JP4252869B2 - Engine exhaust system - Google Patents

Description

  The present invention relates to an exhaust device through which exhaust gas discharged from an engine for automobiles and the like flows, and more particularly, to an exhaust device capable of obtaining excellent silencing performance in both the low speed and high speed rotation regions of the engine. is there.

  An exhaust system connected to an engine for automobiles, etc. is connected to an exhaust port of the engine to introduce exhaust gas exhausted from the engine and exhaust it to the atmosphere, and an exhaust noise interposed in the exhaust pipe In such an exhaust system, in the case of a low-speed rotation range including engine start and idling rotation, the smaller the exhaust pipe diameter and the longer the length, the more advantageous for noise reduction. Further, it is generally known that, in the case of the high speed rotation region of the engine, the exhaust pipe having a larger diameter and shorter length has a smaller exhaust resistance and is advantageous for improving the engine output.

Therefore, conventionally, an opening / closing valve 23 is provided in the silencer 10, and by opening / closing control of the opening / closing valve 23, an exhaust gas path that is advantageous for silencing in the low-speed rotation region of the engine and an output improvement in the high-speed rotation region of the engine. An exhaust device that can be switched to an advantageous exhaust gas path is already known (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-153019

  However, the one disclosed in Patent Document 1 compares the diameter of the exhaust pipe downstream of the silencer so that the flow rate of the exhaust gas in the high-speed rotation region of the engine can be satisfied when the open / close valve is opened. Therefore, there is another problem that it is difficult to enhance the silencing effect when the on-off valve is closed, that is, in the low speed rotation region of the engine.

  The present invention has been proposed in view of such circumstances, and an object of the present invention is to provide a novel engine exhaust system that solves the above-described problems.

In order to achieve the above object, according to the first aspect of the present invention, a silencer is interposed in an exhaust pipe through which exhaust gas from an engine flows, and an exhaust pipe downstream of the silencer is connected to the first exhaust through a branching portion. An on-off valve that branches into a pipe and a second exhaust pipe, and is maintained in a closed position in the low-speed rotation region of the engine and in an open position in the high-speed rotation region, in one of the first exhaust pipe and the second exhaust pipe The exhaust gas flows through only one of the first exhaust pipe and the second exhaust pipe in the low engine speed range, and flows in both of them in the high speed engine speed range. In the exhaust system ,
Of the first exhaust pipe and the second exhaust pipe, the exhaust pipe on the side where the on-off valve is provided has an on-off valve provided on the peripheral wall of the exhaust pipe so that it can be opened and closed in the radial direction. A downstream end of the cap is closed with a cap, and a dead-end resonance pipe communicating with the on-off valve is formed on the upstream side of the cap, and the portion of the exhaust pipe provided with the on-off valve and the resonance pipe is surrounded by a sealed outer cylinder. The outer cylinder communicates with the atmosphere .

  In order to achieve the above object, the invention according to claim 2 is the invention according to claim 1, wherein the exhaust pipe on the side of the first exhaust pipe and the second exhaust pipe provided with the on / off valve is provided with an on / off valve. It is characterized by having a larger diameter than the exhaust pipe on the non-existing side.

  According to the first aspect of the present invention, the diameter of the exhaust pipe downstream of the silencer in the low speed rotation region of the engine can be formed smaller than the diameter of the exhaust pipe downstream of the silencer in the high speed rotation region. Therefore, the silencing performance in the low-speed rotation range of the engine can be greatly improved.

In addition, in the low-speed rotation region of the engine, the dead end passage from the branch portion to the on-off valve in the exhaust pipe on the side where the on-off valve is provided can be a resonance pipe. As a result, exhaust noise can be further reduced.

  According to the second aspect of the present invention, the exhaust pipe on the side of the first exhaust pipe and the second exhaust pipe on the downstream side of the silencer where no on-off valve is provided is connected to the exhaust pipe on the side on which the on-off valve is provided. By reducing the diameter of the engine, the difference in the flow rate of the exhaust gas flowing downstream from the silencer can be further increased between the low-speed rotation range of the engine and the high-speed rotation range. The characteristics can be further improved.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below based on examples of the present invention shown in the accompanying drawings.

