CN108223056B - Engine exhaust system, engine and car - Google Patents

Abstract

An engine exhaust system, an engine and an automobile are provided, wherein the engine exhaust system comprises a silencing cavity; the silencing device comprises a first pipeline, a second pipeline and a third pipeline, wherein the first pipeline, the second pipeline and the third pipeline are provided with reversing pieces, one end of the second pipeline and one end of the third pipeline are communicated with the silencing cavity, and the other ends of the second pipeline and the third pipeline are connected with the reversing pieces; the length of the second pipeline is longer than that of the third pipeline, and the sum of the length of the second pipeline and the length of the first pipeline meets the following condition: the exhaust pressure reflection wave of the exhaust gas discharged by the exhaust valve at the outlet of the second pipeline and the exhaust wave at the closing time of the exhaust valve are mutually counteracted. The exhaust system of the invention improves the low-speed torque of the engine; meanwhile, the dynamic property of the engine at a high-speed stage is improved; exhaust noise is also reduced.

Description

Engine exhaust system, engine and car

Technical Field

The invention relates to the technical field of automobiles, in particular to an engine exhaust system, an engine and an automobile.

Background

For automobiles, it is desirable to increase the low speed torque of the engine while reducing the exhaust noise of the engine.

The low-speed torque of the engine greatly affects the acceleration of the automobile and can directly affect the feeling of a customer on the dynamic property of the whole automobile. Therefore, the low-speed torque of the engine is improved, so that automobile products can be favored by more customers in the increasingly intense automobile market, and the product performance and the competitiveness are improved. In the actual situation, the passenger car faces a lot of urban working conditions, and frequent start-stop and acceleration/deceleration working conditions occupy a large part of the service time of the car. Therefore, it is necessary to improve the low-speed torque of the engine.

The overall vehicle exhaust noise level directly affects the comfort of the vehicle. With the development of automobile technology and the popularization of automobiles, automobile customers have higher and higher requirements on the NVH performance (Noise, Vibration and Harshness for short) of the whole automobile, and thus an automobile product provider is required to reduce exhaust Noise so as to obtain more comfortable and silent products.

At present, the exhaust noise of the automobile is mainly reduced by adding silencers in an exhaust system, the number of the silencers is 1-3, and the arrangement of 2 silencers is common in gasoline automobiles.

When the structure of the muffler is improved to improve the exhaust noise reduction performance of the muffler, the exhaust back pressure of the engine is increased, and the exhaust back pressure is increased, so that the low-speed torque of the engine is reduced.

Further, during operation of the engine, as the engine speed increases, more exhaust gas is generated. A typical engine has a plurality of cylinder blocks, and accordingly, a plurality of exhaust manifolds. After flowing out from each exhaust manifold, the exhaust gas is converged to an exhaust pipe and then discharged to the atmosphere. Because the waste gas that the cylinder block produced increases, the waste gas in many exhaust manifolds assembles an blast pipe, and still sets up the silencer on the blast pipe, and this just leads to the air current resistance increase in the blast pipe, and the exhaust back pressure increases, influences the dynamic nature of engine at high-speed stage. At this time, it is necessary to reduce the back pressure of the exhaust system to improve the dynamic property of the engine at a high speed stage.

Therefore, the reasonable exhaust system structure can reduce the influence on the exhaust back pressure as much as possible while reducing the noise, and reduce the influence on the power torque of the engine.

However, an exhaust system which can simultaneously achieve low-speed torque, exhaust noise and power performance of the engine at a high-speed stage is not available.

Disclosure of Invention

The invention solves the problems that: the prior art fails to improve low speed torque of the engine while reducing exhaust noise.

To solve the above problems, the present invention provides an engine exhaust system comprising: a silencing cavity; the silencing device comprises a first pipeline, a second pipeline and a third pipeline, wherein the first pipeline, the second pipeline and the third pipeline are provided with reversing pieces, one end of the second pipeline and one end of the third pipeline are communicated with the silencing cavity, and the other ends of the second pipeline and the third pipeline are connected with the reversing pieces; one end of the first pipeline is provided with an engine exhaust manifold connecting interface; the reversing piece can be switched between a first state and a second state, the first pipeline is communicated with the second pipeline in the first state, and the first pipeline is communicated with the third pipeline in the second state; the length of the second pipeline is longer than that of the third pipeline, and the sum of the length of the second pipeline and the length of the first pipeline meets the following condition: the exhaust pressure reflection wave of the exhaust gas discharged by the exhaust valve at the outlet of the second pipeline and the exhaust wave at the closing time of the exhaust valve are mutually counteracted.

