WO2020108564A1 - Engine having low-pressure egr system, and vehicle - Google Patents

Abstract

An engine (7) having a low-pressure EGR system, and a vehicle, the engine (7) comprising: a target EGR rate control module and a temperature control module; the target EGR rate control module is applicable to determining and adjusting the opening of an EGR valve (11) according to the mode which a vehicle is about to enter, and the temperature control module is applicable to determining and adjusting the temperature of a cooling liquid of the engine (7) according to the working conditions of the vehicle.

Description

Engine and vehicle with low-pressure EGR system

Cross-reference of related applications

This application requires the priority of the Chinese patent application number "201811459384.8" filed by Great Wall Motor Co., Ltd. on November 30, 2018 with the application name "Engines and Vehicles with Low Pressure EGR System".

Technical field

The present application relates to the technical field of vehicles, and in particular to an engine and a vehicle having a low-pressure EGR system.

Background technique

In the related art, the engine EGR system is external EGR, which leads the exhaust gas after the three-way catalyst to the intake supercharger, and needs to pass through the supercharger, the intake intercooler and the throttle valve to enter the engine cylinder .

Due to the immature technology of the existing engine EGR system, there are the following problems:

(1) Inaccurate calculation of EGR rate leads to inaccurate control of the amount of fresh air entering the cylinder, which will cause problems such as engine emissions and difficulty in suppressing knock;

(2) Due to the low-pressure EGR system, the pipeline that needs to flow from the exhaust gas from the exhaust system to the cylinder is long, and there is a delay, which will cause a delay in the acceleration of the vehicle;

(3) Due to the mixed exhaust gas in the intake air, condensate will be precipitated in the intake intercooler. The condensate needs to be discharged and cannot flow into the cylinder in the form of liquid, otherwise it will affect the reliability of the valve seat ring and other parts;

(4) After adopting high compression ratio and low-pressure EGR strategy, the engine is more sensitive to coolant temperature;

(5). The engine area has different requirements for EGR rate under different operating conditions.

Summary of the invention

This application aims to solve at least one of the technical problems in the prior art. To this end, an object of the present application is to propose an engine with a low-pressure EGR system.

Another object of the present application is to propose a vehicle employing the above engine.

An engine with a low-pressure EGR system according to an embodiment of the present application includes: a target EGR rate control module and a temperature control module, the target EGR rate control module is adapted to determine and adjust the EGR valve opening degree according to the mode the vehicle is about to enter, the temperature The control module is adapted to determine and adjust the temperature of the engine coolant according to the operating conditions of the vehicle.

Therefore, through the target EGR rate control module, the EGR rate can be accurately adjusted, so that the fuel consumption and power of the engine are more balanced. While taking into account the acceleration performance of the vehicle, the fuel consumption of the engine is effectively reduced. The control module enables the vehicle to work under the corresponding coolant temperature under different working conditions, so that the fuel in the engine is burned more fully, and the fuel economy of the engine is improved.

The vehicle according to the embodiment of the present application includes the engine having the low-pressure EGR system described in the above embodiment.

Additional aspects and advantages of the present application will be partially given in the following description, and some will become apparent from the following description, or be learned through practice of the present application.

BRIEF DESCRIPTION

The above and/or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

1 is a schematic diagram of a low-pressure EGR system according to an embodiment of the present application;

2 is a schematic diagram of a condensed water discharge method in an intake intercooler according to an embodiment of the present application;

FIG. 3 is an optimal water temperature distribution diagram according to an embodiment of the present application;

4 is a first EGR rate map of an embodiment of this application;

5 is a second EGR rate map of an embodiment of this application;

6 is an ERG valve opening control strategy in a rapid acceleration mode according to an embodiment of the present application;

7 is an EGR rate control strategy in a rapid acceleration mode according to an embodiment of the present application;

8 is a schematic diagram of a management strategy according to an embodiment of the present application;

9 is a schematic diagram of an area selection strategy in an acceleration mode according to a management strategy according to an embodiment of the present application;

10 is a schematic diagram of an area selection strategy in the deceleration mode according to the management strategy in the embodiment of the present application;

11 is a schematic diagram of an engine target EGR rate control module and temperature control module in parallel according to an embodiment of the present application; and

12 is a schematic diagram of a method for calculating the amount of fresh air of an engine according to an embodiment of the present application.

detailed description

The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the drawings, in which the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application, and cannot be construed as limiting the present application.

The engine 7 having a low-pressure EGR system according to an embodiment of the present application will be described below with reference to FIGS. 1-12.

As shown in FIGS. 1-12, the engine 7 with a low-pressure EGR system according to an embodiment of the first aspect of the present application includes: a target EGR rate control module and a temperature control module, the target EGR rate control module is adapted to The opening degree of the EGR valve 11 is determined and adjusted, and the temperature control module is adapted to determine and adjust the temperature of the engine 7 coolant according to the operating conditions of the vehicle.

According to the engine 7 of the embodiment of the present application, through the target EGR rate control module, the EGR rate can be accurately adjusted, so that the fuel consumption and power of the engine 7 are more balanced, while taking into account the acceleration performance of the vehicle, effectively The fuel consumption of the engine 7 is reduced, and the temperature control module enables the vehicle to work at the corresponding coolant temperature under different working conditions, so that the fuel in the engine 7 is burned more fully, and the fuel economy of the engine 7 is improved.

As shown in FIG. 6, according to some embodiments of the present application, the control strategy of the target EGR rate control module includes: predicting that the vehicle is about to enter a sharp acceleration mode, a slow acceleration mode, or a hill climbing mode according to the torque demand and changes of the vehicle; When entering the rapid acceleration mode, the EGR valve 11 has an initial opening degree; when the vehicle is about to enter the slow acceleration mode, the EGR valve 11 opening degree is determined according to the engine 7 speed, the engine 7 torque, and the first EGR rate map; In the mode, the opening degree of the EGR valve 11 is determined based on the engine 7 rotation speed, the engine 7 torque, and the second EGR rate map.

In this way, the engine 7 can be operated at a reasonable EGR rate under a variety of different working conditions, so that the fuel combustion in the engine 7 is more complete and sufficient, and the utilization rate of EGR (exhaust gas) is further improved to improve the engine. 7. Fuel economy.

Next, the control strategy of the target EGR rate control module will be described in detail.

