Title of Invention

"AN EXHAUST PIPE HAVING AN EXHAUST EMISSION CONTROL SYSTEM"

Abstract

[Solving Means] An exhaust pipe 30 contains an exhaust emission control system 40 including a catalyst supporting plate 41 and a catalyst supporting cylinder member 51 which are disposed in series in this order. The catalyst supporting plate 41 is composed of a multihole plate 43 with small holes 42. The multihole plate 43 has a slot 44 at a central portion in the width direction. [Effect] The slot or slit, which is provided at an approximately central portion of a catalyst supporting plate, allows the catalyst supporting plate to be freely thermally expanded/contracted, thereby significantly prolonging the service life. Since the slot or slit serves as a guide passage for an exhaust gas, it is possible to make smooth the flow of the exhaust gas and hence to reduce the disturbance of the flow of the gas. This is effective to keep a preferable output characteristic of the engine.

Full Text

The present invention relates to an exhaust pipe having an exhaust emission control system. [Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an exhaust pipe- an exhaust emission control system, which is suitable for a motorcycle. [Related Art] A technique of mounting an exhaust emission control system on a vehicle for preventing air pollution has been known, for example, from Japanese Patent Laid-open No. Hei 4-109022 titled "Exhaust Emission Control System". As shown in Fig. 1 of the above document, this system includes a catalyst supporting plate 16 vertically disposed in an exhaust pipe portion 15 for oxidizing an unburned component of an exhaust gas. [Problem to be Solved by the Invention] The catalyst supporting plate 16 disposed in the exhaust pipe portion 15 directly under an engine, however, has a disadvantage. The plate 16 is exposed to a high temperature atmosphere, because it is positioned at a central portion in cross-section of the exhaust pipe portion 15 which is particularly higher in temperature in the exhaust pipe and it is additionally heated by oxidization of the catalyst. As a result, the plate 16 is susceptible to a large stress due to thermal expansion and thereby it is shortened in service life. The catalyst supporting plate 16 has another disadvantage. Although an exhaust gas is desirable to smoothly flow down from the engine through the exhaust pipe portion 15, the catalyst supporting plate 16 disturbs the flow of the exhaust gas. The disturbance of the flow of the exhaust gas exerts a large effect on an output characteristic of the engine. An object of the present invention is: (1) to prolong the service life of a catalyst supporting plate; (2) to reduce the disturbance of the flow of an exhaust gas; and (3) to desirably keep purifying reaction with an exhaust gas. [Means for Solving the Problem] To achieve the above object, according to an invention described in claim 1, there is provided an exhaust pipe including an exhaust emission control system characterized in that an exhaust pipe portion formed of a pair of half cylinders, disposed directly under an engine; and a catalyst supporting plate disposed at an approximately central portion in transverse cross-section of said exhaust pipe portion with both ends of said catalyst supporting plate held by flanges of said pair of half cylinders of said exhaust pipe portion; wherein said catalyst supporting plate has at an approximately central portion thereof a slot or slit extending in the flow direction of exhaust gas, and a slot substantially perpendicular to said slot or slit. The provision of the slot substantially perpendicular to the slot or slit provided at an approximately central portion of the catalyst supporting plate is effective to sufficiently relieve thermal expansion/contraction of the plate, and hence to suppress occurrence of thermal stress. According to an invention described in claim 2, in addition to the configuration of the invention described in claim 1 , end portions of said slot substantially perpendicular to said slot or slit formed in said catalyst supporting plate at an approximately central portion thereof extend up to positions overlapped to said flanges of said pair of half cylinders. Since vibration (that is, chatter) of the catalyst supporting plate is not transmitted to each end portion of the slot, it is possible to prevent the catalyst supporting plate from being cracked from the end portion of the slot. According to an invention described in claim 3, in addition to the configuration of the invention described in any one of claims 1 and 2, said catalyst supporting plate has a plurality of bridges crossing said slit extending along an approximately central portion of said plate. Since the catalyst supporting plate is