Optionally, the other end of the first pipeline is communicated with the second pipeline; the reversing piece comprises: the first shell is fixedly arranged outside the first pipeline and provided with a first inner cavity which is communicated with the third pipeline;

the second shell is positioned in the first inner cavity and fixedly arranged outside the first pipeline, the second shell is provided with a second inner cavity, and an opening for communicating the second inner cavity with the first inner cavity is formed in the second shell along the length direction of the first pipeline;

the cover body is positioned in the first inner cavity, movably sleeved outside the first pipeline and used for covering the opening;

the elastic piece is connected with the cover body at one end and connected with the first pipeline or the second shell at the other end along the length direction;

the outer surface of the part of the first pipeline positioned in the second inner cavity is provided with a plurality of through holes;

in the first state, the pressure of the waste gas in the second inner cavity is smaller than the elastic force of the elastic piece, and the cover body is attached to the second shell and covers the opening;

in the second state, the pressure of the exhaust gas in the second inner cavity is larger than the elastic force of the elastic piece, the cover body moves back to the second shell along the length direction, and the first inner cavity is communicated with the second inner cavity.

Optionally, the elastic member is a spring or rubber.

Optionally, the reversing piece is a reversing valve, and the reversing valve is provided with a first pressure valve and a second pressure valve; the first pressure valve is located between the first pipeline and the second pipeline, and the second pressure valve is located between the first pipeline and the third pipeline;

in the first state, the pressure of the exhaust gas in the first pipeline is greater than the opening pressure of the first pressure valve and less than the opening pressure of the second pressure valve;

in the second state, the pressure of the exhaust gas in the first pipe is greater than the cracking pressure of the first pressure valve and the cracking pressure of the second pressure valve.

Optionally, the ratio of the sum of the areas of the cross sections of all the through holes to the area of the cross section of the first pipeline is 1.2 to 1.5.

Optionally, the muffler further comprises a resonant cavity, wherein the resonant cavity is close to the muffling cavity and is communicated with the second pipeline.

Optionally, the muffling frequency of the resonant cavity is below 200 HZ.

Optionally, the method further includes: and one end of the engine exhaust manifold is connected with an engine cylinder body, and the other end of the engine exhaust manifold is connected with the first pipeline.

Optionally, the muffler further comprises a rear muffler, and the rear muffler is communicated with the muffling cavity.

Optionally, the method further includes: one end of the fourth pipeline is communicated with the second pipeline through the silencing cavity, and the other end of the fourth pipeline is communicated with the rear silencer;

and one end of the fifth pipeline is communicated with the third pipeline through the silencing cavity, and the other end of the fifth pipeline is communicated with the rear silencer.

The invention also provides an engine comprising the engine exhaust system.

The invention also provides an automobile comprising the engine.

Compared with the prior art, the technical scheme of the invention has the following advantages:

when the first line in the exhaust system is in communication with the exhaust manifold of the engine.

When the engine is in the first state, for example, the engine is in a part load condition, the engine speed is low. The reversing piece is switched to enable the first pipeline and the second pipeline to be communicated, and exhaust gas generated by the engine flows out of the longer second pipeline. When the exhaust valve is opened again, exhaust waves are generated when exhaust gas in the engine cylinder is exhausted through the exhaust valve, and exhaust pressure reflection waves are generated when the generated exhaust gas flows to the silencing cavity. The sum of the length of the second pipeline and the length of the first pipeline satisfies the following condition: the exhaust pressure reflection wave of the exhaust gas discharged by the exhaust valve at the outlet of the second pipeline and the exhaust wave at the closing time of the exhaust valve are mutually counteracted.

The reflected wave and the exhaust wave at the exhaust valve cancel each other out, and the pressure of the exhaust wave at the exhaust valve is lower than the average pressure of the exhaust pipe. I.e. the pressure at the exhaust valve is reduced, i.e. the exhaust back pressure at the exhaust valve is reduced. The residual waste gas in the cylinder is exhausted more smoothly, the residual waste gas in the cylinder is reduced, the charging coefficient is increased, and the low-speed torque of the engine is increased. Meanwhile, when the generated waste gas passes through the silencing cavity, the exhaust noise is also controlled.

