JP4532198B2 - Motorcycle exhaust system - Google Patents

Description

  The present invention relates to an exhaust device for a motorcycle.

  FIGS. 15 and 16 show an example of a conventional exhaust system for a motorcycle (Patent Document 1). In FIG. 16 showing a schematic plan view, two exhaust mufflers 101 and 102 are placed on the left and right above the rear wheel 100. The exhaust pipe 103 connected to the front end exhaust port of the engine 110 extends rearward through the lower side of the engine 110 and is displaced to the right side, and the rear part of the exhaust pipe 103 is located on the rear side of the engine 110. And the right branch exhaust pipe 105 is connected to the right exhaust muffler 102, and the left branch exhaust pipe 106 extends above the rear wheel 100. It crosses to the left and is connected to the exhaust muffler pipe 101 on the left side.

  In FIG. 15, which is a side view, the exhaust muffler 101 (and 102) is disposed between the rear frame 104 and the rear wheel 100 in a side view.

  As in the above-described structure, the exhaust muffler 101, 102 is maintained while branching the single exhaust pipe 103 into the left and right exhaust mufflers 101, 102 while maintaining the flexibility of the exhaust system layout and the compactness of the vehicle. The total capacity is increased.

That is, according to the exhaust device of FIGS. 15 and 16, the exhaust gas from the exhaust pipe 103 is dispersed into the two exhaust mufflers 101 and 102 and is discharged from the respective exhaust mufflers 101 and 102. The total capacity of the exhaust mufflers 101 and 102 can be used as an expansion chamber, thereby improving the output and the silencing effect.
JP 2003-48592 A

  However, the exhaust system shown in FIGS. 15 and 16 is configured to always use both exhaust mufflers 101 and 102 at the same time regardless of operating conditions, such as during high load operation and low load operation. The flow of exhaust gas cannot be arbitrarily changed according to the above. In addition, since the purpose is to increase the capacity of the exhaust expansion chamber, the exhaust mufflers 101 and 102 have substantially the same internal structure, and the exhaust pressure (exhaust gas back pressure) is also substantially the same. It has become.

  Therefore, for example, when driving on an expressway, the exhaust gas back pressure can be reduced to achieve higher engine output. On the other hand, when driving in urban areas, the noise reduction effect is not much expected. Can not. In other words, depending on the operating conditions, there may be a case where the silencing effect cannot be expected.

  Further, as shown in FIG. 16, since the exhaust gas is branched immediately before the entrance of the right exhaust muffler 102, the flow of the exhaust gas is suddenly changed, leading to a decrease in exhaust efficiency. In order to mitigate such a rapid change in the direction of the exhaust gas flow, the left branch exhaust pipe 106 is formed in a curved shape. However, if it is made too long in a curved shape, the compactness is lacking.

(Object of invention)
The present invention distributes exhaust gas into two exhaust mufflers, so that the capacity of the expansion chamber for exhaust can be secured while maintaining the compactness of the motorcycle, and high load operation or low load can be achieved. The purpose is to make it possible to exhibit output performance and noise reduction performance suitable for each operation condition during any operation. Another object is to improve the appearance of motorcycles.

In order to solve the above problem, the invention according to claim 1 of the present application branches an exhaust pipe connected to an exhaust port of an engine into a first branch exhaust pipe and a second branch exhaust pipe via a branch pipe, In a motorcycle exhaust system in which a first exhaust muffler is connected to the first branch exhaust pipe, and a second exhaust muffler is connected to the second branch exhaust pipe, the first exhaust muffler is operated at a high load. The second exhaust muffler is an exhaust muffler suitable for low-load operation, and is arranged by displacing the branch pipe to one side in the left-right direction of the vehicle body, and the first exhaust muffler. A muffler is disposed by being displaced to the same side as the branch pipe arrangement side in the left-right direction of the vehicle body, and as an exhaust device, a valve that guides exhaust gas only to the second exhaust muffler during low-load operation is disposed , The exhaust muffler is in front The back pressure of exhaust gas is set higher than that of the first exhaust muffler, the second exhaust muffler is partitioned into a plurality of expansion chambers by an intermediate partition, and the first exhaust muffler has one overall An expansion chamber was constructed .

According to a second aspect of the present invention, an exhaust pipe connected to an exhaust port of an engine is branched into a first branch exhaust pipe and a second branch exhaust pipe via a branch pipe, and the first branch exhaust pipe is connected to the first branch exhaust pipe. In a motorcycle exhaust system in which a first exhaust muffler is connected and a second exhaust muffler is connected to the second branch exhaust pipe, the first exhaust muffler is an exhaust muffler suitable for high load operation, The second exhaust muffler is an exhaust muffler adapted for low-load operation, and the branch pipe is displaced to one side in the left-right direction of the vehicle body, and the first exhaust muffler is disposed in the left-right direction of the vehicle body. Displaced to the same side as the pipe arrangement side, and as an exhaust device, a valve for guiding exhaust gas only to the second exhaust muffler during low load operation is arranged, and each exhaust muffler is connected to the rear frame in a side view. Up and down rear wheels The exhaust pipe is arranged between the engine and the rear wheel in a side view, and is arranged at the rising portion. An exhaust pipe insertion recess is formed in a swing arm that branches into an exhaust pipe and supports the rear wheel so as to swing up and down, and the branch pipe of the exhaust pipe is disposed in the recess.

According to a third aspect of the present invention, an exhaust pipe connected to an exhaust port of an engine is branched into a first branch exhaust pipe and a second branch exhaust pipe via a branch pipe, and the first branch exhaust pipe is connected to the first branch exhaust pipe. In a motorcycle exhaust system in which a first exhaust muffler is connected and a second exhaust muffler is connected to the second branch exhaust pipe, the first exhaust muffler is an exhaust muffler suitable for high load operation, The second exhaust muffler is an exhaust muffler adapted for low-load operation, and the branch pipe is displaced to one side in the left-right direction of the vehicle body, and the first exhaust muffler is disposed in the left-right direction of the vehicle body. Displaced to the same side as the pipe arrangement side, and as an exhaust device, a valve for guiding exhaust gas only to the second exhaust muffler during low load operation is arranged, and each exhaust muffler is connected to the rear frame in a side view. Up and down rear wheels The exhaust pipe is arranged between the engine and the rear wheel in a side view, and is arranged at the rising portion. Branching into an exhaust pipe, the branch pipe was configured to branch the two branch exhaust pipes back and forth .