unified by provision of a plurality of the bridges crossing the slit, it is possible to make easy handling and assembling of the catalyst supporting plate. According to an invention described in claim 4, in addition to the configuration of the invention described in claim 3, said bridges are disposed at two portions, a central portion and a rear end portion, of said catalyst supporting plate. Since the bridges are disposed at two portions, a central portion and a rear end portion, of said catalyst supporting plate, it is possible to reduce the resistance of the bridges against the flow of exhaust gas passing through the slit as much as possible. According to an invention described in claim 5, in addition to the configuration of the invention described in any one claims 1 to 4, said catalyst supporting plate, and a catalyst supporting cylinder member disposed at an approximately central portion in transverse cross-section of said exhaust pipe in such a manner as to extend along the flow direction of exhaust pipe, are disposed in series in this order. Two-stage purifying actions can be achieved by provision of the catalyst supporting plate and the catalyst supporting cylinder member. This is effective to ensure a sufficient purifying reaction. According to an invention described in claim 6, in addition to the configuration of the invention described in claim 3, wherein each of said bridge has a notch which allows said bridge to be broken by thermal expansion. Since the bridges are broken by thermal expansion of the catalyst supporting plate by the effect of the notches provided in the bridges, the catalyst supporting plate is divided into two parts along the central portion during use. This allows the catalyst supporting plate to be freely, thermally expanded / contracted. Accordingly, the present invention relates to an exhaust pipe having an exhaust emission control system, comprising: an exhaust pipe portion formed of a pair of half cylinders, disposed directly under an engine; and a catalyst supporting plate disposed at an central portion in transverse cross-section of said exhaust pipe portion with both ends of said catalyst supporting plate held by flanges of said pair of half cylinders of said exhaust pipe portion; wherein said catalyst supporting plate has at an central portion thereof a slot or slit extending in the flow direction of exhaust gas, and a slot perpendicular to said slot or slit. [Brief Description of the Accompanying Drawings] [Fig- 1] A side view of a motorcycle including an exhaust pipe (first embodiment) according to the present invention. [Fig. 2] A plan view of the motorcycle including an exhaust pipe (first embodiment) according to the present invention. [Fig. 3] A plan view of a front locking portion of a fuel tank of the motorcycle according to the present invention. [Fig. 4] A sectional view taken on line 4-4 of Fig. 3. [Fig. 5] A plan view of a swing arm of the motorcycle according to the present invention. [Fig. 6] A side view of Fig. 5. [Fig. 7] A side view of the exhaust pipe including an exhaust emission control system according to the present invention. [Fig. 8] A sectional view taken on line 8-8 of Fig. 7. [Fig. 9] A sectional view taken on line 9-9 of Fig. 7. [Fig. 10] An exploded perspective view of a rear portion of an exhaust emission control system (first embodiment) according to the present invention; [Fig. 11] A vertical sectional view of an exhaust emission control system (first embodiment) according to the present invention. [Fig. 12] A view seen along arrows 12-12 of Fig. 11. [Fig. 13] A sectional view taken on line 13-13 of Fig. 11. [Fig. 14] A view showing an exhaust pipe (second embodiment) according to the present invention. [Fig. 15] A view showing a modification of the embodiment shown in Fig. 10. [Fig. 16] A view showing another modification of the embodiment shown in Fig. 10. [Fig. 17] A view showing an exhaust pipe (third embodiment) according to the present invention. [Fig. 18] A sectional view showing an exhaust pipe (third embodiment) according to the present invention. [Fig. 19] A sectional view taken on line 19-19 of Fig. 18. [Figs. 20(a), 20(b)] Views illustrating a first function of the exhaust pipe (third embodiment) according to the present invention. [Figs. 21(a), 21(b)] Views illustrating a second function of the exhaust pipe (third embodiment) according to the present invention. [Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It is to be noted that the drawing should be seen from the direction of characters. Fig. 1 is a side view of a motorcycle including an exhaust pipe (first embodiment) of the present invention. The configuration of a motorcycle 1 is as follows. A front fork 4 is rotatably supported on the front portion of a main frame 