JP2023002175A - cooling system - Google Patents

Abstract

To provide a cooling system capable of further promoting warming-up of an internal combustion engine while preventing local boiling of cooling water.SOLUTION: A cooling system X includes: a pump P; a first flow channel 11, which is a route through which cooling water circulates to an upper region of a cylinder head Ea; a second flow channel 12, which is a route through which cooling water circulates to a lower region of the cylinder head Ea; a third flow channel 14, which is a route through which cooling water circulates to the inside of a cylinder block Eb; a first valve FSV disposed on the route of the second flow channel 12; a second valve V disposed on the route of the third flow channel 14; a communication passage 15 for circulating cooling water between the inside of the cylinder head Ea and the inside of the cylinder block Eb; and a control part 5 for executing opening/closing control of the first valve FSV and the second valve V.SELECTED DRAWING: Figure 1

Description

The present invention relates to a cooling system for cooling an internal combustion engine with cooling water.

Conventionally, a two-system cooling system capable of separately cooling a cylinder block and a cylinder head of an internal combustion engine is known (see, for example, Patent Document 1).

The cooling system described in Patent Document 1 has a first state in which cooling water flows only into the cylinder head during warm-up operation, and a first state in which the entire amount of cooling water flows into the cylinder head through the cylinder block after the end of warm-up operation. and a second state. As a result, during warm-up operation, the flow of water into the cylinder block is stopped to promote warm-up.

JP 2015-190450 A

The cooling system disclosed in Patent Document 1 circulates the cooling water only in the cylinder head during warm-up, so the temperature rise of the cooling water remaining in the cylinder block is accelerated. At this time, the cooling water flowing through the cylinder head suppresses the temperature rise of the cooling water staying in the cylinder block to some extent. is insufficient. In other words, in the technique described in Patent Literature 1, it was necessary to quickly shift from the first state to the second state in order to prevent this local boiling. As a result, the promotion of warm-up of the internal combustion engine becomes insufficient.

Therefore, there is a demand for a cooling system that can further promote warm-up of the internal combustion engine while preventing local boiling of the cooling water.

The characteristic configuration of the cooling system according to the present invention includes a pump that circulates cooling water in the internal combustion engine, a first flow path that is a route through which the cooling water flows to the upper region of the cylinder head by the driving force of the pump, and the pump a second flow path through which the cooling water circulates to the lower region of the cylinder head by the driving force of the pump; and a third flow path through which the cooling water circulates inside the cylinder block by the driving force of the pump. and between a first valve arranged on the path of the second flow path, a second valve arranged on the path of the third flow path, and between the inside of the cylinder head and the inside of the cylinder block and a control unit for controlling the opening and closing of the first valve and the second valve.

The cooling system of this configuration includes a first flow path for circulating cooling water in the upper region of the cylinder head, a second flow path for circulating cooling water in the lower region of the cylinder head, and a flow path for circulating cooling water inside the cylinder block. It has three routes with the third flow channel. Also, a first valve is provided in the second flow path, and a second valve is provided in the third flow path, so that cooling water can flow between the cylinder head and the cylinder block through the communication path.

From this configuration, by closing the first valve and the second valve during warm-up, if the cooling water is circulated only in the first flow path that is the upper region of the cylinder head, the cooling water that stays inside the cylinder block Since the degree to which water is cooled indirectly through the communication passage is reduced, warming up can be accelerated. In addition, if the first valve is opened when the temperature of the cooling water in the communication passage where local boiling is likely to occur inside the cylinder block rises, the second flow becomes the lower region of the cylinder head located near the communication passage. Cooling water can be passed through the passages to prevent local boiling. Furthermore, even if the temperature of the cooling water in the communication passage rises to just before boiling, opening the second valve enables the cooling water to spread inside the cylinder block and prevent local boiling. It is possible to prevent local boiling of the cooling water while promoting machine operation. In this manner, this configuration provides a cooling system that can further promote warm-up of the internal combustion engine while preventing local boiling of the cooling water.

