JP5083277B2 - Cooling device for internal combustion engine - Google Patents

Description

  The present invention relates to a cooling device for an internal combustion engine.

The water-cooled internal combustion engine has a cooling water circulation passage inside thereof, and the cooling water in the circulation passage is circulated to the radiator side by the operation of the water pump to cool the cooling water, and the cooled cooling water is again returned to the internal combustion engine. By circulating to the side, cooling of the internal combustion engine is executed (for example, Patent Document 1). As the water pump, a mechanical type that operates by synchronizing with the rotation of the internal combustion engine and an electric type that operates by an electric motor or the like are widely used.
When the operation of the water pump is stopped due to a failure or the like, the cooling capacity of the internal combustion engine is significantly reduced because the cooling water is not circulated. Therefore, there is a problem that the internal combustion engine may be overheated and damaged.

  In order to solve such a problem, the failure of the electric water pump is detected, and when the failure is detected, the engine control parameter is changed and the fail safe operation is executed to prevent the engine from being damaged. Techniques are described in Patent Documents 2 and 3.

Further, as a control device for an internal combustion engine, exhaust gas recirculation (Exhaust Gas Recirculation), which can improve fuel efficiency by suppressing a part of the exhaust gas to the intake side or suppress the amount of nitrogen oxide (NOx) generated, is described below. , Apparatus abbreviated as EGR) is widely applied. The EGR device includes an EGR cooler in which a part of the cooling water of the internal combustion engine circulates, and cools the EGR gas that is recirculated to the intake side to an appropriate temperature.
In this case, if the amount of cooling water circulating through the EGR cooler is insufficient, the cooling water in the EGR cooler may boil when the amount of EGR gas recirculated with the increase in the amount of NOx in the exhaust gas increases. When the cooling water boils, the pressure in the EGR cooler rises greatly, and there is a problem that the EGR device and the cooling system may break down or be damaged.

  In order to solve such problems, a cooling line for flowing the coolant cooled by the radiator to the engine body, a return line for flowing the coolant heated by the engine body to the radiator, and supplying the coolant to the EGR cooler And an EGR line that branches from the cooling line and merges with the return line, and distributes the coolant to the flow path that is configured from the branch position of the cooling line to the merge position of the return line via the engine body. Patent Document 4 discloses a technique for preventing the cooling liquid in the EGR cooler from boiling by forming a throttle portion to be suppressed and increasing the amount of water supplied to the EGR cooler.

Japanese Utility Model Publication No. 06-037523 JP 2000-303839 A JP 2008-121656 A JP 2008-051010 A

In recent years, control for temporarily stopping the circulation of cooling water by stopping the operation of the water pump during the warm-up operation of the internal combustion engine has been widely performed for the purpose of greatly improving the warm-up performance. When this control is executed, in an internal combustion engine equipped with an EGR device, the circulation of the cooling water in the EGR cooler is also stopped. For this reason, if the operation of the water pump is stopped, the high temperature EGR gas is recirculated, whereby the cooling water in the EGR cooler may boil and the EGR device or the cooling system may break down or be damaged.
However, in the techniques of Patent Documents 2 to 4, since it is difficult to circulate the cooling water in the EGR cooler, it is not possible to appropriately suppress the boiling of the cooling water in the EGR cooler. There is.

  In the techniques of Patent Documents 2 to 4, it is difficult to circulate the cooling water in the internal combustion engine or the EGR cooler when the operation of the water pump is stopped due to trouble or failure. Therefore, there is a problem that the internal combustion engine and the EGR device cannot be appropriately suppressed from being overheated and damaged.

  The present invention has been made in view of this point, and an object of the present invention is to provide a cooling device for an internal combustion engine that can ensure the circulation of the refrigerant even when the pump is stopped.

In order to achieve the above object, a cooling device for an internal combustion engine according to the present invention is a cooling device for an internal combustion engine including an EGR cooler for cooling EGR gas of the internal combustion engine. Provided in the first flow path, the second flow path for circulating the refrigerant circulated through the internal combustion engine toward the radiator, and the first flow path when the internal combustion engine is at a first temperature or higher. A refrigerant pump that circulates the refrigerant by operating, and is provided in the first flow path between the radiator and the refrigerant pump, and opens when the internal combustion engine is at a second temperature or higher. A first thermostat that allows the refrigerant to flow through one flow path, and the second flow path between the internal combustion engine and the radiator, and opens when the internal combustion engine is at or above a third temperature; The second flow path A second thermostat which allows refrigerant to flow, joins the downstream side of the second thermostat in the second flow path via the EGR cooler branch from the first flow path on the outlet side of the refrigerant pump A part of the refrigerant that circulates the EGR cooler, and a branch from the first passage between the radiator and the first thermostat, and the first thermostat and the refrigerant pump A bypass flow path that merges with the first flow path in between and causes the refrigerant to flow through the first thermostat (Claim 1).
By adopting such a configuration, the refrigerant in the internal combustion engine or the EGR cooler can be circulated by natural convection even when the pump for circulating the refrigerant is stopped.

In particular, the internal combustion engine cooling apparatus according to the present invention is characterized in that the first flow path is provided below the EGR cooler, and the second flow path is provided above the EGR cooler. (Claim 2).
By adopting such a configuration, a refrigerant flow is generated by natural convection, so that the refrigerant in the internal combustion engine or the EGR cooler is circulated even when the pump for circulating the refrigerant is stopped. Can do.

In the cooling device for an internal combustion engine of the present invention, the bypass passage allows the refrigerant to flow only when the refrigerant pump is not operating (Claim 3).
With such a configuration, when the pump for circulating the refrigerant is operating, the refrigerant cooled by the radiator can be circulated to the internal combustion engine side via the main thermostat. Therefore, it can suppress that the temperature control of a refrigerant | coolant becomes impossible.

In the cooling apparatus for an internal combustion engine according to the present invention, the second thermostat opens at a lower temperature than the first thermostat (Claim 4).
By setting it as such a structure, it can suppress that a 2nd thermostat prevents the temperature control of the refrigerant | coolant by a 1st thermostat.