2 through a head pipe 3. A front wheel 5 and a front fender 6 are mounted on the front fork 4. A two-cycle engine 8 is mounted on the lower side of the main frame 2 through engine hangers 7,7. An exhaust pipe 30 extends from the two-cycle engine 8. A cantilever swing arm 11 is rotatably supported on the rear end portion of the main frame 2 through a pivot 9, and a rear wheel 12 is mounted on the swing arm 11 . In the figure, reference numeral 14 indicates a fuel tank; 15 is an air clearer; 16 is a carburetor; 17 is a seat; 18, 19 are seal rails; 20 is a fellow rider seat, 21 is a rear suspension; 22 is a drive chain; and 23 is a silencer. Reference numeral 61 indicates a meter; 62 is a head lamp; 63 is a winker provided in each of right and left openings of a front portion of a cowling 67; 64 is a brake disk; 66 is a caliper; 68 is a radiator; 69 is a drive pulley for driving an exhaust timing control valve provided at the upper edge of an exhaust port of the engine 8; 71 is a drive motor for driving the exhaust timing control valve; 72 is a suction chamber, 73 is a battery; 74 is an oil tank; 76 is a tail lamp; 77 is a seat cowl; and 78 is a rear axle. Fig. 2 is a plan view of the motorcycle including the exhaust pipe (first embodiment) of the present invention. The exhaust pipe 30 extends rearward from the center of a vehicular body, bypassing the rear suspension 21 and the cantilever swing arm 11, and extends rearward on the right side of the body as seen from the rider. In the figure, reference numeral 25 indicates a rider step; 26 is a brake pedal; 27 is a change pedal; and 28 is a steering handlebar. Fig. 3 is a plan view showing a locking portion for locking a front portion of a fuel tank of the motorcycle to which the present invention is applied. The fuel tank 14 is indicated by an imaginary line for a clearer understanding. The locking portion for locking the front portion of the fuel tank includes a cross pipe 81 hung between the main pipes 2, 2 extending rearward from the head pipe 3 in a V-shape; rubber stoppers 82, 82, each being L-shaped in the plan view, fixed on the cross pipe 81; rubber members 83, 83 mounted on the cross pipe 81; and a stay 14a on the fuel tank side, which is fitted with the rubber members 83, 83. Fig. 4 is a sectional view taken on line 4-4 of Fig. 3. A procedure of assembling the locking portion for locking the front portion of the fuel tank will be described with reference to Fig. 4. The rubber member 83 has a structure similar to that of a C-shaped stop ring specified in JISB2804. The rubber member 83 can be mounted on the cross pipe 81 as shown in Fig. 4 by extending a slit 83a, and it can be brought in tight-contact with the outer peripheral surface of the cross pipe 81 by an elastic force thereof. The rubber member 83 has also shallow cutouts 83b formed in the outer peripheral surface, so that it can be easily deformed for simplifying the above mounting work. The rubber member 83 thus mounted is pulled in the direction of crossing the paper surface of the drawing for locking different cutouts 83c, 83c with the rubber stopper 82 (see Fig. 3), to thereby obtain the rotation-stop of the rubber member 83. A horizontally U-shaped recess 14b, which is formed in the stay 14a provided on the front portion of the fuel tank, is mounted to cover the rubber member 83. The stay 14a can be thus fixed while holding the rubber members 83, 83 as shown in Fig. 3. A thrust force is applied to the rubber member 83 when the stay 14a is moved in the axial direction of the cross pipe 81; however, the movement of the rubber member 83 and the stay 14a in the thrust direction can be desirably limited because the rubber stoppers 82, 82 limit the movement of the rubber members 83, 83. Fig. 5 is a plan view of a swing arm of the motorcycle to which the present invention is applied. The swing arm 11 has a pivot collar 87 provided on the front portion through bearings 85, 86; a chain slider 88 provided on the intermediate portion; and a rear axle 78 provided on the rear portion through a bearing holder 89, a needle bearing 91 and a ball bearing 92. In addition, reference numeral 93 indicates an oil seal for dust seal; and 94 is a collar for separating the needle bearing 91 from the ball bearing 92 at a specified interval. A flange 95 for mounting a rear wheel is formed at one end of the rear axle 78, and a brake disk 96 is mounted on the flange 95 by means of a bolt 97. On the other hand, a star-flange 98 is mounted on the other end of the rear axle 78 by spline or key connection, and a rubber bush 99 is inserted in each large diameter portion of the star-flange 98. A boss plate 101 is mounted on the rubber bushes 99 thus inserted, and a sprocket 102 is mounted on the boss plate 101. In Fig. 