Title of Invention

"EXHAUST DEVICE WITH CATALYST".

Abstract

An exhaust device with catalyst including an exhaust tube (1) extended from an engine, a muffler (2) connected to the exhaust tube (1), an inserting portion (10, 11) of the exhaust tube (1) which is arranged in the muffler (2) and one end (38) of which is connected to communicate with said exhaust tube (1) and a conventional catalyst carried at inside of the muffler: said inserting portion (10, 11) of the exhaust tube (1) constituting a diffuser pipe (11) a diameter of which is widened in a diverging shape in a direction of flowing out exhaust gas; and a catalyst cylinder (13) which is in a cylindrical shape and a surface of which is porous and carries the catalyst inserted into and supported by the diffuser pipe (11) concentrically.

Full Text

[DETAILED DESCRIPTION OF THE INVENTION] [0001] [Technical Field of the Invention] The present invention relates to an exhaust device carrying a catalyst in a muffler. [0002] [Prior Art] Japanese Unexamined Patent Publication No. JP-A-6-10658 discloses an exhaust device in which a muffler is connected to an exhaust tube extended from an engine, a diffuser pipe one end of which is connected to communicate with the exhaust tube and the diameter of which is widened in a diverging shape in a direction of flowing out exhaust gas, is arranged in the muffler, and a catalyst device is insertingly mounted to a connection point connecting the exhaust tube and the diffuser pipe. [0003 ] Japanese Unexamined Utility Model Publication No. JU-A-4-27108 discloses an exhaust device in which a cylindrical member incorporating a catalyst is connected in series with a rear end of a diffuser pipe arranged in a muffler. [0004] Japanese Unexamined Patent Publication No. JP-A-54-118912 discloses an exhaust device in which a cylindrical member formed by a cloth-like catalyst is connected in series with an upstream side of an exhaust tube inserted into a muffler. [0005] Further, Japanese Unexamined Utility Model Publication No. JU-A-2-87922 discloses an exhaust device in which a rear end portion of a dif fuser pipe connected to a rear end portion of an exhaust tube extended out from an engine, is projected into a muffler, the inside of the muffler is partitioned into three chambers communicated to each other by communicating tubes, and a catalyst is carried on respective inner peripheral faces of the exhaust tube, the diffuser pipe and an external plate of the muffler and on a total of surfaces of the communicating tubes, a tail pipe and partition walls. [0006] [Problems to be Solved by the Invention] When the separate catalyst device is arranged in series with the diffuser pipe as in Japanese Unexamined Patent Publication No. JP-A-6 - 10658, Japanese Unexamined Utility Model Publication No. JU-A-4- 27108, and Japanese Unexamined Patent Publication No . JP-A-54 -118912, the total dimension of the members inserted into the muffler is prolonged and accordingly, the muffler is liable to prolong, and further, such a catalyst device is normally constituted in a honeycomb shape and therefore, the weight is increased and accordingly, compact formation of the total of the exhaust device becomes difficult. [0007] Moreover, in the case of a muffler for a small-sized vehicle such as a scooter or the like, the length of the muffler is liable to be restricted and therefore, it is not easy to arrange a catalyst device such that the surface area necessary for achieving a predetermined purification level can be secured and a difficult design is required. [0008] Further, although the purification efficiency is promoted by arranging a catalyst device in series with an exhaust system of an exhaust tube or a diffuser pipe, an influence on pulsation of exhaust is liable to cause and accordingly, a difficult design is required such that the output of an engine is not lowered thereby. [0009 ] Furthermore, when the catalyst device is constituted in a honeycomb shape, the weight is increased and accordingly, a portion for attaching the diffuser pipe becomes large-sized, particularly, it is difficult to support the catalyst device by a cantilever and an influence on pulsation of exhaust gas is liable to cause and therefore, a difficult design is required such that the output of an engine is not lowered. [0010] Further, although the porous catalyst cylinder is used in Japanese Unexamined Patent Publication No. JP-A-54 -118912, in