JP2813193B2 - Exhaust system for motorcycle - Google Patents

Description

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

(Prior Art) In an engine mounted on a vehicle such as a motorcycle, an exhaust pulsation effect is used as one means for improving the output. However, a pressure wave propagates in the exhaust pipe at a sonic speed, and the sonic speed is in the exhaust pipe. (Specifically, proportional to the square root of the absolute temperature), the temperature in the exhaust pipe is one of the important parameters in adjusting the output of the engine.

By the way, in the conventional exhaust device, the exhaust pipe is directly exposed to the atmosphere, and has not been covered.

(Problems to be Solved by the Invention) Therefore, in the conventional exhaust system, the exhaust pipe is a heat transfer surface, and the exhaust gas flowing through the exhaust pipe is cooled by the traveling wind. It depends on overall favorable conditions, and depending on running conditions, mismatching occurs in the output characteristics of the engine. For example, when the exhaust pipe length and the like are set so that an effective exhaust pulsation effect is obtained when the motorcycle runs under standard atmospheric conditions (for example, an atmospheric condition at a temperature of 20 ° C.), the standard atmospheric conditions and When a motorcycle is run in a cold region or a tropical region, which is significantly different, an effective exhaust pulsation effect cannot be obtained, and a mismatch occurs in the output characteristics of the engine.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a motorcycle exhaust device capable of always obtaining a constant engine output characteristic regardless of the running conditions of the motorcycle. Is to do.

(Means for Solving the Problems) In order to achieve the above object, the present invention relates to an exhaust system for a motorcycle including an exhaust pipe extending from the engine cylinder to the rear of the vehicle body through the inside of the fairing. A heat insulating material is adhered to the inside of a cover material made of aluminum, and the heat insulating cover formed in an arc shape in advance is spread, and this is fitted along the outer peripheral surface of the exhaust pipe from the outside of the vehicle body to fit the outer peripheral surface of the exhaust pipe. The exhaust pipe is covered with a heat insulating cover to cover an angle range greater than the central angle 180 ° of the outer peripheral surface including at least the outer side surface of the vehicle body with a heat insulating cover, and a cutout portion is formed in the heat insulating cover. A stay is sandwiched between heat insulating materials, and the stay is fastened together with a bracket attached to the uppermost surface of the exhaust pipe to a fastening member on the vehicle body with a bolt. A gap in the vehicle longitudinal direction is formed between the pipe and the bracket.

(Operation) According to the present invention, since the exhaust pipe is covered with the heat insulating cover, the exhaust gas flowing in the exhaust pipe is not cooled by the traveling wind, and the temperature in the exhaust pipe is kept substantially constant irrespective of the traveling conditions of the motorcycle. Therefore, the output characteristics of the engine are not mismatched depending on the running conditions of the motorcycle, and an effective exhaust pulsation effect is always obtained.

In addition, the heat insulating cover can be easily attached to the exhaust pipe simply by expanding the heat insulating cover formed in an arc shape in advance and fitting it along the outer peripheral surface of the exhaust pipe from outside the vehicle body. Since the heat insulating cover is attached to the fastening member on the vehicle body together with the exhaust pipe by co-fastening, the heat insulating cover does not move in the front-rear direction of the vehicle body due to the vibration of the exhaust pipe, and does not rotate in the circumferential direction along the outer peripheral surface of the exhaust pipe.

Further, since a gap in the longitudinal direction of the vehicle body is formed between the front and rear edges of the notch formed in the heat insulating cover and the bracket of the exhaust pipe, a dimensional error in the longitudinal direction of the vehicle body due to a difference in thermal expansion between the heat insulating cover and the exhaust pipe. Can be absorbed by the gap,
Positioning at the time of attaching the heat insulating cover can be easily performed.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

1 is a schematic side view of a motorcycle provided with an exhaust device according to the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a sectional view taken along line III-III of FIG. .

