A control method of EGR system, EGR system and automobile

Abstract

The embodiment of the present application provides a control method of an EGR system, an EGR system and an automobile, wherein the EGR system includes an engine, an EGR valve and a mixing valve, and the control method includes: determining that the engine enters a load operation state; controlling the EGR system to enter a segmented control mode, obtaining the current speed and current torque of the engine; comparing the current torque with the set torque corresponding to the current speed; and according to the comparison result, performing closed-loop control on one of the EGR valve and the mixing valve, and performing open-loop control on the other of the EGR valve and the mixing valve. The control method of the EGR system of the embodiment of the present application can effectively improve the performance of the engine.

Description

Technical Field

[0001] The present application relates to the field of automobile technology, and in particular to a control method of an EGR system, an EGR system and an automobile. Background Art

[0002] Hybrid vehicles develop their engines by matching them with a low-pressure EGR system (low-pressure exhaust gas recirculation system), which is an important technical means to improve engine combustion efficiency.

[0003] In the related art, the low-pressure EGR system includes a mixing valve, an EGR valve (exhaust gas recirculation valve) and a throttle valve. When the low-pressure EGR system is turned on, there is a situation where the mixing valve, the EGR valve and the throttle valve are linked. Specifically, when the throttle valve is in the open state, the opening of the mixing valve and the opening of the EGR valve are controlled to jointly control the intake flow and intake pressure of the engine, wherein the throttle valve and the EGR valve realize the closed-loop control of the intake flow of the engine, and the mixing valve realizes the closed-loop control of the intake pressure.

[0004] However, the coordinated control of the throttle, mixing valve and EGR valve will cause conflicts. In short, the intake flow required by the engine needs to be achieved by constantly changing the valve opening of the mixing valve, throttle and EGR valve. As a result, it is easy for each valve to be adjusted too frequently, which prolongs the engine stabilization time, and the engine speed and torque are prone to fluctuations, which cannot effectively guarantee the engine performance. Summary of the invention

[0005] In view of this, the main purpose of the embodiments of the present application is to provide a control method of an EGR system, an EGR system and a vehicle that can improve engine performance.

[0006] To achieve the above purpose, the technical solution of the embodiment of the present application is implemented as follows:

[0007] A first aspect of an embodiment of the present application provides a control method for an EGR system, the EGR system comprising an engine, an EGR valve and a mixing valve, the control method comprising:

[0008] Determining that the engine enters a load operation state;

[0009] Controlling the EGR system to enter a segmented control mode, and obtaining a current speed and a current torque of the engine;

[0010] comparing the current torque with a set torque corresponding to the current speed;

[0011] According to the comparison result, one of the EGR valve and the mixing valve is controlled in a closed loop, and the other of the EGR valve and the mixing valve is controlled in an open loop.

[0012] In one embodiment, the engine operation area includes a fuel economy area and a non-fuel economy area, and the set torque is the torque corresponding to the current speed on the boundary line between the fuel economy area and the non-fuel economy area.

[0013] In one embodiment, the control method includes:

[0014] If the current torque increases from less than the set torque to equal to or greater than the sum of the set torque and a first adjustment value, the EGR valve is closed-loop controlled and the mixing valve is open-loop controlled, wherein the first adjustment value is greater than or equal to 0; and / or,

[0015] If the current torque decreases from greater than the set torque to equal to or less than the difference between the set torque and a second adjustment value, the EGR valve is open-loop controlled and the mixing valve is closed-loop controlled, wherein the second adjustment value is greater than or equal to 0.

[0016] In one implementation manner, the first adjustment value is 10 N·m; and / or the second adjustment value is 10 N·m.

[0017] In one implementation, the closed-loop control of the EGR valve includes:

[0018] Calculating a current EGR flow rate through the EGR valve according to a throttling equation;

[0019] comparing the current EGR flow rate with a set EGR flow rate, wherein the set EGR flow rate is an EGR flow rate determined according to the current speed and the current torque;

[0020] According to the comparison result, the valve opening of the EGR valve is adjusted to make the current EGR flow rate equal to the set EGR flow rate.

