JP4960936B2 - Engine exhaust system - Google Patents

Description

  The present invention relates to an engine exhaust device disposed in an exhaust system of a vehicle such as an automobile.

  Conventionally, for example, a muffler is mounted on an exhaust system of an engine of a vehicle such as an automobile in order to reduce exhaust noise. With regard to this type of silencer, for example, Patent Document 1 discloses a multiple-type silencer that can simultaneously reduce exhaust noise and reduce exhaust gas back pressure over the entire engine speed. Has been.

  In the multiple silencer disclosed in Patent Document 1, an exhaust pipe body connected to an engine, a branch pipe branched from the middle of the exhaust pipe body, and a first opening / closing provided in the middle of the branch pipe A first muffler comprising two valves: a valve, a first tail pipe connected to the exhaust pipe body and not provided with an on-off valve; and a second tail pipe having a second on-off valve; A configuration is adopted in which a second silencer having two pipes consisting of a third tail pipe connected to a pipe and not provided with an on-off valve and a fourth tail pipe having a third on-off valve is employed.

  In this case, in the idling rotation to low rotation range of the engine, all of the first to third on-off valves are closed to close the branch pipe, and only from the first tail pipe of the first silencer communicating with the exhaust pipe body. Exhaust gas is discharged. Next, in the middle rotation range of the engine, the first on-off valve is closed to close the branch pipe, and only the second on-off valve is opened to communicate with the exhaust pipe main body. Exhaust gas is discharged from the first tail pipe and the second tail pipe of the vessel.

Subsequently, when the engine is in a high speed range and the load is small, only the first on-off valve and the second on-off valve are opened, and the first tail pipe, the second tail pipe, and the second silencer of the first silencer are opened. Exhaust gas is discharged from the third tail pipe, and when the load is high in the high rotation range, all the first to third on / off valves are opened and the exhaust gas is discharged from all of the first to fourth tail pipes. I am letting.
Japanese Utility Model Publication No. 5-96429

  However, in the multiple silencer disclosed in Patent Document 1, the exhaust from the first tail pipe and / or the second tail pipe of the first silencer communicating with the exhaust pipe body in the idling rotation to middle rotation range of the engine. The exhaust noise is reduced by discharging gas. Generally, in the low engine speed range, the larger the capacity of the silencer, the higher the noise reduction efficiency, whereas the second silencer There is a problem that it is not used at all and is not effectively silenced.

  Further, in the multiple silencer disclosed in Patent Document 1, exhaust gas is discharged from the first silencer communicating with the exhaust pipe body and exhausted from the second silencer in the idling rotation to middle rotation range of the engine. The gas is not discharged. Therefore, for example, when the vehicle is used in a low-temperature environment such as in winter, white smoke due to water vapor is generated only from the first silencer from which exhaust gas is discharged, and white smoke is generated from the second silencer from which exhaust gas is not discharged. Therefore, there is a possibility that the automobile user may feel uneasy that the gas passage communicating with the second silencer of the exhaust system may be blocked.

  The present invention has been made in view of the above points, and exhaust gas is discharged from both the first silencer and the second silencer in the engine idling rotation to middle rotation range, thereby further improving the silencing efficiency. It is another object of the present invention to provide an engine exhaust device that can achieve low back pressure and avoids anxiety for an automobile user.

In order to achieve the above object, according to the present invention, an exhaust pipe connected to an engine has a first exhaust pipe disposed upstream of a branch part and a second exhaust gas disposed downstream of the branch part. An exhaust system for an engine comprising a first silencer connected to the second exhaust pipe and a second silencer connected to the third exhaust pipe. The third exhaust pipe is provided with first to third flow control valves for controlling the flow rate of the exhaust gas flowing through the pipe, and each flow control valve controls the flow rate of the exhaust gas according to the valve opening degree. There is provided a valve body and a flow means for circulating a part of the exhaust gas from the upstream side to the downstream side when the valve body is closed, and in the idling rotation to low rotation range of the engine All the valve bodies of the first to third flow control valves are closed. The valve body of the second flow rate control valve and the third flow rate control valve is maintained in the valve closed state and the valve body of the first flow rate control valve becomes the valve opened state, in the high rotation region of the engine, all of the valve body of the first through third flow control valve and said Rukoto such a valve open state.