this example, the exhaust gas after expansion is purified by collecting it to inside of the catalyst cylinder and therefore, the purification efficiency is deteriorated and as a result, the catalyst cylinder becomes large-sized and the cost is increased. [0011] Meanwhile, when a separate catalyst device is not provided and the catalyst is carried directly on the inner peripheral faces of the exhaust tube and the diffuser pipe and the like as in Japanese Unexamined Utility Model Publication No. JU-A-2-87922, the exhaust can be purified without effecting an influence on the length of the muffler and pulsation of exhaust gas. However, according to the. example, the exhaust gas which comes out from the diffuser pipe is brought into contact with the catalyst carried by the communicating tubes and the like on the downstream side while gradually lowering the exhaust temperature and accordingly, the purification efficiency tends to lower as the exhaust gas proceeds toward the downstream side and as a result, the catalyst must be carried in a wide range to achieve a predetermined purification level and accordingly, the cost is increased by that amoun t. In order to resolve the above-described problem, according to the present invention there is provided an exhaust device with catalyst including an exhaust tube extended from an engine, a muffler connected to the exhaust tube, an inserting portion of the exhaust tube which is arranged in the muffler and one end of which is connected to communicate with said exhaust tube and a catalyst carried at inside of the muffler: said inserting portion of the exhaust tube constituting a diffuser pipe a diameter of which is widened in a diverging shape in a direction of flowing out exhaust gas; and a catalyst cylinder which is constituted by forming a porous material in a cylindrical shape and a surface of which carries the catalyst is inserted into and supported by the diffuser pipe substantially concentrically. In this case, an end portion of the catalyst cylinder on the side of flowing out the exhaust gas can be projected in the direction of flowing out the exhaust gas longer than an end portion of the diffuser pipe on the side of flowing out the exhaust gas . Further, the catalyst cylinder can be supported by the inner side of the diffuser pipe by a supporting member and a flow path of the exhaust gas can be formed between the catalyst cylinder and the diffuser pipe. Moreover, the catalyst can be carried on at least portions of both of inner and outer peripheral. faces of the diffuser pipe. [0017] Furthermore, in an exhaust device with catalyst including an exhaust tube extended from an engine, a muffler connected to the exhaust tube, an inserting portion of the exhaust tube which is arranged in the muffler and one end of which is communicated with the exhaust tube, and a catalyst carried at inside of the muffler in which exhaust gas flowing out from the inserting portion of the exhaust tube is exhausted to outside of the muffler after being expanded to a surrounding of the inserting portion of the exhaust tube in an expansion chamber provided at an inner portion of the muffler and the exhaust gas is purified by the catalyst, wherein the catalyst can be carried on at least portions of both of inner and outer peripheral faces of the inserting portion of the exhaust tube. [0018] In this case, a range of carrying the catalyst on both of the inner and outer peripheral faces of the inserting portion of the exhaust gas, can include a portion proximate to an end portion of the inserting portion of the exhaust tube on the side of flowing in the exhaust gas and a portion proximate to an end portion thereof on the side of flowing out the exhaust gas. [0019] [Effect of the Invention] The porous catalyst cylinder is concentrically arranged to insert into the inner side of the diffuser pipe arranged in the muffler and therefore, the influence effected on the length of the muffler is inconsiderable compared with that in the conventional example where the separate catalyst device is arranged in series and further, the weight is small and the support is facilitated since it is constituted in a simple cylindrical shape and accordingly, compact formation of a total of the exhaust device can be achieved. [0020] In this case, the catalyst cylinder purifies the exhaust gas before expansion in the diffuser pipe and therefore, the purification efficiency is high and