JP4684199B2 - Motorcycle exhaust system - Google Patents

Description

The present invention relates to an exhaust device for a motorcycle, and more particularly to a device suitable for an off-road vehicle.

It is known to arrange an exhaust catalyst in front of the engine (see Patent Document 1).
In addition, an expansion chamber that is long in the front-rear direction is divided into left and right portions along the length direction, an exhaust pipe and a catalyst are disposed therein, the inside of the expansion chamber is divided into a plurality, and the exhaust path is bent, thereby It is also known to increase the tube length (see Patent Document 2).

JP 54-65215 A Japanese Patent Laid-Open No. 2002-256861

By the way, since the exhaust system is relatively heavy, there is a case where such heavy objects are desired to be concentrated on the front part of the vehicle body. Such a demand is particularly great in an off-road motorcycle that requires a light handling operation. However, in order to obtain a high output of the engine, a sufficient exhaust pipe length is required. Moreover, if an exhaust catalyst that is a relatively large and heavy part for purifying exhaust gas is also arranged, the expansion chamber becomes large. It is not easy in terms of space to arrange such an expansion chamber in the front part of the vehicle body.
Therefore, the main purpose of the present application is to make it possible to dispose such a relatively large and heavy expansion chamber in front of the vehicle body.

In order to solve the above problems, the invention of claim 1 according to an exhaust device for a motorcycle
An engine is provided between the front wheel and the rear wheel, the engine includes a cylinder extending upward from the crankcase, and an exhaust pipe extending from the exhaust port provided above the cylinder to the front of the engine and then extending to the rear of the vehicle body. In the provided motorcycle exhaust system,
An expansion chamber is provided in a lower front portion of the engine, the exhaust pipe is inserted into the expansion chamber and curved, and a catalytic converter is connected to an exhaust downstream end of the curved portion.

Further , the exhaust pipe is inserted from the upper part of the expansion chamber and is curved in a loop shape when viewed from the front of the vehicle body.

According to a second aspect of the present invention, in the first aspect , the expansion chamber is configured by an outer wall divided into left and right sides, and the exhaust pipe housing portion including the loop-shaped curved portion on one outer wall and the loop-shaped curved surface. And a support part for the part.

  According to the first aspect of the present invention, the expansion chamber provided with the catalytic converter can be disposed in front of the engine while ensuring a sufficient length of the exhaust pipe from the exhaust port of the cylinder to the catalytic converter. It is possible to concentrate heavy objects and to obtain excellent handle operability.

Further , since the exhaust pipe is inserted from the upper part of the expansion chamber and is bent in a loop shape when viewed from the front of the vehicle body, the expansion chamber can be made compact while ensuring a necessary and sufficient exhaust pipe length.

According to the second aspect of the present invention, the exhaust pipe housing portion including the loop-shaped curved portion formed of the outer wall divided into the left and right sides and curved in a loop shape on one outer wall, and the support portion of the loop-shaped curved portion Therefore, the contents of the expansion chamber can be concentrated on one side and divided into small parts. For this reason, since it can assemble only by joining the other with respect to one which concentrated the content part beforehand and assembled, the assembly work can be made efficient.

  An embodiment will be described below with reference to the drawings. FIG. 1 is a left side view of an essential part of an off-road motorcycle according to this embodiment. This motorcycle includes a head pipe 2, a main frame 3, a center frame 4, a down frame 5 and a lower frame 6 as a front portion of a body frame 1, all of which are made of metal pipes and are entirely looped. The engine 7 is supported inside.

The main frame 3 forms a substantially straight line above the engine 7 and extends rearward in an obliquely downward direction, and is connected to the upper end portion of the center frame 4 extending rearward of the engine 7 in the vertical direction.
The down frame 5 extends obliquely downward to the front of the engine 7 and is connected to the front end of the lower frame 6 at its lower end. The lower frame 6 is bent from the lower front side of the engine 7 to the lower side of the engine 7 and extends rearward in a substantially linear shape, and is connected to the lower end of the center frame 4 at the rear end.

  The engine 7 is a water-cooled four-cycle type and includes a cylinder 8 and a crankcase 9. The cylinder 8 is provided at the front portion of the crankcase 9 in an upright state in which the cylinder axis is substantially vertical, and includes a cylinder block 10, a cylinder head 11, and a head cover 12. A fuel tank 13 is disposed above the cylinder 8 and supported on the main frame 3.