In the second state, for example, the engine is in a full load condition, the engine speed is high, the exhaust gas generated by the engine is increased, and the airflow resistance is increased. The reversing piece is switched to enable the first pipeline and the third pipeline to be communicated, and generated waste gas flows out of the shorter third pipeline. That is, when the engine is in a high rotating speed, the generated waste gas can be discharged quickly, the waste gas is discharged smoothly, and the exhaust back pressure is reduced. Meanwhile, when the generated waste gas passes through the silencing cavity, the exhaust noise is also controlled.

In conclusion, when the engine rotates at a low speed, the exhaust backpressure at the outlet of the exhaust valve is reduced, and the low-speed torque of the engine is improved; meanwhile, when the engine rotates at a high speed, the exhaust back pressure of the exhaust pipe is also reduced, and the dynamic property of the engine at a high-speed stage is improved; in addition, no matter the engine is in low rotational speed or high rotational speed, the waste gas in the cylinder body can all pass through the noise elimination cavity, has reduced exhaust noise.

Drawings

FIG. 1 is a schematic block diagram of an engine exhaust system according to an embodiment of the present invention;

FIG. 2 is a first schematic structural diagram of a reversing element in an exhaust system of an engine according to an embodiment of the invention, wherein a cover body is shown in an open state;

fig. 3 is a schematic structural diagram two of a reversing member in an engine exhaust system according to an embodiment of the invention, and a cover body is shown in an open state.

Detailed Description

In the prior art, after a silencer is arranged on an exhaust pipe, when an engine rotates at a low speed, exhaust back pressure at an outlet of the exhaust pipe is large; when the engine rotates at a high speed, the exhaust back pressure of the exhaust pipe is high. The pre-silencer of the invention utilizes the acoustic wave interference principle, and when the engine rotates at a low speed, the exhaust back pressure at the outlet of the exhaust valve is reduced; meanwhile, when the engine rotates at a high speed, the exhaust back pressure of the exhaust pipe is also reduced.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

The dynamic performance is a core evaluation index of the engine, and according to the engine principle, the torque of the engine can be improved by improving the intake density and the charge coefficient, and the dynamic performance is improved. Because passenger cars face a lot of urban working conditions, frequent starting, stopping and acceleration and deceleration working conditions occupy a large part of the service time of the cars. The low-speed torque of the engine greatly affects the acceleration of the automobile and can directly affect the feeling of a customer on the dynamic property of the whole automobile. Therefore, the low-speed torque of the engine is improved, so that automobile products can be favored by more customers in the increasingly intense automobile market, and the product performance and the competitiveness are improved.

As described in the background section, the noise of the exhaust gas and the exhaust back pressure of the vehicle are a pair of parameters that contradict each other, and the muffling structure of the muffler causes the exhaust back pressure to rise. The exhaust gas in the cylinder body is not smoothly discharged, so that more residual exhaust gas is generated in the cylinder body, the charging coefficient of the engine is low, and the low-speed torque of the engine is low.

The exhaust system of a vehicle is one of the important components in a vehicle. Vehicle exhaust noise is a major source of noise in motor vehicles and is also a major concern in urban environmental noise control. In order to reduce exhaust noise, motor vehicles generally use mufflers in the exhaust system for exhaust. In general, a plurality of mufflers are provided in an exhaust pipe, and a muffler closest to an exhaust manifold is referred to as a "front muffler" and a muffler farthest from the exhaust manifold is referred to as a "rear muffler".

The exhaust gas generated in the cylinder body is exhausted by the exhaust valve, and then is exhausted to the atmosphere after sequentially passing through the exhaust manifold, the plurality of silencers and the exhaust pipe. No matter what kind of operating mode the engine is in, the waste gas in the cylinder body all is through same blast pipe discharge.

However, the exhaust noise and the exhaust back pressure of the automobile are a pair of parameters which contradict each other. When the exhaust gas in the cylinder block flows through the muffler, the muffler inevitably increases the exhaust resistance of the engine due to the structure, and the exhaust back pressure rises. Particularly, when the engine is in a partial load working condition and is in a low rotating speed, the flow speed of the waste gas flow is slow, and the pressure at the outlet of the exhaust valve is large. That is, at low rotation speed, the exhaust back pressure at the outlet of the exhaust valve is large, so that the exhaust gas in the cylinder body is not smoothly discharged, more residual exhaust gas is left in the cylinder body, the charge coefficient of the engine is low, and the low-speed torque of the engine is low.