5, reference numeral 106 indicates a brake caliper bracket; and 107 is a stopper pin for torque link. Fig. 6 is a side view of Fig. 5. When the sprocket 102 is forcibly turned by a drive chain (not shown), the star-flange 98 is turned after the rubber bush 99 is elastically deformed, to thereby absorb a shock due to starting and transmission, enabling smoother running. The bearing holder 89 can be freely turned by loosening a bolt 103 provided at the rear end of the rear axle 78. Since the outer peripheral surface of the bearing holder 89 is eccentric with respect to the axis thereof, the tension of the drive chain can be adjusted by the eccentricity of the outer peripheral surface of the bearing holder 89. In addition, reference numeral 105 indicates a chain slider fixing screw; and 88 is a horizontally u-shaped chain slider for collectively covering the upper/ lower surfaces and the front end surface of the front portion of the swing arm 11. Fig. 7 is a side view of the exhaust pipe (first embodiment) including the exhaust emission control system of the present invention. The exhaust pipe 30 shown in Fig. 1 includes the curved exhaust pipe portion 31, an expansion chamber 32, and a tail pipe portion 36. The expansion chamber 32 includes a divergent portion 33 having the cross-section of a flow passage gradually increased in the direction of a gas flow, a straight portion 34 having the cross-section of the flow passage being substantially constant, and a convergent portion 35 having the cross-section of a flow passage gradually decreased in the direction of the gas flow. It is to be noted that the exhaust pipe portion does not mean the entire exhaust pipe but only the curved portion of the exhaust pipe which is positioned directly under an engine. The exhaust pipe 30 contains an exhaust emission control system 40. The exhaust emission control system 40 includes a catalyst supporting plate 41 disposed in the exhaust pipe portion 31 and a catalyst supporting cylinder member 51 disposed in the expansion chamber 32. The catalyst supporting plate 41 is formed of a multihole plate 43 having a plurality of small holes 42 wherein a slot 44 extending along a gas flow is provided in the plate 43 at the center in the width direction. The catalyst supporting cylinder member 51 extends from the divergent portion 33 to the straight portion 34 in such a manner as to be positioned at an approximately center portion in cross-section (see Fig. 9). The detail configuration of the cylinder member 51 will be -described later. In addition, reference numeral 37 indicates a metal hanger. Fig. 8 is a sectional view taken on line 8-8 of Fig. 7. The catalyst supporting plate 41 is clamped between half -cylinders 31R, 31L forming the exhaust pipe portion 31 and is welded at both the ends (upper and lower ends) therewith. The slot 44 positioned at the center of the exhaust pipe 31 in cross-section serves as a passage for an exhaust gas and it also allows the vertical extension of the plate 41. The catalyst is selected from noble metals or ceramics capable of performing catalytic oxidation of an unburned component contained in an exhaust gas. Fig. 9 is a sectional view taken on line 9-9 of Fig. 7 showing the configuration of a front supporting stay. A front supporting stay 52F includes a W-shaped metal support 53F and an outer ring 54 welded to the metal support 53F. The outer ring 54 is divided into two parts for making easy the assembly. An elastic body 55, an inner ring 56 and the catalyst supporting cylinder member 51 supported by the outer ring 54 will be described later. The exhaust pipe 30 is composed of a divided pipe body 30T and a divided pipe body 3 OB connected to each other. The W-shaped metal support 53F is welded only to the divided pipe body 30T as shown in Fig. 9. As is apparent from Fig. 9, the catalyst supporting cylinder member 51 is supported in the exhaust pipe 30 at an approximately center position in cross-section by the front supporting stay 52F. A rear supporting stay 52R is similar in the basic structure to the front supporting stay 52F except for a slight difference in the shape of the W-shaped metal support 53R, and accordingly, the explanation thereof is omitted . Fig. 10 is an exploded perspective view showing the rear portion of the exhaust emission control system (first embodiment) of the present invention. The catalyst supporting cylinder member 51 is composed of a multihole plate 5 la which is rounded and welded at a mating portion 51c of both the ends. In addition, a cutout 51b is formed in the rear end of the multihole plate 51a, and when the multihole plate 51a is welded at the mating portion 51c, the cutout 51b is located at the bottom, that is, at the position opposed to the mating portion 51c. The