CN107893714B

CN107893714B - EGR system and control method thereof

Info

Publication number: CN107893714B
Application number: CN201711381278.8A
Authority: CN
Inventors: 刘俊龙; 李卫; 李志杰
Original assignee: Weichai Power Co Ltd
Current assignee: Weichai Power Co Ltd
Priority date: 2017-12-20
Filing date: 2017-12-20
Publication date: 2020-06-02
Anticipated expiration: 2037-12-20
Also published as: CN107893714A

Abstract

The invention relates to the field of engine EGR, and particularly discloses an EGR system and a control method thereof, wherein the system comprises an engine, a gas compressor, a turbine, a control valve and an EGR pipeline, wherein each cylinder of the engine is respectively communicated with an intake manifold and an exhaust manifold; the input end of the compressor is communicated with the atmosphere, and the output end of the compressor is communicated with the air inlet manifold; the turbine is connected with the compressor, the output end of the turbine is communicated with the atmosphere, the input end of the turbine is connected with the exhaust manifold through a first pipeline, one end of the EGR pipeline is communicated with the first pipeline, the other end of the EGR pipeline is communicated with the intake manifold, the control valve is installed on a main pipeline of the exhaust manifold, and the control valve can control the amount of waste gas discharged by a part of cylinders entering the first pipeline. According to the invention, the control valve is used for controlling the amount of the exhaust gas entering the first pipeline, so that the problems that the EGR rate of an EGR system is difficult to improve and the improvement degree depends on the performance of the supercharger in the prior art are solved.

Description

EGR system and control method thereof

Technical Field

The invention relates to the field of engine EGR, in particular to an EGR system and a control method thereof.

Background

Exhaust Gas Recirculation (EGR) is an emission control technique in which a portion of Exhaust Gas generated by a diesel engine or a gasoline engine is led out of an Exhaust line, and an appropriate amount of Exhaust Gas is led into an intake line through a control valve (e.g., an EGR valve) to be mixed with fresh air and then introduced into a combustion chamber to participate in combustion. Because the waste gas contains a large amount of CO₂And CO₂Can not burn but absorb a large amount of heat, thereby reducing the combustion temperature of the mixed gas in the cylinder and further reducing NO_XThe amount of production of (c).

However, the upgrading of the exhaust emission standard and the aging problem of the aftertreatment system make the diesel engine need to improve the EGR rate, but under the condition that the specification of the supercharger is certain (namely, the pressure ratio of the supercharger is certain), the improvement of the EGR rate is difficult.

Specifically, as shown in fig. 1, an engine EGR system in the related art includes: the system comprises an EGR pipeline 1-1, a intercooler 2-1, an engine 3-1, an air inlet pipeline 4-1, a first exhaust pipeline 5-1, a second exhaust pipeline 6-1 and an EGR valve 7-1. Three cylinders (for example, 1 cylinder, 2 cylinders and 3 cylinders) of the engine 3-1 are connected with one end of a first exhaust pipeline 5-1, the other end of the first exhaust pipeline 5-1 is connected with a turbine 8-1, the first exhaust pipeline 5-1 is also connected with one end of an EGR pipeline 1-1, and the other end of the EGR pipeline 1-1 is connected with an air inlet pipeline 4-1. The other three cylinders (e.g. 4, 5, 6) of the engine 3-1 are connected to one end of a second exhaust line 6-1, the other end of the second exhaust line 6-1 is also connected to the turbine 8-1, and the exhaust gas from the 4, 5, 6 cylinders is passed to the turbine 8-1 via the second exhaust line 6-1 and drives the compressor 9-1 to compress the intake air and then to discharge it as exhaust gas.

