JPH0141853Y2 - - Google Patents

Description

[Detailed explanation of the idea] B Industrial application field The present invention relates to a silencer for an internal combustion engine.

(b) Prior art Normally, in internal combustion engines, when the engine speed is low, it is not a big problem to reduce the back pressure and improve the engine output, but on the other hand, the exhaust noise is high, so it is difficult to muffle the engine. Action is required. Also, when the engine speed is high, the effect of exhaust noise on the driver is relatively small, so silencing is not a big problem. There is a need.

Conventionally, engine exhaust gas in all engine speed ranges, regardless of whether the engine is in the low or high speed range, always flows into the muffler through one exhaust inflow path and always passes through the same flow path within the muffler. In a silencer that is designed to reduce noise, if emphasis is placed on improving noise reduction performance, the back pressure suppression performance will decrease and this will hinder the improvement of engine output. There was a problem that the noise reduction performance and back pressure suppression performance could not be satisfied in the entire rotation range.

C. Purpose of the invention In view of the above, the present invention is designed to distribute exhaust gas through an exhaust flow path with the main purpose of silencing effect in the low speed range of the engine, and to suppress back pressure in the high speed range of the engine. It is an object of the present invention to propose a muffling device that allows exhaust gas to flow through an exhaust flow path and satisfies muffling performance and back pressure suppression performance over the entire rotation range of an engine.

D. Structure and Examples of the Invention In order to achieve the above object, the present invention provides a bench lily part 3 in the exhaust pipe 2 from the engine to the muffler 1, and extends the exhaust pipe 2 in a straight line downstream from the vent lily part 3. A main exhaust inflow path 4 and a sub exhaust inflow path 5 branching from the exhaust pipe 2 are provided, and the exhaust pipe 2 is further provided with a bypass path 6 that bypasses the bench lily portion 3, and the upstream side of the bypass path 6 is open upstream of the bench lily portion 3. The silencer 1 is provided with an opening so that the downstream side thereof is directed toward the opening 5a of the sub-exhaust inflow passage 5, and furthermore, within the silencer 1, there is a main exhaust passage 7 whose main purpose is to have a silencing effect, and a main exhaust passage 7 which has a back pressure suppressing effect. A sub-exhaust flow path 8 is provided whose main purpose is to communicate the inflow side of the main exhaust flow path 7 with the main exhaust inflow path 4, and communicate the inflow side of the sub-exhaust flow path 8 with the sub-exhaust flow path 5. It is characterized by the fact that In the embodiment shown in the drawings, the main exhaust flow path 7 whose main purpose is a silencing effect is configured such that its rear part communicates with each expansion chamber 9 in the muffler 1, and the main exhaust flow path 7 is configured to communicate with each expansion chamber 9 in the muffler 1. Exhaust noise is muffled and the exhaust is discharged from the exhaust inner cylinder 10 to the outside. Furthermore, the sub-exhaust flow path 8 whose main purpose is to suppress back pressure is configured such that the exhaust gas flowing out from this path immediately flows into the exhaust inner cylinder 10 without flowing into the resonance generating chamber 9 of the muffler 1. , so that back pressure does not exert a large effect on the exhaust.

E. Effect When the engine is in a low rotation range, the exhaust volume from the engine is small, so the exhaust gas passes straight through the exhaust pipe 2 through the bench lily part 3 of the exhaust pipe 2, and goes straight through the main exhaust inflow path 4. As shown in the dotted line in the figure, Then, the exhaust gas flows from the main exhaust flow path 7 into the exhaust inner cylinder 10 through each resonance generating chamber 9 in the muffler 1, and is discharged to the outside. Exhaust noise is muffled by flowing into each expansion chamber 9. At this time, back pressure is not suppressed very much, but back pressure suppression does not need to be much of a problem in the low rotational speed range of the engine. Furthermore, when the engine is in a high rotation range, the exhaust amount from the engine increases, so the flow of the exhaust gas is suppressed by the bench lily part 3, and a part of the exhaust gas is transferred from the inlet 6a to the bypass path 6.
The exhaust gas is ejected from the downstream outlet port 6a toward the inlet port 5a of the sub-exhaust gas inlet path 5. Therefore, the exhaust gas that has passed through the bench lily portion 3 is diverted to the sub-exhaust gas inflow path 5 as shown by the solid line in the figure by the ejection force of the exhaust gas ejected from the bypass path 6. Therefore, the exhaust gas from the engine passes through the sub-exhaust inflow path 5, flows into the sub-exhaust flow path 8 in the muffler 1, and immediately flows into the exhaust inner cylinder 10 without flowing into the expansion chamber 9 in the muffler 1. and is discharged to the outside. Therefore, in the high rotation range of the engine, back pressure is reduced and the output of the engine can be improved.
Although the silencing effect is not very effective at this time,
In the high speed range of the engine, the effect of exhaust noise on the driver is relatively small, so silencing is not much of a problem.

F. Effect of the invention As described above, according to the invention, the noise reduction effect can be exhibited well in the low rotation range of an engine where emphasis is placed on the noise reduction effect, and the back pressure Since the suppressing effect can be exhibited satisfactorily, the silencing performance and back pressure suppressing performance can be satisfied over the entire rotation range of the engine. Moreover, it has the advantage that the exhaust flow path can be changed automatically and with a simple structure using the exhaust gas in the low speed range and the high speed range of the engine.

[Brief explanation of the drawing]

The drawing is an exhaust system diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Silencer, 2... Exhaust pipe, 3... Bench lily part, 4... Main exhaust inflow path, 5... Subexhaust exhaust inflow path, 6... Bypass path, 7... Main exhaust flow path, 8...
...Sub-exhaust flow path.

Claims (1)

[Scope of utility model registration request] An exhaust pipe 2 leading from the engine to the muffler 1 is provided with a bench lily part 3, and downstream of the bench lily part 3 of the exhaust pipe 2 are a main exhaust inflow path 4 that is straight, and a sub exhaust inflow path 5 that branches from the exhaust pipe 2. Furthermore, the exhaust pipe 2 is provided with a bypass passage 6 that bypasses the bench lily portion 3.
The upstream side thereof opens upstream of the bench lily part,
The muffler 1 has a main exhaust flow path 7 whose downstream side is oriented toward the opening 5a of the sub-exhaust inflow path 5, and a main exhaust flow path 7 whose main purpose is to have a silencing effect, and a main exhaust flow path whose main purpose is to suppress back pressure. A target sub-exhaust flow path 8 is provided, the inflow side of the main exhaust flow path 7 is communicated with the main exhaust inflow path 4, and the inflow side of the sub-exhaust flow path 8 is connected to the sub-exhaust flow path 5.
A silencer for an internal combustion engine, characterized in that it communicates with the silencing device.