Furthermore, the internal combustion engine cooling device of the present invention is provided in the third flow path between the EGR cooler and the second flow path, and opens when the EGR cooler is at a predetermined temperature or higher. A third thermostat for communicating the third flow path may be provided, and the third thermostat may be opened at a lower temperature than the second thermostat (Claim 5).
By setting it as such a structure, the quantity of the refrigerant | coolant which circulates through an EGR cooler can be adjusted according to the warming-up state of an internal combustion engine. Therefore, since it is possible to adjust the cooling capacity of the EGR cooler according to the warm-up state, it is possible to recirculate EGR gas having an appropriate temperature to the intake side.

The cooling apparatus for an internal combustion engine according to the present invention further includes a radiator cooling means for cooling the radiator when the internal combustion engine is at or above a fourth temperature, and the radiator cooling means is configured such that the internal combustion engine is less than a fourth temperature. The radiator may be cooled when the temperature of the EGR cooler is equal to or higher than a first threshold value (Claim 6).
With such a configuration, when the temperature of the EGR cooler is equal to or higher than the first threshold value, it is possible to improve the cooling capacity of the radiator and appropriately cool the refrigerant circulating in the EGR cooler. Therefore, it is possible to improve the warm-up property of the internal combustion engine while suppressing the decrease in the cooling capacity of the EGR cooler.

  According to the cooling device for an internal combustion engine of the present invention, since the refrigerant flow is generated by natural convection, the refrigerant in the internal combustion engine or the EGR cooler is removed even when the pump for circulating the refrigerant is stopped. It can be circulated. Therefore, it is possible to ensure the circulation of the refrigerant even when the pump is stopped.

It is the block diagram which showed schematic structure of the engine cooling system of an Example. The flow of cooling water at each temperature is shown. An example of the relationship between the cooling water temperature and the operation area of each component is shown. The control example of the EGR gas recirculation amount based on the cooling water temperature is shown. It is a flowchart which shows an example of a process of engine ECU. It is a flowchart which shows an example of a process of engine ECU. An example of a Qw map is shown. It is a flowchart which shows an example of a process of engine ECU. It is a flowchart which shows an example of a process of engine ECU. It is the block diagram which showed schematic structure of the engine cooling system of an Example. An example of the relationship between the cooling water temperature and the operation area of each component is shown. It is a flowchart which shows an example of a process of engine ECU. The flow of cooling water at each temperature is shown.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a schematic configuration of an engine cooling system 1 incorporating a cooling device for an internal combustion engine of the present invention. FIG. 1 shows only the configuration of one cylinder of the engine.

  An engine cooling system 1 shown in FIG. 1 includes an engine 100 that is a power source, and includes a radiator 11 that cools the engine 100 and a radiator fan 12 that cools the radiator 11. The engine cooling system 1 also includes an ECU (Electronic Control Unit) 10 that comprehensively controls the operation of the engine cooling system 1. The engine cooling system 1 includes an EGR cooler 14 that cools the exhaust gas introduction passage 13 and adjusts the temperature of the EGR gas that passes through the exhaust gas introduction passage 13 and is returned to the intake side. The engine cooling system 1 further includes a first flow path 21 and a second flow path 22 through which the refrigerant circulating through the radiator 11 and the engine 100 flows, and a third flow path 23 through which the refrigerant circulating through the EGR cooler 14 flows. ing. The engine cooling system 1 also includes a water pump 24 that circulates the refrigerant, a main thermostat 25 that controls the communication of the first flow path 21, and a sub thermostat 26 that controls the communication of the second flow path 22. The engine cooling system 1 includes a bypass passage 27 that branches from the first passage 21 and bypasses the main thermostat 25.

The engine 100 is a multi-cylinder engine mounted on a vehicle, and each cylinder includes a piston that constitutes a combustion chamber. The piston of each combustion chamber is connected to a crankshaft as an output shaft member via a connecting rod.
The mixed gas flowing into the combustion chamber from the intake port is compressed in the combustion chamber by the upward movement of the piston. The ECU 10 determines the ignition timing based on the position of the piston from the crank angle sensor and the cam shaft rotation phase information from the intake cam angle sensor, and sends a signal to the igniter. The igniter energizes the spark plug with the electric power from the battery at the instructed ignition timing according to the signal from the ECU 10. The spark plug is ignited by electric power from the battery, ignites the compressed mixed gas, expands in the combustion chamber, and lowers the piston. The descending motion is changed to the shaft rotation of the crankshaft through the connecting rod, whereby the engine 100 obtains power.

A water jacket is provided around the combustion chamber of the engine 100, and a coolant (cooling water) for cooling the combustion chamber and the like circulates inside the water jacket. As the cooling water in this embodiment, a general LLC (Long Life Coolant) made of an ethylene glycol aqueous solution is used, but other refrigerants may be used.
The water jacket is provided with a water temperature sensor 31 for measuring the temperature of the cooling water, and the detection result of the cooling water temperature inside the water jacket is transmitted to the ECU 10. ECU 10 recognizes the coolant temperature detected by water temperature sensor 31 as the temperature of engine 100. In this case, the water temperature sensor 31 is preferably provided at a position where the temperature of the relatively high-temperature cooling water inside the engine 100 can be detected. For example, near the outlet of the cooling water (near the connection with the second flow path 22) ).

The exhaust gas introduction passage 13 is branched from the exhaust passage on the upstream side of the purification catalyst and merges with the intake passage via the EGR cooler 14 to recirculate a part of the exhaust gas after combustion to the intake side. The exhaust gas branched into the exhaust gas introduction passage 13 proceeds to the intake passage while the flow rate is adjusted by an EGR valve (not shown), is mixed with the fuel injected into the intake port together with the intake air, and is supplied to the combustion chamber. The The EGR valve adjusts the amount of exhaust gas recirculation supplied to the intake passage to an appropriate amount by adjusting the valve opening according to a command from the ECU 10. In this manner, by supplying an appropriate amount of EGR gas according to the operating state to the intake passage, the combustion temperature of the engine 100 can be lowered and the NOx emission amount can be reduced. The branch portion between the exhaust passage and the exhaust gas introduction passage 13 may be provided on the downstream side of the purification catalyst.
The exhaust gas introduction passage 13 includes a bypass passage (not shown) that bypasses the EGR cooler 14. The bypass passage causes the EGR gas to flow back to the intake side without passing through the EGR cooler 14 by circulating the EGR gas when the temperature of the EGR gas to be refluxed is low. As a result, the EGR gas can be prevented from lowering in temperature more than necessary, so that the combustion of the engine 100 can be prevented from deteriorating.

