Low-pressure EGR cooling system and control method thereof

Abstract

The invention discloses a low-pressure EGR cooling system and a control method thereof, and relates to the technical field of low-pressure EGR, the low-pressure EGR cooling system comprises an engine and a low-pressure EGR system, and the low-pressure EGR system is connected to the air inlet end and the air outlet end of the engine and used for guiding part of waste gas at the air outlet end into the air inlet end to form mixed gas; the low-pressure EGR cooling system further comprises an engine cooling system and a water-cooling inter-cooling cooling system, the engine cooling system comprises a first water-cooling circulation pipeline, and the first water-cooling circulation pipeline is connected to the engine and the low-pressure EGR system and used for conducting heat absorption and cooling on part of waste gas recycled by the engine and the low-pressure EGR system; according to the technical scheme, a traditional engine cooling structure and a traditional water-cooling intercooling structure which are separated from each other are combined, the two cooling structures can be communicated or separated according to different temperatures in the two circulating cooling pipelines, and the risk of mixed gas condensation is reduced.

Description

Technical Field

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

[0002] EGR (exhaust gas recirculation) technology was first used in diesel engines in the 1960s. When the EGR system is working, it will return part of the exhaust gas to the combustion chamber through the intake system, thereby lowering 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 taking exhaust gas from the front of the turbine, passing through the front of the compressor of the supercharger and entering the intake manifold, and then entering the engine cylinder. Low-pressure EGR generally refers to taking exhaust gas from the back of the turbine, passing through the compressor of the supercharger together with fresh air and entering the intake manifold, and then entering the engine cylinder. Thanks to the use of a mixing valve (throttle valve), there is no negative pressure difference area under low-speed and high-load conditions for low-pressure EGR, ensuring that a large amount of EGR exhaust gas can flow smoothly into the cylinder to play a role. Therefore, compared with high-pressure EGR, low-pressure EGR can achieve a higher EGR rate and a wider range of use. Low-pressure EGR has basically become a standard feature on the newly developed high-efficiency supercharged gasoline engines of major OEMs.

[0004] However, the low-pressure EGR system has a feature compared to the high-pressure EGR system, that is, after the EGR exhaust gas and fresh air are mixed, they pass through the turbocharger compressor, then 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 after being cooled below the dew point temperature. The condensed water gathers in the intercooler or intake manifold. When the accelerator pedal changes suddenly, causing the intake pressure to change, a large amount of liquid water will enter the combustion chamber and cause misfires. In severe cases, it will cause damage to the piston connecting rod. This is especially likely to happen in foggy or rainy weather with high air humidity, 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 misfires, 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 is also a technical solution that uses a baffle to add a baffle in the intake manifold after the intake air is intercooled 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 enter the engine combustion chamber and cause a fire, which cannot completely solve the problem.

[0005] And because the current intake intercooler uses 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. Therefore, the intake intercooler heats up slowly. Especially when the ambient temperature is low, due to the low temperature of the intake intercooler, 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, causing engine damage. Summary of the invention

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

[0007] To achieve the above object, the low-pressure EGR cooling system proposed in the present invention includes an engine and a low-pressure EGR system, wherein the low-pressure EGR system is connected to the intake end and the outlet end of the engine to introduce part of the exhaust gas at the outlet end into the intake end to form a mixed gas, and the low-pressure EGR cooling system also includes:

[0008] The engine cooling system comprises a first water-cooling circulation pipeline, wherein the first water-cooling circulation pipeline is connected to the engine and the low-pressure EGR system, and is used for absorbing heat and cooling 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-cooled circulation pipeline and an intake intercooler, wherein the intake intercooler is connected in series to the second water-cooled circulation pipeline and is connected to one end of the intake pipeline corresponding to the engine, so as to cool the mixed gas; and

[0010] The conducting structure is arranged between the first water-cooling circulation pipeline and the second water-cooling circulation pipeline, and is used for conducting and separating the first water-cooling circulation pipeline and the second water-cooling circulation pipeline.