A seat 14 is disposed behind the fuel tank 13 and supported by a seat rail 15 extending rearward from the upper end of the center frame 4. Reference numeral 16 denotes a reinforcing backstay disposed below the seat rail 15. The seat rail 15 and the reinforcing back stay 16 are also made of pipe-like members and constitute the rear portion of the vehicle body frame 1.
An air cleaner 17 is supported on the seat rail 15 and the reinforcing backstay 16 and is sucked into the cylinder head 11 from the rear of the vehicle body via a throttle body 18 that forms part of the electronic fuel injection system.

  A front exhaust pipe 20 extends obliquely downward from the front of the cylinder head 11 to the front of the engine 7 and is connected to the expansion chamber 21. The expansion chamber 21 expands exhaust gas and consumes exhaust energy, so that a partial capacity of the exhaust path is enlarged to form a large capacity expansion space. In this embodiment, the side view with a built-in catalytic converter is omitted. A relatively large triangle. A rear exhaust pipe 22 extends rearward from the expansion chamber 21, extends rearward across the outer side of the center frame 4, and a rear end thereof is connected to the muffler 23. The muffler 23 is a well-known unit having an expansion chamber, and further having a silencer function provided with a catalytic converter if necessary, and is supported on the reinforcing backstay 16 below the seat 14.

A telescopic front fork 24 constituting a front suspension is supported on the head pipe 2. A front wheel 25 is supported at the lower end of the front fork 24 and is steered by a handle 26 connected to the upper end of the front fork 24.
The expansion chamber 21 is disposed in a space 27 between the front wheel 25 and the front portion of the crankcase 9. A rear end portion of the front fender 28 is located in the vicinity of the upper end portion of the expansion chamber 21.

  The center frame 4 is supported by a pivot shaft 29 so that the front end portion of the rear arm 30 is swingable, and the rear end portion of the rear arm 30 is supported by a rear wheel 31. The rear wheel 31 is chain driven by the engine 7. A rear suspension cushion unit 19 is provided between the rear arm 30 and the connecting portion of the center frame 4.

  FIG. 2 is a plan view of the main part of the front part of the vehicle body with the expansion chamber 21 as the center. The main frame 3 is provided as a pair of left and right, and extends rearward from a head pipe (not shown, see FIG. 1) located on the vehicle body center at the front end of the vehicle body frame. A pair of left and right seat rails 15 are also provided, and a muffler 23 is disposed below the right seat rail 15. A rear exhaust pipe 22 that connects the muffler 23 and the expansion chamber 21 passes through the right side of the vehicle body and further below the seat rail 15 to connect to the muffler 23. The front exhaust pipe 20, the expansion chamber 21, the rear exhaust pipe 22 and the muffler 23 constitute an exhaust system.

The front exhaust pipe 20 extends from the vicinity of the vehicle body center C toward the left side of the vehicle body and enters the inside of the expansion chamber 21 from the entrance portion 32. The entrance portion 32 is a cylindrical portion that protrudes in a square shape from the upper surface of the left end portion of the expansion chamber 21.
The expansion chamber 21 is integrally formed by combining a left chamber 33 having a substantially cylindrical shape in plan view that is long in the vehicle width direction and a right chamber 34 that is connected to the right end of the left chamber 33 and extends rearward from the left and right. It has become.

The right chamber 34 is arranged outside the main frame 3 in a plan view, and forms an inflating portion 35 in which the front side which is the upstream side of the exhaust gas is greatly inflated, and the outlet portion 36 is continuously downstream from the inflating portion 35. It protrudes in a horn shape. The outlet portion 36 is a cylindrical portion that changes from the upper portion of the inflating portion 35 toward the rear, and the front end portion of the rear exhaust pipe 22 is inserted and integrated inside the rear end portion.
The contour line of the outlet portion 36 inside the vehicle body is directed to the rear of the vehicle body at a substantially right angle to the expansion chamber 21.
A stay 37 protrudes rearward from the left chamber 33 and the right chamber 34 on the back surface of the expansion chamber 21 facing the vehicle body, and is attached to the front end portion of the lower frame 6 (FIG. 1) via a mount rubber 38.