further, the catalyst cylinder can comparatively be prolonged to a degree substantially the same as the length of the diffuser pipe and accordingly, the surface area necessary for achieving a predetermined purification level can easily be secured. [0021] Moreover, the diffuser pipe is provided with a diverging shape and accordingly, the inner pressure of the exhaust gas flowing at an inner portion thereof is gradually lowered toward an end portion of the diffuser pipe on the side of the flowing out the exhaust gas and therefore, the exhaust gas in the catalyst cylinder is easy to flow out to outside through perforations formed at the outer peripheral portion and the purification efficiency is promoted also thereby. [0022] Accordingly, even in the case where the length is liable to be restricted as in a muffler for a small vehicle of a scooter or the like, a catalyst having a sufficient surface area can be arranged and a design therefor is simplified. [0023 ] Further, when the end portion of the catalyst cylinder on the side of flowing out the exhaust gas is projected in the direction of flowing out the exhaust gas longer than the end portion of the diffuser pipe on the side of flowing out the exhaust gas, the exhaust gas in the catalyst cylinder can easily be flown out to outside from the projected portion by utilizing expansion flow of the exhaust gas which comes out from the diffuser pipe and therefore, the purification efficiency is further promoted. [0024] Furthermore, when the flow path of the exhaust gas is secured between the catalyst cylinder and the diffuser pipe, the influence on pulsation of exhaust can be made difficult to effect and a design for preventing the output of an engine from lowering is facilitated. [0025] Furthermore, when the catalyst is carried on at least portions of both of the inner and outer peripheral faces of the diffuser pipe, firstly, the exhaust gas passing through the inside of the diffuser pipe is brought into contact and chemically reacted with the catalyst on the side of the inner peripheral face by which the catalyst on the side of the outer peripheral face is heated by the reaction heat. [0026] Then, when the exhaust gas which comes out from the diffuser pipe and is expanded, is brought into contact with the catalyst on the side of the outer peripheral face, the chemical reaction is expedited by the catalyst on the side of the outer peripheral face heated by the reaction heat of the catalyst on the side of the inner peripheral face and as a result, the purificalion efficiency of the exhaust gas after coming out from the diffuser pipe is promoted despite gradual lowering of the exhaust temperature. [0027] Further, when the catalyst is carried on at least portions of both of the inner and outer peripheral faces of the inserting portion of the exhaust tube which is arranged in the muffler and one end of which is communicated with the exhaust tube outside of the muffler, similarly as above, the temperature of the catalyst on the side of the outer peripheral face is elevated by utilizing the reaction heat generated by bringing the exhaust gas passing through the inside of the inserting portion of the exhaust tube at comparatively high temperatures with the catalyst on the side of the inner peripheral face and accordingly, the exhaust gas which flows out from the inserting portion of the exhaust tube and is expanded can be purified efficiently on the side of the outer peripheral face of the inserting portion of the exhaust tube. [0028] Accordingly, the catalyst can be carried in a comparatively narrow range and the cost can be reduced by that amount. [0029] Furthermore, in this case, when a range of carrying the catalyst includes a portion proximate to an end portion of the inserting portion of the exhaust tube on the side of flowing in the exhaust gas and a portion proximate to an end portion thereof on the side of flowing out the exhaust gas, firstly, at the portion proximate to the end portion on the side of flowing in the exhaust gas, the exhaust gas having the highest temperature in the inserting portion of the exhaust tube is purified efficiently by being brought into contact with the catalyst on the side of the inner peripheral face and the portion is intensively heated. [0030] Next, at the portion proximate to the end portion on the side of flowing out the exhaust gas, the exhaust gas maintaining a comparatively high temperature by the reaction