  According to the present invention, for example, in the idling rotation to middle rotation range of the engine, even if the valve body is closed, exhaust is performed through the flow means provided in the first to third flow control valves, respectively. Compared with the prior art in which exhaust gas is discharged only from one side of the silencer by flowing a part of the gas and discharging exhaust gas from both the first silencer and the second silencer. The noise reduction efficiency can be further improved, and a low back pressure can be achieved.

In other words, according to the present invention, in the idling rotation to low rotation range of the engine, all the valve bodies of the first to third flow rate control valves are in the closed state, and the exhaust gas is discharged via the circulation means. A part can be circulated , and the exhaust gas is discharged from both the first silencer and the second silencer to increase the capacity of the entire silencer through which the exhaust gas circulates (passes) compared to the conventional case. As a result, the silencing efficiency can be increased and a low back pressure can be achieved.
Further, in the middle speed range of the engine, the valve bodies of the second flow rate control valve and the third flow rate control valve are held in the valve closed state, and the valve body of the first flow rate control valve is in the valve open state, By discharging the exhaust gas from both the first silencer and the second silencer, low back pressure can be ensured, and the generation of airflow noise can be suppressed.
Furthermore, in the high engine speed range, all the valve bodies of the first to third flow rate control valves are opened, thereby suppressing the generation of airflow noise while ensuring low exhaust gas back pressure. be able to.
As described above, in the present invention, the flow rate of the exhaust gas can be controlled in three stages of the engine rotation range from the idling rotation to the low rotation region, the middle rotation region, and the high rotation region.

  Further, according to the present invention, for example, even when a vehicle is used in a low-temperature environment such as winter, exhaust from both the first silencer and the second silencer in the idling rotation to middle rotation range of the engine. By discharging the gas, it is possible to suitably avoid anxiety that an automobile user may have the exhaust pipe on one side blocked.

  In this case, for example, a tube member that surrounds the outer peripheral surface of the valve body is provided as the circulation means, and a part of the exhaust gas is circulated by a gap formed between the valve body and the tube member, or A part of the exhaust gas may be circulated by a bypass pipe that bypasses the valve body and communicates the upstream side and the downstream side of each flow control valve. This is because a part of the exhaust gas can be circulated with a simple structure when the valve body is in the valve closed state.

  Further, according to the present invention, a pair of tail pipes that exhaust exhaust gas into the atmosphere is connected to the first silencer and the second silencer, respectively, and the second flow rate control valve and the third flow rate control valve are connected to each other. One of the pair of tail pipes is provided in each of the first silencer and the second silencer, and the opening degree of the second flow rate control valve and the third flow rate control valve is controlled. The flow of the exhaust gas from the tail pipe may be blocked, and the flow means may be constituted by the other tail pipe of the pair of tail pipes. Further, a third silencer is connected to the first exhaust pipe, and the first flow rate control valve is disposed in the vicinity of the introduction port where the exhaust gas is introduced into the third silencer inside the third silencer. It is good to be done.

  As described above, the first flow rate control valve is integrally provided in the third silencer, or the second flow rate control valve and the third flow rate control valve are integrally provided in the first silencer and the second silencer. By providing, the number of parts can be reduced and the manufacturing cost can be reduced.

  In the present invention, the exhaust gas is discharged from both the first silencer and the second silencer in the idling rotation to the middle rotation range of the engine, thereby further improving the silencing efficiency and lowering the back pressure. Furthermore, it is possible to obtain an engine exhaust device that can avoid making an automobile user feel uneasy.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 is a schematic perspective view of an engine exhaust system according to an embodiment of the present invention applied to an automobile exhaust system.