Another configuration is that the control unit changes the first valve from closed to open when the temperature of the cooling water flowing through the communication passage becomes equal to or higher than a first threshold value.

As in this configuration, the first valve is closed when the temperature of the coolant in the communication passage, where local boiling is likely to occur inside the cylinder block, is less than the first threshold, thereby promoting warm-up. If the first valve is opened when the threshold value is equal to or higher than one threshold value, the cooling water is allowed to flow through the second passage, which is the lower region of the cylinder head located near the communication passage, thereby preventing local boiling of the cooling water. be able to.

As another configuration, the control unit changes the second valve from closed to open when the temperature of the cooling water flowing through the communication path becomes equal to or higher than a second threshold that is larger than the first threshold. It is in the point to do.

As in this configuration, the second valve is closed when the temperature of the coolant in the communication passage, where local boiling is likely to occur inside the cylinder block, is less than the second threshold, and when the temperature reaches or exceeds the second threshold. If the second valve is opened immediately, it is possible to spread the cooling water inside the cylinder block and prevent local boiling. Since this second threshold is greater than the first threshold, it is possible to accelerate the warm-up up to the critical point where local boiling of the cooling water occurs.

As another configuration, the control unit changes the first valve and the second valve from closed to open when the temperature of the cooling water flowing through the communication passage reaches or exceeds a predetermined temperature. be.

As in this configuration, the first valve and the second valve are closed when the temperature of the cooling water in the communication passage, in which local boiling tends to occur inside the cylinder block, is lower than the predetermined temperature, and the temperature rises to the predetermined temperature or higher. If the first valve and the second valve are opened at the same time, the cooling water is circulated in the second flow path, which is the lower region of the cylinder head located near the communication path, and the cooling water flows inside the cylinder block. can be distributed to reliably prevent local boiling.

Another configuration is that the control unit duty-controls the opening and closing time of the second valve.

By duty-controlling the opening/closing time of the second valve as in this configuration, the amount of cooling water flowing through the inside of the cylinder block can be adjusted according to the degree of occurrence of local boiling of the cooling water. As a result, warm-up can be promoted without cooling the cylinder block more than necessary.

Another configuration is to further include a third valve arranged on the path of the first flow path.

If a third valve is provided in the first flow path as in this configuration, it is possible to create a state in which cooling water is not circulated inside the cylinder head or a state in which a small amount of cooling water is circulated inside the cylinder head. Therefore, the warm-up can be further accelerated.

Another configuration is that the pump is a mechanical pump, and the control section changes the valve opening time of the second valve according to the rotational speed of the internal combustion engine.

As in this configuration, in the case of a mechanical pump, if the opening time of the second valve is changed according to the rotation speed of the internal combustion engine, an appropriate amount of cooling water can be circulated according to the driving force of the pump. can be done.

As another configuration, the pump is an electric pump, and the control unit performs duty control so that the discharge amount of the pump is smaller when the second valve is opened than when the second valve is closed. It is in the point to do.

As in this configuration, in the case of an electric pump, if the duty is controlled so that the discharge amount of the pump becomes small when the second valve is opened, it is possible to prevent local boiling of the cooling water while promoting warm-up operation. can.

As another configuration, the control unit closes the first valve and the second valve after the internal combustion engine stops after the warm-up operation of the internal combustion engine is completed, and closes the first valve and the second valve when restarting the internal combustion engine. It lies in opening the first valve.

As in this configuration, if the first valve and the second valve are closed after the internal combustion engine stops after the end of the warm-up operation, cooling of the internal combustion engine can be prevented and fuel consumption can be improved. When one valve is opened, the coolant temperature of the cylinder block is made uniform by circulating the coolant through the second channel, which is the lower region of the cylinder head located near the communication channel. local boiling can be prevented.