Among them, the control strategy of the target EGR rate control module includes: predicting that the vehicle is about to enter the rapid acceleration mode, slow acceleration mode, or climbing mode according to the torque demand and changes of the vehicle; when the vehicle is about to enter the rapid acceleration mode, the EGR valve 11 has an initial opening When the vehicle is about to enter the slow acceleration mode, the EGR valve 11 opening degree is determined according to the first EGR rate map; when the vehicle is about to enter the hill climbing mode, the EGR valve 11 opening degree is determined according to the second EGR rate map.

During the driving process, based on the changes in driving road conditions and changes in traffic flow, the driver needs to perform rapid overtaking, deceleration, slow acceleration, climbing, and downhill actions in a timely manner, so that the vehicle is in different driving modes, and in In different driving modes, the required torque of the vehicle and the corresponding torque change value are different, and the fuel consumption of the engine 7 is different. Different fuel consumption corresponds to different intake air quantities, and then different EGRs are called according to different driving modes of the vehicle. A rate map and a reasonable determination of the opening degree of the EGR valve 11 can make the intake air amount of the engine 7 more reasonable.

For example, when the vehicle is about to enter the rapid acceleration mode, the EGR valve 11 needs to be completely closed to ensure the amount of fresh air required by the vehicle, but if the EGR valve 11 is directly closed, after the vehicle enters the rapid acceleration mode, part of the exhaust gas needs to be entered at this time To avoid knocking. Therefore, if the EGR valve 11 is completely closed, the response of the EGR valve 11 will be delayed after entering the rapid acceleration mode. This application makes the EGR valve 11 have an initial opening when the vehicle is about to enter the rapid acceleration mode; when the vehicle is slowly accelerating and the vehicle is in the climbing mode, according to the optimal opening of the EGR valve 11 in the corresponding driving mode, The opening degree of the EGR valve 11 is adjusted.

It should be noted that the initial opening degree is the initial opening degree of the EGR valve 11 when the vehicle is about to enter the rapid acceleration mode. The above-mentioned initial opening degree of the EGR valve 5 refers to: an opening degree close to closing the EGR valve 5, the opening degree The value range of the EGR rate is 5%-15%.

As shown in Figures 6 and 7, according to the torque demand and changes, it is predicted that the vehicle will soon enter the rapid acceleration mode, the slow acceleration mode or the climbing mode.

According to the degree to which the driver depresses the accelerator pedal and the speed of the vehicle, the driving modes can be divided into three modes: a rapid acceleration mode, a slow acceleration mode, and a climbing mode, which are representative of the opening degree of the EGR valve 11. Under the three driving modes, different control strategies need to be adopted.

Among them, rapid acceleration mode gives priority to power (that is, acceleration performance), slow acceleration mode and hill climbing mode give priority to fuel economy, and then different EGR control needs to be performed according to different priority levels, so that the driver can be better satisfied Based on the operation requirements, both fuel consumption and power performance are considered.

It should be noted that the rapid acceleration mode is a driving mode in which the driver has a higher demand for power when overtaking; the slow acceleration mode is a driving mode in which the driver is driving normally and needs slight acceleration and deceleration to slowly increase the speed of the vehicle ; Climbing mode is a driving mode when the vehicle needs to go uphill on a long distance.

It can be understood that, when the vehicle is in the hill climbing mode, the engine 7 runs at low speed and near-external characteristics for a long time. The determination of the climbing mode requires that the engine is below 3000r/mim, the torque output is more than 80%, and the duration is more than 10 seconds to enter; the torque below 3000r/mim and more than 80% is the calibrated value, which can be according to the needs of different vehicles Can be changed.

In summary, according to different driving modes of the vehicle, different maps of EGR rate are called, reasonable control and selection of different opening degrees of the EGR valve 11 are made, so that the EGR rate and intake air of the vehicle in multiple driving modes can meet the driving Requirements, find a balance between fuel consumption and power. In this way, the engine 7 can fully burn the fuel under different driving modes of the vehicle, so that the vehicle has more power and better acceleration performance, and by controlling the opening degree of the EGR valve 11, the EGR rate is controlled, so that In the unused driving mode, the current EGR rate is closer to the target EGR rate, while taking into account the acceleration performance of the vehicle, and effectively reducing the fuel consumption of the engine.

The EGR rate refers to the ratio of recirculated exhaust gas to the total intake air drawn into the cylinder (combustion chamber) of the engine 7 and is an important indicator of fuel economy. It is too large or too small when the vehicle is idling or the engine 7 is stopped. , Have a negative impact on the engine 7. The driving mode is not limited to the above-mentioned rapid acceleration mode, slow acceleration mode, and hill climbing mode. In other embodiments, the corresponding EGR rate map may be calibrated according to other driving modes, so that the vehicle in the corresponding driving mode can also be reasonable The opening degree of the EGR valve 11 is adjusted.

In the specific embodiment shown in FIG. 7, when the vehicle is about to enter the rapid acceleration mode, after controlling the EGR valve 11 to maintain the initial opening degree and ensuring the initial intake air amount, the EGR valve 11 is controlled to slowly open.

It can be understood that the initial intake air amount refers to: when the engine 7 is about to enter the rapid acceleration mode, the EGR valve 11 is controlled to have an initial opening degree, and thus the initial intake air amount of the EGR valve 11 having the initial opening degree. That is, the initial intake air amount is the intake air amount of the exhaust gas when the engine 7 is about to enter the rapid acceleration mode (that is, the exhaust air intake amount).

When the vehicle is about to enter the rapid acceleration mode, it means that the power of the vehicle needs to be guaranteed. For a common equivalent-burning gasoline engine, the intake air quantity can guarantee the power output of the engine 7, so in the rapid acceleration mode, the engine needs to be guaranteed 7 Air intake.

After the rapid acceleration mode is triggered, a large amount of air is required to enter the cylinder to ensure the full combustion of the fuel in the engine 7 to ensure the power of the vehicle. At this time, if the EGR valve 11 is still maintained in the previous driving mode. A large opening will result in too much recirculated exhaust gas entering the cylinder, and insufficient intake of fresh air with a high oxygen content, which will result in a significant decrease in the power of the vehicle.

Furthermore, when the vehicle is about to enter the rapid acceleration mode, the EGR valve 11 is controlled to quickly adjust to the initial opening degree, and the opening degree of the EGR valve 11 is slowly changed according to the increase of the vehicle speed.

Therefore, first adjust the EGR valve 11 to the initial opening degree, so that fresh air and a very small amount of exhaust gas can quickly enter the cylinder. After the acceleration of the vehicle is stabilized, the EGR valve 11 is slowly opened to gradually increase the EGR The rate can not only effectively reduce the knock of the engine 7 and reduce the fuel consumption, but more importantly, it can reduce the hysteresis of the EGR valve 11 to make the adjustment and response of the EGR valve 11 more sensitive.