  The exhaust device 10 according to the embodiment of the present invention will be described below based on what is interposed in the exhaust system 3 of the engine 2 (internal combustion engine) of a vehicle such as the automobile 1, but is not limited thereto. It can also be applied to an exhaust system of an engine other than a vehicle.

  As shown in FIG. 1, an engine 2 mounted on an automobile 1 is provided with an exhaust system 3 for discharging exhaust gas discharged from the engine 2 to the atmosphere. The exhaust system 3 includes an exhaust manifold 4 connected to an exhaust port of the engine 2, an exhaust pipe 5 connected to the downstream side of the exhaust manifold 4, and an exhaust gas purification connected in the middle of the exhaust pipe 5. And the exhaust device 10 according to the first embodiment of the present invention connected to the downstream side of the catalyst 6.

  2A is a schematic configuration diagram of the exhaust device according to the first embodiment of the present invention, and FIG. 2B is a longitudinal section of the first on-off valve along the line IIB-IIB in FIG. 2A. Drawing 2 and Drawing 2 (c) are transverse cross sections of the 1st on-off valve along IIC-IIC of Drawing 2 (b).

  As shown in FIG. 2 (a), the exhaust device 10 according to the first embodiment is connected to the downstream side of the catalyst 6 and is disposed upstream of a branching section 12 to be described later. An exhaust pipe 14 a, a first on-off valve (flow control valve) 16 a and a pre-chamber (third silencer) 18 that are sequentially arranged in series downstream of the first exhaust pipe 14 a, and a downstream of the pre-chamber 18 A bifurcated portion 12 that is bifurcated, a second exhaust pipe 14b and a third exhaust pipe 14c that are provided substantially in parallel on the downstream side branched from the bifurcated portion 12, and a downstream side of the second exhaust pipe 14b. The second on-off valve (flow control valve) 16b and the first silencer 20a, which are sequentially connected in series and arranged on the right side of the rear of the vehicle body in plan view, are sequentially connected in series to the downstream side of the third exhaust pipe 14c. Connected and arranged on the left side of the rear of the car body in plan view And a third on-off valve (flow control valve) 16c and a second silencer 20b to be.

  Connected to the first silencer 20a and the second silencer 20b are two tail pipes 22a and 22b, respectively, for releasing the exhaust gas in the silencer to the atmosphere. The first on-off valve 16a is disposed on the upstream side of the pre-chamber 18, but is disposed on the downstream side of the pre-chamber 18 as indicated by a two-dot chain line in FIG. May be.

  Exhaust gas discharged by driving the engine 2 is purified by the catalyst 6 and then temporarily silenced by the pre-chamber 18, and further by the first silencer 20a and the second silencer 20b. It is silenced and discharged into the atmosphere.

  The first to third on-off valves 16a to 16c have the same configuration, and are normally closed type valves that are initially closed. Hereinafter, the structure of the first on-off valve 16a will be described in detail, and the description of the second on-off valve 16b and the third on-off valve 16c will be omitted.

  As shown in FIGS. 2B and 2C, the first on-off valve 16a includes a tube member 24 formed in a substantially cylindrical shape, and an inlet port and an outlet port (not shown) communicating with the first exhaust pipe 14a. A pair of end plates (not shown) that are formed and close both ends of the tube member 24, and a substantially disc-shaped valve body 30 that is pivotally supported in the tube member 24 by a pivot shaft 28. And have.

  An annular gap (flow means) 32 is formed between the inner wall of the tube member 24 and the outer peripheral surface of the valve body 30 so as to be spaced apart by a predetermined distance along the radial direction. The exhaust gas is partially allowed to flow from the upstream side to the downstream side without being affected by the opening / closing operation.

  For example, an elastic member (not shown) such as a spring member is provided to bias the valve body 30 in a valve closed state substantially orthogonal to the axis of the tube member 24, and the valve body resists the spring force of the spring member. By rotating 30 by a predetermined angle about the rotation shaft 28, the valve opening degree is adjusted to the valve open state in which the exhaust gas flows through the inside of the tube member 24.