According to a fourth aspect of the present invention, in the exhaust device for a motorcycle according to the third aspect, the rising portion of the exhaust pipe is displaced from the vehicle width center line to one of the left and right sides and branched forward and backward. Of the second branch exhaust pipe, the rear branch exhaust pipe is connected to the exhaust muffler disposed on the displacement side of the rising portion, and the front branch exhaust pipe crosses the vehicle body in the left-right direction. And connected to the exhaust muffler disposed on the other side .

According to a fifth aspect of the present invention, an exhaust pipe connected to an exhaust port of an engine is branched into a first branch exhaust pipe and a second branch exhaust pipe via a branch pipe, and the first branch exhaust pipe is connected to the first branch exhaust pipe. In a motorcycle exhaust system in which a first exhaust muffler is connected and a second exhaust muffler is connected to the second branch exhaust pipe, the first exhaust muffler is an exhaust muffler suitable for high load operation, The second exhaust muffler is an exhaust muffler adapted for low-load operation, and the branch pipe is displaced to one side in the left-right direction of the vehicle body, and the first exhaust muffler is disposed in the left-right direction of the vehicle body. Displaced to the same side as the pipe arrangement side, and as an exhaust device, a valve for guiding exhaust gas only to the second exhaust muffler during low load operation is arranged, and each exhaust muffler is connected to the rear frame in a side view. Up and down rear wheels The exhaust pipe is arranged between the engine and the rear wheel in a side view, and is arranged at the rising portion. Branching to the exhaust pipe, the rising part of the exhaust pipe is displaced from the vehicle width center line to one of the left and right sides, and the reserve tank of the rear shock absorber that supports the swing arm is placed in an upward posture, and the rising part It was displaced to the opposite side to the displacement side .

According to a sixth aspect of the present invention, an exhaust pipe connected to an exhaust port of an engine is branched into a first branch exhaust pipe and a second branch exhaust pipe via a branch pipe, and the first branch exhaust pipe is connected to the first branch exhaust pipe. In a motorcycle exhaust system in which a first exhaust muffler is connected and a second exhaust muffler is connected to the second branch exhaust pipe, the first exhaust muffler is an exhaust muffler suitable for high load operation, The second exhaust muffler is an exhaust muffler adapted for low-load operation, and the branch pipe is displaced to one side in the left-right direction of the vehicle body, and the first exhaust muffler is disposed in the left-right direction of the vehicle body. Displaced to the same side as the pipe arrangement side, and as an exhaust device, a valve for guiding exhaust gas only to the second exhaust muffler during low load operation is arranged, and each exhaust muffler is connected to the rear frame in a side view. Up and down rear wheels The exhaust pipe is arranged between the engine and the rear wheel in a side view, and is arranged at the rising portion. The exhaust muffler branched to the exhaust pipe and disposed on the displacement side of the rising portion is the first exhaust muffler suitable for high load operation, and the exhaust muffler disposed on the side opposite to the displacement side of the rising portion is The second exhaust muffler is suitable for low load operation .

According to a seventh aspect of the present invention, an exhaust pipe connected to an exhaust port of an engine is branched into a first branch exhaust pipe and a second branch exhaust pipe via a branch pipe, and the first branch exhaust pipe is connected to the first branch exhaust pipe. In a motorcycle exhaust system in which a first exhaust muffler is connected and a second exhaust muffler is connected to the second branch exhaust pipe, the first exhaust muffler is an exhaust muffler suitable for high load operation, The second exhaust muffler is an exhaust muffler adapted for low-load operation, and the branch pipe is displaced to one side in the left-right direction of the vehicle body, and the first exhaust muffler is disposed in the left-right direction of the vehicle body. Displaced to the same side as the pipe arrangement side, and as an exhaust device, a valve for guiding exhaust gas only to the second exhaust muffler during low load operation is arranged, and each exhaust muffler is connected to the rear frame in a side view. Up and down rear wheels The exhaust pipe is arranged between the engine and the rear wheel in a side view, and is arranged at the rising portion. The rear frame that branches to the exhaust pipe and is located above the rear wheel includes a pair of left and right rail portions that extend in the front-rear direction and a plurality of cross portions that connect the rail portions. The cross part was an integrally formed product of a cast or forged product .

According to an eighth aspect of the present invention, in the exhaust device for a motorcycle according to the seventh aspect, the rail portion of the rear frame has an elongated cross section in the vertical direction, and is spaced from the upper end edge of the rail portion by a predetermined distance. The rib which protrudes to the vehicle width center side was formed in the lower position .

(1) Since one exhaust pipe is branched and connected to two exhaust mufflers, a large volume of the exhaust expansion chamber can be secured while maintaining the compactness of the vehicle.

(2) By using an exhaust device to change the flow of exhaust gas to each exhaust muffler, two exhaust mufflers can be selectively activated according to the operating conditions such as high-load operation or low-load operation. It can be utilized, and thereby the output performance and the silencing performance can be exhibited.

(3) Of the two exhaust mufflers, the first exhaust muffler is suitable for high-load operation, and the second exhaust muffler is suitable for low-load operation. When operating at low speed, low power (low load) can be achieved in urban areas, etc. on the other hand, by flowing most or all of the exhaust gas through the first exhaust muffler for high load. In this case, the silencing effect can be improved by flowing the exhaust gas only to the second exhaust muffler for low load.