The expansion chamber 21 is manufactured separately by dividing the left chamber 33 and the right chamber 34 into left and right parts, and is welded and integrated with a joining line 39. The joint line 39 is offset from the vehicle body center C to the right side of the vehicle body.
The left chamber 33 is also divided in the front-rear direction. That is, the left chamber 33 is welded and integrated with the front outer wall 40 and the rear outer wall 41 formed in a half-divided three-dimensional shape by press molding or the like facing each other at the joining line 42. The joining line 42 extends in the left-right direction at the center in the front-rear direction. The entrance portion 32 is also integrally formed by a joining portion of the front outer wall 40 and the rear outer wall 41.

The same applies to the right chamber 34, and the expanding portion 35 is welded and integrated at the joining line 45 with the front outer wall 43 and the rear outer wall 44 formed in the same manner facing each other. However, the exit portion 36 that extends in a substantially horizontal direction is vertically aligned, and the joining line 45 is formed on the side surface of the exit portion 36 (see FIGS. 3 and 5 ).

Hereinafter, the exhaust system will be described in detail. FIG. 3 is a perspective view of the exhaust system, and the front exhaust pipe 20 enters the interior from an entrance portion 32 that protrudes above the left chamber 33 of the expansion chamber 21. The rear exhaust pipe 22 extending rearward from the outlet portion 36 of the right chamber 34 extends rearward while bending with the front portion 22a, the intermediate portion 22b, and the rear portion 22c, and is a muffler 23 that is disposed long in the front-rear direction at the rear end. Connect to.
The front part 22a bends in the vicinity of the connection part with the outlet part 36 and bends inward of the vehicle body, the intermediate part 22b linearly extends rearward substantially parallel to the vehicle body center, and the rear part 22c opens slightly outward. It extends obliquely upward and connects to the muffler 23.

FIG. 4 is a rear view showing the exhaust system from the rear side of the vehicle body. The position of the joint portion 39 between the left chamber 33 and the right chamber 34 of the expansion chamber 21 substantially coincides with the position of the rear exhaust pipe 22.
The intermediate portion 22 b of the rear exhaust pipe 22 has a height that enters slightly below the upper end of the expansion chamber 21. The rear end positions of the flange 20a and the outlet portion 36 at the front end of the front exhaust pipe 20 are substantially the same height.
The outline of the muffler 23 inside the vehicle body substantially coincides with the outline of the intermediate portion 22 b of the rear exhaust pipe 22.
Each stay 37 is formed at the lower back of each of the left chamber 33 and the right chamber 34.

  FIG. 5 is a side view of the expansion chamber 21 and is partially broken to show the inside. In this side view, the entrance portion 32 substantially overlaps with the exit portion 36, the front exhaust pipe 20 is curved in a convex manner in the middle in the vertical direction and continues to the entrance portion 32, and the left chamber 33 is substantially elongated in the side view. It has a triangular shape. The right chamber 34 has a large capacity with the expansion portion 35 swelling forward and backward than the left chamber 33, and the outlet portion 36 extends rearward longer than the front exhaust pipe 20.

In the left chamber 33, the front exhaust pipe 20 is wound and accommodated in a loop shape, and left and right piping parts (parts visible in a cross section) are arranged at the front lower corner part and upper part, A known catalytic converter 50 for purifying exhaust gas is disposed in the corner portion, and a gap is maintained between these by a spacer 51.
In this way, when one front exhaust pipe 20 and a relatively large-diameter catalytic converter 50 are arranged at the front and rear at the bottom of the expansion chamber 21, and one front exhaust pipe 20 is arranged at the top, it is substantially triangular in side view. Since it has a shape, the space 27 between the front wheel and the front part of the crankcase 9 expands back and forth due to the influence of the down frame 5 that is arranged obliquely downward, so that it can be arranged in the space 27 with a margin. Become.

  FIG. 6 is a plan view of the expansion chamber 21 and is partially broken to show the inside. The front exhaust pipe 20 enters the left chamber 33 from the entrance 32, extends on the front bottom toward the right chamber 34, bends and folds in the inflating portion 35, and the upper portion of the chamber is near the left end of the left chamber 33 , And then folds downward again to communicate with the left end of the catalytic converter 50 that is long on the rear side of the bottom of the left chamber 33 in the left-right direction. The front exhaust pipe 20 of the left chamber 33 and the catalytic converter 50 are positioned and fixed by two spacers 51 and 52 arranged with a space in the left-right direction. This fixing is performed only on the left chamber 33 side.

