JPH0893442A - Muffler device - Google Patents

Abstract

(57) [Summary] [Objective] To provide a resistance type muffler device capable of effectively reducing air flow noise. [Structure] An upstream side exhaust conduit and a downstream side exhaust conduit are housed in a large volume casing, and a large number of small holes are provided on the outer peripheral surface of each exhaust conduit in the casing. The exhaust gas of the engine is discharged from the small hole of the upstream exhaust pipe into the casing, and the exhaust gas flowing into the casing is flowed into the small exhaust hole of the downstream exhaust pipe into the same pipe to dissipate into the outside air from the tail pipe. Let The diameter of the small holes in the upstream exhaust conduit is preferably 5-6 mm, and the diameter of the small holes in the downstream exhaust conduit is preferably 3-4 mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffler device suitable for being used in an exhaust system of an engine, particularly an engine for a relatively large vehicle such as a truck.

[0002]

2. Description of the Related Art A so-called resistance type muffler device provided in an exhaust system of a conventional engine for a vehicle such as a heavy-duty truck includes one or more units housed in a hollow or elliptic cylindrical main body casing. A large number of small holes are bored on the outer peripheral surface of an exhaust pipe or pipe having a relatively small diameter, and engine exhaust gas flows out from the small holes of the exhaust pipe into a large-volume expansion chamber or exhaust gas chamber in the main casing. Conversely, when the exhaust gas flows from the large-capacity exhaust gas chamber through a large number of small holes into the exhaust pipe, the exhaust gas expands and contracts to reduce the sonic energy of the exhaust sound and reduce the exhaust sound. It is a thing.

Now, an example of a typical structure of a conventional muffler device for a large truck will be described with reference to a perspective view of FIG. 4 and a partial sectional view of FIG. In the drawings, reference numeral 10 generally indicates a muffler device. The muffler device 10 includes an outer cylinder 12 having an appropriate cross-sectional shape such as a circular elliptical shape and an oval shape, and both end portions in the axial direction of the outer cylinder 12 as end plates or. The casing 16 has a hollow cylindrical casing 16 closed by an end plate 14, and an end plate 14 at one end (upstream side) of the casing 16 is provided with an exhaust gas inlet pipe 18 connected to an exhaust pipe of a diesel engine (not shown). An exhaust gas outlet pipe 20 communicating with a tail pipe (not shown) is provided on the end plate 14 at the other end (downstream side) in the axial direction. Further, in the case of the muffler device 10 shown,
A plurality of partition plates 22, 24, 25, and 28 are provided in the casing 16, and the end plates 14 and the partition plates 22 to 28 at both ends in the axial direction face the casing 16 from the upstream side to the downstream side in the axial direction. Room A, Room B, Room C, D in order
The chamber and the E chamber are partitioned and formed.

The exhaust gas inlet pipe 18 extends through the end plate 14 and the partition plate 22 and has its downstream end fixed to the partition plate 24 and closed. Also, the partition plates 22, 24 and 2
5, a plurality of small-diameter communication conduits 26 are provided,
The chamber A and the chamber D are communicated with each other by these communication conduits 26. Further, a large number of small holes 30 are formed on the outer peripheral surface of the exhaust gas inlet pipe 18 in the B chamber, and the partition plate 22 further has a plurality of large-diameter through holes 32 for communicating the A chamber and the B chamber. Is provided. (It should be noted that although not directly related to the present invention, the above-mentioned chamber C is utilized as a resonance chamber that produces a silencing effect in cooperation with a relatively large-diameter through hole provided in one or more communication conduits 26. )

An exhaust conduit 34 is provided so as to penetrate the partition plate 28 and the downstream end plate 14, and the exhaust conduit 34 is provided with a partition plate 36 provided at a substantially central portion in the axial direction of the upstream exhaust conduit. 38 and a downstream side exhaust conduit 40, and the exhaust gas outlet port protruding from the end plate 14 of the downstream side exhaust conduit 40 forms the exhaust gas outlet pipe 20. A large number of small holes 42 for exhaust gas outflow are formed in the outer peripheral surface of the upstream side exhaust conduit 38 which is housed in the E chamber, and are similarly housed in the E chamber of the downstream side exhaust conduit 40. A large number of small holes 44 for inflowing exhaust gas are formed on the outer peripheral surface. (In the figure, the exhaust gas outflow small hole 42 and the exhaust gas inflow small hole 44 are drawn only on a part of the side surface of the conduit, respectively, but they are usually provided over the entire circumferential surface.)

