofFIG. 1. For each cylinder, a cylinder bore of the cylinder block E1, a piston, and the cylinder head E2define a combustion chamber.

The cylinder head E2is provided with four exhaust ports (not shown), each of which is connected to a corresponding one of the four combustion chambers. Exhaust gas generated in the combustion chambers is discharged outside the vehicle through an exhaust path including the exhaust ports.

As shown inFIGS. 1 and 2, the exhaust gas purifier1according to this embodiment is connected to the exhaust ports. A downstream exhaust gas passage (not shown), which extends to the outside of the vehicle, is connected downstream of the exhaust gas purifier1. In this manner, the exhaust path, to which the exhaust gas purifier1is applied, includes the exhaust ports, the exhaust gas purifier1, and the downstream exhaust gas passage described above.

As shown inFIGS. 1 and 2, the exhaust gas purifier1according to the present embodiment includes an exhaust manifold M, a connector N, and a catalytic converter Q. The exhaust manifold M is connected to the four exhaust ports of the engine E. The connector N is connected to the outlet of the exhaust manifold M. The catalytic converter Q is connected to the outlet of the connector N.

As shown inFIGS. 1 and 2, the exhaust manifold M is connected to the four exhaust ports.

As shown inFIG. 2, the exhaust manifold M is for collecting the exhaust gas discharged from the four combustion chambers through the respective exhaust ports. Independent exhaust pipes, each of which is connected to a corresponding one of the four exhaust ports, are assembled in the right of the exhaust manifold M. The exhaust gas collected in the exhaust manifold M is fed into the catalytic converter Q via the connector N connected to the outlet of the exhaust manifold M.

The connector N is a tubular member for guiding the exhaust gas, which has been fed from the exhaust manifold M disposed above the catalytic converter Q, to the catalytic converter Q. In this embodiment, the connector N is an L-shaped tubular member curving from above to the left.

In the description of the present specification, the cylinder head E2is located above and the cylinder block E1is located below in the “vertical direction,” and the engine E is located at the front and the exhaust manifold M is located at the rear in the “longitudinal direction,” as shown inFIG. 1, with reference to the engine E. On the other hand, as shown inFIG. 2, in a “horizontal direction,” the cylinders are arranged with reference to the engine E. In other words, the “horizontal direction” is perpendicular to the drawing plane ofFIG. 1. The front is the left and the back is the right. Further, the expressions “upstream” and “downstream” are used with reference to the flow of exhaust gas discharged from the combustion chambers through the respective exhaust ports.

In this embodiment, as shown inFIG. 1, the “longitudinal direction” is parallel to the central axis L3of a gasoline particulate filter3(hereinafter referred to as a “GPF3”), which serves as a second catalyst and will be described later.

As shown inFIGS. 2 to 4, the catalytic converter Q includes a three-way catalyst2as a first catalyst, the GPF3as the second catalyst, a connecting pipe4as a connection member, a downstream end part7of the GPF, an exhaust gas outlet5, and an outlet6for the EGR. The three-way catalyst2is connected to the outlet of the connector N. The GPF3is disposed downstream of the three-way catalyst2. The connecting pipe4connects the three-way catalyst2to the GPF3. The downstream end part7is provided at the downstream end of the GPF3. The exhaust gas outlet5and the outlet6for the EGR are provided at the tip of the downstream end part7of the GPF.

The three-way catalyst2is for purifying hydrocarbon HC, carbon monoxide CO, and nitrogen oxide NOx in the exhaust gas. Although not described in detail, examples of the three-way catalyst2include a catalyst obtained by coating a honeycomb carrier with a catalyst component, which is formed by supporting noble metal such as Pt, Pd, and Rh on a support material of metal oxide. The three-way catalyst2is not particularly limited, and may be of any known type.

As shown inFIGS. 5 and 9, the three-way catalyst2is a cylindrical catalyst with a central axis L2. Although not particularly limited, the three-way catalyst2has a cylindrical shape in one preferred embodiment in view of easily disposing in the three way catalyst2in the exhaust path and obtaining a uniform flow of exhaust gas. The cross-sectional shape of the three-way catalyst2, which is perpendicular to the central axis L2of the three-way catalyst, is not particularly limited. Any shape such as a completely round, oval, rectangular, or polygonal shape may be employed. However, the three-way catalyst2may have a completely round or oval cross-sectional shape in one preferred embodiment, in view of obtaining a uniform flow of exhaust gas and reducing manufacturing costs.

As shown inFIG. 7, the surface of the three-way catalyst2located at the upstream end is referred to an upstream end surface2A of the three-way catalyst (i.e., the upstream end surface of the first catalyst). The surface of the three-way catalyst2located at the downstream end is referred to a downstream end surface2B of the three-way catalyst (i.e., the downstream end surface of the first catalyst). The upstream and downstream end surfaces2A and2B of the three-way catalyst are in a circular shape with the same diameter.