  The exhaust enters the left chamber 33 from the exhaust upstream end portion of the front exhaust pipe 20 as indicated by an arrow in the drawing. The front exhaust pipe 20 is composed of a front pipe 46, an intermediate pipe 47, and a rear pipe 48. The front exhaust pipe 20 flows in the loop-shaped front exhaust pipe 20 and circulates around to ensure a sufficient exhaust pipe length. Thereafter, it enters the catalytic converter 50 to be purified, and enters the expansion portion 35 to expand. Since the expansion portion 35 has a large capacity, the exhaust energy can be sufficiently consumed. Thereafter, the air is gradually throttled at the outlet 36 and flows out to the rear exhaust pipe 22. Exhaust gas that has entered the muffler 23 from the rear exhaust pipe 22 expands again inside and further consumes exhaust energy. Further, if necessary, a catalytic converter can be provided to further purify the exhaust gas.

The expansion chamber 21 accommodates the front exhaust pipe 20 having a sufficiently long exhaust pipe length and the catalytic converter 50, and further provided with a sufficiently large expansion chamber, so that the expansion chamber 21 itself is relatively large. and then the weight of, the ratio of the weight of total exhaust system weight is high, the expansion chamber by 21 to place the space 27 (FIG. 1), many car body center of the exhaust system weight, and more particularly the head pipe 2 (FIG. 1) Concentrated arrangement in the vicinity. Further, since the catalytic converter 50 is connected to the exhaust downstream end of the front exhaust pipe 20, the exhaust can be efficiently purified at a position close to the cylinder head 11 where the exhaust becomes high temperature.

Next, the internal structure of the expansion chamber 21 will be described in more detail. FIG. 7 is a perspective view showing the expansion chamber 21 portion from the right front side of the vehicle body, and shows the internal structure except for the front outer wall of the expansion chamber 21.
The front exhaust pipe 20 enters the left chamber 33 from the entrance 32 and is wound in a loop. This loop shape is wound in a loop shape in a vertical plane in a front view as seen from the front of the vehicle body, and forms a ring shape similar to an oval track for competition. By arranging in this way, the expansion chamber 21 can be formed thin in the front-rear direction and wide in the left-right direction and the up-down direction, so that the comparison is performed in a state where a necessary and sufficient capacity is secured and a necessary and sufficient exhaust pipe length is secured. Can be efficiently arranged in a narrow space 27.

  The front exhaust pipe 20 includes a front pipe 46, an intermediate pipe 47, and a rear pipe 48. The front pipe 46 extends downward from the entrance 32 to the left side inside the left chamber 33, and in the vehicle body near the bottom of the left chamber 33. Bend in the direction and connect to the lower part of the intermediate pipe 47. The intermediate pipe 47 is substantially U-shaped, and the lower part connected to the front pipe 46 extends longer to the left side of the vehicle body. The intermediate pipe 47 is disposed so as to be substantially U-shaped in the vertical plane, and the substantially U-shaped curved portion slightly enters the expansion portion 35 of the right chamber 34. The upper part is connected to the upper end of the rear pipe 48 at the right side of the vehicle body from the lower part.

  The rear pipe 48 is bent in a substantially U shape in the opposite direction to the intermediate pipe 47, the curved portion overlaps with the front pipe 46 in the front-rear direction, and the exhaust downstream end is connected to the catalytic converter 50. The catalytic converter 50 is formed in a substantially cylindrical shape that is long in the left-right direction so as to overlap the lower portions of the front pipe 46 and the intermediate pipe 47, and by passing the exhaust gas that has entered from the rear pipe 48 into the catalytic converter 50, Purify the exhaust. The exhaust gas discharged from the catalytic converter 50 expands into the expansion portion 35 and flows upward, and travels toward the outlet portion 36.

  The lower portion of the front pipe 46 and the upper portion of the rear pipe 48 are positioned by the first spacer 51, and similarly, the upper and lower portions of the intermediate pipe 47 are positioned by the second spacer 52. The first spacer 51 and the second spacer 52 also support and position the catalytic converter 50 at the same time. The first spacer 51 and the second spacer 52 are positioned and fixed to the rear outer wall 41 side in this embodiment.

