JP2652882B2 - Exhaust pipe of two-cycle engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust pipe of a two-stroke engine.

2. Description of the Related Art In a two-stroke engine, a pressure wave in exhaust gas is reflected to an exhaust port side of an engine in an exhaust pipe, and a positive or negative reflected wave reaches an exhaust port at an appropriate time to prevent blow-by of fresh air. Alternatively, the engine output is improved by assisting the extraction of combustion gas. For example, 47
In an exhaust pipe of a two-stroke engine disclosed in Japanese Patent No. 22045, a control pipe (sliding cylinder) for reflecting a pressure wave is provided inside a muffler cylinder. When the engine is running at high speed, the effective length from the exhaust port is shortened to shorten the effective length of the reflected wave to the exhaust port, and when the engine is running at low speed, it is retracted to increase the effective length from the exhaust port to increase the effective time of the reflected wave from the exhaust port. I try to delay it. For this reason, the sliding cylinder is suspended by an operating rod protruding outward from a split groove formed in the muffler cylinder. Moves in the axial direction. However, since the exhaust gas leaks to the outside through the split groove, the split groove is provided with a cover that covers the split groove in order to prevent this.

In order to move the control pipe in the exhaust pipe as described above, a hole must be provided in the exhaust pipe through which the operating member penetrates, and therefore, means for sealing this hole is required. By the way, if the operating member penetrating the exhaust pipe is used as the rotating shaft, the above-mentioned seal is hardly needed. In this case, the rotation shaft and the control pipe may be connected by a swing arm inside the exhaust pipe. However, if the swing arm is disposed outside the control pipe, a space between the control pipe outer surface and the exhaust pipe inner surface may be obtained. Requires more space, and the outer diameter of the exhaust pipe becomes larger. Therefore, it is desirable to dispose the swing arm inside the control pipe. However, on the other hand, a notch groove for passing the swing arm must be provided in the control pipe, and this notch groove is relatively long so as not to hinder the swing movement of the swing arm. Although this notch groove has nothing to do with the leakage of exhaust gas from the exhaust pipe, the exhaust gas escapes through the groove to the outside of the control pipe, so that the pressure control function of the control pipe is reduced and the effect of improving the engine output is reduced. .

Therefore, the present invention is to reduce the length of the notch groove for passing the swing arm provided in the control pipe as described above as much as possible to prevent a decrease in the engine output improving effect. .

Means and Action for Solving the Problems For this reason, in the present invention, a two-cycle in which a frusto-conical pressure wave control tube having a large-diameter opening and a small-diameter opening at both ends is incorporated so as to be movable in the axial direction. An exhaust pipe of the engine, the swing arm having one end pivotally connected to the control pipe inside the control pipe and the other end connected to a support shaft provided outside the control pipe; The control tube is moved in the axial direction by swinging about a support shaft, wherein the axial position of the support shaft is set at an intermediate portion of a movement range of the control tube, and the swing is performed. An arm is connected to the control pipe near the large-diameter open end, and the swinging arm is connected to the control pipe at the one end of the moving range so that the peripheral wall of the control pipe is enlarged. Near the open end of the diameter After being penetrated from the inside to the outside in the radial direction, it is bent to form a crank-shaped bent shape facing the support shaft.

According to the present invention, at the large-diameter opening end side of the peripheral wall of the control pipe, the control pipe has one end position of its moving range, that is, the position where the large-diameter opening opens toward the opposite side to the support shaft. If a notch groove is provided to allow the swing arm to pass through when the control pipe moves to the other end position due to the swing of the swing arm, the swing arm will move relative to the control pipe. It moves in the direction of exiting forward from the notch groove, and eventually escapes completely from the notch groove and extends into the control pipe through the large-diameter opening of the control pipe, so that the length of the notch groove is reduced. There is no need to increase the length in anticipation of the swinging motion of the swinging arm, and therefore, the provision of the cutout groove hardly reduces the output of the engine. In addition, since the support shaft supporting the swing arm is located in the middle of the movement range of the control tube in the axial direction, a long movement length of the control tube can be secured with a short swing arm.