(4) The exhaust pipe for each cylinder connected to the exhaust port of each cylinder of the multi-cylinder engine is once assembled into one exhaust pipe and branched from the one exhaust pipe into two exhaust mufflers. As a result, the compactness of a vehicle equipped with a multi-cylinder engine can be maintained.

(5) By providing a catalyst on the exhaust upstream side of the collecting portion where the exhaust pipes for each cylinder are gathered into one exhaust pipe, a large catalyst capacity can be secured while maintaining compactness, and the exhaust The distance between the device and the catalyst can be maintained, and the exhaust device can be protected from the heat of the hot exhaust gas.

(6) The exhaust mufflers are arranged between the rear frame and the rear wheel in the vertical direction in a side view, and are distributed to the left and right sides of the rear wheel in a plan view so that accessories such as heat insulating materials can be attached. Without being provided, the thermal influence on the rear seat can be reduced, and the space between the rear seat and the rear wheel can be effectively used for an accessory case or the like.

(7) By branching the exhaust pipe into two branch exhaust pipes at the rising part, stress concentration due to engine vibration or the like on the welded part or the like of the branch part can be avoided, and the production is simplified. Moreover, it can be smoothly divided into two flows without disturbing the flow of the exhaust gas, and the exhaust efficiency is improved.

(8) By disposing the branch portion of the exhaust pipe in the exhaust pipe insertion recess formed in the swing arm, the branch portion can be hidden from the outside, and the appearance is improved.

(9) Since the two branch exhaust pipes are branched forward and backward in the branch portion, the compactness in the width direction of the vehicle can be maintained.

(10) The rising portion of the exhaust pipe is displaced from the vehicle width center line to one side on the left and right sides, and the reserve tank of the rear shock absorber is placed in an upward posture and is displaced to the side opposite to the displacement side of the rising portion. By doing so, the heat influence of the exhaust pipe on the reserve tank can be avoided, and the shock absorbing function of the rear shock absorber can be maintained.

(11) The rising portion of the exhaust pipe is displaced from the vehicle width center line to one side on the left and right sides, the branch exhaust pipe located on the rear side is connected to the exhaust muffler on the displacement side, and the front branch exhaust pipe is By crossing the front of the wheel to the left and right other side and connecting to the exhaust muffler on the other side, the empty space around the rear wheel can be used effectively for the arrangement of exhaust pipes and branch exhaust pipes, and the vehicle compact In addition, the exhaust muffler on one side can secure a fast exhaust flow, so that the output improvement effect can be exhibited for high load operation, and the exhaust muffler on the other side has a long branch exhaust pipe length. At the same time, the speed of the exhaust flow is reduced, so that a silencing effect can be exhibited for low load operation.

(12) The exhaust muffler on the same side as the displacement side of the rising portion is a first exhaust muffler suitable for high load operation, and the opposite exhaust muffler is a second exhaust muffler suitable for low load operation. As a result, coupled with the effect described in the previous section (11), the output improvement effect at the time of high load operation by the first exhaust muffler is increased, while the noise reduction effect at the time of low load operation by the second exhaust muffler is also increased. .

(13) By making the rear frame an integral molded product of a cast or forged product, the frame can be easily manufactured.

(14) The rear frame is an integrally formed product of casting or forging, and the left and right rail portions are formed in a shape that is elongated in the vertical direction in the cross section, and at the lower position spaced from the upper end edge of the rail portion. By forming a rib projecting toward the center side, the heat receiving area for the exhaust pipe disposed below the rear seat is reduced and the thermal effect on the rear seat is reduced compared to the conventional rear frame made of pipe. be able to. Incidentally, in the conventional pipe commission structure, the heat receiving area is wide, and heat is trapped in the pipe, which is thermally disadvantageous.

(15) The rear frame is an integrally formed product of casting or forging, and the left and right rail parts are formed in a shape that is elongated in the vertical direction in the cross section, and at the lower position spaced from the upper edge of the rail part. By forming the rib projecting toward the center side, the rigidity is improved regardless of the load in the vertical direction and the load in the horizontal direction.
(16) By inserting the exhaust pipe into the exhaust pipe insertion recess formed in the swing arm and attaching a detachable recess cover (exhaust pipe cover) to the opening side of the exhaust pipe insertion recess, from the outside The exhaust pipe in the recess for inserting the exhaust pipe can be concealed to improve the appearance of the motorcycle, and the piping operation of the exhaust pipe can be easily performed with the removable concave cover removed.

[First embodiment]
(Overview of the entire motorcycle)
1 to 12 show a first embodiment of an exhaust device for a motorcycle to which the present invention is applied. 2 is a right side view of the motorcycle shown without the exhaust pipe cover of the swing arm 10. In FIG. 2, the vehicle body frame 1 includes a pair of left and right main frames 2, a swing arm bracket 4, and a rear frame. 7 is formed in a Y shape when viewed from the side. The main frame 2 extends rearwardly downward from the head pipe 3, the swing arm bracket 4 is formed in a downward projecting shape at the rear lower end portion of the main frame 2, and the rear frame 7 is formed at the rear end portion of the main frame 2. It is fixed and extends rearward. A front fork 5 is supported on the head pipe 3, a handle 6 is provided at the upper end of the front fork 5, and a front wheel 8 is supported at the lower end of the front fork 5.

  The swing arm bracket 4 supports the front end portion of the swing arm 10 so that the swing arm 10 can swing in the vertical direction. The rear wheel 11 is supported on the rear end portion of the swing arm 10, and between the front portion of the swing arm 10 and the vehicle body frame 1. The rear shock absorber 9 having a generally upright posture is interposed in a telescopic manner. On the upper side of the vehicle body frame 1, a fuel tank 12, a seat 13, and a rear seat 14 are provided in order from the front side. A parallel 4-cylinder engine 15 is mounted on the lower side of the main frame 2, for example.