heat at the portion proximate to the end portion on the side of flowing in the exhaust gas, is efficiently purified by being brought into contact with the catalyst on the side of the inner peripheral face and further, the portion is also heated by the reaction heat. [0031] Accordingly, the exhaust gas which comes out from the end portion on the side of flowing in the exhaust gas at a comparatively high temperature and is expanded, is firstly efficiently purified by being brought into contact with the catalyst on the side of the outer peripheral face which is provided on the outer peripheral face of the portion proximate to the end portion on the side of flowing out the exhaust gas and which is heated from the inner side, on the side of the outer peripheral face of the inserting portion of the exhaust tube, and is heated again by the reaction heat at this portion and is brought into contact with the catalyst on the side of the outer peripheral face of the portion proximate to the end portion on the side of flowing in the exhaust gas. [0032] At this moment, the catalyst on the side of the outer peripheral face of this portion is heated at a considerably high temperature from the inner side as described above and accordingly, the exhaust gas maintaining the comparatively high temperature is efficiently purified also at this portion. 10033] Accordingly, the exhaust gas after coming out from the inner portion of the exhaust tube can be maintained at high temperatures for a comparatively long time period and further, can be purified in a comparatively wide range of the outer peripheral face of the inner portion of the exhaust tube. [BRIEF EXPLANATION OF THE DRAWINGS] (Fig. 1] Fig. 1 is a total sectional view of a muffler portion in the length direction. [Fig. 2] Fig. 2 is a total view of an exhaust device us ing a muf fler. .[Fig. 3] Fig. 3 is an enlarged sectional view taken from a line 3-3 of Fig. 1. [Fig. 4] Fig. 4 is an enlarged sectional view taken from a line 4-4 of Fig. 1. [Fig. 5] Fig. 5 is a partially broken view of an outlook of a catalyst cylinder. [Fig. 6] Fig. 6 is an enlarged sectional view taken from a line 6-6 of Fig. 5. [0034 ] [Preferred Embodiments] An explanation will be given of an embodiment of the present invention in reference to the drawings as follows. Fig. 1 is a total sectional view in respect of a length direction of a muffler portion. Fig. 2 is a total view of an exhaust device using the muffler, Fig. 3 is an enlarged sectional view taken from a line 3-3 of Fig. 1, Fig. 4 is an enlarged sectional view taken from a line 4-4 of Fig. 1, Fig. 5 is a partially broken view of an outlook of a catalyst cylinder, and Fig. 6 is an enlarged sectional view taken from a line 6-6 of Fig. 5. [0035] In Fig. 2. an end portion of the downstream side of an exhaust tube 1, an end portion on the upstream side of which is connected to an exhaust port of an engine, not illustrated, is connected to the upstream side of a muffler 2. Notation 3 designates a stay for attaching to a vehicle body. [0036] Further, in the following explanation, the end portion on the downstream side of the exhaust tube 1 is referred to as a rear endportion, a portion of the muffler 2 connected thereto is referred to as a front portion and a side opposed thereto in the length direction is referred to as a rear portion. Further, in respect of end portions in the length direction of each of a first and a second diffuser pipe and a catalyst cylinder, mentioned later, the upstream side of the exhaust gas flowing at the inside of each of them is referred to as a front end portion and a side opposed thereto is referred to as a rear end portion. [0037] As is apparent from Fig. 1, the inside of the muffler 2 is partitioned into a first expansion chamber 6, a second expansion chamber 7, and a third expansion chamber 8 successively from the front side by partition walls 4 and 5. A diffuser pipe in a diverging shape penetrating the first expansion chamber 6 through the third expansion chamber 8, is arranged in the front and rear direction at the inside of the muffler 2. [0038] Diffuser pipes penetrating the first expansion chamber 6 through the third expansion chamber 8 and forming a diverging shape are arranged in the forward and backward direction at inside of the muffler. [0039] The diffuser pipes correspond to the inserting portion of the exhaust tube according to the present invention and is constituted by a