The EGR cooler 14 has cooling water circulating therein, and adjusts the flow rate and flow rate of the circulating cooling water according to a command from the ECU 10 to adjust the temperature of the EGR gas passing through the exhaust gas introduction passage 13. . A part of the cooling water flowing through the first flow path 21 flows through the third flow path 23 by the operating force of the water pump 24 and is sent into the EGR cooler 14. The cooling water inside the EGR cooler 14 absorbs heat from the EGR gas passing through the exhaust gas introduction passage 13 and adjusts the EGR gas temperature to a temperature suitable for combustion. In this case, it is desirable to provide a cooling water flow rate adjustment valve at the cooling water inlet of the EGR cooler 14 to adjust the flow rate of the cooling water circulating inside the EGR cooler 14. Then, the cooling water after heat exchange flows from the third flow path 23 through the second flow path 22 and is cooled by the radiator 11, and then is sent to the first flow path 21 again.
Further, the EGR cooler 14 is provided with an EGR cooler temperature sensor 32, detects the temperature of the cooling water inside the EGR cooler 14, and transmits the detection result to the ECU 10. The ECU 10 recognizes the coolant temperature detected by the EGR cooler temperature sensor 32 as the temperature of the EGR cooler 14. In this case, the EGR cooler temperature sensor 32 may directly detect the temperature of the EGR cooler 14 instead of the temperature of the cooling water inside the EGR cooler 14.

The radiator 11 is a radiator that includes an upper tank, a radiator core, and a lower tank. Cooling water that has become hot due to cooling of the engine 100 flows through the second flow path 22 and is guided to the upper tank of the radiator 11 and passes through the radiator core. The radiator core takes heat and dissipates heat into the air when high-temperature cooling water passes through the radiator core, and is provided with a large number of fins in order to improve heat dissipation efficiency. The cooling water cooled by the radiator core flows through the first flow path 21 from the lower tank and is returned to the engine 100 again.
The radiator fan 12 is disposed between the radiator 11 and the engine 100, and cools the radiator 11 by creating an air flow from the radiator 11 toward the engine 100. The radiator fan 12 controls the cooling capacity of the radiator 11 by adjusting the rotation of the fan in accordance with a command from the ECU 10. The radiator fan 12 may rotate the fan in synchronization with the rotation of the engine 100, or may rotate the fan by an electric motor or the like. In the case of synchronizing with the rotation of the engine 100, a variable transmission mechanism such as a clutch mechanism is used for the rotation transmission unit so that the rotation of the fan can be arbitrarily adjusted. Further, the radiator fan 12 is not limited to between the radiator 11 and the engine 100, and can be disposed at an arbitrary position where the radiator 11 can be cooled.

The engine cooling system 1 includes a first flow path 21, a second flow path 22, and a third flow path 23 through which cooling water flows. The first flow path 21 is configured to allow the lower tank of the radiator 11 and the engine 100 to communicate with each other, and circulates cooling water cooled by the radiator 11 to the engine 100. The second flow path 22 is configured to communicate the engine 100 and the upper tank of the radiator 11, and circulates the cooling water heated by the engine 100 to the radiator 11. The third flow path 23 is branched from a first flow path 21 on the outlet (downstream) side of a water pump 24 to be described later, and is joined to the second flow path 22 via the EGR cooler 14. Part of the water is circulated to the EGR cooler 14.
In this case, the 1st flow path 21 is installed below the EGR cooler 14, and the 2nd flow path 22 employ | adopts the structure installed above the EGR cooler 14. FIG. With such a configuration, the cooling water that has been heated by the engine 100 or the EGR cooler 14 and has a reduced density (specific gravity) moves toward the second flow path 22 above and is cooled by the radiator 11. Thus, the cooling water whose density (specific gravity) has increased moves toward the lower first flow path 21. Therefore, since the flow of the cooling water by natural convection is generated, the cooling water in the engine 100 and the EGR cooler 14 can circulate even when the operation of the water pump 24 is stopped.
The third flow path 23 adopts a configuration that branches from the first flow path 21 immediately after the outlet of the water pump 24. By setting it as such a structure, it can suppress that the cooling water cooled and passed through the radiator 11 by natural convection is mixed with the cooling water inside the engine 100, and a warming-up improvement effect falls. This can be suppressed.

  The water pump 24 is provided in the first flow path 21, and circulates cooling water to the radiator 11, the engine 100, and the EGR cooler 14 by the operating force. The water pump 24 employs a mechanical type that operates by transmitting the rotational force of the crankshaft shaft of the engine 100 by a belt or the like, but may employ an electric type that operates by an electric motor or the like, or both types. May be used in combination. The water pump 24 has an electromagnetic clutch in the transmission portion of the rotational force of the crankshaft shaft, and controls the transmission rate of the rotational force from the crankshaft shaft by adjusting the engagement rate of the electromagnetic clutch. Control the operating power of In this case, the operating force of the water pump 24 may be controlled by using another variable transmission mechanism instead of the electromagnetic clutch.

The main thermostat 25 is provided in the first flow path 21 between the radiator 11 and the water pump 24, and controls the communication of the first flow path 21 based on the temperature of the engine 100. The main thermostat 25 employs a general thermostat having a thermo wax as an operating source, but may employ an electric thermostat having a linear solenoid as an operating source. The main thermostat 25 adjusts the flow rate of the cooling water flowing through the first flow path 21 by changing the valve opening degree according to the temperature of the engine 100, that is, the temperature of the cooling water. The main thermostat 25 closes the first flow path 21 by closing when the cooling water temperature is lower than the second temperature (for example, 90 [° C.]), and gradually opens the cooling water temperature at the second temperature or higher. It is comprised so that the 1st flow path 21 may be connected.
The main thermostat 25 is connected to a cooling water flow path communicating with the third flow path 23 above the water jacket of the engine 100 and downstream of the EGR cooler 14, and a part of the heated cooling water is supplied to the radiator. 11 is supplied to the main thermostat 25 without going through 11. Thereby, when the engine 100 and the EGR cooler 14 are hot, the valve opening degree of the main thermostat 25 can be improved more reliably and the flow rate of the cooling water can be increased.
The main thermostat 25 corresponds to the first thermostat of the present invention.

