Engine cooling device

Abstract

To provide an engine cooling device that enables suppression of deterioration of fuel economy.SOLUTION: An engine cooling device includes: a block lower part that is a lower part of a cylinder block of an engine; a block upper part that is an upper part of the cylinder block; a cylinder head of the engine; an exhaust gas cooling part that cools exhaust gas of the engine; a radiator that radiates heat of cooling water; a first path that bypasses the radiator and causes the cooling water to circulate in the block lower part, the block upper part, the cylinder head and the exhaust gas cooling part; a second path that bypasses the block lower part and causes cooling water to circulate in the radiator, the block upper part, the cylinder head and the exhaust gas cooling part; and a flow rate control mechanism that when a temperature of the cooling water flowing in the first path is a warm-up completion temperature or higher, increases a flow rate of the cooling water flowing in the second path relative to a flow rate of the cooling water flowing in the first path compared to when the temperature of the cooling water is lower than the warm-up completion temperature.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an engine cooling device. [Background technology]

[0002] BACKGROUND ART An engine cooling device that cools an engine with cooling water is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-097991 Summary of the Invention [Problem to be solved by the invention]

[0004] If the temperature of the engine's cylinder block and cylinder head rises slowly before the warm-up is complete, the amount of unburned fuel increases, which may result in a decrease in fuel efficiency. Also, if the upper part of the engine's cylinder block, cylinder head, and exhaust cooling section rise too high in temperature after the warm-up is complete, knocking may occur more easily, which may result in a decrease in fuel efficiency.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an engine cooling device that suppresses a decrease in fuel efficiency. [Means for solving the problem]

[0006] The above object can be achieved by an engine cooling device comprising: a block lower portion that is the lower portion of a cylinder block of an engine; a block upper portion that is the upper portion of the cylinder block; a cylinder head of the engine; an exhaust cooling portion that cools exhaust gas from the engine; a radiator that dissipates heat from cooling water; a first path that bypasses the radiator and circulates cooling water to the block lower portion, the block upper portion, the cylinder head, and the exhaust cooling portion; a second path that bypasses the block lower portion and circulates cooling water to the radiator, the block upper portion, the cylinder head, and the exhaust cooling portion; and a flow control mechanism that, when the temperature of the cooling water flowing through the first path is equal to or higher than a warm-up completion temperature, increases the flow rate of cooling water flowing through the second path relative to the flow rate of cooling water flowing through the first path compared to when the temperature of the cooling water is below the warm-up completion temperature.

[0007] The engine may further include an EGR cooler that cools EGR gas of the engine, and each of the first and second paths may further circulate cooling water through the EGR cooler.

[0008] The first path may allow the cooling water that has passed through the exhaust cooling portion and the cylinder head to flow into the EGR cooler.

[0009] The second path may include a path that circulates cooling water from the radiator to the upper part of the block and the EGR cooler, and a path that circulates cooling water from the radiator to the cylinder head and the exhaust cooling portion.

[0010] The flow rate control mechanism may include a first water pump disposed on the first path and a second water pump disposed on the second path. [Effects of the Invention]

[0011] An engine cooling device can be provided that suppresses a decrease in fuel efficiency. [Brief explanation of the drawings]

