Exhaust system for motorcycle

The present invention relates to an exhaust device that reduces exhaust noise of an engine mounted on a motorcycle.

Conventionally, an exhaust device connected to a multi-cylinder engine mounted on a motorcycle has a plurality of exhaust pipes extending from the engine guided to the lower side of the engine, and their rear ends are connected to an exhaust chamber to be assembled. The exhaust chamber is connected to a muffler located above the rear end of the swing arm via a joint pipe. The silencer is placed above the rear end of the swing arm because the required bank angle (tilt angle) cannot be obtained if it is placed below, and the side from the center line of the vehicle body to avoid the swing arm. Since it is necessary to install it at a position relatively separated from the other side, it is necessary to set it at a high position in relation to the bank angle. As described above, in the exhaust device, since the muffler is arranged on the rear side greatly separated from the engine, the exhaust pipe and the joint pipe connecting the two become long, which causes an increase in weight.

Therefore, conventionally, an exhaust device for a motorcycle has been proposed so as to achieve both weight reduction by shortening the overall length of the device and an increase in the bank angle of the vehicle body (for example, Patent Document). This exhaust device is arranged at a position extending from the lower part of the engine to the front end of the rear wheel, and the exhaust chamber has an approximately L-shaped side view in which the rear part partially bulges upward, and the upward bulge is formed. By connecting a silencer, the overall length is shortened and the capacity of the entire device is increased.<patcit num="1"><text>Japanese Patent No. 2601387</text></patcit>

<p> However, in the exhaust device, since the exhaust chamber is arranged below the engine, there is not enough space above the exhaust chamber, so that the shape must be flat in order to obtain the required bank angle. Therefore, the exhaust device cannot obtain a sufficient capacity.</p><p> The present invention has been made in view of the above-mentioned conventional problems, and while the muffler has a shape having a length required for the output performance of the engine and a sufficient capacity for the sound deadening effect, the overall length of the device is shortened to reduce the weight. It is an object of the present invention to provide an exhaust system for a motorcycle that can be planned and the center of gravity can be further lowered.</p>

<p> In order to achieve the above object, in the exhaust device of the motorcycle according to the present invention, the engine is arranged between the front wheels and the rear wheels, and the muffler connected to the exhaust pipe of the engine is formed between the rear surface and the rear wheels of the engine. The muffler has a muffler casing arranged along the front-rear direction, the muffler casing has a front wall and a rear wall, the exhaust pipe is connected to the front wall, and the rear wall is connected. A tail pipe that exhausts exhaust gas is connected to<u style="single">The width of the muffler casing in the left-right direction is set smaller than the length in the front-rear direction, the tail pipe is arranged at an upper right side of the muffler, and the right side of the bottom surface of the muffler casing is moved from the center of the bottom surface to the tail pipe. It is tilted diagonally upward toward the location where</u>。 </p><p> In this configuration, the muffler is placed between the rear surface and the rear wheels of the engine, where there is a relatively large space above, so the muffler has an outer shape with a height that allows sufficient capacity. For example, a large catalyst can be installed to obtain the required sound deadening effect. Further, since the muffler is located behind the engine, the total length of the exhaust passage including the exhaust pipe and the muffler can be made relatively large to be the length required for the output performance of the engine. Further, since the muffler is arranged in a sufficient space in the vertical direction, the muffler can be arranged at a suitable height position where the center of gravity can be lowered as much as possible within the range where the required bank angle can be obtained. ..</p><p> In a preferred embodiment of the present invention, the muffler is located below the lower end of the main frame including the swing arm bracket. According to this configuration, there is an empty space in the left-right direction at the part below the lower end of the main frame, so the left-right width of the muffler should be as large as possible within the range where the required bank angle can be obtained. It can be set, and a larger muffling effect can be obtained.</p><p> In another preferred embodiment of the invention, the muffler is located behind the oil pan at the bottom of the engine. Since the rear surface of the oil pan is usually located slightly forward of the rear surface of the engine, according to this preferred embodiment, the front end of the muffler can be extended forward to a position close to the rear surface of the oil pan. The length of the muffler in the front-rear direction can be set even larger to improve the muffler performance.</p><p> In still another preferred embodiment of the present invention, exhaust purifiers provided in each of the plurality of exhaust pipes from the engine are juxtaposed in the muffler in the left-right direction. According to this configuration, the muffler can be made into a relatively flat shape, and the exhaust purifier built into the muffler is not exposed to the outside air, so it has a high heat retention effect, so immediately after the engine starts. The temperature rises rapidly from the engine to activate it, and the purification reaction to the exhaust gas from each exhaust gas is promoted.</p>