The sub thermostat 26 is provided at a position closer to the engine 100 than the second flow path 22, and controls the communication of the second flow path 22 based on the temperature of the engine 100. The sub thermostat 26 has a structure similar to that of the main thermostat 25, and changes the valve opening degree according to the temperature of the engine 100, that is, the temperature of the cooling water, thereby allowing the cooling water flowing through the second flow path 22. Adjust the flow rate.
In this case, the sub thermostat 26 is configured to open at a third temperature (for example, 85 [° C.]) lower than the main thermostat 25. By adopting such a configuration, since the sub thermostat 26 is opened first when the engine 100 is warmed up, it is possible to suppress the sub thermostat 26 from interfering with the temperature control of the cooling water by the main thermostat 25. it can. Further, when the water pump 24 cannot be operated due to a failure or the like, the sub thermostat 26 opens early due to an increase in the coolant temperature inside the engine 100. As a result, natural convection of the cooling water from the engine 100 toward the radiator 11 occurs, so that the cooling water inside the engine 100 circulates, so that the engine 100 is cooled.
The sub thermostat 26 corresponds to the second thermostat of the present invention.

The bypass flow path 27 branches from the first flow path 21 between the radiator 11 and the main thermostat 25 (upstream side), and the first flow path 21 between the main thermostat 25 and the water pump 24 (downstream side). By adopting a configuration that joins the main thermostat 25, the main thermostat 25 is bypassed and the cooling water is circulated.
By providing the bypass flow path 27, the cooling water can be circulated without passing through the main thermostat 25 even when the main thermostat 25 closes the first flow path 21. Therefore, even when the main thermostat 25 is closed and the operation of the water pump 24 is stopped, the natural flow between the third flow path 23, the radiator 11, and the first flow path 21 to the bypass flow path 27 can be reduced. A cooling water flow is generated by convection (see FIG. 2B). Therefore, when the EGR cooler 14 becomes high temperature while the engine 100 is warmed up, the cooling water in the EGR cooler 14 can be circulated, so that the EGR cooler 14 can be prevented from overheating.
In this case, a configuration is adopted in which the upstream branch portion of the bypass flow path 27 is branched immediately before the main thermostat 25. By adopting such a configuration, the temperature of the cooling water circulating through the bypass channel 27 is easily conducted to the vicinity of the main thermostat 25, and therefore, when the circulating cooling water temperature is high, the valve opening of the main thermostat 25 is promoted. Can do. Therefore, when the cooling capacity of the radiator 11 is insufficient, the cooling capacity of the engine 100 can be improved by opening the main thermostat 25 at an early stage and increasing the flow rate of circulating cooling water.

The bypass flow path 27 is provided with a one-way valve 27a. On the other hand, the valve 27a is closed when the water pump 24 is operating to close the bypass passage 27, and is opened when the operation of the water pump 24 is stopped to allow the bypass passage 27 to communicate. The cooling water is circulated in the direction of the water pump 24. Thereby, since the bypass flow path 27 is closed when the water pump 24 is operating, the cooling water can be circulated through the main thermostat 25 (see FIG. 2). Therefore, the temperature control of the cooling water by the main thermostat 25 can be appropriately executed.
On the other hand, as the valve 27a, a gravity valve that is closed by the negative pressure of the water pump 24 and opens by its own weight when there is no negative pressure can be applied. In this case, a gravity valve having an appropriate weight that does not close by natural convection of the cooling water is applied.

  The ECU 10 includes a CPU (Central Processing Unit) that performs arithmetic processing, a ROM (Read Only Memory) that stores programs, a RAM (Random Access Memory) that stores data, and an NVRAM (Non Volatile RAM). It is a computer. The ECU 10 reads the detection results of the crank angle sensor, the intake cam angle sensor, the air flow meter, the throttle position sensor, the exhaust temperature sensor, the water temperature sensor 31 and the like, and operates the throttle valve, the opening / closing timing of the intake valve and the exhaust valve, and the operation of the injector The operation of the engine 100 is controlled in an integrated manner, such as the ignition timing of the spark plug and the recirculation amount of EGR gas.

Further, the ECU 10 executes warm-up improvement control for stopping the operation of the water pump 24 when the engine 100 is warm-up.
FIG. 3 shows an example of the relationship between the cooling water temperature and the operation area of each component. Based on the detection result of the water temperature sensor 31, the ECU 10 disconnects the electromagnetic clutch of the water pump 24 when the coolant temperature of the engine 100 is lower than a predetermined temperature. By executing this control, it is possible to suppress the cooling water inside the water jacket from being circulated during the warm-up of the engine 100, so that the warm-up performance of the engine 100 can be improved. Here, as the predetermined temperature for determining whether or not to disconnect the electromagnetic clutch, an arbitrary cooling water temperature lower than the operation start temperature (first temperature) of the water pump 24 is applied, and is set to 85 [° C.], for example. can do. Moreover, although the arbitrary cooling water temperature which should give priority to cooling of the engine 100 is applied with 1st temperature, it can set to 90 [degreeC], for example.
The ECU 10 engages the electromagnetic clutch of the water pump 24 to start circulation of the cooling water when the cooling water temperature of the engine 100 becomes the first temperature or higher.

Then, the ECU 10 executes control for changing the recirculation amount of the EGR gas in accordance with the progress of warming up of the engine 100.
FIG. 4 shows a control example of the EGR gas recirculation amount based on the cooling water temperature. Based on the detection result of the water temperature sensor 31, the ECU 10 stops the recirculation of EGR gas when the coolant temperature of the engine 100 is lower than a predetermined temperature. When the EGR gas is recirculated when the internal combustion engine is at a low temperature, the combustion of the internal combustion engine is deteriorated because the EGR gas is at a low temperature. Therefore, it is possible to prevent the combustion of engine 100 from deteriorating by stopping the recirculation of EGR gas when the coolant temperature is less than the predetermined temperature. Here, as the predetermined temperature for determining whether or not to stop the recirculation of the EGR gas, an arbitrary cooling water temperature at which it can be determined that the combustion of the engine 100 does not deteriorate is applied, for example, set to 40 [° C.]. Can do.