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

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

[0013] an exhaust pipeline connected to the gas outlet end, and a three-way catalyst is arranged on the exhaust pipeline; and

[0014] A recovery pipeline, one end of which is connected to the intake pipeline corresponding to the middle position between the air filter and the intake end, and the other end of which is connected to the exhaust pipeline of the three-way catalyst away from the outlet end, and an EGR cooler is provided on the recovery pipeline;

[0015] The intake intercooler is connected to the intake pipeline at a position corresponding to the middle 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 one embodiment, the water-cooled intercooler cooling system further includes an intercooler water pump and an intercooler radiator, and the intercooler water pump and the intercooler radiator are both connected in series in the second water-cooled circulation pipeline.

[0018] In one embodiment, the engine cooling system further includes a water jacket and an engine water pump, the water jacket is connected to the engine, and the water jacket and the engine water pump are both arranged in the first water cooling circulation pipeline.

[0019] In one embodiment, the engine cooling system further includes a condenser heat dissipation water circuit, the condenser heat dissipation water circuit is connected in parallel with the first water cooling circulation pipeline, the condenser heat dissipation water circuit includes an engine condenser, and a thermostat is provided at the water inlet end of the engine condenser, and the thermostat is used to cut off the conductive relationship between the high-efficiency heat dissipation water circuit and the first water cooling circulation pipeline; and\or,

[0020] The low-pressure EGR cooling system also includes a fan structure, and the intercooler radiator and the engine radiator are both arranged corresponding 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 a pressure difference sensor is provided on both sides of the recovery pipeline corresponding to the EGR valve;

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

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

[0024] An oxygen sensor is arranged on the exhaust pipe between the three-way catalyst and the exhaust end.

[0025] In one embodiment, the conduction structure includes a connecting pipe and an electric control valve, wherein the electric control valve is arranged on the connecting pipe, and both ends of the connecting pipe are respectively connected to the second water-cooling circulation pipeline and the first water-cooling circulation pipeline; and / or,

[0026] The air inlet pipeline and the air outlet pipeline 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 gas bypass valve.

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

[0028] Setting a standard value of the external environment temperature, and respective standard value ranges of the first water-cooling circulation pipeline coolant temperature and the second water-cooling circulation pipeline coolant temperature;

[0029] Acquire 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] The opening state of the electric control valve is controlled by the actual value and the standard value range, so that the first water-cooling circulation pipeline and the second water-cooling circulation pipeline are connected to or separated from each other.

[0031] In one embodiment, controlling the opening state of the electric control valve by the actual value and the standard value range includes the following steps:

[0032] When the actual value of the external environment temperature is lower than its standard value, and the actual value of the coolant temperature of the second water-cooling circulation pipeline is lower than its standard value range, the electric control valve is opened, and the first water-cooling circulation pipeline and the second water-cooling circulation pipeline are connected to each other;

[0033] When the actual value of the coolant temperature in the second water-cooling circulation pipeline is greater than its standard value range, the electric control valve is closed, and the first water-cooling circulation pipeline and the second water-cooling circulation pipeline are separated from each other.

[0034] In one embodiment, the “when the actual value of the external environment temperature is less than its standard value, and the actual value of the coolant temperature of the second water-cooling circulation pipeline is less than its standard value range, the electric control valve is opened, and the first water-cooling circulation pipeline and the second water-cooling circulation pipeline are connected to each other” also includes:

[0035] When the actual value of the external ambient 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.