In the case of a muffler device for a large truck, the casing 16, the exhaust gas inlet pipe 18, the communication conduit 26 and the exhaust conduit 34 are usually made of a heat-resistant steel plate having a thickness of about 2 mm, and a small hole is drilled in them. Holes 30, 42 and 44
Generally has a diameter of about 6 mm.

In the muffler device 10, the exhaust gas of a diesel engine (not shown) is exhaust gas inlet pipe 18
Is introduced into the chamber B of a large volume through a large number of small holes 30, and then flows into the chamber A from the through holes 32 provided in the partition plate 22,
A plurality of communication conduits 26 flow into the D chamber. The exhaust gas in the D chamber flows into the conduit from the exhaust inlet 46 of the upstream side exhaust conduit 38, flows from the small holes 42 to the large-volume E chamber, and then from the E chamber to the small holes 44. Through the exhaust gas outlet pipe, that is, from the exhaust gas outlet pipe 20 to a tail pipe (not shown), and is discharged to the outside air from the tail pipe. Mainly, when the exhaust gas flows out from the large number of small holes 30 into the B chamber and also flows out from the large number of small holes 42 into the E chamber, and also from the E chamber through the large number of small holes 44, the downstream side exhaust conduit 40. The sonic energy of the exhaust sound is reduced by the contraction as it flows into the interior.
(Of course, when the exhaust gas flows from the chamber A into the communication conduit 26, contracts, when the exhaust gas flows from the chamber 26 into the chamber D, expansion, D
Although there is also a reduction in acoustic energy due to contraction when flowing into the upstream side exhaust conduit 38 from the chamber, the large number of small holes 30, 42 described above.
And 44, which is relatively significantly smaller than the effect of reducing acoustic energy when passing through. Further, although the effect of reducing acoustic energy can be obtained by using the chamber C as a resonance chamber, it is based on a principle different from that of the resistance silencer targeted by the present invention. Therefore, a more detailed description will be given here. Omit it. )

However, the above-mentioned conventional muffler device 1 provided with a large number of small holes 30, 42 and 44 having a diameter of about 6 mm.
At 0, the flow of exhaust gas through these small holes is complicated by the structural features, and as shown by the arrow in the partially enlarged cross-sectional view of FIG. A swirl is likely to occur on both the inlet side and the outlet side, and airflow noise generated especially in the high engine speed region where the exhaust gas flow rate increases becomes a new problem. Further, recently, as the output of the engine is increased due to the adoption of the supercharger and the exhaust gas flow rate is further increased, the air flow noise tends to be further increased. Therefore, in order to reduce the emission sound emitted to the environment, it is necessary to suppress the generation of airflow noise to the minimum.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and allows exhaust gas of an engine to flow out from a large number of small holes into an exhaust gas chamber having a large volume, and also in the exhaust gas chamber. It is an object of the present invention to effectively reduce the generation of airflow noise in a resistance type muffler device that allows exhaust gas to flow into an exhaust conduit through a large number of small holes.

[0010]

In order to achieve the above object, the present invention provides a hollow cylindrical main body casing having both axial ends closed, and a main casing housed in the main casing.
It has an exhaust gas inlet at one end and is closed at the other end,
An upstream exhaust conduit having a large number of small holes for exhaust gas outflow opening in the body casing on the outer peripheral surface of the portion upstream of the closed end; and an exhaust gas outlet port housed in the body casing and having one end. And a downstream side exhaust conduit having a plurality of small holes for exhaust gas inflow opening in the main body casing on the outer peripheral surface of a portion downstream from the closed end and provided on the upstream side exhaust conduit. The muffler device is characterized in that the diameter of the small hole provided in the downstream exhaust pipe is smaller than the diameter of the small hole. In the present invention, the large number of small holes provided in the upstream exhaust conduit all have substantially the same diameter.
It is preferable that the holes are 6 mm, and that a large number of small holes provided in the downstream exhaust conduit are holes having substantially the same diameter and 3 to 4 mm.

[0011]

According to the present invention, an upstream side exhaust conduit having a large number of small holes for exhaust gas outflow is provided in a hollow cylindrical main body casing, and a downstream side exhaust conduit having a large number of small holes for exhaust gas inflow is provided. By setting the diameter of the small holes of the upstream exhaust conduit larger than the diameter of the small holes of the downstream exhaust conduit, the flow of the exhaust gas flowing into the exhaust gas inflow small holes is It is possible to effectively reduce airflow noise that is likely to occur due to turbulence. Further, the diameter of the large number of small holes for outflowing the exhaust gas is 5 to 6 mm, which is substantially the same as the conventional one.
The diameter of many small holes for inflowing exhaust gas is 3 to 4 mm, which is smaller than the conventional one, and suppresses the deterioration of engine performance due to the increase of the back pressure of the engine while suppressing the air flow noise. The width can be reduced.