[0012] [Figure 1]1 is an explanatory diagram of an engine cooling device according to a first embodiment. [Figure 2] 1 is an explanatory diagram of an engine cooling device according to a first embodiment. [Figure 3] 1 is an explanatory diagram of an engine cooling device according to a first embodiment. [Figure 4] FIG. 6 is an explanatory diagram of an engine cooling device according to a second embodiment. [Figure 5] FIG. 6 is an explanatory diagram of an engine cooling device according to a second embodiment. [Figure 6] FIG. 10 is an explanatory diagram of an engine cooling device according to a third embodiment. [Figure 7] FIG. 10 is an explanatory diagram of an engine cooling device according to a third embodiment. [Figure 8] FIG. 10 is an explanatory diagram of an engine cooling device according to a fourth embodiment. [Figure 9] FIG. 10 is an explanatory diagram of an engine cooling device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] [First Example] 1 to 3 are explanatory diagrams of an engine cooling device 1 of a first embodiment. The engine cooling device 1 is mounted on, for example, a vehicle. The engine cooling device 1 includes a block lower part 11, a block upper part 12, a cylinder head 13, an exhaust cooling section 14, an EGR cooler 21, an EGR valve 22, a throttle body 23, a radiator 30, a heater core 31, an on-off valve 32, an oil cooler 33, water pumps P1 and P2, temperature sensors S1 and S2, and an ECU (Electronic Control Unit) 100. The block lower part 11 is the lower part of the cylinder block of the engine. The block upper part 12 is the upper part of the cylinder block of the engine. A jacket through which cooling water flows in the block lower part 11 and a jacket through which cooling water flows in the block upper part 12 are separated from each other. The cylinder head 13 is fixed to the top of the block upper part 12. The exhaust cooling section 14 is provided on the outer periphery of an exhaust manifold connected to the cylinder head 13. As coolant flows through the exhaust cooling section 14, heat exchange occurs between the coolant and exhaust gas, cooling the exhaust gas. The EGR cooler 21 is provided on the outer periphery of an EGR (Exhaust Gas Recirculation) pipe. As coolant flows through the EGR cooler 21, heat exchange occurs between the coolant and EGR gas, cooling the EGR gas. The EGR cooler 21 is connected to the block upper section 12. The EGR valve 22 adjusts the flow rate of EGR gas. The throttle body 23 is the main body of the intake valve that adjusts the amount of intake air. The radiator 30 promotes heat exchange between outside air and coolant to cool the coolant. The heater core 31 promotes heat exchange between the air in the vehicle's cabin and the coolant to heat the cabin. The on-off valve 32 allows or blocks the flow of coolant into the heater core 31. The oil cooler 33 cools engine oil through heat exchange between the coolant and engine oil.

[0014] The ECU 100 is an electronic control unit that includes a processing circuit that performs various arithmetic operations related to vehicle driving control and a memory that stores control programs and data. The ECU 100 acquires the coolant temperature based on temperature sensors S1 and S2. The ECU 100 controls water pumps P1 and P2 and an on-off valve 32. The water pumps P1 and P2 are electrically operated. The water pumps P1 and P2 are an example of a flow control mechanism. The water pump P1 is an example of a first water pump. The water pump P2 is an example of a second water pump.

[0015] The passage 61 is connected to the block lower portion 11. The water pump P1 is provided on the passage 61. The water pump P1 pumps cooling water to the block lower portion 11 via the passage 61. The passage 62 connects the block lower portion 11 to the exhaust cooling section 14. The passage 63 connects the block lower portion 11 to the exhaust cooling section 14 via the oil cooler 33. The passage 64 connects the exhaust cooling section 14 to the cylinder head 13. The passage 65 connects the cylinder head 13 to the block upper portion 12. The passage 66 connects the EGR cooler 21 to the passage 61 via the EGR valve 22 and the throttle body 23. The passage 67 branches off from the passage 66 between the EGR cooler 21 and the EGR valve 22 and is connected to the passage 61. The passage 71 connects the exhaust cooling section 14 to the radiator 30. Path 68 branches off from path 71 and is connected to EGR cooler 21. Path 72 connects radiator 30 and block upper portion 12. Water pump P2 is provided on path 72. Water pump P2 pumps coolant to block upper portion 12 via path 72. Temperature sensor S2 is provided on path 72.

[0016] The path 81 connects the exhaust cooling section 14 and the path 61. The path 81 is provided with an on-off valve 32 and a heater core 31. The temperature sensor S1 is provided on the path 81 between the exhaust cooling section 14 and the on-off valve 32. More specifically, the temperature sensor S1 is provided on a path (not shown) that connects the path 81 and the path 61, bypassing the on-off valve 32 and the heater core 31. Therefore, the temperature sensor S1 detects the temperature of the coolant from the exhaust cooling section 14 even when the on-off valve 32 is closed. Therefore, the temperature sensor S1 detects the temperature of the coolant circulating through a first path, which will be described in detail later.

