Cooling systems for internal combustion engines

Abstract

To provide an internal combustion engine cooling system capable of executing optimal pressure relief control when controlling a flow control valve in accordance with a difference between a target opening degree and an actual opening degree.SOLUTION: An internal combustion engine cooling system includes: multiple channels for allowing a coolant to flow; a flow control valve for controlling a flow rate of the coolant; and a control device for determining a target opening degree while obtaining a temperature of the coolant, determining a speed of moving the flow control valve so as to increase the speed proportionately as a difference between the target opening degree and an actual opening degree increases, and controlling the flow control valve by the speed. The control device performs: controlling the flow control valve by a first target opening degree determined on the basis of a temperature in the case of pressure of the coolant being less than a given value; determining, in the case of pressure of the coolant being equal to or higher than a given value, a second target opening degree with which the opening degree of multiple channels becoming a maximum and a third target opening degree being larger than the second target opening degree, and executing pressure relief control for controlling the flow control valve by using the third target opening degree; and controlling the flow control valve by using a fourth target opening degree being a difference from the actual opening degree smaller than from the first target opening degree, in the case of ending the pressure relief control.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to cooling systems for internal combustion engines. [Background technology]

[0002] Conventionally, cooling systems for internal combustion engines that have passages for supplying cooling water to parts that require cooling, such as the cylinder head and exhaust gas recirculation system of the internal combustion engine, have been known (see, for example, Patent Document 1). Such cooling systems for internal combustion engines have passages for supplying cooling water to a radiator, and the cooling water is cooled by the radiator. Patent Document 1 discloses a cooling system for an internal combustion engine that has flow control valves that control the flow rate of each passage, and controls the flow control valves so that an optimal flow rate of cooling water flows through each passage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-67014 A Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses a cooling system for an internal combustion engine that releases pressure by increasing the opening of a flow control valve when there is a possibility that the pressure in a cooling water circuit will increase. Patent Document 1 also discloses a cooling system for an internal combustion engine that slows down the rate of change in the opening of the flow control valve at the end of depressurization compared to the rate of change in the opening of the flow control valve at the start of depressurization. However, Patent Document 1 does not disclose pressure release control in a cooling system for an internal combustion engine that controls the flow control valve according to the difference between a target opening and an actual opening, which is the actual opening of the flow control valve.

[0005] An object of the present disclosure is to provide a cooling system for an internal combustion engine that can perform optimal depressurization control when controlling a flow control valve in accordance with the difference between a target opening and an actual opening, which is the actual opening of the flow control valve. [Means for solving the problem]

[0006] A cooling system for an internal combustion engine according to the present disclosure includes a plurality of passages through which a coolant flows, a flow control valve that controls the flow rate of the coolant flowing through each of the plurality of passages, and a control device that acquires a temperature of the coolant and determines a target opening, determines the speed at which the flow control valve is moved faster as the difference between the target opening and an actual opening that is an actual opening of the flow control valve increases, and controls the flow control valve based on the speed. When a pressure of the coolant flowing through each of the plurality of passages is less than a predetermined value, the control device controls the flow control valve using a first target opening determined based on the temperature, and when the pressure of the coolant is equal to or greater than a predetermined value, determines the second target opening at which the openings of the plurality of passages are maximized, and determines a third target opening that is greater than the second target opening, performs a pressure release control that controls the flow control valve using the third target opening, and when the pressure release control is terminated, controls the flow control valve using a fourth target opening that is smaller than the first target opening and an actual opening.

[0007] According to this cooling system for an internal combustion engine, the flow control valve is moved by the third target opening degree, which is larger than the second target opening degree, so that the passage through which the cooling water flows can be opened to the maximum angle more quickly. In addition, after the depressurization is completed, the flow control valve is slowly closed by the fourth target opening degree, thereby preventing water hammer. Thus, according to this cooling system for an internal combustion engine, when the flow control valve is controlled according to the difference between the target opening degree and the actual opening degree, which is the actual opening degree of the flow control valve, optimal depressurization control can be performed by simple control. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a cooling system for an internal combustion engine that can perform optimal pressure relief control when controlling a flow control valve in accordance with the difference between a target opening and an actual opening, which is the actual opening of the flow control valve. [Brief description of the drawings]

