JP2005090334A - Engine exhaust system - Google Patents

Abstract

【The invention's effect】
PROBLEM TO BE SOLVED: To improve a noise reduction performance in an engine exhaust device in a low speed rotation region.
An exhaust pipe (1) through which exhaust gas from an engine (E) flows is branched into a first exhaust pipe (11) and a second exhaust pipe (12) via a branch part (2), and an opening / closing valve (V) is provided on the first exhaust pipe (11). A silencer M2 is provided in the second exhaust pipe 12, and the on-off valve V is closed in the low speed rotation region of the engine E to exhaust the exhaust gas to the atmosphere only from the second exhaust pipe 12, and the open / close valve V is discharged in the high speed rotation region of the engine E. Is an engine exhaust device that exhausts exhaust gas from both exhaust pipes of the first exhaust pipe 11 and the second exhaust pipe 12 to the atmosphere, and branches in the first exhaust pipe 11 when the on-off valve V is closed. A resonance tube for the exhaust gas is configured from the portion 2 to the on-off valve V.
[Selection] Figure 1

Description

  The present invention relates to an exhaust device through which exhaust gas discharged from an engine for vehicles or the like flows.

Conventionally, an exhaust pipe through which exhaust gas discharged from an engine exhaust port flows is branched into a first exhaust pipe 9 and a second exhaust pipe 10, and an on-off valve 3 is provided in the first exhaust pipe 9, and a second The silencer 6 is interposed in the exhaust pipe, and the on-off valve 3 is closed and the exhaust gas is exhausted from the second exhaust pipe 10 to the atmosphere only in the low-speed rotation region of the engine, and the on-off valve 3 is opened in the high-speed rotation region of the engine. An exhaust device that exhausts exhaust gas to the atmosphere from both the first exhaust pipe 9 and the second exhaust pipe 10 is known (for example, see Patent Document 1).
Utility Model Registration No. 3074863

  However, what is disclosed in Patent Document 1 is that the on-off valve 3 provided in the first exhaust pipe 9 is positioned immediately after the branching portion with the second exhaust pipe 10, so that the on-off valve 3 is closed. There is a problem that the first exhaust pipe 9 on the downstream side of the on-off valve 3 is not effectively utilized for the exhaust gas silencing action.

  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, an exhaust pipe through which exhaust gas from an engine flows is branched into a first exhaust pipe and a second exhaust pipe via a branch portion, and the first exhaust pipe is formed. An on-off valve is provided, and a silencer is provided on the second exhaust pipe. The on-off valve is closed in the low-speed rotation range of the engine and exhaust gas is discharged from the second exhaust pipe to the atmosphere. An engine exhaust device that opens a valve and exhausts exhaust gas from both the exhaust pipes of the first exhaust pipe and the second exhaust pipe to the atmosphere,
When the on-off valve is closed, a resonance pipe for the exhaust gas is formed in a portion from the branch portion to the on-off valve in the first exhaust pipe.

  When the on-off valve is closed in the low-speed rotation region of the engine, the flow of the exhaust gas is allowed in the portion from the branch portion of the first exhaust pipe with the second exhaust pipe to the on-off valve, Since the resonance tube which provides the resonance damping action is configured, the noise reduction performance in the low speed rotation region of the engine 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.

  In the accompanying drawings, FIG. 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, and FIG. 3 is a sectional view taken along line 3-3 in 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. The downstream side of the exhaust pipe 1 is bifurcated into a first exhaust pipe 11 and a second exhaust pipe 12 via a branch portion 2. The pipe 11 is formed longer than the second exhaust pipe 12. A primary muffler (pre-chamber) M1 is interposed in the middle of the exhaust pipe 1 upstream of the branch part 2, and a butterfly as an on-off valve is provided at the rear of the first exhaust pipe 11, that is, downstream thereof. An outer cylinder 20 having a valve V is connected, and a secondary silencer M2 is interposed in the second exhaust pipe 12.

  Since both the primary silencer M1 and the secondary silencer M2 have a conventionally known structure, detailed description thereof is omitted.