The ECU 10 starts the recirculation of EGR gas when the coolant temperature of the engine 100 becomes equal to or higher than a predetermined temperature. By executing this control, the intake negative pressure decreases and the pump loss during intake decreases, so the fuel consumption of the engine 100 can be improved. Moreover, since the combustion temperature of the engine 100 is lowered, the amount of NOx emission can be reduced. In this case, the ECU 10 bypasses the EGR cooler 14 and recirculates the EGR gas until the cooling water temperature reaches a predetermined temperature (for example, 60 [° C.]), so that the combustion becomes unstable due to the low temperature of the EGR gas. Suppress.
During the warm-up improvement control, the main thermostat 25 is closed and the operation of the water pump 24 is stopped. Therefore, when the cooling water temperature becomes equal to or higher than the predetermined temperature and the recirculation of the EGR gas is started, gradually. The temperature of the EGR cooler 14 increases. Here, when the temperature of the EGR cooler 14 rises, a flow of cooling water by natural convection is generated between the third flow path 23, the radiator 11, and the first flow path 21 and the bypass flow path 27, so that the EGR cooler 14 The cooling water inside circulates. Therefore, since the low-temperature cooling water flows into the EGR cooler 14, it is possible to suppress the EGR cooler 14 from overheating (see FIGS. 2A and 2B).

  ECU10 stops the recirculation | reflux of EGR gas, when the cooling water temperature of the engine 100 becomes more than predetermined temperature. By executing this control, it is possible to prevent the EGR cooler 14 from overheating due to a large amount of high-temperature EGR gas being refluxed. Here, as the predetermined temperature for determining whether or not to stop the recirculation of the EGR gas, any cooling water temperature at which it is possible to determine that the EGR cooler 14 may be overheated is applied. Can be set.

Further, the ECU 10 controls the operation of the radiator fan 12 according to the coolant temperature or the temperature of the EGR cooler 14 while the engine 100 is warmed up (see FIG. 3).
Based on the detection result of the water temperature sensor 31, the ECU 10 stops the operation of the radiator fan 12 when the cooling water temperature of the engine 100 is lower than a predetermined temperature. By executing this control, it is possible to suppress the temperature of the cooling water from excessively decreasing. Here, as the predetermined temperature for determining whether or not to stop the operation of the radiator fan 12, any cooling water temperature lower than the operation start temperature (fourth temperature) of the radiator fan 12 can be applied. It can be set to 90 [° C.]. Moreover, although arbitrary cooling water temperature can be applied with 4th temperature according to the cooling capacity of the radiator 11, it can set to 95 [degreeC], for example.
The ECU 10 starts the operation of the radiator fan 12 when the coolant temperature of the engine 100 becomes the fourth temperature or higher. Further, when the ECU 10 determines that the temperature of the EGR cooler 14 is equal to or higher than the first threshold value based on the detection result of the EGR cooler temperature sensor 32, that is, when the EGR cooler 14 needs to be cooled, The operation of the radiator fan 12 is started. Thereby, since the cooling water which circulates through the engine 100 and the EGR cooler 14 can be cooled to a lower temperature, the engine 100 and the EGR cooler 14 can be prevented from overheating. Here, although the arbitrary cooling water temperature which can judge that the EGR cooler 14 may overheat is applied with a 1st threshold value, it can set to 100 [degreeC], for example.

  Next, the operation of the engine cooling system 1 will be described along the control flow of the ECU 10. FIG. 5 is a flowchart showing an example of processing of the ECU 10. The engine cooling system 1 according to the present embodiment includes a first flow path, a second flow path, a refrigerant pump, a main thermostat, a sub thermostat, a third flow path, and a bypass flow path. Even when the pump that circulates is stopped, the refrigerant in the internal combustion engine or the EGR cooler can be circulated to suppress overheating.

  The control of the ECU 10 starts when an engine start request is made, that is, when the ignition switch is turned on, and is executed at predetermined intervals while the ignition switch is on. First, in step S1, the ECU 10 executes the warm-up improvement control of the engine 100 by stopping the operation of the radiator fan 12 while disconnecting the electromagnetic clutch of the water pump 24 (see FIG. 2A). After finishing the process of step S1, the ECU 10 proceeds to the next step S2.

  In step S <b> 2, the ECU 10 determines whether or not the cooling water temperature in the EGR cooler 14 is less than the first threshold value based on the detection result of the EGR cooler temperature sensor 32. Here, since the first threshold value has been described above, a detailed description thereof will be omitted. When the cooling water temperature in the EGR cooler 14 is not lower than the first threshold value, that is, not lower than the first threshold value (step S2 / NO), the ECU 10 determines that the EGR cooler 14 may be overheated, Proceed to step S7. If the cooling water temperature in the EGR cooler 14 is lower than the first threshold value (step S2 / YES), the ECU 10 proceeds to the next step S3.

  In step S <b> 3, the ECU 10 determines whether the cooling water temperature is equal to or higher than the valve opening temperature (third temperature) of the sub thermostat 26 based on the detection result of the water temperature sensor 31. Here, since the valve opening temperature of the sub thermostat 26 was mentioned above, the detailed description is abbreviate | omitted. When the cooling water temperature is not equal to or higher than the valve opening temperature of the sub thermostat 26 (step S3 / NO), the ECU 10 ends the control process. When the cooling water temperature is equal to or higher than the valve opening temperature of the sub thermostat 26 (step S3 / YES), the ECU 10 determines that the sub thermostat 26 is open, that is, the second flow path is in communication, and the next Proceed to step S4.

  In step S <b> 4, the ECU 10 determines whether or not the cooling water temperature is equal to or higher than the valve opening temperature (second temperature) of the main thermostat 25 based on the detection result of the water temperature sensor 31. Here, since the valve opening temperature of the main thermostat 25 was mentioned above, the detailed description is abbreviate | omitted. When the cooling water temperature is not equal to or higher than the valve opening temperature of the main thermostat 25 (step S4 / NO), the ECU 10 ends the control process. When the cooling water temperature is equal to or higher than the valve opening temperature of the main thermostat 25 (step S4 / YES), the ECU 10 determines that the main thermostat 25 is open, that is, the first flow path is in communication, and the next Proceed to step S5.

In step S5, the ECU 10 determines that the engine 100 has been sufficiently warmed up, engages the electromagnetic clutch of the water pump 24 separated in step S1, and operates the water pump 24. By executing this control, the coolant can be circulated through the engine 100 and the EGR cooler 14 that have been sufficiently warmed up to a high temperature to cool to an appropriate temperature (see FIG. 2C).
After finishing the process of step S5, the ECU 10 proceeds to the next step S6.

