An EGR cooling and transmission oil temperature control system and method of controlling the same

Abstract

The application discloses an EGR cooling and gearbox oil temperature control system, which comprises an engine, a water pump, a thermostat, a radiator, an EGR cooler and a gearbox oil cooler, the water pump is communicated with the water jacket of the engine, the thermostat is communicated with the water pump and the engine, the EGR cooler and the gearbox oil cooler are connected in parallel on the thermostat, one end of the radiator is communicated with the thermostat, and one end of the radiator is communicated with the EGR cooler and / or the gearbox oil cooler. The application also provides an EGR cooling and gearbox oil temperature control method, and aims to cool the EGR gas by using the cooling water with relatively low temperature, so as to improve the EGR gas density; meanwhile, the cooling water with different temperatures is used to regulate and control the gearbox oil temperature, improve the gearbox mechanical efficiency, reduce the vehicle fuel consumption and prolong the gearbox service life.

Description

Technical Field

[0001] This invention belongs to the field of vehicle technology, specifically relating to an EGR cooling and transmission oil temperature control system and its control method. Background Technology

[0002] Applying EGR technology to gasoline engines can reduce fuel consumption. Depending on the engine and EGR control strategy, the effective fuel consumption rate can be reduced by 3%-8%. In gasoline engines with an added EGR system, NOx emissions are significantly reduced by up to approximately 80% as the EGR rate increases. Therefore, combining a three-way catalytic converter and EGR technology can significantly improve the fuel economy of gasoline engines under certain operating conditions while meeting China VI emission regulations. Based on the significant role of EGR technology in energy conservation and emission reduction, most gasoline engines in China are now equipped with EGR technology.

[0003] Engine exhaust gases are typically at high temperatures; however, lower exhaust gas temperatures result in better NOx suppression in the engine. Therefore, the EGR (Exhaust Gas Refrigerant) is equipped with a cooling device to lower the exhaust gas temperature. Current technology involves drawing water from the engine block, which flows through the EGR cooler and back to the thermostat, thus cooling the EGR gas flowing within the EGR cooler.

[0004] Once the engine is fully warmed up, the temperature of the engine block and the intake manifold rises. At the same time, the temperature of the coolant flowing out of the block is relatively high. As a result, the EGR gas temperature becomes higher than that during the warm-up process, and the EGR gas density becomes lower than that during the warm-up process. The reduced EGR gas density makes it difficult to increase the EGR rate and effectively reduce fuel consumption and NOx emissions.

[0005] When the engine is cold-started, the transmission fluid temperature is low, and the fluid viscosity is high, resulting in poor lubrication. As the automatic transmission operates, some power loss is converted into heat, causing the transmission fluid temperature to rise. If the fluid temperature reaches a certain level, it will lead to changes in the lubricating oil's properties, such as decreased viscosity and accelerated aging and deterioration. If the lubricating oil film is damaged, it will lose its lubricating function, causing damage to the gear meshing surfaces or bearing surfaces, resulting in equipment failure and significantly impacting the transmission's lifespan. Therefore, controlling the transmission fluid temperature is an effective means to improve transmission mechanical efficiency, reduce overall vehicle fuel consumption, and extend transmission life.

[0006] If the transmission oil cooler is located in the small circulation loop of the engine cooling system, it is generally connected in parallel with the heater circuit. In this configuration, during the engine warm-up phase, the thermostat shuts off the circulation of the heater and oil cooler to ensure rapid engine temperature rise. During this engine warm-up phase, the transmission oil cannot be warmed. After the engine warms up, the fluid entering the transmission oil cooler is high-temperature water. Under high-temperature and high-load conditions, the transmission oil temperature remains high, affecting the transmission's lifespan and easily leading to high-temperature torque limiting, resulting in a poor user experience.

[0007] If the transmission oil cooler is located in the main cooling system loop, with water drawn from behind the radiator and then returning to the water pump, then during the engine warm-up phase, no coolant flows through the transmission oil cooler. The transmission oil temperature rises only through frictional heat generation, resulting in a slow temperature increase and significant frictional losses. Under these conditions, the transmission's mechanical efficiency is low, leading to high overall vehicle fuel consumption.