FIG. 1 is an external view of an exhaust pipe of a two-stroke engine for a motorcycle according to an embodiment of the present invention. The exhaust pipe 1 is connected to an exhaust port of a two-cycle engine mounted on a motorcycle at a connection portion 2 at a front end. After being curved from the connecting portion 2 as shown in the drawing, the lower portion of the vehicle body extends rearward, and an expanding portion 3 having a gradually increasing diameter is formed behind the curved portion. The rear of the expansion section 3 is tapered, and a rear exhaust pipe 4 having a small diameter is connected to the rear end. The rear exhaust pipe 4 extends rearward upward along the side of the vehicle body, and has a rear end opening toward the rear of the vehicle body. The inflatable portion 3 includes a front inflatable portion 3a and a rear inflatable portion 3b.
In each of 3a and 3b, each half-tubular body divided into right and left is joined to each other via a flange 5 to form a tubular shape.

FIG. 2 is an enlarged cross-sectional view of the expansion section 3. As shown in the figure, a control tube, that is, a reflection tube 6 is provided inside the rear inflation portion 3b. The reflecting tube 6 is a conical tube that converges backward, and when the exhaust gas passes through the reflecting tube 6, the pressure wave is reflected toward the upstream side, and the reflected wave reaches the exhaust port of the engine at an appropriate time. By doing so, the output of the engine is improved as described above. Therefore, in order to match the arrival time of the reflected wave and the opening / closing timing of the exhaust port, the reflecting tube 6 can be moved back and forth. That is, the reflection tube 6 occupies a front position shown by a solid line in the figure when the engine rotates at a high speed, and occupies a rear position as shown by a broken line when the engine rotates at a low speed.

For this reason, as shown in FIG. 3, a shaft 7 is installed across the inside of the reflecting tube 6 at a lower portion near the front end face of the reflecting tube 6, and the shaft 7 is attached to the lower end of the swing arm 8. The fixed sleeve 9 is rotatably fitted. The swing arm 8 is
When the reflecting tube 6 is at the forefront position shown by a solid line in FIG. 2, it extends upward substantially at right angles to the axis of the reflecting tube 6 and passes through a cutout groove 10 provided at the front end of the upper end of the reflecting tube 6. A boss portion formed at an end of the lower arm portion 11 extending to the outside of the reflecting tube 6 and an upper arm portion 12 which bends and extends rearward from the arm portion 11 in this state; At 13, it is fixed to a support shaft 14. FIG. 4 is a perspective view of the swing arm 8. When the reflecting tube 6 is located at the forefront (during high-speed rotation of the engine), the lower arm portion 11 abuts on the lower surface of the notch groove 10 to close the groove 10 to reduce the output of the engine. A sealing plate 15 is provided for prevention. The periphery of the notch groove 10 is reinforced by a reinforcing member 16.

The rear end of the rear expanding portion 3b is a tapered portion 3c as described above, and the rear exhaust pipe 4 having a small diameter is connected to the rear end thereof. 3c
The rear end of the reflection tube 6 is slidably supported by the connection tube 17. Since the sliding surface 18 at the rear end of the reflection tube 6 is formed in an arc-shaped cross section,
Can slide while swinging to some extent with respect to the connection pipe 17.

The support shaft 14 is disposed above the reflector 6 at a position substantially at the center of the moving range T of the reflector 6, and is attached to a mounting flange 19 (FIGS. 1 and 3) provided on the tube wall of the rear expanding portion 3b. It penetrates freely and protrudes outside the exhaust pipe. A pulley 20 is attached to the tip. A pulley housing 21 that covers the pulley 20 is mounted on the mounting flange 19.
The pulley 20 is driven by a motor (not shown) via a wire or the like, and the operation of the motor is controlled by an engine speed detecting device according to the engine speed. As a result, when the engine speed is high, the reflecting tube 6 and the swing arm 8
Is at the forefront position shown by the solid line in FIG. When the engine speed decreases from this state, the support shaft 14 rotates counterclockwise in the figure, and the swing arm 8 swings backward, so that the reflecting tube 6 slightly swings with respect to the axis of the connecting tube 17. While being guided by the connecting pipe 17, it moves backward, and finally the reflecting pipe 6 and the swing arm 8 reach the rearmost position shown by the broken line.