As shown inFIGS. 5, 7, and 8, the three-way catalyst2has, as a catalyst body for purifying exhaust gas, a two-stage structure. A front stage21is located closer to the upstream end of the three-way catalyst, while a rear stage22is located closer to the downstream end of the three-way catalyst. The front stage21serves as a three-way catalyst with an excellent low-temperature activity for purifying low-temperature exhaust gas, for example, during a low-load operation of the engine E. On the other hand, the rear stage22serves as a three-way catalyst with an excellent high-temperature activity for purifying high-temperature exhaust gas, for example, during a high-load operation. In this embodiment, the three-way catalyst2has the two-stage structure of the front and rear stages21and22, but is not limited thereto. The three-way catalyst2may be a single catalyst, or may have a multi-stage structure that is divided into three or more stages.

As shown inFIG. 7, assume that the entire length of the three-way catalyst2in the longitudinal direction, that is, parallel to the central axis L2of the three-way catalyst is H2. Then, the ratio H21/H22of the length H21of the front stage21to the length H22of the rear stage22is about 1. The length ratio H21/H22of the front stage21to the rear stage22is variable in accordance with, for example, the type of the engine E. However, the ratio falls within a range from 0.50 to 2.0 in one preferred embodiment, and from 0.75 to 1.25 in one more preferred embodiment, in view of obtaining an excellent catalytic performance of the three-way catalyst2.

As shown inFIG. 7, the tip of the three-way catalyst2including the upstream end surface2A, that is, the tip of the front stage21protrudes beyond the connecting pipe4.

Serving as the catalyst suitable for purifying low-temperature exhaust gas, the front stage21is more likely to be influenced by a thermal damage when exposed to high-temperature exhaust gas. Protruding outside from the inside of the connecting pipe4, the front stage21is not exposed to the high-temperature exhaust gas, which has been diffused into the connecting pipe4, even in a high-load operation. This effectively prevents or reduces deterioration of the front stage21due to the heat damage, thereby reducing the risk of the heat damage to the whole three-way catalyst2.

The whole or only a part of the front stage21may protrude beyond the connecting pipe4. In addition, the degree of protrusion is adjustable in accordance with the length H21of the front stage21. The degree of protrusion of the front stage21falls within a range from 50% to 100% in one preferred embodiment, from 60% to 95% in one more preferred embodiment, and from 70% to 90% in one particularly preferred embodiment, of the length H21of the front stage, in view of preventing or reducing the thermal damage of the catalyst with an excellent low-temperature activity.

With the use of a three-way catalyst having an excellent high-temperature activity, the rear stage22may also or, does not have to, protrude beyond the connecting pipe4. Considering that the rear stage22exhibits excellent performance of purifying high-temperature exhaust gas, the whole rear stage22is inserted into the connecting pipe4in one preferred embodiment, in view of downsizing the exhaust gas purifier1.

As shown inFIG. 5, the three-way catalyst2includes a catalyst mat23and a catalyst case24. The catalyst mat23covers the entire outer peripheries of the front and rear stages21and22as a main body of the catalyst. The catalyst case24covers the entire outer periphery of the catalyst mat23.

The exhaust gas has a low temperature around 400° C. at a low load, and a high temperature around 800° C. at a high load. Then, being always exposed to the high-temperature exhaust gas, which has passed through the three-way catalyst2, the three-way catalyst2may be degraded by a thermal damage.

The catalyst mat23is for holding the front and rear stages21and22as the main body of the catalyst even under an environment in which the three-way catalyst2is exposed to high-temperature exhaust gas, and made of a material, such as ceramic, with a high heat resistance and a high heat retention. The thickness depends on, for example, the size of the three-way catalyst2or the material of the catalyst mat23, and is not particularly limited. However, the thickness may fall, for example, within a range from 2.0 mm to 8.0 mm, from 3.0 mm to 5.0 mm in one preferred embodiment, and from 3.6 mm to 4.0 mm in one more preferred embodiment, in view of preventing or reducing a thermal damage of the three-way catalyst2. With a thickness smaller than 2.0 mm, the three-way catalyst2tends to have difficulty in exhibiting sufficient holding performance, heat resistance, and heat retention. A thickness larger than 8.0 mm may cause higher manufacturing costs or difficulty in keeping a sufficient space for mounting control devices.

The catalyst case24is for holding the front and rear stages21and22of the three-way catalyst2and the catalyst mat23, and made of, for example, metal such as iron or stainless steel. Note that the catalyst mat23and the catalyst case24may be of any known type.