  First, a first embodiment of the present invention will be described with reference to FIGS.

  1 is an overall perspective view of the exhaust system of the present invention, FIG. 2 is an enlarged sectional view taken along line 2-2 in FIG. 1, FIG. 3 is a sectional view taken along line 3-3 in FIG. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG.

  In FIG. 1, an exhaust pipe 1 through which exhaust gas discharged therefrom is connected is connected to an automobile engine E. The exhaust pipe 1 extends in the longitudinal direction of the vehicle body of the automobile, and the downstream side of the exhaust pipe 1 is branched into a first exhaust pipe 11 and a second exhaust pipe 12 via a branch portion 2. A primary silencer (pre-chamber) M1 and a secondary silencer M2 are interposed in the exhaust pipe 1 upstream of the branch portion 2 from the upstream side to the downstream side. The first exhaust pipe 11 is formed in a straight shape, and its downstream end is opened to the atmosphere, and the second exhaust pipe 12 is also formed in a straight shape and its downstream end is opened to the atmosphere. The first exhaust pipe 11 and the second exhaust pipe 12 are formed to have substantially the same diameter, and they are smaller in diameter than the exhaust pipe 1.

  The primary silencer M1 and the secondary silencer M2 are both of a conventionally known structure, and thus detailed description thereof is omitted.

  As shown in FIGS. 2 to 4, a butterfly valve V as an on-off valve is provided in the middle of the second exhaust pipe 12. The portion of the first exhaust pipe 12 provided with the butterfly valve V is surrounded by a cylindrical outer cylinder 20 concentric with the second exhaust pipe 12, and the front and rear opening edges of the outer cylinder 20 and the second exhaust pipe The outer peripheral surface of the pipe 12 is closed by front and rear end plates 21 and 22, and an annular exhaust gas flow passage 24 is formed between the second exhaust pipe 12 and the outer cylinder 20. A rectangular valve port 25 communicating with the exhaust gas flow passage 24 is opened in the peripheral wall of the second exhaust pipe 12, and an outer mesh plate 27 having an inner mesh plate 26 laminated on the inner surface around the valve port 25. The outer edge is spot welded. Further, a stay 28 having a U-shaped cross section is welded to the outer peripheral surface of the second exhaust pipe 12 so as to straddle the valve opening 25 from the front and rear, and the valve opening 25 is attached to the front and rear end edges of the stay 28. A valve body 30 having an arcuate surface shape for opening and closing is supported by a valve shaft 31 so as to be freely opened and closed. Between the stay 28 and the valve body 30, a valve spring 32 made of a torsion spring wound around the valve shaft 31 is provided, and the elastic force of the valve spring 32 urges the valve body 30 in the closing direction. is doing. When the exhaust gas pressure flowing through the second exhaust pipe 12 becomes higher than the resilience of the valve spring 32, the valve body 30 is opened. A cap 33 that closes the flow path of the second exhaust pipe 12 is fixed to the downstream side of the valve body 30 of the second exhaust pipe 12, and a number of punch holes 34 are further provided downstream of the cap 33. The exhaust gas is opened and the exhaust gas in the exhaust gas flow passage 24 is discharged to the atmosphere through these punch holes 34.

  Next, the operation of this embodiment will be described.

  Exhaust gas generated by the rotation of the engine E flows to the exhaust pipe 1. The exhaust gas flowing through the exhaust pipe 1 passes through the primary silencer M1, is primarily silenced, passes through the secondary silencer M2, is secondarily silenced, and is discharged to the atmosphere.