At this time, paying attention to the positional relationship between the swing arm 8 and the reflecting tube 6, the lower arm portion 11 of the swing arm 8 enters the notch groove 10 deepest when the reflecting tube 6 is at the forefront position. Thereafter, as the reflecting tube 6 retreats, it comes out of the notch groove 10 forward, and finally escapes completely from the notch groove 10 and reflects from the opening at the front surface of the reflecting tube 6 as shown by the broken line in the figure. It comes into the pipe 6. Therefore notch groove 10
It is sufficient if the arm portion 11 of the swing arm 8 is long enough to pass at the forefront position of the reflecting tube 6, and it is not necessary to make the notch groove 10 longer than this in preparation for the swing motion of the swing arm. Absent. That is, by keeping the opening area of the notch groove 10 to a minimum,
A decrease in engine output caused by a part of exhaust gas passing through the inside of the reflecting tube 6 during the low-speed rotation of the reflecting tube 6 retreating and escaping out of the reflecting tube 6 through the notch 10 (the effect of improving the engine output by reflected waves). Drop) can be minimized.

Since the support shaft 14 is provided at an intermediate position between the frontmost position and the rearmost position of the reflecting tube 6, a required reflecting tube moving range T can be secured by the relatively short swing arm 8.

At the time of high-speed rotation where a large engine output is desired, as described above, the seal plate 15 provided on the swing arm 8 is
To prevent the exhaust gas from leaking to the outside of the reflective tube 6 through the cutout groove 10, and further, to prevent the exhaust gas from leaking from the peripheral edge of the front surface of the reflective tube 6, the exhaust gas is provided on the outer periphery of the front surface of the reflective tube 6. The protruding edge 22 is provided with a seal ring 23 abutting from the front. The seal ring 23 is urged rearward by a seal spring 24. When the reflecting tube 6 reaches the forefront position, the protruding edge 22 seals the seal ring 23 with a seal spring.
By pressing forward against the force of 24, the protruding edge 22 and the seal ring 23 come into close contact with each other over the entire surface.
Reference numeral 25 denotes a stopper for restricting the backward movement of the seal ring 23.

The rear end 3d of the front inflatable portion 3a is formed with a small diameter in order to accommodate the seal spring 24 in the inflatable portion 3, and the rear inflate is provided with a radial gap around the rear end 3d. The front end 3e of the portion 3b extends, and a seal spring 24 is provided in an annular space formed between the two. Further, this space is divided into two parts by the intermediate wall 26. The rear end of the intermediate wall 26 is hermetically welded to the rear end of the rear end 3d of the front expanding portion 3a, and the front portion of the intermediate wall 26 is airtightly welded to the front end of the front end 3e of the rear expanding portion 3d. . The seal spring 24 is located outside the intermediate wall 26 and the front end is
Has been received by 26. The intermediate wall 26 extends further forward from the welded portion with the front end portion 3e to form a part of the tube wall of the expansion portion 3, and the front end thereof is welded to the outer wall of the front expansion portion 3a. An air opening 27 is provided in the tube wall portion 26a, and a gap 28 communicating with the atmosphere is formed between the rear end 3d of the front expanding portion 3a and the intermediate wall 26. This gap 28
Exhaust heat dissipated to the outside through the rear end 3d is blocked from the seal spring 24 to prevent the seal spring 24 from becoming hot and deteriorating.

When the reflecting tube 6 is located at the rearmost position shown by the broken line in FIG. 2, the conical tube wall of the reflecting tube 6 and the tapered portion of the rear expansion portion 3b are formed.
A dead space 30 communicating with the front portion of the expansion portion 3 through an annular gap 29 between the protruding edge 22 on the outer periphery of the front surface of the reflection tube 6 and the tube wall of the rear expansion portion 3b is formed between the reflection tube 6 and the tube wall 3c. You. The pressure wave in the exhaust gas enters the dead space 30 via the gap 29, and the reflected wave reflected in the dead space 30 travels forward in the exhaust pipe through the gap 29.
It is behind the reflected wave reflected inside. Therefore, if the reflected wave from the dead space 30 is used, it is possible to correspond to a lower engine speed. That is, the output can be improved over a wide engine speed range in a relatively short reflecting tube movement range T, so that the apparatus is downsized.