[0008] Chinese invention patent No. 202210912873.4, published on November 8, 2022, discloses a method, apparatus, device, and readable storage medium for rapid engine warm-up. The method includes: acquiring the engine coolant temperature; if the engine coolant temperature is less than a first preset threshold, and at least one of the air rail temperature signal and EGR temperature signal is valid, then when at least one of the valid temperature values ​​is less than a second preset threshold, controlling the engine speed to increase to a first preset speed, wherein the second preset threshold is less than the first preset threshold; when the detected air rail temperature or EGR temperature is greater than the first preset temperature, controlling the engine speed to decrease to the second preset speed. The technical solution provided in this prior art cannot solve the aforementioned technical problem. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide an EGR cooling and transmission oil temperature control system and its control method, which utilizes relatively low-temperature cooling water to cool EGR gas, thereby increasing EGR gas density; simultaneously, it uses cooling water of different temperatures to regulate transmission oil temperature, thereby improving transmission mechanical efficiency, reducing overall vehicle fuel consumption, and extending transmission life.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows: an EGR cooling and transmission oil temperature control system, comprising an engine, a water pump, a thermostat, a radiator, an EGR cooler, and a transmission oil cooler. The water pump is connected to the water jacket of the engine, the thermostat is connected to the water pump and the engine, the EGR cooler and the transmission oil cooler are connected in parallel to the thermostat, one end of the radiator is connected to the thermostat, and one end of the radiator is connected to the EGR cooler and / or the transmission oil cooler.

[0011] Furthermore, the thermostat includes thermostat I and thermostat II. The inlet of thermostat I is connected to the outlet of the water pump, and the outlet of thermostat I is connected to the inlet of the radiator, the inlet of the EGR cooler, and the inlet of the transmission oil cooler. The outlets of the radiator, the EGR cooler, and the transmission oil cooler are connected to the inlet of thermostat II, and the outlet of thermostat II is connected to the water jacket of the engine.

[0012] Furthermore, the control system also includes a three-way valve I and a three-way valve II. The inlet of the EGR cooler is connected to the outlet of the thermostat I and the outlet of the radiator through the three-way valve I. The inlet of the gearbox oil cooler is connected to the outlet of the thermostat I and the outlet of the radiator through the three-way valve II.

[0013] Furthermore, the engine, water pump, thermostat I, three-way valve I, EGR cooler, and thermostat II constitute the first circulation path. During the engine warm-up phase, the first circulation path mode is adopted. Water in the engine water jacket flows out from the outlet of thermostat I through the water pump, is switched by three-way valve I, flows into the EGR cooler, and then flows back to the engine through thermostat II.

[0014] Furthermore, the engine, water pump, thermostat I, radiator, three-way valve I, EGR cooler, and thermostat II constitute the second circulation path. After the engine warm-up phase, the second circulation path mode is adopted. The water in the engine water jacket flows out from the outlet of thermostat I through the water pump, passes through the radiator, is switched by three-way valve I, flows into the EGR cooler, and then flows back to the engine through thermostat II.

[0015] Furthermore, the engine, water pump, thermostat I, three-way valve II, transmission oil cooler, and thermostat II constitute the third circulation path. When the transmission oil temperature needs to be heated, the third circulation path mode is adopted. The hot water in the engine water jacket flows out from the outlet of thermostat I through the water pump, is switched through three-way valve II, flows into the transmission oil cooler, and then flows back to the engine through thermostat II.

[0016] Furthermore, the engine, water pump, thermostat I, radiator, three-way valve II, transmission oil cooler, and thermostat II constitute the fourth circulation path. When the transmission oil temperature needs to be heated, the fourth circulation path mode is adopted. The hot water in the engine water jacket flows out from the outlet of thermostat I through the water pump, passes through the radiator, is switched by three-way valve II, flows into the transmission oil cooler, and then flows back to the engine through thermostat II.

