JPS5977020A - Exhaust muffler - Google Patents

Abstract

PURPOSE:To eliminate exhaust noise effectively with simple and small device by branching pulsating exhaust wave from engine into plural flows then shifting phase of expansion timing for every branch to expand pulsating wave and converting to constant pressure flow. CONSTITUTION:Exhaust from engine is led as plusating pressure wave to the flow-in port 4 of muffler 1 and expanded in expansion chamber 9. Then it is passed through plural branch paths 11a-11d formed between spiral guide walls 10 planted on the outercircumferential face of conical head 8 to a gap 7 between outer tube 1 and inner tube 6. Consequently exhaust flow is branched and converted into spiral flow. Here single line of opening 12 is made circumferentially in the inner tube 6 where distances from the downstream end of each branch paths 11a-11d to the opening 12 are made different. Consequently each exhaust branch will reach to the opening 12 with timing shift and expand. Thereafter each exhaust branch will be guided through a guide vane 18 to the delivery port 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust muffler for vehicle engines, general-purpose engines, etc.

Countermeasures against engine exhaust noise have been in the spotlight as a social issue for many years, but sufficient effects have yet to be seen.

Various methods have been used to muffle the sound of engine exhaust. For example, pressure waves are attenuated by guiding the pressure waves of the exhaust into an expansion chamber, expanding them, and then deflating them and repeating no operation multiple times. a resonance absorption method that consumes sound energy by utilizing the resonance effect of exhaust air within the volume of a sound-deadening chamber, an interference method that attenuates sound through the interference of sound waves, or a sound absorption method that uses sound-absorbing materials such as wool. Sound absorption methods are known. However, each of Kowara's sound deadening methods cannot be expected to have a sufficient effect even when used alone, and the current situation is that multiple types of various types are used in combination, but these silencers have extremely complex structures. Therefore, it is desired to reduce the manufacturing time and to improve the sound-deadening ability.

The present invention has been made based on the above circumstances, and its object is to provide an exhaust muffler that has a simple structure and excellent muffling ability.

Exhaust sound is a pressure wave based on the engine exhaust pulsation.
It is known that sound can be muffled by expanding this pressure wave, and that converting a pulsating flow into a steady flow is also effective in muffling sound. The basic principle of the present invention is to expand the pulsating waves from the engine and convert them into constant pressure flows by dividing the pulsating waves from the engine into multiple flows and shifting the phase of the expansion timing for each of these divided flows. . Then, a spiral flow is applied to the branched flow, and the phase of the expansion timing of each branched flow is different due to this spiral flow, thereby making the structure of the exhaust muffler simple and compact.

An embodiment of the present invention will be described below based on the drawings.

In the figure, reference numeral 1 denotes a circular outer cylinder which becomes the main body of the muffler, and both ends are closed by closing plates 2 and 3, and these closing plates 2 and 3 have an exhaust inlet 4 and an exhaust outlet 5. . The inlet 4 communicates with an exhaust pipe of an engine (not shown),
The discharge port 5 is open to the atmosphere.

This is an eFi inner cylinder, and is provided approximately concentrically with the outer cylinder 1. A continuous gap 7 is provided between the outer peripheral surface of the inner cylinder 6 and the inner peripheral surface of the outer cylinder 1 over the entire circumference and the entire length of the inner cylinder 6. Note that the other end of the gap 7 is closed by a closing plate 3. One end of the inner cylinder 6 is closed by a conical head 8, and the other end is open to the discharge port 5. The conical head 8 is spaced apart from and facing the inlet 4, and is located between the conical head 8 and the inlet 4, and has a first tube inside the outer cylinder 1.
An expansion chamber 9 is formed.

A plurality of guide walls 10, for example, four guide walls 10, are provided on the outer peripheral surface of the conical head 8. These guide walls 10・
... have an airfoil shape, and are spaced apart from each other at an angle of 90 degrees in the circumferential direction, and each guide wall 10 ... is curved in a spiral shape.

The length of each guide wall 10 along the axial direction is the same, and the turning pitch is also the same. And these guide walls 10
For example, 9 from one end to the other end in the axial direction.
It is twisted by an angle of 0 degrees. Therefore, four branch passages 118-lid connecting the first expansion chamber 9 and the gap 7 are formed between these guide walls 1θ, and these branch passages 1'la-lid have a spiral shape. I am doing it.

The inner cylinder 6VC is provided with a single opening 12 opening in the clockwise direction shown in FIG. 3 at one location along the circumferential direction. The opening direction of this opening 12 will be described later, but it is directed toward the upstream side of the spiral flow. Note that the opening edge 13 of the opening 12 is extended by a dimension 1 between 1.0 and 1.0 toward the upstream side. Further, the opening 12 is continuous over the entire length of the inner cylinder 6.

