Low-pressure EGR cooling system and control method therefor

Abstract

A low-pressure EGR cooling system (100), and a control method for a low-pressure EGR cooling system (100). The low-pressure EGR cooling system (100) comprises an engine (7) and a low-pressure EGR system, and the low-pressure EGR system is connected to a gas inlet end and a gas outlet end of the engine (7), and is used for directing part of exhaust gas at the gas outlet end into the gas inlet end so as to form mixed gas. The low-pressure EGR cooling system (100) also comprises an engine cooling system and a water-cooling inter-cooling system, the engine cooling system comprises a first water-cooling circulation pipe (8), and the first water-cooling circulation pipe (8) is connected to the engine (7) and the low-pressure EGR system, and is used for performing heat absorption and cooling on part of exhaust gas recovered by the engine (7) and the low-pressure EGR system. In the low-pressure EGR cooling system (100), the engine cooling system and the water-cooling inter-cooling system that are separated from each other are connected, so that the two cooling systems are communicated with or separated from each other on the basis of different temperatures of the cooling liquids in two circulating cooling pipes, thereby reducing the risk of condensation of the mixed gas.

Description

Low pressure EGR cooling system and control method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of low pressure EGR, in particular to a low pressure EGR cooling system and a control method thereof. BACKGROUND

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

[0003] From the structure, the EGR system is mainly divided into two types, high pressure EGR and low pressure EGR. High pressure EGR generally refers to taking exhaust gas before the turbine, and the exhaust gas enters the intake manifold before the compressor of the supercharger, and then enters the engine cylinder. Low pressure EGR generally refers to taking exhaust gas after the turbine, which enters the intake manifold after the compressor of the supercharger with fresh air, and then enters the engine cylinder. Thanks to the use of a mixing valve (throttle valve), low pressure EGR does not have a negative pressure difference area at low speed and high load conditions, ensuring that a large amount of EGR exhaust gas can flow into the cylinder and play a role. Therefore, compared with high pressure EGR, low pressure EGR can achieve higher EGR rate and wider use area. In the newly developed high-efficiency supercharged gasoline engine of major manufacturers, low pressure EGR has become a standard configuration.

[0004] However, the low pressure EGR system has a feature compared with the high pressure EGR system, that is, after the EGR exhaust gas and fresh air are mixed, they pass through the turbine supercharger, then pass through the water-cooled intercooler, and then enter the cylinder through the intake manifold. In the water-cooled intercooler, when the wall temperature is low, a large amount of water vapor in the EGR exhaust gas will form condensed water when it is below the dew point temperature after being cooled. The condensed water accumulates in the intercooler or the intake manifold, and when the accelerator pedal suddenly changes, causing the intake pressure to change, a large amount of liquid water will enter the combustion chamber, causing misfire, and in severe cases, causing piston rod damage. Especially in heavy fog weather or rainy weather, when the air is saturated with water, it is prone to occur. General measures include reducing the EGR rate and increasing the intake manifold temperature to reduce the probability of misfire, but reducing the EGR rate will affect the engine fuel consumption and nitrogen oxide emissions, and increasing the intake manifold temperature will increase the engine knock tendency. There is also a technical solution to add a baffle in the intake manifold after the intercooler to block the condensed water, but this solution will also affect the intake efficiency of the intake manifold, and a large amount of condensed water will also enter the engine combustion chamber to cause misfire, and cannot completely solve the problem.

[0005] And because the current intake intercooler adopts an independent cooling water circulation system, the intake intercooler and the coolant can only be heated by the mixed gas entering the intake intercooler, and there is no other heat source, so the intake intercooler is slowly warmed, especially when the ambient temperature is low, because the temperature of the intake intercooler is low, it is more likely to cause the water vapor in the mixer to condense into liquid water when it is cold, and enter the engine combustion chamber to cause engine damage. SUMMARY

[0006] The main purpose of the present application is to provide a low-pressure EGR cooling system and a control method thereof, which aims to solve the problem that the traditional intake intercooler and the coolant can only be heated by the mixed gas entering the intake intercooler, the intake intercooler is slowly warmed, and it is easy to cause the water vapor in the mixer to condense into liquid water when it is cold, and enter the engine combustion chamber to cause engine damage.