Hereinafter, the best embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side view showing a motorcycle provided with an exhaust device according to the first embodiment of the present invention. In this motorcycle, the front fork 2 is supported by the front end of the main frame 1 that constitutes the front half of the body frame FR, and the front wheel 4 is supported by the bottom case 3 provided at the lower end of the front fork 2 via the axle 7. ing. A handle 9 is attached to the upper bracket 8 that supports the front fork 2. A swing arm bracket 10 is formed in the lower part of the rear end of the main frame 1, and the front ends of a pair of left and right swing arms 11 are supported by the swing arm bracket 10 so as to swing up and down via a pivot shaft 12. A rear wheel 13 is supported at the rear end of the swing arm 11. The seat rail 14 connected to the rear part of the main frame 1 constitutes the latter half of the vehicle body frame FR, and the shock absorber 17 of the rear wheel 13 is bridged between the main frame 1 and the swing arm 11. .. A 4-cycle engine E is supported in the lower center of the main frame, and the rear wheels 13 are driven from this engine E via a chain 18.

A rider's seat 19 and a passenger's seat 20 are supported on the seat rail 14. A fuel tank 21 is attached between the steering wheel 9 and the rider's seat 19 at the upper part of the main frame 1, that is, the upper part of the vehicle body. Further, in this embodiment, a resin cowling 22 that covers a portion from the front of the steering wheel 9 to the side of the front portion of the vehicle body is attached to the front portion of the vehicle body, and the rear portion of the cowling 22 is the engine E. It covers the sides and the bottom.

In FIG. 2, which is an enlarged view of a partially broken main part of FIG. 1, the engine E is a 2-cylinder 4-cycle engine in this example, and has a crankcase 24, a cylinder 27, a cylinder head 28, and a cylinder head cover.<u style="single">29</u>It also includes an engine body 23 having an oil pan 30 and a transmission 31. The exhaust device guides a plurality of (two in this example) exhaust pipes 32 having their front ends connected to the cylinder head 28 from below to the rear of the engine E, and a muffler at the rear end of each of the exhaust pipes 32. It has a configuration in which 33 are connected. The muffler 33 is arranged between the rear surface ER of the engine E and the rear wheel 13, and is located at the center of the vehicle body in the left-right direction. In this embodiment, the muffler 33 is arranged between the rear wheel 13 and the portion facing the oil pan 30 in the lower portion of the rear surface ER of the engine E having the above configuration, and the swing arm bracket is arranged via the support bracket 34. It is supported by the lower end of 10. Here, the rear surface ER of the engine E is the rear surface of the entire engine including the engine body 23 and the transmission 31.

FIG. 3 shows a cut plan view of the exhaust device of FIG. In the figure, the muffler 33 has a muffler casing 37 having a uniform cross-sectional shape along the front-rear direction, and two exhaust gas introduction pipes 38 and 38 are arranged through the front wall 37a of the muffler casing 37. , The rear ends of the two exhaust pipes 32 and 32 connected to the two-cylinder engine E are connected to the front ends of these exhaust gas introduction pipes 38 and 38, respectively. In addition, the two exhaust gas introduction pipes 38 and 38 are communicated with each other by a communication pipe 39, which causes an exhaust interference effect described later and facilitates the outflow of exhaust gas from each of the exhaust pipes 32 and 32. There is. The rear part of the exhaust pipe 32 and the exhaust gas introduction pipe 38 connected to the exhaust pipe 32 are located below the engine E shown in FIG.

The muffler 33 has three chambers, the first muffler chamber 42, the second muffler chamber 43, and the exhaust chamber 44, due to the two partition walls 40, 41, the front and rear walls 37a, 37b, and the peripheral wall 37c inside the muffler casing 37. It is partitioned. The first muffler chamber 42 is provided at the rear of the muffler casing 37, the second muffler chamber 43 is provided at the front of the muffler casing 37, and the exhaust chamber 44 is provided between the two muffler chambers 42 and 43. In the second sound deadening chamber 43, two cylindrical catalysts (exhaust gas purifiers) 47, 47 are juxtaposed in the left-right direction in a state of being individually connected to two exhaust gas introduction pipes 38, 38. A pair of first communication pipes 48, 48 provided so as to penetrate the partition walls 40, 41 are connected to the catalysts 47, 47, respectively. Further, the first muffling chamber 42 and the second muffling chamber 43 are communicated with each other by a pair of second communication pipes 49 provided so as to penetrate the partition walls 40 and 41, respectively. Further, the second muffling chamber 43 and the exhaust chamber 44 are communicated with each other by a pair of third communication pipes 50 and 50 provided so as to penetrate the partition wall 40. The exhaust chamber 44 communicates with the outside by a tail pipe 51 provided so as to penetrate the partition wall 41 and the rear wall 37b of the muffler casing 37, respectively.

