Engine cooling device

Abstract

To easily suppress excessive rise of water pressure in a cooling water circuit.SOLUTION: A cooling water circuit C for circulating cooling water through an engine 10 connected to a wheel via a manual transmission includes: a mechanical water pump 21; a radiator water channel 23 passing a radiator 20; a first bypass water channel 24 and a second bypass water channel 25 bypassing the radiator 20; and a multifunctional valve 22 switching a state in which water passing in the radiator water channel 23 is blocked and a state in which the water passing is permitted according to an operation of a valve element 22A. An ECU 30 executes a retreating process to start driving of the valve element 22A so as to shorten a time necessary for starting the water passing in the radiator water channel 23 in a case where an engine rotating speed becomes a retreating determination value or more during blockage of the water passing in the radiator water channel 23, and a changing process for changing the retreating determination value to be increased when a ratio of the engine rotating speed to a vehicle speed is larger in comparison with a case where the ratio is small.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Patent Document 1 describes a device as an engine cooling device, which includes a radiator water passage passing through a radiator, a bypass water passage bypassing the radiator, and a switching valve for switching between a closed state and an open state of the radiator water passage. Further, the engine cooling device includes a control unit that controls the switching valve so as to close the radiator water passage during warm-up of the engine and open the radiator water passage after completion of warm-up. Furthermore, when the operating state of the engine during the closing of the radiator water passage becomes an operating state in which the pressure loss of the cooling water flowing through the cooling water circuit increases and cavitation is likely to occur, the control unit opens the radiator water passage. And thereby, by reducing the pressure loss of the cooling water flowing through the cooling water circuit, the occurrence of cavitation is suppressed. Note that the control unit determines whether or not the operating state is an operating state in which cavitation is likely to occur based on the opening degree of the switching valve, the temperature of the cooling water, and the engine speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the cooling device as described above, as a water pump for circulating cooling water, a mechanical pump that operates by receiving the rotation of the engine may be employed. In a cooling device that employs a mechanical water pump, the flow rate of the cooling water circulating in the cooling water circuit increases in accordance with an increase in the engine speed. When the radiator water passage is closed, the flow rate of the cooling water in the bypass water passage increases more than when it is open. Therefore, if the engine speed increases while the radiator water passage is closed, there is a risk that the water pressure in the bypass water passage will rise beyond the allowable limit.

Means for Solving the Problem

[0005] The engine cooling device that solves the above problems cools an engine connected to wheels via a manual transmission capable of manually switching gear stages. The engine cooling device has a cooling water circuit that circulates cooling water through the engine, and a control unit. The cooling water circuit includes a mechanical water pump that operates by receiving the rotation of the engine, a radiator water passage that passes through a radiator, a bypass water passage that bypasses the radiator, and a switching valve that switches between a state where the water flow through the radiator water passage is blocked and a state where the water flow is allowed, according to the operation of a valve body. On the other hand, when the engine speed becomes equal to or higher than an evacuation determination value during the interruption of the water flow through the radiator water passage, the control unit performs an evacuation process of instructing the driving of the valve body in the direction in which the switching position is located as viewed from the current operating position, and a change process of changing the evacuation determination value so as to be a smaller value when the NV ratio, which is the ratio of the engine speed to the vehicle speed, is large than when the NV ratio is small. Note that the switching position is the operating position of the valve body at which the state of blocking the water flow and the state of allowing the water flow are switched.

[0006] When the valve body is driven in the direction where the switching position is located as viewed from the current operating position, the driving amount of the valve body required for switching from the state of blocking the water flow in the radiator water passage to the state of allowing the water flow is reduced. Therefore, by predicting the increase in the water pressure in the bypass water passage and performing the evacuation process, it becomes easier to suppress the increase in the water pressure in the bypass water passage exceeding the allowable limit. On the other hand, in a vehicle equipped with a manual transmission, the engine and the wheels are disconnected and connected by the operation of the user. When the engine and the wheels are disconnected, the engine speed tends to increase faster than when they are connected. Further, when the engine speed is increasing in the state where the engine and the wheels are disconnected, the ratio of the engine speed to the vehicle speed becomes large. The control unit of the engine cooling device performs the evacuation process at a lower engine speed when the ratio is large than when the ratio is small. Therefore, the engine cooling device has the effect of making it easier to suppress an excessive increase in the water pressure in the cooling water circuit.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0008] Hereinafter, an embodiment of the engine cooling device will be described in detail with reference to FIGS. 1 to 6. First, referring to FIG. 1, the configuration of the drive system of a vehicle equipped with the engine cooling device of the present embodiment will be described. The vehicle having the drive system shown in FIG. 1 is configured as a part-time four-wheel drive vehicle capable of manually switching between two-wheel drive running and four-wheel drive running.

