JPH02223633A - 2 cycle engine exhaust pipe - Google Patents

Abstract

PURPOSE:To allow certain sealing between the outer periphery of a control pipe end and the wall of an exhaust pipe by forming on the wall of the exhaust pipe on a continuous basis, an inner wall pipe which covers a sealing member, provided at the position of one end of the control pipe, via a gap inwardly in a radial direction to the sealing member. CONSTITUTION:At the position of one end of a reflecting pipe 6 in an exhaust pipe 1, a sealing member 30 is provided which continues over the whole periphery of the inner face of the exhaust pipe 1 and comprises a seal ring 23 movable to an axial direction in contact with the end face of the outer periphery portion of the reflecting pipe 6 and a seal spring 24 energizing the seal ring 23 toward the end face of the outer periphery portion. An inner wall pipe 29 which covers the seal member 30 via a cavity 28 inwardly in a radial direction to the seal member 30 is formed on the wall of the exhaust pipe 1 on a continuous basis. As a result, certain sealing can be performed between the outer periphery of the end of the reflecting pipe 6 and the wall of the exhaust pipe 1 to enhance the effect of improving engine output.

Description

[Detailed description of the invention] Rikuri Retired Emperor's skin ■ Separation This article relates to an exhaust pipe for a zero-engine C'x2 cycle engine.

In the J25 2-cycle engine, the pressure waves in the exhaust gas are reflected in the exhaust pipe toward the engine exhaust port, and the positive or negative reflected waves reach the exhaust port at an appropriate time, allowing fresh air to flow through the exhaust pipe. The engine's output is improved by preventing blow-by or helping to suck out combustion gas. For example, Jiko Sho 4
In the exhaust pipe of the two-stroke engine shown in Publication No. 7-22045, a control pipe (sliding pipe) for reflecting pressure waves is provided inside the muffler pipe, and this sliding pipe is When the engine rotates at high speeds, the engine is moved forward to shorten the effective length from the exhaust port, so that the reflected waves reach the exhaust port earlier, and when the engine rotates at low speeds, it is moved back to lengthen the effective length from the exhaust port, so that the reflected waves reach the exhaust port. This is to delay the process.

In addition, in the exhaust pipe for a two-stroke engine described in Japanese Utility Model Application Publication No. 63-51117, a constriction part having the same effect as the sliding tube is moved forward and backward relative to the front part of the exhaust pipe, thereby exhausting the engine exhaust gas. In this exhaust pipe, a spring is interposed between the front part of the exhaust pipe and the throttle part to change the effective length from the mouth to the throttle part.

In the exhaust pipe described in the above-mentioned Japanese Utility Model Publication No. 47-22045, when the engine rotates at high speed, when the pressure wave reflection function of the sliding tube is most desired, that is, when the sliding tube moves forward, Since no means was taken to seal between the outer circumference of the sliding tube and the inner circumference of the exhaust pipe, some of the exhaust gas escaped to the outside of the sliding tube.
The pressure wave control function of the sliding tube is reduced accordingly, and the effect of improving engine output is reduced.

The same applies to the exhaust pipe described in Japanese Utility Model Application Publication No. 63-51117, but since the spring in this exhaust pipe is exposed to high-temperature exhaust gas, it is difficult to maintain its elasticity.

The present invention has been made in view of these circumstances,
In the present invention, in the exhaust pipe of a two-stroke engine having a built-in pressure wave control pipe that is movable in the axial direction, the pressure wave control pipe is placed at one end position of the movement range of the control pipe in the exhaust pipe, and on the entire circumference of the inner surface of the exhaust pipe. A sealing member is provided, comprising an axially movable sealing ring which is continuous over the entire range and abuts against the outer peripheral end face of the control tube, and a biasing means for urging the seal ring toward the outer peripheral end face. An inner wall pipe is formed inwardly in the radial direction of the member so as to be continuous with the exhaust pipe wall and cover the seal member with a gap therebetween.

According to the present invention, just before the control pipe moves within the exhaust pipe and reaches one end position of its movement range, the outer peripheral end surface of the control pipe abuts the seal ring, and the seal ring moves to the end position. Push forward. Since the seal ring is urged toward the outer peripheral end face by the urging means, assembly errors and precision errors of the control tube are absorbed during this time, and the outer peripheral end face of the control pipe and the seal ring are The outer periphery of the end of the control pipe and the wall of the exhaust pipe are effectively sealed.

The seal member consisting of the seal ring and the biasing means is covered from radially inward by an inner wall pipe that is continuous with the exhaust pipe wall, and a gap is interposed between the inner wall pipe and the seal member.
The sealing member, especially the biasing means made of a spring or the like, is less affected by exhaust heat, and the biasing means does not deteriorate due to high temperatures. Therefore, the biasing means maintains elasticity or biasing force for a long period of time, ensuring sealing performance by the seal ring.

