JPH0729630B2 - 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.

(Background of the Invention) There have conventionally been small vehicles having three or four wheels with two front wheels each having an engine near the center of the vehicle body and a straddle-type driving seat 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 this exhaust expansion pipe is large and long, obstacles on the road surface are likely to hit the exhaust expansion pipe if the exhaust expansion pipe is passed from the front side of the engine to the lower part. Further, if the vehicle is passed through the side of the engine, the width of the vehicle body near the side of the engine is increased, and the driver's foot easily comes into contact with the expansion tube.

(Object of the Invention) The present invention has been made in view of such circumstances, and a two-cycle engine having two cylinders in the vehicle width direction is mounted near the center of the vehicle body, but the vehicle body near the side of the engine is mounted. It is an object of the present invention to provide an exhaust device for a person who does not have an excessive width, is free from the possibility of being damaged by a road surface obstacle and damaging the exhaust expansion pipe, and has good cooling performance of the exhaust expansion pipe.

(Construction of the Invention) According to the present invention, the object is to provide two front wheels, a two-cycle engine having two cylinders mounted in the vicinity of the center of the vehicle body and arranged in parallel in the vehicle body width direction, and disposed at the upper portion of the vehicle body. And a pair of left and right exhaust expansion pipes connected to two cylinders of the engine independently, and a pair of left and right down tubes located in front of the engine and having upper parts close to each other. Each of the exhaust expansion pipes extends obliquely downward and forward from between the both down tubes and is inserted between the front wheels so as to overlap with the front wheels in a side view, and outside of the down tubes and outside of the engine. A vehicle exhaust system, characterized in that it is arranged so as to extend rearward through the vehicle.

Since the down tubes have a narrow upper space, the expansion tubes do not bulge to the side of the vehicle body even when passing through large expansion tubes outside the upper parts of both down tubes.

(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 a front view showing an arrangement of an exhaust expansion pipe. It is a figure.

In these figures, reference numeral 10 is a frame of the vehicle body, and a pair of left and right lower tubes 12, 12 and a pair of left and right upper tubes 14, which are joined to the front and rear wheels of the lower tube 12 and are bent so as to project upward, 14, a pair of left and right seat rails 16 and 16 extending rearward from the upper rear portion of the upper tube 14, and back tubes 18 and 18
And the cross tubes 20, 2 that connect the lower tubes 12, 12.
Cross tube 2 that connects 2, 24 and both upper tubes 14, 14
6, 28, 30, 32 and a pair of left and right down tubes 34, 34 connecting the upper and lower cross tubes 22, 28 and the cross tube 26
A pair of left and right upright tubes 36 that connect the lower tube 12 to the lower tube 12.
(Only one is shown). As shown in FIG. 3, the down tubes 34, 34 have their upper portions approaching each other and their intervals are narrowed.

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, and a front wheel independent suspension device is formed by struts. 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 gives a restoring force to the lower side via 56. Wide ultra-low pressure tires (so-called balloon tires) are mounted on the front wheels 42 and the rear wheels 52.

60 is a water-cooled 2-cycle 2-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 tubes. The exhaust port of each cylinder of the engine 60 is located on the front surface of the cylinder, and is directed 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, and rise upward in front of the engine 60, and then outside the down tube 34 upper part and the engine 60 upper part. It extends to the rear through the outside.
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 expansion pipes 68, 68 are located near the outer side of the upper part of the down tube 34 in front of the engine 60, and the downstream side thereof is gradually reduced in the lateral side of the engine 60, and the upper tube. 1
It is connected to exhaust pipes 70, 70 that pass between 4 and 14 in the front-rear direction. Downstream sides of the exhaust pipes 70, 70 are connected to mufflers 72, 72. A traveling wind passage (FIGS. 2 and 3) is formed between the expansion pipes 68 and 68, in which the front of the cylinder 62 passes between the front wheels 42 and 42 and is opened toward the front as shown in FIG. Has been done.

In FIGS. 1 and 2, 74 and 74 are spark plugs attached to the upper surface of the cylinder 62, and 76 in FIG. 1 is a radiator arranged in front of the steering shaft 44. The radiator 76 is a cooling device for the engine 60. It is for cooling the liquid. 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. Reference numeral 82 is a front fender that covers the front wheels 42, 84 is a rear fender that covers the rear wheels 52, and 86 is a tank cover that covers a fuel tank (not shown).