  In step S <b> 6, the ECU 10 determines whether the cooling water temperature is equal to or higher than the operation start temperature (fourth temperature) of the radiator fan 12 based on the detection result of the water temperature sensor 31. Here, since the operation start temperature of the radiator fan 12 has been described above, a detailed description thereof will be omitted. If the coolant temperature is not equal to or higher than the operation start temperature of the radiator fan 12 (step S6 / NO), the ECU 10 ends the control process. If the coolant temperature is equal to or higher than the operation start temperature of the radiator fan 12 (step S6 / YES), the ECU 10 proceeds to the next step S7.

When the determination in step S2 is NO or when the process in step S6 is completed, the ECU 10 proceeds to step S7. In step S7, the ECU 10 determines that the temperature of the cooling water circulating in the engine cooling system 1 is high, starts the operation of the radiator fan 12 stopped in step S1, and cools the radiator 11. By executing this control, the cooling capacity of the radiator 11 can be improved and the cooling water circulating in the engine cooling system 1 can be cooled to a lower temperature, so that the engine 100 and the EGR cooler 14 can be prevented from overheating. it can.
When the ECU 10 finishes the process of step S7, the ECU 10 ends the control process.

  Next, a flow for determining a failure of the water pump 24 will be described. FIG. 6 is a flowchart illustrating an example of processing of the ECU 10. The control of the ECU 10 starts when the control of step S7 is executed, that is, when the operation of the radiator fan 12 is started, and is executed at predetermined time intervals while the radiator fan 12 is operating. First, in step S8, the ECU 10 determines whether or not the cooling water temperature has decreased for a predetermined period from the start of the operation of the radiator fan 12 based on the detection result of the water temperature sensor 31. Here, the predetermined period can be set to an arbitrary period based on the flow rate of the cooling water or the like. If the coolant temperature has decreased for a predetermined period after the radiator fan 12 starts operating (step S8 / YES), the ECU 10 determines that the water pump 24 is operating normally, and ends the control process. If the cooling water temperature has not decreased for a predetermined period after the start of operation of the radiator fan 12 (step S8 / NO), the ECU 10 proceeds to the next step S9.

In step S9, the ECU 10 determines that the water pump 24 is not operating normally, and warns that the water pump 24 is abnormal. As the warning, various methods that can transmit the abnormality of the water pump 24 to the driver, such as turning on a warning lamp, can be employed.
After finishing the process of step S9, the ECU 10 proceeds to the next step S10.

  In step S10, the ECU 10 determines whether or not the cooling water temperature of the engine 100 is maintained at a predetermined temperature or less by circulating the cooling water by natural convection based on the detection result of the water temperature sensor 31. Here, the predetermined temperature is an arbitrary cooling water temperature at which the engine 100 can be determined to be overheated, and can be set to 100 [° C.], for example. When the coolant temperature of engine 100 is maintained at a predetermined temperature or lower (step S10 / YES), ECU 10 determines that the output of engine 100 can be maintained, and ends the control process. If the coolant temperature of engine 100 is not maintained below the predetermined temperature (step S10 / NO), ECU 10 proceeds to next step S11.

In step S11, ECU 10 determines that there is a possibility of overheating if the output of engine 100 is maintained, and limits the output of engine 100. In this case, the ECU 10 limits the output of the engine 100 based on the cooling heat receiving (Qw) map of the engine 100 in FIG. 7 so that, for example, Qw does not exceed 50% of the maximum value. Suppresses overheating. It should be noted that the output limit of engine 100 can be arbitrarily set according to the traveling state of the vehicle.
When the ECU 10 finishes the process of step S11, the ECU 10 proceeds to next step S12.

  In step S12, the ECU 10 determines whether or not the cooling water temperature of the engine 100 after the output restriction is maintained below a predetermined temperature based on the detection result of the water temperature sensor 31. Here, the predetermined temperature is an arbitrary cooling water temperature at which it can be determined that there is a risk of overheating of the engine 100, and can be set to 110 [° C.], for example. When the coolant temperature of engine 100 is maintained at a predetermined temperature or lower (step S12 / YES), ECU 10 determines that the risk of overheating of engine 100 is low, and ends the control process. When the cooling water temperature of engine 100 is not maintained below the predetermined temperature (step S12 / NO), ECU 10 proceeds to next step S13.

In step S13, the ECU 10 determines that there is a risk of overheating of the engine 100, and limits the output of the engine 100 to the minimum output necessary for the vehicle to evacuate. In this case, the ECU 10 restricts the output of the engine 100 based on the cooling heat receiving (Qw) map of the engine 100 in FIG. 7 so that the Qw does not exceed 25% of the maximum value, for example. Suppresses overheating. It should be noted that the output limit of engine 100 can be arbitrarily set according to the traveling state of the vehicle.
ECU10 complete | finishes the process of control, after finishing the process of step S13.

  Next, a flow for determining stop of the radiator fan 12 based on the detection result of the EGR cooler temperature sensor 32 will be described. FIG. 8 is a flowchart showing an example of processing of the ECU 10. The control of the ECU 10 starts when the control of step S7 is executed, that is, when the operation of the radiator fan 12 is started, and is executed at predetermined time intervals while the radiator fan 12 is operating. First, in step S14, the ECU 10 determines whether or not the coolant temperature in the EGR cooler 14 is equal to or higher than a first threshold value based on the detection result of the EGR cooler temperature sensor 32. Here, since the first threshold value has been described above, a detailed description thereof will be omitted. When the cooling water temperature in the EGR cooler 14 is equal to or higher than the first threshold value (step S14 / YES), the ECU 10 determines that it is necessary to continue cooling the radiator 11, and ends the control process. If the cooling water temperature in the EGR cooler 14 is not equal to or higher than the first threshold value (step S14 / NO), the ECU 10 proceeds to the next step S15.

  In step S15, the ECU 10 determines that the possibility that the EGR cooler 14 is overheated is low, and stops the operation of the radiator fan 12 that started the operation in step S3. After finishing the process of step S15, the ECU 10 ends the control process.