[0009] As shown in FIG. 1, an engine 10, a manual transmission 11, and a transfer 12 are provided in the drive system of the vehicle. Drive shafts 13 and 14 on the front-wheel side and the rear-wheel side are connected to the transfer 12. The drive shaft 13 on the front-wheel side is connected to the left and right front wheels 16 via a front-wheel side differential 15. The drive shaft 14 on the rear-wheel side is connected to the left and right rear wheels 18 via a rear-wheel side differential 17. The manual transmission 11 changes the rotation of the engine 10 and outputs it to the transfer 12. The gear ratio of the manual transmission 11 is changed by switching the gear stage by the manual operation of the user. A sub-transmission 19 is provided in the transfer 12. That is, in the drive system of FIG. 1, the sub-transmission 19 is interposed between the manual transmission 11 and the wheels. The sub-transmission 19 has three gear stages: "2H", "4H", and "4L". The gear stage of the sub-transmission 19 can be switched by the manual operation of the user. When the gear stage of the sub-transmission 19 is "2H", the transfer 12 transmits the power input from the manual transmission 11 only to the drive shaft 14 on the rear-wheel side. When the gear stage of the sub-transmission 19 is "4H" or "4L", the transfer 12 distributes the power input from the manual transmission 11 to both the drive shafts 13 and 14 on the front-wheel side and the rear-wheel side. Further, when the gear stage is "4L", the gear ratio of the sub-transmission 19 is higher than when the gear stage is "2H" or "4H". In the present embodiment, "4L" corresponds to the low-speed gear stage of the sub-transmission 19, and "4H" and "2H" correspond to the high-speed gear stages, respectively.

[0010] Next, referring to FIG. 2, the configuration of the engine cooling device of the present embodiment will be described. The engine cooling device shown in FIG. 2 has a cooling water circuit C that circulates cooling water through the interior of the engine 10. The cooling water circuit C includes a radiator 20 and a mechanical water pump 21. The radiator 20 is a heat exchanger that cools the cooling water by heat exchange between the cooling water and the outside air. The water pump 21 operates in response to the rotation of the engine 10 and sends the cooling water to the engine 10. The flow rate of the cooling water discharged by the water pump 21, that is, the flow rate of the cooling water circulating through the cooling water circuit C, increases as the engine speed NE increases.

[0011] Further, the cooling water circuit C is provided with a multi-functional valve 22. The multi-functional valve 22 is installed at the cooling water discharge port of the engine 10. The multi-functional valve 22 has three ports, namely a radiator port P1, a first bypass port P2, and a second bypass port P3, as ports for discharging cooling water. Also, the multi-functional valve 22 has a valve body 22A and a motor 22B for driving the valve body 22A. And the multi-functional valve 22 is configured to make the opening ratio of each of the radiator port P1, the first bypass port P2, and the second bypass port P3 variable according to the operation of the valve body 22A. A radiator water passage 23 is connected to the radiator port P1. The radiator water passage 23 is a water passage for flowing cooling water from the radiator port P1 through the radiator 20 to the water pump 21. The first bypass port P2 is connected to a first bypass water passage 24. The first bypass water passage 24 is a water passage for flowing cooling water from the first bypass port P2 through the oil warmer / cooler 26 to the water pump 21. The oil warmer / cooler 26 is a heat exchanger that warms and cools the oil of the manual transmission 11 by heat exchange with the cooling water. A second bypass water passage 25 is connected to the second bypass port P3. The second bypass water passage 25 is a water passage for flowing cooling water from the second bypass port P3 through the throttle body 27 of the engine 10 or the heater core 28 of the air conditioning system to the water pump 21. The air conditioning system warms the air blown into the passenger compartment by heat exchange with the cooling water at the heater core 28, thereby heating the passenger compartment. Incidentally, an electric pump 29 for adjusting the flow rate of the cooling water passing through the heater core 28 is provided in the second bypass water passage 25. The multi-functional valve 22 changes the distribution of the cooling water flowing through each of the radiator water passage 23, the first bypass water passage 24, and the second bypass water passage 25. Incidentally, the multi-functional valve 22 can switch between a state where the water flow through the radiator water passage 23 is blocked and a state where the water flow is allowed by closing / opening the radiator port P1. In the present embodiment, such a multi-functional valve 22 corresponds to the switching valve.