Furthermore, as engine speed increases, more exhaust gas is generated, especially at full load conditions. A typical engine has a plurality of cylinder blocks, and accordingly, a plurality of exhaust manifolds. After flowing out from each exhaust manifold, the exhaust gas is converged to an exhaust pipe and then discharged to the atmosphere. Because the waste gas that the cylinder block produced increases, the waste gas in the many exhaust manifolds assembles an blast pipe, and still sets up the silencer on the blast pipe, and this just leads to the air current resistance increase in the blast pipe, and exhaust back pressure increases. At this time, the back pressure of the exhaust system needs to be reduced.

The exhaust noise of the automobile is not affected, and the exhaust back pressure can be reduced. Referring to fig. 1, an embodiment of the present invention provides an engine exhaust system including: the shell 11, the shell 11 is equipped with the noise elimination cavity 12, and the noise elimination cavity 12 and the shell 11 constitute the pre-silencer 10. When the exhaust gas discharged from the engine 30 flows through the sound attenuation chamber 12, the sound attenuation chamber 12 functions to reduce noise. Further comprising: a first pipeline 13, a second pipeline 14 and a third pipeline 15 which are provided with reversing pieces 20; one end of the second pipeline 14 and one end of the third pipeline 15 are both communicated with the silencing cavity 12, and the other ends are both connected with the reversing piece 20; the first pipe 13 has an engine exhaust manifold connection at one end.

Namely: the first pipe 13 has one end for communicating with an engine exhaust manifold 31, the engine exhaust manifold 31 communicates with an exhaust valve (not shown) of a cylinder block (not shown), and exhaust gas in the cylinder block flows into the exhaust manifold 31 after being discharged through the exhaust valve, and flows into the pre-muffler 10 from the exhaust manifold 31.

In this embodiment, the reversing element 20 is disposed on the first pipeline 13; one end of the second pipeline 14 is communicated with the silencing cavity 12, and the other end of the second pipeline is connected with the reversing piece 20; one end of the third pipeline 15 is communicated with the silencing cavity 12, and the other end of the third pipeline is connected with the reversing piece 20.

The diverter 20 is switchable between a first state in which the first and second lines 13, 14 are in communication, and a second state in which the first and third lines 13, 15 are in communication, i.e. the diverter 20 functions to: the flow direction of the exhaust gas discharged from the cylinder block under different operating conditions in the front muffler 10 is switched.

In the present embodiment, after the engine exhaust manifold connection port at one end of the first pipe 13 in the front muffler 10 is communicated with the exhaust manifold 31 of the engine 30, the exhaust gas in the cylinder block flows into the first pipe 13 from the exhaust manifold 31 and flows into the front muffler 10.

The first state: when the engine 30 is in a part load condition, the engine 30 is rotating at a low speed. The direction change member 20 is switched so that the other end of the first pipe 13 and the second pipe 14 are communicated, and the exhaust gas generated by the engine flows out from the longer second pipe 14 (the thin black arrow in fig. 1 represents the flow direction of the exhaust gas in the second pipe 14). When the exhaust valve is opened again, exhaust waves are generated when exhaust gas in the engine cylinder is exhausted through the exhaust valve, and exhaust pressure reflection waves are generated when the generated exhaust gas flows to the silencing cavity 12 through the second pipeline 14.

In the present embodiment, the length of the second pipeline 14 is longer than the length of the third pipeline 15, and the sum of the length of the second pipeline 14 and the length of the first pipeline 13 satisfies the following condition: the exhaust pressure reflection wave of the exhaust gas discharged from the exhaust valve at the outlet of the second pipe 14 and the exhaust gas wave at the closing time of the exhaust valve cancel each other out.

It can be understood that: the sum of the length of the second conduit 14 and the length of the first conduit 13 is equal to the velocity of the sound wave times the time interval between the opening and closing of the exhaust valve minus the length of the engine exhaust manifold. The exhaust pressure reflected wave passes through the second pipe 14, the first pipe 13 and the exhaust manifold 31 in sequence at the speed of sound and then reaches the exhaust valve port. The time t for the exhaust pressure reflected wave to reach the exhaust valve is as follows: the sum of the length of the second pipe 14, the length of the first pipe 13, and the length of the exhaust manifold 31 is divided by the speed of sound.