FIG. 5 shows another embodiment of the present invention, and the same parts as those in the above embodiment are denoted by the same reference numerals. In the present embodiment, a control pipe is provided with an inlet pipe 31 having a small-diameter opening 31a at the front end and a large-diameter opening 31b at the rear end. The negative pressure wave generated at this time travels upstream and reaches the exhaust port of the engine. The introduction tube 31 occupies the front position when the engine is rotating at a high speed, and occupies the rear position when the engine is rotating at a low speed, similarly to the reflection tube 6 in the above embodiment. In FIG. 5, the time when the introduction tube 31 is at the rear position is indicated by a solid line, and the time when the introduction tube 31 is at the front position is indicated by a broken line. The swing arm 8 is pivotally connected to the introduction pipe 31 near the large-diameter opening 31b, that is, at the rear end of the introduction pipe 31.
When 31 is at the rearmost position, it extends to the outside of the introduction tube 31 through the cutout groove 10 provided at the upper rear end of the introduction tube 31, and is bent forward and fixed to the support shaft 14. . At this time, the swinging arm 8 has entered the notch groove 10 most deeply, and thereafter escapes backward from the notch groove 10 as the introduction pipe 31 advances. Therefore, also in the present embodiment, the length of the notch groove 10 can be minimized, and the support shaft 14 is connected to the introduction pipe 31.
Is provided at an intermediate position between the foremost position and the rearmost position, a required introduction pipe moving range can be secured with a relatively short swing arm.

According to the present invention, there is provided an exhaust pipe of a two-stroke engine including a frusto-conical pressure wave control pipe having a large-diameter opening and a small-diameter opening at both ends so as to be movable in the axial direction. Swinging a swing arm, which is pivotally connected to the control tube inside the control tube and the other end is connected to a support shaft provided outside the control tube, about the support shaft. By moving the control tube in the axial direction, the axial position of the support shaft is set at an intermediate portion of the movement range of the control tube, and the swing arm is attached to the control tube by the large diameter. Near the opening end of the control tube, and when the control tube is at one end of the movement range, the peripheral wall of the control tube is substantially radiused near the large-diameter opening end. After penetrating from inside to outside in the direction The length of the notch groove provided in the control pipe for allowing the swing arm to pass through is shortened because it is bent to form a crank-shaped bent shape facing the support shaft. The output of the engine hardly decreases. In addition, since the support shaft supporting the swing arm is located in the middle of the movement range of the control tube in the axial direction, a long movement length of the control tube can be secured with a short swing arm.

[Brief description of the drawings]

FIG. 1 is an external view of an exhaust pipe of a two-stroke engine for a motorcycle according to one embodiment of the present invention, FIG. 2 is an enlarged sectional view of an expansion portion thereof, and FIG. 3 is a reflection pipe and a swing attached thereto. FIG. 4 is a front view of the moving arm, FIG. 4 is a perspective view of the swing arm, and FIG. 5 is a drawing similar to FIG. 2 showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... exhaust pipe, 2 ... connection part, 3 ... expansion part, 4 ... rear exhaust pipe, 5 ... flange, 6 ... reflection pipe (control pipe),
7 ... axis, 8 ... swing arm, 9 ... sleeve, 10 ...
Notch groove, 11, 12… Arm part, 13 boss part, 14… Support shaft, 15… Seal plate, 16… Reinforcement, 17… Connection pipe, 18
…… Sliding surface, 19 …… Mounting flange, 20 …… Pulley, 21…
... pulley housing, 22 ... protruding edge, 23 ... seal ring, 24
…… Seal spring, 25… Stopper, 26 …… Intermediate wall, 27 …… Atmosphere opening port, 28 …… Void, 29 …… Gap, 30…
... dead space, 31 ... introduction pipe (control pipe).

Claims (1)

(57) [Claims] An exhaust pipe of a two-stroke engine having a frusto-conical pressure wave control pipe having a large-diameter opening and a small-diameter opening at both ends, which is movable in the axial direction. By swinging a swing arm, which is pivotally connected to the control pipe inside the pipe and the other end is connected to a support shaft provided outside the control pipe, about the support shaft, In a configuration in which the control pipe is moved in the axial direction, the axial position of the support shaft is set at an intermediate portion of a movement range of the control pipe, and the swing arm is connected to the control pipe by the large-diameter open end. And connecting the swing arm with the control wall at one end of the movement range and moving the peripheral wall of the control tube substantially radially near the large-diameter opening end. Bends after penetrating from outside An exhaust pipe of two-cycle engine, characterized in that formed in the crank-shaped bent shape towards.