[0012] The engine cooling device also includes an ECU (Electronic Control Unit) 30 as a control unit. The ECU 30 includes an arithmetic processing unit 31 and a memory 32. Programs and data for controlling the engine cooling device are stored in the memory 32. The arithmetic processing unit 31 executes the programs stored in the memory 32 to perform various processes for controlling the engine cooling device. The ECU 30 receives the detection results of various sensors installed in each part of the vehicle. The detection results input to the ECU 30 include the engine speed NE, vehicle speed V, coolant temperature THW, and intake air temperature THA.

[0013] Next, the operation of the multi-functional valve 22 will be described with reference to FIG. 3. FIG. 3 shows the relationship between the operating position of the valve body 22A of the multi-functional valve 22 and the opening ratios of the radiator port P1, the first bypass port P2, and the second bypass port P3. In the figure, "L1" represents the opening ratio of the radiator port P1, "L2" represents the opening ratio of the first bypass port P2, and "L3" represents the opening ratio of the second bypass port P3. The opening ratio represents the ratio of the flow passage area to the maximum flow passage area of the corresponding port. Therefore, each port is closed when the opening ratio is "0", blocking the water flow in the connected water passage. And each port is opened when the opening ratio becomes a value greater than "0", allowing the water flow in the connected water passage.

[0014] A reference position A0, which is the reference operating position of the valve body 22A, is set for the multi-functional valve 22. The operating range of the valve body 22A in the multi-functional valve 22 is divided into a summer use area and a winter use area with the reference position A0 as the boundary. The summer use area is the operating range of the valve body 22A used when the implementation of cabin heating is not assumed. The winter use area is the operating range of the valve body 22A used when the implementation of cabin heating is assumed. The ECU 30 selects the use area used for controlling the multi-functional valve 22 based on, for example, the outside air temperature. Summer and winter in the following description represent the selection times of the summer use area and the winter use area, respectively.

[0015] In FIG. 3, the operating range of the valve body 22A is shown divided into six regions R1 to R6. The reference position A0 is included in the region R3. In the region R3, all of the radiator port P1, the first bypass port P2, and the second bypass port P3 are closed. The region R3 is divided into a summer use region and a winter use region with the reference position A0 as the boundary. The regions R1 and R2 on the left side in the figure from the region R3 are included in the summer use region, and the regions R4 to R6 on the right side in the figure are included in the winter use region. In the region R2, only the first bypass port P2 opens. In the region R1, the radiator port P1 and the first bypass port P2 open. In the region R4, only the second bypass port P3 opens. In the region R5, the first bypass port P2 and the second bypass port P3 open. In the region R6, all of the radiator port P1, the first bypass port P2, and the second bypass port P3 open. When the valve body 22A is located in the regions R2 to R5, the multi-functional valve 22 is in a state of blocking the water flow in the radiator water passage 23. When the valve body 22A is located in the region R1 or the region R6, the multi-functional valve 22 is in a state of allowing the water flow in the radiator water passage 23. In the following description, the operating position of the valve body 22A at which the state of blocking the water flow in the radiator water passage 23 and the state of allowing the water flow are switched is described as the switching position. When the summer use region is selected, "A1" shown in FIG. 3 becomes the switching position. On the other hand, when the winter use region is selected, "A2" shown in FIG. 3 becomes the switching position.