first diffuser pipe 10 and a second diffuser pipe 11 in continuation to each other. [0040] The front end portion of the first diffuser pipe 10 penetrates a front cap 12 where it is connected to the rear end portion of the exhaust tube I and the rear end portion thereof is connected to the front end portion of the second diffuser pipe II in the second expansion chamber 7. [0041] A catalyst cylinder 13 is arranged in the second diffuser pipe 11 substantially concentrically and the respective rear end portions of the second diffuser pipe 11 and the catalyst cylinder 13 are opened at a vicinity of an end cap 14 in the third expansion chamber 8. [0042] The third expansion chamber 8 and the first expansion chamber 6 are communicated with each other via a communicating tube 15 and the first expansion chamber 6 and the second expansion chamber 7 are communicated with each other via a communicating tube 16 (refer to Fig. 3). [0043 ] Further, the second expansion chamber 7 is communicated with the atmosphere via a tail pipe 17, the end portion of which is projected to the outside by penetrating the end cap 14 and an end portion of the tail pipe 17 opened to the inside of the second expansion chamber 7 constitutes an external exhaust port 18. [0044 J Notation 20 designates an outer cylinder of the muffler 2 in a cylindrical shape and a sound absorbing material 21 is held by an inner cylinder 22 made of a punching metal on the inner side of the outer cylinder at a portion thereof in the third expansion chamber 8. [0045] Further, a silencer 23 is also attached to the outer periphery of the second diffuser pipe 11, a sound absorbing material 24 is insertingly mounted to the inner side and a number of small perforations 25 are formed at the wall face of the second diffuser 11 at this portion. [0046] Inner plates 26 an 27 made of a punching metal are provided on the respective inner sides of the front cap 12 and the end cap 14 and the sound absorbing materials 28 and 29 are held respectively between the front cap 12 and the inner plate 26 and between the end cap 14 and the inner plate 27. [0047 ] Exhaust gas which has entered from the exhaust tube 1, proceeds from the first diffuser pipe 10 into the second diffuser pipe 11 and is expanded by coming out from the respective rear end portions of the second diffuser pipe 11 and the catalyst cylinder 13 into the third expansion chamber 8. [0048] Thereafter, the exhaust gas passing through the communicating tube 15, enters the first expansion chamber 6 and is expanded, passes through further the communicating tube 16 and is expanded again in the second expansion chamber and thereafter, exhausted to the atmosphere by passing through the tail pipe 17 from the external exhaust port 18. [0049] As shown by Fig. 4 through Fig. 6, stays 30 are fixed to the outer periphery of the front end portion of the catalyst cylinder 13 by plug welding portions 31 and abutment portions 32 formed at portions thereof are supported in a cantilever fashion by being brought into contact with the inner peripheral face of the front end portion of the second diffuser pipe 11. [0050] A flow path 33 constituting a sufficiently large gap between the catalyst cylinder 13 and the second diffuser pipe 11, is formed and a catalyst 34 is carried on the respective inner and outer peripheral faces of the second diffuser pipe 11 and the catalyst cylinder 13. [0051] The catalyst cylinder 13 is fabricated by forming a punching metal in a cylindrical shape and welding end portions thereof in the peripheral direction to provide a number of small perforations 35 and carries the catalyst 34 via a ceramic coating at its surroundings and publicly-known composition and method can be adopted for the catalyst 34 and the method of carrying thereof. [0052] The stay 30 is provided with a fixing portion 36, bent portions 37, and the abutment portions 32, and the fixing portion 36 is a portion attached to the catalyst cylinder 13 by the plug welding portion 31 along the outer periphery of the front end portion of the catalyst cylinder 13. [0053 ] The bent portions 37 are portions formed by bending both end portions of the fixing portions 36 in the peripheral direction of the catalyst cylinder 13 to the external side in the radius direction of the catalyst cylinder 13. [0054] The abutment portion 32 is a portion formed by further bending the front end of the bent portion 37 to be directed along the inner