1 is a circuit configuration diagram of a cooling system according to a first embodiment; FIG. 1 is a conceptual diagram of an internal combustion engine; FIG. 4 is a control flowchart of the cooling system; FIG. 4 is a circuit configuration diagram at the start of warm-up operation; 4 is a circuit configuration diagram during warm-up operation; FIG. It is a circuit block diagram after completion|finish of warm-up operation. It is an example of the opening-and-closing control of a 1st valve. It is a circuit configuration diagram of a cooling system according to a second embodiment. FIG. 11 is a circuit configuration diagram of a cooling system according to a third embodiment; It is an example of opening and closing control of the second valve in the case of a mechanical pump. It is an example of duty control of an electric pump.

EMBODIMENT OF THE INVENTION Below, embodiment of the cooling system which concerns on this invention is described based on drawing. However, without being limited to the following embodiments, various modifications are possible without departing from the scope of the invention.

[First embodiment]
As shown in FIG. 1, the cooling system X includes an engine E as an internal combustion engine, a pump P that circulates cooling water (coolant) in the engine E, a heater core that generates hot air in the vehicle, and cooling oil such as ATF. A heat exchanger 2 composed of an oil cooler or an EGR cooler, etc., a radiator 3, a thermostat valve 4, a fluid control valve FSV (an example of a first valve), and a solenoid valve V (an example of a second valve) , and a controller 5 for controlling the opening and closing of at least the fluid control valve FSV and the solenoid valve V. As shown in FIG.

The engine E has a cylinder head Ea with adjacent combustion chambers (not shown) and a cylinder block Eb that houses the piston 1 (see also FIG. 2). A shaft sensor Sb for detecting the number of revolutions of the engine E is provided near a crankshaft (not shown) of the engine E. As shown in FIG. Further, an intake manifold (not shown) of the engine E is provided with an airflow meter Sc for detecting the amount of intake air.

The pump P is composed of a mechanical water pump that rotates in conjunction with the rotation of the crankshaft of the engine E, or an electric water pump that rotates with the driving force of an electric motor.

The thermostat valve 4 maintains a closed state when the temperature of the cooling water is less than a set temperature (eg, 80 to 90° C.), and switches to an open state when the water temperature is equal to or higher than the set temperature. type valve.

The fluid control valve FSV is provided with a valve body that opens under the fluid pressure of the cooling water and closes by coming into contact with the valve seat by the electromagnetic force opposing the fluid pressure and the urging force of the coil spring (for example, , see JP-A-2017-31910). The fluid control valve FSV does not require electric power control because it is opened by receiving fluid pressure. When the fluid pressure is low, the valve is closed by the biasing force of the coil spring, thereby saving power consumption. ing. Note that the fluid control valve FSV is not particularly limited and may be composed of an electromagnetic valve or the like as long as it can be switched between a closed valve state that closes the flow path and an open valve state that opens the flow path.

The electromagnetic valve V is an ON/OFF opening/closing valve that can be switched between a closed state in which the flow path is closed and an open state in which the flow path is opened by an electromagnetic force. The solenoid valve V is configured such that the valve closing time and the valve opening time can be adjusted by duty control. It should be noted that the electromagnetic valve V may not be configured as an ON/OFF opening/closing valve, but may be configured as a proportional valve whose opening can be adjusted by changing the current value.

The control unit 5 is configured as an ECU (engine control unit), and controls the fluid control valve FSV and the solenoid valve based on the rotational speed of the engine E obtained from the shaft sensor Sb and the amount of intake air measured by the airflow meter Sc. Controls opening and closing of V.

The cooling system X includes a first flow path 11, which is a path through which cooling water circulates to the upper region of the cylinder head Ea by the driving force of the pump P, and a cooling water circulates to the lower region of the cylinder head Ea by the driving force of the pump P. A second flow path 12, which is a path, and a third flow path 14, which is a path through which cooling water flows inside the cylinder block Eb by the driving force of the pump P, are provided. Further, the first flow path 11 branches into a first branch path 11a and a second branch path 11b on the downstream side of the cylinder head Ea. The second branch path 11b is a path through which cooling water circulates from the upper area of the cylinder head Ea to the engine E by the driving force of the pump P. be part of Furthermore, the cooling system X includes a confluence channel 13 where the first channel 11 and the second channel 12 join on the upstream side of the pump P. As shown in FIG.