In the embodiment, the time interval between the opening and the closing of the exhaust valve is [ t1, t2], and the time t when the exhaust pressure reflected wave reaches the exhaust valve opening is just within the time interval [ t1, t2] between the opening and the closing of the exhaust valve. At this time, the exhaust pressure reflected wave and the exhaust wave at the exhaust valve port cancel each other out, and the pressure of the exhaust wave at the exhaust valve port is lower than the exhaust pipe average pressure. That is, the pressure at the exhaust port is reduced, reducing the exhaust back pressure at the exhaust port. The residual waste gas in the cylinder body is exhausted more smoothly, the residual waste gas in the cylinder is reduced, the charge coefficient is improved, and the low-speed torque of the engine is improved.

In addition, when the engine 30 is in a partial load condition, the exhaust noise in the low frequency range below 200HZ contributes significantly to the noise in the vehicle, has a large influence on the subjective feeling of the driver and passengers in the vehicle, and is more difficult to eliminate than the exhaust noise in the medium and high frequency ranges. Therefore, a resonant cavity 16 is further arranged in the shell of the front silencer 10, the resonant cavity 16 is close to the silencing cavity 12 and is communicated with the second pipeline 14, the silencing frequency of the resonant cavity 16 is lower than 200Hz of low-frequency noise, and therefore the resonant cavity 16 can reduce the low-frequency noise. Meanwhile, when the generated waste gas passes through the silencing cavity 12, the exhaust noise is also controlled, and the resonant cavity 16 reduces the low-frequency noise after passing through the resonant cavity 16.

That is, in the present embodiment, both exhaust noise and exhaust back pressure are reduced when the engine 30 is in a part load condition. The problem that the reduction of exhaust noise and the reduction of exhaust back pressure are contradictory after the silencer is arranged on an exhaust system is solved.

The second state: when the engine is in a full load condition, the engine 30 rotates at a high speed, and the engine 30 generates more exhaust gas, as described in the background section, the airflow resistance increases, and the exhaust back pressure increases. At this time, the direction change member 20 is switched so that the other end of the first pipe 13 and the third pipe 15 are communicated, and the generated exhaust gas flows out from the shorter third pipe 15 (the thick black arrow in fig. 1 represents the flow direction of the exhaust gas in the third pipe 15).

The exhaust gas in the cylinder body directly flows out from the third pipeline 15 in the front silencer 10, only flows out after passing through the silencing cavity 12, and does not flow through the resonant cavity 16. That is, when the engine 30 is at a high rotation speed, the generated exhaust gas can be discharged quickly, the noise elimination structure through which the exhaust gas flows reduces the exhaust back pressure, the exhaust gas is discharged smoothly, and the dynamic property of the engine is improved. Meanwhile, when the generated waste gas passes through the silencing cavity 12, the exhaust noise is also controlled. The power performance of the engine at high rotating speed is improved.

In conclusion, the exhaust system of the invention has the function of reducing exhaust noise; on the other hand, when the engine 30 rotates at a low speed, the exhaust back pressure at the exhaust valve is reduced, and the low-speed torque of the engine is improved; meanwhile, when the engine 30 rotates at a high speed, the exhaust back pressure of the exhaust pipe is also reduced, and the dynamic property of the engine is improved.

It should be noted that, in different automobile types, the rotating speeds of the cam shafts in the engine are different, and the opening and closing time intervals of the exhaust valve are also different; the length of the exhaust manifold of the engine also varies; this results in the sum of the lengths of the first and second lines 13, 14 being different in different vehicle types. The sum of the lengths of the first pipeline 13 and the second pipeline 14 is not limited in the embodiment of the present invention. As long as the sum of the length of the second pipe 14 and the length of the first pipe 13 satisfies the following condition: the exhaust pressure reflection wave of the exhaust gas discharged from the exhaust valve at the outlet of the second pipe 14 and the exhaust gas wave at the closing time of the exhaust valve cancel each other out. That is, the sum of the length of the second pipe 14 and the length of the first pipe 13: the velocity of the acoustic wave is multiplied by the time interval between the opening and closing of the exhaust valve minus the length of the engine exhaust manifold.

Taking a certain type of automobile as an example, the sum of the lengths of the first and second lines 13, 14 is denoted as L1; the length of the engine exhaust manifold is noted as L2; the rotation speed of the camshaft is changed, and the opening and closing time intervals of the exhaust valve are [ t1, t2]]Where t1 is the minimum time interval and t2 is the maximum time interval. Min_L1＝340×t1-L2；Max_L1340 xt 2-L2. Range of the sum L1 of the lengths of the first line 13 and the second line 14: (340 × t1-L2) to (340 × t 2-L2).