The GPF3is a filter disposed downstream of the three-way catalyst2to trap particulate matter (hereinafter referred to as “PM”) in the exhaust gas, which has passed through the three-way catalyst2. Although not described in detail, the GPF3is, for example, a sealed honeycomb carrier, which additionally has a filter function and is coated with a catalyst to promote combustion of the PM deposited on the filter. The PM in the exhaust gas is adsorbed onto the surface of a partition wall of the GPF3. Once the PM is deposited, a post injection for injecting fuel is performed after the main injection to increase the temperature to the temperature for the PM combustion, thereby incinerating the PM deposited on the GPF3. The GPF3is not particularly limited and may be of any known type.

As shown inFIGS. 1 and 2, the GPF3is a cylindrical catalyst with a central axis L3. Although the shape of the GPF3is not particularly limited, the GPF3may have a cylindrical shape in one preferred embodiment, in view of easily disposing the GPF3in the exhaust path and obtaining a uniform flow of exhaust gas. The cross-sectional shape of the GPF3, which is perpendicular to the central axis L3of the GPF, is not particularly limited. Any shape such as a completely round, oval, rectangular, or polygonal shape may be employed. However, the GPF3may have a completely round or oval cross-sectional shape in one preferred embodiment, in view of obtaining a uniform flow of exhaust gas and reducing manufacturing costs.

As shown inFIG. 9, the surface of the GPF3located at the upstream end is referred to an upstream end surface3A of the GPF (i.e., the upstream end surface of the second catalyst). The surface of the GPF3located at the downstream end is referred to a downstream end surface3B of the GPF (i.e., the downstream end surface of the second catalyst). The upstream and downstream end surfaces3A and3B of the GPF are in a circular shape with the same diameter.

Like the three-way catalyst2, the GPF3includes a catalyst main body, a catalyst mat, and a catalyst case. The catalyst main body of the GPF is for purifying the exhaust gas. The catalyst mat of the GPF covers the entire outer periphery of the catalyst main body of the GPF. The catalyst case of the GPF covers the entire outer periphery of the catalyst mat of the GPF. The catalyst mat and the catalyst case of the GPF are used for the same or a similar purpose as the catalyst mat23and the catalyst case24described above, and may have the same or similar configurations as those described above.

The connecting pipe4is a tubular member for connecting the three-way catalyst2to the GPF3, and forms a part of the exhaust path.

As shown inFIG. 10, the connecting pipe4includes a first opening4A at the upstream end, a second opening4B at the downstream end, and a bend4C connecting the first opening4A to the second opening4B.

As shown inFIG. 10, the three-way catalyst2is inserted in the downstream end surface2B first into the connecting pipe4through the first opening4A. On the other hand, for example, as shown inFIG. 5, the GPF3is inserted in the upstream end surface3A first into the connecting pipe4through the second opening4B. The configuration, in which the three-way catalyst2and the GPF3are inserted into the connecting member4, requires, for example, no connecting flange, which is needed if the three-way catalyst2and the GPF3are connected to the upstream and downstream ends of the connecting member4. This contributes to downsizing of the exhaust gas purifier1.

—Relative Arrangement Between Three-Way Catalyst and GPF—

FIG. 9is a cross-sectional view taken along line IX-IX ofFIG. 4. The cross-section, which is perpendicular to the central axis L2of the three-way catalyst2and passes through the GPF3and the exhaust gas outlet5, is viewed from the left. The cross-section shown inFIG. 9is hereinafter referred to as an “IX-IX section” (longitudinal section). The line indicated by reference numeral PL32inFIG. 9represents a plane that includes the central axis L3of the GPF3and is parallel to the central axis L2of the three-way catalyst2.

As shown inFIG. 9, the central axis L2of the three-way catalyst2is located below the plane PL32, that is, the central axis L3of the GPF3on the IX-IX section. Accordingly, as will be described later, the exhaust manifold M can be disposed above the three-way catalyst2so that the exhaust gas purifier1can be disposed in a small area in the vehicle.

As shown inFIG. 5, the downstream end surface2B of the three-way catalyst2and the upstream end surface3A of the GPF3are arranged in the bend4C to form a dihedral angle α of about 90 degrees. The dihedral angle α is not limited to this angle. However, the angle falls within a range from 60 degrees to 120 degrees in one preferred embodiment, from 70 degrees to 110 degrees in one more preferred embodiment, and from 80 degrees to 100 degrees in one particularly preferred embodiment, in view of maintaining a sufficient flow of exhaust gas from the three-way catalyst2to the GPF3.

In addition, a part of the upstream end surface3A of the GPF3is covered with a side surface of the three-way catalyst2to form an overlap31. In other words, the overlap31is a part of the upstream end surface3A of the GPF3, which is close to and faces a part of the side surface of the three-way catalyst2.