The inside of the inner cylinder 6 forms a second expansion chamber 14, and a cylindrical or cylindrical holder 15 is provided in the center via stays 16+12. There is. A large number of guide wings 18 are placed between the inner cylinder 6 and the holder 15. Each guide vane 18 has a fan shape of about 120 degrees and is spirally twisted in the circumferential direction and the axial direction so that the exhaust flow becomes a spiral flow. Note that the helical pitch of the guide blades 18 is smaller than the helical pitch of the guide walls 1θ.

Such guide blades 18 are arranged in the inner cylinder 6 at equal intervals in the axial direction. Note that all of the above-mentioned members of this embodiment are formed from rolled steel plates or stainless steel. Further, the cross-sectional area of the gap 7 is larger than the cross-sectional area of the chamber inlet 4. Furthermore, the axial length of the gap 7 is such that the spiral flow can rotate once.

The operation of the embodiment with such a configuration will be explained.

The exhaust gas emitted from the engine is guided into the muffler through the inlet 4 as a pulsating pressure wave. The exhaust pressure wave flowing in from the inlet 4 is once expanded in the first expansion chamber 9. Then, it flows from this first expansion chamber 9 into the gap 7 through the branch passages 11h to lld. At this time, the branch passages 11h to 1
1d is divided by the guide walls 10..., so the exhaust flow flowing from the expansion chamber 9 toward the gap 7 is divided into, for example, four streams, and each branch flow is divided into four streams.
Since 1h to lld have a spiral shape, the flow is converted into a spiral flow. Note that each branch flow is sequentially contracted while passing through the branch flow passages 11a to 11d.

The spiral flow passing through each branch passage 11a to lld is
The fluid enters the gap 7 and is turned into a spiral flow by the inertial flow. By the way, the above-mentioned branch passage is divided into four passages along the circumferential direction, and on the other hand, a single opening 12 is opened in the inner cylinder 6 in the circumferential direction. . Therefore, the distances from the downstream ends of the respective branch passages 1L to 1D to the openings 12 are different.

That is, assuming that a spiral flow occurs in the counterclockwise direction as shown by arrow A in FIG. Therefore, the branch passage 11d is the farthest distance from the opening 12 along the counterclockwise direction.

Therefore, among the defecation which has been divided by the above-mentioned division passages 11 and given a spiral circulation flow, the exhaust branch flow that has passed through the division passage 11a reaches the opening 12 the earliest. Since the opening 12 is opened in the upstream direction of the swirling flow shown by the arrow A, the exhaust branch flow is branched at the opening edge 13 in the opening 12, and the portion 1.1 follows the opening 12 and flows into the inner cylinder 6. One part of the exhaust gas flows into the second expansion chamber 14. When entering this inner cylinder 6, the exhaust gas branch is expanded. Then, the exhaust gas branching that has passed through the branching passage 11b reaches the opening 1 with a phase delay of about 90 #' than the exhaust branching that has passed through the dividing passage 11a.
2 and flows into the inner cylinder 6 through this opening Z2. Similarly, the extracted partial flow that has passed through the divided flow passage 11c with a phase of 90 degrees flows into the inner cylinder 6 from the opening 12. Furthermore, the exhaust gas branch that has passed through the branch passage 11d is connected to the passage Jlc.
The branch flow that has passed through also reaches the opening 12 with a delay of 90 degrees.

Therefore, the timing of each branch flow is shifted from the opening 12.
Since the phase changes, the phase of the expansion timing is generated.

Furthermore, the opening 1 passes through each branch passage 11a to Ild.
In each branched flow that reaches 2, the opening 12 is opened along the axial direction, but these branched flows are spiral flows, so in each branched flow, the flow closer to the left side in Fig. 1 is directed to the right side. This means that the flow reaches the opening 12 earlier than the flow that is closer to the flow, causing it to expand.

Each branched flow thus expanded by flowing into the inner cylinder 6 becomes a spiral flow and heads toward the discharge port 5 while being guided by the guide blades 18 . At this time, since the helical pitch of the guide blades 18 is smaller than that of the guide wall 10, the helical pitch in the inner cylinder 6 becomes smaller. This means that the spiral flow flowing in from the left end in Figure 1 turns 5 to 6 times before reaching the discharge port 5 at the right end, so the length of the spiral flow path becomes longer. Among the swirling flows that flow into the inner cylinder 6 through the opening 12 from the gap 7, the swirling flow that flows from the left end in FIG. 1 takes a long time to reach the discharge port 5. The swirling flow that flows into the inner cylinder 6 from the left end through the opening 12 is discharged from the discharge port 5 to the atmosphere first, and the swirling flow that flows from the left end is discharged from the discharge port 5 last.