  FIG. 1 is a right side view of a motorcycle. A front cowl 16, a side cowl 17, a lower cowl 18 and the like are provided at a front portion of a vehicle body, and a rear cowl (rear cover) covering a rear frame 7 is provided at a rear portion of the vehicle body. 19 etc. are provided. A pair of left and right rider steps 46 are fixed to the swing arm bracket 4 with bolts, and a pair of left and right passenger steps 47 are fixed to the rear frame 7 with bolts. Further, a heat-insulating cover 71 for foot protection is provided above the rider's step 46.

(Brake disc and vehicle speed sensor)
In FIG. 1, break discs 55 and 56 are fixed to the rear wheel 11 and the front wheel 8, respectively, and a large number of irregularities 68 are formed on the outer peripheral ends of the brake discs 55 and 56 at regular intervals in the circumferential direction. Has been. A rear wheel brake pad mechanism 59 is attached to the swing arm 10 via a bracket 58, and a front wheel brake pad mechanism 62 is attached to the front fork 5 via a bracket 61. The hydraulic oil hose 64 connected to the rear wheel brake pad mechanism 59 extends forward from the upper position of the swing arm 10 to connect to the hydraulic control device, and the hydraulic oil hose 65 connected to the front wheel brake pad mechanism 62 includes , Extending upward and connected to the hydraulic control device.

  FIG. 12 is an enlarged right side view of the rear wheel 11. A pickup sensor 69 is provided as a vehicle speed sensor on the bracket 58 of the swing arm 10 at a position corresponding to the outer peripheral unevenness 68 of the brake disc 55 for the rear wheel. The pick-up sensor 69 counts the number of passages of the unevenness 68 per unit time, thereby calculating the vehicle speed. The lead wire of the pickup sensor 69 is disposed so as to extend forward along the hydraulic oil hose 64.

(Swing arm configuration)
FIG. 6 is a plan view of the swing arm 10. The swing arm 10 includes a flat plate-like front portion 72 formed integrally with the pivot cylinder portion 10 a at the front end, and a pair of left and right extending rearward from the flat plate-like front portion 72. A recess 75 for inserting an exhaust pipe is formed at the right end of the flat plate-like front portion 72, and a recess cover (exhaust pipe cover) 76 is formed at the right opening end of the recess 75. Is detachably attached. The rear shock absorber 9 is located on the left side of the vehicle width center line C, that is, on the side opposite to the exhaust pipe insertion recess 75, and an oil reserve tank 77 provided at the upper end of the rear shock absorber 9 is Further, the rear shock absorber 9 is located on the left side and is disposed in an upward posture as shown in FIG. That is, the reserve tank 77 is arranged so as to be spaced apart from the exhaust pipe insertion recess 75 of FIG.

(Exhaust system configuration)
FIG. 3 is a rear view of the motorcycle. A pair of left and right exhaust mufflers 21 and 22 are arranged above the rear wheel 11 and rear ends of the exhaust mufflers 21 and 22 are arranged. Are respectively provided with tail pipes 21a and 22a. Both exhaust mufflers 21 and 22 are disposed between the rear wheel 11 and the rear frame 7 and supported by the rear frame 7 in a side view as shown in FIG.

  The cylinder exhaust pipes 24 are respectively connected to the front exhaust ports of the four cylinders of the engine 15, and the four cylinder exhaust pipes 24 extend downward on the front side of the engine 15 and rearward at the lower end portion. It is curved and extends rearward on the lower side of the engine 15.

  FIG. 4 is a schematic plan view of the exhaust device. A pair of left and right first collecting pipes 25 are arranged on the lower side of the engine 15, and the four pipes are disposed at the front end of each first collecting pipe 25. Two cylinder exhaust pipes 24 are connected to each other, and a catalyst pipe 26 is connected to the rear end of each first collecting pipe 25. The two catalyst pipes 26 gather in one exhaust pipe 28 via the second collecting pipe 27, and the one exhaust pipe 28 extends rearward while being displaced rightward.

  In FIG. 2, as described above, one exhaust pipe 28 that extends rearward while displacing to the right reaches the recess 75 of the swing arm 10 and rises vertically upward in the recess 75. A branch pipe (branch portion) 30 that branches the one exhaust pipe 28 into the front and rear branch exhaust pipes 31 and 32 is disposed in the recess 75, and the two branch exhaust pipes 31 branched back and forth. 32 extend substantially vertically upward through the recess 75 and are curved backward at a position below the rear frame 7.

  In FIG. 4, of the branch exhaust pipes 31 and 32 branched forward and backward, the rear branch exhaust pipe 31 extends substantially straight rearward and is connected to the front end inlet of the first exhaust muffler 21 on the right side. The exhaust pipe 32 crosses the front of the rear wheel 11 to the left and then extends rearward and is connected to the front end inlet of the second exhaust muffler 22 on the left side.

  FIG. 5 is a schematic horizontal cross-sectional view of the exhaust mufflers 21 and 22 (an enlarged VV cross-sectional view of FIG. 1). In FIG. 5, the branch exhaust pipes 31 and 32 are branched side by side by the branch pipe 30. This is an expedient expression for clearly indicating the branch state. In this embodiment, as described above, the two branch exhaust pipes 31 and 32 are arranged in the front and rear. Branch in a state.

  The volume of each exhaust muffler 21, 22 is the same, but the second exhaust muffler 22 on the left is an exhaust muffler suitable for low load operation, and a plurality of, for example, two expansion chambers 41, 42 are provided by the intermediate partition 44. The expansion chambers 41 and 42 are communicated with each other by a communication pipe 43. That is, the back pressure of the exhaust gas is increased by forming the partition wall 44. On the other hand, the first exhaust muffler 21 on the right side is an exhaust muffler suitable for high-load operation, and the entire exhaust muffler constitutes one expansion chamber. That is, the exhaust gas escapes quickly and the exhaust gas back pressure is low. A branch exhaust pipe 31 connected to the first exhaust muffler 21 for high load is provided with an on-off valve 35 as an exhaust device capable of blocking the flow of exhaust gas to the first exhaust muffler 21.