FIG. 5is a cross-sectional view taken along line V-V inFIG. 3. The cross-section, which includes the central axis L2of the three-way catalyst2and is parallel to the central axis L3of the GPF3, is viewed from above. The cross section shown inFIG. 5is hereinafter referred to as a “V-V section” (cross-section). As shown inFIG. 5, the length H31of the part of the side surface of the three-way catalyst2forming the overlap31is longer than or equal to 10% and shorter than 50% of the entire length H2of the three-way catalyst2on the V-V section in one preferred embodiment, in view of arranging the three-way catalyst2and the GPF3in a small area and providing a uniform flow of exhaust gas within the GPF3.

The length H31of the side surface of the three-way catalyst2is 10% or longer and shorter than 50% of the width W3of the GPF in the V-V section ofFIG. 5in one preferred embodiment, in view of arranging the three-way catalyst2and the GPF3in a small area and providing a uniform flow of exhaust gas within the GPF3.

As described above, if the three-way catalyst2and the GPF3are arranged laterally, the first catalyst and the GPF3form the overlap31, which merely expands within the range described above. This allows the exhaust gas purifier1to achieve a compact size and to exhibit improved efficiency in using the GPF3, particularly in using the overlap31.

—First and Second Connecting Members—

As shown inFIGS. 10 and 12, the connecting pipe4includes a first connecting member40and a second connecting member41.

As shown inFIG. 12, the first and second connecting members40and41include a first joint40A and a second joint41A, respectively, in the connecting pipe4near the downstream end surface2B of the three-way catalyst2. The first and second joints40A and41A are fitted to each other to form the connecting pipe4.

As shown inFIG. 10, the first connecting member40is provided with the first opening4A and a part, namely, the right half, of the second opening4B. On the other hand, the second connecting member41is provided with the other part, namely, the rest left half of the second opening4B.

In other words, the connecting pipe4is comprised of the two members: the first connecting member40; and the second connecting member41. The first opening4A, the part of the second opening4B, and a part of the bend4C are provided in the first connecting member40. Then, the rest of the second opening4B and the rest of the bend4C are provided in the second connecting member41.

The connecting member4is divided into the first and second connecting members40and41to be molded, which allows for accurate molding of the connecting member4in the complicated shape. A part of the second opening4B close to the first opening4A is connected from the first opening4A through a wall surface of the bend4C bending with a small curvature radius. Thus, the stress tends to concentrate on the wall surface of the bend. The division between the first and second connecting members40and41is formed away from such a position, in which the stress tends to concentrate. This improves the durability of the connecting pipe4.

In the specification, as shown inFIG. 10, the uppermost part and the lowermost part of the connecting pipe4are referred to as a top4D and a bottom4E, respectively, where the exhaust gas purifier1including the connecting pipe4is mounted to the engine E. Note that, in the present embodiment, the top4D and the bottom4E are located near the joint between the first and second connecting members40and41.

As shown inFIGS. 10 and 12, the first connecting member40includes a support45for supporting by face the outer peripheral surface of the three-way catalyst2.

As shown inFIGS. 5, 9, 10, 11, and 12, the support45includes a support part45A at the first opening and a support part (support surface)45B at the downstream end surface of the three-way catalyst. The support part45A supports by face the entire peripheral surface of the three-way catalyst2from the first opening4A toward the downstream end surface2B of the three-way catalyst2. The support part45B extends from the support part45A at the first opening, and supports the outer peripheral surface of the three-way catalyst2, which is located opposite to the GPF3with respect to the three-way catalyst2. InFIG. 12, for the purpose of explanation, the boundary between the support part45A at the first opening and the support part45B at the downstream end surface of the three-way catalyst is represented by a dashed line.

As shown inFIG. 9, the support45B at the downstream end surface of the three-way catalyst supports by face the outer peripheral surface of the three-way catalyst2in a range in which an angle θ around the central axis L2of the three-way catalyst2is about 190 degrees, when the three-way catalyst2is viewed from the left, that is, from the downstream end surface2B of the three-way catalyst. The angle θ is not limited to this angle. However, the angle θ is 180 degrees or greater in one preferred embodiment, in view of downsizing the exhaust gas purifier1, improving the performance of the connecting pipe4in holding the three-way catalyst2, and reducing the thermal damage of the three-way catalyst2.

The outer peripheral surface of the three-way catalyst2is supported by face with the support part45B which is formed in this manner in the connecting pipe4and has a sufficient area. This improves the supportability of the three-way catalyst2, and further reduces the longitudinal size of the catalytic converter Q.