The muffler 33 is located between the rear ER of the engine E and the rear wheels 13 shown in FIG. 2, unlike the configuration in which the exhaust chamber is installed below the engine where there is no space above as in the conventional exhaust device. It is placed in a place where there is a relatively large space above. As a result, the muffler 33 forms the muffler casing 37 in a size having a height capable of obtaining a sufficient capacity, and the first communication pipes 48, 48 are placed in the central portion in the height direction inside the muffler casing 37 at the lower portion. The second communication pipes 49 and 49 are arranged, and the third communication pipes 50 and 50 are arranged at the upper part, respectively.

Therefore, as shown in FIG. 3, the exhaust gas G from the engine E is introduced into the catalysts 47 and 47 through the exhaust pipes 32 and 32 and the exhaust gas introduction pipes 38 and 38, and burned by the oxidation reaction in the catalyst 47. And harmful HC and CO₂Purification is promoted. This purified exhaust gas G flows into the first muffling chamber 42 through the first communication pipes 48 and 48, expands, contracts in the second communication pipes 49 and 49, and passes through the second communication pipe 49,49. It flows into the muffling chamber 43 and expands again, and then flows into the exhaust chamber 44 through the third communication pipes 50 and 50 to repeat contraction and expansion, and then to the outside through the tail pipe 51. It is discharged.

In this way, since the muffler 33 repeatedly expands and contracts the exhaust gas inside the muffler casing 37, the exhaust gas G can be discharged to the outside in a state where the exhaust noise is sufficiently reduced. Also, since the muffler 33 is placed between the rear ER of the engine E and the rear wheel 13, the position of the muffler 33 is closer to the rear than when the muffler is placed below the engine, so the exhaust pipe By making the total length of the exhaust passage including 32, exhaust gas introduction pipe 38, muffler 33 and tail pipe 51 appropriate, the pulsation due to back pressure from engine E can be effectively used to improve the output performance of engine E. It can be improved. Furthermore, since the muffler 33 is located in the space between the rear ER of the engine E and the rear wheels 13, the position of the muffler 33 can be lowered to set the center of gravity low, and this space has a margin in the vertical direction. Therefore, the height of the muffler 33 can be increased to increase the capacity of the muffler 33.

Moreover, since the catalyst 47 is arranged inside the muffler casing 37 to keep it warm and is arranged on the most upstream side inside the muffler 33, it remains at a high temperature immediately after being discharged from the engine E. Exhaust gas G is introduced to effectively cause an oxidation reaction, and the exhaust gas G that has risen to a higher temperature due to the oxidation reaction by this catalyst 47 passes through the first muffling chamber 42 and the catalyst 47 is arranged in the second muffling chamber. Since it is guided to 43, the high-temperature exhaust gas G flowing into the second muffling chamber 43 creates a high-temperature atmosphere around the catalyst 47, which causes the catalyst 47 to rise in temperature more rapidly and be activated. Therefore, this exhaust device has an advantage that the catalyst 47 is rapidly activated immediately after the start even immediately after the motorcycle has a cold start, and the purification action of the exhaust gas G is started promptly. Further, since the pair of exhaust gas introduction pipes 38 and 38 are communicated with each other by the communication pipe 39, the phase of the exhaust gas G discharged from each of the two cylinders is shifted by 180 °, and the negative pressure of one causes the other. Exhaust gas G is sucked smoothly due to the exhaust interference effect that sucks the exhaust gas G.

The rear ER of the Oinpan 30 at the bottom of the engine E is usually set closer to the front than the rear end 31a of the transmission 31, whereas the muffler 33 is located behind the Oinpan 30, so the muffler 33 The front end can be extended forward to a position close to the rear ER of the Oinpan 30. As a result, the capacity of the muffler 33 can be further increased by setting a large length in the front-rear direction, and the sound deadening performance of the exhaust can be improved.

FIG. 4 shows a cross-sectional view taken along the line IV-IV of FIG. In the figure, the muffler 3 is arranged below the lower ends of the pair of left and right swing arm brackets 10 and 10 in the main meleeme 1 (FIG. 1). There is an empty space in the left-right direction below the lower ends of the swing arm brackets 10 and 10, that is, the muffler 33 can be extended to the left and right without being restricted by the swing arm brackets 10 and 10. The width W of the muffler casing 37 of the muffler 33 in the left-right direction can be set to be larger than the distance C of the facing inner surfaces of the swing arm brackets 10 and 10. As a result, a pair of catalysts 47, 47 having a relatively large diameter can be arranged side by side in the left-right direction inside the muffler 33, and the purifying action of the exhaust gas G is improved. However, the width W in the left-right direction of the muffler casing 37 is set to be smaller than the length in the front-rear direction, thereby increasing the bank angle θ2, which will be described later.