The operation of the EGR system is as follows: the exhaust gas from the cylinders 1, 2 and 3 is divided into two parts by the first exhaust pipeline 5-1, and one part of the exhaust gas enters the turbine 8-1 through the air inlet of the turbine 8-1 and drives the turbine 8-1, so that the compressor 9-1 is driven to compress the inlet air. Another portion of the exhaust gas is passed via the EGR line 1-1 to the EGR valve 7-1, where the EGR valve 7-1 is opened and the pressure in the EGR line 1-1 is greater than the pressure in the inlet line 4-1, after which the exhaust gas passes through the EGR valve 7-1, is mixed with the inlet air and cooled by the charge air cooler 2-1 and enters the cylinders of the engine 3-1 via the inlet port of the engine 3-1. During the operation of the EGR system, the exhaust gas from the cylinders 1, 2 and 3 generates EGR only when the pressure in front of the turbine 8-1 is larger than the intake pressure, which causes that the EGR rate is difficult to be improved, the improvement of the EGR rate completely depends on the performance of the supercharger, and high requirements are put on the matching of the supercharger.

Accordingly, there is a need for an engine EGR system that is capable of effectively increasing the EGR rate.

Disclosure of Invention

One object of the present invention is: the utility model provides a EGR system to the EGR rate that solves among the prior art EGR system promotes the difficulty, is difficult to realize higher EGR rate, and promotes the problem that the degree relies on booster self performance.

Another object of the invention is: a control method of an EGR system is provided.

In one aspect, the present invention provides an EGR system comprising:

an engine comprising at least two cylinders, each cylinder in communication with an intake manifold and an exhaust manifold, respectively;

the input end of the air compressor is communicated with the atmosphere, and the output end of the air compressor is communicated with the main pipeline of the air inlet manifold;

the turbine is connected with the compressor, the output end of the turbine is communicated with the atmosphere, and the input end of the turbine is communicated with the exhaust manifold through a first pipeline;

one end of the EGR pipeline is communicated with the first pipeline, and the other end of the EGR pipeline is communicated with a main pipeline of the intake manifold;

a control valve installed on a main line of the exhaust manifold, the control valve being capable of controlling an amount of exhaust gas discharged from a portion of the cylinders into the first line.

Preferably, the turbine is further communicated with the control valve through a second pipeline, and the control valve can control the exhaust gas discharged by the part of the cylinders to enter the first pipeline completely, enter the second pipeline completely or enter the first pipeline partially and enter the second pipeline partially.

Preferably, the control valve and the connection between the first pipeline and the main pipeline of the exhaust manifold are located between the connection between the partial cylinders and the connection between the other partial cylinders and the main pipeline of the exhaust manifold.

Preferably, the control valve includes:

the valve comprises a valve body shell, a valve body and a valve body cover, wherein a first port, a second port and a third port are arranged on the valve body shell at intervals;

the valve core is positioned inside the valve body shell;

the control valve is connected to a main pipe of the exhaust manifold through the first port and the third port, the third port is closer to a connection point of the first pipe and the main pipe of the exhaust manifold than the first port, the second port is connected to the second pipe, and the valve element can control the opening degree of the second port or the third port.

Preferably, the part of the cylinders are all communicated with the control valve through the first ports.

Preferably, a fourth port is further disposed on the valve body housing, the fourth port is located between the first port and the third port, one of the partial cylinders is communicated with the fourth port, and the rest of the partial cylinders is communicated with the third port.

Preferably, the valve body housing is cylindrical, and the first port, the second port, and the third port are provided at intervals on a circumferential surface of the valve body housing.

Preferably, the control valve further comprises a stepping motor, the stepping motor is located on one side of the valve body shell and connected with an output shaft of the stepping motor, and the stepping motor can rotate forwards or backwards.

Preferably, the stepping motor is a direct current stepping motor, and the direct current stepping motor is connected with the valve core through a coupler.

Preferably, the control valve further comprises a control module connected with the stepping motor, and the control module can control the position of the valve core in the valve body shell.

Preferably, the system further comprises an intercooler arranged between the output end of the compressor and a main pipeline of the intake manifold, and an EGR cooler and an EGR valve which are arranged on the EGR pipeline.