The above-mentioned initial opening degree of the EGR valve 11 refers to an opening degree close to closing the EGR valve 11. In this way, when the vehicle is switched to the slow acceleration mode, the EGR valve 11 can be quickly switched to the opening degree of the EGR valve 11 required by the engine 7 in the slow acceleration mode, so that the reaction of the EGR valve 11 is more sensitive and the amount of hysteresis is smaller.

In the specific embodiment shown in FIG. 7, in some embodiments, when the vehicle enters the rapid acceleration mode, the vehicle has a rapid acceleration mode control strategy, which includes: controlling the EGR valve 11 to maintain the initial opening degree ; Detect the amount of fresh air and determine the difference between the required intake air amount and the amount of fresh air; according to the difference between the required intake air amount and the amount of fresh air, the EGR valve 11 obtains the opening of the EGR valve 11; the initial opening and the EGR valve The amount of change in opening 11 is added to obtain the actual opening of EGR valve 11.

The specific execution process of the rapid acceleration mode is to first calibrate an initial opening degree of an EGR valve 11 close to closing; then according to the difference between the amount of air required by the engine 7 (ie, the required intake air amount) and the amount of fresh air, refer to the EGR valve 11 The opening degree change rate curve obtains the opening degree change amount of the EGR valve 11, the initial opening degree is added to the opening degree change amount to obtain the actual opening degree of the EGR valve 11, and is compared with the maximum opening degree. When the sum of the changes (ie, the actual opening degree of the EGR valve 11) is less than the maximum opening degree, adjust the EGR valve 11 to the opening degree (ie, the actual opening degree of the EGR valve 11), and when the opening degree is greater than or equal to the maximum opening degree, adjust the EGR Valve 11 to maximum opening. Therefore, during the operation of the engine 7, the amount of fresh air of the engine 7 is substantially close to the required intake air amount, which not only can effectively meet the power, but also gradually increase the opening degree of the EGR valve 11 to the maximum opening degree, thereby In the rapid acceleration mode, properly adjust the EGR rate to effectively reduce the knocking trend and improve fuel consumption.

It should be noted that the EGR valve opening rate change curve in this application is obtained by the applicant after many tests and through a large number of test data, which can be based on the required intake air amount, the actual intake air amount and the EGR valve opening degree The rate-of-change curve determines the amount of change in EGR valve opening. Of course, other methods and methods can also be used to obtain the amount of change in EGR valve opening corresponding to the required intake air volume and actual intake air volume. Be limited.

It can be understood that the above-mentioned determination process of the maximum opening degree is: detecting the engine 7 rotation speed and the engine 7 torque; determining the maximum opening degree of the EGR valve 11 according to the engine 7 rotation speed, the engine 7 torque and the EGR rate maximum opening map; the EGR valve 11 The actual opening degree is not greater than the maximum opening degree of the EGR valve 11 (that is, the rapid acceleration mode control strategy). In other words, the maximum value of the actual opening degree of the EGR valve 11 is the above-mentioned maximum opening degree of the EGR valve 11.

It should be noted that the abscissa of the opening rate change rate curve of the EGR valve 11 is the difference between the fresh air amount and the required intake air amount, and the ordinate is the change value of the initial opening degree, which can be obtained by collecting data according to specific tests.

As shown in FIG. 4, when the vehicle enters the slow acceleration mode, the opening degree of the EGR valve 11 is determined based on the engine 7 rotation speed, the engine 7 torque, and the first EGR rate map.

By verifying different EGR rates for different engine 7 operating conditions, the optimal EGR rate is set to multiple regions to form a first EGR rate map, the EGR rates in multiple different regions are different, in non-snap acceleration mode , The appropriate EGR rate in the first EGR rate map is determined according to the engine 7 rotation speed. Therefore, an appropriate EGR rate can be selected in the first EGR rate map according to the engine 7 rotation speed, so that the EGR rates in the slow acceleration mode are more reasonable, thereby further reducing fuel consumption.

In the specific embodiments shown in FIGS. 4 and 5, the first EGR rate map includes: a first region, a second region, and a third region, the EGR rate of the first region, the EGR rate of the second region, and the third The EGR rate of the regions gradually increases. The EGR rate of the first region is 0-5%, the EGR rate of the second region is 5%-15%, and the EGR rate of the third region is 15%-25%.

The applicant of this application made multiple measurements in non-rapid acceleration mode to fix the speed of the engine 7 and gradually increase the torque of the engine 7 to calibrate the first EGR rate map and divide it into the first Zone, second zone and third zone to make the EGR rate selection of the vehicle in slow mode easier and more accurate.

In the specific embodiment shown in FIG. 5, when the vehicle enters the hill climbing mode, the opening degree of the EGR valve 11 is determined according to the engine 7 rotation speed, the engine 7 torque, and the second EGR rate map.

That is, in the hill climbing mode, the low-pressure EGR system also has a second EGR rate map, and the vehicle selects an appropriate EGR rate according to the second EGR rate map. As a result, the vehicle has better acceleration performance and more power in the climbing mode.

The second EGR rate map includes: a fourth area, and the EGR rate of the fourth area is 5%-15%. That is to say, when the vehicle enters the hill climbing mode, the EGR rate of the engine 7 can be adjusted according to the previously calibrated fourth zone, and as can be seen from FIG. 5, in the hill climbing mode, the EGR rate of the fourth zone The range of the EGR rate in the first region is consistent, but it corresponds to a greater torque, which allows the engine 7 to provide greater torque for climbing.

It should be noted that the fourth area is not marked on the first EGR rate map. Since the control accuracy of the traditional low-pressure EGR system is 3%, during the control process, a sudden increase or a sudden decrease in the EGR rate may occur. Too high EGR rate leads to insufficient power, misfire, and too low to knock, and the control strategy of this embodiment only calls the second EGR rate map in the climbing mode.

In this way, it is not only possible to prevent the EGR rate of the low-pressure EGR system of the engine 7 in the climbing mode, the EGR rate is always located in the fourth area in the second EGR rate map, so as to avoid The above-mentioned problems of insufficient power, misfire and knocking (that is, after confirming that the vehicle enters the climbing mode, call the second EGR rate map and adjust the EGR rate according to the EGR rate map) can effectively reduce fuel consumption and reduce Shock to increase ride comfort.

