JPS58202320A - Discharge device for two-cycle engine - Google Patents

Abstract

PURPOSE:To prevent the resonant frequency of a resonance pipe from being varied by bringing the pipe wall of the resonance pipe into contact with a high temperature portion near a discharge port so that the heat quentity conveyed to the resonance pipe is increased and thereby the temperatre change due to the effect of the outside air, etc. is decreased. CONSTITUTION:An exhauster 5 is constituted with a discharge pipe 7 connected to the discharge hole 6a of a two-cycle engine 6 and a resonance pipe 8 with its pipe wall 8a brought into contact with the inner peripheral surface 7a of the discharge pipe 7 which is near the discharge hole 6a and becomes a high temperature when the engine is in operation. The discharge pipe 7 is provided so that the frequency characteristic of a pulsating wave due to the discharge gas flowing through the discharge pipe 7 matches the opening/closing timing of the discharge hole 6a when the engine 6 is operated at a high speed. The resonance pipe 8 is formed in a cylindrical shape with its both ends closed, and a resonance chamber 8c inside the reconance pipe is communicated to the inside of the discharge pipe 7 through an opening portion 8b formed on the pipe wall 8a.

Description

[Detailed Description of the Invention] This invention provides an exhaust pipe connected to an exhaust hole of an engine;
The present invention relates to an exhaust system for a two-stroke engine that includes a resonance pipe that forms a resonance chamber that communicates with the inside of the exhaust pipe.

The flow of exhaust gas in the engine exhaust pipe is a pulsating flow.
A pulsating wave whose traveling speed WIL changes depending on the engine speed is generated in the exhaust pipe.

In a two-stroke engine, the frequency characteristics of this pulsating wave are matched with the opening and closing timing of the engine's exhaust port, and the pulsating wave reflected at the rear of the exhaust pipe creates positive pressure around the exhaust port at the end of the exhaust process. By doing so, the fresh air blown into the exhaust pipe by the positive pressure around the exhaust hole is pushed back into the cylinder (into the cylinder), increasing the scavenging efficiency, and the output of the engine can be custom-made.

However, the frequency characteristics of the pulsating waves within the exhaust pipe are greatly influenced by the dimensions and shape of the exhaust pipe, and once the dimensions and shape of the exhaust pipe are determined, the frequency characteristics of the pulsating waves obtained by the exhaust pipe are The engine speed is limited to a range in which the output characteristics can be effectively improved by matching the opening/closing timing of the exhaust hole, and at other speeds, negative pressure acts around the exhaust hole, reducing the amount of pressure sent into the cylinder. There is a risk that the scavenging efficiency will decrease as the fresh air that was introduced is sucked out, resulting in a decrease in the output.

Therefore, in recent years, exhaust pipes have been equipped with resonance pipes that resonate in a certain frequency range, and in engine speed ranges where negative pressure is applied around the exhaust hole, the resonance pipe can resonate and attenuate the pulsating waves. An exhaust system has been developed that measures the decrease in negative pressure and prevents a decrease in output in the engine speed range where negative pressure acts on the exhaust hole. Figures 11 and 2 show conventional examples. The one indicated by 1 is Misaki Sou! It is. This exhaust system #1 includes a nine exhaust pipe 3 connected to the exhaust hole 2 of the two-stroke engine, and a resonance pipe 4 whose open end 4a is connected to the peripheral wall of the exhaust pipe 3 on the exhaust hole 2 side. t, has been done.

By the way, when designing the resonance tube 4 mentioned above, it is necessary to make sure that the unique resonance frequency of the resonance tube 4 is the same as the frequency of the pulsating wave around the exhaust hole (in the engine speed range where negative pressure acts). Accordingly, the shape and dimensions of the resonance tube are determined so that the resonance damping of the pulsating waves is achieved only when the tsunoda acts around the exhaust hole.