By the way, in the low speed rotation range including the idling rotation and the start rotation of the engine E, the combustion pressure of the engine E is low and the pressure of the exhaust gas discharged from the engine E is low. Since the valve, that is, the valve closing force of the butterfly valve V by the valve spring 32 is weaker, the valve V maintains the closed state. Therefore, the exhaust gas flowing through the exhaust pipe 1 flows through the first exhaust pipe 11 via the branch portion 2 as shown by the solid line arrow in FIG. 4 , but does not flow into the second exhaust pipe 12, and all of the exhaust gas is exhausted. It flows from the pipe 1 through the branch part 2 to the first exhaust pipe 11 and is discharged to the atmosphere. At this time, since the exhaust gas flows through the first exhaust pipe 11 from the exhaust pipe 1 and flows through the exhaust passage having a long overall length and a small passage area, the exhaust gas is exhausted in the low speed rotation region of the engine. Noise can be reduced efficiently, and in addition, a part of the exhaust gas bypasses a dead end passage from the branch part 2 to the on-off valve V in the second exhaust pipe 12 as shown by the solid line arrow in FIG. Since it flows, this dead-end passage becomes a resonance tube, which exhibits a resonance attenuation effect on the exhaust gas, and can further reduce the exhaust noise.

  On the other hand, when the combustion of the engine E is in a complete explosion state and reaches the high speed rotation range, the combustion pressure increases, and the pressure of the exhaust gas exhausted therefrom also increases, so that the exhaust gas flowing through the exhaust pipe 1 The pressure becomes higher than the closing force of the valve spring 32 of the butterfly valve V, and the valve V is closed. Therefore, the exhaust gas flowing through the exhaust pipe 1 flows through the branch portion 2 in a branched manner to the first exhaust pipe 11 and the second exhaust pipe 12. The exhaust gas flowing through the second exhaust pipe 12 is discharged from the opened butterfly valve V through the punch hole 34 to the atmosphere as shown by the two-dot chain line arrow in FIG. At this time, since the exhaust gas flows through the first and second exhaust pipes 11 and 12 from the exhaust pipe 1 and flows through the exhaust passage having a large passage area as a whole, the exhaust gas in the high-speed rotation region of the engine. The exhaust resistance can be efficiently reduced.

  Next, a second embodiment of the present invention will be described with reference to FIGS.

  FIG. 5 is an overall perspective view of the exhaust system of the present invention, and FIG. 6 is an enlarged cross-sectional view taken along line 6-6 of FIG. 5, and the same reference numerals are given to the same elements as those in the first embodiment.

  In the second embodiment, the downstream part of the first exhaust pipe 11 and the second exhaust pipe 12 is surrounded by an outer cylinder 120. The outer cylinder 120 is composed of an outer shell 121 having an elliptical cylindrical shape and its front and rear. Before closing the opening end, the rear end plates 122 and 123 are formed in a more sealed elliptical cylinder shape, and the exhaust gas flow passage 124 side is formed between the outer cylinder 120 and the first exhaust pipe 11. Further, a support plate 125 parallel to the rear end plate 123 is fixed near the rear portion in the outer cylinder 120, and a plurality of communication holes 126 communicating with the front and rear thereof are formed in the support plate 125. The rear end plate 123 supports the front portion of one tail pipe 127 so that the downstream end of the tail pipe 127 is open to the atmosphere.

  The downstream portion of the straight first exhaust pipe 11 is inserted into the outer cylinder 120 and is integrally penetrated and supported by the front end plate 122 and the support plate 125, and the downstream end thereof is connected to the tail pipe 127. Direct communication. Further, the downstream portion of the second exhaust pipe 12 provided with the opening / closing valve V is also inserted into the outer cylinder 120 and is integrally penetrated and supported by the front end plate 122 and the support plate 125. It is accommodated in the cylinder 120. The downstream end of the second exhaust pipe 12 is closed by a cap 133. As shown in FIG. 6, the second exhaust pipe 12 is formed with a larger diameter than the first exhaust pipe 11. The on-off valve V is the same as that of the first embodiment. When the on-off valve V is closed, the second exhaust pipe 12 becomes a dead end passage to block the flow of exhaust gas, and when opened, the exhaust gas is exhausted. As shown by a two-dot chain line in FIG. 6, the exhaust gas passes through the exhaust gas flow passage 124 in the outer cylinder 120 and is discharged to the atmosphere through the tail pipe 127.