[0036] The technical solution of the present invention combines the traditional engine cooling structure separated from each other with the water-cooled intercooler cooling structure, and can form a conducting or separation relationship between the two cooling structures according to the difference in temperature in the two circulating cooling pipelines. Specifically, when the intake temperature is low and the engine is cold-started, the engine cooling structure can be connected with the water-cooled intercooler cooling structure. Due to the use of coolant heated by the engine combustion chamber and the high-temperature exhaust gas of the EGR cooler, the coolant temperature in the water-cooled intercooler rises rapidly, and the temperature rise of the water-cooled intercooler wall is also accelerated. When the mixed gas is cooled by the water-cooled intercooler, the temperature difference between the mixed gas and the intercooler decreases, reducing the risk of condensation of the mixed gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0038] Figure 1 A schematic structural diagram of an embodiment of a low-pressure EGR cooling system provided by the present invention;

[0039] Figure 2 For application Figure 1 A flow chart of a control method for a low-pressure EGR cooling system of a medium- and low-pressure EGR cooling system;

[0040] Figure 3 For application Figure 2 A detailed flow chart of some control steps in the control method of the medium and low pressure EGR cooling system.

[0041] Description of Figure Numbers:

[0042] 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; 2. Exhaust pipe; 21. Three-way catalytic converter; 22. Oxygen sensor; 23. Second bypass; 24. Exhaust bypass valve; 3. Recovery pipe; 31. EGR cooler; 32. Temperature sensor; 33. EGR valve; 34. Pressure difference sensor; 4. Second water-cooling circulation pipeline; 41. Intercooler water pump; 42. Intercooler radiator; 43. Intake intercooler; 5. Conducting structure; 51. Connecting pipe; 52. Electric control valve; 6. Fan structure; 7. Engine; 8. First water-cooling circulation pipeline; 81. Water jacket; 82. Engine water pump; 83. Engine condenser; 84. Thermostat.

[0043] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0046] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0047] After the EGR exhaust gas is mixed with fresh air, it passes through the turbocharger compressor, then through the water-cooled intercooler, and then enters 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 after being cooled below the dew point temperature. The condensed water will gather in the intercooler or intake manifold. When the accelerator pedal changes suddenly, causing the intake pressure to change, the large amount of liquid water that has gathered will enter the combustion chamber and cause misfires. In severe cases, it will cause damage to the piston connecting rod. This is especially likely to happen in foggy or rainy weather with high air humidity, 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 misfires, 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 is also a technical solution that uses a baffle to add a baffle in the intake manifold after the intake air is intercooled 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 enter the engine combustion chamber and cause a fire, which cannot completely solve the problem.

[0048] And because the current intake intercooler uses 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. Therefore, the intake intercooler heats up slowly. Especially when the ambient temperature is low, due to the low temperature of the intake intercooler, 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, causing engine damage.

[0049] The present invention provides a low-pressure EGR cooling system 100 .

[0050] See also Figure 1In one embodiment of the present invention, the structure of the low-pressure EGR system part in the low-pressure EGR cooling system 100 is the same as the conventional arrangement structure, and both are connected to the air intake and air outlet loops of the engine 7. The main difference is that the cooling system loop in the low-pressure EGR cooling system 100 specifically includes an engine cooling system and a water-cooled intercooler cooling system. In conventional settings, 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 its temperature rises very slowly, especially when the ambient temperature is very low, and the gas temperature of the external environment is also relatively low. The mixed gas has a certain temperature, and when it contacts the relatively cold intake intercooler, condensed water will be generated and enter the engine 7, thereby affecting the operation of the engine 7. In this embodiment, the above two cooling systems are integrated. Specifically, a conducting 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 is started, the first water-cooling circulation pipeline 8 is connected to the engine 7. The combustion of the engine 7 generates a large amount of heat, which causes the coolant in the first water-cooling circulation pipeline 8 to heat up quickly. 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 with the recovered part of the high-temperature exhaust gas also has a certain temperature at this time, but at this time, the mixed gas with the second water-cooling circulation pipeline 8 is relatively low. The temperature of the intake intercooler 43 connected to the pipeline 4 is relatively low. When the mixed gas passes through the intake intercooler 43, the large temperature difference will cause the mixed gas to condense into liquid in large quantities. In order to avoid this situation, when the engine 7 is cold started, the conduction 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 up quickly, so that the temperature difference between the temperature of the intake intercooler 43 and the mixed gas is as small as possible, which also effectively reduces the risk of condensation of the mixed gas. 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 the first water-cooling circulation pipeline 8 cools down, part of the exhaust gas is mixed with the intake air, and the temperature difference between the temperature of the formed mixed gas and the temperature of the intake intercooler 43 is small enough. At this time, the conduction structure 5 is in a closed state, so that the above two cooling systems are independently circulated.