[0007] To achieve the above purpose, the low-pressure EGR cooling system provided by the present application comprises an engine and a low-pressure EGR system, the low-pressure EGR system is connected to the intake end and the exhaust end of the engine, and is used to guide part of the exhaust gas at the exhaust end into the intake end to form a mixed gas, and the low-pressure EGR cooling system further comprises:

[0008] An engine cooling system comprising a first water cooling circulation pipeline connected to the engine and the low-pressure EGR system, and used to absorb heat and cool part of the exhaust gas recovered by the engine and the low-pressure EGR system;

[0009] A water-cooled intercooler cooling system comprising a second water cooling circulation pipeline and an intake intercooler, the intake intercooler is connected to one end of the intake pipeline corresponding to the engine, and is used to cool the mixed gas; and

[0010] A conduction structure arranged between the first water cooling circulation pipeline and the second water cooling circulation pipeline, and used for the conduction and separation of the first water cooling circulation pipeline and the second water cooling circulation pipeline.

[0011] In an embodiment, the low-pressure EGR system comprises:

[0012] An intake pipeline connected to the intake end, and an air filter arranged on the intake pipeline;

[0013] An exhaust pipeline connected to the exhaust end, and a three-way catalyst arranged on the exhaust pipeline; and

[0014] A recovery pipeline, one end of which is connected to the intake pipeline at a position between the air filter and the intake end, and the other end of which is connected to the exhaust pipeline at a position away from the exhaust end, and an EGR cooler is arranged on the recovery pipeline.

[0015] The intake air intercooler is connected to the intake air pipeline at a position between the end of the recovery pipeline and the intake end;

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

[0017] In an embodiment, the water cooling intercooler cooling system further comprises an intercooler water pump and an intercooler radiator, both of which are connected in series in the second water cooling circulation pipeline.

[0018] In an embodiment, the engine cooling system further comprises a water jacket and an engine water pump, both of which are arranged in the first water cooling circulation pipeline.

[0019] In an embodiment, the engine cooling system further comprises a condenser cooling water circuit, which is connected in parallel to the first water cooling circulation pipeline, and the condenser cooling water circuit comprises an engine condenser, a water inlet end of the engine condenser is provided with a thermostat, the thermostat is used to cut off the conduction relationship between the high-efficiency cooling water circuit and the first water cooling circulation pipeline; and / or,

[0020] The low-pressure EGR cooling system further comprises a fan structure, and the intercooler radiator and the engine radiator are both arranged corresponding to the fan structure.

[0021] In an embodiment, a temperature sensor and an EGR valve are arranged in sequence on the recovery pipeline corresponding to the exhaust end of the EGR cooler, and a differential pressure sensor is arranged on the recovery pipeline corresponding to both sides of the EGR valve.

[0022] An air flow meter and a mixing valve are arranged on the intake air pipeline corresponding to a position between the air filter and the connection position of the recovery pipeline; and / or,

[0023] A throttle valve is arranged on the intake air pipeline corresponding to a position between the intake air intercooler and the intake end; and / or,

[0024] An oxygen sensor is arranged on the exhaust pipeline corresponding to a position between the three-way catalyst and the exhaust end.

[0025] In an embodiment, the conduction structure comprises a connecting pipe and an electrically controlled valve, the electrically controlled valve is arranged on the connecting pipe, and both ends of the connecting pipe are connected to the second water cooling circulation pipeline and the first water cooling circulation pipeline respectively; and / or,

[0026] First and second bypass pipelines are arranged on the intake air pipeline and the exhaust pipeline respectively, and a pressure relief valve and an exhaust gas bypass valve are arranged on the first and second bypass pipelines respectively.