[0017] Based on the aforementioned EGR cooling and transmission oil temperature control system, this invention also relates to an EGR cooling and transmission oil temperature control method. The control method includes EGR cooling control and transmission oil temperature control. The EGR cooling control is as follows: when the engine coolant temperature T is less than a fixed value T1, the engine is in the warm-up stage, using the first circulation path; when the engine coolant temperature T is greater than the fixed value T1, the engine needs cooling, using the second circulation path. The transmission oil temperature control is as follows: when the transmission oil temperature K is less than a fixed value K1, the transmission oil needs heating, using the third circulation path; when the transmission oil temperature K is greater than the fixed value K1, the transmission oil needs cooling, using the fourth circulation path.

[0018] Furthermore, the control method specifically includes the following steps:

[0019] Step 100: Obtain the current engine coolant temperature T;

[0020] Step 110: Obtain the current transmission oil temperature K;

[0021] Step 120: Determine whether the current engine coolant temperature T is higher than the fixed value T1. If the determination result is positive, proceed to step 140. If the determination result is negative, proceed to step 150.

[0022] Step 130: Determine whether the current transmission oil temperature K is higher than the fixed value K1. If the determination result is positive, proceed to step 160; if the determination result is negative, proceed to step 170.

[0023] Step 140: By opening and closing the three-way valve I, the second circulation loop is realized. The water in the engine water jacket flows from the outlet of thermostat I into the radiator through the engine water pump, then flows to the three-way valve I and back to thermostat II through the EGR cooler, and then back to the engine circulation.

[0024] Step 150: By opening and closing the three-way valve I, the first circulation loop is realized. The water in the engine water jacket flows from the outlet of thermostat I to the three-way valve I via the engine water pump, flows back to thermostat II via the EGR cooler, and then flows back to the engine circulation.

[0025] Step 160: By opening and closing the three-way valve II, the fourth circulation loop can be realized. The water in the engine water jacket flows from the outlet of the thermostat I into the radiator through the engine water pump, then flows to the three-way valve II, and then flows back to the thermostat II through the transmission oil cooler, and then flows back to the engine circulation.

[0026] Step 170: By opening and closing the three-way valve II, the third circulation loop is realized. The water in the engine water jacket flows from the outlet of thermostat I through the engine water pump to the three-way valve I, then flows back to thermostat II through the transmission oil cooler, and then flows back to the engine circulation.

[0027] The advantages of using the technical solution of this invention are:

[0028] 1. This invention, through the design of an EGR cooling and transmission oil temperature control system and control method, can utilize relatively low-temperature cooling water to cool EGR gas, thereby increasing the EGR gas density; at the same time, by utilizing cooling water of different temperatures, the transmission oil temperature can be regulated, thereby improving the mechanical efficiency of the transmission, reducing overall vehicle fuel consumption, and extending the transmission life.

[0029] 2. This invention switches between heating and cooling circulation loops via a three-way solenoid valve, based on different transmission oil temperature requirements. In heating mode, the relatively high-temperature coolant heats the transmission oil, rapidly increasing its temperature, reducing viscosity, minimizing churning losses, reducing friction losses, improving transmission mechanical efficiency, and lowering overall vehicle fuel consumption. In cooling mode, the low-temperature coolant cooled by the radiator enters the transmission oil cooler, rapidly cooling the transmission oil and preventing high-temperature torque limiting due to excessively high transmission oil temperature. This also prevents the lifespan of clutch friction plates and brake pads from decreasing, further extending the transmission's lifespan. Attached Figure Description

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0031] Figure 1 This is a flowchart of the EGR cooling control and transmission oil temperature control of the present invention;

[0032] Figure 2 This is a schematic diagram of the EGR cooling control and transmission oil temperature control system of the present invention;

[0033] Figure 3 This is a schematic diagram of the first circulation path of the EGR cooling control of the present invention;

[0034] Figure 4 This is a schematic diagram of the second circulation path for EGR cooling control in this invention;

[0035] Figure 5 This is a schematic diagram of the third circulation path for the transmission oil temperature control of the present invention;

[0036] Figure 6 This is a schematic diagram of the fourth circulation path for the transmission oil temperature control of the present invention.