[0016] The ECU 30 drives the motor 22B to adjust the operating position of the valve body 22A according to the cooling requirement of the engine 10 and the heating requirement of the passenger compartment. For example, until the warm-up of the engine 10 is completed, the ECU 30 holds the operating position of the valve body 22A within the range of the regions R2 to R5 and blocks the water flow in the radiator 20 to promote the warm-up of the engine 10. Then, when the warm-up of the engine 10 is completed, the ECU 30 transitions the operating position of the valve body 22A to the region R1 or the region R6 and starts cooling the engine 10 by allowing water to flow through the radiator 20.

[0017] As described above, the engine cooling device of the present embodiment employs a mechanical water pump 21 that operates in response to the rotation of the engine 10. The discharge amount of the cooling water of such a water pump 21 increases as the engine speed NE increases. On the other hand, during warm-up of the engine 10, the flow of water through the radiator water passage 23 is stopped. At this time, the cooling water concentrates and flows through the first bypass water passage 24 and the second bypass water passage 25. If the engine speed NE increases during the interruption of the water flow through the radiator water passage 23, the water pressure in the first bypass water passage 24 and the second bypass water passage 25 may exceed the pressure resistance limits of the hose connectors and the heater core 28 that constitute these water passages.

[0018] When the engine speed NE becomes equal to or higher than a predetermined emergency release rotation speed LIM during the interruption of the water flow through the radiator water passage 23, the ECU 30 opens the radiator port P1 to reduce the water pressure in the first bypass water passage 24 and the second bypass water passage 25. The emergency release rotation speed LIM is set as an upper limit value of the engine speed NE at which the water pressure in the first bypass water passage 24 and the second bypass water passage 25 does not exceed the allowable upper limit in a state where the water flow through the radiator water passage 23 is interrupted. However, it takes a certain amount of time to change the operating position of the valve body 22A of the multi-functional valve 22. Therefore, when the increase rate ΔNE of the engine speed NE is high, even if the opening of the radiator port P1 is commanded when the engine speed NE reaches the emergency release rotation speed LIM, the reduction in water pressure may not be in time. Therefore, the ECU 30 performs an evacuation process of starting the drive of the preliminary valve body 22A while the water pressure is within an allowable range.

[0019] Fig. 4 shows the processing procedure of an evacuation processing routine executed by the ECU 30 for the evacuation process. The ECU 30 repeatedly executes this routine at every predetermined control cycle during the interruption of the water flow through the radiator water passage 23. Incidentally, the "S" before the three-digit numbers in Fig. 4 and the following description represents a step.

[0020] When this routine starts, first at S100, the ECU 30 determines whether or not the gear stage of the auxiliary transmission 19 is set to "4L", which is the low-speed gear stage. Then, when it is set to "4L" (YES), the ECU 30 proceeds to S200, and when it is set to other gear stages, that is, the high-speed gear stage (NO), the ECU 30 proceeds to S110 for processing respectively.

[0021] At S110, the ECU 30 determines whether or not the NV ratio is equal to or greater than a predetermined neutral determination value X0. The NV ratio represents the ratio of the engine speed NE to the vehicle speed V. When the NV ratio is equal to or greater than the neutral determination value X0 (YES), the ECU 30 sets the predetermined low-speed side determination value LO as the value of the retreat determination value X1 at S120. On the other hand, when the NV ratio is less than the neutral determination value X0 (NO), the ECU 30 sets the predetermined high-speed side determination value HI as the value of the retreat determination value X1 at S130. The high-speed side determination value HI is set to a rotation speed higher than the low-speed side determination value LO and lower than the above-mentioned emergency release rotation speed LIM. Then, after the processing of S120 or S130, the ECU 30 proceeds to S150 for processing.