[0017] FIG. 1 shows the circulation state of the coolant when the coolant temperature detected by the temperature sensor S1 is below the warm-up completion temperature. Before the warm-up completion, the ECU 100 drives the water pump P1 and stops the water pump P2. In FIG. 1, the flow rate of the coolant is high through the path indicated by the solid line, and low through the path indicated by the dotted line. In this state, the coolant flows into the lower block 11 via path 61. A portion of the coolant that flows into the lower block 11 flows into the exhaust cooling section 14 via path 62. A portion of the coolant that flows into the lower block 11 flows into the oil cooler 33 and the exhaust cooling section 14 via path 63. A portion of the coolant that flows into the exhaust cooling section 14 flows into the cylinder head 13, the upper block 12, and the EGR cooler 21 via paths 64 and 65. A portion of the coolant that flows into the exhaust cooling section 14 flows into the EGR cooler 21 via a portion of path 71 and path 68. A portion of the cooling water that flows into the EGR cooler 21 flows through the EGR valve 22 and the throttle body 23 via a path 66 and then flows into the path 61. A portion of the cooling water that flows into the EGR cooler 21 flows into the path 61 via a path 67. Parts of the paths 61, 62, 63, 64, 65, 66, 67, 68, and 71 are examples of first paths.

[0018] In the exhaust cooling section 14, the coolant is heated by the exhaust gas. This high-temperature coolant flows into the cylinder head 13, the block upper section 12, and the block lower section 11, accelerating the temperature increase therein. This suppresses an increase in unburned fuel in the combustion chamber, and suppresses a decrease in fuel efficiency. In addition, the coolant, which has been heated after passing through the exhaust cooling section 14, the cylinder head 13, and the block upper section 12, flows into the EGR cooler 21. This accelerates the temperature increase in the EGR cooler 21, and suppresses the generation of condensation in the EGR pipe caused by low-temperature coolant flowing into the EGR cooler 21.

[0019] Furthermore, because water pump P2 is stopped, the flow rate of coolant flowing into radiator 30 is reduced, accelerating the rise in the temperature of the coolant. Also, because coolant flows into EGR valve 22, excessive temperature rise of EGR valve 22 is suppressed. Because coolant flows into throttle body 23, freezing of throttle body 23 is suppressed.

[0020] FIG. 2 shows the circulation state of the coolant when the coolant temperature detected by the temperature sensor S1 is equal to or higher than the warm-up completion temperature. After the warm-up is completed, the ECU 100 drives the water pumps P1 and P2. In other words, in FIG. 2, the flow rate of the coolant from the water pump P2 is greater than the flow rate of the coolant from the water pump P1 compared to that in FIG. 1. Because the water pump P2 is driven, some of the coolant that flows into the exhaust cooling section 14 flows into the radiator 30 via path 71. The coolant is cooled in the radiator 30. The coolant that flows into the radiator 30 flows into the block upper part 12 via path 72. This prevents the block upper part 12 from overheating. The coolant that flows into the radiator 30 flows back into the radiator 30 via paths 72, 66, 67, 61, 62, 63, and 71. Therefore, the routes 72, 66, 67, 61, 62, 63, and 71 are examples of the second route. In this way, a part of the first route and a part of the second route overlap.

[0021] Furthermore, the cooling water that flows into the radiator 30 does not flow into the lower block portion 11. This prevents the temperature of the lower block portion 11 from decreasing, thereby preventing an increase in unburned fuel in the combustion chamber and reducing a decrease in fuel efficiency. Furthermore, a portion of the cooling water cooled by the radiator 30 flows into the EGR cooler 21, EGR valve 22, and throttle body 23 via the upper block portion 12. The flow of cooling water through the EGR cooler 21 and the EGR valve 22 promotes cooling of the EGR gas and reduces a decrease in fuel efficiency.

[0022] When there is a heating request, the ECU 100 opens the on-off valve 32 as shown in Fig. 2. As a result, a portion of the coolant that has flowed into the exhaust cooling section 14 flows into the heater core 31 via a path 81. Heat is exchanged between the coolant and the air in the vehicle cabin in the heater core 31, and the vehicle cabin is heated. The path 81 is an example of a third path. Note that even when there is a heating request before the warm-up is completed as shown in Fig. 1, the vehicle cabin is heated by opening the on-off valve 32.

[0023] FIG. 3 shows the circulation state of the coolant when the coolant temperature detected by the temperature sensor S1 is equal to or higher than the warm-up completion temperature. Here, FIG. 3 shows a case where the coolant temperature detected by the temperature sensor S1 is higher than that shown in FIG. 2. In FIG. 3, the water pumps P1 and P2 are driven as in FIG. 2, but the flow rate of the coolant from the water pump P2 is greater than that from the water pump P1 in FIG. 2. Therefore, in FIG. 3, the coolant that passes through the radiator 30 and flows into the block upper portion 12 flows into the cylinder head 13 via path 65. The coolant that flows into the cylinder head 13 flows into the exhaust cooling section 14 via path 64. This prevents excessive temperature rise in the block upper portion 12, the cylinder head 13, and the exhaust cooling section 14. For example, knocking can be suppressed, and a decrease in fuel efficiency can be suppressed. In this case, paths 64 and 65 are also included in the second path.