However, the resonant frequency of a resonance tube is not only a function of the shape and dimensions of the resonance tube, but also a function of the speed of sound, and the speed of sound changes depending on the temperature of the transmission medium (in this case, the gas inside the resonance tube). Therefore, as shown in Figure 1, if the tube wall of the first resonance tube 4 is separated from the exhaust pipe and the temperature inside the resonance tube is likely to change due to cooling by outside air, etc., the speed of sound will change with the temperature change. As a result, the resonant frequency of the resonant tube 4 fluctuates, so that the damping effect of the pulsating waves cannot be obtained in the desired engine speed range, and the output characteristics of the engine may not be improved as much as expected at the time of design. Takko's invention was made in consideration of the above circumstances, and by preventing fluctuations in the resonant frequency of the resonant tube and effectively attenuating the pulsating waves within a preset engine speed range, the engine output can be improved. The purpose is to propose an exhaust system C whose characteristics can be improved almost as designed.

In this invention, the pipe wall of the resonance pipe that communicates with the inside of the exhaust pipe and forms nine resonance chambers is connected to a high-temperature area near the exhaust hole of the engine, such as the exhaust pipe wall near the exhaust hole, By contacting the internal parts of the engine body near the exhaust hole (cylinder head, cylinder, etc.) and increasing the amount of heat transferred from the high temperature part near the exhaust hole to the resonance tube, it is possible to reduce the influence of outside air etc. This shows how the 1 liam change inside the resonance tube has been flattened and made smaller.If the temperature change inside the resonance tube is made extremely small, the change in sound speed due to the temperature change can also be small.
This prevents fluctuations in the resonant frequency as a function of the speed of sound.

Embodiments of the present invention will be described below with reference to the drawings.

3 and 4 show a first embodiment of the present invention, in which 5 is an exhaust device. This exhaust device 5 includes an exhaust pipe 7 connected to an exhaust hole 6a of a %2 cycle engine 6, and a pipe wall 8a on the inner circumferential surface 7a of the exhaust pipe 7, which is close to the exhaust hole 6a and becomes hot during engine operation. Sakaki is formed from the resonance tube 8 brought into contact.

The exhaust pipe 7 is designed so that the frequency characteristics of the pulsating waves caused by the exhaust gas flowing inside the exhaust pipe 7 match the opening/closing timing of the exhaust hole 6a when the engine 6 rotates at high speed. , it is very effective in determining the shape and quantification of Si%.

The resonance tube 8 has a cylindrical shape with both ends 1 closed.
A resonance chamber 8c inside the resonance tube communicates with the inside of the exhaust pipe 7 through an opening 8b formed in the tube wall 8a. The resonance frequency of the resonance pipe 8 is designed to coincide with the pulsating waves generated in the exhaust pipe 7 when the engine 6 rotates at low speed.

None, in addition to the engine 6 mentioned above, 6b is engine 11f,
6a'ri cylinder head, 6dH piston, 6th
Crankshaft, 5f, pumps fresh air into cylinder 6b, inner K
R is a scavenging hole for letting in air.

Hereinafter, the second to sixth embodiments of the present invention will be explained in order, but the parts common to the first embodiment will be explained.

The same numbers are given to simplify the explanation.

Figures 5 and 6 show a second embodiment of the present invention. This embodiment differs from the first embodiment in that the high temperature part near the exhaust hole 6a is located on the outer peripheral surface of the first exhaust pipe 7 on the exhaust hole 6a side, and the shape of the resonance tube 9 that is brought into contact with this outer peripheral surface is made into a hollow cylindrical shape to form a cylindrical resonance chamber 9a that covers the outer periphery of the exhaust pipe 7. The inner cylindrical wall of the resonance tube 9 for forming the cylindrical resonance chamber 9a uses the pipe wall of the exhaust pipe 7, and the resonance chamber 9a and the inside of the exhaust pipe 7 are connected to the pipe wall of the exhaust pipe 7. A communication hole 10t is formed to communicate with each other.