[0051] Among them, similar to the conventional low-pressure EGR, the low-pressure EGR system in this embodiment also mainly includes three sections of pipelines. Specifically, one end of the recovery pipeline 3 is connected to the middle position between the air filter 11 in the intake pipeline 1 and the intake end, and the other end is connected to the part of the pipeline on the exhaust pipeline 2 where the three-way catalytic converter 21 is away from the outlet end. In the actual working process, the exhaust gas discharged by the engine 7 is processed by the three-way catalytic converter 21, and part of the exhaust gas after processing 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 of the engine 7 and the heat of the exhaust gas and the temperature rises. The temperature of the recovered exhaust gas after being cooled by the EGR cooler 31 is generally lower than 120°C. On the intake pipe 1, the external air passes through the air filter 11 and is mixed with the recovered exhaust gas after being cooled. The mixed gas is cooled by the intake intercooler 43 before entering the engine 7. Generally, the intake temperature of the engine 7 is below 60°C. When the ambient temperature is low, the temperature of the intake intercooler 43 is also very low, so if the temperature is not quickly increased, a lot of condensed water will be generated in the mixed gas.

[0052] The water-cooled intercooler cooling system and the engine cooling system are driven to circulate the coolant through the corresponding intercooler water pump 41 and the engine water pump 82. The intercooler water pump 41 and the intercooler radiator 42 are both connected in series in the second water-cooled circulation pipeline 4, and the intercooler radiator 42 can continuously cool the coolant in the second water-cooled circulation pipeline 4, so that the intake intercooler 43 can achieve the effect of cooling the mixed gas.

[0053] At the same time, in the first water-cooling circulation pipeline 8, the engine water pump 82 pumps out the 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 connected to the EGR cooler 31 through a pipeline. The coolant is heated again by the high-temperature gas in the EGR cooler 31. The temperature of the heated coolant is relatively high, and the temperature will be reduced by a certain amount through the engine 7 radiator. The fan structure 6 is facing the intercooler radiator 42 and the engine 7 radiator. During the heat dissipation process, the above two cooling system pipelines can be effectively cooled.

[0054] In order to increase the water temperature as quickly as possible, the engine 7 can disconnect the entire first water-cooling circulation pipeline 8 and the engine 7 radiator through the thermostat 84, so that the engine cooling system works in a small cycle. At this time, the coolant pumped out by the engine water pump 82 enters the water jacket 81 of the engine 7. Since the water jacket 81 is arranged around the combustion chamber, the coolant flowing in the water jacket 81 is heated by a large amount of heat generated by the combustion of gasoline in the combustion chamber. The coolant heated by the combustion chamber flows to the EGR cooler 31 and other positions. The intake temperature of the EGR cooler 31 can reach more than 700°C, and the outlet temperature of the EGR cooler 31 is lower than 120°C. The EGR cooler 31 releases a large amount of heat that is absorbed by the coolant in the engine cooling system. Since the thermostat 84 disconnects the connection between the engine 7 radiator and the first water-cooling circulation pipeline 8, the coolant in the engine cooling system is quickly heated by the combustion exhaust gas in the water jacket 81 and the EGR cooler 31, and the coolant temperature rises rapidly. Therefore, when the outside temperature is low and the engine 7 is cold-started, the coolant in the first water-cooling circulation pipeline 8 can be quickly heated up in the above manner.