  That is, when the valve body 30 is in a valve closed state that is substantially orthogonal to the axis of the tube member 24 in the initial state, the valve body 30 acts as a barrier to prevent the exhaust gas from flowing, and the tube member 24 and the valve body 30 A portion of the exhaust gas is circulated through a gap 32 formed between the two (see FIG. 2C).

  On the other hand, when the valve body 30 is displaced (turned) and is in a valve open state substantially parallel to the axis of the tube member 24, the valve body 30 does not become a barrier and exhausts along the inside of the tube member 24. Gas circulates.

  Each of the first to third on-off valves 16a to 16c may be configured to open and close the valve body 30 by increasing or decreasing the pressure of exhaust gas (exhaust pressure), or, for example, an electromagnetic solenoid or an electric device (not shown) The valve body 30 may be configured to open and close by an electrical mechanism such as an actuator.

  The exhaust system 3 of the automobile 1 to which the exhaust device 10 according to the first embodiment of the present invention is applied is basically configured as described above. Next, the function and effect will be described.

  First, in the idling rotation to low rotation range of the engine 2, all the valve bodies 30 of the first to third on-off valves 16 a to 16 c are closed, and the exhaust gas flow in the tube member 24 is While being blocked by the valve body 30, a part of the exhaust gas flows along the gap 32 between the tube member 24 of the first to third on-off valves 16 a to 16 c and the valve body 30.

  Therefore, the exhaust gas that has passed through the gap 32 of the first on-off valve 16a is primarily silenced by the pre-chamber 18, and the exhaust gas that has passed through the gap 32 of the second on-off valve 16b via the branch portion 12 is first filtered. At the same time as being discharged from the tail pipes 22a and 22b of the first silencer 20a, the exhaust gas that has passed through the gap 32 of the third on-off valve 16c is discharged from the tail pipes 22a and 22b of the second silencer 20b.

  As a result, exhaust gas can be sufficiently reduced by passing exhaust gas through the first silencer 20a and the second silencer 20b simultaneously.

  Next, in the middle rotation range of the engine 2, the valve body 30 of the first on-off valve 16a is displaced while the valve bodies 30 of the second on-off valve 16b and the third on-off valve 16c are respectively held in the valve closed state. Thus, the valve opening degree is adjusted from the valve closed state to the valve open state. Therefore, when the valve body 30 of the first on-off valve 16a disposed on the upstream side of the branching portion 12 is opened, the exhaust gas can flow through the tube member 24, and the back pressure is reduced. Can be ensured, and the generation of airflow noise can be suppressed.

  Further, in the high speed range of the engine 2, by adjusting the valve opening degree of all the valve bodies 30 of the first to third on-off valves 16a to 16c from the valve closed state to the valve open state, the exhaust gas has a low profile. The generation of airflow noise can be suppressed while securing the pressure.

  As described above, in the first embodiment, exhaust gas is discharged from both the first silencer 20a and the second silencer 20b in the idling rotation to middle rotation range of the engine 2, and the exhaust gas is discharged from only one silencer on one side. Compared with the prior art in which the gas is discharged, the noise reduction efficiency can be further improved and a low back pressure can be achieved.

  In other words, in the first embodiment, the exhaust gas is circulated by discharging exhaust gas from both the first silencer 20a and the second silencer 20b in the idling rotation to low rotation range of the engine 2 as compared with the conventional one. By increasing the capacity of the entire silencer that passes (passes through), it is possible to increase the silencing efficiency and achieve a low back pressure.

  Furthermore, in the first embodiment, for example, even when the automobile 1 is used in a low-temperature environment such as winter, the first silencer 20a and the second silencer 20b are in the idling rotation to middle rotation range of the engine 2. By discharging the exhaust gas from both of them, it is possible to suitably avoid anxiety that the automobile user may have the exhaust pipe on one side blocked.

  Next, an exhaust device 10a according to a second embodiment of the present invention is shown in FIG. In the embodiment described below, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. FIG. 3A is a schematic configuration diagram of an exhaust device according to the second embodiment, and FIG. 3B is a longitudinal sectional view of the first on-off valve along the line IIIB-IIIB in FIG. .