As shown in FIG. 12, the calculation method of the fresh air amount includes: calculating the basic EGR rate e1 according to the formula e1=(m2-m1)/m2, where m1 is the air flow at the total intake pipe and m2 is the intake air cooling The flow rate at the outlet of the generator; according to the formula m4=pVM/(RT), calculate the total intake air m4 of the engine, where p is the intake air pressure at the front end of the intake manifold, V is the displacement of the engine 7, and R is a constant, T is the absolute temperature of the intake air, M is the average molar mass; according to the formula m3=m4*e1, calculate the EGR flow m3; according to the formula mx1=m4*(1-e1), calculate the first fresh air amount mx1; according to the formula mx2 = Mx1*a1*a2, calculate the actual fresh air volume mx2 of the engine 7 cylinder, where a1 is the first air volume correction coefficient and a2 is the second air volume correction coefficient; the pressure difference ΔP and the opening of the EGR valve 11 are input to the valve port flow rate The model map obtains m5. According to the formula d=(m5-m3)/m3, the deviation rate d of the EGR rate is calculated, where m5 is the flow rate at the EGR valve 11, and the deviation rate d is input into the correction factor map1 to obtain the first air volume correction factor a1; the actual Lambda of the cylinder of the engine 7 is measured based on the oxygen content detected by the oxygen sensor 8, and (Lambda-1) is input to the correction coefficient map2 to obtain the second air volume correction coefficient a2.

That is to say, the calculation process of the actual EGR rate is: the first air flow meter 1 measures the fresh air flow m1 (that is, the air flow at the total intake pipe), and the second air flow meter 4 measures the EGR plus fresh air flow The total air volume m2 (that is, the flow rate at the outlet end of the intake intercooler 3); according to the intake pressure p at the front end of the intake manifold measured by the intake pressure sensor 6, according to the absolute temperature T of the intake air and the intake pressure p The total intake air volume m4 of the engine 7 is calculated by the intake air calculation module, and m4 is calculated according to the ideal gas state equation (the ideal gas state equation is P*V=MRT, where P is the intake pressure and V is the engine 7 displacement , R is a constant 8.314, T is the absolute temperature, M is the average molar mass, multiplied by the number of moles can be converted to mass), that is, m4 = pVM / (RT), then calculate the EGR flow m3, m3 = m4 * e1.

Furthermore, calculate the first fresh air volume mx1; according to the formula mx2=mx1*a1*a2, calculate the actual fresh air volume mx2 of the engine 7 cylinder, where a1 is the first air volume correction coefficient and a2 is the second air volume correction coefficient; The difference ΔP and the opening of the EGR valve are input into the valve port flow model map to obtain m5, and the deviation rate d of the EGR rate is calculated according to the formula d=(m5-m3)/m3, where m5 is the flow rate at the EGR valve 11, and the deviation rate d Input the correction coefficient map1 to obtain the first air volume correction coefficient a1; measure the actual Lambda of the engine 7 cylinder according to the oxygen content detected by the oxygen sensor 6, and input (Lambda-1) to the correction coefficient map2 to obtain the second air volume correction coefficient a2 .

The first fresh air volume mx1 is a calculated value of the intake air volume of the engine 7. Since it is close to the intake manifold, it defaults to the real air volume. From this, an accurate amount of fresh air is calculated, and an equivalent ratio fuel injection (air to fuel mass ratio of 14.7) is performed according to the amount of fresh air, so that the fuel entering the cylinder can be fully burned.

Because the EGR transportation pipeline is long and has a delay effect, the EGR rate actually entered into the cylinder during the transient operation of the vehicle is somewhat different from the target EGR rate, so it is necessary to accurately calculate the current EGR rate and the current entry The fresh air in the cylinder (that is, the amount of fresh air mentioned above), so that the fuel injector injects fuel in proportion to the fresh air, and adjusts the ignition angle according to the actual EGR rate entering the cylinder.

Among them, accurately calculate the amount of fresh air of the engine 7, and constantly adjust the coolant temperature, so that the coolant temperature of the engine 7 continues to approach the optimal coolant temperature, and then determine the driving mode of the vehicle according to the torque demand, call Different EGR rate map, and reasonable choice of different EGR valve 11 opening.

For example, when the vehicle is in the rapid acceleration mode, the vehicle needs a large initial intake air volume, but if the EGR valve 11 is directly closed, it will cause the EGR valve 11 to respond lagging, and then the application puts the vehicle in the rapid acceleration mode, the EGR valve 11 can keep the product small opening; when the vehicle is slowly accelerating and the vehicle is in the climbing mode, the opening of the EGR valve 11 is adjusted according to the optimal opening of the EGR valve 11 in the corresponding driving mode.

In summary, according to the engine 7 with a low-pressure EGR system of this embodiment, multiple data such as the coolant temperature and EGR rate of the engine 7 can be adjusted to accurately control the combustion of oil and gas in the engine 7 and improve the combustion stability of the engine 7 , To provide a reasonable EGR rate to match the operating conditions of the corresponding engine 7. In this way, smoothness, acceleration performance and fuel consumption can be taken into account, and the fuel consumption can be effectively reduced on the premise of making the vehicle more powerful and smoother.

It can be understood that, according to the driving needs of the driver, it is determined to use different EGR rate maps, so as to avoid a large gap between the EGR rate called by the engine 7 and the target EGR rate, in order to ensure the driver's demand for power, try to use more A large EGR rate reduces the fuel consumption of the engine 7.

Therefore, the operating condition of the engine 7 is determined according to the running state of the vehicle, and the opening degree of the EGR valve 11 is determined according to the target EGR rate and the operating condition of the engine 7, so that the EGR rate of the EGR actually entering the cylinder is instantaneous During normal operation, it is closer to the target EGR rate (that is, the required EGR rate), so that the EGR rate control accuracy is higher.

Among them, if the EGR rate is reduced to a certain degree compared with the target EGR rate, the ignition angle needs to be pushed back. If the EGR rate actually entering the cylinder is higher than the target EGR rate, the ignition angle needs to be slightly advanced to ensure the combustion efficiency.

It should be noted that, in order to ensure that the different loads of the engine 7 can achieve the corresponding power and fuel consumption targets, it is necessary to control the EGR rate actually entered into the cylinder under different loads to be equal to the target EGR rate. The three-way catalyst 9 is used in the post-processing of the engine 7. In order to ensure the efficiency of the three-way catalyst 9, the air-fuel ratio of the engine 7 must be 14.7, that is, the Lambda is 1. Therefore, it is necessary to accurately control the EGR rate actually entering the cylinder.