[0037] The markings in the above diagram are as follows: 01, Three-way valve I; 02, Three-way valve II; 03, Engine; 04, Thermostat; 041, Thermostat I; 042, Thermostat II; 05, Water pump; 06, Radiator; 07, EGR cooler; 08, Transmission oil cooler. Detailed Implementation

[0038] In this invention, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "planar direction," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention.

[0039] like Figures 1 to 6 As shown, an EGR cooling and transmission oil temperature control system includes an engine 03, a water pump 05, a thermostat 04, a radiator 06, an EGR cooler 07, and a transmission oil cooler 08. The water pump 05 is connected to the water jacket of the engine 03, the thermostat 04 is connected to both the water pump 05 and the engine 03, the EGR cooler 07 and the transmission oil cooler 08 are connected in parallel to the thermostat 04, one end of the radiator 06 is connected to the thermostat 04, and the other end of the radiator 06 is connected to the EGR cooler 07 and / or the transmission oil cooler 08.

[0040] To facilitate component arrangement and circulation pipeline implementation, thermostat 04 includes thermostat I 041 and thermostat II 042. The inlet of thermostat I 041 is connected to the outlet of water pump 05, and the outlet of thermostat I 041 is connected to the inlet of radiator 06, the inlet of EGR cooler 07, and the inlet of transmission oil cooler 08. The outlets of radiator 06, EGR cooler 07, and transmission oil cooler 08 are connected to the inlet of thermostat II 042, and the outlet of thermostat II 042 is connected to the water jacket of engine 03.

[0041] The control system also includes three-way valves I01 and II02. The inlet of the EGR cooler 07 is connected to the outlet of the thermostat I041 and the outlet of the radiator 06 via three-way valve I01; the inlet of the gearbox oil cooler 08 is connected to the outlet of the thermostat I041 and the outlet of the radiator 06 via three-way valve II02. Preferably, both three-way valves I01 and II02 are three-way solenoid valves.

[0042] Engine 03, water pump 05, thermostat I 041, three-way valve I 01, EGR cooler 07, and thermostat II 042 constitute the first circulation path. The circulation route is: Engine 03 → Water pump 05 → Thermostat I 041 → Three-way valve I 01 → EGR cooler 07 → Thermostat II 042 → Engine 03. During the engine warm-up phase, the first circulation path is used. Water in the engine water jacket flows out from the outlet of thermostat I 041 via water pump 05, is switched by three-way valve I 01, flows into the EGR cooler, and then flows back to the engine via thermostat II 042. In other words, water in the engine water jacket sequentially passes through water pump 05, thermostat I 041, three-way valve I 01, EGR cooler 07, and thermostat II 042 before returning to the engine water jacket.

[0043] Engine 03, water pump 05, thermostat I 041, radiator 06, three-way valve I 01, EGR cooler 07, and thermostat II 042 constitute the second circulation path. The circulation route is: Engine 03 → Water pump 05 → Thermostat I 041 → Radiator 06 → Three-way valve I 01 → EGR cooler 07 → Thermostat II 042 → Engine 03. After the engine warm-up phase, the second circulation path is activated. Water from the engine water jacket flows out of the outlet of thermostat I 041 via water pump 05, passes through the radiator, is switched by three-way valve I 01, flows into the EGR cooler, and then flows back to the engine via thermostat II 042. In other words, water from the engine water jacket sequentially passes through water pump 05, thermostat I 041, radiator 06, three-way valve I 01, EGR cooler 07, and thermostat II 042 before returning to the engine water jacket.

[0044] Engine 03, water pump 05, thermostat I 041, three-way valve II 02, transmission oil cooler 08, and thermostat II 042 constitute the third circulation path. The circulation path is: engine 03 → water pump 05 → thermostat I 041 → three-way valve II 02 → transmission oil cooler 08 → thermostat II 042 → engine 03. When the transmission oil temperature needs to be heated, the third circulation path mode is adopted. The hot water in the engine water jacket flows out from the outlet of thermostat I 041 through water pump 05, is switched by three-way valve II 02, flows into the transmission oil cooler, and then flows back to the engine through thermostat II 042. That is, the water in the engine water jacket passes through water pump 05, thermostat I 041, three-way valve II 02, transmission oil cooler 08, and thermostat II 042 in sequence and then returns to the engine water jacket, so that the high-temperature coolant flowing in the circuit can heat the transmission oil.