[0009] [Figure 1] 1 is a system diagram of an internal combustion engine control system according to an embodiment of the present disclosure. [Diagram 2] 5 is a graph showing an example of a relationship between the opening area (opening degree) of a corner passage and the rotation angle of a rotary valve according to an embodiment of the present disclosure. [Diagram 3] 4 is a flowchart showing a control procedure executed by a control device according to an embodiment of the present disclosure. [Figure 4] 5 is a timing chart showing a relationship between an actual rotation angle and a target rotation angle during pressure release control according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the following description, the upstream side and the downstream side will be referred to as "upstream" and "downstream" based on the direction in which the cooling water flows.

[0011] 1, the cooling system 1 of the internal combustion engine 2 is a device that cools various devices of the internal combustion engine 2. The cooling system 1 of the internal combustion engine 2 includes a flow control valve (V) 4, a valve fitting (V / F) 6, a water pump (W / P) 8, a cylinder block (C / B) 10, a cylinder head (C / H) 12, an outlet fitting (O / F) 14, an exhaust gas recirculation gas cooler (EGR / C) 16, a heater core (H / C) 18, a turbocharger (T / C) 20, a throttle (Th / B) 22, a motor generator (M / G) 24, a transmission cooler (TM / C) 26, an engine oil cooler (ENG / C) 28, a radiator (RA) 30, a hot bottle (HB) 32, and a control device 40. In this embodiment, the internal combustion engine 2 is a reciprocating type internal combustion engine that is mounted on a vehicle and has pistons (not shown) that rotate a crankshaft.

[0012] The cooling system 1 for the internal combustion engine 2 also includes a plurality of passages for supplying cooling water to various devices. In this embodiment, the cooling system 1 includes a main engine cooling passage 50, a radiator passage 52, an exhaust gas recirculation gas cooler passage 54, a throttle hot water passage 56, an engine oil cooler passage 58, and a turbocharger cooling passage 60.

[0013] The flow control valve 4 is a device that adjusts the amount of cooling water flowing through the passages. In this embodiment, it is a device that adjusts the amount of cooling water flowing through the radiator passage 52, the exhaust gas recirculation cooler passage 54, and the engine oil cooler passage 58 (hereinafter, sometimes referred to as each passage in the specification). In this embodiment, the flow control valve 4 controls the flow rate of cooling water flowing through each passage by varying the opening degree of the inlet through which the cooling water enters the flow control valve 4 from each passage. In this embodiment, the flow control valve 4 is a rotary valve having a rotary valve 4a. The flow control valve 4 changes the size of the opening area of ​​the inlet of each passage by rotating the rotary valve 4a. In this way, the flow control valve 4 can control the flow rate of cooling water flowing through each passage. The flow control valve 4 is electrically connected to the control device 40, and the rotation angle of the valve is controlled by the control device 40. In addition, the flow control valve 4 has a rotation angle sensor (not shown) that detects the rotation angle ω of the rotary valve 4a, and transmits the rotation angle ω of the rotary valve 4a to the control device 40.

[0014] The flow control valve 4 has a first inlet 4b directly connected to the rotary valve 4a as an inlet through which the cooling water enters, a second inlet 4c bypassing the rotary valve 4a via a thermostat (T) 5 and connected to a valve fitting 6, and a third inlet 4d bypassing the rotary valve 4a and a thermo valve (not shown) for opening and closing the second inlet 4c of the thermostat 5 and connected to the valve fitting 6. When the cooling water reaches a predetermined temperature, the paraffin wax melts and opens the second inlet 4c. The predetermined temperature is a temperature at which the cooling water may boil and the internal combustion engine 2 may overheat. The cooling water supplied to the third inlet 4d passes through this paraffin wax and melts the paraffin wax. The thermostat 5 has a spring that biases the thermo valve in a direction to close the second inlet 4c. The thermostat 5 may be an existing thermostat 5, and a more detailed description will be omitted.

[0015] The valve fitting 6 is a cylindrical member attached to the cooling water outlet of the flow control valve 4. A water pump 8 that supplies cooling water to each passage is connected downstream of the valve fitting 6. In this embodiment, the water pump 8 is a mechanical pump in which an impeller is rotated by receiving driving force from the crankshaft of the internal combustion engine 2.