Referring to fig. 2 in conjunction with fig. 1, in the present embodiment, the other end of the first pipeline 13 is communicated with the second pipeline 14, and it can be understood that the first pipeline 13 and the second pipeline 14 are integrally formed. Wherein, commutator 20 includes: the first casing 21 is fixedly arranged outside the first pipeline 13, the first casing 21 is provided with a first inner cavity 21a, and the first inner cavity 21a is communicated with the third pipeline 15. It can be understood that: both the first and second pipes 13 and 14 pass through the first housing 21.

In this embodiment, the first casing 21 is fixedly disposed outside the first pipeline 13, and it can be understood that: the first casing 21 is circumferentially sleeved outside the first pipeline 13, that is, the first casing 21 completely covers the outer circumferential surface of the first pipeline 13. In other embodiments, the first housing may be an outer circumferential surface that partially covers the first pipe in a circumferential direction.

With continued reference to fig. 2, the reversing element 20 further includes a second casing 22, the second casing 22 is located in the first inner cavity 21a and is fixedly disposed outside the first pipeline 13, the second casing 22 has a second inner cavity 22a, and along the length direction of the first pipeline 13, the second casing 22 is provided with an opening 22b communicating the second inner cavity 22a with the first inner cavity 21 a.

Referring to fig. 2, in the present embodiment, the reversing element 20 further includes a cover 23, and the cover 23 is located in the first inner cavity 21a and movably sleeved outside the first pipeline 13 to cover the opening 22 b. The device further comprises an elastic piece 24, and one end of the elastic piece 24 is connected with the cover body 23 along the length direction, and the other end of the elastic piece 24 is connected with the first pipeline 13 or the second shell 22. Thus, the first lumen 21a and the second lumen 22a are made to communicate; the outer surface of the portion of the first pipe 13 located in the second inner cavity 22a is provided with a plurality of through holes 13a, and the exhaust gas in the first pipe 13 can flow into the second inner cavity 22a of the second housing 22 through the through holes 13 a.

In this embodiment, the second casing 22 is fixedly disposed outside the first pipeline 13, and it can be understood that: the second casing 22 is circumferentially sleeved outside the first pipeline 13, that is, the second casing 22 completely covers the outer circumferential surface of the first pipeline 13. In other embodiments, the second housing may partially cover the outer peripheral surface of the first pipeline along the circumferential direction, but it is required to ensure that the through hole provided on the outer surface of the first pipeline is located in the second inner cavity of the second housing.

In this embodiment, the exhaust gas in the first pipeline 13 needs to change the flow direction under the action of the reversing element 20. As long as the cover 23 does not cover the opening 22b, the exhaust gas in the first pipe 13 flows from the first pipe 13 to the third pipe 15, otherwise the exhaust gas in the first pipe 13 flows from the first pipe 13 to the second pipe 14.

In the first state, the pressure of the exhaust gas in the second internal cavity 22a is smaller than the elastic force of the elastic member 24, and the cover 23 is attached to the second housing 22 and covers the opening 22 b. The first line 13 and the second line 14 are in communication,

in the second state, the pressure of the exhaust gas in the second inner cavity 22a is greater than the elastic force of the elastic member 24, the cover 23 moves away from the second housing 22 in the length direction, the opening 22b is not covered by the cover 23, the first inner cavity is communicated with the second inner cavity, and then the first pipeline 13 is communicated with the third pipeline 15.

Referring to fig. 2, in the present embodiment, the elastic member 24 is a spring, and in other embodiments, the elastic member 24 is rubber or other structures having elastic force. The spring has a certain elastic force, and plays a role of supporting the cover body 23 along the length direction.

Specifically, in the first state, when the engine is in a partial load condition, the engine speed is low, the flow rate of the exhaust gas flow is slow, and the exhaust gas in the first pipe 13 flows into the second cavity 22a through the plurality of through holes 13a on the outer peripheral surface of the first pipe 13. The pressure of the exhaust gas in the second cavity 22a is lower than the elastic force of the spring, and the cover 23 is not pushed open, so that the exhaust gas does not enter the first cavity 21a of the first housing 21. Since the other end of the first pipe 13 communicates with the second pipe 14, the exhaust gas in the cylinder block flows from the first pipe 13 to the second pipe 14 to reduce the pressure at the exhaust port.