The EGR rate refers to the ratio of the recirculated exhaust gas to the total intake air drawn into the cylinder (combustion chamber) of the engine 7 and is an important indicator of fuel economy. Too large or too small when the vehicle is at idle or the engine 7 is stopped Time, all have a negative impact on the engine 7. The driving mode is not limited to the above-mentioned rapid acceleration mode, slow acceleration mode, and hill climbing mode. In other embodiments, the corresponding EGR rate map may be calibrated according to other driving modes, so that the vehicle in the corresponding driving mode can also be reasonable The opening degree of the EGR valve 11 is adjusted.

As shown in FIGS. 8-10, the control strategy of the temperature control module includes: detecting the speed and torque of the engine 7; determining the current operating condition of the engine 7 according to the speed and torque of the engine 7; determining the correspondence according to the current operating condition of the engine 7 The engine 7 coolant temperature area corresponds to each engine 7 coolant temperature area. In this way, the vehicle can be operated at the corresponding coolant temperature under different operating conditions, so that the fuel in the engine 7 is burned more fully, and the fuel economy of the engine is improved.

Furthermore, for different operating conditions of the engine 7, multiple optimal EGR rate regions are correspondingly provided, and according to different operating conditions, a reasonable EGR amount is provided toward the cylinder of the engine 7. In this way, when the engine 7 is under medium and high load, knocking can be effectively suppressed and the ride comfort of the vehicle can be improved. When the engine 7 is under a small load, the intake air quantity of the engine 7 can be maintained to ensure combustion stability, thereby improving the vehicle The dynamics of the vehicle, thus effectively balancing the dynamics and smoothness of the vehicle.

The temperature control module can verify the different coolant temperatures for different engine 7 loads, set the optimal coolant to multiple areas, and a boundary line is formed between the two adjacent areas; it is determined according to the engine 7 speed Corresponding to the boundary torque on the boundary line, the actual torque of the engine 7 and the boundary torque are compared, and the coolant temperature is controlled in an appropriate region.

Detect the speed and torque of the engine 7; determine the current operating condition of the engine 7 according to the speed and torque of the engine 7; determine the corresponding coolant temperature area of the engine 7 according to the current operating condition of the engine 7, the current operating condition of the engine 7 Including medium and low speed, medium and small load conditions, medium speed, medium load conditions and medium and high speed, medium and high load conditions, each condition corresponds to its own engine 7 coolant temperature area.

Here, it should be noted that the speed and torque of the engine 7 correspond to each other, and the vehicle can have different torques at the same speed under different operating conditions. Similarly, as the speed of the engine 7 increases, the torque can change. In the region formed by the correspondence between the torque and the speed of the engine 7, different regions corresponding to different optimal coolant temperatures are artificially set to improve the stability and reliability of the low-pressure EGR system to further optimize the use effect of the engine 7 , To reduce emissions, the optimal coolant temperature is through continuous experiments, the engine 7 at the same speed and torque by adjusting the coolant temperature to test the engine 7 emissions and various performance indicators, and according to different coolant temperatures Optimum coolant temperature derived from engine 7 emissions and various performance indicators.

A boundary line is formed between two adjacent optimal coolant temperature regions. When any one of the speed or torque of the engine 7 exceeds the range of this region, the optimal coolant temperature of the engine 7 is also If a change occurs, the coolant temperature can be adjusted by controlling the coolant flow valve to keep the coolant temperature close to the optimal coolant temperature, so that the low-pressure EGR system of the vehicle maintains a good state.

The control center of the vehicle can receive the engine 7 speed of the vehicle and the torque information output by the engine 7, according to the actual speed falling into the corresponding position on the boundary line, get the value of the boundary torque corresponding to the actual speed on the boundary line, by comparing The size of the actual torque and the boundary torque to determine the optimal coolant temperature corresponding to the engine 7 at this time, the control center adjusts the coolant temperature by controlling the radiator 14, coolant flow valve and other devices that can adjust the coolant temperature Temperature, so that the temperature of the coolant gradually approaches the optimal coolant temperature.

According to the engine 7 with a low-pressure EGR system of the present application, by setting the optimal coolant temperature to a plurality of regions, a boundary line is formed between two adjacent regions, and the corresponding engine is determined according to the current operating conditions of the engine 7 7Coolant temperature area, by comparing the actual engine speed with the corresponding boundary torque on the boundary line to determine the optimal coolant temperature at this time, the engine 7 can be at different coolant temperatures under different operating conditions Work to improve the fuel economy of the engine 7.

As shown in FIG. 3, according to an embodiment of the present application, the engine 7 coolant temperature regions corresponding to medium and low speed, medium and small load conditions, medium speed, medium load conditions, and medium and high speed and medium and high load conditions are: A Area, area B, area C, the cooling water temperature in area A, the cooling water temperature in area B, and the cooling water temperature in area C are sequentially lowered.

That is to say, the multiple areas include: A area-medium and low speed, medium and low load area, B area-medium speed and medium load area, C area-medium and high speed, medium and high load area, between A and B area AB boundary line, a BC boundary line is formed between the B area and the C area, and the cooling water temperature in the A area, the cooling water temperature in the B area, and the cooling water temperature in the C area sequentially decrease.

Among them, the temperature of the coolant in the area A is 100℃-110℃, where the optimal coolant temperature in the area A is between 100℃-110℃, the temperature of the coolant in the area B is 85℃-100℃, and the temperature in the area B The optimal temperature of the cooling liquid is between 85°C and 100°C, and the temperature of the cooling liquid in the area C is 70°C-90°C, and the optimal cooling liquid temperature in the area C is between 70°C and 90°C.

When the speed and torque of the engine 7 are both in the A region, the engine 7 is at a medium and small load, and the speed of the engine 7 is at a low to medium speed, as shown in FIGS. 1 and 2, the exhaust gas of the engine 7 passes through the EGR after passing through the catalyst The valve 11 and the EGR cooler 10 are reintroduced into the intake passage of the engine 7. After the exhaust gas passes through the supercharger 2 of the engine 7, it enters the cylinder through the throttle valve 5 and is re-mixed with the air. After fuel is fully combusted with fuel. Low-pressure EGR has a certain negative impact on the combustion of small loads, which may cause combustion instability. When the engine 7 is at medium and small loads and low to medium speeds, the low-pressure EGR system can reduce the pumping loss of the engine 7 by increasing the coolant temperature. To reduce friction and increase the stability of fuel combustion in the engine 7, thereby reducing the risk of misfire and reducing fuel consumption.