[0016] A main engine cooling passage 50 is connected downstream of the water pump 8. The main engine cooling passage 50 includes a first water jacket (not shown) formed around a cylinder (not shown) of the cylinder block 10, and a second water jacket (not shown) formed in the vicinity of an exhaust port of the cylinder head. The main engine cooling passage 50 cools the cylinder block 10 and the cylinder head 12 by passing cooling water through the first water jacket and the second water jacket.

[0017] The outlet fitting 14 is a cylindrical member that distributes the cooling water that has passed through the cylinder block 10 and the cylinder head 12 to each passage. In this embodiment, the outlet fitting 14 is attached downstream of the second water jacket of the cylinder head 12. In this embodiment, the outlet fitting 14 is provided with a water temperature sensor 15. The water temperature sensor 15 detects the temperature (water temperature WT) of the cooling water passing through the outlet fitting 14. In other words, the water temperature sensor 15 detects the temperature of the cooling water before the cooling water is supplied to each passage. The water temperature sensor 15 is electrically connected to the control device 40 and transmits the detected water temperature WT to the control device 40.

[0018] The internal combustion engine 2 of this embodiment is provided with an exhaust gas recirculation device 17 including an exhaust gas recirculation valve (not shown), which introduces the exhaust gas of the internal combustion engine 2 into the intake air. The exhaust gas recirculation valve is electrically connected by a control device 40, and the amount of exhaust gas flowing into the intake air is adjusted by the exhaust gas recirculation valve. The exhaust gas recirculation gas cooler (one example of an exhaust gas recirculation gas cooling device) 16 is a heat exchanger that cools the exhaust gas recirculation gas (see the broken line in FIG. 1) introduced into the intake air from the exhaust gas of the internal combustion engine 2 by the exhaust gas recirculation device 17, using coolant. The heater core 18 is a heat exchanger of an air conditioning device (HVAC) 19 that supplies conditioned air to the interior of the vehicle. The heater core 18 absorbs heat from the coolant and heats the conditioned air. The air conditioning device 19 includes a blower fan 19a, and supplies the conditioned air heated by the heater core 18 into the interior by rotating the blower fan 19a. The air conditioning device 19 includes an air conditioning control device 19b. The air conditioning control device 19b is electrically connected to the control device 40 via a communication line (not shown) and can acquire information transmitted from the control device 40. Similarly, the control device 40 can acquire information transmitted from the air conditioning control device 19b.

[0019] The exhaust recirculation gas cooler 16 and the heater core 18 are connected to an exhaust recirculation gas cooler passage 54, which is connected to the outlet fitting 14, and the cooling water is supplied to the exhaust recirculation gas cooler passage 54. The exhaust recirculation gas cooler passage 54 is a passage formed by a rubber hose, a metal pipe, or the like. The exhaust recirculation gas cooler passage 54 branches into a first exhaust recirculation gas cooler passage 54a connected to the first inlet 4b of the flow control valve 4 downstream of the heater core 18, and a second exhaust recirculation gas cooler passage 54b connected to the third inlet 4d. The second exhaust recirculation gas cooler passage 54b is a passage for sensing the temperature of the thermostat 5. Specifically, when the cooling water becomes hot, the cooling water flowing through the second exhaust recirculation gas cooler passage 54b melts the paraffin wax, and when the paraffin wax melts and the second inlet 4c opens, the cooling water is supplied to the radiator passage 52 regardless of the rotation angle ω of the rotary valve 4a.

[0020] The turbocharger 20 is a device that supercharges the intake air of the internal combustion engine 2. A turbocharger cooling passage 60 that branches off from the exhaust gas recirculation gas cooler passage 54 at a position upstream of the exhaust gas recirculation gas cooler 16 is connected to the turbocharger 20, and cools the turbine shaft of the turbocharger 20. The turbocharger cooling passage 60 is connected to a hot bottle 32.