A two-stroke engine (not shown) is mounted on a portion behind the front wheel 2 of the motorcycle 1 shown in FIG. 1, and an exhaust pipe 3 extends from the cylinder of the engine toward the rear of the vehicle body through the inside of the fairing 4. And extends obliquely upward, and a silencer 5 is connected to a rear portion thereof.

The exhaust pipe 3 has an intermediate portion supported by a footrest bracket 7 via a stay 6. The central angle θ as shown in FIG.
(> 180 ゜). As shown in FIG. 1, the front end of the heat insulating cover 8 overlaps with the fairing 4 in a side view, and the front end is located inside the fairing 4.

As shown in FIG. 3, the heat-insulating cover 8 has a heat-insulating material 8b made of asbestos cloth or the like having a high heat resistance inside a cover material 8a made of carbon fiber reinforced plastic (CFRP).
The cross section of the exhaust pipe 3 is previously formed in an arc shape so as to be in close contact with the outer periphery of the exhaust pipe 3, and a cutout 8c (see FIG. 2) formed in a part thereof has metal. Made stay
8d is sandwiched and attached between the cover material 8a and the heat insulating material 8b.

By the way, as shown in FIG. 2 and FIG.
The exhaust pipe 3 and the heat insulating cover 8 are attached to the stay 6 by fastening together with bolts 10 inserted into the bracket 9 and the stay 8d. Supported by the footrest bracket 7. As shown in FIG. 2, the notch 8c is formed in a part of the heat insulating cover 8 in order to avoid interference between the stay 8d and the bracket 9 and the heat insulating cover 8. 6, a predetermined gap is formed in the vehicle longitudinal direction. Also, as shown in FIG. 3, the rear side of the exhaust pipe 3 is covered by a rear arm 11.

Since the heat insulating cover 8 is previously formed in an arc shape corresponding to the outer peripheral shape of the exhaust pipe 3 as described above, when the heat insulating cover 8 is attached to the exhaust pipe 3, the heat insulating cover 8 is formed.
Is slightly expanded and fitted along the outer peripheral surface of the exhaust pipe 3 from the outside of the vehicle body, the heat insulating cover 8 is held by the exhaust pipe 3 in close contact with the outer peripheral surface of the exhaust pipe 3 due to its elasticity. Finally, when the bolt 10 inserted into the stay 8d is tightened, the heat insulating cover 8 is supported by the footrest bracket 7 via the stay 6 together with the exhaust pipe 3.

In the motorcycle 1 shown in FIG. 1, 12 is a main frame, 13 is a fuel tank, 14 is a seat, and 15 is a rear wheel.

In the above, in this embodiment, since the outer peripheral surface of the exhaust pipe 3 except the inner side surface of the vehicle body is covered with the heat insulating cover 8, the outer peripheral surface of the exhaust pipe 3 does not function as a heat transfer surface. No heat is exchanged between the flowing exhaust gas and the atmosphere. That is, the exhaust gas flowing in the exhaust pipe 3 is not cooled by the traveling wind, and the temperature in the exhaust pipe 3 is kept substantially constant irrespective of the traveling conditions of the motorcycle 1.
Accordingly, if the conditions such as the length of the exhaust pipe 3 are set so that an effective exhaust pulsation effect can be obtained with the heat insulating cover 8 attached, the motorcycle 1 can be operated under any conditions such as a cold region or a tropical region. Even so, an effective exhaust pulsation effect is always obtained,
No mismatch occurs in the output characteristics of the engine.

Further, the heat insulating cover 8 can be easily mounted on the exhaust pipe 3 simply by expanding the heat insulating cover 8 previously formed into an arc shape and fitting it along the outer peripheral surface of the exhaust pipe 3 from outside the vehicle body. The heat insulating cover 8 and the exhaust pipe 3 together with the stay 6 on the vehicle body side.
The heat insulating cover 8
Moves in the longitudinal direction of the vehicle due to the vibration of the exhaust pipe 3,
It does not turn in the circumferential direction along the outer peripheral surface of the exhaust pipe 3.