The upper region of the cylinder head Ea, the radiator 3 and the thermostat valve 4 are arranged in this order in the first branch passage 11a of the first flow passage 11 along the flow direction of the cooling water. In the second flow path 12, the lower region of the cylinder head Ea, the fluid control valve FSV, and the heat exchanger 2 are arranged in this order along the circulation direction of the cooling water. A junction 13 of the second branch 11b of the first flow path 11 and the second flow path 12 bypasses the temperature sensing portion (not shown) of the thermostat valve 4, and the thermostat valve 4 is detected to open the set temperature. In other words, flow control valves such as the fluid control valve FSV and the electromagnetic valve V are not provided on the paths of the second branch passage 11b and the merging passage 13 . A water temperature sensor Sa for measuring the temperature of the cooling water is provided on the outlet side of the cylinder head Ea of the first flow path 11 .

A solenoid valve V and a cylinder block Eb are arranged in this order in the third flow path 14 along the flow direction of the cooling water. This solenoid valve V is provided between the thermostat valve 4 and the cylinder block Eb. The third flow path 14 in this embodiment communicates the downstream side of the thermostat valve 4 with the cylinder block Eb, and communicates with the combined flow path 13 . The third flow path 14 bypasses the upstream side of the cylinder head Ea and the downstream side of the heat exchanger 2, the radiator 3 and the thermostat valve 4, and passes through the cylinder block Eb.

A heater core, an oil cooler, an EGR cooler, or the like may be arranged in the second branch passage 11b of the first flow passage 11. FIG. In addition, the heat exchanger arranged in the second flow path 12 is not limited to a heater core, an oil cooler, or an EGR cooler. It is not particularly limited.

With such a flow path configuration, on the downstream side of the cylinder head Ea, the fluid control valve FSV and the heat exchanger 2 arranged in the second flow path 12 and the first branch path 11a of the first flow path 11 are arranged. The radiator 3 and the thermostat valve 4 are arranged in parallel, respectively, and in the joint channel 13 where the second channel 12 and the first channel 11 join, downstream of the connection part with the first branch channel 11a The third channel 14 is in communication. In addition, the pump P may be provided on the outlet side of the cylinder head Ea, and is not particularly limited.

As shown in FIG. 2, the cooling system X includes a communication passage 15 for circulating cooling water between the inside of the cylinder head Ea and the inside of the cylinder block Eb. As described above, the first flow passage 11 is formed in the upper region of the cylinder head Ea, and the second flow passage 12 is formed in the lower region of the cylinder head Ea. A portion of the flow path 12 communicates with the water jacket of the cylinder head Ea. The communication path 15 connects the water jacket of the cylinder head Ea that forms the second flow path 12 and the water jacket of the cylinder block Eb that forms the third flow path 14 .

The communication path 15 is composed of a first drill pass 15a formed in the cylinder head Ea and a second drill pass 15b formed in the cylinder block Eb. Peripheries of the first drill pass 15a and the second drill pass 15b are sealed by a seal member S arranged at the boundary between the cylinder head Ea and the cylinder block Eb. As described above, the first flow path 11 and the second flow path 12 are partially communicated in the cylinder head Ea. It is smaller than the passage diameter of the communication passage 15 (the first drill pass 15a and the second drill pass 15b) of the third passage 14. That is, the second flow path 12 and the third flow path 14 are directly communicated by the communication path 15, and the first flow path 11 and the third flow path 14 are connected by the second flow path 12 and the first flow path. 11 and the small-diameter communication path of the second flow path 12, and communicates indirectly by the communication path 15. As shown in FIG.

[Control mode]
An example of the control mode of the cooling system X according to the present embodiment will be described below with reference to FIGS. 3 to 7. FIG.