[0022] At S150, the ECU 30 calculates the value of the second retreat determination value X2 based on the engine speed NE. The ECU 30 calculates the second retreat determination value X2 with reference to the map MAP1 stored in the memory 32. The map MAP1 is configured as a hash table that takes, for example, the engine speed NE as the input value and returns the second retreat determination value X2. Fig. 5 shows the relationship between the engine speed NE and the second retreat determination value X2 in the map MAP1. As shown in Fig. 5, the second retreat determination value X2 is calculated as a value that gradually decreases as the engine speed NE increases. More specifically, the second retreat determination value X2 is calculated so as to be proportional to the difference between the engine speed NE and the emergency release rotation speed LIM. Next, at S160, the ECU 30 determines whether or not the engine speed NE is equal to or greater than the retreat determination value X1 and the rising speed ΔNE is equal to or greater than the second retreat determination value X2. Then, when the ECU 30 makes an affirmative determination at S160 (YES), it proceeds to S200, and when it makes a negative determination (NO), it proceeds to S170 for processing respectively.

[0023] At S170, the ECU 30 determines whether the engine 10 is in an idle operation. The idle operation is the operation of the engine 10 when the shaft torque output by the engine 10 to the outside is "0". Then, when the ECU 30 is in the idle operation (YES), the process proceeds to S180. On the other hand, when it is not in the idle operation (NO), the ECU 30 ends the process of this routine in the current control cycle. At S180, the ECU 30 calculates a third retreat determination value X3 based on the vehicle speed V. The ECU 30 calculates the third retreat determination value X3 with reference to the map MAP2 stored in the memory 32. The map MAP2 is configured as a hash table that takes, for example, the vehicle speed V as an input value and returns the third retreat determination value X3. Fig. 6 shows the relationship between the vehicle speed V and the third retreat determination value X3 in the map MAP2. In the present embodiment, a value that is inversely proportional to the vehicle speed V is calculated as the value of the third retreat determination value X3. More specifically, a value equal to the quotient obtained by dividing a predetermined rotational speed NX (described later) by the vehicle speed V is calculated as the value of the third retreat determination value X3. Next, at S190, the ECU 30 determines whether the engine rotational speed NE is equal to or greater than the third retreat determination value X3. Then, when the state where the engine rotational speed NE is equal to or greater than the third retreat determination value X3 continues for a predetermined time (YES), the process proceeds to S200. On the other hand, when the engine rotational speed NE is less than the third retreat determination value X3 (NO), the ECU 30 ends the process of this routine in the current control cycle.

[0024] On the other hand, in S200, the ECU 30 commands the multi-functional valve 22 to drive the valve body 22A to the switching position A1 or A2. That is, in summer, it commands the drive to the switching position A1, and in winter, it commands the drive to the switching position A2. Then, after the command, the ECU 30 ends the processing of this routine in the current control cycle. In this embodiment, the processing of S200 corresponds to the retraction process of commanding the drive of the valve body 22A in the direction where the switching positions A1 and A2 are located as viewed from the current operating position. When the retraction process starts, the operating amount of the valve body 22A up to the switching positions A1 and A2 approaches "0". By performing the retraction process, the ECU 30 shortens in advance the time required for the opening of the radiator port P1 in preparation for the increase in water pressure.

[0025] <Function and Effect of the Embodiment> The operation and effect of this embodiment will be described. In the drive system of the vehicle shown in FIG. 1, the torque transmission path between the engine 10 and the drive shafts 13 and 14 is disconnected or connected by the operation of the user's shift lever or clutch pedal. In the following description, the state in which the torque transmission path is disconnected is described as the neutral state of the drive system, and the state in which the torque transmission path is connected is described as the connected state of the drive system.

[0026] When the accelerator pedal is depressed and the engine output increases, the engine speed NE rises. When the drive system is in the neutral state, the engine speed NE is more likely to rise than when it is in the connected state. Therefore, when the drive system is in the neutral state, it is necessary to start the retraction operation of the multi-functional valve 22 at an earlier time than when it is in the connected state. On the other hand, the gear ratio of the drive system when the drive system is in the connected state is determined by the respective gear positions of the manual transmission 11 and the auxiliary transmission 19. That is, the NV ratio when the drive system is in the connected state is determined by the respective gear positions of the manual transmission 11 and the auxiliary transmission 19. On the other hand, since the NV ratio when the drive system is in the neutral state is indefinite, it may become a large value that cannot be obtained when the drive system is in the connected state. Therefore, when the NV ratio is larger than a certain value, it can be determined that there is a high possibility that the drive system is in the neutral state. In contrast, in S110 to S130 of the retraction processing routine, the ECU 30 sets a lower rotation speed as the value of the retraction determination value X1 when the NV ratio is equal to or greater than the neutral determination value X0 than when it is less than the neutral determination value X0.