  And the flow which determines the operation stop of the water pump 24 and the radiator fan 12 based on the detection result of the water temperature sensor 31 is demonstrated. FIG. 9 is a flowchart illustrating an example of processing of the ECU 10. The control of the ECU 10 is started when the control of step S5 or step S7 is executed, that is, when the operation of the water pump 24 or the radiator fan 12 is started, and for a predetermined time while the water pump 24 or the radiator fan 12 is operated. It is executed every time. First, in step S <b> 16, the ECU 10 determines whether the cooling water temperature is equal to or lower than the operation stop temperature of the radiator fan 12 based on the detection result of the water temperature sensor 31. Here, the operation stop temperature of the radiator fan 12 is an arbitrary cooling water temperature lower than the operation start temperature (fourth temperature) of the radiator fan 12, and can be set to 90 ° C., for example. If the cooling water temperature is not lower than the operation stop temperature of the radiator fan 12 (step S16 / NO), the ECU 10 determines that the cooling of the radiator 11 needs to be continued, and ends the control process. If the coolant temperature in the EGR cooler 14 is equal to or lower than the predetermined temperature (step S16 / YES), the ECU 10 proceeds to the next step S17.

  In step S17, the ECU 10 determines that the possibility that the engine 100 is overheated is low, and stops the operation of the radiator fan 12 that has started the operation in step S7. After finishing the process of step S17, the ECU 10 proceeds to the next step S18.

  In step S <b> 18, the ECU 10 determines whether the cooling water temperature is equal to or lower than the operation stop temperature of the water pump 24 based on the detection result of the water temperature sensor 31. Here, as the operation stop temperature of the water pump 24, an arbitrary cooling water temperature lower than the operation start temperature (first temperature) of the water pump 24 is applied, and may be set to, for example, 85 [° C.]. If the coolant temperature is not equal to or lower than the operation stop temperature of the water pump 24 (step S18 / NO), the ECU 10 determines that the operation of the water pump 24 needs to be continued and ends the control process. If the coolant temperature is equal to or lower than the operation stop temperature of the water pump 24 (step S18 / YES), the ECU 10 proceeds to the next step S19.

  In step S19, the ECU 10 determines that the possibility of overheating of the engine 100 is low, and disconnects the electromagnetic clutch engaged in step S5 to stop the operation of the water pump 24. After finishing the process of step S19, the ECU 10 ends the control process.

  As described above, the engine cooling system 1 according to this embodiment includes the first flow path, the second flow path, the refrigerant pump, the main thermostat, the sub thermostat, the third flow path, and the bypass flow path. By providing, even if the pump that circulates the refrigerant is stopped, the refrigerant in the internal combustion engine or the EGR cooler can be circulated. Therefore, overheating can be suppressed by ensuring the circulation of the refrigerant even when the pump is stopped.

  Next, a second embodiment of the present invention will be described. The engine cooling system 2 of the present embodiment is different from the engine cooling system 1 in that an EGR thermostat is provided in a third flow path between the EGR cooler and the second flow path.

As in the first embodiment, the engine cooling system 2 of the present embodiment includes a first flow path 21, a second flow path 22, a third flow path 23, a water pump 24, a main thermostat 25, a sub thermostat 26, and a bypass flow path 27. The cooling water in the engine 100 and the EGR cooler 14 can be circulated by natural convection even when the water pump 24 is stopped.
Furthermore, the engine cooling system 2 includes the EGR thermostat 28 in the third flow path 23, so that the flow rate of the cooling water circulating through the EGR cooler 14 can be adjusted according to the warm-up state of the engine 100. Therefore, it is possible to recirculate EGR gas having an appropriate temperature to the intake side, and to suppress overheating of the EGR cooler 14.

FIG. 10 is a configuration diagram showing a schematic configuration of an engine cooling system 2 incorporating the cooling device for an internal combustion engine of the present invention.
The EGR thermostat 28 is provided at a position closer to the EGR cooler 14 than the third flow path 23, and controls the communication of the third flow path 23 based on the temperature of the EGR cooler 14. The EGR thermostat 28 has the same structure as the main thermostat 25, and changes the valve opening degree according to the temperature of the EGR cooler 14, that is, the temperature of the cooling water inside the EGR cooler 14, so that the third flow path 23 Adjust the flow rate of the cooling water flowing through. Thereby, the flow rate of the cooling water circulating through the EGR cooler 14 is adjusted, and the cooling capacity of the EGR cooler 14 is controlled.
In this case, the EGR thermostat 28 is configured to open gradually from a cooling water temperature (for example, 60 [° C.]) that is lower than the sub thermostat 26 and starts cooling the EGR gas. With this configuration, when the recirculation of the EGR gas is started in the warm-up control of the engine 100, the EGR thermostat 28 is opened according to the warm-up state of the engine 100, that is, the EGR gas temperature to be recirculated. To do. Therefore, since the flow rate of the cooling water circulating through the EGR cooler 14 can be appropriately adjusted, it is possible to suppress overcooling or insufficient cooling of the EGR gas (see FIG. 11).
The EGR thermostat 28 corresponds to the third thermostat of the present invention.

Next, the operation of the engine cooling system 2 will be described along the control flow of the ECU 10. FIG. 12 is a flowchart illustrating an example of processing of the ECU 10. The ECU 10 of the engine cooling system 2 performs the following control from step S20 to step S26 together with the processing from step S1 to step S19 of the engine cooling system 1 of the first embodiment. Therefore, since the control from step S1 to step S19 is the same as that of the engine cooling system 1 of the first embodiment, detailed description thereof is omitted.
The engine cooling system 2 according to the present embodiment includes the EGR thermostat 28 in the third flow path 23, so that the flow rate of the cooling water circulating through the EGR cooler 14 can be adjusted according to the warm-up state of the engine 100.

The control of the ECU 10 starts when an engine start request is made, that is, when the ignition switch is turned on, and is executed at predetermined intervals while the ignition switch is on. First, in step S20, the ECU 10 instructs the EGR valve to close and stops the recirculation of the EGR gas (see FIG. 11). By executing this control, it is possible to prevent the combustion of the engine 100 from deteriorating due to the recirculation of the low-temperature EGR gas.
When the ECU 10 finishes step S20, the ECU 10 proceeds to next step S21.

  In step S <b> 21, the ECU 10 determines whether the coolant temperature of the engine 100 is equal to or higher than the EGR gas recirculation start temperature based on the detection result of the water temperature sensor 31. Here, the EGR gas recirculation start temperature is an arbitrary cooling water temperature at which it can be determined that combustion of the engine 100 does not deteriorate even if EGR gas recirculation is started, and can be set to 40 [° C.], for example. . If the coolant temperature of engine 100 is not equal to or higher than the EGR gas recirculation start temperature (step S21 / NO), ECU 10 ends the control process. When the coolant temperature of engine 100 is equal to or higher than the EGR gas recirculation start temperature (step S21 / YES), ECU 10 proceeds to next step S22.