In the low-speed rotation region of the engine E, as described above, the butterfly valve V maintains the closed state, so that the exhaust gas flowing through the exhaust pipe 1 flows through the first exhaust pipe 11 via the branch portion 2, The exhaust gas does not flow to the second exhaust pipe 12, but all of the exhaust gas flows from the exhaust pipe 1 to the first exhaust pipe 11 and is discharged to the atmosphere. At this time, the exhaust gas flows from the exhaust pipe 1 through the first exhaust pipe 11 as in the first embodiment, and exhaust gas exhaust noise in the low-speed rotation region of the engine can be efficiently reduced. In the second embodiment, the diameter of the first exhaust pipe 11 can be set to be smaller than the diameter of the second exhaust pipe 12, and the noise reduction performance of the exhaust noise in the low speed rotation region of the engine can be further enhanced.
In addition, as in the first embodiment, the dead end passage from the branching portion 2 to the on-off valve V in the second exhaust pipe 12 can be a resonance pipe, and exhibits a resonance damping effect on the exhaust gas, Noise can be further reduced.

  On the other hand, in the high-speed rotation region of the engine E, the butterfly valve V is closed as in the first embodiment. Therefore, the exhaust gas flowing through the exhaust pipe 1 flows through the branch portion 2 to the first exhaust pipe 11 and the second exhaust pipe 12 and flows through the exhaust passage having a large passage area. The exhaust resistance of the exhaust gas in the rotation region can be efficiently reduced.

  As mentioned above, although the Example of this invention was described, this invention is not limited to the Example, A various Example is possible within the scope of the present invention.

  For example, in the above-described embodiment, the case where the on-off valve V is provided in the second exhaust pipe 12 has been described. However, this may be provided in the first exhaust pipe 11, and in this case, it does not correspond to the second embodiment. The diameter of the first exhaust pipe 11 is made larger than the diameter of the second exhaust pipe 12. In the above-described embodiment, the case where the on-off valve V is constituted by a butterfly valve has been described. However, this may be constituted by a reed valve or other valves having the same function.

Overall perspective view of exhaust system of the present invention (first embodiment) FIG. 1 is an enlarged sectional view taken along line 2-2 of FIG. 1 (first embodiment). Sectional view along line 3-3 in FIG. 2 (first embodiment) Sectional view along line 4-4 in FIG. 3 (first embodiment) Overall perspective view of the exhaust system of the present invention (second embodiment) FIG. 5 is an enlarged sectional view taken along line 6-6 (second embodiment).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Exhaust pipe 2 ... Branch part 11 ... 1st exhaust pipe 12 ... 2nd exhaust pipe
20 ... outer cylinder
33 ... Cap
120 ...
133 ··· Cap E ··· Engine M2 · · · Silencer (second silencer)
V ... Open / close valve (butterfly valve)

Claims (2)

A silencer (M2) is interposed in the exhaust pipe (1) through which the exhaust gas from the engine (E) flows, and the exhaust pipe (1) downstream of the silencer (M2) is connected via the branch (2). The first exhaust pipe (11) and the second exhaust pipe (12) are branched, and either the first exhaust pipe (11) or the second exhaust pipe (12) is connected to the engine (E) at a low speed rotation range. An on-off valve (V) that is maintained in the closed position and in the open position in the high-speed rotation region is provided. 12) In the exhaust system of the engine, which flows through only one of the other, and flows both (11, 12) in the high speed rotation region of the engine (E) ,
Of the first exhaust pipe (11) and the second exhaust pipe (12), the exhaust pipe (12) on the side where the on-off valve (V) is provided has the on-off valve (V) on the peripheral wall of the exhaust pipe (12). It is provided so that it can be opened and closed in the radial direction, and the downstream side of the on-off valve (V) is closed by a cap (33, 133), and the on-off valve (V A dead-end resonance pipe that communicates with the exhaust pipe (12) is formed, and a portion of the exhaust pipe (12) provided with the on-off valve (V) and the resonance pipe is surrounded by a sealed outer cylinder (20, 120). 20, 120) An exhaust system for an engine characterized in that the interior thereof communicates with the atmosphere .   Of the first exhaust pipe (11) and the second exhaust pipe (12), the exhaust pipe (12) on the side where the on-off valve (V) is provided is connected to the exhaust pipe (11) on the side where the on-off valve (V) is not provided. 2. The exhaust system for an engine according to claim 1, wherein the exhaust system has a larger diameter.

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