When the engine E is started, cranking is started to operate the pump P, and cooling water begins to flow through the first flow path 11 (second branch path 11b) passing through the upper region of the cylinder head Ea. At this time, if the cooling water temperature measured by the water temperature sensor Sa provided on the outlet side of the cylinder head Ea of the first flow path 11 is the first temperature T1 (for example, 80° C.) or lower (#31 Yes in FIG. 3), Under the control of the control unit 5, the fluid control valve FSV is energized and the solenoid valve V is not energized, so that the fluid control valve FSV and the solenoid valve V (all valves) are closed (#32 in FIG. 3, FIG. 4). state). When the engine E is started, the temperature of the cooling water is low and the thermostat valve 4 is closed. Thereby, the cooling water flows through the second branch passage 11b branched from the first passage 11 and the combined passage 13, and is heated by the upper region of the cylinder head Ea. In this way, by closing the fluid control valve FSV and the solenoid valve V during warm-up operation, the cooling water is allowed to flow only through the first flow path 11 passing through the upper region of the cylinder head Ea. The degree to which the cooling water staying inside is indirectly cooled through the communication passage 15 is reduced, and the warm-up of the cylinder block Eb can be accelerated.

On the other hand, when the cooling water temperature measured by the water temperature sensor Sa is higher than the first temperature T1 (#31 No in FIG. 3), such as when the engine E is running after warming up, the control unit 5 controls , the solenoid valve V and the fluid control valve FSV are opened as necessary, and the driving force of the pump P circulates the cooling water.

When the fluid control valve FSV and the solenoid valve V are closed, the controller 5 determines whether or not the temperature of the communication passage 15 has reached or exceeded a second temperature T2 (an example of the first threshold value, for example 120° C.). (#33 in FIG. 3). Here, when the communication path 15 is provided with a temperature sensor, the cooling water temperature of the communication path 15 (an example of the temperature of the communication path 15) can be used. In the present embodiment, assuming that no temperature sensor is provided in the communication path 15, the estimated temperature of the communication path 15 (an example of the temperature of the communication path 15) is determined in advance based on any of the following estimated temperature maps: can be calculated using If there are multiple arguments, any or all of the arguments are used to create the estimated temperature map.
(1) Current cooling water temperature measured by water temperature sensor Sa (2) Cooling water temperature when engine E started measured by water temperature sensor Sa, and accumulated air amount after engine E started (3) Water temperature sensor Sa The cooling water temperature measured by the engine E starting, the accumulated air amount after the engine E starting, and the current cooling water temperature measured by the water temperature sensor Sa (4) When the engine E started measured by the water temperature sensor Sa cooling water temperature, accumulated air amount after engine E start, and pump P rotation speed Temperature and integrated air volume after re-opening of the fluid control valve FSV *The integrated air volume is calculated by adding the intake air volume measured by the air flow meter Sc or the like.

In the estimated temperature map of (1) above, since the cooling water in the communication passage 15 is indirectly cooled by the cooling water flowing through the cylinder head Ea, a certain degree of correlation with the cooling water temperature at the outlet of the cylinder head Ea is obtained. . In the estimated temperature map of (2) above, since the coolant temperature in the communication passage 15 rises in proportion to the combustion energy of the engine E, the coolant temperature at engine E start is proportional to the integrated air amount after engine E start. As a result, the temperature of the cooling water in the communication passage 15 rises. In the estimated temperature map of (3) above, the estimation accuracy is enhanced by the correlation in which the above (1) and (2) are superimposed. In the estimated temperature map of (4) above, in addition to the correlation of (2) above, due to the circulation amount of cooling water proportional to the rotation speed of the pump P, the heat in the communication passage 15 between the cylinder head Ea and the cylinder block Eb Since the income and expenditure can be predicted, the estimation accuracy increases. In (5) above, when the fluid control valve FSV is opened and closed, the current cooling water temperature measured by the water temperature sensor Sa may be high. can. In addition, the integrated fuel injection amount of the engine E, the rotation speed of the engine E, the measured value of the air-fuel ratio sensor, etc. may be used as arguments.