  In the exhaust device 10a according to the second embodiment, in the first to third on-off valves 40a to 40c having the same configuration, the outer diameter of the disc-shaped valve body 42 is substantially the same as the inner diameter of the tube member 24. The gap 32 is not provided, and instead of the gap 32, the valve body 42 of the first to third on-off valves 40a to 40c is bypassed to the inlet of the first to third on-off valves 40a to 40c. By providing a small-diameter bypass conduit (circulation means) 44 that allows communication between the port side (upstream side) and the outlet port side (downstream side), the same effect as in the first embodiment can be obtained.

  That is, when the valve body 42 is closed and in the valve closed state, a part of the exhaust gas is allowed to flow along the small-diameter bypass pipe 44 bypassing the valve body 42, thereby The same effect as 32 can be obtained.

  In the following embodiments, the first to third on-off valves 16a to 16c in the first embodiment in which the gap 32 is formed between the tube member 24 and the valve body 30 are used as partially closed on-off valves. On the other hand, the first to third on-off valves 40a to 40c in the second embodiment in which the gap 32 is not formed are completely closed on-off valves (see FIG. 3 (b)), and are black valve symbols. This will be described below.

  Next, FIGS. 4A to 4D show an exhaust device according to another embodiment configured by mixing the partially closed type on / off valve and the fully closed type on / off valve as an on / off valve.

  FIG. 4A is a schematic configuration diagram of an exhaust device 10b according to the third embodiment. In the third embodiment, the first on-off valve 16a disposed on the upstream side of the branching portion 12 is connected to the gap 32. FIG. The second on-off valve 40b and the third on-off valve 40c arranged on the downstream side of the branching section 12 are constituted by a completely closed on-off valve having a bypass line 44.

  FIG. 4B is a schematic configuration diagram of the exhaust device 10c according to the fourth embodiment. In the fourth embodiment, the first on-off valve 40a disposed on the upstream side of the branching portion 12 is connected to the bypass pipe line. The second on-off valve 16b and the third on-off valve 16c arranged on the downstream side of the branching portion 12 are constituted by partially closed on-off valves having a gap 32.

  FIG. 4C is a schematic configuration diagram of the exhaust device 10d according to the fifth embodiment. In the fifth embodiment, the first on-off valve 16a disposed on the upstream side of the branching portion 12 is replaced with the gap 32. The second on-off valve 40b disposed on one downstream side of the branch portion 12 is configured by a fully-closed on-off valve having a bypass line 44, and the other on-off valve of the branch portion 12 is configured. The third on-off valve 16 c disposed on the downstream side is configured by a partially closed on-off valve having a gap 32.

  FIG. 4D is a schematic configuration diagram of the exhaust device 10e according to the sixth embodiment. In the sixth embodiment, the first on-off valve 40a disposed on the upstream side of the branching section 12 is connected to the bypass pipe line. The second on-off valve 16b disposed on one downstream side of the branch portion 12 is configured by a partially-closed on-off valve having a gap 32, and the other end of the branch portion 12 The third on-off valve 40 c disposed on the downstream side is configured by a completely closed on-off valve having a bypass line 44.

  In this way, by configuring the first to third on-off valves 16a to 16c and 40a to 40c by mixing the partially-closed on-off valve having the gap 32 and the fully-closed on-off valve having the bypass pipe 44 in combination. The same operational effects as in the first embodiment can be obtained.

  Next, an exhaust device according to a seventh embodiment is shown in FIG. FIG. 5A is a schematic configuration diagram of the exhaust device according to the seventh embodiment, FIG. 5B is an enlarged vertical cross-sectional view of the first silencing mechanism 50a, and FIG. 5C is FIG. It is a longitudinal cross-sectional view along the VB-VB line of FIG.