[0045] Engine 03, water pump 05, thermostat I 041, radiator 06, three-way valve II 02, transmission oil cooler 08, and thermostat II 042 constitute the fourth circulation path. The circulation path is: engine 03 → water pump 05 → thermostat I 041 → radiator 06 → three-way valve II 02 → transmission oil cooler 08 → thermostat II 042 → engine 03. When the transmission oil temperature needs to be heated, the fourth circulation path mode is adopted. The hot water in the engine water jacket flows out of the outlet of thermostat I 041 through water pump 05, passes through the radiator, is switched by three-way valve II 02, flows into the transmission oil cooler, and then flows back to the engine through thermostat II 042. That is, the water in the engine water jacket passes through water pump 05, thermostat I 041, radiator 06, three-way valve II 02, transmission oil cooler 08, and thermostat II 042 in sequence and then returns to the engine water jacket, so that the low-temperature coolant in the circuit cools the transmission oil.

[0046] Based on the aforementioned EGR cooling and transmission oil temperature control system, this invention also provides an EGR cooling and transmission oil temperature control method. The control method includes EGR cooling control and transmission oil temperature control. The EGR cooling control is as follows: when the engine coolant temperature T is less than a fixed value T1, the engine is in the warm-up stage, using the first circulation path; when the engine coolant temperature T is greater than the fixed value T1, the engine needs cooling, using the second circulation path. The transmission oil temperature control is as follows: when the transmission oil temperature K is less than a fixed value K1, the transmission oil needs heating, using the third circulation path; when the transmission oil temperature K is greater than the fixed value K1, the transmission oil needs cooling, using the fourth circulation path. The fixed value T1 is the temperature under optimal engine operating conditions; the fixed value K1 is the transmission oil temperature under optimal transmission operating conditions.

[0047] The control method specifically includes the following steps:

[0048] Step 100: Obtain the current engine coolant temperature T;

[0049] Step 110: Obtain the current transmission oil temperature K;

[0050] Step 120: Determine whether the current engine coolant temperature T is higher than the fixed value T1. If the determination result is positive, proceed to step 140. If the determination result is negative, proceed to step 150.

[0051] Step 130: Determine whether the current transmission oil temperature K is higher than the fixed value K1. If the determination result is positive, proceed to step 160. If the determination result is negative, proceed to step 170.

[0052] Step 140: By opening and closing the three-way valve I01, the second circulation loop is realized. The water in the engine 03 water jacket flows from the outlet of the thermostat I041 into the radiator 06 through the engine water pump, then flows to the three-way valve I01 and flows back to the thermostat II042 through the EGR cooler 07, and then flows back to the engine 03 circulation.

[0053] Step 150: By opening and closing the three-way valve I01, the first circulation loop is realized. The water in the engine 03 water jacket flows from the outlet of thermostat I041 to the three-way valve I01 via the engine water pump, flows back to thermostat II042 via EGR cooler 07, and then flows back to engine 03 circulation.

[0054] Step 160: By opening and closing the three-way valve II02, the fourth circulation loop can be realized. The water in the engine 03 water jacket flows from the outlet of the thermostat I041 into the radiator 06 through the engine water pump, then flows to the three-way valve II02 and then flows back to the thermostat II042 through the transmission oil cooler 08, and then flows back to the engine 03 circulation.

[0055] Step 170: By opening and closing the three-way valve II02, the third circulation loop is realized. The water in the engine 03 water jacket flows from the outlet of the thermostat I041 to the three-way valve I01 via the engine water pump, flows back to the thermostat II042 via the transmission oil cooler 08, and then flows back to the engine 03 circulation.