[0027] The present application also provides a control method of the low-pressure EGR cooling system, which comprises the following steps:

[0028] setting a standard value of the external environment temperature, and a range of standard values of the first water cooling circulation pipeline coolant temperature and the second water cooling circulation pipeline coolant temperature;

[0029] acquiring actual values of the external environment temperature, the first water cooling circulation pipeline coolant temperature and the second water cooling circulation pipeline coolant temperature;

[0030] controlling the opening state of the electrically-controlled valve according to the actual values and the range of standard values, so as to connect or separate the first water cooling circulation pipeline and the second water cooling circulation pipeline.

[0031] In an embodiment, the step of controlling the opening state of the electrically-controlled valve according to the actual values and the range of standard values comprises the following steps:

[0032] when the actual value of the external environment temperature is less than the standard value, and the actual value of the second water cooling circulation pipeline coolant temperature is less than the range of standard values, the electrically-controlled valve is opened, and the first water cooling circulation pipeline and the second water cooling circulation pipeline are connected;

[0033] when the actual value of the second water cooling circulation pipeline coolant temperature is greater than the range of standard values, the electrically-controlled valve is closed, and the first water cooling circulation pipeline and the second water cooling circulation pipeline are separated.

[0034] In an embodiment, the step of “when the actual value of the external environment temperature is less than the standard value, and the actual value of the second water cooling circulation pipeline coolant temperature is less than the range of standard values, the electrically-controlled valve is opened, and the first water cooling circulation pipeline and the second water cooling circulation pipeline are connected” further comprises the following steps:

[0035] when the actual value of the external environment temperature is less than the standard value, and the engine is cold started, the thermostat separates the connection between the engine radiator and the first water cooling circulation pipeline.

[0036] The technical scheme of the present application combines the traditional engine cooling structure and the water-cooled intercooler cooling structure, and forms a conductive or separated relationship between the two cooling structures according to the temperature difference between the two circulating cooling pipelines. Specifically, when the intake temperature is low and the engine is cold-started, the engine cooling structure and the water-cooled intercooler cooling structure are conductive, and the coolant in the water-cooled intercooler is heated by the engine combustion chamber and the high-temperature exhaust gas of the EGR cooler, so that the temperature of the coolant in the water-cooled intercooler is quickly raised, and the temperature of the wall surface of the water-cooled intercooler is also quickly raised. When the mixture passes through the water-cooled intercooler, the temperature difference between the mixture and the intercooler is reduced, and the risk of condensation of the mixture is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical scheme in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained according to the structures shown in the drawings without creative labor for those skilled in the art.

[0038] Fig. 1 is a structural schematic diagram of an embodiment of a low-pressure EGR cooling system provided by the present application;

[0039] Fig. 2 is a flow chart of a control method of the low-pressure EGR cooling system applied to the low-pressure EGR cooling system in Fig. 1;

[0040] Fig. 3 is a detailed flow chart of part of the control steps in the control method of the low-pressure EGR cooling system applied to Fig. 2.

[0041] Brief description of the drawings: 100, low-pressure EGR cooling system; 1, intake pipeline; 11, air filter; 12, air flow meter; 13, mixing valve; 14, first bypass branch; 15, pressure relief valve; 16, throttle valve; 2, exhaust pipeline; 21, three-way catalyst; 22, oxygen sensor; 23, second bypass branch; 24, exhaust gas bypass valve; 3, recovery pipeline; 31, EGR cooler; 32, temperature sensor; 33, EGR valve; 34, differential pressure sensor; 4, second water-cooled circulating pipeline; 41, intercooler water pump; 42, intercooler radiator; 43, intake intercooler; 5, conductive structure; 51, connecting pipe; 52, electric control valve; 6, fan structure; 7, engine; 8, first water-cooled circulating pipeline; 81, water jacket; 82, engine water pump; 83, engine condenser; 84, thermostat.

[0042] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0043] Clearly, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of the present application.

[0044] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship, movement, etc. between the components in a certain posture, and if the certain posture changes, the directional indications will also change accordingly.

[0045] In addition, if the embodiments of the present application involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include at least one of the features. In addition, "and / or" or "and / or" appearing throughout the text means that the three parallel schemes include A scheme, or B scheme, or A and B schemes are satisfied at the same time. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist and is not within the scope of protection required by the present application.