[0024] Furthermore, a portion of the cooling water cooled by the radiator 30 flows into the EGR cooler 21, the EGR valve 22, and the throttle body 23 via the block upper portion 12. This promotes the cooling of the EGR gas. Furthermore, a portion of the cooling water that flows into the exhaust cooling section 14 from the block lower portion 11, the cylinder head 13, and the oil cooler 33 flows into the radiator 30 via a path 71. This promotes the cooling of the cooling water.

[0025] [Second Example] 4 and 5 are explanatory diagrams of an engine cooling device 1a of a second embodiment. In FIGS. 4 and 5, the block lower part 11 and the block upper part 12 are shown separately for ease of understanding. A path 69 connects the EGR cooler 21 and the block upper part 12. A path 66 connects to a path 68. Specifically, the temperature sensor S1 is provided on a path (not shown) that bypasses the on-off valve 32 and the heater core 31 and connects the path 81 and the path 66. Therefore, the temperature sensor S1 can detect the temperature of the coolant from the exhaust cooling section 14 even when the on-off valve 32 is closed.

[0026] FIG. 4 shows the circulation state of the coolant when the coolant temperature detected by the temperature sensor S1 is below the warm-up completion temperature. Before the warm-up completion, the ECU 100 drives the water pump P1 and stops the water pump P2. Therefore, the coolant flows into the lower block 11 via path 61. A portion of the coolant that flows into the lower block 11 flows into the exhaust cooling section 14 via path 62. A portion of the coolant that flows into the lower block 11 flows into the oil cooler 33 via path 63. The coolant that flows into the oil cooler 33 flows into the exhaust cooling section 14. A portion of the coolant that flows into the exhaust cooling section 14 flows into the EGR cooler 21 via part of path 71 and path 68. The coolant that flows into the EGR cooler 21 flows into the upper block 12 via path 69. The coolant that flows into the upper block 12 flows into the cylinder head 13 via path 65. The cooling water that flows into the cylinder head 13 flows into the exhaust cooling section 14 via path 64. Furthermore, a portion of the cooling water that flows into the exhaust cooling section 14 flows into the EGR valve 22 and the throttle body 23 via part of path 71, part of path 68, and path 66. The cooling water that flows into the EGR valve 22 and the throttle body 23 flows into the block lower portion 11 via path 66 and path 61. Parts of paths 61, 62, 63, 64, 65, 66, 67, 68, 69, and 71 are examples of first paths.

[0027] The cooling water heated to a high temperature in the exhaust cooling section 14 flows into the block upper section 12, the cylinder head 13, and the block lower section 11. This promotes a temperature increase in the block upper section 12, the cylinder head 13, and the block lower section 11. In addition, the cooling water heated to a high temperature after flowing through the cylinder head 13 and the exhaust cooling section 14 flows into the EGR cooler 21. This promotes a temperature increase in the EGR cooler 21.

[0028] Note that, assuming a coolant pressure loss R1 in the cylinder head 13, a coolant pressure loss R2 in the exhaust cooling section 14, a coolant pressure loss R3 in the block upper part 12, and a coolant pressure loss R4 in the EGR cooler 21, and likening this to a Wheatstone bridge circuit, the closer (R2·R3−R1·R4) is to 0, the more the flow rate of coolant flowing through the radiator 30 when the water pump P2 is stopped can be reduced. Therefore, by adjusting each of the above pressure losses and reducing the flow rate of coolant flowing through the radiator 30 when the water pump P2 is stopped, the temperature rise of the coolant and the temperature rise of the block lower part 11, block upper part 12, cylinder head 13, and EGR cooler 21 are promoted.