peripheral face of the front portion of the second diffuser pipe 11 and is in a tapered shape having the same inclination as that of the inner peripheral face of the second diffuser pipe 11. [0055] Accordingly, when the catalyst cylinder 13 is inserted into the second diffuser pipe 11 from the side of the rear end portion, the abutment portions 32 are brought into close contact with the inner peripheral face of the front portion of the second diffuser pipe 11 by taper matching. [0056] In this case, an interval of a dimension "d" is maintained between the fixing portion 36 and the abutment portion 32 by the bending portion 37 and therefore, the gap having the dimension "d" or more is formed between the catalyst cylinder 13 and the inner peripheral face of the second diffuser pipe 11 and the gap portion constitutes the flow path 33 described above (Fig. 4} . [0057] Further, although not clearly shown in the drawings, the abutment portion 32 is supported in a cantilever fashion to the inner peripheral face of the front portion of the second diffuser pipe 11 by performing plug welding. [0058] By performing the plug welding at this portion, after welding the abutment portions 32, the silencer 23 is welded onto the outer peripheral face of the second diffuser pipe 11 by fitting it from the side of the small diameter portion. [0059] The rear end portion of the catalyst cylinder 13 is projected from the rear end portion of the second diffuser pipe 11 considerably to the downstream side as shown by a dimension D (Fig. 1} . [0060] Further, the catalyst 34 is similarly carried on the inner and outer peripheral faces of the second diffuser pipe 11, the inner peripheral face of the first diffuser pipe 10 in the first expansion chamber 6, and the outer peripheral face thereof in the first expansion chamber 6. [0061] However, at a portion of the outer peripheral face of the first diffuser pipe 10 penetrating the partition wall 4, the catalyst is not carried by previously masking the portion by a masking tape whereby the weldability in respect of the partition wall 4 is secured. [0062] Further, notation 38 in Fig. 1 designates an end portion of the first dif fuser pipe 10 on the side of flowing in the exhaust gas and notation 39 designates an end portion of the second diffuser pipe 11 on the side of flowing out the exhaust gas. Further, notation 13a designates an end portion of the catalyst cylinder 13 on the side of flowing out the exhaust gas. [0063] Next, an explanation will be given of the operation of the embodiment. In Fig. 1, exhaust gas which has entered the first diffuser pipe 10 from the exhaust tube 1, is brought into contact with the catalyst 34 carried on the inner peripheral face in the highest temperature state and is purified efficiently and the first diffuser pipe 10 is heated from the inner side by the exhaust gas at high temperatures and the reaction heat. [0064] Thereafter, the exhaust gas which has entered the second diffuser pipe 11, is divided to proceed in the flow path 33 formed between the second diffuser pipe 11 and the catalyst cylinder 13 and proceed in the catalyst cylinder 13. [0065] The exhaust gas proceeding the inside of the flow path 33 is brought into contact with the catalyst 34 on the inner peripheral face of the second diffuser pipe 11 and the outer peripheral face of the catalyst cylinder 13 in a state of maintaining a comparatively high temperature since it has been heated in the first diffuser pipe 10 whereby oxidation is expedited and the exhaust gas is purified further. [0066] Further, the exhaust gas proceeding the catalyst cylinder 13 is purified by the catalyst 34 on the inner peripheral face of the catalyst cylinder 13 and portions thereof gradually pass to the outside through the small perforations 35 of the catalyst cylinder 13 in which the exhaust gas is purified by being brought into contact with the catalyst 34 and expediting the chemical reaction. [0067] At this moment, since the second diffuser pipe 11 is in a diverging shape, the inner pressure of the exhaust gas flowing at the inside is gradually lowered toward the rear end portion and the exhaust gas in the catalyst cylinder 13 is easy to flow out to the outside via the small perforation 35 whereby the purification efficiency is promoted. [0068] Moreover, since the catalyst cylinder 13 is projected from the second diffuser pipe 11 to the downstream side by the dimension D, the exhaust gas