[0027] Furthermore, the ECU 30 sets the second retraction determination value X2 as a value that decreases as the engine speed NE increases in S150. Then, in S160, when it is determined that the engine speed NE is equal to or greater than the retraction determination value X1 and the rising speed ΔNE is equal to or greater than the second retraction determination value X2, the ECU 30 commands the retraction operation of the multi-functional valve 22. In this embodiment, in this embodiment, the processing of S110 to S130 in the retraction processing routine corresponds to a change process of changing the retraction determination value X1 so that it becomes a smaller value when the NV ratio, which is the ratio of the engine speed NE to the vehicle speed V, is large than when it is small. Also, in this embodiment, the processing of S150 in the retraction processing routine corresponds to a setting process of setting a higher speed as the value of the second retraction determination value X2 when the engine speed NE is high than when the same engine speed NE is low.

[0028] In this embodiment, when the NV ratio is large and there is a high possibility that the drive system is in a neutral state, the retreat operation is more likely to start at a lower engine speed NE than in other cases. Therefore, the retreat operation of the multifunctional valve 22 can be started at an appropriate timing according to the difference in the ease of increase in the engine speed NE between the neutral state and the connected state of the drive system. Further, in this embodiment, the higher the increase rate ΔNE of the engine speed NE, the earlier the retreat operation starts at a lower engine speed NE. Therefore, the retreat operation of the multifunctional valve 22 can be started at an appropriate timing according to the increase rate ΔNE of the engine speed NE.

[0029] On the other hand, the engine 10 during vehicle deceleration is in an idling operation state where it does not generate shaft torque. Also, the engine 10 during vehicle deceleration is further in a state of being rotated according to the rotation of the wheels. When the user performs a downshift operation of the manual transmission 11 during such vehicle deceleration, the engine speed NE may increase rapidly. In contrast, in S180 of the retreat processing routine, the ECU 30 calculates a value equal to the quotient obtained by dividing the above-mentioned predetermined rotational speed NX by the vehicle speed V as the value of the third retreat determination value X3. The maximum value in the normal use range of the engine speed NE during vehicle deceleration is set for the rotational speed NX. The normal use range represents the range of values that the engine speed NE can take when the vehicle decelerates while maintaining the gear position of the manual transmission 11. Therefore, when the engine speed NE becomes "NX" or higher during vehicle deceleration, that is, when the NV ratio becomes equal to or higher than the third retreat determination value X3, it can be determined that there is a high possibility that the downshift operation of the manual transmission 11 has been performed. And the ECU 30 also commands the retreat operation of the multifunctional valve 22 when the NV ratio becomes equal to or higher than the third retreat determination value X3 during idling operation (S170: YES and S190: YES). Therefore, when it is predicted that the engine speed NE may exceed the emergency release rotational speed LIM thereafter due to the downshift operation of the manual transmission 11 by the user during vehicle deceleration, the retreat operation of the multifunctional valve 22 is performed.

[0030] Incidentally, when the user of the vehicle performs driving that requires a large driving force on a steep slope or on a rocky mountain, etc., the gear stage of the auxiliary transmission 19 is set to "4L", which is a low-speed gear stage. In such driving, the engine speed NE is likely to increase significantly. In contrast, in the retreat process routine, when the gear stage of the auxiliary transmission 19 is set to the low-speed gear stage (S100: YES), the ECU 30 performs the retreat operation of the multi-functional valve 22.

[0031] <Other Embodiments> This embodiment can be implemented with the following modifications. This embodiment and the following modification examples can be implemented in combination with each other within a range where there is no technical contradiction.