In another aspect, the present invention provides a method for controlling an EGR system, which is applied to the EGR system according to any one of the above aspects, and includes:

and controlling the control valve to ensure that all the exhaust gas discharged by a part of cylinders enters the first pipeline or all the exhaust gas does not enter the first pipeline.

Preferably, the control valve is controlled to allow a portion of the exhaust gas discharged from a portion of the cylinders to enter the first conduit.

Preferably, the valve core partially seals the third port and completely opens the second port;

or the third port and the second port are all opened;

or the second port is partially sealed, and the third port is completely opened;

one part of the exhaust gas discharged by one part of the cylinders enters the first pipeline, and the other part of the exhaust gas enters the second pipeline.

The invention has the beneficial effects that:

1) the volume of the waste gas that gets into first pipeline through control valve control, and then the atmospheric pressure of control first pipeline, thereby realize the control to the volume that gets into intake manifold waste gas through the EGR pipeline, thereby realize the control to the EGR rate, when the whole first pipeline that gets into of waste gas, atmospheric pressure in the first pipeline reaches the biggest, thereby control through the control valve can realize high EGR rate, the EGR rate promotion difficulty of EGR system among the prior art has been solved, it is difficult to realize higher EGR rate, and the problem that promotion degree relies on booster self performance.

2) When the control valve controls the exhaust gas discharged by a part of cylinders to completely enter the first pipeline, the air pressure in the first pipeline can be maximized, and because the EGR pipeline takes gas from the first pipeline, more EGR gas can enter the intake manifold, so that higher EGR rate can be realized and the performance of the supercharger is not depended on.

3) When the control valve controls all the exhaust gas discharged by one part of cylinders to enter the second pipeline and all the exhaust gas discharged by the other part of cylinders to enter the first pipeline, if the number of the part of cylinders is the same as that of the other part of cylinders, pulse pressurization can be realized.

4) When the control valve controls the exhaust gas discharged by one part of cylinders and the exhaust gas discharged by the other part of cylinders to freely enter the turbine through the first pipeline and the second pipeline to drive the turbine, and the number of the part of cylinders and the other part of cylinders is the same, constant-pressure pressurization can be realized.

5) When the control valve controls a part of the exhaust gas discharged by a part of cylinders to enter the first pipeline, the adjustment of the air pressure of the pipeline at the air intake side of the EGR pipeline can be realized, and the EGR rate is further adjusted.

Drawings

FIG. 1 is a schematic diagram of an EGR system for an engine according to the background of the present disclosure;

FIG. 2 is a schematic diagram of an EGR system configuration (including three ports) according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of an EGR system configuration (including four ports) according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a control valve in an EGR system in accordance with an embodiment of the present invention;

3 fig. 3 5 3 is 3 a 3 sectional 3 view 3 of 3 the 3 control 3 valve 3 shown 3 in 3 fig. 3 4 3 taken 3 along 3 the 3 direction 3 a 3- 3 a 3. 3

In the figure:

1-1, an EGR pipeline; 2-1, an intercooler; 3-1, an engine; 4-1, an air inlet pipeline; 5-1, a first exhaust pipeline; 6-1, a second exhaust pipeline; 7-1, an EGR valve; 8-1, a turbine; 9-1, a gas compressor;

1. an engine; 11. a cylinder; 12. an intake manifold; 13. an exhaust manifold;

21. a compressor; 22. a turbine;

3. an EGR line;

4. a first pipeline;

5. a control valve; 51. a valve body housing; 511. a first port; 512. a second port; 513. a third port; 514. a fourth port; 52. a stepping motor; 53. a valve core; 531. a rotating shaft; 532. a connecting portion; 533. a sealing part; 54. a coupling;

6. a second pipeline;

7. an intercooler;

8. an EGR cooler;

9. an EGR valve.

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.

The embodiment provides an EGR system, as shown in fig. 2 to 5, including an engine 1, a compressor 21, a turbine 22, an EGR pipeline 3, an intercooler 7, an EGR cooler 8, an EGR valve 9, and a control valve 5.