According to such a silencer, the exhaust pulsating pressure waves emitted from the engine are once expanded in the first expansion chamber 9, and then contracted in the process of flowing through the branch passages 11a to 11d. When it flows into the second expansion chamber 14 of No. 6, it is expanded again. In other words, the pressure waves are attenuated by the two-stage expansion.

In addition, the exhaust flow is divided into, for example, four flows, and each of these divided flows flows into the inner cylinder 6 through the opening 12 at different timings, thereby causing a phase in the expansion timing of each. The single exhaust pulsating pressure flow P shown in is composed of four mutually out-of-phase pressure waves P r
+ P2 *Attenuated to P3 and P4. Moreover,
Since the opening 12 is opened along the axial direction and the divided flow is a spiral flow, a single divided flow flows into the opening 12 sequentially from the left side of FIG. 1 to the right side, and the expansion timing is adjusted. Continuously changing.

This means that the waveforms of pressure waves P1 to P4 in FIG. 4 are gently continuous, resulting in a constant pressure flow as shown by characteristic B. Therefore, since the pulsating flow is converted into a constant pressure flow, the silencing ability is extremely high. Note that the pressure wave P1 shown in FIG. indicates the second branch passage 11b, P3 indicates the third branch passage 11c, and P4 indicates the fourth branch passage 11d. The reason why Pi to P4 are in the reverse order in time is that, as mentioned earlier, the first branch flow is caused by the guiding action of the guide blade 180, and the fourth branch flow also flows to the discharge port 5 with a delay. By coming.

The above configuration divides a single exhaust pulsating pressure flow into a plurality of parts by the conical head 8 and the guide wall 10 . . . and generates a spiral flow. 12 to produce a phase in each expansion timing, the number of parts used is small, the structure is simplified, manufacturing is easy, and it can be provided at low cost. Further, since the phase of the expansion timing is shifted, the internal volume of the inner cylinder 6 serving as the second expansion chamber 14 can be made smaller, and the muffler can be made smaller. In other words, despite its small size, the noise reduction ability is large.

Note that by protruding the opening edge 13 of the opening 12 by a dimension l, a part of the spiral flow can be smoothly passed through the inner cylinder 6 through the d11 portion 12.
This is for the purpose of introducing it within the company.

As described in detail above, according to the present invention, the exhaust pulsating pressure flow introduced into the outer cylinder through the inlet is divided by the conical head and the guide wall, and a spiral flow is generated, and each divided swirling flow is divided between the outer cylinder and the inner cylinder. The tubes are rotated within the gap between the tube and the tube, and are introduced into the inner tube through an opening formed in the inner tube, out of phase with each other, and expanded. Therefore, according to this product, in addition to attenuation based on the expansion of pressure waves, exhaust noise can be effectively muffled by shifting the expansion timing of each branch flow to convert it into a constant pressure flow, and the sound muffling ability is extremely high. It became a thing. In addition, a conical head and a spiral guide wall were used to separate the pressure flow and create a spiral flow, and a single opening was provided in the inner cylinder to create a phase difference in the expansion timing.
The structure is simple, the number of parts is small, the assembly requires no effort and can be manufactured at low cost, and furthermore, it is compact, which is extremely convenient for practical use.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and No. 10 is a cross-sectional view of an exhaust silencer, and FIGS. 2 and 3 are line ■-■ in FIG. 1 and II! A sectional view taken along line -1 and FIG. 4 are characteristic diagrams for explaining the action. 1...Outer cylinder, 4...Exhaust inlet, 5...Discharge port,
6... Inner cylinder, 8... Conical head, 10... Guide wall, 12... Opening, 18... Guide wing.

Claims (1)

[Claims] A circular outer cylinder has an exhaust inlet at one end and an outlet at the other end, and an inner cylinder is provided approximately concentrically with the inner peripheral surface of the outer cylinder with a gap between the outer cylinder and the inner peripheral surface of the outer cylinder. , a conical head that faces the exhaust inlet with one end of the inner cylinder closed, and a conical head provided on the conical head to divide the exhaust flow introduced from the inlet into a plurality of flows, and to spiral these divided flows. a plurality of guide walls that convert the circular flow into the gap; a single opening formed in the inner cylinder and opened toward the upstream side of the spiral circular flow in the gap and continuous in the axial direction; An exhaust muffler characterized by comprising a large number of guide vanes provided in a cylinder at equal intervals along the axial direction and sequentially guiding the exhaust gas that has not flowed in from the opening into a discharge port as a spiral flow.