  The on-off valve 35 is, for example, a rotatable butterfly valve, and is driven by an actuator 36 such as a motor. The actuator 36 is connected to a controller 38. A load detection sensor 40 is connected to the controller 38, and the load detection sensor 40 is disposed in a fuel increasing / decreasing device such as a fuel governor or an accelerator lever, for example, and detects the fuel injection amount to inject the fuel to the controller 38. A quantity detection signal is input. The controller 38 sends a command signal to the actuator 36 to open the on-off valve 35 when the fuel injection amount is greater than or equal to a predetermined value, that is, when the load is high load operation greater than or equal to a predetermined value. When the load is less than the predetermined value, that is, when the load is low load operation less than the predetermined value, a command signal is sent to the actuator 36 to close the on-off valve 35.

  As the load detection sensor 40, a pickup sensor (vehicle speed sensor) 69 for detecting the rotational speed of the rear wheel 11 can be used as shown in FIG. That is, since the high-speed operation is usually a high load (high output) operation, the on-off valve 35 is opened, and the low-speed operation is usually a low load (low output) operation, so the on-off valve 35 is closed. It is also possible to configure as described above. Traction control is possible by detecting rear wheel slip and controlling output.

(Rear frame structure)
8 is a perspective view of the rear frame 7, and FIGS. 9 to 11 are cross-sectional views taken along the lines IX-I, XX, and XI-XI of FIG. 8, respectively. In FIG. 8, the rear frame 7 is composed of a pair of left and right rail portions 80 extending in the front-rear direction and a plurality of cross portions 81, 82, 83, 84 that integrally couple the rail portions 80. The rail portion 80 and the cross portions 81, 82, 83, 84 are an integrally molded product by casting or forging. For example, it is die-cast integrally with a pair of upper and lower molds and a slide mold that can be pulled left and right. Each rail portion 80 is formed in a sector shape in which the vertical section is elongated in the vertical direction and the front end portion 7a extends in the vertical direction. The second cross section from the front of the first cross portion 81 is the second from the front. A portion having a U-shaped cross section is formed between the two cross portions 82. A pair of front and rear passenger step mounting holes 86 are formed in the U-shaped portion, and a rear cowl mounting bracket 87 is formed. Attachment holes 88 for attaching the rear frame 7 to the main frame 2 (FIG. 2) are formed at the upper and lower ends of the sector-shaped front end 7a. On the inner surface of each rail portion 80, a rib 90 protruding inward in the vehicle width is formed long along the length direction of the rail portion 80 at a lower position spaced apart from the upper end edge of the rail portion 80. .

  The second cross portion 82 and the third cross portion 83 third from the front are formed so as to be connected integrally with the rib 90, and the rear cross portion 84 is formed in a cylindrical shape for rear seat locking. Is formed. The first cross portion 81 at the front end is formed in a gate shape, and an arch portion 91 for engaging the rear seat is integrally formed at the upper end. The third cross portion 83 is formed with a pair of left and right hooks 92 for hooking a helmet.

  In FIG. 9, a battery holding case 94 is fixed to the lower ends of the left and right rail portions 80 corresponding to the gate-shaped first cross portion 81, and the battery 95 is placed on the holding case 94.

  FIG. 10 clearly shows the shape of the upward U-shaped portion of the rail portion 80, and clearly shows the shapes of the rib 90 and the rear cowl mounting bracket portion 87.

  FIG. 11 clearly shows the U shape of the second cross portion 82 and the left and right rail portions 80 in the cross portion 82.

(Operational effects of the first embodiment)
In FIG. 4, during vehicle operation, exhaust gas discharged from the engine 15 first gathers from the four cylinder exhaust pipes 24 into the two first collecting pipes 25, and then the two second gathering pipes. Each of the pipes 27 gathers into one exhaust pipe 28 via the catalyst pipe 26, and then is separated from the one exhaust pipe 28 into two branch exhaust pipes 31 and 32 via the branch pipe 30. The exhaust gas flows to the second exhaust mufflers 21 and 22, but the flow of the exhaust gas is changed by opening and closing the on-off valve 35 depending on the load level.

  That is, in FIG. 5, when a highway or the like is operated at high speed and high output (high load), the on-off valve 35 is opened by a command from the controller 38, and the first and second exhaust mufflers 21 and 22 are opened. However, the branch exhaust pipe 31 on the first exhaust muffler 21 side is shorter than the branch exhaust pipe 32 on the second exhaust muffler 22 side, and there are few bent portions. Moreover, since the first exhaust muffler 21 has lower exhaust gas back pressure than the second exhaust muffler 22, most of the exhaust gas flows into the first exhaust muffler 21, and the first exhaust muffler 21 Is then discharged from the tail tube 21a. Therefore, the exhaust gas is quickly discharged, and a high output can be achieved.

  On the other hand, when an urban area or the like is operated at low speed and low output (low load), the on-off valve 35 is closed by a command from the controller 38, and the exhaust gas flows only to the second exhaust muffler 22 for low load. It is in a state. The branch exhaust pipe 32 on the second exhaust muffler 22 side is longer than the branch exhaust pipe 31 on the first exhaust muffler 21 side and has many bent portions, and the second exhaust muffler 22 is the first exhaust muffler. Since the back pressure of the exhaust gas is higher than 21, the high noise reduction performance can be exhibited.

(Other effects of the first embodiment)
(1) As shown in FIG. 2, the branch pipe 30 that branches into the two branch exhaust pipes 31 and 32 is disposed in the recess 75 of the swing arm 10, and a cover 76 is attached to the recess 75 as shown in FIG. If it exists, the branch pipe 30 can be hidden from the outside, and the external appearance of a vehicle improves.

(2) As shown in FIG. 2, when the branch pipe 30 is connected to the rising portion of one exhaust pipe 28 and the two branch exhaust pipes 31 and 32 are branched so as to be lined up and down, the branch pipe The stress is not concentrated on the joint portion or the like of the engine 30 due to engine vibration or the like, and the pipe can be more compactly arranged in the vehicle width direction as compared with the case where the branch pipe 30 is disposed on the lower side of the engine, for example.

