JPH02163407A - Exhaust pipe of motorcycle - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the engine faculty and secure the necessary activation temperature of a catalyst and prevent the transmission of the reaction heat of the catalyst to the driver's feet by forming a catalytic layer at the part within a front fork width in front view, in the exhaust pipe of a motorcycle in which the catalytic layer is formed inside. CONSTITUTION:The part (a) of an exhaust pipe 10 occupies a length l1 at the root part having a small diameter, and a catalytic layer 16 is formed at this part (a). Further, the part (b) occupies a length of l2 at the large diameter part after the U-turn of the exhaust pipe 10, and a catalytic layer 17 is formed also at this part. Therefore, the catalytic layers 16 and 17 are formed in the exhaust pipe 10 part in the width B of a front fork in the front view, between the front wheels and an engine. Therefore, during the traveling of a motorcycle, a front fork, front wheels, front fender, etc., which are positioned in front of the part within a range of the width B of the exhaust pipe 10 serve to shield wind, and the part is prevented from being cooled by the traveling wind, and the necessary activation temperature for the catalyst layers 16 and 17 formed at the part can be secured sufficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust pipe for a motorcycle that has a catalyst layer formed therein.

(Prior art) In motorcycles, a catalyst layer made of precious metals such as platinum and palladium is formed in the exhaust pipe as a countermeasure against exhaust gas.
This catalyst layer reduces the low concentration of Co contained in the exhaust gas.
, HC is being combusted at relatively low temperatures.

Incidentally, in order to ensure the activation temperature of the catalyst, the catalyst layer has been formed for a predetermined length from the gas inlet (mouth) of the exhaust pipe.

(Problem to be solved by the invention) However, if the catalyst layer is formed to a predetermined length from the gas inlet of the exhaust pipe as described above, the part of the exhaust pipe that is cooled by the running wind (the part of the front fork when viewed from the front) Since the catalyst layer is also formed on the exhaust pipe portion that protrudes to the side, there is a problem in that some portions of the catalyst layer do not reach the activation temperature, making it impossible to obtain an effective catalytic effect. There is also the problem that the reaction heat of the catalyst at that location hits the foot of the lighter placed on the step located behind it.

Furthermore, since the inside of the catalyst layer (the side that comes into contact with the exhaust gas flow) is made of punched metal with many small holes, if the catalyst layer is formed at the mouth of the exhaust pipe where the exhaust gas flow rate is high, There is also the problem that the exhaust gas flowing through this creates turbulent flow, which increases flow resistance and reduces engine performance.

The present invention was made in view of the problem described in L.The purpose of the present invention is to secure the necessary activation temperature of the catalyst without causing a decrease in engine performance, and to prevent the reaction heat of the catalyst from reaching the rider's feet. To provide a motorcycle exhaust pipe that can prevent this.

(Means for Solving the Problems) In order to achieve the above object, the present invention has a front wheel rotatably supported on the lower ends of two left and right front forks located at the front of the vehicle body, and an engine disposed behind the front wheels. In an exhaust pipe of a motorcycle, which is led out from the exhaust system of the engine of a motorcycle, and has a catalyst layer formed inside, the exhaust pipe is located between the front wheel and the engine and within the width of the front fork when viewed from the front. , characterized in that the catalyst layer is formed.

(Function) The part of the exhaust pipe that is within the width of the front fork when viewed from the front is
Since the front fog, front wheels, front fender, etc. in front of this act as a windshield, they are not exposed to the wind while driving, so the catalyst layer formed in these areas is not cooled by the wind and the catalyst is heated. The necessary activation temperature is ensured, and the reaction heat of the catalyst does not reach the rider's feet.

In addition, since the necessary activation temperature of the catalyst is secured as described above, the catalyst layer can be formed in areas other than the mouth of the exhaust pipe where the diameter is large and the speed of the exhaust gas flowing therethrough is slow. As a result, it is possible to reduce the flow resistance of exhaust gas and prevent deterioration of engine performance.

(Example) Embodiments of the present invention will be described below based on the accompanying drawings.

FIG. 1 is a broken sectional view of an exhaust pipe according to the present invention, FIG. 2 is a side view of a motorcycle equipped with the exhaust pipe, and FIG. 3 is a front view of the motorcycle.

First, the general structure of the motorcycle l will be explained based on FIGS. 2 and 3. In the figure, 2 is a head pipe located at the front upper part of the vehicle body, and the head pipe 2 is rotatably inserted into the head pipe 2. The upper portions of two left and right front forks 3.3 are attached to the steering shaft (not shown), and the front wheels 4 are rotatably supported at the lower portions of the front forks 3.3.