As shown in FIG. 1, the driver puts his / her both feet on the footrests 80, 80 and sits on the driving seat 78. The exhaust expansion pipe 68 has a maximum diameter portion A located in front of the engine 60 and an upper portion of the engine 60. The diameter is reduced laterally. Since the down tubes 34, 34 are close to each other at the upper part, a large-diameter exhaust expansion pipe 68 is provided on the outer side thereof.
Even with the above arrangement, the diameter of the expansion tube 68 can be increased while reducing the amount of expansion of the expansion tube 68 in the vehicle width direction. For this reason, it becomes difficult for the driver's foot to come into contact with the expansion tube 68.

Further, since the expansion pipe 68 is opened in front of the cylinder 62 and a traveling wind passage B passing between the front wheels 42, 42 is formed, traveling wind is good near the cylinder 62 and the connection portion between the cylinder 62 and the expansion pipe 68. Therefore, the cooling performance of these is improved.

FIG. 4 is a front view showing an arrangement of expansion tubes according to another embodiment of the present invention. In this figure, the frame 10A is provided with a traveling shaft cylinder 100 at the front end, and a pair of left and right lower down tubes 34B, 34 are provided at the lower part of the upper down tube 34A extending downward from the traveling shaft cylinder 100.
The top of B is stuck. Lower down tube 34B, 34B
The upper parts of them are close to each other and gather in the upper tube 34A.

A pair of left and right exhaust expansion pipes 68A, 68A are connected to the exhaust port of the two-cylinder engine 60A. The expansion tubes 68A, 68A extend obliquely downward and forward from between the lower down tubes 34B, 34B, rise upward and extend rearward from both sides of the upper down tube 34A through the upper outer side of the engine 60A.

Therefore, in this embodiment, by arranging the large diameter portions of the expansion tubes 68A, 68A on the sides of the upper down tube 34A,
Expansion tube 68A while suppressing bulging of 68A and 68A in the vehicle width direction
The capacity can be increased.

In each of the above embodiments, the engine 60 has two cylinders, but the present invention is also applicable to the case of a V-type three-cylinder, four-cylinder two-cycle engine having two cylinders in the front cylinder, and includes such a thing.

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

Further, if a traveling wind passage for guiding traveling wind to the vicinity of the cylinder or the cylinder connection portion of the expansion pipe is provided between the two expansion pipes, the cooling performance of the engine and the expansion pipe is also improved.

(Effects of the Invention) As described above, the present invention makes the upper portions of the pair of left and right down tubes close to each other, and extends the pair of left and right exhaust expansion pipes obliquely downward and forward from between the both down tubes, and the upper portions of the down tube and the engine Since it is arranged so as to pass through the outside and extend backward, there is no risk of obstacles on the road surface hitting the exhaust expansion pipe as in the case where the exhaust expansion pipe is arranged near the lower part of the engine, and the exhaust expansion pipe is prevented by the obstacle. There is no need to worry about damaging it. Since the tops of the down tubes are close to each other,
Even if the expansion tube is arranged on the outer side of the expansion tube, the expansion amount of the expansion tube in the vehicle body width direction becomes small. Therefore, it becomes difficult for the driver's foot to touch the expansion tube, and it is possible to take a comfortable driving posture.

Further, by making the exhaust expansion pipe enter between both front wheels, the exhaust expansion pipe can be made sufficiently long, and a large-capacity expansion pipe capable of maximizing engine performance can be obtained. 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.

[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 the essential parts thereof, and FIG. 3 is a front view showing the arrangement of expansion tubes, and FIG. FIG. 6 is a front view showing the arrangement of an expansion tube according to another embodiment of the present invention. 10, 10A ... Frame, 34 ... Down tube, 34A ... Upper down tube, 34B ... Lower down tube, 60, 60A ... Engine, 62 ... Cylinder, 68, 68A ... Exhaust expansion pipe, B ... Traveling air passage.

Claims (2)

[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 vehicle width direction, and a straddle-type operating seat disposed above the vehicle body. In the vehicle, a pair of left and right down tubes located in front of the engine and having upper portions close to each other, and a pair of left and right exhaust expansion tubes independently connected to the two cylinders of the engine are provided. Is slanted downward and forward from between the both down tubes, and is viewed between the front wheels so as to overlap with the front wheels in a side view, and is arranged to extend rearward through the outer side of the upper part of each down tube and the outer side of the upper part of the engine. A vehicle exhaust system characterized by being installed. 2. A traveling wind passage is formed in front of a cylinder of the engine, the traveling wind passage being opened forward between the exhaust expansion pipes, passing through the front wheels. A vehicle exhaust system according to claim 1.