FIG. 8 is a perspective view similar to FIG. 7, but shown from the left side of the vehicle body. As is apparent from this figure, the first spacer 51 has an upper portion 53 and a lid portion 54 integrally, and a metal material or the like is formed by press molding or the like.
The upper portion 53 has a substantially trapezoidal shape that is hollowed out, and the top portion thereof forms a concave curved surface portion 53 a along the outer peripheral portion of the rear pipe 48 to support the rear pipe 48. Further, the exhaust downstream side end portion of the front pipe 46 is positioned by the lower concave curved surface portion 53b. 53c is a hollow hole.

  The lid portion 54 is a portion that fits and supports the upstream end portion of the catalytic converter 50, and the exhaust downstream end portion of the rear pipe 48 is connected to a connection hole 54 a provided in the center. In addition, a shoulder portion 54b connected to the concave curved surface portion 53b is provided on a side portion of the lid portion 54, and a part of the shoulder portion 54b is fitted into the concave curved surface portion 53b on the shoulder portion 54b. Here, the lower end portion of the front pipe 46 supports the vicinity of the connecting portion with the lower end portion of the intermediate pipe 47.

The second spacer 52 has a similar upper portion 53 and band portion 55 integrally. The upper portion 53 is the same as that of the first spacer 51. The concave curved surface portion 53a supports the vicinity of the connecting portion with the rear pipe 48 at the upper end portion of the intermediate pipe 47, and the lower portion of the intermediate pipe 47 is positioned by the concave curved surface portion 53b. (FIG. 7).
The band portion 55 is wound around the outer periphery of the exhaust downstream side end of the catalytic converter 50 so as to allow thermal expansion of the catalytic converter 50, and a part of the outer periphery is continuously integrated with the lower portion of the upper portion 53.

  Since both the first spacer 51 and the second spacer 52 are hollowed out and have a hollow 53c, the inner space 33a surrounded by the front exhaust pipe 20 in the space in the left chamber 33 is the first space 51a. The first spacer 51 and the second spacer 52 communicate with each other without being separated, and further communicate with the expanding portion 35 of the right chamber 34. Accordingly, a part of the exhaust gas that has expanded to the expansion portion 35 can also expand to the inner space 33a of the left chamber, and this inner space 33a can be used as a part of the expansion chamber, so that the capacity of the expansion chamber can be increased. Can contribute.

To assemble the expansion chamber 21, first, the front exhaust pipe 20 is assembled. At this time, positioning is performed by the first spacer 51 and the second spacer 52, and the catalytic converter 50 is supported by the first spacer 51 and the second spacer 52.
At this time, the fixing of the front exhaust pipe 20, the catalytic converter 50, and the spacer is concentrated on either one of the front outer wall 40 or the rear outer wall 41, and then the front exhaust pipe 20 is connected to the front outer wall 40 and the rear part. The left chamber 33 is sandwiched from the front and rear by the outer wall 41 and integrated after welding at the joining line 42 to integrate the left chamber 33 into a small assembly. By assembling the content portion in such a manner that the content portion is concentrated on one side of the front outer wall 40 or the rear outer wall 41, the assembly work of the left chamber 33 can be made efficient.

  Similarly, the right chamber 34 is integrated into a small assembly. At this time, the upstream side end portion of the rear exhaust pipe 22 is sandwiched between the end portions of the outlet portion 36 separated vertically, and the outlet portion 36 is faced in the vertical direction, and at the same time, the front outer wall 43 and the rear outer wall Assemble 44 by facing each other from the front and back and weld and integrate at the joining line 45.

  Thereafter, the left chamber 33 and the right chamber 34, which are respectively assembled, are combined from the left and right and welded and integrated at the joining line 39 to assemble the expansion chamber 21. In this way, the content portion can be concentrated only on the left chamber 33 side, and a part of the right side portion of the front exhaust pipe 20 only needs to be accommodated in the expansion portion 35 during assembly. Since it is not necessary to fix the front exhaust pipe 20 by welding or the like, the assembly work of the expansion chamber 21 can be made efficient.