(3) Displace the branch pipe 30 to the left and right sides as shown in FIG. 4, branch the two branch exhaust pipes 31 and 32 back and forth, and extend the rear branch exhaust pipe 31 rearward as it is to the right. The exhaust gas in the branch exhaust pipe 31 smoothly and quickly flows into the first exhaust muffler 21 and is connected to the first exhaust muffler 21. As an exhaust muffler for high loads, high output can be exhibited.

(4) When two catalyst pipes 26 are arranged upstream of the portion gathered in one exhaust pipe 28 as shown in FIG. 4, the capacity (catalyst area) is large in a limited space. A catalyst can be disposed, and the exhaust gas purification function can be improved while maintaining compactness. In addition, when the on-off valve (exhaust device) 35 is arranged in the branch exhaust pipe 31 downstream of the one exhaust pipe 28, the distance between the on-off valve 35 and the catalyst pipe 26 can be kept long. Thus, it is possible to reduce the thermal effect on the on-off valve 35 of the exhaust gas that has become high temperature due to the catalytic action.

(5) When the two exhaust mufflers 21 (22) are arranged in the space between the rear frame 7 and the rear wheel 11 in a side view as shown in FIG. 2, the rear frame 7 as shown in FIG. The inside can be effectively used as a space for storing the battery 95 or other tools.

(6) As shown in FIG. 8, the rear frame 7 is formed as an integral molded product by casting or forging, and in particular, when the left and right rail portions 80 are formed in a shape that is long in the vertical direction, a conventional pipe is used. Compared with the rear frame, a large space for storing small items in the rear frame 7 can be secured, and the heat receiving area for the branch exhaust pipes 30 and 31 can be reduced as shown in FIG. Can be reduced.

(7) When the left and right rail portions 80 are formed in a shape that is long in the vertical direction, and the rib 90 is formed on the inner surface of the rail portion 80, either load in the vertical direction or load in the left and right direction is affected. However, the rigidity is increased. Further, if the rib 90 is formed at a lower position at a certain interval from the upper end edge of the rail portion 80, for example, compared to the case where the rib is formed on the upper end edge of the rail portion 80, the load against the load in the left and right direction In the case of casting, the die cutting length in the vertical direction is shortened and the draft angle can be set small, so that the casting process is facilitated.

(8) As shown in FIG. 6, the rear shock absorber 9 is displaced to the side opposite to the exhaust pipe arrangement side (right side) with respect to the vehicle width center line C, and the reserve tank 77 is arranged upward. If the rear shock absorber 9 is disposed further to the left, the thermal influence of the branch exhaust pipes 31 and 32 on the oil in the reserve tank 77 can be avoided, and the shock absorption performance of the rear shock absorber 9 can be maintained. Can do.

[Second Embodiment]
The second embodiment shown in FIG. 13 has a structure in which a switching valve 50 is arranged as an exhaust device in a branch pipe 30 that branches two branch exhaust pipes 31 and 32 from one exhaust pipe 28. An actuator 36 that rotationally drives the valve 50 is connected to a controller 38, and a load detection sensor 40 is connected to the controller 38. Compared with the structure of FIG. 5, the on-off valve and the switching valve 50 are the same except that they are the same. Parts corresponding to those in FIG.

  The switching valve 50 can be switched by the actuator 36 between a state in which exhaust gas flows only to the first exhaust muffler 21 and a state in which exhaust gas flows only to the second exhaust muffler 22. According to the load detection value input from the load detection sensor 40 to the controller 38, when the fuel injection amount is less than a predetermined value, that is, during low load operation where the load is less than the predetermined value, as shown in FIG. When the exhaust gas is allowed to flow only to the exhaust muffler 22 and the fuel injection amount is greater than or equal to a predetermined value, that is, during a high load operation where the load is greater than or equal to the predetermined value, the exhaust gas is only flowed to the first exhaust muffler 21. It is supposed to change.

(Operation of the second embodiment)
In FIG. 13, when the vehicle is in operation, the exhaust gas discharged from the engine once gathers in one exhaust pipe 28 and enters the branch pipe 30 from the one exhaust pipe 28 as in FIG. 5. The flow of exhaust gas is changed depending on the load level.

  That is, when the highway or the like is operated at high speed and high load (high output), the switching valve 50 is in a state where the exhaust gas flows only to the first exhaust muffler 21 for high load. The branch exhaust pipe 31 on the exhaust muffler 21 side is shorter than the branch exhaust pipe 32 on the second exhaust muffler 22 side, and there are few bent parts, and the first exhaust muffler 21 is the second exhaust muffler 22. Since the back pressure of the exhaust gas is lower than that, the exhaust gas is quickly discharged, and a high output can be achieved.

  On the other hand, when the urban area or the like is operating at low speed and low output (low load), the switching valve 50 is in a state in which exhaust gas flows only to the second exhaust muffler 22 for low load. The branch exhaust pipe 32 on the exhaust muffler 22 side is longer than the branch exhaust pipe 31 on the first exhaust muffler 21 side, has many bent portions, and the second exhaust muffler 22 is more than the first exhaust muffler 21. However, since the back pressure of the exhaust gas is high, a high silencing performance can be demonstrated.

[Third embodiment]
In the embodiment shown in FIG. 14, on-off valves 51, 52 interlocking with each other are arranged in the branch exhaust pipes 31, 32, and actuators 36, 37 that drive the on-off valves 51, 52 are connected to the controller 38. A load detection sensor 40 is connected to the controller 38. 5 is the same as the structure of FIG. 5 except that the on-off valve is different from that of FIG. 5, and the parts corresponding to those in FIG.