cylinder member 51 supports a catalyst such as a noble metal or ceramic . The inner ring 56 having a flange 56a is mounted to the rear portion of the catalyst supporting cylinder member 51 so as to cover it, and is welded thereto. The inner ring 56 may be divided into two parts The heat-resisting elastic body 55 is fitted around the inner ring 56, and is held by the two divided parts of the outer ring 54 . Each of the two divided parts of the outer ring 54 has a thrust stop flange 54a, and the divided part shown on the left side in the figure has a rotation-stop piece 54b. The rotation-stop piece 54b is fitted in the cutout 51b formed on the rear end of the catalyst supporting cylinder member 51 for preventing the rotation of the cylinder member 51. The elastic body 55 is preferably made of stainless wool excellent in heat resistance and cushioning performance Fig. 11 is a vertical sectional view of the exhaust emission control system (first embodiment) of the present invention. The catalyst supporting cylinder member 51 is formed with small holes 51d except for portions overlapped to the inner rings 56, 56. The reason why the small holes 51d are not formed in the overlapped portions is that an exhaust gas does not pass through such portions. The elastic body 55 in the front supporting stay 52F is held between the flanges 54a of the outer ring 54 and the flange 56a of the inner ring 56. Similarly, the elastic body 55 in the rear supporting stay 52R is held between the flanges 54a of the outer ring 54 and the flange 56a of the inner ring 56. The flanges 54a of the outer ring 54 of the front supporting stay 52F limit the forward movement (leftward in the figure) of the elastic body 55, and the flanges 54a of the outer ring 54 of the rear supporting stay 52R limit the rearward movement (rightward in the figure) of the elastic body 55. Fig. 12 is a view seen from line 12-12 of Fig. 11 showing an essential portion of .the rear supporting stay 52R. The rotation-stop piece 54b of the outer ring 54 is fitted in the cutout 51b of the catalyst supporting plate 51 for preventing the rotation of the catalyst supporting cylinder member 51. In addition, the cylinder member 51 is welded at the mating portion 51c just as the front supporting stay 52F. Fig. 13 is a sectional view taken on line 13-13 of Fig. 11 showing a state that the catalyst supporting member 51 is supported by the outer ring 54 of the front supporting stay 52F through the elastic body 55 and the inner ring 56. The function of the exhaust pipe (first embodiment) including the exhaust emission control system of the present invention will be described below. Referring to Fig. 1, an exhaust gas heated at a high temperature flows from the engine 8 to the silencer 23 on the rear side through the exhaust pipe 30. At this time, the exhaust gas discharged from the engine 8 first reaches the catalyst supporting plate 41 disposed in the exhaust pipe portion 31, as shown in Fig. 7. The first stage purifying reaction is carried out in the catalyst supporting plate 41, and the second stage purifying reaction is carried out in the subsequent catalyst supporting cylinder member 51. With respect to the flow of the exhaust gas, the exhaust gas at a high temperature smoothly flows in the exhaust pipe portion 31 along the slot 44 by the guide action Of the slot 44. The flow of the exhaust gas is not disturbed even in the subsequent catalyst supporting cylinder member 51 because the cylinder member 51 extends along the flow direction of the exhaust gas . As for the thermal expansion of the catalyst supporting plate 41, the plate 41 linearly passes through the center of the pipe and it has the slot 44 at the center of the pipe as shown in Fig. 8, and accordingly, the plate 41 is prevented from being applied with an undesirable thermal stress. On the other hand, as shown in Fig. 11, the intermediate portion and the rear end portion of the catalyst supporting cylinder member 51 are certainly supported by the front supporting stay 52F and the rear supporting stay 52R, respectively. The leading end of the catalyst supporting cylinder member 51 heated at a high temperature is freely expanded/contracted in the forward direction in the cantilever state. A portion of the catalyst supporting cylinder member 51 between the front supporting stay 52F and the rear supporting stay 52F is also freely expanded/contracted by the action of the elastic bodies 55, 55. The movement of the catalyst supporting cylinder member 51 in the longitudinal direction (axial direction) is suitably limited by the opposed flanges 54a, 54a of the outer rings 54, 54 for preventing the cylinder member 51 from being slipped off from the front supporting stay 52F and the rear supporting stay 52R. The rotation of