Returning to FIG. 3, when the temperature of the communication passage 15 becomes equal to or higher than the second temperature T2 (eg, 120° C.) (#33 Yes in FIG. 3), the control unit 5 stops energizing the fluid control valve FSV, The fluid pressure of the cooling water opens the fluid control valve FSV (#34 in FIG. 3, state in FIG. 5). In this manner, since the fluid control valve FSV is opened when the temperature of the cooling water in the communication passage 15, which is likely to cause local boiling inside the cylinder block Eb, rises, the cylinder head located near the communication passage 15 It is possible to prevent local boiling of the cooling water by circulating the cooling water in the second flow path 12 which is the lower region of Ea. Moreover, since cooling water does not flow through the cylinder block Eb, warm-up is promoted.

Next, when the temperature of the communication passage 15 becomes lower than the second temperature T2 (second temperature T2-α) (for example, 110° C.) (#35 Yes in FIG. 3), the control unit 5 controls the fluid control valve FSV is resumed to close the fluid control valve FSV (#36 in FIG. 3). This promotes warm-up without excessively cooling the cylinder block Eb by the cooling water flowing in the lower region of the cylinder head Ea.

FIG. 7 shows an example of duty control of the fluid control valve FSV. As shown in the figure, by duty-controlling the opening/closing time of the fluid control valve FSV, while preventing local boiling of the communication passage 15, the low-temperature region (for example, the lower part of the block) of the cylinder block Eb is warmed up to the target warm-up temperature. It can be increased step by step. That is, in the present embodiment, by providing the fluid control valve FSV for duty control in the second flow path 12, it is possible to increase the temperature of the cooling water in the low temperature region of the cylinder block Eb. The temperature is uniformed, and warm-up can be accelerated. By duty-controlling the opening/closing time of the fluid control valve FSV in this way, the amount of cooling water flowing inside the cylinder block Eb can be adjusted according to the degree of occurrence of local boiling of the cooling water. As a result, warm-up can be promoted without cooling the cylinder block Eb more than necessary.

On the other hand, if the temperature of the communication path 15 becomes a third temperature T3 (an example of the second threshold value, for example, 150° C.) higher than the second temperature T2 (#37 Yes in FIG. 3), the control of the control unit 5 energizes the solenoid valve V to open it (#38 in FIG. 3, state in FIG. 6). At this time, as shown in FIG. 6, the fluid control valve FSV may be closed, or may be opened as necessary. In this way, when the temperature of the cooling water in the communication passage 15 rises to the limit, opening the solenoid valve V allows the cooling water to spread inside the cylinder block Eb and prevent local boiling of the cooling water. becomes.

Then, when the temperature of the communication passage 15 becomes lower than the third temperature T3 (third temperature T3-β) (for example, 120° C.) (#39 Yes in FIG. 3), the control unit 5 controls the solenoid valve V is stopped to close the valve (#40 in FIG. 3, state in FIG. 5). As a result, even if the temperature of the communicating path 15 becomes equal to or higher than the third temperature T3, local boiling of the cooling water is prevented, and when the temperature of the communicating path 15 becomes less than (the third temperature T3-β), Warming up can be accelerated by closing the solenoid valve V again. In this manner, when the temperature of the cooling water in the communication passage 15, which is likely to cause local boiling inside the cylinder block Eb, is lower than the third temperature T3, the solenoid valve V is closed, and the temperature rises to the third temperature T3 or higher. If the solenoid valve V is opened at this time, the cooling water can be distributed inside the cylinder block Eb to prevent local boiling of the cooling water. Since this third temperature T3 is higher than the second temperature T2, it is possible to accelerate the warm-up up to the limit point where local boiling of the cooling water occurs. If the fluid control valve FSV is closed when the solenoid valve V is closed at #40 in FIG. 3, as shown in FIG. may be stopped and the fluid control valve FSV may be opened by the fluid pressure of the cooling water.