The support part45B at the downstream end surface of the three-way catalyst supports the three-way catalyst2. This does not allow the exhaust gas, which has passed through the three-way catalyst2, to come into contact with the outer peripheral surface, which is supported with the support part45B at the downstream end surface of the three-way catalyst. This reduces the volume of the part of the three-way catalyst2exposed to the exhaust gas, which has passed through the three-way catalyst2itself. Accordingly, the reduction of the volume can decrease the thermal damage caused by constant exposure of the three-way catalyst2to high-temperature exhaust gas. In particular, the entire outer periphery of the three-way catalyst2is covered with the catalyst mat23and the catalyst case24as described above. This reduces thermal expansion of the catalyst case24, which is caused by the thermal damage, and eventually, reduces a decrease in the surface pressure of the catalyst mat23. Such a configuration can also prevent or reduce erosion of the catalyst mat23due to a thermal damage, and displacement of the main body of the three-way catalyst2from the catalyst mat23and the catalyst case24when the main body is held.

As shown inFIG. 1, the outer peripheral surface supported with the support part45B at the downstream end surface of the three-way catalyst is adjacent to the cylinder block E1of the engine E. In this configuration, the exhaust gas, which has passed through the three-way catalyst2, does not flow into the cylinder block E1. This reduces heat damage to the outside of the catalytic converter Q.

—First and Second Walls—

As shown inFIGS. 5, 6, 10, and 12, the second connecting member41includes a first wall42and a second wall43for guiding the exhaust gas, which has passed through the three-way catalyst2, to the GPF3. As shown inFIG. 5, the first wall42faces the downstream end surface2B of the three-way catalyst2. The second wall43faces the upstream end surface3A of the GPF3.

When the connecting pipe4is divided into the first and second connecting members40and41to be molded, the first and second walls42and43are formed in the second connecting member41, that is, one of the connecting members. This provides smooth wall surfaces of the walls guiding the exhaust gas, without forming any division. This can reduce turbulence of the flow of the exhaust gas.

As shown inFIGS. 10 and 12, the first wall42includes a wall transition42A, a wall slope42B, and a wall step42C. The wall transition42A smoothly extends forward from the downstream end, which forms the second opening4B. The wall slope42B is smoothly connected to the wall transition42A, and rises up toward the three-way catalyst2. The rear of the wall step42C is smoothly connected to the wall slope42B. The front of the wall step42C is smoothly connected to the second wall43with a curvature radius R3(a predetermined curvature radius), as shown inFIG. 5.

As shown inFIG. 10, when the connecting pipe4is viewed from the second opening4B so that the first opening4A is located on the right, the wall transition42A rises up with a curvature radius R1from the bottom4E of the connecting pipe4. Similarly, the wall step42C rises up with a curvature radius R2from the bottom4E of the connecting pipe4. Note that, as shown inFIG. 10, the curvature radius R1of the wall transition and the curvature radius R2of the wall step are collectively referred to as the curvature radius R of the first wall.

The curvature radius R of the first wall shown inFIG. 10is here set to be greater than the curvature radius R3of the second wall shown inFIG. 5.

It is known that a fluid such as exhaust gas tends to flow along a curved surface with a great curvature radius. For example, as shown inFIG. 15, the following case is considered. The bend4C of the connecting pipe4employs a general curved tubular shape. Specifically, the curvature radius R3of the second wall curves larger and more gently than the curvature radius R of the first wall. In this case, as indicated by the broken arrow inFIG. 15, it is considered that most of the exhaust gas, which has passed through the three-way catalyst2, directly flows into the GPF3along the wall surface, which gently curves with the curvature radius R3of the second wall. Then, the amount of exhaust gas flowing into the vicinity of the overlap31of the GPF3decreases, which may reduce the efficiency in using the GPF3. In addition, in the position where a larger amount of exhaust gas flows, the flow rate of the exhaust gas increases so that the flow resistance may increase to decrease the output.

On the other hand, in the exhaust gas purifier1according to the present embodiment, the first and second walls42and43of the bend4C of the connecting pipe4are formed as follows. As shown inFIGS. 5 and 6, the second wall has a small curvature radius R3. As shown inFIGS. 10 and 11, the curvature radius R of the first wall is greater than the curvature radius R3of the second wall. As shown inFIG. 9, the central axis L2of the three-way catalyst3is shifted downward from the plane PL32, which includes the central axis L3of the GPF3and is parallel to the central axis L2of the three-way catalyst2.