The engine 1 includes at least two cylinders 11, and an intake manifold 12 and an exhaust manifold 13 that communicate with each cylinder 11, respectively, and as shown in fig. 2, the engine 1 in the present embodiment includes six cylinders 11.

The input end of the compressor 21 is communicated with the atmosphere, and the output end of the compressor is communicated with a main pipeline of the air inlet manifold 12; the turbine 22 is connected to the compressor 21, the output of the turbine 22 being connected to the atmosphere and the input being connected via a first line 4 and a second line 4, respectivelyThe pipeline 6 is communicated with the exhaust manifold 13, the intercooler 7 is arranged on a connecting pipeline of a main pipeline of the compressor 21 and the air inlet manifold 12, the intercooler 7 is used for cooling fresh air which is about to enter the air inlet manifold 12, the purpose of reducing the combustion temperature in the air cylinder 11 is achieved, and therefore NO is further reduced_XAfter the exhaust gas enters the turbine 22, the turbine 22 is driven to operate, and the turbine 22 drives the compressor 21 to compress fresh air.

One end of the EGR pipeline 3 is communicated with the first pipeline 4, and the other end is communicated with a main pipeline of the intake manifold 12, in this embodiment, the other end of the EGR pipeline 3 is communicated with a connecting pipeline between the intercooler 7 and the intake manifold 12. The EGR cooler 8 and the EGR valve 9 are both mounted on the EGR line 3, and the EGR valve 9 is located below the EGR cooler 8 in the gas flow direction, the temperature of the exhaust gas entering the intake manifold 12 is reduced by the EGR cooler 8, and the flow rate of the exhaust gas is controlled by the EGR valve 9, thereby facilitating matching of the corresponding EGR rate according to the actual condition of the engine 1.

It will be appreciated that the other end of the EGR line 3 may also communicate with the connection between the output of the compressor 21 and the intercooler 7, in which case the exhaust gases may be further cooled by the intercooler 7 before entering the intake manifold 12, so that the performance requirements for the EGR cooler 8 may be reduced.

The control valve 5 is installed on a main pipeline of the exhaust manifold 13, and the control valve 5 can control a part of the exhaust gas discharged by the cylinders 11 to enter the first pipeline 4 completely, enter the first pipeline 4 partially or not enter the first pipeline 4 completely. Specifically, the control valve 5 and the connection between the first pipeline 4 and the main pipeline of the exhaust manifold 13 are located between the connection between one part of the cylinders 11 and the main pipeline of the exhaust manifold 13 and the connection between the other part of the cylinders 11 and the main pipeline of the exhaust manifold 13. In the present embodiment, a part of the cylinders 11 refers to 4 cylinders, 5 cylinders, and 6 cylinders among the cylinders 11 shown in fig. 2, and the other part of the cylinders 11 refers to 1 cylinder, 2 cylinders, and 3 cylinders.

The control valve 5 includes a valve body housing 51, a stepping motor 52, a valve core 53, a coupling 54, and a control module (not shown in the drawings), the valve body housing 51 is cylindrical, a first port 511, a second port 512, and a third port 513 are sequentially provided on a circumferential surface of the valve body housing 51 at an interval of 90 °, and the first port 511, the second port 512, and the third port 513 have the same hole diameter. The valve core 53 is located in the valve body shell 51 and is fan-shaped, the stepping motor 52 is located outside the valve body shell 51, the rotating shafts of the stepping motor 52 and the valve core 53 are connected through a coupler 54, and the valve core 53 can rotate in the inner cavity of the valve body shell 51 under the driving of the stepping motor 52. The control module is connected with the stepping motor 52, and the control module can control the stepping motor 52 to run or stop, so that the position of the valve core 53 in the valve body shell 51 can be controlled, and the valve core 53 can continuously rotate at fixed angle intervals relative to the valve body shell 51 by changing the pulse number input to the stepping motor 52 by the control module. In the present embodiment, when the spool 53 is rotated to a position facing the first port 511, the second port 512, or the third port 513, the spool 53 can seal the first port 511, the second port 512, or the third port 513, and when the spool 53 is rotated to the middle of any adjacent two ports among the first port 511, the second port 512, and the third port 513, the spool 53 does not overlap the first port 511, the second port 512, or the third port 513. It should be noted that the stepping motor 52 in this embodiment is preferably a dc stepping motor, and can rotate in the forward direction or in the reverse direction, so that the position of the valve element 53 can be continuously adjusted according to the real-time operating condition of the engine 1.