Figure 1 is an external view of an exhaust pipe of a two-stroke motorcycle engine according to an embodiment of the present invention. This exhaust pipe 1 is connected at a connecting portion 2 at the front end to an exhaust port of a two-stroke engine mounted on a motorcycle. and the connection part 2
As shown in the figure, the curved rear lower part of the vehicle body extends rearward, and an expansion part 3 whose diameter gradually increases is formed behind this curved part. The rear part of the expansion part 3 is tapered,
A small diameter rear exhaust pipe 4 is connected to the rear end.

The rear exhaust pipe 4 extends upward and rearward along the side of the vehicle body.
The rear end opens toward the rear of the vehicle. The inflatable section 3 consists of a front inflatable section 3a and a rear inflatable section 3b, and each of these front and back inflatable sections 3a and 3b is formed by joining semi-tubular bodies divided into left and right sides to each other via a flange 5 to form a tubular shape. It is formed.

FIG. 2 is an enlarged 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 expansion section 3b. The reflector tube 6 is a conical tube that converges toward the rear, and when the exhaust gas passes through the reflector tube 6, pressure waves are reflected toward the upstream side, and these reflected waves reach the engine exhaust port at an appropriate time. By doing so, the output of the engine is improved as described above. Therefore, in order to match the arrival timing of the reflected waves and the opening/closing timing of the exhaust port, the reflection tube 6 can be moved back and forth. That is, when the engine rotates at high speed, the reflection tube 6 occupies the front position shown by the solid line in the figure, and when the engine rotates at low speed, it occupies the rear position as shown by the broken line.

Therefore, as shown in FIG. 3, a shaft 7 is installed in the lower part of the reflection tube 6 near the front end face, crossing the inside of the reflection tube 6. A fixed sleeve 9 is rotatably fitted. The swinging arm 8 extends upward substantially at right angles to the axis of the reflection tube 6 when the reflection tube 6 is in the forwardmost position shown by the solid line in FIG. A lower arm portion 11 extends to the outside of the reflective tube 6 through the groove 10, and an upper arm portion 12 extends backward from the arm portion 11 in this state.
a boss portion 13 formed at the end of the arm portion 12;
It is fixed to the support shaft 14 at. Lower arm part 11
includes a seal plate 15 that comes into contact with the lower surface of the notched groove 10 to close the groove 10 when the reflecting tube 6 is at the forefront (when the engine rotates at high speed) to prevent a decrease in engine output. is provided. The peripheral edge of the notched groove 10 is reinforced with a reinforcing material 16.

The rear end of the rear expansion part 3b is the tapered part 3C as described above, and the small diameter rear exhaust pipe 4 is connected to the rear end, but the connecting pipe 17 connected to the rear exhaust pipe 4 is the tapered part. 3c, and the rear end of the reflecting tube 6 is slidably supported by this connecting tube 17. Note that since the sliding surface 18 at the rear end of the reflection tube 6 is formed to have an arcuate cross section, the reflection tube 6 can slide with respect to the connection tube 17 without swinging to a certain extent.

The support shaft 14 is disposed above the reflection tube 6 at approximately the center of the movement range T of the reflection tube 6, and rotates a mounting flange 19 (Fig. 1.3) provided on the tube wall of the rear expansion section 3b. It freely penetrates and protrudes to the outside of the exhaust pipe. A pulley 20 is attached to its tip. A pulley housing 21 that covers the boo IJ20 is attached to 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 according to the engine speed by an engine speed detection device.

As a result, when the engine speed is high, the reflection tube 6 and the swing arm 8 are in the forwardmost 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 swinging arm 8 swings rearward, causing the reflection tube 6 to swing somewhat with respect to the axis of the connection pipe 17. While being guided by the connecting tube 17, the reflecting tube 6 and the swinging arm 8 finally reach the rearmost position shown by the broken line.

During high-speed rotation when a large engine output is desired, the seal plate 15 provided on the swing arm 8 is inserted into the notch groove 1 as described above.
0 and prevents exhaust gas from leaking to the outside of the reflection tube 6 through the notched groove 10. Furthermore, in order to prevent exhaust gas from leaking from the front periphery of the reflection tube 6, a groove is provided on the front outer periphery of the reflection tube 6. A seal ring 23 is provided which comes into contact with the surface of the raised edge 22 from the front.

The seal ring 23 has a flange portion 23 that continuously protrudes along the entire circumference along the inner surface of the exhaust pipe and faces the projecting edge 22.
a, and a tubular portion 23 extending forward from the flange portion 23a.
b, and an engaging portion 23c protruding from the front end of the tubular portion 23b.
and a seal spring 2 that engages with the engaging portion 23c.
4 (biasing means) toward the rear.

The rearward movement of the seal ring 23 is restricted by the engaging portion 23c engaging with the stopper 25, as shown by the broken line in the figure. A seal member 30 consisting of the seal ring 23, seal spring 24 and stopper 25 is disposed along the inner circumferential surface of the front end 3d of the rear expansion portion 3b, with a gap radially inward of the seal member 300. An inner wall tube 29 extends back and forth so as to cover the sealing member 30 from inside. The inner wall tube 29 is formed continuously with the front inflation section 3a by forming the rear end of the front inflation section 3a into a small diameter and extending into the front end 3d of the rear inflation section 3b. .