the catalyst supporting cylinder member 51 is further prevented by the rotation-stop piece 54b. Since the mating portion 51c at which both the ends of the multihole plate 5 la are welded to each other is usually located at the specific position, the design condition in strength of the mating portion 51c is desirably determined. Fig. 14 shows an exhaust pipe (second embodiment) of the present invention. In the figure, parts corresponding to those shown in the Fig. 7 are indicated by the same characters, and the detail explanation thereof is omitted . A catalyst supporting plate 41 is divided into two parts by a slit 45. The slit 45 serves as an exhaust gas passage like the slot 44 (see Fig. 7) for guiding an exhaust gas at a high temperature. Fig. 15 shows a modification of the embodiment shown in Fig. 10 (exploded perspective view of the rear portion of the exhaust emission control system of the present invention). A catalyst supporting cylinder member 51 in this modification is the same as that shown in Fig. 10, and the explanation thereof is omitted. Each of outer rings 54, 54 in this modification is also similar to that shown in Fig. 10 except that it is smaller in size than that shown in Fig. 10, and the detail explanation thereof is omitted. In this modification, a slit 57a is formed in an elastic body 57 for enhancing a deformation performance in the radial direction. Also, chamfered portions 57b are formed at both ends of the inner surface of the elastic body 57, and a stopper ring 58 is used. The chamfered portions 57 serve as guide surfaces allowing the elastic body 57 to be mounted without catching on the cylinder member 51. The stopper ring 58 having a flange 58a is smaller in diameter and shorter in length than the inner ring 56 shown in Fig. 10. The reason why the diameter and length of the stopper ring 58 is made smaller will be described in the following modification. Fig. 16 shows a modification of the embodiment shown in Fig. 11 (vertical sectional view of the exhaust emission control device of the present invention). Parts corresponding to those shown in Fig. 11 are indicated by the same characters, and the explanation thereof is omitted . The inner peripheral surface of an elastic body 57 is brought in press-contact with a cylinder member 51, and the outer peripheral surface of the elastic body 57 is held by the outer rings 54, 54. The axial movement of the elastic member 57 is prevented by flange 54a of the outer ring 54 and a flange 58a of a stopper ring 58 (which is the same as that shown in Fig. 15). Since the elastic body 57 in this modification is directly brought in press-contact with the cylinder member 51, it can be made smaller in diameter than that shown in Fig. 11. As a result, the stopper ring 58 is made smaller in size and also the outer rings 54, 54 is made smaller in outside diameter. The flow resistance of an exhaust gas flowing around a heat-resisting material 57 and the outer rings 54, 54 is made small in this modification because the outside diameters of the heat-resisting material 57 and the outer rings 54, 54 are made smaller. This is effective to desirably keep the output performance of the engine. Fig. 17 is a view showing an exhaust pipe (third embodiment) of the present invention. Parts corresponding to those shown in Fig. 14 are indicated by the same characters, and explanation thereof is omitted. An exhaust emission control system 100 includes a catalyst supporting plate 101 disposed in an exhaust pipe portion 31 and a catalyst supporting cylinder member 51 disposed in an expansion chamber 32. The catalyst supporting plate 101 includes an upper plate 102 and a lower plate 103 disposed on upper and lower sides of a slit 45 respectively, two bridges 104, 104 connecting the upper and lower plates 102, 103 to each other, and a plurality of slots 106 substantially perpendicular to the slit 45. Fig. 18 is a sectional view showing the exhaust pipe (third embodiment) of the present invention. The catalyst supporting plate 101 is disposed in the exhaust pipe portion 31 at an approximately central portion thereof in transverse cross-section. An upper end portion 102a of the upper plate 102 is held on upper flanges 108L, 108R of half cylinders 31L, 31R. A lower end portion 103a of the lower plate 103 is held on lower flanges 108L, 108R of half cylinders 31L, 31R. The bridges 104, 104 are provided at a central portion and a rear end portion of the slit 45. Each of the bridges 104, 104 extends across the slit 45 for connecting the upper and lower plates 102, 103 to each other. The bridge 104 has such a notch 105 as to allow the bridge 104 to be broken by thermal expansion/contraction of the catalyst supporting plate 101. Three pieces of the slots 106 are formed in each of