Further, since a gap in the front-rear direction of the vehicle body is formed between the notch 8c formed in the heat-insulating cover 8 and the stay 6 on the vehicle body side, a dimensional error in the front-rear direction is absorbed by the gap, and Can be easily adjusted.

In addition, in the present embodiment, the front end of the heat insulating cover 8 is overlapped with the fairing 4 in a side view, so that the traveling wind is prevented from entering the heat insulating cover 8 and the exhaust gas is cooled by the traveling wind. The effect is further reliably suppressed, and the above effect is further enhanced.

In this embodiment, the exhaust device provided in the two-cycle engine has been particularly described. However, the present invention naturally includes the exhaust device provided in the four-cycle engine.

(Effects of the Invention) As is apparent from the above description, according to the present invention, in a motorcycle exhaust device including an exhaust pipe extending from the engine cylinder to the rear of the vehicle body through the inside of the fairing, a fiber-reinforced plastic is provided. A heat insulating material is adhered to the inside of a cover material made of aluminum, and the heat insulating cover formed in a circular arc shape is spread, and this is fitted along the outer peripheral surface of the exhaust pipe from the outside of the vehicle body to fit the outer peripheral surface of the exhaust pipe. The exhaust pipe is covered with a heat insulating cover to cover an angle range greater than the central angle 180 ° of the outer peripheral surface including at least the outer side surface of the vehicle body with a heat insulating cover, and a cutout portion is formed in the heat insulating cover. A stay is sandwiched between heat insulating materials, and the stay is jointly fastened to a fastening member on the vehicle body side with a bolt together with a bracket attached to the uppermost surface of the exhaust pipe. A gap in the longitudinal direction of the vehicle body is formed between the bracket and the bracket, so that the temperature in the exhaust pipe is kept substantially constant regardless of the running conditions of the motorcycle, and a constant engine output characteristic is always obtained, and the engine output characteristic is mismatched. Is obtained.

Further, since a gap in the longitudinal direction of the vehicle body is formed between the front and rear edges of the notch formed in the heat insulating cover and the bracket of the exhaust pipe, a dimensional error in the longitudinal direction of the vehicle body due to a difference in thermal expansion between the heat insulating cover and the exhaust pipe. Can be absorbed by the gap, so that the positioning can be easily performed when the heat insulating cover is attached.

[Brief description of the drawings]

1 is a schematic side view of a motorcycle provided with an exhaust device according to the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a sectional view taken along line III-III of FIG. . 1 ... motorcycle, 3 ... exhaust pipe, 4 ... fairing, 6 ... stay (fastening member), 8 ... heat insulating cover, 8a
... cover material, 8b ... heat insulation material, 8c ... notch, 8d ... stay, 9 ... bracket, 10 ... bolt.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-83483 (JP, A) JP-A 62-36973 (JP, U) JP-A 60-52337 (JP, U) JP-A 2-83 121393 (JP, U) Japanese Utility Model Showa 64-56375 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01N 7/08 F01N 7/14

Claims (1)

(57) [Claims] An exhaust system for a motorcycle having an exhaust pipe extending from the engine cylinder to the rear of the vehicle body through the inside of the fairing, wherein a heat insulating material is attached to the inside of a fiber-reinforced plastic cover material in advance. Expanding the arc-shaped heat insulating cover, fitting it along the outer peripheral surface of the exhaust pipe from the outside of the vehicle body, and closely adhering to the outer peripheral surface of the exhaust pipe, the outer peripheral surface of the exhaust pipe including at least the outer side surface of the vehicle body Covering an angle range larger than 180 ° of the central angle with a heat insulating cover, forming a notch in the heat insulating cover,
A stay is sandwiched between the cover material and the heat insulating material at the periphery of the notch, and the stay is jointly fastened to a vehicle body side fastening member with a bolt together with a bracket attached to the uppermost surface of the exhaust pipe, An exhaust device for a motorcycle, wherein a gap in the vehicle longitudinal direction is formed between a front and rear edge of a notch and a bracket of an exhaust pipe.