Low-pressure EGR cooling system and control method thereof

Abstract

This invention discloses a low-pressure EGR cooling system and its control method, relating to the field of low-pressure EGR technology. The low-pressure EGR cooling system includes an engine and a low-pressure EGR system connected to the engine's intake and exhaust ends to introduce a portion of the exhaust gas from the exhaust end into the intake end to form a gas mixture. The low-pressure EGR cooling system also includes an engine cooling system and a water-cooled intercooler system. The engine cooling system includes a first water-cooled circulation pipe connected to the engine and the low-pressure EGR system to absorb heat and cool a portion of the exhaust gas recovered by the engine and the low-pressure EGR system. The technical solution provided by this invention combines the traditionally separate engine cooling structure with the water-cooled intercooler structure, enabling the two cooling structures to form a conductive or isolated relationship based on the temperature difference in the two circulation cooling pipes, reducing the risk of gas mixture condensation.

Description

Technical Field

[0001] This invention relates to the field of low-pressure EGR technology, and particularly to a low-pressure EGR cooling system and its control method. Background Technology

[0002] EGR (Exhaust Gas Recirculation) technology was first applied to diesel engines in the 1960s. When the EGR system is working, it returns a portion of the exhaust gas to the combustion chamber through the intake system, thereby reducing the maximum combustion temperature and reducing the formation of nitrogen oxides.

[0003] Structurally, EGR systems are mainly divided into two types: high-pressure EGR and low-pressure EGR. High-pressure EGR generally refers to drawing exhaust gas before the turbine, which then passes through the turbocharger's compressor before entering the intake manifold and finally into the engine cylinders. Low-pressure EGR generally refers to drawing exhaust gas after the turbine, which, along with fresh air, passes through the turbocharger's compressor before entering the intake manifold and finally into the engine cylinders. Thanks to the use of a mixing valve (throttle valve), low-pressure EGR eliminates the negative pressure differential region under low-speed, high-load conditions, ensuring that a large amount of EGR exhaust gas can flow smoothly into the cylinders to exert its effect. Therefore, compared to high-pressure EGR, low-pressure EGR can achieve a higher EGR rate and a wider operating range. Low-pressure EGR has become standard equipment in the newly developed high-efficiency turbocharged gasoline engines of major OEMs.

[0004] However, low-pressure EGR systems have a unique characteristic compared to high-pressure EGR systems: after the EGR exhaust gas mixes with fresh air, it passes through the turbocharger compressor, then the water-cooled intercooler, and finally enters the cylinder through the intake manifold. Inside the water-cooled intercooler, when the wall temperature is low, a large amount of water vapor in the EGR exhaust gas condenses below its dew point. This condensate accumulates in the intercooler or intake manifold. When the accelerator pedal suddenly changes, causing a change in intake pressure, the accumulated liquid water can enter the combustion chamber, leading to misfire and, in severe cases, damage to the piston and connecting rod. This is especially prone to occur in foggy or rainy weather when the air is saturated with water. Common measures include reducing the EGR rate and increasing the intake manifold temperature to reduce the probability of misfire. However, reducing the EGR rate affects engine fuel consumption and nitrogen oxide emissions, while increasing the intake manifold temperature increases the tendency for engine knocking. Another technical solution involves adding a baffle in the intake manifold after the intercooler to block the condensate. However, this solution also affects the intake efficiency of the intake manifold, and excessive condensate can enter the engine combustion chamber and cause misfires, so it cannot completely solve the problem.

[0005] Furthermore, since the intake intercooler currently uses an independent cooling water circulation system, the intake intercooler and coolant can only be heated by the air-fuel mixture entering the intake intercooler. There are no other heat sources, so the intake intercooler heats up slowly. Especially when the ambient temperature is low, the low temperature of the intake intercooler makes it easier for water vapor in the mixer to condense into liquid water and enter the engine combustion chamber, causing engine damage. Summary of the Invention

[0006] The main objective of this invention is to propose a low-pressure EGR cooling system and its control method, which aims to solve the problem that in traditional intake intercooling, the coolant can only be heated by the air-fuel mixture entering the intake intercooler, resulting in slow temperature rise and easy condensation of water vapor in the mixer into liquid water, which then enters the engine combustion chamber and causes engine damage.