[0056] Based on the above control method, the current engine coolant temperature is obtained, and the current circulation mode is determined according to the current engine coolant temperature. During the engine warm-up phase, the first circulation path mode is adopted, allowing the coolant flowing from the engine thermostat outlet to flow into the EGR cooler and then back to the engine thermostat via a three-way solenoid valve. After the engine warm-up phase, the second circulation path mode is adopted, allowing the coolant flowing from the engine thermostat outlet to pass through the radiator, then flow into the EGR cooler via a three-way solenoid valve and then back to the engine thermostat.

[0057] The temperature of the coolant flowing from the engine outlet is relatively lower during engine warm-up than after warm-up. Therefore, during engine warm-up, the system switches to the first circulation water path mode. After warm-up, the relatively coolant flows to the EGR cooler via the second circulation water path, increasing the EGR gas density and thus improving the EGR rate.

[0058] According to the design method of the above invention, the current transmission oil temperature is obtained, and the current circulation mode is determined based on the current transmission oil temperature; when the transmission oil temperature needs to be heated, the third circulation path mode is adopted, and the three-way solenoid valve is used to switch so that the high-temperature coolant flowing in the circuit heats the transmission oil; when the transmission oil temperature needs to be cooled, the fourth circulation path mode is adopted, and the three-way solenoid valve is used to switch so that the low-temperature coolant cooled in the circuit cools the transmission oil.

[0059] Depending on the different transmission fluid temperature requirements, a three-way solenoid valve switches between heating and cooling mode circulation loops. In heating mode, the relatively high-temperature coolant heats the transmission fluid, rapidly increasing its temperature, reducing its viscosity, minimizing churning losses, reducing friction losses, improving transmission mechanical efficiency, and lowering overall vehicle fuel consumption. In cooling mode, the low-temperature coolant, cooled by the radiator, enters the transmission fluid cooler, rapidly cooling it and preventing high-temperature torque limiting due to excessively high transmission fluid temperature. This also prevents the wear and tear on clutch friction plates and brake pads, further extending the transmission's lifespan.

[0060] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the technical solution of the present invention, or the direct application of the concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. An EGR cooling and transmission oil temperature control system, characterized in that: The system includes an engine (03), a water pump (05), a thermostat (04), a radiator (06), an EGR cooler (07), and a transmission oil cooler (08). The water pump (05) is connected to the water jacket of the engine (03), the thermostat (04) is connected to the water pump (05) and the engine (03), the EGR cooler (07) and the transmission oil cooler (08) are connected in parallel to the thermostat (04), one end of the radiator (06) is connected to the thermostat (04), and one end of the radiator (06) is connected to the EGR cooler (07) and / or the transmission oil cooler (08). The thermostat (04) includes thermostat I (041) and thermostat II (042). The inlet of thermostat I (041) is connected to the outlet of water pump (05). The outlet of thermostat I (041) is connected to the inlet of radiator (06), the inlet of EGR cooler (07), and the inlet of gearbox oil cooler (08). The outlet of radiator (06), the outlet of EGR cooler (07), and the outlet of gearbox oil cooler (08) are connected to the inlet of thermostat II (042). The outlet of thermostat II (042) is connected to the water jacket of engine (03). The control system also includes a three-way valve I (01) and a three-way valve II (02). The inlet of the EGR cooler (07) is connected to the outlet of the thermostat I (041) and the outlet of the radiator (06) through the three-way valve I (01); the inlet of the gearbox oil cooler (08) is connected to the outlet of the thermostat I (041) and the outlet of the radiator (06) through the three-way valve II (02). The engine (03), water pump (05), thermostat I (041), three-way valve I (01), EGR cooler (07), and thermostat II (042) constitute the first circulation path; The engine (03), water pump (05), thermostat I (041), radiator (06), three-way valve I (01), EGR cooler (07), and thermostat II (042) constitute the second circulation path; The engine (03), water pump (05), thermostat I (041), three-way valve II (02), gearbox oil cooler (08), and thermostat II (042) constitute the third circulation path; The engine (03), water pump (05), thermostat I (041), radiator (06), three-way valve II (02), gearbox oil cooler (08), and thermostat II (042) constitute the fourth circulation path.