Then, as shown inFIG. 6, there is a change in the flow of exhaust gas. That is, the exhaust gas, which has passed through the three-way catalyst2, is more likely to flow along the surface of the first wall42than along the wall surface of the connector between the first wall42and the second wall43. Specifically, as indicated by the broken arrow inFIG. 6, the flow of exhaust gas similar to the flow shown inFIG. 15decreases. On the other hand, as indicated by the solid-line arrow inFIG. 6, observed is an increase in the flow of exhaust gas reaching the first wall42, and flowing along the wall surface of the wall transition42A curving with the curvature radius R1or of the wall step42C curving with the curvature radius R2. As described above, as shown inFIG. 9, the central axis L2of the three-way catalyst is shifted downward from the plane PL32, which is parallel to the central axis L2. Thus, observed is an increase in the flow of exhaust gas flowing along the curved wall surface of the wall transition42A or the wall step42C and winding upward from below. In this manner, the secondary flow of exhaust gas, which reaches the first wall42and winds up into the space between the three-way catalyst2and the GPF3, is utilized. Then, the flow rate of the whole exhaust gas decreases so that the exhaust gas is diffused into the connecting pipe4. This increases the amount of exhaust gas flowing into the overlap31of the GPF3. This also decreases the flow resistance of the exhaust gas flowing into the GPF3, thereby providing a uniform flow of exhaust gas. Eventually, the exhaust device exhibits improved efficiency in using the GPF3, the function, and the performance.

The wall step42C of the first wall42, which is continuous with the second wall43, protrudes more toward the three-way catalyst2than toward the wall transition42A. As shown inFIG. 6, this reduces the concentrated flow of exhaust gas, which has passed through the three-way catalyst2and reaches the wall step42C, toward the end of the GPF3, at which the wall transition42A exists. This also promotes the flow of exhaust gas to the overlap31.

As shown inFIG. 10, the curvature radius R1of the wall transition is set to be greater than the curvature radius R2of the wall step.

It is considered, as indicated by the solid arrow inFIGS. 7, 8, and 11, that the exhaust gas, which has passed through the three-way catalyst2, reaches the first wall42, particularly, the wall transition42A or the wall step42C, and winds up or winds down along the curved wall surface of the wall transition42A or the wall step42C to be diffused into the bend4C of the connecting pipe4. At this time, as shown inFIGS. 7 and 8, the curvature radius R1of the wall transition is greater than the curvature radius R2of the wall step, that is, the wall transition42A curves more gently than the wall step42C. This further reduces the flow rate of exhaust gas near the upstream end surface3A of the GPF3. Accordingly, the flow resistance of the exhaust gas flowing into the GPF3from the connecting pipe4further decreases, and a uniform flow of exhaust gas is provided. Eventually, the efficiency in use, the function, and the performance of the GPF3further improve.

As shown inFIG. 8, a base44is provided on the top4D of the connecting pipe4and on the second connecting member41. Control devices such as various sensors including an NOx sensor (detecting means)92shown inFIG. 4are mounted on the base44. InFIG. 8, for simplicity, the sensor body of the NOx sensor92is not shown, and only a mount92A for NOx sensor for mounting the sensor body is shown.

As described above, the exhaust gas, which has passed through the three-way catalyst2, is diffused into the connecting pipe4and then flows into the GPF3. At this time, there is little chance the exhaust gas, which has passed through the three-way catalyst2, directly reaching the top4D of the connecting pipe4. At the top4D, the secondary flow of exhaust gas, which winds up along the wall surface of the first wall42, diffuses the exhaust gas. Then, near the top4D of the connecting pipe4, a sufficient amount of exhaust gas to be used for detecting, for example, the component concentration, temperature, and pressure of the exhaust gas is diffused at a lower flow rate. This arrangement of various sensors near the top4D of the connecting pipe4achieves stable detection accuracy, and improves the mountability of control devices such as various sensors.

Although the base44is flat as shown inFIG. 8, note that the shape is not limited thereto. The base44may have, for example, a curved surface. Further, the control devices such as various sensors may be provided in a position other than the base44.

<Downstream End Part of GPF>

As shown inFIG. 3, a downstream end part7of the GPF is connected to the downstream end of the GPF3. As shown inFIG. 13, the downstream end part7of the GPF is provided with an introduction hole71for the exhaust gas outlet, and an introduction port72for the EGR. The introduction hole71allows for attachment of the exhaust gas outlet5that is the outlet of the exhaust gas, which has passed through the GPF3. The introduction port72allows for attachment of the outlet6for the EGR that feeds part of the exhaust gas to the intake side.

The exhaust gas outlet5is for guiding the exhaust gas, which has passed through the GPF3, to the downstream exhaust gas passage (not shown). The exhaust gas outlet5is also for collecting and removing the moisture generated by the purification of the exhaust gas using the three-way catalyst2and the GPF3.