[0055] 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, because the intake temperature of the EGR cooler 31 can reach more than 700°C, and the outlet temperature of the EGR cooler 31 is lower than 120°C. Therefore, a temperature sensor 32 is provided at the exhaust end of the EGR cooler 31, and an EGR valve 33 is provided on the pipeline. A pressure difference sensor 34 is provided at both ends of the EGR valve 33, which can control the gas flow and ventilation volume in the intake pipeline 1 through the air flow meter 12 and the mixing valve 13. The EGR valve 33 controls the exhaust gas flow in the recovery pipeline 3, and can adjust the mixing ratio of the air and the recovered exhaust gas of the mixed gas. A throttle 16 is also provided at one end of the intake pipeline 1 corresponding to the intake end to control the intake flow of the engine 7. In addition, an oxygen sensor 22 is provided on the exhaust pipeline 2 to work together with the three-way catalytic converter 21 to make the treatment of exhaust gas more effective.

[0056] The conducting structure 5 is mainly a structure of a connecting pipe 51 and an electric control valve 52. The two ends of the connecting pipe 51 conduct the main circuits of the second water-cooling circulation pipeline 4 and the first water-cooling circulation pipeline 8. The on-off status of the above two cooling circuits is controlled by the electric control valve 52 on the connecting pipe 51. In addition, the first bypass 14 and the second bypass 23 are respectively provided on the intake pipeline 1 and the outlet pipeline, and the first bypass 14 and the second bypass 23 are respectively provided with a pressure relief valve 15 and an exhaust gas bypass valve 24 to relieve the pressure of the intake pipeline 1 and the outlet pipeline, so as to increase the safety of the entire low-pressure EGR cooling system 100 during operation.

[0057] The present invention also proposes a control method for a low-pressure EGR cooling system 100, which is applied to the above-mentioned low-pressure EGR cooling system 100. The specific structure of the low-pressure EGR cooling system 100 refers to the above-mentioned embodiment. Since the control method adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here. Among them, the control method of the low-pressure EGR cooling system 100 should be controlled according to the actual external temperature (intake temperature) and the actual temperature of the above two cooling system loops to avoid the problem of large temperature difference causing a large amount of water vapor in the intake pipe 1 to condense into liquid. The control method of the low-pressure EGR cooling system 100 mainly includes the following control steps:

[0058] Setting a standard value of the external environment temperature, and respective standard value ranges of the coolant temperature of the first water-cooling circulation pipeline 8 and the coolant temperature of the second water-cooling circulation pipeline 4;

[0059] Acquire actual values ​​of the external environment temperature, the coolant temperature of the first water-cooling circulation pipeline 8, and the coolant temperature of the second water-cooling circulation pipeline 4;

[0060] The opening state of the electric control valve 52 is controlled by the actual value and the standard value range, so that the first water-cooling circulation pipeline 8 and the second water-cooling circulation pipeline 4 are connected to or separated from each other.

[0061] First, it is necessary to set the standard value of the external ambient temperature, as well as the standard value ranges of the coolant temperature of the first water-cooling circulation pipeline 8 and the coolant temperature of the second water-cooling circulation pipeline 4. The determination of each standard value is related to the actual working condition of the entire EGR cooling system. In the actual control process, it is necessary to compare the actual coolant temperature in the corresponding cooling pipeline with the standard value range to determine whether it is necessary to connect or isolate the above two water-cooling circulation pipelines through the electric control valve 52.

[0062] Controlling the opening state of the electric control valve 52 by the actual value and the standard value range includes the following steps:

[0063] When the actual value of the external environment temperature is lower than the standard value, and the actual value of the coolant temperature of the second water-cooling circulation pipeline 4 is lower than the standard value range, the electric control valve 52 is opened, and the first water-cooling circulation pipeline 8 and the second water-cooling circulation pipeline 4 are connected to each other;

[0064] When the actual value of the coolant temperature in the second water-cooling circulation pipeline 4 is greater than its standard value range, the electric control valve 52 is closed, and the first water-cooling circulation pipeline 8 and the second water-cooling circulation pipeline 4 are separated from each other.