[0046] After the EGR exhaust gas and fresh air are mixed, they pass through the turbocharger compressor, then pass through the water-cooled intercooler, and then pass through the intake manifold into the cylinder. In the water-cooled intercooler, when the wall temperature is low, a large amount of water vapor in the EGR exhaust gas will form condensed water when it is below the dew point temperature after being cooled. The condensed water accumulates in the intercooler or the intake manifold, and when the accelerator pedal suddenly changes, causing the intake pressure to change, a large amount of liquid water will enter the combustion chamber, causing misfire, and in severe cases, causing piston connecting rod damage. This is particularly prone to occur in heavy fog weather or rainy weather when the air is saturated with water. General measures include reducing the EGR rate, increasing the intake manifold temperature, and other measures to reduce the probability of misfire, but reducing the EGR rate will affect engine fuel consumption and nitrogen oxide emissions, and increasing the intake manifold temperature will increase the tendency of engine knock. There are also technical solutions that add a baffle to the intake manifold after the intercooler to block the condensed water, but this solution will also affect the intake efficiency of the intake manifold, and when a large amount of condensed water accumulates, it will also enter the engine combustion chamber to cause misfire, and cannot completely solve the problem.

[0047] And because the current intake intercooling adopts an independent cooling water circulation system, the intake intercooling and the cooling liquid can only be heated by the mixed gas entering the intake intercooling, and there is no other heat source, so the intake intercooling is slow to warm up, especially when the ambient temperature is low, because the intake intercooling temperature is low, it is more likely to cause the water vapor in the mixer to condense into liquid water due to the cold, and enter the engine combustion chamber to cause engine damage.

[0048] The application provides a low-pressure EGR cooling system 100.

[0049] Please refer to Fig. 1, in an embodiment of the present application, the structure of the low pressure EGR system part in the low pressure EGR cooling system 100 is the same as the conventional arrangement, which is connected to the intake and exhaust end loop of the engine 7. The main difference is that the cooling system loop in the low pressure EGR cooling system 100, specifically including the engine cooling system and the water-cooled intercooler cooling system, is conventionally arranged, and the cooling loops of the above two cooling systems are independent of each other. The coolant in the water-cooled intercooler cooling system can only be heated by the mixed gas in the low pressure EGR system, and the temperature rises slowly, especially when the ambient temperature is very low, the gas temperature of the external environment is also relatively low, and the mixed gas has a certain temperature. When it contacts the relatively cold intake intercooler, condensate water will be produced into the engine 7, thereby affecting the operation of the engine 7. In the embodiment, the above two cooling systems are integrated, specifically, a through structure 5 is provided between the first water cooling circulation pipeline 8 and the second water cooling circulation pipeline 4. When the external environment is low and the engine 7 starts, the first water cooling circulation pipeline 8 is connected to the engine 7 at this time, and the engine 7 generates a large amount of heat to promote the rapid heating of the coolant in the first water cooling circulation pipeline 8. At this time, due to the influence of the external environment, the intake temperature of the low pressure EGR system is relatively low, and the mixed gas formed by the recovered part of the high temperature exhaust gas also has a certain temperature at this time. However, the temperature of the intake intercooler 43 connected to the second water cooling circulation pipeline 4 is relatively low at this time. When the mixed gas passes through the intake intercooler 43, the large temperature difference will cause the mixed gas to condense into a liquid state in a large amount. In order to avoid this situation, when the engine 7 is cold started, the through structure 5 can guide the coolant in the first water cooling circulation pipeline 8 to the second water cooling circulation pipeline 4, so that the coolant in the second water cooling circulation pipeline 4 is heated relatively quickly, and the temperature difference between the intake intercooler 43 and the mixed gas is as small as possible. At this time, the risk of condensation of the mixed gas is also effectively reduced. When the water temperature in the second water cooling circulation pipeline 4 is high, the wall temperature of the intercooler 43 is also high. At this time, after part of the exhaust gas is cooled through the first water cooling circulation pipeline 8, the temperature difference between the mixed gas formed by the mixed gas and the intake intercooler 43 is small enough. At this time, the through structure 5 is in a closed state, so that the above two cooling systems are independently circulated.