When the speed and torque of the engine 7 are both in the B region, the engine 7 is at a medium load and a medium speed, and the coolant of the engine 7 needs a lower temperature, which can suppress knocking to a certain extent to improve the engine The stability of 7, reduces the emissions of the engine 7, and improves the thermal efficiency of the engine 7.

When the speed and torque of the engine 7 are both in the C region, the engine 7 is at medium-high load and medium-high speed. At this time, the engine 7 needs the lowest possible water temperature, which can further reduce knocking and greatly improve the engine 7 power. At the power point, the exhaust temperature of the engine 7 is reduced to increase the maximum power of the engine 7.

As shown in FIGS. 8 and 10, according to an embodiment of the present application, region B is a transition region, there is an AB boundary torque between regions A and B, and BC boundary torque between regions B and C; region B The transition strategy includes: determining the BC boundary torque according to the engine 7 speed; if the engine 7 torque is greater than or equal to the BC boundary torque, switch to the area C, otherwise switch to the area A or B; determine the AB boundary torque according to the engine 7 speed; if the engine 7 The torque is greater than or equal to the AB boundary torque, switch to the B area, otherwise switch to the A area.

Among them, the rotation speed of the engine 7 can be brought into the BC boundary torque curve to obtain the BC boundary torque at the rotation speed. The rotation speed of the engine 7 can be brought into the AB boundary torque curve to obtain the AB boundary torque, and the BC boundary torque curve and the AB boundary torque curve are obtained from multiple experiments.

Further, according to the speed of the speed change, the temperature of the coolant can be adjusted to the area A or the area C in advance. In this way, the transition of the coolant temperature between the A region, the B region, and the C region is smoother, the hysteresis of the coolant temperature adjustment is reduced, and the response speed of the coolant temperature adjustment is increased.

The specific process of coolant temperature adjustment is as follows:

As shown in FIG. 10, query the corresponding AB boundary torque on the AB boundary line and the corresponding BC boundary torque on the BC boundary line according to the actual speed of the engine 7; compare the actual torque of the engine 7 with the AB boundary torque and the BC boundary torque, if the engine 7 If the actual torque is greater than the BC boundary torque, the coolant temperature is controlled in the C region. If the actual torque of the engine 7 is greater than the AB boundary torque and less than the BC boundary torque, the coolant temperature is controlled in the B region. If the actual torque of the engine 7 is less than the AB boundary torque, Then the coolant temperature is controlled in area A.

According to an embodiment of the present application, during the acceleration process of the engine 7, according to the slope of acceleration, the coolant can be selectively advanced to the area C to adjust the coolant temperature in advance, so that the temperature of the coolant is adjusted to the maximum in the area A Under the optimal coolant temperature, the vehicle can further alleviate the knock caused by the influence of the low-pressure EGR system during acceleration, improve the power of the engine 7, and make the vehicle have better acceleration capability.

As shown in FIGS. 8 and 9, according to an embodiment of the present application, the area selection strategy in the acceleration mode includes: calculating the AB boundary torque according to the engine 7 speed and the AB boundary torque curve; calculating the acceleration slope; according to the acceleration slope and AB The boundary torque hysteresis curve determines the acceleration torque transition amount; the AB boundary torque is added to the acceleration torque transition amount; if the torque of the engine 7 is greater than or equal to the sum of the AB boundary torque and the acceleration torque transition amount, the region C is advanced.

It should be noted that the AB boundary torque curve is obtained by the applicant based on multiple tests and through a large number of test data. The AB boundary torque can be calculated according to the engine speed and the AB boundary torque curve. Of course, the engine can also be obtained by other methods or methods. The AB boundary torque corresponding to the rotation speed is not limited in this application for the acquisition method of the AB boundary torque.

The AB boundary torque hysteresis curve is obtained by the applicant based on multiple tests and through a large number of test data. The acceleration torque transition amount can be calculated according to the acceleration slope and the AB boundary torque hysteresis curve. Of course, it can also be obtained by other methods or methods. The acceleration torque transition amount corresponding to the acceleration slope is not limited in this application.

Among them, the slope of acceleration is: (throttle pedal position b-throttle pedal position a)/(time spent from a to b), it should be noted that the acceleration slope is the distance from the accelerator pedal position b to the accelerator pedal position a and the accelerator pedal The ratio of the time taken from position b to position a of the accelerator pedal; as shown in Figure 5, the AB boundary torque on the AB boundary can be obtained by introducing the engine 7 speed into the AB boundary torque curve, and the acceleration slope is input to the AB boundary torque Hysteresis curve to obtain the transition torque. If the actual torque of the engine 7 is greater than the corresponding AB boundary torque on the AB boundary plus the transition torque, the coolant temperature will advance to the optimal coolant temperature corresponding to the C region, and the acceleration slope can be The greater the slope of the driver’s torque demand, the greater the torque required by the vehicle.

According to an embodiment of the present application, in the two-dimensional image formed by the correspondence between the actual speed of the engine 7 and the torque, during the deceleration of the engine 7, the coolant may be selectively advanced to A according to the deceleration slope In order to adjust the coolant temperature in advance, the coolant temperature is adjusted to the optimal coolant temperature in the A zone, reducing friction and increasing the stability of fuel combustion in the engine 7, thereby reducing the risk of misfire and reducing fuel consumption.

As shown in FIG. 8, according to an embodiment of the present application, the area selection strategy in the deceleration mode includes: calculating the BC boundary torque based on the engine 7 speed and the BC boundary torque curve; calculating the deceleration slope: (throttle pedal position b-throttle pedal position a)/a to b time; determine the deceleration torque transition amount according to the deceleration slope and the BC boundary torque hysteresis curve; subtract the BC boundary torque minus the deceleration torque transition amount; if the engine 7 torque is less than or equal to the BC boundary torque and deceleration torque The difference between the transition amounts enters area A in advance.

It should be noted that the BC boundary torque curve is obtained by the applicant based on multiple tests and through a large number of test data. The BC boundary torque can be calculated according to the engine speed and the BC boundary torque curve. Of course, the engine can also be obtained by other methods or methods. The BC boundary torque corresponding to the rotation speed is not limited in this application.

The BC boundary torque hysteresis curve is obtained by the applicant based on multiple tests and through a large number of test data. The deceleration torque transition amount can be calculated according to the deceleration slope and the BC boundary torque hysteresis curve. The deceleration torque transition amount corresponding to the deceleration slope is not limited in this application.