Next, when the engine E stops (#41 Yes in FIG. 3), such as when the engine E stops idling after the end of the warm-up operation, the control unit 5 controls the fluid control valve FSV and the solenoid valve V (all valves ) is closed to prevent excessive cooling of the engine E (#42 in FIG. 3, state in FIG. 4). As a result, the engine E is not cooled more than necessary, and the fuel efficiency at restart can be improved. Next, when the engine E is restarted after being stopped (#43 Yes in FIG. 3), the control unit 5 stops energizing the fluid control valve FSV, and only the fluid control valve FSV is opened by the fluid pressure of the cooling water. valve (#44 in FIG. 3, state in FIG. 5). As a result, the cooling water flows through the second flow passage 12, which is the lower region of the cylinder head Ea located near the communication passage 15, and the temperature of the cooling water in the cylinder block Eb is made uniform. Next, at a predetermined timing, the electromagnetic valve V is energized and opened under the control of the controller 5 (#45 in FIG. 3, state in FIG. 6). As a result, it is possible to spread the cooling water inside the cylinder block Eb and prevent local boiling of the cooling water. At this time, if necessary, the fluid control valve FSV may be energized and closed by the control of the control unit 5, or the valve may be maintained in the open state and the cooling water may be circulated through the second flow path 12 as well. Also good.

Only the configurations of other embodiments that are different from the above-described first embodiment will be described below. In addition, in order to facilitate the explanation, the same member names and symbols are used for the same members.

[Second embodiment]
As shown in FIG. 8, the cooling system X may further include a fluid control valve FSV (an example of a third valve) arranged on the path of the second branch 11b of the first flow path 11. As shown in FIG. If the second branch passage 11b of the first flow passage 11 is also provided with the fluid control valve FSV in this manner, it is possible to create a state in which the cooling water is not circulated inside the cylinder head Ea. can be further promoted. Further, the second flow path 12 may be branched into the third branched path 12a and the fourth branched path 12b on the downstream side of the cylinder head Ea. In this case, the third branch passage 12a becomes a part of the passage through which the cooling water is circulated from the lower region of the cylinder head Ea to the fluid control valve FSV, the heat exchanger 2, and the engine E by the driving force of the pump P. The branch passage 12b is a part of a passage through which cooling water is circulated from the lower region of the cylinder head Ea to the engine E by the driving force of the pump P. By providing the fourth branch passage 12b in this way, by closing the fluid control valves FSV of the second branch passage 11b and the third branch passage 12a, a small amount of cooling water is circulated only in the lower region of the cylinder head Ea. Since it is possible to create a state in which the cooling water is allowed to warm up, the warm-up can be promoted while reliably preventing local boiling of the cooling water.

[Third embodiment]
As shown in FIG. 9, the cooling system X further includes a heat exchanger 2 arranged on the downstream side (between the third flow path 14 and the engine E) of the combined flow path 13 from the pump P. can be When the engine E is started, cranking is started and the pump P is operated, and cooling water begins to flow through the first flow path 11 (second branch path 11b) and the combined flow path 13 passing through the upper region of the cylinder head Ea. However, by providing the heat exchanger 2 in the joint passage 13, it is possible to suppress the increase in the cooling water temperature. As a result, when the fluid control valve FSV of the second flow path 12 is opened, local boiling of the communication path 15 can be effectively prevented.

[Other embodiments]
(a) As shown in FIG. 10, the pump P is a mechanical pump whose discharge rate changes according to the fluid pressure of the cooling water. may be changed by duty control. As shown in the figure, it is preferable to set the opening time of the solenoid valve V to be shorter as the number of revolutions of the engine E is higher. As a result, the higher the rotation speed of the engine E, the larger the discharge amount of the pump P. However, by shortening the valve opening time of the solenoid valve V, it becomes possible to keep the amount of cooling water flowing through the cylinder head Ea constant. . In this way, when the pump P is a mechanical pump, if the valve opening time of the solenoid valve V is changed according to the rotation speed of the engine E, an appropriate amount of cooling water can be circulated according to the driving force of the pump P. can be made

(b) As shown in FIG. 11, the pump P is an electric pump, and the controller 5 controls the discharge amount of the pump P to be smaller when the solenoid valve V is open than when the solenoid valve V is closed. duty control may be performed. As shown in the figure, it is preferable to set the voltage applied to the pump P to be lower when the solenoid valve V is open than when the solenoid valve V is closed. . As a result, when the solenoid valve V is open, the amount of cooling water circulating in the cooling system X increases. It becomes possible to In this way, if the pump P is an electric pump and duty control is performed so that the discharge amount of the pump P is reduced when the solenoid valve V is opened, local boiling of the cooling water is prevented while accelerating the warm-up operation. be able to.

