JPH0729631B2 - Vehicle exhaust system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention mounts a two-cycle engine having two cylinders arranged side by side in the vehicle width direction in the vicinity of the center of a vehicle body, and has a straddle-type operation seat above the vehicle body. The present invention relates to an exhaust device for a small vehicle having three or four wheels with two front wheels provided with a.

(Background of the Invention) There have conventionally been small vehicles having three or four wheels with front wheels in which an engine is arranged near the center of the vehicle body and a straddle-type driving seat is arranged above the vehicle body. In this type of vehicle, when the engine is a two-cycle engine in which two cylinders are arranged side by side in the vehicle width direction, it is necessary to independently provide an exhaust expansion pipe for each cylinder in order to improve engine performance. . Since the diameter of the exhaust expansion pipe is large and long, obstacles on the road surface are likely to hit the exhaust expansion pipe when the exhaust expansion pipe is passed from the front of the engine to a lower position on the lower side or both sides of the engine. Further, if the engine is passed through both sides of the upper part of the engine, both sides of the upper part of the engine are blocked by the left and right exhaust expansion pipes, which makes it difficult to attach and remove the spark plug on the upper surface of the cylinder.

(Object of the Invention) The present invention has been made in view of such circumstances,
Although the two-cycle engine having two cylinders in the width direction of the vehicle body is mounted near the center of the vehicle body, there is no risk of the exhaust expansion pipe being damaged by an obstacle on the road surface, and the cooling performance of the exhaust expansion pipe is good. It is an object of the present invention to provide an exhaust system for a vehicle, which has good workability for attaching and detaching a spark plug on the upper surface.

(Structure of the Invention) According to the present invention, the object is to have two front wheels and spark plugs that are attached to and detached from both sides of the vehicle body in two cylinders mounted near the center of the vehicle body and arranged in parallel in the vehicle body width direction. In a vehicle including a cycle engine and a straddle-type driving seat arranged on an upper part of a vehicle body, a front side of the engine is inserted between both front wheels so as to overlap with the both front wheels in a side view, and a rear side is passed through an upper side of the engine. A pair of left and right exhaust expansion pipes extending to each other are provided, the maximum diameter portions of these exhaust expansion pipes are located in front of the engine, and the upper edge of the exhaust expansion pipe is near the upper surface of the cylinder behind at least the spark plug at the upper part of the engine. And a pair of left and right spark plug attachment / detachment spaces which are located above the exhaust expansion pipe and open toward the outer side of the vehicle body.

(Embodiment) FIG. 1 is a side view of a four-wheeled vehicle for traveling on rough terrain, which is an embodiment of the present invention, FIG. 2 is a plan view of a main portion thereof, and FIG. 3 is an expansion pipe in FIG. FIG. 3 is a front view showing a cross section taken along line III-III.

In these drawings, reference numeral 10 denotes a body frame, which is a pair of left and right lower tubes 12, 12 and a pair of left and right upper tubes which are connected to the front and rear ends of the lower tube 12 and are bent so as to be convex upward.
14,14, a pair of left and right seat rails 16,16 extending rearward from the upper rear portion of the upper tube 14, and back tubes 18,18,
Cross tube 20,22,24 connecting both lower tubes 12,12
And cross tubes 26,28,3 that connect both upper tubes 14,14
0, 32, a pair of left and right down tubes 34, 34 connecting the upper and lower cross tubes 22, 28, and a pair of left and right upright tubes 36 (only one shown) connecting the cross tube 26 and the lower tube 12. As shown in FIG. 3, the down tubes 34, 34 have a narrow gap at the upper portion.

38 is a pair of left and right front shock absorbers (only one is shown), the upper end of which is supported by the upper tube 14, and the lower end of which is the lower arm.
It is held vertically by 40. A pair of left and right front wheels 42 (only one of which is shown) is steerably attached to the lower end of each shock absorber 38 to form a strut-type front wheel independent suspension device. Reference numeral 44 is a steering shaft, and 46 is a steering bar handle.

48 is a rear arm, the front end of which is pivotally attached to the body frame 10 so as to be vertically swingable, and rear wheels 52 (only one of which is shown) are fixed to the left and right ends of a rear wheel shaft 50 which is rotatably held at the rear end thereof. Has been done. This rear arm 48 has a link 54,
A rear shock absorber 58 provides a downward restoring force via 56. Wide ultra-low pressure tires (so-called balloon tires) are mounted on the front wheels 42 and the rear wheels 52.

The 60 is a water-operated two-cycle two-cylinder engine mounted near the center of the vehicle body. The engine 60 includes two cylinders arranged side by side in the vehicle body width direction, and a cylinder 62 including each cylinder stands obliquely upward and forward from a crankcase 64. On the rear surface of the cylinder 62, two carburetors 66, 66 are arranged side by side in the vehicle width direction.

68 and 68 are a pair of left and right exhaust expansion pipes. The exhaust port of each cylinder of the engine 60 is located on the front surface of the cylinder, and is open obliquely downward and forward from between the left and right down tubes 34, 34. The expansion pipes 68, 68 are connected to these exhaust ports, extend obliquely downward and forward from between the down tubes 34, 34, rise upward in front of the engine 60, and then pass rearward through the upper side of the engine 60. . As is apparent from FIG. 1, the exhaust expansion pipes 68, 68 enter between the front wheels 42, 42 and overlap with the front wheels 42, 42 in a side view to secure a sufficient length. There is. Here, the maximum diameter portions A, A of both the expansion pipes 68, 68 are located in front of the engine 60, and the downstream side thereof is gradually reduced in diameter laterally of the engine 60, so that the space between the upper tubes 14, 14 extends in the front-rear direction. It is connected to the exhaust pipes 70, 70 passing through. Downstream sides of the exhaust pipes 70, 70 are connected to mufflers 72, 72.