  In the exhaust device 10f according to the seventh embodiment, as shown in FIG. 5A, the first on-off valve 16a and the pre-chamber (third silencer) 18 disposed on the upstream side of the branching portion 12 are integrated. The first silencing mechanism 50a configured as a single unit, the second on-off valve 40b disposed on one downstream side of the branching section 12, and the first silencer 20a are integrated into a second silencing mechanism 50b. And a third silencer mechanism 50c configured by integrating a third on-off valve 40c and a second silencer 20b disposed on the other downstream side of the branching section 12. The second silencing mechanism 50b and the third silencing mechanism 50c have the same configuration.

  As shown in FIG. 5B, the first silencing mechanism 50a includes a housing 52 formed in a substantially cylindrical shape, a pair of closing members 54a and 54b that respectively close both ends of the housing 52, and The first opening / closing valve 16a is a partially closed opening / closing valve disposed in the vicinity of the introduction port of the housing 52. The first on-off valve 16a is configured in the same way as the partially-closed on-off valve shown in FIGS. 2B and 2C, and detailed description thereof is omitted.

  As shown in FIGS. 5A and 5C, the second silencing mechanism portion 50b (third silencing mechanism portion 50c) is disposed inside the silencer housing 58 and communicates with the atmosphere. It has the 2nd on-off valve 40b (3rd on-off valve 40c) which consists of a complete block type on-off valve connected to one side of 22b. The second on-off valve 40b (third on-off valve 40c) is configured in the same manner as the completely closed on-off valve shown in FIG.

  In the seventh embodiment, the first on-off valve 16a made up of a partially closed on-off valve and the pre-chamber 18 are integrated, and the second on-off valve 40b (third on-off valve 40c) made up of a fully closed on-off valve and the first By integrating the silencer 20a (second silencer 20b), there is an advantage that the number of parts can be reduced and the manufacturing cost can be reduced.

  Briefly describing the operation of the seventh embodiment, in the idling rotation to low rotation range of the engine 2, all the valve bodies 30, 42 of the first to third on-off valves 16a, 40b, 40c are closed. Yes, the flow of the exhaust gas in the first silencing mechanism 50a is hindered by the valve body 30, and the flow of a part of the exhaust gas is caused by the gap 32 between the tube member 24 and the valve body 30 of the first on-off valve 16a. Permissible. Exhaust gas that has passed through the first silencing mechanism 50a is introduced into the second silencing mechanism 50b and the third silencing mechanism 50c via the branching section 12, and the second on-off valve 40b is not provided. And the other tail pipe (distribution means) 22b not provided with the third on-off valve 40c.

  As a result, in the seventh embodiment, as in the first embodiment, the exhaust gas passes through the second silencing mechanism 50b and the third silencing mechanism 50c at the same time in the idling rotation to low rotation range of the engine 2, respectively. Thus, exhaust noise can be sufficiently reduced.

  Next, an exhaust device according to another embodiment in which a large number of on-off valves are arranged is shown in FIG. FIG. 6 is a schematic configuration diagram of an exhaust device according to the eighth embodiment. In the exhaust device 10g according to the eighth embodiment, the first opening / closing valve 60a and the second opening / closing valve 60b are disposed on the upstream side and the downstream side of the pre-chamber 18 on the upstream side of the branching portion 12, respectively. 12, a third on-off valve 60c is disposed on the upstream side of the first silencer 20a, and a fourth on-off valve 60d is provided in the middle of one tail pipe 22a connected to the first silencer 20a. And the other tail pipe connected to the second silencer 20b by disposing the fifth on-off valve 60e on the other downstream side of the branching section 12 and upstream of the second silencer 20b. A sixth on-off valve 60f is disposed in the middle of 20b.

  In this case, the first on-off valve 60a, the second on-off valve 60b, the third on-off valve 60c, and the fifth on-off valve 60e are configured by partially closed on-off valves shown in FIGS. 2B and 2C, respectively. The fourth on-off valve 60d and the sixth on-off valve 60f disposed in the middle of the tail pipes 22a and 22b are constituted by fully closed on-off valves shown in FIG. In addition, the 4th on-off valve 60d and the 6th on-off valve 60f may be comprised by the partial obstruction | occlusion type on-off valve shown by FIG.2 (b) and (c), respectively.