[0050] In the embodiment, similar to the conventional low-pressure EGR, the low-pressure EGR system mainly comprises three pipes. Specifically, one end of the recovery pipe 3 is connected to the middle position of the air filter 11 and the intake end in the intake pipe 1, and the other end is connected to the part of the exhaust pipe 2 away from the exhaust end, where the three-way catalyst 21 is located. In actual operation, the exhaust gas emitted by the engine 7 is treated by the three-way catalyst 21, and part of the treated exhaust gas enters the EGR cooler 31 in the recovery pipe 3. The first water cooling circulation pipe 8 absorbs the heat in the recovered exhaust gas to reduce the temperature, and the coolant in the first water cooling circulation pipe 8 increases in temperature after absorbing the heat of the engine 7 and the exhaust gas. The temperature of the recovered exhaust gas after being cooled by the EGR cooler 31 is generally lower than 120℃. In the intake pipe 1, the external air after passing through the air filter 11 is mixed with the recovered exhaust gas after being cooled, and the mixed gas is further cooled by the intake intercooler 43 before entering the engine 7. Generally, the intake temperature of the engine 7 is below 60℃. When the ambient temperature is low, the temperature of the intake intercooler 43 is also low, so if it is not quickly warmed up, a lot of condensed water will be produced in the mixed gas.

[0051] The water cooling intercooling cooling system and the engine cooling system are respectively driven by the corresponding intercooling water pump 41 and engine water pump 82. The intercooling water pump 41 and intercooling radiator 42 are connected in series in the second water cooling circulation pipe 4. The intercooling radiator 42 can continuously cool the coolant in the second water cooling circulation pipe 4, so that the intake intercooler 43 can achieve the effect of cooling the mixed gas.

[0052] Meanwhile, in the first water cooling circulation pipe 8, the engine water pump 82 pumps the coolant into the water jacket 81 connected to the engine 7. The water jacket 81 is heated by the combustion chamber, and the heated coolant is connected by the pipe to the EGR cooler 31. The coolant is heated again by the high-temperature gas in the EGR cooler 31. The temperature of the heated coolant is relatively high, which will be reduced by the engine 7 radiator. The fan structure 6 is opposite to the intercooling radiator 42 and the engine 7 radiator, which can effectively cool the above two cooling system pipes during the cooling process.

[0053] The engine 7 in order to promote the water temperature as soon as possible, can be through the thermostat 84 disconnect the entire first water cooling cycle pipe 8 and the engine 7 radiator between the connection, make the engine cooling system work in small cycle, at this time the engine water pump 82 pumped into the cooling liquid into the engine 7 of the water jacket 81, because the water jacket 81 is arranged around the combustion chamber, the water jacket 81 flowing in the cooling liquid is heated by the combustion chamber in the gasoline combustion generated a large amount of heat, after the combustion chamber heated cooling liquid flow to the EGR cooler 31 and other positions, the EGR cooler 31 inlet temperature can reach more than 700 DEG C, the EGR cooler 31 outlet temperature is lower than 120 DEG C, the EGR cooler 31 release a large amount of heat is absorbed by the cooling liquid in the engine cooling system. Because the thermostat 84 disconnects the engine 7 radiator and the first water cooling cycle pipe 8 between the contact, so the cooling liquid in the engine cooling system is heated by the water jacket 81 and the EGR cooler 31 in the combustion exhaust gas, the cooling liquid temperature rises quickly. Thus can in the external temperature is low, and the engine 7 cold start time, through the above way, make the first water cooling cycle pipe 8 in the cooling liquid temperature rises quickly.