It should be noted that the acceleration slope is: (throttle pedal position b-throttle pedal position a)/a to b time; as shown in Figure 8, the acceleration slope is input to the BC boundary torque hysteresis curve to obtain the transition torque , Bring the speed of the engine 7 into the BC boundary torque curve to get the BC boundary torque. If the actual torque of the engine 7 is less than the corresponding BC boundary torque on the BC boundary minus the transition torque, the coolant enters the area A in advance to adjust in advance The coolant temperature is adjusted to the optimal coolant temperature in the area A to improve the power performance of the engine 7 and reduce friction while increasing the stability and fuel consumption of fuel combustion in the engine 7.

According to an embodiment of the present application, the flow rate of the cooling liquid is adjustable, and the temperature of the cooling liquid is adjusted by controlling the flow rate of the cooling liquid, so that the temperature of the cooling liquid continuously approaches the optimal temperature of the cooling liquid, so that a low-pressure EGR system is provided The engine 7 can maintain a good working condition.

Since the coolant temperature is adjusted by adjusting the flow rate, the coolant temperature adjustment has a certain hysteresis. After analyzing the temperature distribution of the three areas of ABC, the characteristics are confirmed, and the area B is used as a transition area in advance. Pre-adjust the flow rate of the cooling liquid to achieve the following of the cooling liquid temperature and effectively reduce the fuel consumption. After testing and verification, the coolant temperature follows very well, which meets the needs of the engine 7 corresponding to different temperatures under different working conditions.

Among them, the engine 7 also includes a condensed water precipitation module.

As shown in FIGS. 2 and 11, the oxygen sensor 8 is adapted to sense the oxygen content on the exhaust side to determine whether the combustion is complete.

Before the exhaust gas enters the intake intercooler 3, the exhaust gas is introduced into the EGR cooler 10 to precipitate moisture in the exhaust gas. It is understandable that when EGR passes through the intake intercooler 3, liquid water is separated out, the liquid water cannot be directly introduced into the cylinder, otherwise it will increase the friction of the valve seat ring and increase the friction between the piston and the cylinder wall. Affect the life of the engine 7.

The temperature of the gas discharged from the engine 7 is high, part of the exhaust gas is discharged from the vehicle after being catalyzed, and another part of the exhaust gas enters the cylinder of the engine 7 through the throttle valve 5 through the pipeline, and the part of the exhaust gas is discharged from the exhaust system of the engine 7 After entering the air intake intercooler 3, the temperature of the exhaust gas in the air intake intercooler 3 is greatly reduced, and then the moisture in the water exhaust gas can be fully precipitated to ensure that the water cannot directly enter the cylinder of the engine 7 to a certain extent. The lower friction loss between the piston and the cylinder wall helps to increase the service life of the engine 7.

The cooling temperature of the intake intercooler 3 for the gas is not greater than the cooling temperature of the EGR cooler 10 for the exhaust gas. In order to prevent the gas from being analyzed in the intake intercooler 3 to reduce the loss of the engine 7; alternatively, the intake intercooler 3 cools the intake air higher than the EGR cooler 10 cools the exhaust gas 3 ℃-7℃.

After the water in the exhaust gas is analyzed, the precipitated moisture can be selectively introduced into the combustion chamber. Thus, thermal efficiency can be improved.

Specifically, EGR is led out from the back of the three-way catalyst 9, and after cooling by the EGR cooler 10, the temperature is reduced from 500-700 degrees Celsius to 40 degrees Celsius or less, and the water is charged and analyzed, and the precipitated water is stored in the water reservoir 16. The EGR cooler 10 is provided with an electroplated radiator 14 and a fan 15. The radiator 14 and the fan 15 are arranged at the vehicle intake grille. After the EGR is cooled by the EGR cooler 10, the water is charged and analyzed, and then the EGR heat The exchanger 17 (provided with heat from the engine 7 coolant) heats the EGR, increases the saturation of the EGR, makes it sufficiently dry, and then passes through the electric heater 18 and the EGR valve 11 and enters the intake intercooler 3 for cooling.

The cooling temperature of the intake air intercooler 3 for the intake air is 5°C higher than the cooling temperature of the EGR cooler 10 for the EGR, to ensure that no water will be analyzed in the intake air, and the precipitated water is stored in the water storage 16, the water storage The pipeline of 16 is connected to the condensate valve 19, water flows through the condensate valve 19 through the water reservoir 16 and into the cylinder (combustion chamber) through the atomizing mechanism 21, and the above-mentioned circulation pipeline constitutes the engine water passage 20.

In addition, the water path of the engine 7 is such that the effluent of the engine 7 passes through the heat exchanger to slightly heat the EGR, then flows into the radiator 14, and then when the engine 7 is in the cold state, when the temperature of the engine 7 cooling water is lower than 70°C, the electricity The heater 18 heats the cooled EGR. In the rapid acceleration mode, the engine 7 is at a near power point. At this time, in order to suppress the exhaust temperature, the condensate valve 19 is opened, and the water enters the cylinder in a gaseous state through the atomizing mechanism 19 to reduce the temperature in the cylinder.

In other words, the flow rate of the coolant is adjustable. In this way, the flow rate of the coolant is more accurately controlled, so that the engine can be sufficiently heat-exchanged in the normal mode, and the combustion during the cold start can be more adequate.

When the engine 7 introduces EGR into the pipeline in the cylinder, condensation and coking will occur during long-term use, and clogging will occur. The main risk areas for clogging are the EGR cooler 10 and the EGR valve 11, and the EGR flow will be blocked after the clogging. The gap between the actual EGR rate and the required target EGR is large, resulting in insufficient EGR rate, which will lead to an increase in fuel consumption at small loads, mid-to-high load engines 7 deflagration, and there is a risk of scrapping the engines 7.

The working process of the differential pressure sensor 12 is: the gas is taken from the EGR cooler 10, and the pressure difference measured by the differential pressure sensor 12 is the first pressure difference, and the first pressure difference is compared with the corresponding first standard pressure difference. When the pressure of a differential pressure exceeds the first standard differential pressure, the differential pressure sensor 12 is controlled by the check valve 13 to take air in the area behind the EGR cooler 10 and in front of the EGR valve 11, the measured pressure difference is the first The second pressure difference, the second pressure difference is compared with the corresponding second standard pressure difference, the second pressure difference is greater than the second standard pressure difference, it is determined that the EGR valve 11 is blocked; if the second pressure difference is less than the second standard pressure difference, but the first If the pressure difference is still greater than the first standard pressure difference, it is determined that the EGR cooler 10 is clogged.