  Next, the operation of this embodiment will be described. As shown in FIGS. 7 and 8, the expansion chamber 21 can use not only the inside of the left chamber 33 as a housing portion for the front exhaust pipe 20, but also the inside space 33a as an exhaust expansion chamber. In addition, the inside of the right chamber 34 can be used not only for the expansion portion 35 but also for the whole as an expansion chamber for exhaust. Therefore, it is easy to secure a necessary and sufficient capacity by using the expansion chamber as a large capacity.

  Moreover, the catalytic converter 50 can be accommodated using this expansion chamber. Therefore, since the weight part in the exhaust system can be concentrated in the expansion chamber 21 and disposed in the vicinity of the head pipe 2, the moment of inertia at the time of steering is reduced and the operability is excellent. It will be suitable for steering. Further, the front exhaust pipe 20 can secure a sufficient exhaust pipe length, and can be made compact by curving it in a loop shape in the vertical direction, and the expansion chamber 21 can be made thin in the front-rear direction, Since it can be formed wide in the vertical direction, it can be efficiently arranged in a relatively narrow space 27 with a sufficient exhaust pipe length secured. For this reason, the expansion chamber 21 can be disposed by effectively utilizing the conventional dead space 27 between the front wheel 25 and the crankcase 9.

  Further, the expansion chamber 21 is divided into a left and right chamber 33 and a right chamber 34, each of which is a small assembly, and the left chamber 33 is divided into a front outer wall 40 and a rear outer wall 41, and the front outer wall 40 or the rear outer wall. 41, for example, the front exhaust pipe 20 and the catalytic converter 50 are centrally supported on the rear outer wall 41 by the first spacer 51 and the second spacer 52, so that when the left chamber 33 is assembled, the centrally supported rear portion The front wall 40 is put on the outer wall 41 so as to be aligned in the front-rear direction.

  In addition, the right chamber 34 that has been assembled in advance is simply opposed to the left chamber 33 in the left-right direction to the joint line 39 with respect to the left chamber 33 that forms the small assembly in a state in which the contents are integrated. Since the expansion chamber 21 can be assembled simply by welding, the assembly operation of the expansion chamber 21 can be made efficient.

The present invention is not limited to the above-described embodiments, and various modifications and applications can be made within the principle of the invention. For example, the number of loops and the loop shape of the front exhaust pipe 20 are arbitrary, and the number of catalytic converters 50 is also arbitrary. Further, the rear exhaust pipe 22 and the muffler 23 can be omitted if the silencer function can be exhibited to a necessary and sufficient level even with the first muffler 21 alone.

Side view of main part of motorcycle according to embodiment The main part plan view Exhaust system perspective view Figure showing the exhaust system from the rear Side view of expansion chamber Top view of expansion chamber A perspective view showing the inside of the expansion chamber Perspective view showing slightly different angle from above

Explanation of symbols

1: body frame, 2: head pipe, 7: engine, 8: cylinder, 9: crankcase, 20: front exhaust pipe, 21: expansion chamber, 22: rear exhaust pipe, 23: muffler, 25: front wheel, 27 : Space, 32: Entrance part, 33: Left ventricle, 34: Right ventricle, 35: Expansion part, 36: Outlet part, 39: Joining line, 50: Catalytic converter, 51: First spacer, 52: Second spacer

Claims (2)

An engine (7) between the front and rear wheels, the engine (7) comprises a cylinder (8) extending upward from the crankcase (9), an engine from an exhaust port provided above the cylinder (8) In the exhaust system for a motorcycle provided with an exhaust pipe extending downward from the front of (7) to the rear of the vehicle body,
An expansion chamber (21) is provided in the lower front portion of the engine (7), the exhaust pipe is inserted into the interior from the upper portion of the expansion chamber (21) , and is bent in a loop when viewed from the front of the vehicle body .
An exhaust device for a motorcycle, wherein a catalytic converter (50) is connected to an exhaust downstream end of the curved portion. The expansion chamber (21) is composed of outer walls (40, 41, 43, and 44) divided into left and right, and includes the loop-shaped curved portion that is curved in the loop shape on one outer wall (41). The exhaust device for a motorcycle according to claim 1 , further comprising a tube housing portion and a support portion ( 51, 52) for the loop-shaped curved portion.

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