In the second state, the engine is in a full-load condition, the engine speed is high, the engine generates more exhaust gas, and the exhaust gas in the first pipeline 13 flows into the second inner cavity 22a through the plurality of through holes 13a on the outer peripheral surface of the first pipeline 13. At this time, the pressure of the exhaust gas in the second cavity 22a is large and exceeds the elastic force of the spring, and the lid 23 is pushed open. At this time, the opening 22b of the second housing 22 is not covered, and the first inner chamber 21a and the second inner chamber 22a communicate with each other. The exhaust gas in the first pipe 13 flows into the second inner chamber 22a through the plurality of through holes 13a in the outer circumferential surface of the first pipe 13, and then enters the first inner chamber 21a of the first housing 21. Since the first inner chamber 21a communicates with the third pipe 15, the exhaust gas in the first pipe 13 flows to the third pipe 15.

With continued reference to fig. 2, in the present embodiment, a connecting member 25 is provided on the outer peripheral surface of the first pipe line 13, and the connecting member 25 is welded to the outer surface of the first pipe line 13. In this embodiment, the connection 25 is perpendicular to the outer surface of the first pipeline 13, and in other embodiments, the connection 25 may not be perpendicular to the outer surface of the first pipeline 13. In this embodiment, one end of the spring is connected to the connector 25 and the other end is connected to the cover 33 along the longitudinal direction. In other embodiments, no connector may be provided, and one end of the spring is directly connected to the outer circumferential surface of the first pipe 13 and the other end is connected to the cover 23.

The positional relationship between the elastic member 24 and the cover 23 may satisfy the following condition: in the first state, the pressure of the exhaust gas in the second inner cavity 22a is smaller than the elastic force of the elastic member 24, and the cover 23 is attached to the second housing 22 and covers the opening 22 b; in the second state, the pressure of the exhaust gas in the second internal cavity 22a is greater than the elastic force of the elastic member 24, the cover 23 moves in the longitudinal direction away from the second housing 22, and the first internal cavity 21a and the second internal cavity 22a communicate with each other.

In addition, in the present embodiment, the cover 23 is located between the elastic member 24 and the second housing 22. In other embodiments, referring to fig. 3, along the length direction, one end of the elastic member 24 is connected to the cover 23, and the other end is connected to the second housing 22, and when the pressure of the exhaust gas in the second cavity 22a is smaller than the elastic force of the elastic member 24, the cover 23 is attached to the second housing 22 and covers the opening 22 b.

It should be noted that the direction changing member 20 is not limited to the above structure, and in other embodiments, the direction changing member 20 is a direction changing valve. The exhaust gases in the first line 13 are switched by the reversal of the reversing valve to flow either to the second line 14 or to the third line 15. The directional valve has a first pressure valve (not shown) and a second pressure valve (not shown).

A first pressure valve is located between the first line 13 and the second line 14, and a second pressure valve is located between the first line 13 and the third line 15; in the first state, the pressure of the exhaust gas in the first pipe 13 is greater than the opening pressure of the first pressure valve and less than the opening pressure of the second pressure valve; the first line 13 and the second line 14 are in communication. In the second state, the pressure of the exhaust gas in the first pipe 13 is greater than the opening pressure of the first pressure valve and the opening pressure of the second pressure valve; the first line 13 and the third line 15 are in communication.

With continued reference to fig. 2, in the present embodiment, the outer peripheral surface of the first pipe 13 is provided with a plurality of through holes 13a, and the exhaust gas in the first pipe 13 can flow into the second inner cavity 22a of the second housing 22 through the through holes 13 a. Under the full load condition of the engine, the exhaust gas in the first pipeline 13 flows into the second inner cavity 22a, the first inner cavity 21a and the third pipeline 15 in sequence through the through hole 13 a.

In the present embodiment, the ratio of the sum of the areas of the cross sections of all the through holes 13a to the area of the cross section of the first pipe 13 is 1.2 to 1.5, including 1.2 and 1.5. In this range, the exhaust back pressure at which the exhaust gas in the first pipe 13 flows into the second cavity 22a can be reduced, and the exhaust gas in the first pipe 13 can smoothly flow into the second cavity 22 a. So that the exhaust gases in the first line 13 can be discharged quickly from the third line 15.