[0021] The throttle 22 is a device that controls the amount of intake air of the internal combustion engine 2. The motor generator 24 is a rotating electric machine that is driven by the internal combustion engine 2 and generates electricity and starts the internal combustion engine 2. The throttle 22 and the motor generator 24 are connected to a throttle hot water passage 56 that is connected to the outlet fitting 14. The throttle hot water passage 56 is connected to the valve fitting 6 without passing through the radiator 30. The throttle hot water passage 56 prevents the throttle 22 and the motor generator 24 from freezing by constantly flowing heated cooling water.

[0022] The transmission cooler 26 is a heat exchanger that exchanges heat between the transmission oil filled in the transmission and the cooling water, thereby raising or cooling the temperature of the transmission oil. The engine oil cooler 28 is a heat exchanger that exchanges heat between the engine oil filled in the internal combustion engine 2 and the cooling water, thereby raising or cooling the temperature of the engine oil.

[0023] The transmission cooler 26 and the engine oil cooler 28 are connected to an engine oil cooler passage 58 that branches off from the throttle hot water passage 56 upstream of the throttle 22, and are supplied with cooling water. The engine oil cooler passage 58 is connected to the first inlet 4b of the flow control valve 4.

[0024] The radiator 30 has an upper passage 30a (not shown), a radiator core 30b arranged downstream of the upper passage 30a, and a lower passage 30c arranged downstream of the radiator core 30b. The radiator core 30b has a plurality of fins and is a heat exchanger for exchanging heat between the coolant and the outside air of the vehicle to cool the coolant. The upper passage 30a of the radiator 30 is connected to a radiator passage 52 connected to the outlet fitting 14. The lower passage 30c of the radiator 30 is connected to a first radiator passage 52a connected to the first inlet 4b of the flow control valve 4 and a second radiator passage 52b connected to the second inlet 4c. The radiator passage 52 branches into the first radiator passage 52a and the second radiator passage 52b. Furthermore, the radiator passage 52 branches off into a third radiator passage 52 c that is connected to the supercharger cooling passage 60 upstream of the radiator 30 .

[0025] The hot bottle 32 functions as a reservoir tank for temporarily storing the cooling water, and is also a tank for bleeding air from the cooling water. The upstream of the hot bottle 32 is connected to the turbocharger cooling passage 60 downstream of the joint between the third radiator passage 52c and the turbocharger cooling passage 60. The downstream of the hot bottle 32 is connected to the throttle hot water passage 56 downstream of the motor generator 24. The hot bottle 32 is supplied with the cooling water that has passed through the turbocharger 20.

[0026] The control device 40 is a device that controls the flow control valve 4 in accordance with the water temperature WT acquired by the water temperature sensor 15, the running state of the vehicle, the operating state of the internal combustion engine 2, and the like, to control the flow rate of the cooling water. More specifically, the control device 40 determines the opening degree O of each passage, i.e., the target rotation angle ωt of the rotary valve 4a, in accordance with the water temperature WT, the running state of the vehicle, and the operating state of the internal combustion engine 2, and controls the flow rate of the cooling water flowing through each passage.

[0027] In the graph of FIG. 2, the horizontal axis indicates the rotation angle ω of the rotary valve 4a, and the vertical axis indicates the opening area (opening degree O). The control device 40 determines the target rotation angle ωt according to the water temperature WT, the running state of the vehicle, and the operating state of the internal combustion engine 2. The control device 40 rotates the rotary valve 4a toward the target rotation angle ωt. When the rotary valve 4a reaches the target rotation angle ωt, the opening degree O of each passage becomes a value corresponding to the target rotation angle ωt, and the flow rate of the cooling water flowing through each passage is controlled. In other words, determining the target rotation angle ωt is synonymous with determining the target opening degree Ot. During this time, the control device 40 obtains the actual rotation angle ωr of the rotary valve 4a from a rotation angle sensor provided in the flow control valve 4, and monitors whether the actual rotation angle is following the target rotation angle ωr.

[0028] Moreover, the flow control valve 4 of this embodiment has a first stopper (an example of a restricting portion) that restricts the rotation of the rotary valve 4a at the position of the minimum rotation angle ωmin of the rotary valve 4a (for example, at the position of -40 degrees in FIG. 2 in this embodiment). Moreover, the flow control valve 4 has a second stopper (an example of a restricting portion) that restricts the rotation of the rotary valve 4a at the position of the maximum rotation angle ωmax (for example, at the position of 210 degrees in FIG. 2 in this embodiment). The control device 40 controls the rotary valve 4a in the section from the first stopper to the second stopper.