the upper and lower plates 102, 103. The slot 106 is branched from the slit 45. End portions 106a, 106a of the slot 106 extend outward until they are overlapped to the upper and lower flanges 108R, 108R, 108L, 108L. Fig. 19 is a sectional view taken on line 19-19 of Fig. 18, showing a state in which the end portion 106a of the slot 106 extends until it is overlapped to the upper flanges 108L, 108R of the half cylinders 31L, 31R. At this time, the flanges 108L, 108R hold a portion of the upper plate 102 around the end portion 106a of the slot 106. Reference numeral 110 indicates a welded portion at which the flanges 108L, 108R are welded to the upper end portion 102a of the upper plate 102. The end portion 106a of the slot 106 formed in the lower plate 103 shown in Fig. 18 is the same in structure as that formed in the upper plate 102 shown in Fig. 19, and the explanation thereof is omitted. A procedure of assembling the catalyst supporting plate (third embodiment) will be described below. The catalyst supporting plate 101 shown in Fig. 18 is located as a single unit at an assembling position and held by the half cylinders 31L, 31R of the exhaust pipe portion 31, to be thus assembled into the state shown in Fig. 17. The catalyst supporting plate 101 is unified by the bridges 104, 104 before assembling, so that it can be easily positioned upon handling and assembling thereof. Figs. 20 (a), 20 (b) are views illustrating the first function of the exhaust pipe (third embodiment) of the present invention. Referring to Fig. 20(a), when the catalyst supporting plate 101 is thermally expanded, for example, in the direction shown by an arrow (1), the bridges 104, 104 are broken at portions having the notches 105, 105 by stress generated by thermal expansion. Referring to Fig. 20 (b), after the bridges 104, 104 are broken, the broken bridges 104, 104 interfere with each other by the thermal expansion/contraction repeated several times, so that gaps 104a, 104a become larger. As a result, the thermal expansion/contraction of the catalyst supporting plate 101 in the direction shown by the arrow (1) can be relieved by the gaps 104a, 104a. The thermal expansion/contraction of the catalyst supporting plate 101 in the direction shown by an arrow (2) can be relieved by the plurality of the slots 106. As a result, it becomes possible to improve the durability of the catalyst supporting plate 101. Since the bridges 104, 104 are disposed at the central portion and the rear end portion of the catalyst supporting plate 101, it is possible to reduce the disturbance of the flow of an exhaust gas passing through the slit while reducing the resistance of bridges against the flow of the gas as much as possible. Figs. 21 (a), 21 (b) are views illustrating the second function of the exhaust pipe (third embodiment) of the present invention, wherein Fig. 21 (a) shows a comparative example, and Fig. 21 (b) shows the embodiment of the present invention. Fig. 21 (a) shows a state in which the end portion 106a of the slot 106 of the catalyst supporting plate 101 does not reach a holding area 112 of the flanges. In this example, a crack 113 possibly occurs at the end portion 106a of the slot 106 by vibration (for example, chatter) of the catalyst supporting plate 101. Fig. 21(b) shows a state in which the end portion 106a of the slot 106 of the catalyst supporting plate 101 is overlapped to the holding area of the flanges and a portion of the catalyst supporting plate 101 around the end portion 106a of the slot 106 is held by the flanges. Since vibration of the catalyst supporting plate 101 is not transmitted to the end portion 106a of the slot 106, it is possible to prevent the catalyst supporting plate 101 from being cracked from the end portion 106a. Although the embodiments have been described by example of an exhaust pipe of a motorcycle, the present invention may be applied to exhaust pipes of other internal combustion engines. [Effect of the Invention] The present invention having the above configuration exhibits the following effects. According to the invention described in claim 2, since the slot is provided in such a manner as to be substantially perpendicular to the slot or slit provided at an approximately central portion of the catalyst supporting plate, it is possible to sufficiently relieve thermal expansion/contraction of the plate and hence to suppress occurrence of thermal stress. This increases flexibility against thermal expansion of the catalyst supporting plate, resulting in the prolonged service life. According to the invention described in claim 3, since vibration (that is, chatter) of the catalyst supporting plate is not transmitted to each end portion of the slot, it is possible to prevent the catalyst supporting plate