[0007] To achieve the above objectives, the present invention proposes a low-pressure EGR cooling system, comprising an engine and a low-pressure EGR system. The low-pressure EGR system is connected to the intake and exhaust ends of the engine, and is used to introduce a portion of the exhaust gas from the exhaust end into the intake end to form a gas-fuel mixture. The low-pressure EGR cooling system further includes:

[0008] An engine cooling system includes a first water-cooled circulation pipe, which is connected to the engine and the low-pressure EGR system to absorb heat and cool down a portion of the exhaust gas recovered by the engine and the low-pressure EGR system.

[0009] A water-cooled intercooling system includes a second water-cooled circulation pipe and an intake intercooler, wherein the intake intercooler is connected in series in the second water-cooled circulation pipe and is connected to the end of the intake pipe corresponding to the engine, for cooling the air-fuel mixture; and,

[0010] A connecting structure is provided between the first water-cooled circulation pipeline and the second water-cooled circulation pipeline for connecting and disconnecting the first water-cooled circulation pipeline and the second water-cooled circulation pipeline.

[0011] In one embodiment, the low-pressure EGR system includes:

[0012] An air intake pipe is connected to the air intake end, and an air filter is provided on the air intake pipe;

[0013] An exhaust pipe is connected to the outlet end, and a three-way catalytic converter is provided on the exhaust pipe; and,

[0014] The recovery pipeline has one end connected to the intake pipeline at the midpoint between the air filter and the intake end, and the other end connected to the exhaust pipeline of the three-way catalytic converter away from the outlet end. An EGR cooler is provided on the recovery pipeline.

[0015] The intake intercooler is connected to the intake pipe at the midpoint between the end of the recovery pipe and the intake end.

[0016] The first water-cooled circulation pipeline is connected to the EGR cooler.

[0017] In one embodiment, the water-cooled intercooling system further includes an intercooling water pump and an intercooling radiator, both of which are connected in series in the second water-cooling circulation pipeline.

[0018] In one embodiment, the engine cooling system further includes a water jacket and an engine water pump, the water jacket being connected to the engine, and both the water jacket and the engine water pump being disposed in the first water-cooled circulation pipeline.

[0019] In one embodiment, the engine cooling system further includes a condenser cooling water path, which is connected in parallel with the first water-cooled circulation pipe. The condenser cooling water path includes an engine radiator, and the inlet end of the engine radiator is equipped with a thermostat. The thermostat is used to disconnect the high-efficiency cooling water path from the first water-cooled circulation pipe; and / or,

[0020] The low-pressure EGR cooling system also includes a fan structure, and the intercooler and the engine radiator are both configured to correspond to the fan structure.

[0021] In one embodiment, a temperature sensor and an EGR valve are sequentially provided on the recovery pipeline corresponding to the exhaust end of the EGR cooler, and differential pressure sensors are provided on both sides of the recovery pipeline corresponding to the EGR valve.

[0022] An air flow meter and a mixing valve are installed on the intake pipe at the midpoint corresponding to the connection between the air filter and the recovery pipe; and / or

[0023] A throttle valve is provided on the intake pipe at a position corresponding to the midpoint between the intake intercooler and the intake end; and / or

[0024] An oxygen sensor is installed on the exhaust pipe between the three-way catalytic converter and the exhaust end.

[0025] In one embodiment, the conductive structure includes a connecting pipe and an electrically controlled valve, the electrically controlled valve being disposed on the connecting pipe, and both ends of the connecting pipe being connected to the second water-cooled circulation pipeline and the first water-cooled circulation pipeline, respectively; and / or,

[0026] The intake pipe and the exhaust pipe are respectively provided with a first bypass and a second bypass, and the first bypass and the second bypass are respectively provided with a pressure relief valve and an exhaust bypass valve.