[0065] As mentioned 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 heats up 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 temperature of the engine 7 is generally required to be lower than 60°C, 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 must be lower than 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 of the second water-cooling circulation pipeline 4, the temperature of the coolant in the second water-cooling circulation pipeline 4 cannot be too low, so it is generally set at 40°C to 50°C. After the engine 7 works normally, the temperature of the coolant in the first water-cooling circulation pipeline 8 can reach above 100°C, so the engine cooling system cannot be used directly to cool the mixed gas. Generally, when the external environment is less than 10°C and the actual value of the coolant temperature in the second water-cooling circulation pipeline 4 is less than the minimum value of its standard value range, the engine cooling system must be used to heat the second water-cooling circulation pipeline 4 to minimize the temperature difference between the intake intercooler 43 and the mixed gas. When the engine 7 runs for a period of time, the temperature of the second water-cooled circulation pipeline 4 and the mixed gas is relatively high. At this time, the coolant temperature in the second water-cooled circulation pipeline 4 may exceed the standard value range (for example, 50°C), and the water-cooled intercooler cooling 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. At this time, the electric control valve 52 must be disconnected to allow the water-cooled intercooler cooling system to circulate independently. If the coolant temperature in the water-cooled intercooler cooling system is too high, the intercooler radiator 42 can also be opened to reduce the temperature of the coolant.

[0066] The above “when the actual value of the external environment temperature is less than its standard value, and the actual value of the coolant temperature of the second water-cooling circulation pipeline 4 is less than its standard value, the electric control valve 52 is opened, and the first water-cooling circulation pipeline 8 and the second water-cooling circulation pipeline 4 are connected to each other” also includes:

[0067] When the actual value of the external ambient temperature is less than the standard value and the engine 7 is cold started, the thermostat 84 isolates the radiator of the engine 7 .

[0068] This process is to increase the water temperature as quickly as possible. In this process, since the thermostat 84 disconnects the connection between the engine 7 radiator and the first water-cooling circulation pipeline 8, the coolant in the engine cooling system is quickly heated by the water jacket 81 and the combustion exhaust gas in the EGR cooler 31, and the coolant temperature rises rapidly. Therefore, when the external temperature is low and the engine 7 is cold-started, the engine 7 radiator can be bypassed at low temperatures through the above method to avoid the engine 7 radiator cooling the coolant in the first water-cooling circulation pipeline 8, thereby achieving a rapid temperature increase effect of the coolant.

[0069] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in 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 an intake end and an outlet end of the engine, and is used to introduce part of the exhaust gas at the outlet end into the intake end to form a mixed gas, characterized in that: The low-pressure EGR cooling system further comprises: The engine cooling system comprises a first water-cooling circulation pipeline, wherein the first water-cooling circulation pipeline is connected to the engine and the low-pressure EGR system, and is used for absorbing heat and cooling part of the exhaust gas recovered by the engine and the low-pressure EGR system; a water-cooled intercooler cooling system, comprising a second water-cooled circulation pipeline and an intake intercooler, wherein the intake intercooler is connected in series to the second water-cooled circulation pipeline and is connected to one end of the intake pipeline corresponding to the engine, so as to cool the mixed gas; and The conducting structure is arranged between the first water-cooling circulation pipeline and the second water-cooling circulation pipeline, and is used for conducting and separating the first water-cooling circulation pipeline and the second water-cooling circulation pipeline.

2. The low-pressure EGR cooling system according to claim 1, characterized in that: The low-pressure EGR system comprises: An air intake pipeline is connected to the air intake end, and an air filter is provided on the air intake pipeline; an exhaust pipeline connected to the gas outlet end, and provided with a three-way catalyst; and A recovery pipeline, one end of which is connected to the intake pipeline corresponding to the middle position between the air filter and the intake end, and the other end of which is connected to the exhaust pipeline of the three-way catalyst away from the outlet end, and an EGR cooler is provided on the recovery pipeline; The intake intercooler is connected to the intake pipeline at a position corresponding to the middle between the end of the recovery pipeline and the intake end; The first water-cooling circulation pipeline is connected to the EGR cooler.