  The on-off valves 51 and 52 close the on-off valve 52 of the second exhaust muffler 22 for low load almost simultaneously with the opening of the on-off valve 51 of the first exhaust muffler 21 for high load during high load operation. Exhaust gas is allowed to flow only to the first exhaust muffler 21 for high load. On the other hand, during low load operation, the first exhaust for high load is almost simultaneously with the opening and closing valve 52 of the second exhaust muffler 22 for low load opening. The on-off valve 51 of the muffler 21 is closed, so that exhaust gas flows only to the second exhaust muffler 22 for low load. The other structure is the same as the first structure in FIG. 5, and the same components are denoted by the same reference numerals.

  The operation is also substantially the same as that of the second embodiment, and will be omitted.

[Other embodiments]
(1) In each of the above embodiments, the two exhaust mufflers are distributed and arranged to the left and right. However, as in the first to fifth aspects, the arrangement of the exhaust mufflers to the left and right is not a constituent requirement. Regarding the invention, for example, it is possible to adopt a structure in which two exhaust mufflers are arranged vertically. In this case, the upper exhaust muffler with the longer exhaust passage length is the second exhaust muffler for low load, and the lower exhaust muffler with the shorter exhaust passage length is the first exhaust muffler for high load. .

(2) In each of the above-described embodiments, the exhaust pipe passing through the lower side of the engine is piped so as to approach the right side. It is also possible to apply a structure for piping. Further, it is also possible to form a structure in which a recess for exhaust pipe insertion is formed on the vehicle width center line of the swing arm or on the left side of the vehicle width center line, and the rising portion of the exhaust pipe and the branch pipe are arranged in the recess. is there.

(3) In the invention in which the rear frame is not limited to casting or forging as in the first to twelfth aspects, the present invention can be applied to a motorcycle including a rear frame made of pipe.

(4) The present invention is not limited to the structures described in the above embodiments, and various structures can be applied within the scope described in the claims.

1 is a right side view of a motorcycle according to a first embodiment of the present invention. FIG. 2 is a right side view showing the motorcycle of FIG. 1 with a cover of a swing arm removed. Fig. 2 is a rear view of the motorcycle shown in Fig. 1. It is a top view of the exhaust apparatus of FIG. FIG. 5 is a schematic horizontal cross-sectional view of the exhaust muffler of FIG. It is a top view of the swing arm of FIG. It is a rear view of the rear shock absorber of FIG. It is an expansion perspective view of the rear frame of FIG. It is IX-IX sectional drawing of FIG. It is XX sectional drawing of FIG. It is XI-XI sectional drawing of FIG. It is a right side enlarged view of the rear wheel of FIG. FIG. 6 is a horizontal sectional view of an exhaust muffler similar to that of FIG. 5 according to a second embodiment of the present invention. FIG. 6 is a schematic horizontal sectional view of an exhaust muffler similar to FIG. 5 according to a third embodiment of the present invention. It is a schematic side view of a conventional example. It is a top view of the exhaust muffler of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Body frame 2 Main frame 4 Swing arm bracket 7 Rear frame 9 Rear shock absorber 10 Swing arm 11 Rear wheel 15 Engine 21 First exhaust muffler for high load 22 Second exhaust muffler for low load 24 Cylinder exhaust pipe 25 first collecting pipe 26 catalyst pipe 27 second collecting pipe 28 one exhaust pipe 30 branch pipe 31, 32 branch exhaust pipe 35 on-off valve (an example of an exhaust device)
50 selector valve (example of exhaust device)
51, 52 On-off valve (example of exhaust device)
40 load detection sensor 75 concave portion for exhaust pipe insertion 76 concave portion cover 77 reserve tank 80 rail portion 81, 82, 83, 84 cross portion 90 rib

Claims (8)