Figures 7 and 8 show a third embodiment of the present invention. In this embodiment, as in the second embodiment described above, the high temperature part near the exhaust hole 6 & is set on the outer circumferential surface of the exhaust pipe 7 on the exhaust hole 6a side, but the resonance chamber 11 of the resonance tube 11 is It is formed into a substantially rectangular parallelepiped shape extending along the longitudinal direction of the exhaust pipe 7, and is further provided with an exhaust winding around the outer peripheral surface of the exhaust pipe 7 on the wall of the resonance pipe 11. The resonance chamber 11 & is connected to the inside of the exhaust pipe 7 through a communication hole 10 formed in the wall of the exhaust pipe 7.

Figure IE9 shows a fourth embodiment of the present invention. In this embodiment, the engine body of the engine 6, particularly the cylinder 6b, is selected as the high temperature part near the exhaust hole 6a. In this embodiment, the tube wall of the resonance tube 12 is integrated with the cylinder 6b, and a cylindrical resonance chamber 12a having an axis perpendicular to the longitudinal direction of the exhaust tube 7 is located below it (the ninth FIG. 10 shows a fifth embodiment of the present invention.

In this embodiment, the engine □ main body of the engine 6 is selected as the high temperature part near the exhaust hole 6a, as in the fourth embodiment, but the resonance pipe 13 whose pipe wall is formed integrally with the engine main body is used. This embodiment is different from the fourth embodiment described above in that it is disposed astride the cylinder 6b and the cylinder head 6cK, and that the resonance chamber 13a is formed in a hook-shaped bent shape. The resonant chamber 13a communicates with the exhaust pipe 7 through an opening 13b disposed at the lower part of the resonance chamber 13a through an exhaust gas passage 6g inside the cylinder.

11 and 12 show a sixth embodiment of the present invention. In this embodiment, the exhaust hole 6 is similar to the first embodiment.
The inner circumferential surface of the exhaust pipe 7 is selected as the high temperature area near a. The resonance pipe 14 has a recess 14b formed in a part of a cylindrical pipe wall 14a that fits into the inner periphery of the exhaust pipe 7.
4b is covered with the inner peripheral surface of the exhaust pipe 7 to form a resonance chamber, and a communication hole 14c for communicating the resonance chamber with the inside of the exhaust pipe 7 is formed in a part of the recess 14b). In the above-mentioned embodiment, in order to communicate the resonance chamber of the resonance tube with the inside of the exhaust pipe (resonance tube), the shape of the opening may be arbitrary, and the position of the opening may be determined as described above. It is not necessary to limit it to the upstream side of the exhaust pipe 7 as in the embodiment.

As explained above, the exhaust system of the present invention brings the tube wall of the resonance tube, which forms a resonance chamber communicating with the inside of the exhaust pipe, into contact with the high temperature area near the exhaust hole of the engine. Since the amount of heat transferred from the tube to the resonance tube is increased, temperature changes inside the resonance tube due to the influence of outside air (cooling effect) can be made extremely small. If the temperature change inside the resonant tube is small, the amount of change in the speed of sound due to the change in temperature is also reduced, so fluctuations in the resonance frequency, which is a function of the speed of sound, are prevented. Therefore, when designing a resonance tube, if the resonance frequency is matched to the frequency of the pulsating wave in the engine speed range where negative pressure acts around the exhaust hole of the engine, it is possible to It is possible to reliably damp the pulsation force in the engine speed range where negative pressure acts on the engine, thereby improving the engine's output characteristics almost as designed. In addition, the exhaust pipe is designed so that the FR wave number characteristics of the pulsating waves match the opening and closing timing of the exhaust hole when the engine rotates at high speeds, and the pulsating waves that occur when the engine rotates at low speeds are damped by resonance with the resonance pipe. For example, it is possible to improve the output characteristics of the engine, as well as make the exhaust system more compact and lighter. Furthermore, in the exhaust system of the present invention, since the resonance pipe does not protrude significantly around the exhaust pipe, it is easy to improve the design by making the entire exhaust aW into a smart shape.