[0027] The present invention also proposes a control method thereof, applied to the low-pressure EGR cooling system in the above-mentioned embodiments, wherein the control method of the low-pressure EGR cooling system includes the following control steps:

[0028] The conductive structure includes a connecting pipe and an electrically controlled valve;

[0029] The control method for the low-pressure EGR cooling system includes the following control steps:

[0030] Set the standard value for the external ambient temperature, as well as the standard value ranges for the coolant temperature of the first water-cooled circulation pipe and the coolant temperature of the second water-cooled circulation pipe;

[0031] Obtain the actual values ​​of the external ambient temperature, the coolant temperature of the first water-cooled circulation pipeline, and the coolant temperature of the second water-cooled circulation pipeline;

[0032] The opening state of the electronically controlled valve is controlled by the range between the actual value and the standard value, so that the first water-cooled circulation pipeline and the second water-cooled circulation pipeline are connected or disconnected.

[0033] In one embodiment, controlling the opening state of the electronically controlled valve by the range between the actual value and the standard value includes the following steps:

[0034] When the actual value of the external ambient temperature is less than its standard value, and the actual value of the coolant temperature in the second water-cooled circulation pipeline is less than its standard range, the electronically controlled valve opens, and the first water-cooled circulation pipeline and the second water-cooled circulation pipeline are connected to each other.

[0035] When the actual temperature of the coolant in the second water-cooled circulation pipeline exceeds its standard range, the electrically controlled valve closes, and the first water-cooled circulation pipeline and the second water-cooled circulation pipeline are separated from each other.

[0036] In one embodiment, the condenser cooling water circuit includes an engine radiator, and the inlet end of the engine radiator is provided with a thermostat;

[0037] The statement that "when the actual value of the external ambient temperature is less than its standard value, and the actual value of the coolant temperature in the second water-cooled circulation pipeline is less than its standard range, the electrically controlled valve opens, and the first water-cooled circulation pipeline and the second water-cooled circulation pipeline are interconnected" further includes:

[0038] When the actual value of the external ambient temperature is less than its standard value, and the engine is cold-started, the thermostat isolates the connection between the engine radiator and the first water-cooled circulation pipe.

[0039] The technical solution of this invention combines the traditionally separate engine cooling structure with a water-cooled intercooler structure, enabling the two cooling structures to be connected or disconnected based on the temperature difference in the two circulating cooling pipes. Specifically, when the intake air temperature is low and the engine is cold-starting, the engine cooling structure and the water-cooled intercooler structure can be connected. Because the coolant is heated by the engine combustion chamber and the high-temperature exhaust gas from the EGR cooler, the coolant temperature in the water-cooled intercooler rises rapidly, also accelerating the temperature rise of the water-cooled intercooler wall. As the air-fuel mixture passes through the water-cooled intercooler, the temperature difference between the air-fuel mixture and the intercooler decreases, reducing the risk of air-fuel mixture condensation. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0041] Figure 1 A schematic diagram of an embodiment of the low-pressure EGR cooling system provided by the present invention;

[0042] Figure 2 For application Figure 1 Flowchart of the control method for the low-pressure EGR cooling system in a medium-low pressure EGR cooling system;

[0043] Figure 3 For application Figure 2 A detailed flowchart of some control steps in the control method of a medium- and low-pressure EGR cooling system.

[0044] Description of Figure Numbers:

[0045] 100. Low-pressure EGR cooling system; 1. Intake pipe; 11. Air filter; 12. Air flow meter; 13. Mixing valve; 14. First bypass; 15. Pressure relief valve; 16. Throttle valve; 2. Exhaust pipe; 21. Three-way catalytic converter; 22. Oxygen sensor; 23. Second bypass; 24. Exhaust bypass valve; 3. Recycle pipe; 31. EGR cooler; 32. Temperature sensor; 33. EGR valve; 34. Differential pressure sensor; 4. Second water-cooled circulation pipe; 41. Intercooler water pump; 42. Intercooler radiator; 43. Intake intercooler; 5. Conducting structure; 51. Connecting pipe; 52. Electronic control valve; 6. Fan structure; 7. Engine; 8. First water-cooled circulation pipe; 81. Water jacket; 82. Engine water pump; 83. Engine radiator; 84. Thermostat.