passing through the catalyst cylinder 13 is easy to be absorbed to the outside at the projected portion via the small perforation 35 by utilizing the expansion flow of the exhaust gas expanding after coming out from the rear end portion of the second diffuser pipe 11 and therefore, the purification efficiency is further promoted. [0069] Further, the inner peripheral face of the second diffuser pipe 11 and the surface of the catalyst cylinder 13 are heated by the reaction heat accompanying the chemical reaction at the carried catalyst 34 and the temperature thereof is elevated and the exhaust gas which has passed through the second diffuser pipe 11 and the catalyst cylinder 13 is also heated. [0070] Accordingly, when the exhaust gas which has passed through the second diffuser pipe 11 and the catalyst cylinder 13, is expanded in the third expansion chamber 8 and is proceeding toward the first expansion chamber 6 while gradually lowering the exhaust temperature, the exhaust gas is brought •into contact with the external surface of the second diffuser pipe 11 and is purified further by the catalyst 34 carried there. [0071] At this moment, the exhaust gas as well as the second diffuser pipe 11 and the catalyst cylinder 13 are respectively heated and therefore, the purification efficiency is promoted. [0072] When the exhaust gas which has been purified in this way in the third expansion chamber 8, enters the first expansion chamber 6 and is brought into contact with the catalyst 34 carried on the external surface of the first diffuser pipe 10." [0073 ] At this moment, the temperature of the first diffuser pipe 10 is sufficiently elevated by being heated from the inner side and further, the exhaust gas entering from the third expansion chamber 8 is also heated by the reaction heat of the second diffuser pipe 11 and the catalyst cylinder 13 and a romparatively high temperature is maintained despite elapse of a comparatively long period of time since coming out of the second diffuser pipe. [0074] Therefore, also in the first expansion chamber 6 at a vicinity of the external exhaust port 18, the exhaust gas is brought into contact wi.th the catalyst 34 carried on the outer surface of the first diffuser pipe 10 and is final lypuri fied efficiently and to a degree sufficient for exhausting to the outside. [0075] Accordingly, the exhaust gas flowing in from the exhaust tube 1 is purified in the muffler 2 at a high purification efficiency and accordingly, a range of directly carrying the catalyst 34 except the catalyst cylinder 13, is made sufficient by the first diffuser pipe 10 and the second diffuser pipe 11, and compared with the case where the catalyst is carried by the partition walls 4 and 5 as well as the communicating tubes 15 and 16 and the tail pipe 17 and the like, the surface of the catalyst can significantly be reduced and the cost can be reduced by that amount. [0076] Further, in respect of the catalyst cy 1 indcr 13, the porous catalyst cylinder 13 is concentrically arranged to insert into the second diffuser pipe 11 and therefore, compared with the conventional device where the catalyst cylinder 13 is arranged in series, the influence effected on the length of the muffler 2 is inconsiderable, the weight is light and the catalyst 13 can be supported by the diffuser pipe 11 in a cantilever fashion and accordingly, compact formation of a total of the exhaust device is facilitated. [0077] In this case, the catalyst cylinder 13 purifies the exhaust gas before expansion in the first diffuser pipe 11 and therefore, the purification efficiency is high, the catalyst cylinder 13 can be made comparatively long to a degree substantially the same as the length of the first diffuser pipe 11 and therefore, the surface area necessary for achieving a predetermined purification level can easily be secured. [0078 ] Moreover, even in the case where the length is apt to be restricted as in a muffler for a small-sized vehicle of a scooter or the like, a catalyst having a sufficient surface area can easily be arranged and a design therefor is simplified. [0079] Furthermore, a separate catalyst device is not arranged in series with the exhaust tube 1 and the diffuser pipes (10, 11) and further, the flow path 33 of exhaust gas can be secured between the catalyst cylinder 13 and the second diffuser pipe 11 and the influence in respect of the pulsation of exhaust is difficult to be effected and accordingly, the