[0054] The whole low pressure EGR system works in the process, the need to monitor the temperature of the cooling of the recovered part of the exhaust gas before and after, because as above the EGR cooler 31 inlet temperature can reach more than 700 DEG C, the EGR cooler 31 outlet temperature is lower than 120 DEG C. So in the exhaust end of the EGR cooler 31 is provided with temperature sensor 32, while in the pipeline is provided with EGR valve 33, differential pressure sensor 34 is arranged at both ends of the EGR valve 33, can be through the air flow meter 12, the mixed valve 13 on the gas flow in the intake pipe 1 and air volume control, the EGR valve 33 control the exhaust gas flow in the recycling pipe 3, can adjust the air and the mixing ratio of the mixed gas recycling exhaust gas, in the intake pipe 1 corresponding to the intake end of one end is also provided with the throttle 16 control the intake flow of the engine 7. In addition, the exhaust pipe 2 is provided with oxygen sensor 22 and the three way catalyst 21 together, so that the treatment of exhaust gas is more effective.

[0055] The conduction structure 5 is mainly a structure of connecting pipes 51 and electrically controlled valves 52, both ends of the connecting pipes 51 are connected with the second water cooling circulation pipeline 4 and the main loop of the first water cooling circulation pipeline 8, and the electrically controlled valves 52 on the connecting pipes 51 control the on-off state of the two cooling loops. In addition, the first bypass pipeline 14 and the second bypass pipeline 23 are arranged on the air inlet pipeline 1 and the air outlet pipeline respectively, and the pressure relief valve 15 and the exhaust gas bypass valve 24 are arranged on the first bypass pipeline 14 and the second bypass pipeline 23 respectively, so as to relieve the pressure of the air inlet pipeline 1 and the air outlet pipeline respectively, thereby increasing the safety of the whole low-pressure EGR cooling system 100 during operation.

[0056] The application also provides a control method of the low-pressure EGR cooling system 100, which is applied to the low-pressure EGR cooling system 100 described above, and the specific structure of the low-pressure EGR cooling system 100 is referred to the above embodiments. Since the control method adopts all the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here. The control method of the low-pressure EGR cooling system 100 controls the operation according to the actual external temperature (intake temperature) and the actual temperature of the two cooling system loops, so as to avoid the problem that a large temperature difference leads to a large amount of water vapor in the air inlet pipeline 1 being condensed into liquid. The control method of the low-pressure EGR cooling system 100 mainly includes the following control steps:

[0057] Setting the standard value of the external environment temperature and the standard value range of the cooling liquid temperature of the first water cooling circulation pipeline 8 and the cooling liquid temperature of the second water cooling circulation pipeline 4;

[0058] Obtaining the actual value of the external environment temperature, the cooling liquid temperature of the first water cooling circulation pipeline 8 and the cooling liquid temperature of the second water cooling circulation pipeline 4;

[0059] Controlling the opening state of the electrically controlled valve 52 according to the actual value and the standard value range, so as to make the first water cooling circulation pipeline 8 and the second water cooling circulation pipeline 4 conduct or separate each other.

[0060] First, the standard value of the external environment temperature and the standard value range of the cooling liquid temperature of the first water cooling circulation pipeline 8 and the cooling liquid temperature of the second water cooling circulation pipeline 4 are set, and the determination of each standard value is related to the actual working condition of the whole EGR cooling system. In the actual control process, the actual cooling liquid temperature in the corresponding cooling pipeline is compared with the standard value range to determine whether the two water cooling circulation pipelines need to be connected or isolated by the electrically controlled valve 52.

[0061] Controlling the opening state of the electrically controlled valve 52 by the actual value and the standard value range includes the following steps:

[0062] When the actual value of the outside environment temperature is less than the standard value, and the actual value of the second water cooling circulation pipeline 4 coolant temperature is less than the standard value range, the electrically controlled valve 52 is opened, and the first water cooling circulation pipeline 8 and the second water cooling circulation pipeline 4 are mutually connected.

[0063] When the actual value of the second water cooling circulation pipeline 4 coolant temperature is greater than the standard value range, the electrically controlled valve 52 is closed, and the first water cooling circulation pipeline 8 and the second water cooling circulation pipeline 4 are mutually separated.