[0029] FIG. 5 shows the circulation state of the coolant when the coolant temperature detected by the temperature sensor S1 is equal to or higher than the warm-up completion temperature. After the warm-up is complete, the ECU 100 drives the water pumps P1 and P2. A portion of the coolant discharged from the exhaust cooling section 14 flows into the radiator 30 via path 71. The coolant that flows into the radiator 30 flows into the block upper section 12. A portion of the coolant that flows into the block upper section 12 flows into the cylinder head 13 and the exhaust cooling section 14 via paths 65 and 64. In this way, a portion of the coolant that passes through the radiator 30 flows into the block upper section 12, the cylinder head 13, and the exhaust cooling section 14, thereby preventing these components from overheating. In addition, a portion of the coolant that flows into the block upper section 12 flows into the EGR cooler 21 via path 69. A portion of the coolant that flows into the EGR cooler 21 flows into the EGR valve 22 and the throttle body 23 via path 66. This also prevents a decrease in fuel efficiency, etc. The paths 64, 65, 68, 69, 71, and 72 are examples of the second paths. When there is a request for heating, the ECU 100 opens the on-off valve 32 as shown in Fig. 5. This causes the interior of the vehicle to be heated.

[0030] [Third Example] 6 and 7 are explanatory diagrams of an engine cooling device 1b of a third embodiment. Path 61a communicates with path 72. Specifically, a portion of path 61a downstream of water pump P1 communicates with a portion of path 72 downstream of water pump P2. Water pump P1 is provided on path 61a. Path 61b communicates between the block lower portion 11 and path 61a. Specifically, path 61b communicates with a portion of path 61a upstream of water pump P1 and a portion of path 61a upstream of water pump P1. Path 61b is provided with an orifice 61c for reducing the flow rate of the cooling water.

[0031] FIG. 6 shows the circulation state of the coolant when the coolant temperature detected by the temperature sensor S1 is lower than the warm-up completion temperature. Before the warm-up completion, the ECU 100 drives the water pump P1, and the water pump P2 is stopped. The coolant flows into the block upper portion 12 via path 61a and a portion of path 72. A portion of the coolant that flows into the block upper portion 12 flows into the EGR cooler 21. A portion of the coolant that flows into the EGR cooler 21 flows into the EGR valve 22 and the throttle body 23 via path 66 and then flows into path 61a. A portion of the coolant that flows into the EGR cooler 21 flows into path 61a via path 67. A portion of the coolant that flows into the block upper portion 12 flows into the cylinder head 13 and the exhaust cooling section 14 via paths 65 and 64. Paths 61a, 61b, 62, 63, 64, 65, 66, 67, and portions of 72 are examples of first paths.

[0032] The cooling water that flows into the exhaust cooling section 14 flows into the lower block section 11 via paths 62 and 63. The cooling water that flows into the lower block section 11 flows into path 61a via path 61b. The cooling water that has been heated in the exhaust cooling section 14 flows into the lower block section 11, the upper block section 12, and the cylinder head 13. This promotes a rise in the temperature of the lower block section 11, the upper block section 12, and the cylinder head 13. In addition, an orifice 61c is provided in path 61b. This suppresses the flow rate of the cooling water passing through the lower block section 11, promoting a rise in the temperature of the lower block section 11.

[0033] FIG. 7 shows the circulation state of the coolant when the coolant temperature detected by the temperature sensor S1 is equal to or higher than the warm-up completion temperature. After the warm-up is complete, the ECU 100 drives the water pumps P1 and P2. A portion of the coolant that flows into the exhaust cooling section 14 flows into the radiator 30 via path 71. The coolant that flows into the radiator 30 flows into the block upper section 12 via path 72. The coolant that passes through the radiator 30 and flows into the block upper section 12 flows through the cylinder head 13 and the exhaust cooling section 14. This prevents the block upper section 12, the cylinder head 13, and the exhaust cooling section 14 from overheating. Furthermore, the coolant that flows into the radiator 30 does not flow into the block lower section 11. This prevents the temperature of the block lower section 11 from dropping, thereby preventing a decrease in fuel efficiency. Paths 64, 65, 71, and 72 are examples of second paths.

[0034] The flow rate of the coolant flowing through path 72 relative to the flow rate of the coolant flowing through path 61a may be increased or decreased by adjusting the driving power of water pumps P1 and P2. For example, when the temperature detected by temperature sensor S1 is equal to or higher than the warm-up completion temperature and also equal to or higher than the knocking temperature, the flow rate of the coolant flowing through path 72 relative to the flow rate of the coolant flowing through path 61a may be increased compared to when the temperature is equal to or higher than the warm-up completion temperature but lower than the knocking temperature. This ensures that the coolant, which has passed through the radiator 30 and has become cold, flows to the block upper portion 12, the cylinder head 13, and the exhaust cooling portion 14, thereby suppressing the occurrence of knocking.