purification efficiency can be promoted without lowering the output of an engine and a design therefor is facilitated. [0080] Incidentally, the present invention can be modified variously and, for example, a plurality of catalyst cylinders having different diameters can also be arranged to insert concentrically into the second diffuser pipe 11. [0081 ] Further, the catalyst 34 carried on the internal and external peripheral faces of the diffuser pipes (10, 11) can be omitted or restricted to portions thereof. [0082] Conversely, when a sufficient surface area of catalyst can be secured, only a structure where the catalyst 34 is directly carried on the inner and outer peripheral faces of the diffuser pipes (10, 11) can be constituted by omitting the catalyst cylinder 13. [0083 ] In this case, the catalyst can also be carried in a range including at least portions of the diffuser pipes (10, 11) respectively proximate to the inlet side and the outlet side. [0084 ] Further, the range may be constituted by a portion of the exhaust tube 1 extending to the inside of the muffler 2 in place of the diffuser pipes (10, 11) . [Explanation of Reference Numerals] 1: exhaust tube, 2: muffler, 10: first diffuser pipe, 11: second diffuser pipe, 13: catalyst cylinder, 30: stay, 33: flow path, 34: catalyst WE CLAIM : 1. An exhaust device with catalyst including an exhaust tube (1) extended from an engine, a muffler (2) connected to the exhaust tube (1), an inserting portion (10, 11) of the exhaust tube (1) which is arranged in the muffler (2) and one end (38) of which is connected to communicate with said exhaust tube (1) and a catalyst carried at inside of the muffler: said inserting portion (10, 11) of the exhaust tube (1) constituting a diffuser pipe (11) a diameter of which is widened in a diverging shape in a direction of flowing out exhaust gas; and a catalyst cylinder (13) which is constituted by forming a porous material in a cylindrical shape and a surface of which carries the catalyst is inserted into and supported by the diffuser pipe (11) substantially concentrically. 2. An exhaust device with catalyst as claimed in claim 1, wherein an end portion (13a) of the catalyst cylinder (13) on a side of flowing out the exhaust gas is projected in the direction of flowing out the exhaust gas longer than an end portion (39) of the diffuser pipe (11) on the side of flowing out the exhaust gas. 3. An exhaust device with catalyst as claimed in claim 1 or 2; wherein said catalyst cylinder (13) is supported on an inner side of the diffuser pipe (11) by a supporting member (30) and a flow path of the exhaust gas is formed between the catalyst cylinder (13) and the diffuser pipe (11). 4. An exhaust device with catalyst as claimed in anyone of claims 1 through 3, wherein said catalyst (34) is carried on at least portions of both and outer peripheral faces of the diffuser pipe (11). 5. An exhaust device as claimed in claim 1, wherein exhaust gas flowing out from the inserting portion (10, 11) of the exhaust tube (1) is exhausted to outside of the muffler (2) after being expanded to a surrounding of said inserting portion (10, 11) of the exhaust tube (11) in an expansion chamber (6, 7, 8) inner portion (10, 11) of the muffler (2) and the exhaust gas is purified by the catalyst (34): said catalyst (34) is carried by at least portions of both of inner and outer peripheral faces of said inserting portion (10, 11) of the exhaust tube (1). 6. An exhaust device with catalyst as claimed in claim 5, wherein a range of carrying said catalyst (34) on both of the inner and outer peripheral faces of said inserting portion (10, 11) of the exhaust tube (1) includes a portion proximate to an end portion (38) of the inserting portion (10, 11) of the exhaust tube (1) on a side of flowing in the exhaust gas and a portion proximate to an end portion (39) side of flowing out the exhaust gas. 7. An exhaust device with catalyst substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

3839-del-1997-abstract.pdf

3839-del-1997-claims.pdf

3839-del-1997-correspondence-others.pdf

3839-del-1997-correspondence-po.pdf

3839-del-1997-description (complete).pdf

3839-del-1997-form-1.pdf

3839-del-1997-form-13.pdf

3839-del-1997-form-19.pdf

3839-del-1997-form-2.pdf

3839-del-1997-form-3.pdf

3839-del-1997-form-4.pdf

3839-del-1997-form-6.pdf

3839-del-1997-gpa.pdf

3839-del-1997-petition-137.pdf

3839-del-1997-petition-138.pdf