The annular space between the sealing member 30 and the inner wall tube 29 is further divided into two parts, an inner and outer part, by an intermediate wall 26. The rear end of the intermediate wall 26 is hermetically welded to the rear end of the inner wall tube 29.
The front part of the intermediate wall 26 is hermetically welded to the front end of the front end part 3d of the rear expansion part 3b. The seal spring 24 is located outside the intermediate wall 26 and has its front end received by the intermediate wall 26. The intermediate wall 26 extends further forward from the welded portion with the front end portion 3d and becomes a part of the tube wall of the inflatable portion 3, and its front end is welded to the outer wall of the front inflatable portion 3a. Atmospheric opening 2 is provided in this tube wall portion 26a.
7 is provided, and a gap 28 communicating with the atmosphere is formed between the inner wall tube 29 and the intermediate wall 26.

When the reflecting tube 6 is in the rear position, the seal ring 23 is pressed by the seal spring 24 and regulated by the stopper 25, and is in the rear protruding position shown by the broken line. When the reflecting tube 6 moves forward, the projecting edge 22 comes into contact with the seal ring 23 located at this rear protruding position, and thereafter the projecting edge 22 and the seal ring 23 contact each other.
and move forward while maintaining contact with each other and compressing the seal spring 24.

Due to assembly errors and precision errors, the seal ring 23 and ridge 2 were initially
Even if the seal ring 23 and the protrusion 22 do not come into perfect contact with each other, their mutual relationship will be automatically adjusted while they move forward, and when they reach the final position shown by the solid line, the seal ring 23 and the protrusion 22 will be completely in contact with each other. It remains in close contact for a long time. In addition, at this time, the front surface of the flange portion 23a is in close contact with the end surface of the intermediate wall 26 welded to the inner wall tube 29, so the space between the front edge of the reflection tube 6 and the exhaust pipe is completely sealed, and the engine output The improvement effect increases.

In order to obtain the above-mentioned sealing action, the seal spring 24 must have sufficient elasticity, but if the seal spring 24 becomes high in temperature due to exhaust heat and deteriorates, the elasticity will be lost. However, in this embodiment, an inner wall tube 29 is provided inside the seal spring 24 to prevent the seal spring 24 from being exposed to exhaust gas, and a space between the inner wall tube 29 and the intermediate wall 26 is communicated with the atmosphere. Since the gap 28 is formed to block exhaust heat dissipated to the outside through the inner wall pipe 29 from the seal spring 24, the seal spring 24 will not deteriorate due to high temperature.

As described above, in the present invention, in the exhaust pipe of a two-stroke engine incorporating a pressure wave control pipe that is movable in the axial direction, the control pipe is located at one end position of the movement range of the control pipe within the exhaust pipe. , an axially movable seal ring that extends along the entire circumference of the inner surface of the exhaust pipe and abuts against the outer peripheral end surface of the control pipe; and a biasing means that urges the seal ring toward the outer peripheral end surface. A seal member is provided, and an inner wall pipe is formed inwardly in the radial direction of the seal member to cover the seal member with a gap between the inner wall pipe and the exhaust pipe wall. It is possible to reliably seal the space between the exhaust pipe wall and the exhaust pipe wall, thereby increasing the effect of improving engine output. Furthermore, since the biasing means does not become hot and deteriorate due to exhaust heat, the biasing force is maintained over a long period of time, and therefore the above-mentioned sealing effect can be ensured over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is an external view of an exhaust pipe of a two-stroke motorcycle engine according to an embodiment of the present invention, Fig. 2 is an enlarged cross-sectional view of its expansion part, and Fig. 3 is a reflection pipe and a rocker attached to it. FIG. 3 is a front view of the movable arm. 1... Exhaust pipe, 2... Connection part, 3... Expansion part, 4
... Rear exhaust pipe, 5 ... Flange, 6 ... Reflector pipe, 7 ... Shaft, 8 ... Swinging arm, 9 ... Sleeve, lO ... Notch groove, 11 ... ...Arm part, 12...
Arm part, 13... Boss part, 14... Support shaft, 15...
・Seal plate, 16... Reinforcement material, 17... Connection pipe, 1
8...Sliding surface, 19...Mounting flange, 20...
Pulley, 21... Pulley housing, 22... Projection, 23... Seal ring, 24... Seal spring,
25... Stopper, 26... Intermediate L 27... Atmospheric opening, 28... Gap, 29... Inner wall tube, 30...
...Seal member.

Claims (1)

[Claims] In an exhaust pipe of a two-stroke engine having a built-in pressure wave control pipe movable in the axial direction, at one end position of the movement range of the control pipe within the exhaust pipe, the above-mentioned A seal member consisting of an axially movable seal ring that abuts the outer peripheral end face of the control tube and a biasing means that urges the seal ring toward the outer peripheral end face is provided, and a radially inner portion of the seal member is provided. An exhaust pipe for a two-cycle engine, characterized in that an inner wall pipe is formed continuously on the exhaust pipe wall and covers the seal member with a gap between the inner wall and the seal member.