[0021] In one embodiment, the EGR system includes a throttle valve. After the EGR valve is closed-loop controlled and the mixing valve is open-loop controlled, the control method includes:

[0022] Calculating the current mixed gas flow rate flowing through the throttle valve according to the throttle equation;

[0023] comparing a current air flow rate passing through the mixing valve with a required air flow rate of the engine, wherein the current air flow rate is a difference between the current mixed gas flow rate and the current EGR flow rate;

[0024] The throttle valve is controlled in a closed loop according to the comparison result.

[0025] In one implementation, the open-loop control of the mixing valve includes:

[0026] The valve opening of the mixing valve is controlled to be maintained at a set angle according to the current rotation speed and the current torque.

[0027] In one implementation, the open-loop control of the EGR valve includes:

[0028] The valve opening of the EGR valve is controlled to be maintained at a set angle according to the current speed and the current torque.

[0029] In one embodiment, the closed-loop control of the mixing valve includes:

[0030] Calculating a current air flow rate through the mixing valve according to a throttling equation;

[0031] comparing the current air flow rate with a required air flow rate of the engine;

[0032] According to the comparison result, the valve opening of the mixing valve is adjusted to make the current air flow equal to the required air flow.

[0033] In one embodiment, the EGR system includes a throttle valve. After the EGR valve is open-loop controlled and the mixing valve is closed-loop controlled, the control method includes:

[0034] Comparing the current mixed gas flow rate flowing through the throttle valve with the required mixed gas flow rate of the engine, wherein the current mixed gas flow rate is the sum of a set EGR flow rate and the current air flow rate, and the set EGR flow rate is an EGR flow rate determined according to the current speed and the current torque;

[0035] The throttle valve is controlled in a closed loop according to the comparison result.

[0036] In one embodiment, the control method includes:

[0037] If the engine is switched from the load operation state to the no-load operation state, the EGR system is controlled to exit the segmented control mode.

[0038] A second aspect of the embodiment of the present application provides an EGR system, the EGR system is used to implement the control method described in the first aspect of the embodiment of the present application, and the EGR system includes:

[0039] engine;

[0040] An EGR valve, the EGR valve being used to control a current EGR flow entering the engine;

[0041] a mixing valve, the mixing valve being used to control the current air flow entering the engine;

[0042] A memory, wherein the memory is used to store computer executable instructions;

[0043] An executor is used to execute the computer executable instructions to implement the steps of the control method described in the first aspect of the embodiment of the present application.

[0044] In one embodiment, the EGR system is a low-pressure EGR system.

[0045] A third aspect of an embodiment of the present application provides a vehicle, comprising the EGR system described above.

[0046] The embodiment of the present application provides a control method of an EGR system, an EGR system and an automobile. The EGR system includes an engine, an EGR valve and a mixing valve. The control method of the EGR system can compare the current torque with the set torque corresponding to the current speed, and according to the comparison result, perform closed-loop control on one of the EGR valve and the mixing valve, and perform open-loop control on the other of the EGR valve and the mixing valve. In the control method, the valve opening of the EGR valve and the mixing valve using open-loop control can be quickly adjusted, and at most the valve opening of the EGR valve and the mixing valve using closed-loop control and the valve opening of the throttle valve need to be coordinated and adjusted. As a result, the coordinated control between the valves in the EGR system can be reduced, so that the opening of each valve can be quickly adjusted to the right position, thereby greatly reducing the stabilization time of the engine, and avoiding frequent fluctuations in the speed and torque of the engine, thereby improving the performance of the engine to ensure its performance output. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a flow chart of a control method of an EGR system according to an embodiment of the present application;

[0048] Figure 2 For the realization of Figure 1 A schematic diagram of the structure of the EGR system of the control method;

[0049] Figure 3 This is a flow chart of a control method of an EGR system according to another embodiment of the present application.

[0050] Description of Reference Numerals

[0051] Engine 10; turbine 20; three-way catalytic converter 30; GPF 40; GPF temperature sensor 41; GPF differential pressure sensor 42; EGR valve 50; EGR valve temperature sensor 51; EGR valve differential pressure sensor 52; EGR cooler 53; throttle valve 60; compressor 70; mixing valve 80; air filter 90. DETAILED DESCRIPTION

[0052] It should be noted that, in the absence of conflict, the embodiments and technical features in the embodiments of the present application can be combined with each other, and the detailed description in the specific implementation method should be understood as an explanation of the purpose of the present application and should not be regarded as an improper limitation on the present application.