With continued reference to fig. 1, the engine exhaust system of the embodiment of the present invention further includes: an engine exhaust manifold 31, the engine exhaust manifold 31 having one end connected to an engine block in the engine and the other end connected to the first pipe 13. In order to further reduce exhaust noise, the engine exhaust system of the present embodiment further includes a rear muffler 40, and one end of the rear muffler 40 is communicated with the sound-deadening chamber 12, and the other end is communicated with the exhaust pipe 50.

In this embodiment, the engine exhaust system further includes: one end of the fourth pipeline 42 is communicated with the second pipeline 14 through the silencing cavity 12, and the other end of the fourth pipeline 42 is communicated with the rear silencer 40; and one end of a fifth pipeline 41 is communicated with the third pipeline 15 through the sound attenuation cavity 12, and the other end of the fifth pipeline 41 is communicated with the rear muffler 40. The exhaust gas passing through the rear muffler 40 is finally discharged to the outside atmosphere 60 through the exhaust pipe 50.

The embodiment of the invention also provides an engine comprising the engine exhaust system.

The embodiment of the invention also provides an automobile comprising the engine.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (10)

1. An engine exhaust system, comprising:

a silencing cavity;

the silencing device comprises a first pipeline, a second pipeline and a third pipeline, wherein the first pipeline, the second pipeline and the third pipeline are provided with reversing pieces, one end of the second pipeline and one end of the third pipeline are communicated with the silencing cavity, and the other ends of the second pipeline and the third pipeline are connected with the reversing pieces; one end of the first pipeline is provided with an engine exhaust manifold connecting interface;

the reversing piece can be switched between a first state and a second state, the first pipeline is communicated with the second pipeline in the first state, and the first pipeline is communicated with the third pipeline in the second state;

the length of the second pipeline is longer than that of the third pipeline, and the sum of the length of the second pipeline and the length of the first pipeline meets the following condition: the exhaust pressure reflected wave of the exhaust gas discharged by the exhaust valve at the outlet of the second pipeline and the exhaust wave at the closing time of the exhaust valve are mutually offset;

the other end of the first pipeline is communicated with the second pipeline;

the reversing piece comprises: the first shell is fixedly arranged outside the first pipeline and provided with a first inner cavity which is communicated with the third pipeline; the second shell is positioned in the first inner cavity and fixedly arranged outside the first pipeline, the second shell is provided with a second inner cavity, and an opening for communicating the second inner cavity with the first inner cavity is formed in the second shell along the length direction of the first pipeline; the cover body is positioned in the first inner cavity, movably sleeved outside the first pipeline and used for covering the opening; the elastic piece is connected with the cover body at one end and connected with the first pipeline or the second shell at the other end along the length direction;

the outer surface of the part of the first pipeline positioned in the second inner cavity is provided with a plurality of through holes;

in the first state, the pressure of the waste gas in the second inner cavity is smaller than the elastic force of the elastic piece, and the cover body is attached to the second shell and covers the opening; in the second state, the pressure of the exhaust gas in the second inner cavity is larger than the elastic force of the elastic piece, the cover body moves back to the second shell along the length direction, and the first inner cavity is communicated with the second inner cavity.

2. The engine exhaust system according to claim 1, wherein the resilient member is a spring or rubber.

3. The engine exhaust system according to claim 1, wherein the ratio of the sum of the areas of the cross sections of all the through holes to the area of the cross section of the first pipe is 1.2 to 1.5.

4. The engine exhaust system according to claim 1 further comprising a resonant cavity adjacent to said muffler cavity and in communication with said second conduit.

5. The engine exhaust system according to claim 4, wherein the resonant cavity has a muffling frequency of 200Hz or less.

6. The engine exhaust system according to claim 1, further comprising:

and one end of the engine exhaust manifold is connected with an engine cylinder body, and the other end of the engine exhaust manifold is connected with the first pipeline.

7. The engine exhaust system according to claim 6, further comprising a rear muffler in communication with the sound-attenuating cavity.

8. The engine exhaust system according to claim 7, further comprising:

one end of the fourth pipeline is communicated with the second pipeline through the silencing cavity, and the other end of the fourth pipeline is communicated with the rear silencer;

and one end of the fifth pipeline is communicated with the third pipeline through the silencing cavity, and the other end of the fifth pipeline is communicated with the rear silencer.

9. An engine comprising an engine exhaust system according to any one of claims 1 to 8.

10. An automobile comprising the engine of claim 9.

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