[0035] [Fourth Example] 8 and 9 are explanatory diagrams of an engine cooling device 1c of a fourth embodiment. A thermostat 34 is provided in the passage 72. A passage 61d is connected to the thermostat 34. When the temperature of the coolant in the thermostat 34 is lower than the warm-up completion temperature, the coolant flows into the thermostat 34 via the passage 61d. When the temperature of the coolant in the thermostat 34 is equal to or higher than the warm-up completion temperature, the coolant flows into the thermostat 34 via the passage 61d and also flows into the thermostat 34 via the passage 72. The coolant that flows into the thermostat 34 flows into the block upper portion 12 via the passage 72. A water pump P3 is provided on the passage 72 downstream of the thermostat 34. The thermostat 34 and the water pump P3 are examples of a flow control mechanism. In the fourth embodiment, a single water pump P3 is provided, and therefore power consumption is reduced compared to the first to third embodiments described above, in which two water pumps P1 and P2 are provided.

[0036] FIG. 8 shows the circulation state of the coolant when the coolant temperature detected by the temperature sensor S1 is below the warm-up completion temperature. Before the warm-up completion, the ECU 100 drives the water pump P3, and the thermostat 34 closes the path 72. The coolant flowing through the path 61d flows into the thermostat 34 and then flows into the upper block 12 via a portion of the path 72. A portion of the coolant that flows into the upper block 12 flows into the cylinder head 13, the exhaust cooling section 14, and the lower block 11. That is, the coolant that has become hot in the exhaust cooling section 14 flows into the lower block 11, the upper block 12, and the cylinder head 13. In this way, the temperature rise of the lower block 11, the upper block 12, and the cylinder head 13 is promoted. The paths 61d, 61b, 62, 63, 64, 65, 66, 67, and a portion of the path 72 are examples of the first path.

[0037] 9 shows the circulation state of the coolant when the coolant temperature detected by the temperature sensor S1 is equal to or higher than the warm-up completion temperature. After the warm-up is completed, the ECU 100 drives the water pump P3, and the thermostat 34 opens the path 72. This allows the coolant that has passed through the radiator 30 to flow into the block upper part 12, the cylinder head 13, and the exhaust cooling section 14. This prevents the block upper part 12, the cylinder head 13, and the exhaust cooling section 14 from overheating. The paths 64, 65, 71, and 72 are examples of the second path.

[0038] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0039] 1a, 1b, 1c Engine cooling system 11 Block Lower 12 Block Top 13 Cylinder head 14 Exhaust cooling section 21 EGR cooler 30 Radiator 31 Heater core 32 On-off valve P1 Water pump (flow control mechanism, first water pump) P2 Water pump (flow control mechanism, second water pump)

Claims

1. The lower part of the engine cylinder block, a block upper portion that is an upper portion of the cylinder block; a cylinder head of the engine; an exhaust cooling unit that cools exhaust gas from the engine; a radiator that dissipates heat from the cooling water; a first path that bypasses the radiator and circulates cooling water through the block lower portion, the block upper portion, the cylinder head, and the exhaust cooling portion; a second path that bypasses the lower part of the block and circulates cooling water to the radiator, the upper part of the block, the cylinder head, and the exhaust cooling section; an engine cooling device comprising: a flow control mechanism that, when the temperature of the cooling water flowing through the first path is equal to or higher than a warm-up completion temperature, increases the flow rate of the cooling water flowing through the second path relative to the flow rate of the cooling water flowing through the first path compared to when the temperature of the cooling water is lower than the warm-up completion temperature.

2. an EGR cooler that cools EGR gas of the engine; 2. The engine cooling system of claim 1, wherein each of the first and second paths further circulates cooling water through the EGR cooler.

3. The engine cooling device according to claim 2 , wherein the first path allows the cooling water that has passed through the exhaust cooling portion and the cylinder head to flow into the EGR cooler.

4. 4. The engine cooling device of claim 3, wherein the second path includes a path for circulating cooling water from the radiator to the upper part of the block and the EGR cooler, and a path for circulating cooling water from the radiator to the cylinder head and the exhaust cooling portion.

5. 5. The engine cooling system according to claim 4, wherein the flow rate control mechanism includes a first water pump disposed on the first path and a second water pump disposed on the second path.

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