[0012]

Embodiments of the present invention will be specifically described below with reference to FIGS. (Note that the same reference numerals are used for members and portions that are substantially the same as or corresponding to those of the conventional muffler device described with reference to FIGS. 4 and 5.) The conceptual cross-sectional view of FIG. Muffler device 10 '
E of the conventional muffler device 10 described above with reference to FIG.
An outer cylinder 12 that corresponds to the chamber portion and has an appropriate closed cross-sectional shape such as a circular shape, an elliptical shape, or an oval shape, and an end plate (end plate) or a partition that closes both axial end portions of the outer cylinder 12. A main body casing 16 including the plates 14 and 28 is provided, and an exhaust gas chamber E having a large volume and being hermetically sealed is formed therein.

An exhaust conduit 34 is provided axially through the body casing 16, and the exhaust conduit 34 is provided with a partition plate 36 disposed at a substantially central portion thereof so that an upstream exhaust conduit 38 and a downstream exhaust conduit 38 are provided. It is divided into 40. The upstream side exhaust conduit 38 has an exhaust gas inflow port 46 at one upstream end thereof, and a large number of small holes 42 for exhaust gas outflow are provided on the outer peripheral surface of the E chamber. Further, a large number of small holes 44 for inflowing exhaust gas are provided on the outer peripheral surface of the downstream side exhaust conduit 40 in the E chamber.

The exhaust gas outflow small hole 42 has a diameter of 5 to 6 mm, and the exhaust gas inflow small hole 44.
Are holes having a diameter of 3 to 4 mm and are arranged in a zigzag pattern as shown in the drawing or in a grid pattern. Further, the small holes 42 and 44 are each a process of punching a plurality of times by a press using a punching punch and a die which cooperate with each other in a flat plate-like material and having two to three rows of punching punches. Thus, a perforated plate having a required number of small holes 42 or 44 is produced, and the circular perforated plate is bent and formed into a cylindrical shape.
Further, the spacing between the rows of small holes 42 and 44 (spacing in the axial direction) and the pitch within each row (spacing in the circumferential direction) are from the viewpoint of press punching technology, namely, the material of the plate-shaped material, the plate thickness It is preferable to set as small as possible within an allowable range in consideration of the hole diameter, the space arrangement of the punch, the durability of the punch, and the like.

As clearly shown in the enlarged sectional view of FIG. 2, the small holes 44 on the exhaust gas inflow side are small holes having a diameter of 3 to 4 mm, and the arrangement pitch thereof is set as small as possible in the press punching technique. As a result, the exhaust gas flow that flows into the downstream exhaust conduit 40 from the small hole 44 can be rectified and the generation of swirl can be suppressed, so that the generation of air flow noise can be effectively reduced.

In FIG. 3, the vertical axis indicates the air flow noise Ns, and the horizontal axis indicates the small hole 44 on the exhaust gas inflow side and the small hole 4 on the exhaust gas outflow side.
The diameter d of 2 was taken, and the hole diameter of each small hole was variously changed to examine the loudness of the air flow sound. In the figure, the solid line Na indicates the air flow sound of the inflow side small hole 44, and as the hole diameter is reduced from the conventional diameter of 6 mm, the air flow sound decreases.
A reduction of about 6 decibels at a hole diameter of 4 mm and a reduction of about 5 decibels at a hole diameter of 4 mm was observed. When the hole diameter is 3 mm or less, the air flow noise is further reduced, but in the case of press punching, which has a low production cost, it is actually extremely difficult to machine from the viewpoint of the plate thickness of the material, the spatial arrangement of punches, and the durability of the punch, and the manufacturing cost is significantly It is not suitable for practical use because it has no choice but to rely on expensive drilling, and the hole diameter of the small holes 44 is 3 to 4 in consideration of the reduction efficiency of air flow noise, manufacturing technology, cost, and the like.
mm is suitable, and particularly preferably 3 mm. Also, the dotted line Nb in the figure indicates the air flow sound of the outflow side small hole 42, and by reducing the hole diameter from 6 mm of the conventional type to 5 mm, a slight reduction of the air flow sound of about 2 decibels can be obtained, but the hole diameter is further reduced. However, it was confirmed that such a reduction effect could not be obtained. Therefore, setting the hole diameter of the small hole 42 on the outflow side to 5 mm or less unnecessarily increases the back pressure of the engine and lowers the engine performance. It is appropriate to set the limit of the press punching technology, the manufacturing cost, etc. to 5 to 6 mm, and particularly 6 mm as in the conventional case. In addition, the test of the above-mentioned airflow sound is performed by the reference numeral N in FIG.
As schematically shown above a and below Nb, the upstream exhaust conduit 38 and the E chamber, and the downstream exhaust conduit 40 and the E chamber are made as separate test devices, respectively, and This is a measurement of airflow noise by connecting to the exhaust system of the engine. Based on the above test results, the diameter of the small hole 42 for exhaust gas outflow was 6 mm, and the diameter of the small hole 44 for exhaust gas inflow was 3 mm, and the resistance muffler device 1 shown in FIG.
When 0'is connected to the exhaust system of a heavy-duty diesel engine, a real machine test is conducted.
Decibels, a reduction of 2 decibels in the final exhaust sound was achieved.