[Brief explanation of drawings]

Figures 1 and 2 show a conventional exhaust system, in which Figure 1 is a longitudinal sectional view, Figure 2 is a sectional view taken along 1Ifs in Figure 1, and Figures 3 and 4 are according to the present invention. Fig. 3 is a longitudinal sectional view, Fig. 4 is a sectional view taken along the line ■-■ in Fig. 3, and Fig. 5 and IE6 show the @2 embodiment. , FIG. 5 is a longitudinal sectional view, FIG. 6 is a sectional view taken along the line ■-■ in FIG. , Figure 8 is the ■− of Figure 7.
■ IE9 is a vertical sectional view showing the IE4 embodiment, FIG. 10 is a longitudinal sectional view showing the fifth embodiment, and FIGS. It shows,
FIG. 11 is a longitudinal sectional view, and FIG. 12 is a sectional view taken along the --store line in FIG. 11. 5...Exhaust! ! e position, 6...2 cycle engine. 6a---Exhaust hole, 7---Exhaust pipe, 8---
...Resonance tube. 8c... Resonance chamber, 9... Resonance tube, 9a
... Resonance chamber, 11 ... Resonance tube, 11a
...-Resonance chamber h12, 13...-Resonance tube, 1
2JL, 13B...Resonance chamber, 14...
Resonance tube, 14b... recess. Applicant: Honda Motor Co., Ltd. Agent Patent Attorney: Shiga Formal Procedural Amendment (Own Ship 1. Indication of the Case 1982 Patent Application No. 77850 2, Name of Invention 2-stroke Engine Exhaust System 3, Make amendments) (3; 32) Houda Giken Kogyo Co., Ltd. 4. Detailed clarification of the agent. 6. Contents of amendment (1) The scope of the patent claims will be amended as shown in the attached sheet. [ Temporary 1
and correct it. (4) Correct ``Tube J18at[touch 1'' on page 6 @ line 3 of the letter of specification to [temporary installation (contact) 1 on the upper outer peripheral surface of the tube wall 8a]'' (6) Letter 7 of the specification @ line 1 of 20 "on the tube wall" is corrected to 1 as part of the wall. (6) Add the "heat absorption plate 11b" in the first line of your letter to [
Correct the heat absorption WLI 1 bJ. (]) Specification @ IO page II/spans from line to line 2 [Resonance tube tube I! , and at least one side of the wall surface of the J rtr' resonance tube is corrected to I. (8) Specification No. 101! @2nd line [&! Correct T-1 to 1-biF, rJ. Claims (1) In an exhaust system for a two-stroke engine, comprising an exhaust pipe connected to an exhaust hole of the engine, and a resonance pipe forming a resonance chamber communicating with the inside of the exhaust pipe. An exhaust cover for a two-stroke engine, characterized in that at least one side of the wall surface is provided at a height ms near the exhaust hole. (2) The exhaust system for a two-stroke engine according to claim 1, wherein the pyrometer is an inner peripheral surface of an exhaust pipe. (8) Said High School 1! 2. The exhaust system for a two-stroke engine according to claim 1, wherein the portion is an outer circumferential surface of an exhaust pipe. (4) Claim No. 2 of Claim #kM@-JJI, characterized in that the high temperature deposit is in the engine body near the exhaust hole.
Exhaust system for cycle engines.

Claims (4)

[Claims] (1) In the engine exhaust hole! In a two-stroke engine exhaust system, the exhaust system for a two-stroke engine includes an exhaust pipe that is connected to the exhaust pipe, and a resonance pipe that forms a resonance chamber that communicates with the inside of the exhaust pipe. An exhaust system for a two-stroke engine, characterized in that the exhaust system is in contact with. (2) The exhaust system for a two-stroke engine according to claim 1, wherein the high temperature portion is an inner circumferential surface of an exhaust pipe. (3) The exhaust system for a two-stroke engine according to claim 1, wherein the high temperature portion is an outer circumferential surface of an exhaust pipe. (4) The exhaust for a two-stroke engine according to claim 1, characterized in that the high temperature part is the engine body near the exhaust hole! ! ! Place.