In the exhaust device, since the chain 18 is arranged on the left side, only one tail pipe 51 is provided at the upper right side of the muffler 33, and the right side of the bottom surface of the muffler casing 37 is moved from the center to the tail pipe 51. It is tilted diagonally upward toward the arrangement location. As a result, the bank angle θ1 in the empty state of the motorcycle is not affected, but the bank angle θ2 when the vehicle body carries the rider and the full stroke is lowered can be increased. Further, since the tail pipe 51 is arranged to extend in the front-rear direction of the vehicle body and exhausts the exhaust gas G to the rear of the vehicle body, there is an advantage that noise to the side during acceleration or the like is reduced.

Further, since the muffler casing 37 has an outer shape having a uniform cross section, for example, a single plate material is bent in an annular shape, and both ends thereof are connected to each other by welding or caulking to form a tubular shape. There is an advantage that it can be easily manufactured by simply closing the openings at both ends with flat plates (front and rear walls 37a and 37b in Fig. 3).

If the capacity of the oil pan 30 of the engine E is insufficient, the oil pan 30 is projected downward as shown by the alternate long and short dash line 30a in FIG. As shown by the dotted line, it can be arranged to be inserted between the pair of exhaust gas introduction pipes 38, 38. Further, since the chain 18 shown in FIG. 2 may only interfere with the rear end portion of the muffler 33, the muffler casing 37 is provided with the bulging portion 37A that bulges upward as shown by the alternate long and short dash line. It is also possible to provide a bulging portion 37B that bulges to the left in the front portion as shown by a two-dot chain line in FIG. 3, which can further increase the capacity of the muffler 33. .. As shown by the alternate long and short dash line in Fig. 4, the bulging portion 37B to the left can maintain a large bank angle θ2 at the time of full stroke by inclining the bottom surface diagonally upward toward the left. .. When such bulging portions 37a and 37b are provided, the muffler casing 37 is formed by an upper casing and a lower casing in which the muffler casing 37 is divided into upper and lower halves, and both casing portions are abutted against each other and connected by means such as welding. Therefore, it can be easily manufactured.

Further, in the above embodiment, the case where the motorcycle is mounted on the motorcycle equipped with the 2-cylinder engine E shown in FIG. 2 is illustrated, but for the 4-cylinder engine, two exhaust pipes are provided for each. After assembling through the two collecting pipes, these two collecting pipes may be connected to the exhaust gas introduction pipes 38 and 38 in FIG. Further, the tail pipes 51 may be provided on the left side as a pair if necessary, and in that case, the left tail pipes may be arranged at a position where they do not interfere with the chain.

FIG. 5 shows an exhaust device for a motorcycle according to a second embodiment, (a) is a cut plan view, and (b) is a VV line sectional view of (a). In the figure, the same or equivalent as those in FIGS. 3 and 4 are designated by the same reference numerals, and duplicate description will be omitted. In this exhaust system, the outlets of the pair of left and right catalysts 47 are connected to the two inlets of the bifurcated collecting pipe 52 and assembled, and then the outlet of the collecting pipe 52 is connected to the first communication pipe 48. It is formed in a connected exhaust gas passage. In this muffler 33, in addition to obtaining the exhaust interference effect by the communicating pipe 39, the exhaust interference effect can also be obtained by the collecting pipe 52, so that the exhaust gas G can be sucked more smoothly.

<figref num="1">It is a side view which shows the motorcycle which provided the exhaust device which concerns on 1st Embodiment of this invention.</figref><figref num="2">It is an enlarged view which partially broke the main part of FIG.</figref><figref num="3">It is a cutting plan view of the exhaust device of FIG.</figref><figref num="4">It is sectional drawing along the IV-IV line of FIG.</figref><figref num="5">An exhaust device for a motorcycle according to a second embodiment is shown, (a) is a cut plan view, and (b) is a VV line sectional view of (a).</figref>

Code description

1 ... Mainframe 4 ... Front wheels 10 ... Swing arm bracket 13 ... Rear wheels 30 ... Oil pan 32 ... Exhaust pipe 33 ... Muffler 47 ... Catalyst (exhaust purifier) ) E ... Engine ER ... Rear of the engine