[0032] · The process of S100 in the retreat process routine of FIG. 4 may be omitted. That is, the retreat operation of the multi-functional valve 22 may not be performed when the auxiliary transmission 19 is set to the low-speed gear stage. Also, the processes of S170 to S190 in the retreat process routine of FIG. 4 may be omitted. That is, the retreat operation of the multi-functional valve 22 may not be performed when the engine speed NE becomes equal to or higher than the predetermined speed NX during vehicle deceleration. Further, the processes of S150 and S160 in the retreat process routine of FIG. 4 may be omitted. That is, the determination of performing the retreat operation based on the increase speed ΔNE of the engine speed NE may be omitted.

[0033] · The change of the retreat determination value X1 according to the NV ratio may be performed in three or more steps. Also, the retreat determination value X1 may be continuously changed according to the NV ratio. · In the retreat process, the driving of the valve body 22A to a position closer to the current operating position than the switching positions A1 and A2 may be commanded. Also, in the retreat process, the driving of the valve body 22A to a position farther from the current operating position than the switching positions A1 and A2 may be commanded.

[0034] · The configuration of the cooling water circuit C of the engine cooling device may be changed as appropriate. Specifically, as long as it includes a mechanical water pump, a radiator water passage passing through the radiator, a bypass water passage bypassing the radiator, and a switching valve, the cooling water circuit may have a configuration different from that shown in FIG. 2. Further, the engine cooling device of the above embodiment is applicable to a vehicle having a drive system other than the configuration shown in FIG. 1 as long as the engine and the wheels are connected via a manual transmission capable of manually switching gear stages.

Explanation of Signs

[0035] 10… Engine, 11… Manual transmission, 12… Transfer, 13, 14… Drive shaft, 15, 17… Differential, 16… Front wheel, 18… Rear wheel, 19… Auxiliary transmission, 20… Radiator, 21… Water pump, 22… Multi-functional valve (22A… Valve body, 22B… Motor), 23… Radiator water passage, 24… First bypass water passage, 25… Second bypass water passage, 26… Oil warmer / cooler, 27… Throttle body, 28… Heater core, 29… Electric pump, 30… ECU, 31… CPU, 32… Memory, C… Cooling water circuit

Claims

1. An engine cooling device that cools an engine connected to wheels via a manual transmission capable of manual gear shifting, comprising a cooling water circuit that circulates cooling water through the engine, and a control unit, wherein the cooling water circuit includes a mechanical water pump that operates in response to the rotation of the engine, a radiator water passage that passes through a radiator, a bypass water passage that bypasses the radiator, and a switching valve that switches between a state of blocking the water flow through the radiator water passage and a state of allowing the water flow, wherein the control unit performs a retreat process of commanding the drive of the valve body in the direction in which the switching position is located as viewed from the current operating position when the engine speed becomes equal to or higher than a retreat determination value during the blocking of the water flow through the radiator water passage, and a change process of changing the retreat determination value so as to be a smaller value when the NV ratio, which is the ratio of the engine speed to the vehicle speed, is large than when the NV ratio is small, wherein the switching position is the operating position of the valve body at which the state of blocking the water flow and the state of allowing the water flow are switched, an engine cooling device.

2. wherein the control unit performs a setting process of setting a higher speed as the value of a second retreat determination value when the engine speed is high than when the engine speed is low, wherein the retreat process is a process of commanding the drive of the valve body in the direction in which the switching position is located as viewed from the current operating position when the engine speed becomes equal to or higher than the retreat determination value and the rising speed of the engine speed becomes equal to or higher than the second retreat determination value, The engine cooling device according to claim 1.

3. The engine cooling device according to claim 1, wherein the retreat process is also a process of commanding the drive of the valve body in the direction in which the switching position is located as viewed from the current operating position when the NV ratio becomes equal to or higher than a predetermined value during vehicle deceleration.

4. The vehicle equipped with the engine includes an auxiliary transmission having a low-speed gear stage and a high-speed gear stage provided between the manual transmission and the wheels, wherein the retreat process is also a process of commanding the drive of the valve body in the direction in which the switching position is located as viewed from the current operating position when the gear stage of the auxiliary transmission is set to the low-speed gear stage, The engine cooling device according to claim 1.

5. The cooling device for an engine according to any one of claims 1 to 4, wherein the retreat process is a process of commanding driving of the valve body to the switching position.

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