[0053] An embodiment of the present application provides a control method for an EGR system, wherein the EGR system includes an engine 10, an EGR valve 50 and a mixing valve 80. Figure 1 , the control method of the EGR system comprises the following steps:

[0054] Step S1: Determine whether the engine 10 enters a load operation state;

[0055] Step S2: Control the EGR system to enter the segmented control mode, and obtain the current speed and current torque of the engine 10;

[0056] Step S3: comparing the current torque with the set torque corresponding to the current speed;

[0057] Step S4 : Based on the comparison result, one of the EGR valve 50 and the mixing valve 80 is closed-loop controlled, and the other of the EGR valve 50 and the mixing valve 80 is open-loop controlled.

[0058] Specifically, the load operation state of the engine 10 refers to the state in which the engine 10 operates under load, which is opposite to the no-load operation state of the engine 10 , wherein the no-load operation state of the engine 10 refers to the no-load operation state (such as idling condition).

[0059] It should be noted that the specific method for determining that the engine 10 enters the load operation state can be determined based on the EGR rate (i.e., the ratio of the amount of recirculated exhaust gas to the total amount of intake air sucked into the cylinder). Specifically, the engine 10 is determined to enter the load operation state by determining that the EGR rate is greater than 0.

[0060] The current speed of the engine 10 refers to the real-time speed of the engine 10 during operation, and the current torque refers to the real-time torque of the engine 10 during operation.

[0061] When the current speed is at different values, there are corresponding set torques of different values, as shown in Table 1 (the specific values ​​of the set torques are not given in Table 1, and are only replaced by letters as examples).

[0062] Table 1

[0063] Current speed rpm 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 Set torque N·m A B C D E F G H I J

[0064] In fact, in Table 1, the speed between the current speed of 1000 rpm and 1500 rpm can be determined by interpolation. In other words, the correspondence between the current speed and the set torque is continuous, that is, it is a continuous line in the speed torque coordinate system.

[0065] Exemplarily, the set torque of the engine 10 is defined by the EMS system (engine 10 management system), and the curve of the segmented control is determined according to the actual operating point of the engine 10, so that the set torque is calibrable.

[0066] It should be noted that the specific correspondence method between the set torque and the current rotation speed can be determined according to actual conditions.

[0067] For example, the operating region of the engine 10 includes a fuel economy region and a non-fuel economy region, and the set torque is the torque corresponding to the current speed at the boundary between the fuel economy region and the non-fuel economy region.

[0068] That is to say, at the current speed, if the current torque is greater than the set torque, the engine 10 in this working condition operates in the fuel economy zone, and has good fuel economy. If the current torque is less than the set torque, the engine 10 in this working condition does not operate in the fuel economy zone, that is, it is in the non-fuel economy zone, and does not have good fuel economy.

[0069] Based on the comparison result between the current torque and the set torque, one of the EGR valve 50 and the mixing valve 80 is selectively controlled in a closed loop and the other is selectively controlled in an open loop.

[0070] For example, see Figure 3 , if the current torque is greater than the set torque, the EGR valve 50 is closed-loop controlled and the mixing valve 80 is open-loop controlled. In this case, the engine 10 is in the fuel economy zone, and the basic principle is that the EGR valve 50 is closed-loop controlled in the area with low fuel consumption. Therefore, the accuracy of the EGR rate can be guaranteed by adjusting the valve opening of the EGR valve 50, thereby ensuring fuel economy. At the same time, the mixing valve 80 is combined with the open-loop control so that the mixing valve 80 and the EGR valve 50 can be quickly placed in place, and the control is simple and can be applied to transient conditions.

[0071] For example, see Figure 3 If the current torque is less than the set torque and the engine 10 is not operating in the fuel economy zone, the EGR valve 50 is open-loop controlled and the mixing valve 80 is closed-loop controlled. This allows the EGR valve 50 and the mixing valve 80 to quickly land without coordinated control, thereby saving control time.