  As shown in FIG. 2, the downstream portion of the first exhaust pipe 11 provided with the butterfly valve V is surrounded by a cylindrical outer cylinder 20 concentric with the first exhaust pipe 11. The front and rear opening edges and the outer peripheral surface of the first exhaust pipe 11 are closed by front and rear end plates 21 and 22, and an annular exhaust gas flow passage 24 is provided between the first exhaust pipe 11 and the outer cylinder 20. Is formed. As shown in FIGS. 3 and 4, a rectangular valve port 25 communicating with the exhaust gas flow passage 24 is opened on the peripheral wall of the first exhaust pipe 11, and the first exhaust pipe is surrounded by the valve port 25. An inner mesh plate 26 and an outer mesh plate 27 that are stacked on each other are spot welded to one outer peripheral surface. The outer mesh plate 27 is formed to be slightly larger than the inner mesh plate 26. A stay 28 having a U-shaped cross section is welded to the outer peripheral surface of the first exhaust pipe 11 so as to straddle the valve opening 25 from the front and rear, and the valve opening 25 is opened and closed at the front and rear end edges of the stay 28. A circular arc-shaped valve body 30 is pivotally supported by a valve shaft 31 so as to be freely opened and closed, and a resonance preventing weight 29 is fixed to the valve body 30. 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. doing. When the exhaust gas pressure flowing through the first exhaust pipe 11 becomes higher than the resilience of the valve spring 32, the valve body 30 is opened.

  As shown in FIG. 4, a cap 33 that closes the flow path of the first exhaust pipe 11 is fixed downstream of the butterfly valve V of the first exhaust pipe 11, and the cap 33 of the first exhaust pipe 11 is further fixed. A number of punch holes 34 are opened further downstream, and the exhaust gas in the exhaust gas flow passage 24 is discharged to the atmosphere through the 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 second exhaust pipe 12 via the branch portion 2, but does not flow into the first exhaust pipe 11, and all of the exhaust gas flows through the secondary silencer M2 and the secondary. It is muted and discharged into the atmosphere. At this time, as shown by a solid line arrow in FIG. 4, a part of the exhaust gas allows the exhaust to flow to the dead end part from the branch part 2 to the butterfly valve V in the first exhaust pipe 11, and this part resonates. It becomes a tube, and the inside functions as a resonance chamber (resonance chamber) and has a resonance attenuation function for exhaust gas. And by making a part sufficiently long as a resonance tube, the resonance attenuation function of the exhaust sound can be further enhanced, and therefore the noise reduction performance in the low-speed rotation region of the engine E can be further enhanced.

  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, as shown by the two-dot chain line arrow in FIG. 4, a part of the exhaust gas flowing through the exhaust pipe 1 flows through the first exhaust pipe 11 and is discharged to the atmosphere via the butterfly valve V, while the remaining part is After flowing through the second exhaust pipe 12, passing through the secondary silencer M2, and being secondarily silenced, it is discharged to the atmosphere.

  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 configured by the butterfly valve V has been described. However, this may be configured by the reed valve V and other valves V having the same function.

Overall perspective view of the exhaust system of the present invention Enlarged cross-sectional view along line 2-2 in FIG. Sectional view along line 3-3 in FIG. Sectional view along line 4-4 in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ...... Exhaust pipe 2 ... Branch part 11 ... 1st exhaust pipe 12 ... 2nd exhaust pipe E ... Engine M2 ... Silencer (2nd silencer)
V ... Open / close valve (butterfly valve)

Claims (1)

An exhaust pipe (1) through which exhaust gas from the engine (E) flows is branched into a first exhaust pipe (11) and a second exhaust pipe (12) via a branch part (2), and the first exhaust pipe ( 11) is provided with an on-off valve (V) and a silencer (M2) is provided on the second exhaust pipe (12). In the low-speed rotation region of the engine (E), the on-off valve (V) is closed and the second exhaust pipe ( 12) Exhaust gas is exhausted only to the atmosphere, and in the high-speed rotation region of the engine (E), the on-off valve (V) is opened and both exhaust pipes of the first exhaust pipe (11) and the second exhaust pipe (12) are opened. An exhaust system for an engine that discharges exhaust gas from the atmosphere to the atmosphere.
An engine characterized in that when the on-off valve (V) is closed, a resonance pipe for exhaust gas is formed in a portion from the branch portion (2) to the on-off valve (V) in the first exhaust pipe (11). Exhaust system.

Images