Furthermore, if it is determined that the EGR cooler 10 is clogged, the output is faulty, and the EGR cooler 10 needs to be replaced or cleaned; if it is determined that the EGR valve 11 is faulty, first perform a self-repair procedure, and if the pressure drop after self-repair is reduced, the use is satisfied If it is over, continue to use it. Otherwise, it will report a fault and prompt you to replace the EGR valve 11 or disassemble and clean the EGR valve 11.

It should be noted that the cumulative working time of the engine 7 is the cumulative working time of the engine 7 during the life cycle, because the EGR valve 11 and the EGR cooler 10 accumulate during the working process, and the side walls of the two will have a natural During the process of condensation, the pressure difference will naturally increase, but it is not clogged, and a decline curve can be drawn. The induced pressure of the pressure difference sensor 12 can gradually change according to the decline curve, thereby correcting the pressure difference to avoid misdiagnosis.

The vehicle according to the embodiment of the present application includes the engine 7 having the low-pressure EGR system as in the above embodiment.

According to the vehicle of the embodiment of the present application, the power performance of the vehicle is good, the reliability of the engine 7 is high, and the service life is long.

In the description of this specification, reference to the descriptions of the terms "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" is meant to be combined with the implementation The specific features, structures, materials, or characteristics described in the examples or examples are included in at least one embodiment or example of the present application. In this specification, the schematic expression 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 any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present application have been shown and described, those of ordinary skill in the art may understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and purpose of the present application, The scope of the application is defined by the claims and their equivalents.

Claims (13)

1. An engine with a low-pressure EGR system is characterized by comprising: a target EGR rate control module and a temperature control module, the target EGR rate control module is adapted to determine and adjust the EGR valve opening degree according to the vehicle's upcoming mode, the The temperature control module is adapted to determine and adjust the temperature of the engine coolant according to the operating conditions of the vehicle.
2. The engine with a low-pressure EGR system according to claim 1, wherein the control strategy of the target EGR rate control module includes:

   Predict whether the vehicle is about to enter the rapid acceleration mode, slow acceleration mode or hill climbing mode according to the torque demand and changes of the vehicle;

   When the vehicle is about to enter the rapid acceleration mode, the EGR valve has an initial opening;

   When the vehicle is about to enter the slow acceleration mode, the EGR valve opening degree is determined according to the engine speed, engine torque and the first EGR rate map;

   When the vehicle is about to enter the hill climbing mode, the EGR valve opening degree is determined according to the engine speed, the engine torque, and the second EGR rate map.
3. The engine with a low-pressure EGR system according to claim 2, wherein when the vehicle enters the rapid acceleration mode, the vehicle has a rapid acceleration mode control strategy, the rapid acceleration mode control strategy includes:

   Controlling the EGR valve to maintain the initial opening;

   Check the fresh air volume and determine the difference between the required intake air volume and the fresh air volume;

   According to the difference between the required intake air volume and the fresh air volume, the EGR valve opening variation is obtained;

   The initial opening degree and the EGR valve opening degree change amount are added to obtain the actual opening degree of the EGR valve.
4. The engine with a low-pressure EGR system according to claim 2, wherein the first EGR rate map includes: a first region, a second region, and a third region, the EGR rate of the first region, the The EGR rate in the second zone and the EGR rate in the third zone increase sequentially.
5. The engine with a low-pressure EGR system according to claim 2, wherein the second EGR rate map includes: a fourth region, and the EGR rate of the fourth region is 5%-15%.
6. The engine with a low-pressure EGR system according to claim 3, wherein the calculation method of the fresh air amount includes:

   According to the formula e1=(m2-m1)/m2, calculate the basic EGR rate e1, where m1 is the air flow at the total intake pipe and m2 is the flow at the outlet end of the intake intercooler;

   According to the formula m4=pVM/(RT), calculate the total engine intake m4, where p is the intake pressure at the front of the intake manifold, V is the engine displacement, R is a constant, and T is the absolute temperature of the intake , M is the average molar mass;

   According to the formula m3=m4*e1, calculate the EGR flow m3;

   According to the formula mx1=m4*(1-e1), calculate the first fresh air amount mx1;

   According to the formula mx2=mx1*a1*a2, calculate the actual fresh air volume mx2 of the engine cylinder, where a1 is the first air volume correction coefficient and a2 is the second air volume correction coefficient;

   According to the formula d=(m5-m3)/m3, calculate the deviation rate d of the EGR rate, where m5 is the flow rate at the EGR valve, and obtain the first air volume correction coefficient a1 according to the deviation rate d of the EGR rate;

   The actual Lambda of the engine cylinder is measured according to the oxygen content detected by the oxygen sensor, and the second air volume correction coefficient a2 is obtained according to the Lambda.
7. The engine with a low-pressure EGR system according to claim 1, wherein the control strategy of the temperature control module includes:

   Detect engine speed and torque;

   Determine the current working condition of the engine according to the engine speed and torque;

   The corresponding engine coolant temperature area is determined according to the current operating condition of the engine, and each operating condition corresponds to a respective engine coolant temperature area.
8. The engine with a low-pressure EGR system according to claim 7, wherein the engine coolant temperature region is: region A, region B, region C, the cooling water temperature in the region A, and the cooling water temperature in the region B The temperature of the cooling water in the area C decreases sequentially.
9. The engine with a low-pressure EGR system according to claim 8, wherein the region B is a transition region, there is an AB boundary torque between the region A and the region B, the region B and the region C BC boundary torque between regions;

   The transition strategy of the area B includes:

   Determine the BC boundary torque according to the engine speed;

   If the engine torque is greater than or equal to the BC boundary torque, switch to area C, otherwise switch to area A or B;

   Determine AB boundary torque according to engine speed;

   If the engine torque is greater than or equal to the AB boundary torque, switch to the B zone, otherwise switch to the A zone.
10. The engine with a low-pressure EGR system according to claim 9, characterized in that the coolant temperature can be selectively adjusted to the area A or the area C in advance according to the speed of the speed change.
11. The engine with a low-pressure EGR system according to claim 10, wherein the calculation formula of the speed change speed is: (throttle pedal position b-throttle pedal position a)/(time from a to b).
12. The engine with a low-pressure EGR system according to claim 7, wherein the flow rate of the coolant is adjustable.
13. A vehicle characterized by comprising the engine with a low-pressure EGR system according to any one of claims 1-12.

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