[0072] Another embodiment of the present application provides an EGR system for implementing the control method described above. The EGR system includes an engine 10, an EGR valve 50, a mixing valve 80, a storage device and an actuator.

[0073] Specifically, the EGR valve 50 is used to control the current EGR flow entering the engine 10, the mixing valve 80 is used to control the current air flow entering the engine 10, the memory is used to store computer executable instructions, and the actuator is used to execute the computer executable instructions to implement the steps of the control method described above.

[0074] It should be noted that the EGR system may be a low-pressure EGR system, which is different from a high-pressure EGR system that takes gas before the turbine 20 does work. In this system, part of the exhaust gas is discharged after the turbine 20 does work, resulting in a lower gas pressure in the cylinder.

[0075] For example, see Figure 2 The EGR system may further include a turbine 20, a three-way catalyst 30, a GPF 40 (particulate trap), a GPF temperature sensor 41, a GPF differential pressure sensor 42, an EGR valve temperature sensor 51, an EGR valve differential pressure sensor 52, an EGR cooler 53, a throttle 60, a compressor 70, and an air filter 90. The throttle 60 may be an electronic throttle.

[0076] In addition, the EGR system may also adopt other types of EGR systems.

[0077] Yet another embodiment of the present application provides a vehicle, comprising the EGR system described above.

[0078] The control method of the EGR system of the embodiment of the present application can compare the current torque with the set torque corresponding to the current speed, and according to the comparison result, close-loop control is performed on one of the EGR valve 50 and the mixing valve 80, and open-loop control is performed on the other of the EGR valve 50 and the mixing valve 80. In this control method, the valve opening of the EGR valve 50 and the mixing valve 80 using open-loop control can be quickly adjusted, and at most the valve opening of the EGR valve 50 and the mixing valve 80 using closed-loop control and the valve opening of the throttle valve 60 need to be adjusted in linkage. As a result, the coordinated control between the valves in the EGR system can be reduced, so that the opening of each valve can be quickly adjusted to the right position, thereby greatly reducing the stabilization time of the engine 10, and avoiding frequent fluctuations in the speed and torque of the engine 10, thereby improving the performance of the engine 10 to ensure its performance output.

[0079] In one embodiment, the control method of the EGR system may further include the following steps:

[0080] If the current torque increases from less than the set torque to equal to or greater than the sum of the set torque and the first adjustment value, the EGR valve 50 is closed-loop controlled and the mixing valve 80 is open-loop controlled, wherein the first adjustment value is greater than or equal to zero.

[0081] Specifically, the point corresponding to the sum of the set torque and the first adjustment value is the first switching point for switching the EGR valve 50 from open-loop control to closed-loop control, and for switching the mixing valve 80 from closed-loop control to open-loop control. According to actual needs, the switching can be performed when the current torque is exactly equal to the first switching point, or when it exceeds the first switching point.

[0082] That is, according to different actual working conditions, when the current torque of the engine 10 increases from a smaller value to a larger value, the switching point of the control method of the EGR valve 50 and the mixing valve 80 is the first switching point.

[0083] If the first adjustment value is 0, the first switching point still corresponds to the set torque. Of course, the size of the first adjustment value can be determined according to actual conditions, for example, the first adjustment value is 10 N·m.

[0084] In one embodiment, the control method of the EGR system may further include the following steps:

[0085] If the current torque decreases from greater than the set torque to equal to or less than the difference between the set torque and the second adjustment value, the EGR valve 50 is open-loop controlled and the mixing valve 80 is closed-loop controlled, wherein the second adjustment value is greater than or equal to zero.

[0086] Specifically, the point corresponding to the difference between the set torque and the second adjustment value is the second switching point for switching the EGR valve 50 from closed-loop control to open-loop control, and for switching the mixing valve 80 from open-loop control to closed-loop control. According to actual needs, the switching can be performed when the current torque is exactly equal to the second switching point, or when the current torque is exactly above the second switching point.

[0087] If the second adjustment value is 0, the second switching point still corresponds to the set torque. Of course, the size of the second adjustment value can be determined according to actual conditions, for example, the second adjustment value is 10 N·m.

[0088] That is, according to different actual working conditions, when the current torque of the engine 10 decreases from a larger value to a smaller value, the switching point of the control method of the EGR valve 50 and the mixing valve 80 is the second switching point.