[0046] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0049] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0050] After EGR exhaust gas mixes with fresh air, it passes through the turbocharger compressor, then the water-cooled intercooler, and finally enters the cylinders through the intake manifold. Inside the water-cooled intercooler, when the wall temperature is low, a large amount of water vapor in the EGR exhaust gas condenses below its dew point temperature. This condensate accumulates in the intercooler or intake manifold. When the accelerator pedal suddenly changes, causing a change in intake pressure, the accumulated liquid water can enter the combustion chamber, leading to misfire and, in severe cases, damage to the piston and connecting rod. This is especially prone to occur in foggy or rainy weather when the air is saturated with water. Common measures include reducing the EGR rate and increasing the intake manifold temperature to reduce the probability of misfire. However, reducing the EGR rate will affect engine fuel consumption and nitrogen oxide emissions, while increasing the intake manifold temperature will increase the engine's tendency to knock. Another technical solution involves adding a baffle in the intake manifold after the intercooler to block the condensate. However, this solution also affects the intake efficiency of the intake manifold, and excessive condensate can enter the engine combustion chamber and cause misfires, so it cannot completely solve the problem.

[0051] Furthermore, since the intake intercooler currently uses an independent cooling water circulation system, the intake intercooler and coolant can only be heated by the air-fuel mixture entering the intake intercooler. There are no other heat sources, so the intake intercooler heats up slowly. Especially when the ambient temperature is low, the low temperature of the intake intercooler makes it easier for water vapor in the mixer to condense into liquid water and enter the engine combustion chamber, causing engine damage.

[0052] This invention proposes a low-pressure EGR cooling system 100.

[0053] Please see Figure 1In one embodiment of the present invention, the structure of the low-pressure EGR system portion of the low-pressure EGR cooling system 100 is the same as the conventional arrangement, both being connected to the intake and exhaust circuits of the engine 7. The main difference is that the cooling system circuit in the low-pressure EGR cooling system 100 specifically includes an engine cooling system and a water-cooled intercooler system. In a conventional setup, the cooling circuits of these two cooling systems are independent of each other. The coolant in the water-cooled intercooler system can only be heated by the gas-fuel mixture in the low-pressure EGR system, resulting in a very slow temperature rise, especially when the ambient temperature is very low. The external ambient gas temperature is also relatively low, and the mixed gas has a certain temperature. When it comes into contact with the relatively cold intake intercooler, condensate will be generated and enter the engine 7, thereby affecting the operation of the engine 7. In this embodiment, the two cooling systems are integrated. Specifically, a conductive structure 5 connects the first water-cooled circulation pipe 8 and the second water-cooled circulation pipe 4. When the external environment is low and the engine 7 is started, the first water-cooled circulation pipe 8 is connected to the engine 7. The combustion of the engine 7 generates a large amount of heat, causing the coolant in the first water-cooled circulation pipe 8 to heat up rapidly. At this time, due to the influence of the external environment, the intake air temperature of the low-pressure EGR system is low, and the mixed gas formed with the recovered high-temperature exhaust gas also has a certain temperature. However, at this time, it is connected to the second water-cooled circulation pipe 4. The temperature of the intake intercooler 43 connected to pipe 4 is relatively low. When the mixed gas passes through the intake intercooler 43, the large temperature difference will cause a large amount of the mixed gas to condense into liquid. To avoid this, during the cold start of the engine 7, the conductive structure 5 can guide the coolant in the first water-cooled circulation pipe 8 to the second water-cooled circulation pipe 4, thereby allowing the coolant in the second water-cooled circulation pipe 4 to heat up quickly, minimizing the temperature difference between the intake intercooler 43 and the mixed gas, and effectively reducing the risk of mixed gas condensation. When the water temperature in the second water-cooled circulation pipe 4 is high, the wall temperature of the intercooler 43 is also high. At this time, after being cooled by the first water-cooled circulation pipe 8, some exhaust gas mixes with the intake gas, and the temperature difference between the mixed gas and the intake intercooler 43 is small enough. At this time, the conductive structure 5 is closed, allowing the two cooling systems to circulate independently.