[0064] As described above, the coolant temperature of the first water cooling circulation pipeline 8 is definitely higher than that of the second water cooling circulation pipeline 4 (because the second water cooling circulation pipeline 4 is connected to the engine, and the coolant temperature rises quickly), so it is only necessary to ensure that the coolant temperature of the second water cooling circulation pipeline 4 does not exceed the standard value range. The intake air temperature of the engine 7 is generally required to be lower than 60℃, and the second water cooling circulation pipeline 4 needs to cool the mixed gas, so the temperature of the second water cooling circulation pipeline 4 needs to be lower than 60℃, but in order to prevent the risk of mixed gas condensation due to a large temperature difference between the mixed gas temperature and the coolant temperature of the second water cooling circulation pipeline 4, the temperature of the coolant in the second water cooling circulation pipeline 4 also cannot be too low, so it is generally set to 40℃-50℃. The temperature of the coolant in the first water cooling circulation pipeline 8 can reach more than 100℃ after the engine 7 normally works, so the engine cooling system cannot be directly used to cool the mixed gas. Generally, when the outside environment is less than 10℃, and the actual value of the second water cooling circulation pipeline 4 coolant temperature is less than the minimum value of the standard value range, at this time, the second water cooling circulation pipeline 4 needs to be warmed up by the engine cooling system to minimize the temperature difference between the intercooler 43 and the mixed gas. When the engine 7 runs for a period of time, the temperature of the second water cooling circulation pipeline 4 and the mixed gas is high, at this time, the coolant temperature in the second water cooling circulation pipeline 4 may exceed the standard value range (for example, 50℃), and the water-cooled intercooled cooling system needs to reduce the temperature of the mixed gas to below 60℃, at this time, the engine 7 high-temperature coolant cannot be used to cool the mixed gas, at this time, the electrically controlled valve 52 is disconnected, and the water-cooled intercooled cooling system is independently circulated. If the coolant temperature in the water-cooled intercooled cooling system is too high, the intercooler radiator 42 can also be opened to reduce the temperature of the coolant.

[0065] The "when the actual value of the external environment temperature is less than its standard value, and the actual value of the second water cooling circulation pipeline 4 cooling liquid temperature is less than its standard value, the electric control valve 52 is opened, the first water cooling circulation pipeline 8 and the second water cooling circulation pipeline 4 are mutually conducted" further includes:

[0066] When the actual value of the external environment temperature is less than its standard value, and the engine 7 is cold started, the thermostat 84 isolates the engine 7 radiator.

[0067] The process is, in order to quickly raise the water temperature, in the process, because the thermostat 84 disconnects the engine 7 radiator and the first water cooling circulation pipeline 8, so the cooling liquid in the engine cooling system is quickly heated by the water jacket 81 and the EGR cooler 31 combustion exhaust gas, and the cooling liquid temperature rises quickly. Thus, when the external air temperature is low, and the engine 7 is cold started, by the above method, the engine 7 radiator is bypassed at low temperature, avoiding the engine 7 radiator cooling the cooling liquid in the first water cooling circulation pipeline 8, thereby realizing the effect of rapid heating of the cooling liquid.

[0068] The above-mentioned is only an exemplary embodiment of the present application, and does not limit the patent scope of the present application, any equivalent structural transformation made under the technical concept of the present application, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A low pressure EGR cooling system comprising an engine and a low pressure EGR system connected to an intake end and an exhaust end of the engine for conducting a portion of exhaust gas from the exhaust end to the intake end to form a mixture gas, characterized by, The low-pressure EGR cooling system further comprises: The engine cooling system comprises a first water cooling circulation pipeline connected to the engine and the low-pressure EGR system to absorb heat and cool part of the exhaust gas recovered by the engine and the low-pressure EGR system; The water cooling inter-cooling cooling system comprises a second water cooling circulation pipeline and an air intake inter-cooler connected to the second water cooling circulation pipeline and the air intake pipeline corresponding to one end of the engine to cool the mixed gas; and A conducting structure is arranged between the first water cooling circulation pipeline and the second water cooling circulation pipeline to conduct and separate the first water cooling circulation pipeline and the second water cooling circulation pipeline.