[0089] It should be noted that when the current torque of the engine 10 is hovering around the set torque, if at least one of the first adjustment value and the second adjustment value is not 0, it can be avoided that the first switching point and the second switching point both correspond to the set torque, thereby avoiding the EGR valve 50 and the mixing valve 80 from switching back and forth between closed-loop control and open-loop control, and preventing damage to the EGR system.

[0090] In one embodiment, the closed-loop control of the EGR valve 50 includes:

[0091] Calculate the current EGR flow through the EGR valve 50 according to the throttling equation;

[0092] Comparing the current EGR flow rate with the set EGR flow rate, wherein the set EGR flow rate is the EGR flow rate determined according to the current speed and the current torque;

[0093] According to the comparison result, the valve opening of the EGR valve 50 is adjusted so that the current EGR flow rate is equal to the set EGR flow rate. Thus, the current EGR flow rate of the EGR valve 50 can be prevented from deviating from the set EGR flow rate, thereby ensuring the accuracy of the EGR rate.

[0094] Specifically, the throttling equation is:

[0095]

[0096] In which, taking the EGR valve 50 as an example, m is the current EGR flow rate, C d is the flow coefficient, A is the flow area of ​​the EGR valve 50 determined by the opening of the EGR valve 50, and P us is the pressure on the upstream side of the EGR valve 50, P ds is the pressure on the downstream side of the EGR valve 50, f(P us / P ds ) is the pressure ratio function, R is the gas constant, and T is the EGR valve 50 temperature.

[0097] The current EGR flow rate is the real-time exhaust gas flow rate flowing through the EGR valve 50. The set EGR flow rate is a preset fixed value, and different set EGR flows correspond to different current speeds and current torques. If the current EGR flow rate is different from the corresponding set EGR flow rate, the current EGR flow rate is adjusted and corrected by adjusting the valve opening of the EGR valve 50.

[0098] In one embodiment, the open-loop control of the mixing valve 80 includes:

[0099] The valve opening of the mixing valve 80 is controlled to be maintained at a set angle according to the current speed and the current torque. In other words, the valve opening of the mixing valve 80 is fixed at an opening corresponding to the current speed and the current torque. That is, the valve opening of the mixing valve 80 in this case is only related to the current speed and the current torque, and has nothing to do with the current air flow rate flowing through the mixing valve 80. In this way, the valve opening adjustment of the mixing valve 80 can be completed quickly to save control time.

[0100] In one embodiment, after the EGR valve 50 is closed-loop controlled and the mixing valve 80 is open-loop controlled, the control method of the EGR system may further include the following steps:

[0101] Calculate the current mixture flow rate flowing through the throttle valve 60 according to the throttle equation;

[0102] Compare the current air flow through the mixing valve 80 with the required air flow of the engine 10, wherein the current air flow is the difference between the current mixed gas flow and the current EGR flow;

[0103] The throttle valve 60 is controlled in a closed loop according to the comparison result.

[0104] Specifically, the above steps are steps of performing closed-loop control on the throttle valve 60 when the current torque increases from less than the set torque to equal to or greater than the sum of the set torque and the first adjustment value.

[0105] The exhaust gas from the EGR and the fresh air from the mixing valve 80 are mixed to form a mixed gas flowing through the throttle valve 60. The current mixed gas flow rate refers to the mixed gas flow rate flowing through the throttle valve 60, and the current air flow rate refers to the fresh air flow rate flowing through the mixing valve 80. The current mixed gas flow rate can be calculated according to the throttle equation at the throttle valve 60, and the current EGR flow rate can be calculated according to the throttle equation at the EGR valve 50. The current air flow rate can be obtained by subtracting the two.

[0106] In addition, since the mixing valve 80 is in open-loop control, its valve opening is fixed at the current speed and current torque. Therefore, the throttle valve 60 can be adjusted by performing closed-loop control on the throttle valve 60 so that the current air flow rate flowing through the mixing valve 80 (which is also the air flow rate portion of the current mixed air flow rate flowing through the throttle valve 60) can meet the required air flow rate of the engine 10. If the current air flow rate is different from the required air flow rate of the engine 10, the valve opening of the throttle valve 60 is adjusted to adjust and correct the current air flow rate.