Note that the upper part of the front wheel 4 is covered by a front fender 5.

Further, a two-stroke engine 7 is mounted on two left and right down tubes 6.6 extending rearward and downward from the head pipe 2. An air cleaner 8 and a carburetor 9 are connected to the intake system of the engine 7, and an exhaust pipe IO according to the present invention is led out from the exhaust system of the engine 7.

As shown in the figure, the exhaust pipe IO exits from the front of the engine, bends approximately 90 degrees, heads toward the side of the vehicle body, and then extends further 18 degrees.
It is bent by 0" to make a U-turn, crosses the front of the engine 7 in the width direction toward the other side, and is further bent by approximately 90" to extend toward the rear of the vehicle body. In the figure, 11 is a fuel tank, 12 is a seat, 3 is a rear wheel, 14 is a rear fender, and 15 is a step provided on both sides of the vehicle body.

Here, details of the exhaust pipe 10 will be explained based on FIG. 1. In the figure, the width indicated by B is the width of the front foot 3, 3, and the exhaust pipe 10 within this width B internal part a
, catalyst layers 16 and 17 are formed in portions b, respectively. That is, the above-mentioned section a of the exhaust pipe IO occupies a portion whose length intersects with the mouth portion of the small diameter, and the catalyst layer 16 containing noble metals such as platinum and palladium is formed in this section a, and this catalyst layer The inside of 16 is held by a cylindrical punching metal 18 having a large number of small holes. Further, the above-mentioned portion occupies the large diameter portion of the exhaust pipe lO after the U-turn, and the catalyst layer 1 containing the precious metal is also present in this portion.
7 is formed, and the inner peripheral side of this catalyst fi 17 is held by a cylindrical punching metal 19.

In this way, the catalyst layers 16 and 17 are divided and formed between the front wheels 4 and the engine 7 and in the portion of the exhaust pipe 10 within the width B of the front wheels 3 and 3 when viewed from the front. Become.

While the motorcycle 1 is running, the parts of the exhaust pipe 10 within the width B of the front fender 3.3 in front view include the front forks 3, 3, the front wheel 4, and the Since the fender 5 and the like play the role of a windshield (fender), the driving wind does not hit the vehicle, and since the engine 7 is located behind this area, a kind of stagnation space is formed around this area. . Therefore, this region is not cooled by the running wind, and the required activation temperature of the catalyst layers 16, 17 formed in this region is sufficiently ensured. Further, since the step 15.15 is arranged outside the width B of the front fork 3.3, the reaction heat of the catalyst layer 16.17 does not hit the rider's feet placed on the step 15.15.

Furthermore, in this embodiment, the catalyst layer 17 is provided in the section b, where the exhaust gas flow rate is low, in addition to the section a, where the exhaust gas flows quickly. As a result, the flow loss caused by the turbulent flow of exhaust gas in the section a can be kept small, and the performance of the engine 7 can be prevented from decreasing. In addition, in part b where the exhaust gas flow velocity is small, the flow loss of the exhaust gas is a
It is sufficiently small compared to the other parts.

(Effects of the Invention) As is clear from the above description, according to the present invention, the front wheel is rotatably supported on the lower ends of the two left and right front forks located at the front of the vehicle body, and the engine is arranged behind the front wheel. In an exhaust pipe of a motorcycle, which is led out from the exhaust system of the engine of the motorcycle and has a catalyst layer formed inside, a portion located between the front wheel and the engine and within the width of the front fork when viewed from the front. , since the catalyst layer is formed, the necessary activation temperature of the catalyst can be ensured without deteriorating engine performance, and the reaction heat of the catalyst can be prevented from reaching the rider's feet. .

[Brief explanation of the drawing]

FIG. 1 is a broken sectional view of an exhaust pipe according to the present invention, FIG. 2 is a side view of a motorcycle equipped with the exhaust pipe, and FIG. 3 is a front view of the motorcycle. 1...Motorcycle, 3...Front wheel only, 7.
...engine, engineering 0...exhaust pipe, 16.17...catalyst layer, B...front fork width. Figure 1

Claims (1)

[Claims] Derived from the exhaust system of the engine of a motorcycle in which a front wheel is rotatably supported on the lower ends of two left and right front forks located at the front of the vehicle body, and an engine is disposed behind the front wheel,
A motorcycle characterized in that, in an exhaust pipe for a motorcycle having a catalyst layer formed therein, the catalyst layer is formed in a portion between the front wheel and the engine and within the width of the front fork when viewed from the front. exhaust pipe.