[0054] Similar to conventional low-pressure EGR, the low-pressure EGR system in this embodiment also mainly includes three pipelines. Specifically, one end of the recovery pipeline 3 is connected to the air filter 11 in the intake pipeline 1 at the middle position of the intake end, and the other end is connected to the part of the three-way catalytic converter 21 on the exhaust pipeline 2 away from the exhaust end. In actual operation, the exhaust gas emitted by the engine 7 is treated by the three-way catalytic converter 21, and part of the treated exhaust gas enters the EGR cooler 31 on the recovery pipeline 3 through the pipeline. The first water-cooled circulation pipeline 8 absorbs the heat in the recovered exhaust gas to cool it down. At the same time, the coolant in the first water-cooled circulation pipeline 8 absorbs the heat from the engine 7 and the exhaust gas and then its temperature rises. The recovered exhaust gas, after being cooled by the EGR cooler 31, generally has a temperature below 120°C. In the intake pipe 1, outside air passes through the air filter 11 and mixes with the cooled recovered exhaust gas. This mixture then passes through the intake intercooler 43 for further cooling before entering the engine 7. The intake air temperature of the engine 7 is generally below 60°C. When the ambient temperature is low, the temperature of the intake intercooler 43 is also very low. Therefore, if it is not heated quickly, a lot of condensate will be generated in the mixture.

[0055] The water-cooled intercooler system and the engine cooling system are driven by corresponding intercooler water pump 41 and engine water pump 82, respectively, for coolant circulation. The intercooler water pump 41 and the intercooler radiator 42 are both connected in series in the second water-cooled circulation pipe 4. The intercooler radiator 42 continuously cools the coolant in the second water-cooled circulation pipe 4, thereby enabling the intake intercooler 43 to cool the air-fuel mixture.

[0056] Meanwhile, in the first water-cooled circulation pipe 8, the engine water pump 82 pumps coolant into the water jacket 81 connected to the engine 7. The water jacket 81 is heated by the combustion chamber. The heated coolant is then connected to the EGR cooler 31 through a pipe. The coolant is heated again by the high-temperature gas in the EGR cooler 31. The temperature of the heated coolant is high, and it will be reduced to a certain extent by the engine 7 radiator. The fan structure 6 is directly opposite the intercooler radiator 42 and the engine 7 radiator. During the heat dissipation process, it can effectively cool the pipes of the two cooling systems.

[0057] To quickly raise the engine water temperature, the thermostat 84 disconnects the entire first water-cooling circulation pipe 8 from the engine 7 radiator, causing the engine cooling system to operate in a small circulation mode. In this mode, the coolant pumped by the engine water pump 82 enters the water jacket 81 of the engine 7. Since the water jacket 81 is located around the combustion chamber, the coolant flowing in the water jacket 81 is heated by the large amount of heat generated by the combustion of gasoline in the combustion chamber. The heated coolant then flows to the EGR cooler 31 and other locations. The intake air temperature of the EGR cooler 31 can reach over 700°C, while the outlet air temperature is below 120°C. The EGR cooler 31 releases a large amount of heat, which is absorbed by the coolant in the engine cooling system. Because the thermostat 84 disconnects the engine 7 radiator from the first water-cooling circulation pipe 8, the coolant in the engine cooling system is rapidly heated by the water jacket 81 and the combustion exhaust gas in the EGR cooler 31, causing the coolant temperature to rise rapidly. This allows the coolant in the first water-cooled circulation pipe 8 to heat up rapidly when the outside temperature is low and the engine 7 is cold-started.

[0058] During the operation of the entire low-pressure EGR system, it is necessary to monitor the temperature of the recovered exhaust gas before and after cooling. This is because, as mentioned above, the intake temperature of the EGR cooler 31 can reach over 700℃, while the outlet temperature must be below 120℃. Therefore, a temperature sensor 32 is installed at the exhaust end of the EGR cooler 31, and an EGR valve 33 is installed on the pipeline. A differential pressure sensor 34 is located at both ends of the EGR valve 33, which can control the gas flow and ventilation volume in the intake pipeline 1 via the air flow meter 12 and the mixing valve 13. The EGR valve 33 controls the exhaust gas flow in the recovery pipeline 3, adjusting the mixing ratio of air and recovered exhaust gas in the mixed gas. A throttle valve 16 is also installed at one end of the intake pipeline 1 corresponding to the intake end to control the intake flow of the engine 7. Furthermore, an oxygen sensor 22 is installed on the exhaust pipeline 2, working in conjunction with the three-way catalytic converter 21 to make the treatment of exhaust gases more effective.