The line indicated by reference numeral PRL31shown inFIG. 5is a projection line of the central axis L3of the GPF on the V-V cross-section. On the other hand, the line indicated by reference numeral L5represents the central axis of the exhaust gas outlet5. The point indicated by reference numeral P5is located on the central axis L5of the exhaust gas outlet. The point P5represents the intersection between the central axis L5and a plane including the introduction hole71for the exhaust gas outlet, which is shown inFIG. 13and will be described later. That is, the point P5represents the center of the introduction hole71for the exhaust gas outlet, and is hereinafter referred to as the center position P5of the exhaust gas outlet5.

As shown inFIG. 5, the center position P5of the exhaust gas outlet5, which is close to the downstream end surface3B of the GPF3, is offset to the right, that is toward the three-way catalyst2, from the projection line PRL31of the central axis L3of the GPF3on the V-V cross-section.

As shown inFIGS. 6 and 13, this configuration causes a flow of the exhaust gas, which has flowed into the GPF3, toward the exhaust gas outlet5. Then, with the flow of the exhaust gas toward the exhaust gas outlet5, the amount of the exhaust gas flowing into the overlap31increases. This improves the efficiency in using the GPF3.

As shown inFIG. 5, the degree of the offset of the exhaust gas outlet5is set as follows in one preferred embodiment, in view of obtaining a sufficient amount of exhaust gas flowing into the overlap31to improve the efficiency in using the GPF3. On the V-V cross-section, the right side surface5A of the exhaust gas outlet5, which is closer to the three-way catalyst2, is located on the right of the side surface3C of the GPF3, which is closer to the three-way catalyst2, that is, located closer to the three-way catalyst2. At this time, the degree of the offset of the exhaust gas outlet5is set as follows in one preferred embodiment, in view of reducing an increase in the flow resistance around the exhaust gas outlet5. On the V-V cross-section, the left side surface5B of the exhaust gas outlet5is located on the left of the side surface3C of the GPF3, which is closer to the three-way catalyst2.

As shown inFIG. 9, the exhaust gas outlet5is placed below the plane PL32. This placement of the exhaust gas outlet5below the GPF3allows for effective collection and removal of the moisture generated at the purification of the exhaust gas using the three-way catalyst2and the GPF3at the exhaust gas outlet5.

The engine E may employ, as a component, an EGR that recirculates part of exhaust gas to an intake side, for the purpose of preventing or reducing knocking and reducing the amount of nitrogen oxide NOx. In this case, the exhaust gas outlet6for the EGR may be provided near the downstream end surface3B of the GPF3.

As shown inFIG. 5, the outlet6for the EGR is placed opposite to the exhaust gas outlet5with respect to the projection line PRL31of the central axis L3of the GPF3on the V-V cross section. As shown inFIG. 13, the downstream end part7of the GPF is provided with an exhaust gas guiding passage72A for the EGR in a position apart from the introduction hole71for the exhaust gas outlet. The exhaust gas guiding passage72A allows for guiding of the exhaust gas to the introduction port72for the EGR.

This configuration can maintain a sufficient amount of exhaust gas for the EGR and diffuse the flow of exhaust gas within the GPF3into the exhaust gas outlet5and the outlet6for the EGR to provide a uniform flow of exhaust gas. Accordingly, the efficiency in use, function, and performance of the GPF3can further improve.

The exhaust gas purifier1according to the present embodiment may be assembled into, for example, the structure of a vehicle layout Z as shown inFIG. 14.

Specifically, as shown inFIG. 9, the three-way catalyst2is provided slightly lower than the GPF3. Accordingly, as shown inFIG. 14, placing the exhaust manifold M above and close to the three-way catalyst2further downsizes the exhaust gas purifier1particularly in the longitudinal direction.

As shown inFIGS. 1 and 3, the bottom4E of the connecting pipe4and the bottom3D of the GPF3are formed linearly. As a result, as shown inFIG. 14, a power divider (vehicle component) K is placed below and close to the connecting pipe4and the GPF3. This placement achieves a more compact vehicle layout in the longitudinal, lateral, and vertical directions.

Note that the vehicle component placed below the connecting pipe4and the GPF3is not limited to the power divider K, and may be any other vehicle component. Specifically, for example, if a drive shaft of a drive system or the exhaust gas purifier1is applied to, for example, an FR vehicle; for example, an engine mount of a mount system may be placed close to the connecting pipe4and the GPF3.

Other Embodiments

Now, other embodiments according to the present disclosure will be described in detail. In the description of these embodiments, the same reference characters as those in the first embodiment are used to represent equivalent elements, and the detailed explanation thereof will be omitted.

Although being applied to the FF vehicle, the exhaust gas purifier1of the first embodiment is also applicable to an FR vehicle with the following configuration in such a manner; that is, the independent exhaust pipes of the exhaust manifold M, which are connected to the four exhaust ports, are extended rearward and collected to be oriented at the rear end of the engine E toward the center of the vehicle width, and are then further extended rearward.