The valve body 53 includes a rotation shaft 531 connected to the coupling 54, two fan-shaped coupling portions 532 fixedly coupled to the top and bottom of the rotation shaft 531, respectively, and sealing portions 533 coupled to fan-shaped ends of the two coupling portions 532, respectively, to seal the ports when the sealing portions 533 are rotated to positions facing the ports. The valve core 53 of the present embodiment has a hollow structure between two connecting portions 532, and is communicated with the cavity inside the valve body housing 51, and occupies a smaller space of the cavity, so that in the process of rotating the valve core 53, the change of the air pressure in the cavity inside the valve body housing 51 is not caused, the larger air flow disturbance in the cavity inside the valve body housing 51 is not caused, and the load of the stepping motor 52 is reduced.

As shown in fig. 2, the control valve 5 is mounted on the main pipe of the exhaust manifold 13 through a first port 511 and a third port 513, and the third port 513 is connected to the second pipe 6 through a second port 512 near the junction of the first pipe 4 and the main pipe of the exhaust manifold 13 with respect to the first port 511.

It will be appreciated that a fourth port 514 may also be provided on the outer periphery of the valve body housing 51, as shown in fig. 5, the fourth port 514 being located between the first port 511 and the third port 513 and opposite the second port 512, the fourth port 514 being spaced 90 ° from the first port 511 and being of uniform diameter. As shown in fig. 3, the control valve 5 is installed on the main pipe of the exhaust manifold 13 through a first port 511 and a third port 513, and the third port 513 is connected to the exhaust pipe of 4 cylinders through a second port 512 and a second pipe 6 near the connection of the first pipe 4 and the main pipe of the exhaust manifold 13 with respect to the first port 511, and through a fourth port 514.

The present embodiment further provides a control method of an EGR system, which is applicable to an EGR system in the foregoing scheme, and the control method includes:

by controlling the control valve 5, a part of the exhaust gas discharged from the cylinder 11 is completely introduced into the first pipeline 4, partially introduced into the first pipeline 4 or not introduced into the first pipeline 4.

Through controlling the valve core 53 to swing between the third port 513 and the second port 512, the exhaust gas exhausted by 4 cylinders, 5 cylinders and 6 cylinders can completely enter the first pipeline 4 through the third port 513, one part of the exhaust gas enters the first pipeline 4, the other part of the exhaust gas enters the second pipeline 6 or completely enters the second pipeline 6, and the continuous control of the gas flow entering the first pipeline 4 and the second pipeline 6 can be realized, so that the continuous control of the gas pressure of the first pipeline 4 is realized, namely the continuous control of the gas pressure of the gas taking side of the EGR pipeline 3 is realized, and the EGR rate can be controlled according to the actual working condition of the engine 1. The method comprises the following specific steps:

1) the direct current stepping motor drives the valve core 53 to rotate to a position opposite to the second port 512, the valve core 53 seals the second port 512, at the moment, the third port 513 is completely opened, the exhaust gas discharged by the

cylinders

4, 5 and 6 enters the main pipeline of the exhaust manifold 13 at the other side of the control valve 5 through the third port 513 from the main pipeline of the exhaust manifold 13 at one side of the control valve 5, and enters the first pipeline 4 together with the exhaust gas discharged by the cylinders 1, 2 and 3, at the moment, the exhaust gas discharged by all the cylinders 11 enters the first pipeline 4, so that the air pressure in the first pipeline 4 reaches the maximum, the pressure at the air taking side of the EGR pipeline 3 is improved, more EGR gas can enter the main pipeline of the air inlet manifold 12, and the EGR rate is improved.