2. The EGR cooling and transmission oil temperature control system as described in claim 1, characterized in that: During the engine warm-up phase, the first circulation mode is adopted. Water in the engine water jacket flows out from the outlet of thermostat I (041) via water pump (05), and flows into the EGR cooler through the three-way valve I (01) and then flows back to the engine via thermostat II (042).

3. The EGR cooling and transmission oil temperature control system as described in claim 1, characterized in that: After the engine warm-up phase, the second circulation mode is adopted. The water in the engine water jacket flows out from the outlet of thermostat I (041) via water pump (05), passes through the radiator, is switched by three-way valve I (01), flows into the EGR cooler, and then flows back to the engine via thermostat II (042).

4. The EGR cooling and transmission oil temperature control system as described in claim 1, characterized in that: When the transmission oil temperature needs to be heated, the third circulation mode is adopted. The hot water in the engine water jacket flows out from the outlet of thermostat I (041) through the water pump (05), and flows into the transmission oil cooler through the three-way valve II (02) and then flows back to the engine through thermostat II (042).

5. The EGR cooling and transmission oil temperature control system as described in claim 1, characterized in that: When the transmission oil temperature needs to be heated, the fourth circulation mode is adopted. The hot water in the engine water jacket flows out from the outlet of thermostat I (041) through the water pump (05), passes through the radiator, and is switched by the three-way valve II (02) to flow into the transmission oil cooler and then flows back to the engine through thermostat II (042).

6. A method for EGR cooling and transmission oil temperature control, characterized in that: Based on the EGR cooling and transmission oil temperature control system as described in any one of claims 1 to 5, the control method includes EGR cooling control and transmission oil temperature control. The EGR cooling control is as follows: when the engine coolant temperature T is less than a fixed value T1, the engine is in the warm-up stage and the first circulation path is used; when the engine coolant temperature T is greater than the fixed value T1, the engine needs to be cooled and the second circulation path is used. The transmission oil temperature control is as follows: when the transmission oil temperature K is less than a fixed value K1, the transmission oil needs to be heated and the third circulation path is used; when the transmission oil temperature K is greater than the fixed value K1, the transmission oil needs to be cooled and the fourth circulation path is used.

7. The EGR cooling and transmission oil temperature control method as described in claim 6, characterized in that: The control method specifically includes the following steps: Step 100: Obtain the current engine coolant temperature T; Step 110: Obtain the current transmission oil temperature K; Step 120: Determine whether the current engine coolant temperature T is higher than the fixed value T1. If the determination result is positive, proceed to step 140. If the determination result is negative, proceed to step 150. Step 130: Determine whether the current transmission oil temperature K is higher than the fixed value K1. If the determination result is positive, proceed to step 160; if the determination result is negative, proceed to step 170. Step 140: By opening and closing the three-way valve I (01), the second circulation loop is realized. The water in the engine (03) water jacket flows from the outlet of the thermostat I (041) into the radiator (06) through the engine water pump, then flows to the three-way valve I (01) and flows back to the thermostat II (042) through the EGR cooler (07), and then flows back to the engine (03) for circulation. Step 150: By opening and closing the three-way valve I (01), the first circulation loop is realized. The water in the engine (03) water jacket flows from the outlet of thermostat I (041) to the three-way valve I (01) via the engine water pump, flows back to thermostat II (042) through the EGR cooler (07), and then flows back to the engine (03) for circulation. Step 160: By opening and closing the three-way valve II (02), the fourth circulation loop can be realized. The water in the engine (03) water jacket flows from the outlet of the thermostat I (041) into the radiator (06) through the engine water pump, then flows to the three-way valve II (02) and then flows back to the thermostat II (042) through the transmission oil cooler (08), and then flows back to the engine (03) for circulation. Step 170: By opening and closing the three-way valve II (02), the third circulation loop is realized. The water in the engine (03) water jacket flows from the outlet of the thermostat I (041) to the three-way valve I (01) via the engine water pump, flows back to the thermostat II (042) via the gearbox oil cooler (08), and then flows back to the engine (03) for circulation.

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