In the first embodiment, the three-way catalyst2serves as the first catalyst, and the GPF3serves as the second catalyst. However, the catalysts are not limited thereto, and various catalysts may be used. Specifically, for example, if the exhaust gas purifier1is applied to a diesel engine, a diesel particulate filter may be employed. To serve as the first catalyst and the second catalyst, an oxidation catalyst and a catalyst for NOx purification may be combined.

In the first embodiment, as shown inFIG. 9, the three-way catalyst2is provided slightly lower than the GPF3. As shown inFIG. 10, the wall transition42A and the wall step42C of the first wall42rise up with the curvature radius R1and the curvature radius R2, respectively, from the bottom4E of the connecting pipe4. In this respect, the three-way catalyst2may be provided at a level higher than or equal to that of the GPF3. The wall transition42A and the wall step42C of the first wall42may fall down with the curvature radius R1and the curvature radius R2, respectively, from the top4D of the connecting pipe4. Alternatively, the wall transition42A and the wall step42C may curve from both the top4D and the bottom4E of the connecting pipe4. Instead of the curved shape, a gentle slope such as the base44may be provided. In this case, the secondary flow of exhaust gas may be formed along the slope. In any case, the position for mounting the detecting means, such as the base44for mounting the sensors, is not limited to the position closer to the top4D of the connecting pipe4. The detecting means may be provided as appropriate in a position, such as at the bottom4E or the first connecting member40, in which a uniform flow of exhaust gas is obtained.

In the first embodiment, the outlet of the exhaust manifold M is located on the right of the cylinder arrangement. As shown inFIG. 10, the connecting pipe4is configured so that the first opening4A is located on the right, as viewed from the rear. In this respect, the first opening4A may be arranged in any other position or direction such as the left or the vertical direction, depending on the vehicle layout.

In the first embodiment, the three-way catalyst2and the GPF3are inserted into the connecting pipe4. However, these catalysts do not have to be inserted into the connecting pipe4, and may be connected to the upstream and downstream ends of the connecting pipe4, for example, via connecting flanges. Alternatively, one of the three-way catalyst2and the GPF3may be inserted into the connecting pipe4, and the other may be connected to an end of the connecting pipe4, for example, via a connecting flange. Note that the configuration of the first embodiment may be employed in one preferred embodiment in view of downsizing the exhaust gas purifier1.

INDUSTRIAL APPLICABILITY

The present disclosure achieves a reduction in the size of an engine exhaust device, while improving the efficiency in use, function, and performance of a catalyst, and mountability of control devices. Hence, the present disclosure is thus significantly useful.

DESCRIPTION OF REFERENCE CHARACTERS

1Exhaust Gas Purifier (Engine Exhaust Device)2Three-Way Catalyst (First Catalyst)2A Upstream End Surface of Three-Way Catalyst (Upstream End Surface of First Catalyst)2B Downstream End Surface of Three-Way Catalyst (Downstream End Surface of First Catalyst)3Gasoline Particulate Filter, GPF (Second Catalyst)3A Upstream End Surface of GPF (Upstream End Surface of Second Catalyst)3B Downstream End Surface of GPF (Downstream End Surface of Second Catalyst)3C Side Surface of GPF (Side Surface of Second Catalyst closer to First Catalyst)3D Bottom of GPF (Bottom of Second Catalyst)4Connecting Pipe (Connecting Member)4A First Opening4B Second Opening4C Bend4D Top4E Bottom5Exhaust Gas Outlet5A Right Side Surface of Exhaust Gas Outlet5B Left Side Surface of Exhaust Gas Outlet6Outlet for EGR7Downstream End Part of GPF21Front Stage22Rear Stage23Catalyst Mat24Catalyst Case31Overlap40First Connecting Member40A First Joint41Second Connecting Member42First Wall42A Wall Transition42B Wall Slope42C Wall Step43Second Wall44Base45Support45A Support Part at First Opening45B Support Part (Support Surface) at Downstream End Surface of Three-Way Catalyst71Introduction Hole for Exhaust Gas Outlet72Introduction Port for EGR72A Exhaust Gas Guiding Passage for EGR92NOx Sensor (Detecting Means)92A Mount for NOx SensorEngineK Power Divider (Vehicle Component)L2Central Axis of Three-Way Catalyst (Central Axis of First Catalyst)L3Central Axis of GPF (Central Axis of Second Catalyst)L5Central Axis of Exhaust Gas OutletM Exhaust ManifoldN ConnectorP5Center PositionPRL31Projection LinePL32PlaneQ Catalytic ConverterR Curvature Radius of First WallR1Curvature Radius of Wall TransitionR2Curvature Radius of Wall StepR3Curvature Radius of Second Wall (Predetermined Curvature Radius)α Dihedral Angleθ Angle