3. The low-pressure EGR cooling system according to claim 1, characterized in that: The water-cooled intercooler cooling system also includes an intercooler water pump and an intercooler radiator. The intercooler water pump and the intercooler radiator are both connected in series in the second water-cooled circulation pipeline.

4. The low-pressure EGR cooling system according to claim 3, characterized in that: The engine cooling system further comprises a water jacket and an engine water pump. The water jacket is connected to the engine. Both the water jacket and the engine water pump are arranged in the first water cooling circulation pipeline.

5. The low-pressure EGR cooling system according to claim 4, characterized in that: The engine cooling system further comprises a condenser heat dissipation water circuit, the condenser heat dissipation water circuit is connected in parallel with the first water cooling circulation pipeline, the condenser heat dissipation water circuit comprises an engine condenser, a thermostat is provided at the water inlet end of the engine condenser, and the thermostat is used to cut off the conduction relationship between the high-efficiency heat dissipation water circuit and the first water cooling circulation pipeline; and\or, The low-pressure EGR cooling system also includes a fan structure, and the intercooler radiator and the engine radiator are both arranged corresponding to the fan structure.

6. The low-pressure EGR cooling system according to claim 2, characterized in that: A temperature sensor and an EGR valve are sequentially arranged on the exhaust end of the recovery pipeline corresponding to the EGR cooler, and pressure difference sensors are arranged on both sides of the recovery pipeline corresponding to the EGR valve; An air flow meter and a mixing valve are provided on the intake pipe at a middle position 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 between the intake intercooler and the intake end; and / or, An oxygen sensor is arranged on the exhaust pipe between the three-way catalyst and the exhaust end.

7. The low-pressure EGR cooling system according to claim 2, characterized in that: The conduction structure includes a connecting pipe and an electric control valve, wherein the electric control valve is arranged on the connecting pipe, and both ends of the connecting pipe are respectively connected to the second water-cooling circulation pipeline and the first water-cooling circulation pipeline; and / or, The air inlet pipeline and the air outlet pipeline 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 gas bypass valve.

8. A control method for 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 the external environment temperature, and respective standard value ranges of the first water-cooling circulation pipeline coolant temperature and the second water-cooling circulation pipeline coolant temperature; Acquire actual values ​​of the external environment temperature, the first water-cooling circulation pipeline coolant temperature, and the second water-cooling circulation pipeline coolant temperature; The opening state of the electric control valve is controlled by the actual value and the standard value range, so that the first water-cooling circulation pipeline and the second water-cooling circulation pipeline are connected to or separated from each other.

9. A control method for a low-pressure EGR cooling system, characterized in that: Controlling the opening state of the electric control valve by the actual value and the standard value range comprises the following steps: When the actual value of the external environment temperature is lower than its standard value, and the actual value of the coolant temperature of the second water-cooling circulation pipeline is lower than its standard value range, the electric control valve is opened, and the first water-cooling circulation pipeline and the second water-cooling circulation pipeline are connected to each other; When the actual value of the coolant temperature in the second water-cooling circulation pipeline is greater than its standard value range, the electric control valve is closed, and the first water-cooling circulation pipeline and the second water-cooling circulation pipeline are separated from each other.

10. A control method for a low-pressure EGR cooling system, characterized in that: The above “when the actual value of the external environment temperature is less than its standard value, and the actual value of the coolant temperature of the second water-cooling circulation pipeline is less than its standard value range, the electric control valve is opened, and the first water-cooling circulation pipeline and the second water-cooling circulation pipeline are connected to each other” also includes: When the actual value of the external ambient 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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