[0059] The conductive structure 5 mainly consists of a connecting pipe 51 and an electrically controlled valve 52. The two ends of the connecting pipe 51 connect to the main circuits of the second water-cooled circulation pipe 4 and the first water-cooled circulation pipe 8. The on / off state of these two cooling circuits is controlled by the electrically controlled valve 52 on the connecting pipe 51. Additionally, a first bypass 14 and a second bypass 23 are respectively provided on the intake pipe 1 and the outlet pipe, and a pressure relief valve 15 and an exhaust bypass valve 24 are respectively installed on the first bypass 14 and the second bypass 23 to relieve pressure on the intake pipe 1 and the outlet pipe, thereby increasing the safety of the entire low-pressure EGR cooling system 100 during operation.

[0060] This invention also proposes a control method for a low-pressure EGR cooling system 100. This control method is applied to the aforementioned low-pressure EGR cooling system 100, the specific structure of which is described in the above embodiments. Since this control method employs all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated upon here. Specifically, the control method for the low-pressure EGR cooling system 100 is based on the actual external temperature (intake air temperature) and the actual temperatures of the two cooling system loops mentioned above, to avoid a large temperature difference causing a large amount of water vapor in the intake pipe 1 to condense into liquid. The control method for the low-pressure EGR cooling system 100 mainly includes the following control steps:

[0061] Set the standard value of the external ambient temperature, as well as the standard value range of the coolant temperature of the first water-cooled circulation pipe 8 and the coolant temperature of the second water-cooled circulation pipe 4;

[0062] Obtain the actual values ​​of the external ambient temperature, the coolant temperature of the first water-cooled circulation pipe 8, and the coolant temperature of the second water-cooled circulation pipe 4;

[0063] The opening state of the electronically controlled valve 52 is controlled by the range between the actual value and the standard value, so that the first water-cooled circulation pipeline 8 and the second water-cooled circulation pipeline 4 are connected or disconnected.

[0064] First, the standard value of the external ambient temperature, as well as the standard value ranges of the coolant temperature of the first water-cooled circulation pipe 8 and the coolant temperature of the second water-cooled circulation pipe 4, need to be set. The determination of each standard value is related to the actual working condition of the entire EGR cooling system. In the actual adjustment process, it is necessary to compare the actual coolant temperature in the corresponding cooling pipe with the standard value range to determine whether it is necessary to connect or isolate the two water-cooled circulation pipes through the electronic control valve 52.

[0065] Controlling the opening state of the electronically controlled valve 52 by using the range between the actual value and the standard value includes the following steps:

[0066] When the actual value of the external ambient temperature is less than its standard value, and the actual value of the coolant temperature of the second water-cooled circulation pipe 4 is less than its standard value range, the electronically controlled valve 52 opens, and the first water-cooled circulation pipe 8 and the second water-cooled circulation pipe 4 are connected to each other.

[0067] When the actual temperature of the coolant in the second water-cooled circulation pipe 4 exceeds its standard range, the electrically controlled valve 52 closes, and the first water-cooled circulation pipe 8 and the second water-cooled circulation pipe 4 are separated from each other.