In the embodiment shown in FIG. 1, the partition plate 36 is provided in the single exhaust pipe 34 so that the exhaust pipe 3 on the upstream side is provided.
8 and the downstream side exhaust conduit 40 are formed, the upstream side exhaust conduit 38 and the downstream side exhaust conduit 40 are axially divided into completely separate conduits which are arranged with a space in between. be able to. Further, the resistance type muffler device 1 shown in FIG.
0 ′ is, for example, a conventional muffler device 1 shown in FIG.
Like 0, it can be arranged in the common casing 16 in combination with a resonance chamber or the like.

[0018]

As described above, according to the muffler device of the present invention, a hollow cylindrical main body cable whose both axial ends are closed and the main body casing are housed in the main body casing, and the exhaust gas inlet port is provided at one end. And an upstream exhaust conduit having the other end closed, and a large number of small holes for exhaust gas outflow opening in the main body casing on the outer peripheral surface of a portion upstream from the closed end,
A large number of small holes for inflowing exhaust gas, which are housed in the main body casing, have an exhaust gas outlet at one end and are closed at the other end, and open in the main body casing on the outer peripheral surface of a portion downstream from the closed end. With a downstream exhaust conduit having
The diameter of the small holes provided in the downstream exhaust conduit is smaller than the diameter of the small holes provided in the upstream exhaust conduit, and the small holes provided in the upstream exhaust conduit are further provided. 5-6m with all holes having substantially the same diameter
m, and the large number of small holes provided in the exhaust pipe on the downstream side are all 3 to 4 mm with substantially the same diameter, so that the exhaust noise of diesel engines such as large trucks, especially muffler Airflow noise generated in the device can be effectively reduced without sacrificing extraordinary increase in manufacturing cost, deterioration of engine performance, etc., which is beneficial for environmental improvement.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a state of an exhaust gas flow flowing through an exhaust gas inflow small hole 44 in FIG.

FIG. 3 is a diagram showing the relationship between the air flow noise of the muffler device shown in FIG. 1 and the diameters of small holes 42 and 44.

FIG. 4 is a perspective view showing a muffler device provided in an exhaust system of a conventional heavy-duty truck diesel engine.

5 is an exhaust gas inlet pipe 18 of the muffler device shown in FIG.
And small holes 30, 42 and 44 provided in the exhaust conduit 34.
FIG. 3 is an enlarged cross-sectional view showing a streamline of exhaust gas passing through the exhaust passage.

[Explanation of symbols]

10, 10 '... Muffler device, 16 ... Casing and main body casing, 20 ... Exhaust gas outlet, 34 ... Exhaust conduit,
38 ... Upstream exhaust conduit, 40 ... Downstream exhaust conduit, 42 ...
Exhaust gas outflow small holes, 44 ... Exhaust gas inflow small holes,
46 ... Exhaust gas inlet.

Claims (2)

[Claims] 1. A hollow-cylindrical main body casing having both axial ends closed, and a main casing housed in the main casing.
It has an exhaust gas inlet at one end and is closed at the other end,
An upstream exhaust conduit having a large number of small holes for exhaust gas outflow opening in the body casing on the outer peripheral surface of the portion upstream of the closed end; and an exhaust gas outlet port housed in the body casing and having one end. And a downstream side exhaust conduit having a plurality of small holes for exhaust gas inflow opening in the main body casing on the outer peripheral surface of a portion downstream from the closed end and provided on the upstream side exhaust conduit. A muffler device characterized in that a diameter of a small hole provided in a downstream exhaust pipe is smaller than a diameter of the small hole. 2. The large number of small holes provided in the upstream side exhaust conduit are all holes having substantially the same diameter and 5 to 6 mm, and the large number of small holes provided in the downstream side exhaust conduit are all provided. The muffler device according to claim 1, wherein the holes have substantially the same diameter and have a diameter of 3 to 4 mm.