In step S22, the ECU 10 instructs the EGR valve closed in step S20 to open, and starts recirculation of EGR gas through the bypass passage, that is, by bypassing the EGR cooler 14 (see FIG. 11). By executing this control, it is possible to improve the fuel efficiency of the engine 100 or reduce the NOx emission amount. In this case, the ECU 10 controls the EGR valve opening according to the coolant temperature and adjusts it to an appropriate recirculation amount of the EGR gas (see FIG. 4).
After finishing the process of step S22, the ECU 10 proceeds to the next step S23.

  In step S23, the ECU 10 determines whether or not the cooling water temperature of the engine 100 is equal to or higher than the EGR gas cooling start temperature based on the detection result of the water temperature sensor 31. Here, the EGR gas cooling start temperature is an arbitrary cooling water temperature at which it can be determined that combustion of the engine 100 does not deteriorate even when the EGR gas is cooled, and can be set to 60 [° C.], for example. If the coolant temperature of engine 100 is not equal to or higher than the EGR gas cooling start temperature (step S23 / NO), ECU 10 ends the control process. When the coolant temperature of engine 100 is equal to or higher than the EGR gas cooling start temperature (step S23 / YES), ECU 10 proceeds to next step S24.

In step S24, the ECU 10 determines that the EGR thermostat 28 is open, that is, the third flow path 23 is in communication, and recirculates the EGR gas bypassed in step S22 via the EGR cooler 14. (See FIG. 11). By executing this control, the EGR gas can be cooled by the EGR cooler 14 to increase the density, so that more EGR gas can be recirculated. In this case, since the EGR thermostat 28 is opened, a flow of cooling water by natural convection is generated between the third flow path 23, the radiator 11, and the first flow path 21 to the bypass flow path 27. Therefore, the EGR cooler The cooling water in 14 circulates. Therefore, since the low-temperature cooling water flows into the EGR cooler 14, it is possible to suppress the EGR cooler 14 from overheating even when the operation of the water pump 24 is stopped (FIG. 13B). )reference).
After finishing the process of step S24, the ECU 10 proceeds to the next step S25.

  In step S25, the ECU 10 determines whether or not the cooling water temperature of the engine 100 is equal to or higher than the EGR gas recirculation stop temperature based on the detection result of the water temperature sensor 31. Here, as the EGR gas recirculation stop temperature, any cooling water temperature at which it can be determined that the EGR cooler 14 may be overheated is applied, and can be set to 100 [° C.], for example. When the coolant temperature of engine 100 is not equal to or higher than the EGR gas recirculation stop temperature (step S25 / NO), ECU 10 ends the control process. When the coolant temperature of engine 100 is equal to or higher than the EGR gas recirculation stop temperature (step S25 / YES), ECU 10 proceeds to next step S26.

In step S26, the ECU 10 instructs the EGR valve to close, and stops the recirculation of the EGR gas (see FIG. 11). By executing this control, it is possible to prevent the EGR cooler 14 from overheating due to a large amount of high-temperature EGR gas being refluxed.
ECU10 complete | finishes the process of control, after finishing the process of step S26.

  As described above, the engine cooling system 2 according to the present embodiment includes the EGR thermostat in the third flow path between the EGR cooler and the second flow path, so that the EGR cooler is provided according to the warm-up state of the internal combustion engine. The flow rate of the circulating cooling water can be adjusted. Therefore, it is possible to recirculate EGR gas having an appropriate temperature to the intake side, and to suppress overheating of the EGR cooler 14.

  The above embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to these, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

1 Engine cooling system 10 ECU
DESCRIPTION OF SYMBOLS 11 Radiator 12 Radiator fan 13 Exhaust gas introduction path 14 EGR cooler 21 1st flow path 22 2nd flow path 23 3rd flow path 24 Water pump (refrigerant pump)
25 Main thermostat (1st thermostat)
26 Deputy thermostat (second thermostat)
27 Bypass passage 27a One-way valve 31 Water temperature sensor 32 EGR cooler temperature sensor 100 Engine

Claims (6)

A cooling device for an internal combustion engine comprising an EGR cooler for cooling EGR gas of the internal combustion engine,
A first flow path for circulating the refrigerant circulated through the radiator toward the internal combustion engine;
A second flow path for circulating the refrigerant circulated through the internal combustion engine toward the radiator;
A refrigerant pump that is provided in the first flow path and circulates the refrigerant by operating when the internal combustion engine is at or above a first temperature;
A first thermostat that is provided in the first flow path between the radiator and the refrigerant pump and that allows the refrigerant to flow through the first flow path by opening when the internal combustion engine is at a second temperature or higher. When,
A second thermostat provided in the second flow path between the internal combustion engine and the radiator and allowing the refrigerant to flow through the second flow path by opening when the internal combustion engine is at a third temperature or higher. When,
Branching from the first flow path on the outlet side of the refrigerant pump and joining the downstream side of the second thermostat of the second flow path via the EGR cooler, a part of the refrigerant is transferred to the EGR cooler A third flow path for circulating
The first flow path between the radiator and the first thermostat branches off from the first flow path to join the first flow path between the first thermostat and the refrigerant pump, and the refrigerant bypasses the first thermostat. A bypass flow path to be distributed,
A cooling device for an internal combustion engine, comprising:   The cooling apparatus for an internal combustion engine according to claim 1, wherein the first flow path is provided below the EGR cooler, and the second flow path is provided above the EGR cooler. .   The cooling apparatus for an internal combustion engine according to claim 1 or 2, wherein the bypass passage allows the refrigerant to flow only when the refrigerant pump is not operating.   4. The cooling device for an internal combustion engine according to claim 1, wherein the second thermostat opens at a lower temperature than the first thermostat. 5. A third thermostat that is provided in the third flow path between the EGR cooler and the second flow path, and opens the valve when the EGR cooler is at a predetermined temperature or higher to communicate the third flow path; Prepared,
5. The cooling device for an internal combustion engine according to claim 1, wherein the third thermostat opens at a lower temperature than the second thermostat. 6. Radiator cooling means for cooling the radiator when the internal combustion engine is at a fourth temperature or higher,
The radiator cooling means cools the radiator when the internal combustion engine is less than a fourth temperature and the temperature of the EGR cooler is equal to or higher than a first threshold value. The internal combustion engine cooling device according to claim 1.

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