[0068] As mentioned above, the coolant temperature in the first water-cooled circulation pipe 8 is definitely higher than that in the second water-cooled circulation pipe 4 (because the second water-cooled circulation pipe 4 is connected to the engine, and the coolant heats up quickly). Therefore, it is only necessary to ensure that the coolant temperature in the second water-cooled circulation pipe 4 does not exceed the standard value range. The intake air temperature of the engine 7 is generally required to be below 60°C. The second water-cooled circulation pipe 4 needs to cool the mixed gas, so the temperature of the second water-cooled circulation pipe 4 must be below 60°C. However, in order to prevent the risk of condensation of the mixed gas due to the large temperature difference between the mixed gas temperature and the coolant temperature in the second water-cooled circulation pipe 4, the coolant temperature in the second water-cooled circulation pipe 4 cannot be too low, so it is generally set at 40°C to 50°C. After the engine 7 is operating normally, the temperature of the coolant in the first water-cooled circulation pipe 8 can reach above 100°C. Therefore, the engine cooling system cannot be used directly to cool the gas mixture. Generally, when the external environment is less than 10°C and the actual temperature of the coolant in the second water-cooled circulation pipe 4 is less than the minimum value of its standard range, the engine cooling system is used to heat up the second water-cooled circulation pipe 4 to minimize the temperature difference between the intake intercooler 43 and the gas mixture. When the engine 7 has been running for a period of time, the temperature of the second water-cooled circulation pipe 4 and the mixed gas is high. At this time, the temperature of the coolant in the second water-cooled circulation pipe 4 may exceed the standard value range (e.g., 50°C). The water-cooled intercooler system needs to reduce the temperature of the mixed gas to below 60°C. At this time, the high-temperature coolant of the engine 7 can no longer be used to cool the mixed gas. Therefore, the electronic control valve 52 should be disconnected to allow the water-cooled intercooler system to circulate independently. If the coolant temperature in the water-cooled intercooler system is too high, the intercooler radiator 42 can also be opened to reduce the coolant temperature.

[0069] The statement that "when the actual value of the external ambient temperature is less than its standard value, and the actual value of the coolant temperature in the second water-cooled circulation pipe 4 is less than its standard value, the electrically controlled valve 52 opens, and the first water-cooled circulation pipe 8 and the second water-cooled circulation pipe 4 are interconnected" further includes:

[0070] When the actual value of the external ambient temperature is less than its standard value, and the engine 7 is cold-started, the thermostat 84 isolates the engine 7 radiator.

[0071] This process involves rapidly raising the water temperature. Because the thermostat 84 disconnects the connection between the engine 7 radiator and the first water-cooled circulation pipe 8, the coolant in the engine cooling system is quickly heated by the water jacket 81 and the combustion exhaust gases in the EGR cooler 31, causing the coolant temperature to rise rapidly. This allows the coolant to bypass the engine 7 radiator at low temperatures, especially during cold starts, preventing the radiator from cooling the coolant in the first water-cooled circulation pipe 8 and thus achieving a rapid temperature increase.

[0072] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A low-pressure EGR cooling system, comprising an engine and a low-pressure EGR system, wherein the low-pressure EGR system is connected to the intake end and the exhaust end of the engine, for introducing a portion of the exhaust gas from the exhaust end into the intake end to form a gas-fuel mixture, characterized in that, The low-pressure EGR cooling system also includes: An engine cooling system includes a first water-cooled circulation pipe, which is connected to the engine and the low-pressure EGR system to absorb heat and cool down a portion of the exhaust gas recovered by the engine and the low-pressure EGR system. A water-cooled intercooling system includes a second water-cooled circulation pipe and an intake intercooler, wherein the intake intercooler is connected in series in the second water-cooled circulation pipe and is connected to the end of the intake pipe corresponding to the engine, for cooling the air-fuel mixture; and, A connecting structure is provided between the first water-cooled circulation pipeline and the second water-cooled circulation pipeline for connecting and disconnecting the first water-cooled circulation pipeline and the second water-cooled circulation pipeline.

2. The low-pressure EGR cooling system as described in claim 1, characterized in that, The low-pressure EGR system includes: An air intake pipe is connected to the air intake end, and an air filter is provided on the air intake pipe; An exhaust pipe is connected to the outlet end, and a three-way catalytic converter is provided on the exhaust pipe; and, The recovery pipeline has one end connected to the intake pipeline at the midpoint between the air filter and the intake end, and the other end connected to the exhaust pipeline of the three-way catalytic converter away from the outlet end. An EGR cooler is provided on the recovery pipeline. The intake intercooler is connected to the intake pipe at the midpoint between the end of the recovery pipe and the intake end. The first water-cooled circulation pipeline is connected to the EGR cooler.

3. The low-pressure EGR cooling system as described in claim 1, characterized in that, The water-cooled intercooling system also includes an intercooling water pump and an intercooling radiator, both of which are connected in series in the second water-cooled circulation pipeline.