2. The low pressure EGR cooling system of claim 1, wherein, The low-pressure EGR system comprises: An air intake pipeline connected to the air intake end and provided with an air filter; An exhaust pipeline connected to the air outlet end and provided with a three-way catalyst; and A recovery pipeline connected to the air intake pipeline at a position between the air filter and the air intake end and connected to the exhaust pipeline at a position away from the air outlet end and provided with an EGR cooler; The air intake inter-cooler is connected to the air intake pipeline at a position between the recovery pipeline end and the air intake end; The first water cooling circulation pipeline is connected to the EGR cooler.

3. The low pressure EGR cooling system of claim 1, wherein, The water cooling inter-cooling cooling system further comprises an inter-cooling water pump and an inter-cooling radiator both connected to the second water cooling circulation pipeline.

4. The low pressure EGR cooling system of claim 3, wherein, The engine cooling system further comprises a water jacket connected to the engine and an engine water pump both arranged in the first water cooling circulation pipeline.

5. The low pressure EGR cooling system of claim 4, wherein, The engine cooling system further comprises a condenser heat dissipation water circuit connected in parallel to the first water cooling circulation pipeline, the condenser heat dissipation water circuit comprising an engine condenser provided with a thermostat to cut off the conducting relationship between the high-efficiency heat dissipation water circuit and the first water cooling circulation pipeline; And / or The low-pressure EGR cooling system further comprises a fan structure corresponding to the inter-cooling radiator and the engine radiator.

6. The low pressure EGR cooling system of claim 2, wherein, A temperature sensor and an EGR valve are arranged in sequence on the recovery pipeline corresponding to the exhaust end of the EGR cooler, and a pressure difference sensor is arranged on the recovery pipeline corresponding to both sides of the EGR valve; An air flow meter and a mixing valve are arranged on the air intake pipeline corresponding to a position between the air filter and the recovery pipeline connection; and / or A throttle valve is arranged on the air intake pipeline corresponding to a position between the air intake inter-cooler and the air intake end; and / or An oxygen sensor is arranged on the exhaust pipeline corresponding to a position between the three-way catalyst and the air outlet end.

7. The low pressure EGR cooling system of claim 2, wherein, The conducting structure comprises a connecting pipeline and an electric control valve arranged on the connecting pipeline, and both ends of the connecting pipeline are connected to the second water cooling circulation pipeline and the first water cooling circulation pipeline, respectively; and / or The first bypass and the second bypass are respectively arranged on the air inlet pipeline and the air outlet pipeline, and a pressure relief valve and a waste gas bypass valve are respectively arranged on the first bypass and the second bypass.

8. A control method of a low-pressure EGR cooling system, applied to the low-pressure EGR cooling system according to any one of claims 1 to 7, characterized in that, The control method of the low-pressure EGR cooling system comprises the following control steps: setting a standard value of an external environment temperature, and a standard value range of the first water cooling circulation pipeline coolant temperature and the second water cooling circulation pipeline coolant temperature; acquiring actual values of the external environment temperature, the first water cooling circulation pipeline coolant temperature and the second water cooling circulation pipeline coolant temperature; controlling the opening state of the electric control valve by the actual values and the standard value range, so as to make the first water cooling circulation pipeline and the second water cooling circulation pipeline conduct or separate to each other.

9. A control method of a low-pressure EGR cooling system, characterized by, controlling the opening state of the electric control valve by the actual values and the standard value range comprises the following steps: when the actual value of the external environment temperature is less than the standard value, and the actual value of the second water cooling circulation pipeline coolant temperature is less than the standard value range, the electric control valve is opened, and the first water cooling circulation pipeline and the second water cooling circulation pipeline conduct to each other; when the actual value of the second water cooling circulation pipeline coolant temperature is greater than the standard value range, the electric control valve is closed, and the first water cooling circulation pipeline and the second water cooling circulation pipeline separate to each other.

10. A control method of a low-pressure EGR cooling system, characterized by, In the "when the actual value of the external environment temperature is less than the standard value, and the actual value of the second water cooling circulation pipeline coolant temperature is less than the standard value range, the electric control valve is opened, and the first water cooling circulation pipeline and the second water cooling circulation pipeline conduct to each other", further comprising: when the actual value of the external environment temperature is less than the standard value, and the engine is cold started, the thermostat isolates the connection between the engine radiator and the first water cooling circulation pipeline.

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