2) The dc stepper motor rotates the valve spool 53 to a position where it overlaps the third port 513 or overlaps the second port 512, at which time the valve spool 53 partially seals the third port 513 or partially seals the second port 512, and a portion of the exhaust gas from 4, 5, and 6 cylinders enters the first pipe 4 and another portion enters the second pipe 6. By controlling the overlapping area of the spool 53 and the third port 513 or the second port 512, the amount of exhaust gas discharged from the 4, 5, and 6 cylinders entering the first pipe 4 can be controlled, and thus control of the EGR rate can be achieved.

It should be noted that when there is overlap between the spool 53 and the second port 512, the third port 513 is fully open and most of the exhaust gas enters the first pipe 4, and when there is overlap between the spool 53 and the third port 513, the second port 512 is fully open and most of the exhaust gas enters the second pipe 6.

3) The direct current stepping motor drives the valve core 53 to rotate to the middle of the third port 513 and the second port 512, and the valve core is not overlapped with the second port 512 and the third port 513, at the moment, the third port 513 and the second port 512 are all opened, gas circuits on two sides of the control valve 5 are completely communicated, waste gas discharged by 1 cylinder to 6 cylinders can enter the turbine 22 from the first pipeline 4 and the second pipeline 6 to pressurize the turbine 22, at the moment, the pipeline structure of the EGR system is consistent with that of a conventional constant-pressure pressurizing pipeline, and constant-pressure pressurization of the engine 1 can be realized.

4) The direct current stepping motor drives the valve core 53 to rotate to a position opposite to the third port 513, the valve core 53 seals the third port 513, at the moment, the second port 512 is completely opened, all the exhaust gas discharged by the

cylinders

4, 5 and 6 enters the second pipeline 6, and all the exhaust gas discharged by the cylinders 1, 2 and 3 enters the first pipeline 4, at the moment, the pipeline structure of the EGR system is consistent with that of a conventional pulse pressurization pipeline structure, and pulse pressurization of the engine 1 can be realized.

In the embodiment, the quantity of the exhaust gas discharged by a part of cylinders 11 entering the first pipeline 4 can be controlled through the control valve 5, so that the air pressure of the first pipeline 4 is controlled, the control on the quantity of the exhaust gas entering the intake manifold 12 through the EGR pipeline 3 is realized, the control on the EGR rate is further realized, and when the exhaust gas completely enters the first pipeline 4, the air pressure in the first pipeline 4 reaches the maximum, so that the high EGR rate can be realized, and the problems that the EGR rate of an EGR system in the prior art is difficult to promote, the higher EGR rate is difficult to realize, and the promotion degree depends on the performance of a supercharger in the prior art are solved; meanwhile, the function of the asymmetrical runner supercharger and the function of the symmetrical runner supercharger can be realized, and the asymmetry can be continuously adjusted through the control valve 5 according to actual requirements.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An EGR system, comprising:

an engine (1), said engine (1) comprising at least two cylinders (11), each of said cylinders (11) being in communication with an intake manifold (12) and an exhaust manifold (13), respectively;

the input end of the compressor (21) is communicated with the atmosphere, and the output end of the compressor (21) is communicated with a main pipeline of the air inlet manifold (12);

a turbine (22), the turbine (22) being connected to the compressor (21), the output of the turbine (22) being in communication with the atmosphere and the input being in communication with the exhaust manifold (13) via a first conduit (4);

an EGR pipeline (3), one end of the EGR pipeline (3) is communicated with the first pipeline (4), and the other end of the EGR pipeline is communicated with a main pipeline of the intake manifold (12);

the exhaust gas purification device comprises a control valve (5), the control valve (5) is installed on a main pipeline of an exhaust manifold (13), the control valve (5) can control the amount of exhaust gas discharged by one part of cylinders (11) entering a first pipeline (4), the exhaust gas discharged by the other part of cylinders (11) entering the first pipeline (4), a turbine (22) is communicated with the control valve (5) through a second pipeline (6), and the control valve (5) can control the exhaust gas discharged by one part of cylinders (11) to completely enter the first pipeline (4), completely enter a second pipeline (6) or control one part of exhaust gas to enter the first pipeline (4) and the other part of exhaust gas to enter the second pipeline (6).