[0107] In one embodiment, the open-loop control of the EGR valve 50 includes:

[0108] The valve opening of the EGR valve 50 is controlled to be maintained at a set angle according to the current speed and the current torque. In other words, the valve opening of the EGR valve 50 is fixed at an opening corresponding to the current speed and the current torque. That is, the valve opening of the EGR valve 50 in this case is only related to the current speed and the current torque, and has nothing to do with the current EGR flow rate flowing through the EGR valve 50. In this way, the valve opening adjustment of the EGR valve 50 can be completed quickly to save control time.

[0109] In one embodiment, the closed-loop control of the mixing valve 80 includes:

[0110] Calculate the current air flow through the mixing valve 80 according to the throttling equation;

[0111] comparing the current air flow rate with the required air flow rate of the engine 10;

[0112] According to the comparison result, the valve opening of the mixing valve 80 is adjusted so that the current air flow rate is equal to the required air flow rate.

[0113] Specifically, the current air flow is calculated based on the throttling equation at the mixing valve 80. If the current air flow is different from the required air flow of the engine 10, the current air flow is adjusted and corrected by adjusting the valve opening of the mixing valve 80 so that the air flowing through the mixing valve 80 meets the air demand of the engine 10.

[0114] In one embodiment, after the EGR valve 50 is open-loop controlled and the mixing valve 80 is closed-loop controlled, the control method includes:

[0115] Compare the current mixed gas flow rate flowing through the throttle valve 60 with the required mixed gas flow rate of the engine 10, wherein the current mixed gas flow rate is the sum of the set EGR flow rate and the current air flow rate, and the set EGR flow rate is the EGR flow rate determined according to the current speed and the current torque;

[0116] The throttle valve 60 is controlled in a closed loop according to the comparison result.

[0117] Specifically, the above steps are steps of performing closed-loop control on the throttle valve 60 when the current torque decreases from being greater than the set torque to being equal to or less than the difference between the set torque and the second adjustment value.

[0118] Since the EGR valve 50 is in open-loop control, its valve opening is fixed at the current speed and current torque, and the current EGR flow through the EGR valve 50 is consistent with the set EGR flow. The current air flow can be calculated according to the throttle equation at the mixing valve 80, thereby obtaining the current mixed gas flow through the throttle valve 60.

[0119] Therefore, the throttle valve 60 can be adjusted by closed-loop control so that the current mixed gas flow rate flowing through the throttle valve 60 can meet the required mixed gas flow rate of the engine 10. If the current mixed gas flow rate is different from the required mixed gas flow rate of the engine 10, the valve opening of the throttle valve 60 is adjusted to adjust and correct the current mixed gas flow rate.

[0120] In one embodiment, the control method of the EGR system further includes the following steps:

[0121] If the engine 10 switches from the load operation state to the no-load operation state, the EGR system is controlled to exit the stage control mode.

[0122] Specifically, in the no-load operation state, the EGR rate is equal to 0, so whether the engine 10 is in the no-load operation state can be determined according to the EGR rate. The specific method is that if the EGR rate is reduced to 0, the EGR system is controlled to exit the segmented control mode.

[0123] That is, when the EGR rate is equal to 0, the EGR system is not in the segmented control mode. When the EGR rate is greater than 0, the EGR system is in the segmented control mode.

[0124] In a specific embodiment, before determining that the engine 10 enters the load operation state, the control method of the EGR system further includes the following steps:

[0125] Monitor the vehicle and engine 10 operating conditions and parameters;

[0126] The current speed of the vehicle and the engine 10, the current torque, the EGR rate, the opening of the mixing valve 80, the opening of the EGR valve 50 and the opening of the throttle valve 60 are recorded.

[0127] In the description of the present application, the description with reference to the terms "in one embodiment", "in some embodiments", "in a specific embodiment", or "exemplary" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of the present application. In the present application, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine different embodiments or examples described in the present application and the features of different embodiments or examples without contradiction.