An exhaust pipe connected to the exhaust port of the engine is branched into a first branch exhaust pipe and a second branch exhaust pipe via a branch pipe, and a first exhaust muffler is connected to the first branch exhaust pipe. In the exhaust apparatus for a motorcycle, a second exhaust muffler is connected to the second branch exhaust pipe.
The first exhaust muffler is an exhaust muffler adapted for high load operation, and the second exhaust muffler is an exhaust muffler adapted for low load operation,
The branch pipe is arranged to be displaced to one side in the left-right direction of the vehicle body, and the first exhaust muffler is arranged to be displaced to the same side as the branch pipe arrangement side in the vehicle body left-right direction,
As an exhaust device, a valve that guides exhaust gas only to the second exhaust muffler during low-load operation is arranged ,
The second exhaust muffler sets the exhaust gas back pressure higher than the first exhaust muffler,
The second exhaust muffler is partitioned into a plurality of expansion chambers by an intermediate partition,
An exhaust system for a motorcycle, wherein the first exhaust muffler forms a single expansion chamber as a whole . An exhaust pipe connected to the exhaust port of the engine is branched into a first branch exhaust pipe and a second branch exhaust pipe via a branch pipe, and a first exhaust muffler is connected to the first branch exhaust pipe. In the exhaust apparatus for a motorcycle, a second exhaust muffler is connected to the second branch exhaust pipe.
The first exhaust muffler is an exhaust muffler adapted for high load operation, and the second exhaust muffler is an exhaust muffler adapted for low load operation,
The branch pipe is arranged to be displaced to one side in the left-right direction of the vehicle body, and the first exhaust muffler is arranged to be displaced to the same side as the branch pipe arrangement side in the vehicle body left-right direction,
As an exhaust device, a valve that guides exhaust gas only to the second exhaust muffler during low-load operation is arranged,
Each exhaust muffler is arranged between the rear frame and the rear wheel in the vertical direction in a side view, and is distributed and arranged on the left and right sides of the rear wheel in a plan view.
The exhaust pipe rises upward between the engine and the rear wheel in a side view, and branches to the branch exhaust pipes at the rising portion,
An exhaust system for a motorcycle , wherein a recess for exhaust pipe insertion is formed in a swing arm that supports the rear wheel so as to swing up and down, and the branch pipe of the exhaust pipe is arranged in the recess . An exhaust pipe connected to the exhaust port of the engine is branched into a first branch exhaust pipe and a second branch exhaust pipe via a branch pipe, and a first exhaust muffler is connected to the first branch exhaust pipe. In the exhaust apparatus for a motorcycle, a second exhaust muffler is connected to the second branch exhaust pipe.
The first exhaust muffler is an exhaust muffler adapted for high load operation, and the second exhaust muffler is an exhaust muffler adapted for low load operation,
The branch pipe is arranged to be displaced to one side in the left-right direction of the vehicle body, and the first exhaust muffler is arranged to be displaced to the same side as the branch pipe arrangement side in the vehicle body left-right direction,
As an exhaust device, a valve that guides exhaust gas only to the second exhaust muffler during low-load operation is arranged,
Each exhaust muffler is arranged between the rear frame and the rear wheel in the vertical direction in a side view, and is distributed and arranged on the left and right sides of the rear wheel in a plan view.
The exhaust pipe rises upward between the engine and the rear wheel in a side view, and branches to the branch exhaust pipes at the rising portion,
The exhaust device for a motorcycle, wherein the branch pipe is configured to branch the two branch exhaust pipes back and forth . The exhaust system for a motorcycle according to claim 3,
The rising portion of the exhaust pipe is displaced from the vehicle width center line to one of the left and right sides,
Of the first and second branch exhaust pipes branched forward and backward, the branch exhaust pipe located on the rear side is connected to the exhaust muffler arranged on the displacement side of the rising portion, and the branch exhaust located on the front side An exhaust system for a motorcycle, wherein the pipe is connected to the exhaust muffler disposed on the other side across the vehicle body in the left-right direction . An exhaust pipe connected to the exhaust port of the engine is branched into a first branch exhaust pipe and a second branch exhaust pipe via a branch pipe, and a first exhaust muffler is connected to the first branch exhaust pipe. In the exhaust apparatus for a motorcycle, a second exhaust muffler is connected to the second branch exhaust pipe.
The first exhaust muffler is an exhaust muffler adapted for high load operation, and the second exhaust muffler is an exhaust muffler adapted for low load operation,
The branch pipe is arranged to be displaced to one side in the left-right direction of the vehicle body, and the first exhaust muffler is arranged to be displaced to the same side as the branch pipe arrangement side in the vehicle body left-right direction,
As an exhaust device, a valve that guides exhaust gas only to the second exhaust muffler during low-load operation is arranged,
Each exhaust muffler is arranged between the rear frame and the rear wheel in the vertical direction in a side view, and is distributed and arranged on the left and right sides of the rear wheel in a plan view.
The exhaust pipe rises upward between the engine and the rear wheel in a side view, and branches to the branch exhaust pipes at the rising portion,
The rising portion of the exhaust pipe is displaced from the vehicle width center line to one of the left and right sides,
An exhaust system for a motorcycle , wherein a reserve tank of a rear shock absorber that supports a swing arm is set in an upward posture and is displaced to a side opposite to a displacement side of the rising portion . An exhaust pipe connected to the exhaust port of the engine is branched into a first branch exhaust pipe and a second branch exhaust pipe via a branch pipe, and a first exhaust muffler is connected to the first branch exhaust pipe. In the exhaust apparatus for a motorcycle, a second exhaust muffler is connected to the second branch exhaust pipe.
The first exhaust muffler is an exhaust muffler adapted for high load operation, and the second exhaust muffler is an exhaust muffler adapted for low load operation,
The branch pipe is arranged to be displaced to one side in the left-right direction of the vehicle body, and the first exhaust muffler is arranged to be displaced to the same side as the branch pipe arrangement side in the vehicle body left-right direction,
As an exhaust device, a valve that guides exhaust gas only to the second exhaust muffler during low-load operation is arranged,
Each exhaust muffler is arranged between the rear frame and the rear wheel in the vertical direction in a side view, and is distributed and arranged on the left and right sides of the rear wheel in a plan view.
The exhaust pipe rises upward between the engine and the rear wheel in a side view, and branches to the branch exhaust pipes at the rising portion,
The exhaust muffler disposed on the displacement side of the rising portion is the first exhaust muffler suitable for high load operation,
An exhaust system for a motorcycle, wherein the exhaust muffler disposed on the opposite side of the rising portion from the displacement side is the second exhaust muffler suitable for low load operation . An exhaust pipe connected to the exhaust port of the engine is branched into a first branch exhaust pipe and a second branch exhaust pipe via a branch pipe, and a first exhaust muffler is connected to the first branch exhaust pipe. In the exhaust apparatus for a motorcycle, a second exhaust muffler is connected to the second branch exhaust pipe.
The first exhaust muffler is an exhaust muffler adapted for high load operation, and the second exhaust muffler is an exhaust muffler adapted for low load operation,
The branch pipe is arranged to be displaced to one side in the left-right direction of the vehicle body, and the first exhaust muffler is arranged to be displaced to the same side as the branch pipe arrangement side in the vehicle body left-right direction,
As an exhaust device, a valve that guides exhaust gas only to the second exhaust muffler during low-load operation is arranged,
Each exhaust muffler is arranged between the rear frame and the rear wheel in the vertical direction in a side view, and is distributed and arranged on the left and right sides of the rear wheel in a plan view.
The exhaust pipe rises upward between the engine and the rear wheel in a side view, and branches to the branch exhaust pipes at the rising portion,
The rear frame located above the rear wheel is composed of a pair of left and right rail portions extending in the front-rear direction and a plurality of cross portions connecting both rail portions, and the both rail portions and the cross portion are cast or An exhaust device for a motorcycle characterized by being an integrally formed product of a forged product . The exhaust system for a motorcycle according to claim 7,
The rail portion of the rear frame has an elongated cross section in the vertical direction, and a rib projecting toward the vehicle width center side is formed at a lower position spaced apart from the upper end edge of the rail portion. Motorcycle exhaust system to do.

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