2. An EGR system according to claim 1, characterized in that the control valve (5) and the connection of the first line (4) to the main line of the exhaust manifold (13) are each located between the connections of the cylinders (11, 11) and the other cylinders (11) to the main line of the exhaust manifold (13).

3. An EGR system according to claim 1, characterized in that the control valve (5) comprises:

the valve body shell (51), wherein a first port (511), a second port (512) and a third port (513) are arranged on the valve body shell (51) at intervals;

a valve core (53), wherein the valve core (53) is positioned inside the valve body shell (51);

the control valve (5) is connected to a main line of the exhaust manifold (13) through the first port (511) and the third port (513), and the third port (513) is closer to a connection point of the first line (4) and the main line of the exhaust manifold (13) than the first port (511), the second port (512) is connected to the second line (6), and the valve body (53) can control an opening degree of the second port (512) or the third port (513).

4. An EGR system according to claim 3, characterized in that said part of cylinders (11) are connected to said first port (511).

5. An EGR system according to claim 3, wherein the valve body housing (51) is further provided with a fourth port (514), one cylinder (11) of the portion of cylinders (11) communicates with the fourth port (514), and the remaining cylinders (11) of the portion of cylinders (11) are connected to the first port (511).

6. An EGR system according to any of claims 3-5 wherein said valve body housing (51) is cylindrical and said first port (511), said second port (512) and said third port (513) are spaced around the circumference of said valve body housing (51).

7. An EGR system according to any of claims 3-5 characterized in that the control valve (5) further comprises a stepper motor (52), the stepper motor (52) being located at one side of the valve body housing (51) and connected to the valve spool (53), the stepper motor (52) being capable of forward or reverse rotation.

8. An EGR system according to claim 7 wherein said stepper motor (52) is a dc stepper motor, said dc stepper motor being connected to said valve cartridge (53) by a coupling (54).

9. An EGR system according to claim 7, characterized in that the control valve (5) further comprises a control module connected to the stepper motor (52), the control module being capable of controlling the position of the spool (53) in the valve body housing (51).

10. An EGR system according to claim 1, further comprising an intercooler (7) mounted between the output of the compressor (21) and the main line of the intake manifold (12), an EGR cooler (8) and an EGR valve (9) mounted on the EGR line (3).

11. A control method of an EGR system, which is applied to an EGR system according to any one of claims 1 to 10, comprising:

and controlling the control valve (5) to ensure that all the exhaust gas discharged by a part of the cylinders (11) enters the first pipeline (4) or not enter the first pipeline (4).

12. A control method of an EGR system according to claim 11, characterized in that the control valve (5) is controlled to let a part of the exhaust gases from a part of the cylinders (11) into the first line (4).

13. A control method of an EGR system according to claim 12, characterized in that the turbine (22) communicates with the control valve (5) through a second pipe (6), a first port (511), a second port (512) and a third port (513) are provided on the control valve (5), the control valve (5) is connected to the main pipe of the exhaust manifold (13) through the first port (511) and the third port (513), and the third port (513) is closer to the connection of the first pipe (4) and the main pipe of the exhaust manifold (13) than the first port (511), and the second port (512) is connected to the second pipe (6);

the control valve (5) partially seals the third port (513) and fully opens the second port (512);

or both the third port (513) and the second port (512) are opened;

or the second port (512) is partially sealed and the third port (513) is fully open;

a part of the exhaust gases discharged by a part of the cylinders (11) enters the first pipeline (4), and the other part of the exhaust gases enters the second pipeline (6).