[0128] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A control method for an EGR system, the EGR system comprising an engine, an EGR valve and a mixing valve, characterized in that: The control method comprises: Determining that the engine enters a load operation state; Controlling the EGR system to enter a segmented control mode, and obtaining a current speed and a current torque of the engine; comparing the current torque with a set torque corresponding to the current speed; According to the comparison result, one of the EGR valve and the mixing valve is closed-loop controlled, and the other of the EGR valve and the mixing valve is open-loop controlled; If the current torque increases from less than the set torque to equal to or greater than the sum of the set torque and a first adjustment value, the EGR valve is closed-loop controlled and the mixing valve is open-loop controlled, wherein the first adjustment value is greater than or equal to 0; The closed-loop control of the EGR valve comprises: Calculating a current EGR flow rate through the EGR valve according to a throttling equation; The EGR system includes a throttle valve. After the EGR valve is closed-loop controlled and the mixing valve is open-loop controlled, the control method includes: Calculating the current mixed gas flow rate flowing through the throttle valve according to the throttle equation; comparing a current air flow rate passing through the mixing valve with a required air flow rate of the engine, wherein the current air flow rate is a difference between the current mixed gas flow rate and the current EGR flow rate; The throttle valve is controlled in a closed loop according to the comparison result.

2. The control method according to claim 1, characterized in that: The engine operation area includes a fuel economy area and a non-fuel economy area, and the set torque is the torque corresponding to the current speed at the boundary between the fuel economy area and the non-fuel economy area.

3. The control method according to claim 1 or 2, characterized in that: The control method comprises: If the current torque decreases from greater than the set torque to equal to or less than the difference between the set torque and a second adjustment value, the EGR valve is open-loop controlled and the mixing valve is closed-loop controlled, wherein the second adjustment value is greater than or equal to 0.

4. The control method according to claim 3, characterized in that: The first adjustment value is 10 N·m; and / or the second adjustment value is 10 N·m.

5. The control method according to claim 3, characterized in that: The closed-loop control of the EGR valve comprises: comparing the current EGR flow rate with a set EGR flow rate, wherein the set EGR flow rate is an EGR flow rate determined according to the current speed and the current torque; According to the comparison result, the valve opening of the EGR valve is adjusted to make the current EGR flow rate equal to the set EGR flow rate.

6. The control method according to claim 3, characterized in that: The open-loop control of the mixing valve comprises: The valve opening of the mixing valve is controlled to be maintained at a set angle according to the current rotation speed and the current torque.

7. The control method according to claim 3, characterized in that: The open-loop control of the EGR valve comprises: The valve opening of the EGR valve is controlled to be maintained at a set angle according to the current speed and the current torque.

8. The control method according to claim 7, characterized in that: The closed-loop control of the mixing valve comprises: Calculating a current air flow rate through the mixing valve according to a throttling equation; comparing the current air flow rate with a required air flow rate of the engine; According to the comparison result, the valve opening of the mixing valve is adjusted to make the current air flow equal to the required air flow.

9. The control method according to claim 8, wherein the EGR system comprises a throttle valve, characterized in that: After the EGR valve is open-loop controlled and the mixing valve is closed-loop controlled, the control method includes: Comparing the current mixed gas flow rate flowing through the throttle valve with the required mixed gas flow rate of the engine, wherein the current mixed gas flow rate is the sum of a set EGR flow rate and the current air flow rate, and the set EGR flow rate is an EGR flow rate determined according to the current speed and the current torque; The throttle valve is controlled in a closed loop according to the comparison result.

10. The control method according to claim 1 or 2, characterized in that: The control method comprises: If the engine is switched from the load operation state to the no-load operation state, the EGR system is controlled to exit the segmented control mode.

11. An EGR system, characterized in that: The EGR system is used to implement the control method according to claim 1, and the EGR system includes: engine; An EGR valve, the EGR valve being used to control a current EGR flow rate entering the engine; a mixing valve, the mixing valve being used to control the current air flow entering the engine; A memory, wherein the memory is used to store computer executable instructions; An executor, wherein the executor is used to execute the computer executable instructions to implement the steps of the control method according to claim 1.

12. The EGR system according to claim 11, characterized in that: The EGR system is a low-pressure EGR system.

13. A car, characterized in that: Includes the EGR system as described in claim 11 or 12.

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