(c) The controller 5 changes the fluid control valve FSV and the solenoid valve V from closed to open when the temperature of the cooling water flowing through the communication passage 15 reaches or exceeds a predetermined temperature (for example, 150° C.). can be In other words, instead of opening the fluid control valve FSV and the solenoid valve V in order as in the above-described embodiment, by opening both valves simultaneously, the temperature of the cooling water in the communication passage 15 reaches the limit of local boiling. Local boiling of the cooling water can be prevented by promoting warm-up until the time and changing the fluid control valve FSV and the solenoid valve V from closed to open.

(d) After the warm-up operation of the engine E is completed, the solenoid valve V is closed after the engine E stops, the solenoid valve V is opened for a short time before restarting, and the electric pump P is operated. The temperature of the cooling water inside the engine E may be made uniform as a whole. As a result, the accuracy of estimating the temperature of the cooling water in the communication passage 15 can be improved.

(e) The heat exchanger 2 provided on the path of the second flow path 12 may be omitted.

INDUSTRIAL APPLICABILITY The present invention can be used for a cooling system that cools an internal combustion engine with cooling water.

5: Control unit 11: First flow path 12: Second flow path 14: Third flow path 15: Communication path E: Engine (internal combustion engine)
Ea: Cylinder head Eb: Cylinder block FSV: Fluid control valve (first valve)
P: Pump T2: Second temperature (first threshold)
T3: third temperature (second threshold)
V: Solenoid valve (second valve)
X: Cooling system

Claims (9)

a pump for circulating cooling water to the internal combustion engine;
a first flow path through which the cooling water flows to the upper region of the cylinder head by the driving force of the pump;
a second flow path through which the cooling water flows to the lower region of the cylinder head by the driving force of the pump;
a third flow path through which the cooling water circulates inside the cylinder block by the driving force of the pump;
a first valve arranged on the path of the second flow path;
a second valve arranged on the path of the third flow path;
a communicating passage for circulating the cooling water between the inside of the cylinder head and the inside of the cylinder block;
and a control unit that controls opening and closing of the first valve and the second valve. The cooling system according to claim 1, wherein the control unit changes the first valve from closed to open when the temperature of the cooling water flowing through the communication passage becomes equal to or higher than a first threshold value. 3. The control unit changes the second valve from closed to open when the temperature of the cooling water flowing through the communication path becomes equal to or higher than a second threshold larger than the first threshold. Cooling system as described. 2. The cooling according to claim 1, wherein the control unit changes the first valve and the second valve from closed to open when the temperature of the cooling water flowing through the communication passage reaches or exceeds a predetermined temperature. system. The cooling system according to any one of claims 1 to 4, wherein the control section duty-controls the opening/closing time of the second valve. 6. The cooling system according to any one of claims 1 to 5, further comprising a third valve arranged on the path of said first flow path. The pump is a mechanical pump,
The cooling system according to any one of claims 1 to 6, wherein the control section changes the valve opening time of the second valve according to the rotational speed of the internal combustion engine. The pump is an electric pump,
7. The control unit according to any one of claims 1 to 6, wherein the control unit performs duty control so that the discharge amount of the pump is smaller when the second valve is opened than when the second valve is closed. cooling system. After the internal combustion engine has finished warming up, the control unit closes the first valve and the second valve after the internal combustion engine stops, and opens the first valve when restarting. A cooling system according to any one of claims 1 to 8, comprising a valve.

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