  In the eighth embodiment, by providing a large number of on-off valves including the first to sixth on-off valves 60a to 60f, it is possible to further improve the silencing function and achieve further higher performance.

1 is a schematic perspective view of an engine exhaust device according to a first embodiment of the present invention applied to an automobile exhaust system. (A) is a schematic block diagram of the said exhaust apparatus, (b) is a longitudinal cross-sectional view of the 1st on-off valve along the IIB-IIB line of (a), (c) is IIC-IIC of (b). It is a cross-sectional view of the first on-off valve along the line. (A) is a schematic block diagram of the exhaust apparatus which concerns on 2nd Embodiment, (b) is a longitudinal cross-sectional view of the 1st on-off valve along the IIIB-IIIB line | wire of (a). (A)-(d) is a schematic block diagram of the exhaust apparatus which concerns on 3rd-6th embodiment, respectively. (A) is a schematic block diagram of the exhaust apparatus which concerns on 7th Embodiment, (b) is a longitudinal cross-sectional enlarged view of a 1st silencer mechanism part, (c) followed the VB-VB line | wire of (a). It is a longitudinal cross-sectional view. It is a schematic block diagram of the exhaust apparatus which concerns on 8th Embodiment.

Explanation of symbols

10, 10a to 10g Exhaust device 12 Branch portion 14a to 14c Exhaust pipes 16a to 16c, 40a to 40c, 60a to 60f On-off valve (flow control valve)
18 Prechamber (silencer)
20a, 20b Silencer 22a, 22b Tail pipe 24 Tube member 28 Rotating shaft 30, 42 Valve element 32 Gap 44 Bypass line

Claims (5)

An exhaust pipe connected to the engine is composed of a first exhaust pipe disposed upstream from the branch part, a second exhaust pipe and a third exhaust pipe disposed downstream from the branch part, In an engine exhaust system comprising a first silencer connected to two exhaust pipes and a second silencer connected to the third exhaust pipe,
The first to third exhaust pipes are provided with first to third flow control valves for controlling the flow rate of the exhaust gas flowing through the pipes, respectively. A valve body that controls the flow rate, and a circulation means that circulates a part of the exhaust gas from the upstream side toward the downstream side when the valve body is closed and the valve body is closed ,
In the idling rotation to low rotation range of the engine, all the valve bodies of the first to third flow rate control valves are closed,
In the middle rotation range of the engine, the valve bodies of the second flow rate control valve and the third flow rate control valve are held in the valve closed state, and the valve body of the first flow rate control valve is in the valve open state,
In the high rotation region of the engine, exhaust system of an engine in which all of the valve body of the first through third flow control valve and said Rukoto such a valve open state. The engine exhaust device according to claim 1,
The flow means has a tube member surrounding an outer peripheral surface of a valve body, and a part of exhaust gas is made to flow through a gap formed between the valve body and the tube member. Exhaust system. The engine exhaust device according to claim 1,
The engine exhaust device according to claim 1, wherein the flow means includes a bypass pipe that bypasses the valve body and communicates the upstream side and the downstream side of each flow control valve. The engine exhaust device according to claim 1,
Each of the first silencer and the second silencer is connected to a pair of tail pipes that discharge exhaust gas into the atmosphere.
The second flow rate control valve and the third flow rate control valve are provided inside the first silencer and the second silencer, respectively, and the opening degrees of the second flow rate control valve and the third flow rate control valve are controlled. Thus, the flow of the exhaust gas from one of the pair of tail pipes is blocked, and the other tail pipe in the pair of tail pipes constitutes the flow means. The engine exhaust system is characterized. The engine exhaust device according to claim 1,
A third silencer is connected to the first exhaust pipe, and the first flow rate control valve is disposed in the vicinity of the introduction port through which exhaust gas is introduced into the third silencer. An exhaust system for an engine.

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