In FIGS. 1 and 2, 74 and 74 are spark plugs attached to the upper surface of the cylinder 62. As is apparent from FIG. 1, the expansion tubes 68, 68 are located behind the spark plugs 74, 74.
The upper edge of the cylinder 62 is located below the upper surface of the cylinder 62. Further, the upper tube 14 has a sufficiently large gap with the upper surface of the cylinder 62. As a result, spark plug attachment / detachment spaces B, B that open toward the left and right outer sides of the vehicle body are formed at least above the spark plug 74 in the upper portion of the engine 60.

In FIG. 1, reference numeral 76 denotes a radiator disposed in front of the steering shaft 44, and the radiator 76 cools the cooling fluid of the engine 60. Reference numeral 78 denotes a straddle-type operation seat that is long in the front-rear direction, and is located above the vehicle body, that is, from above the seat rail 16 to above the rear portion of the upper tube 14. Reference numerals 80, 80 denote a pair of left and right footrests, which are fixed to the lower tubes 12, 12 so as to be located below the engine 60. Also 82 is the front wheel 42
Is a front fender that covers the rear wheel 52, 84 is a rear fender that covers the rear wheel 52, and 86 is a tank cover that covers a fuel tank (not shown).

As shown in FIG. 1, the driver places both feet on the footrests 80, 80 and sits on the driver's seat 78. Maximum diameter A of exhaust expansion pipe 68
Is located in front of the engine 60 and has a reduced diameter on the upper side of the engine 60. Therefore, the maximum diameter portion A is largely separated from the driver's foot, and the lateral projection amount of the expansion pipe 68 on the side of the engine 60 is also small.

Further, since the exhaust expansion pipes 68, 68 are located below the upper surface of the cylinder 62 behind the spark plug 74, and form a pair of left and right spark plug attachment / detachment spaces B, B that open to the outside of the vehicle body on the upper side of the cylinder 62. The spark plugs 74, 74 can be attached and detached by inserting a tool such as a wrench from the spaces B, B.

In the present embodiment, the engine 60 has two cylinders, but the present invention can be applied to the case of a V-type three or four cylinder two-cycle engine having two cylinders in the front cylinder, and includes such one.

In addition, the exhaust expansion pipe can be greatly expanded forward from the engine so as to be located between the front wheels by utilizing the space between the two front wheels 42, 42, and the expansion pipe has a large volume capable of maximizing the engine performance. It becomes possible.

(Effects of the Invention) As described above, according to the present invention, the pair of left and right exhaust expansion pipes are arranged so as to extend from the front of the engine to the rear through the upper side of the engine. There is no risk that an obstacle on the road surface will hit the exhaust expansion pipe as in the case of disposing, and there is no concern that the exhaust expansion pipe will be damaged by the obstacle.

In addition, by inserting the exhaust expansion pipe between both front wheels,
A pair of left and right spark plug attachment / detachment spaces where the maximum diameter part is located in front of the engine and the diameter is reduced at least behind the spark plug to position the upper edge of the exhaust expansion pipe near the top surface of the cylinder and open to the outside of the vehicle. Can be formed. Therefore, the workability of attaching and detaching the spark plug is improved. Further, since the exhaust expansion pipe is made to enter between the left and right front wheels, it can be made sufficiently long and can be a large-capacity expansion pipe that can maximize engine performance. Furthermore, it is possible to improve the cooling performance of the exhaust expansion pipe by guiding the traveling wind to the exhaust expansion pipe by utilizing the space between the front wheels. Also, since the upper edge of the exhaust expansion pipe is located near the upper surface of the cylinder behind the spark plug and the spark plug attachment / detachment space that opens to the outside of the vehicle body is formed on the left and right, the workability of attaching / detaching the spark plug is also improved. Become.

[Brief description of drawings]

FIG. 1 is a side view of a four-wheeled vehicle for traveling on rough terrain, which is an embodiment of the present invention, FIG. 2 is a plan view of a main portion thereof, and FIG. 3 is an expansion tube taken along line III-III in FIG. It is a front view which shows a cross section and its arrangement. 60 ... Engine, 62 ... Cylinder, 68 ... Exhaust expansion pipe, 74 ... Spark plug, 78 ... Straddle-type operation seat, B ... Ignition wire attachment / detachment space.

Claims (1)

[Claims] 1. A two-cycle engine having two front wheels, two cylinders mounted in the vicinity of the center of the vehicle body and arranged side by side in the width direction of the vehicle body, each having a spark plug attached to and detached from both sides of the vehicle body, and disposed on the upper portion of the vehicle body. In a vehicle provided with a straddle-type operation seat that has been set, a pair of left and right exhaust expansion pipes that enter from between the front wheels of the engine in a side view and overlap with the front wheels and extend rearward through the upper side of the engine. The exhaust expansion pipe has a maximum diameter portion located in front of the engine, and an upper edge of the exhaust expansion pipe is located near a cylinder upper surface at least behind the spark plug in the upper portion of the engine. An exhaust system for a vehicle, characterized in that a pair of left and right spark plug attachment / detachment spaces that open upward toward the outside of the vehicle body are formed.