from being cracked from the end portion of the slot. According to the invention described in claim 4, since the catalyst supporting plate is unified by provision of a plurality of the bridges crossing the slit, it is possible to make easy handling and assembling of the catalyst supporting plate. According to the invention described in claim 5 , since the bridges are disposed at two portions, a central portion and a rear end portion, of said catalyst supporting plate, it is possible to reduce the resistance of the bridges against the flow of exhaust gas passing through the slit as much as possible. According to the invention described in claim 6, since two-stage purifying actions can be achieved by provision of the catalyst supporting plate and the catalyst supporting cylinder member, it is possible to ensure a sufficient purifying reaction. As a result, it is possible to prolong the service life of the catalyst supporting plate, to keep a preferable output characteristic of the engine, and to ensure a sufficient purifying reaction. According to the invention described in claim 7, since the bridges are broken by thermal expansion of the catalyst supporting plate by the effect of the notches provided in the bridges, the catalyst supporting plate is divided into two parts along the central portion during use and accordingly it can be freely thermally expanded/ contracted. Further, it is possible to make smooth the flow of the exhaust gas passing through the slit and hence to reduce the disturbance of the flow of the exhaust gas. [Reference Numerals] 1: motorcycle, 8: engine, 30: exhaust pipe, 30T, 30B: divided pipe, 31: exhaust pipe portion, 31L, 31R: half circular pipe, 32: expansion chamber, 33: divergent portion, 34: straight portion, 35: convergent portion, 40: exhaust emission control system, 41, 100: catalyst supporting plate, 44, 106: slot, 45: slit, 51, 101: catalyst supporting cylinder member, 52F: front supporting stay, 52R: rear supporting stay, 53F, 53R: W-shaped metal support, 54: outer ring, 54a: flange, 54b: rotation-stop piece, 55, 57: elastic body, 56: inner ring, 56a: flange, 58: stopper ring, 104: bridge, 105: notch, 106a: end portion, 108L, 108R: flange portion WE CLAIM; 1. An exhaust pipe having an exhaust emission control system, comprising: an exhaust pipe portion formed of a pair of half cylinders, disposed directly under an engine; and a catalyst supporting plate disposed at a central portion in transverse cross-section of said exhaust pipe portion with both ends of said catalyst supporting plate held by flanges of said pair of half cylinders of said exhaust pipe portion; wherein said catalyst supporting plate has at a central portion thereof a slot or slit extending in the flow direction of exhaust gas, and a slot perpendicular to said slot or slit. 2. An exhaust pipe having an exhaust emission control system as claimed in claim 1, wherein end portions of said slot perpendicular to said slot or slit formed in said catalyst supporting plate at a central portion thereof extend up to positions overlapped to said flanges of said pair of half cylinders. 3. An exhaust pipe having an exhaust emission control system as claimed in any one of claims 1 and 2, wherein said catalyst supporting plate has a plurality of bridges crossing said slit extending along an central portion of said plate. 4. An exhaust pipe having an exhaust emission control system as claimed in claim 3, wherein said bridges are disposed at two portions, a central portion and a rear end portion, of said catalyst supporting plate. 5. An exhaust pipe having an exhaust emission control system as claimed in any one claims 1 to 4, wherein said catalyst supporting plate, and a catalyst supporting cylinder member disposed at an approximately central portion in transverse cross-section of said exhaust pipe to extend along the flow direction of exhaust pipe, are disposed in series in this order. 6. An exhaust pipe having an exhaust emission control system as claimed in claim 3, wherein each of said bridge has a notch which allows said bridge to be broken by thermal expansion. 7. An exhaust pipe having an exhaust emission control system substantially hereinbefore described with reference to and as illustrated in the accompanying drawings.

Documents:

1769-del-1997-abstract.pdf

1769-del-1997-claims.pdf

1769-del-1997-correspondence-others.pdf

1769-del-1997-correspondence-po.pdf

1769-del-1997-description (complete).pdf

1769-del-1997-drawings.pdf

1769-del-1997-form-1.pdf

1769-del-1997-form-13.pdf

1769-del-1997-form-19.pdf

1769-del-1997-form-2.pdf

1769-del-1997-form-3.pdf

1769-del-1997-form-4.pdf

1769-del-1997-form-6.pdf

1769-del-1997-gpa.pdf

1769-del-1997-petition-138.pdf

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