4. The low-pressure EGR cooling system as described in claim 3, characterized in that, The engine cooling system also includes a water jacket and an engine water pump. The water jacket is connected to the engine, and both the water jacket and the engine water pump are installed in the first water-cooled circulation pipeline.

5. The low-pressure EGR cooling system as described in claim 4, characterized in that, The engine cooling system also includes a condenser cooling water circuit, which is connected in parallel with the first water-cooled circulation pipe. The condenser cooling water circuit includes an engine radiator, and the inlet end of the engine radiator is equipped with a thermostat. The thermostat is used to cut off the connection between the high-efficiency cooling water circuit and the first water-cooled circulation pipe. and / or, The low-pressure EGR cooling system also includes a fan structure, and the intercooler and the engine radiator are both configured to correspond to the fan structure.

6. The low-pressure EGR cooling system as described in claim 2, characterized in that, A temperature sensor and an EGR valve are sequentially installed on the recovery pipeline corresponding to the exhaust end of the EGR cooler, and a differential pressure sensor is installed on both sides of the recovery pipeline corresponding to the EGR valve. An air flow meter and a mixing valve are installed on the intake pipe at the midpoint corresponding to the connection between the air filter and the recovery pipe; and / or A throttle valve is provided on the intake pipe at a position corresponding to the midpoint between the intake intercooler and the intake end; and / or An oxygen sensor is installed on the exhaust pipe between the three-way catalytic converter and the exhaust end.

7. The low-pressure EGR cooling system as described in claim 2, characterized in that, The conductive structure includes a connecting pipe and an electrically controlled valve, the electrically controlled valve being mounted on the connecting pipe, and both ends of the connecting pipe being connected to the second water-cooled circulation pipe and the first water-cooled circulation pipe, respectively; and / or The intake pipe and the exhaust pipe are respectively provided with a first bypass and a second bypass, and the first bypass and the second bypass are respectively provided with a pressure relief valve and an exhaust bypass valve.

8. A control method for a low-pressure EGR cooling system, applied to the low-pressure EGR cooling system as described in any one of claims 1-7, characterized in that, The conductive structure includes a connecting pipe and an electrically controlled valve; The control method for the low-pressure EGR cooling system includes the following control steps: Set the standard value for the external ambient temperature, as well as the standard value ranges for the coolant temperature of the first water-cooled circulation pipe and the coolant temperature of the second water-cooled circulation pipe; Obtain the actual values ​​of the external ambient temperature, the coolant temperature of the first water-cooled circulation pipeline, and the coolant temperature of the second water-cooled circulation pipeline; The opening state of the electronically controlled valve is controlled by the range between the actual value and the standard value, so that the first water-cooled circulation pipeline and the second water-cooled circulation pipeline are connected or disconnected.

9. A control method for the low-pressure EGR cooling system according to claim 8, characterized in that, Controlling the opening state of the electronically controlled valve by the range between the actual value and the standard value includes the following steps: When the actual value of the external ambient temperature is less than its standard value, and the actual value of the coolant temperature in the second water-cooled circulation pipeline is less than its standard range, the electronically controlled valve opens, and the first water-cooled circulation pipeline and the second water-cooled circulation pipeline are connected to each other. When the actual temperature of the coolant in the second water-cooled circulation pipeline exceeds its standard range, the electrically controlled valve closes, and the first water-cooled circulation pipeline and the second water-cooled circulation pipeline are separated from each other.

10. A control method for the low-pressure EGR cooling system according to claim 9, characterized in that, The condenser cooling water circuit includes an engine radiator, and the inlet end of the engine radiator is equipped with a thermostat. The statement "when the actual value of the external ambient temperature is less than its standard value, and the actual value of the coolant temperature in the second water-cooled circulation pipeline is less than its standard range, the electrically controlled valve opens, and the first water-cooled circulation pipeline and the second water-cooled circulation pipeline are interconnected" further includes: When the actual value of the external ambient temperature is less than its standard value, and the engine is cold-started, the thermostat isolates the connection between the engine radiator and the first water-cooled circulation pipe.

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