[0029] The control device 40 also determines the introduction rate of the exhaust recirculation gas, and controls the opening of the exhaust recirculation valve so that the introduction amount of the exhaust recirculation gas becomes the introduction rate determined relative to the intake air amount. The control device 40 may determine the introduction rate of the exhaust recirculation gas based on a map that defines the introduction rate of the exhaust recirculation gas for each operating range of the internal combustion engine 2.

[0030] In addition, the control device 40 may control each device, such as a fuel injection valve (not shown), an exhaust gas recirculation valve (not shown), and the boost pressure of the turbocharger 20, so that the internal combustion engine 2 is in a desired operating state, based on values ​​obtained from sensors such as an air flow sensor (not shown) and an accelerator position sensor (not shown).

[0031] The control device 40 is actually an ECU (Electronic Control Unit) configured by a microcomputer including an arithmetic unit, a memory, an input / output buffer, etc. The control device 40 controls each device based on a map and a program stored in the memory so that the internal combustion engine 2 is in a desired operating state. Note that the various controls are not limited to being processed by software, and can also be processed by dedicated hardware (electronic circuits).

[0032] Next, a control procedure executed by the control device 40 will be described with reference to the flowchart of Fig. 3. The control device 40 starts a control operation when an ignition switch (not shown) is turned on.

[0033] In step S1, the control device 40 acquires the water temperature WT. After acquiring the water temperature WT, the control device 40 proceeds to step S2, where it determines a first target rotation angle (one example of a first target opening) ωt1 of the valve according to the traveling state of the vehicle and the operating state of the internal combustion engine 2. The control device 40 acquires the difference between the first target rotation angle ωt1 and an actual rotation angle (one example of an actual opening) ωr, which is the current angle of the rotary valve 4a, and determines a first rotation speed ωv1 at which the rotary valve 4a is moved based on the difference between the target rotation angle ωt and the actual rotation angle ωr. The control device 40 determines the rotation speed ωv such that the rotation speed ωv increases as the difference between the target rotation angle ωt and the actual rotation angle ωr increases. After determining the rotation speed ωv, the control device 40 proceeds to step S3.

[0034] In step S3, the control device 40 judges whether the pressure of the cooling water flowing through each passage is equal to or higher than a predetermined value, and in this embodiment, whether the rotation speed Er of the internal combustion engine 2 is equal to or higher than a predetermined rotation speed Et. In this embodiment, when the rotation speed Er of the internal combustion engine 2 increases, the rotation speed of the water pump 8 driven by the crankshaft also increases. For this reason, the predetermined rotation speed Et is determined based on the rotation speed Er of the internal combustion engine 2 at which the pressure of each passage increases to a pressure at which there is a concern of hose slippage, etc., as the rotation speed of the water pump 8 increases. The predetermined rotation speed Et may be, for example, a rotation speed near a red zone set in a region from a rotation speed 1000 rpm lower than the allowable rotation speed of the internal combustion engine 2 to the allowable rotation speed. The predetermined rotation speed Et may also be a rotation speed slightly lower than the red zone. When the control device 40 judges that the rotation speed Er of the internal combustion engine 2 is equal to or higher than the predetermined rotation speed Et (YES in step S3), the process proceeds to step S4.

[0035] In step S4, the control device 40 establishes the depressurization control. As shown in FIG. 4, in this embodiment, when the rotation speed Er of the internal combustion engine 2 is equal to or higher than a predetermined rotation speed Et, the control device 40 determines that the depressurization control is necessary and records a flag for the depressurization control. However, for example, when the water pump 8 is an electric water pump, the control device 40 may obtain the rotation speed of the water pump 8 and determine whether or not the depressurization control is necessary. The control device 40 may also measure the pressure of the cooling water flowing through each passage with a sensor or the like. Furthermore, the control device 40 may determine whether or not the depressurization control is necessary by taking into account the water temperature WT in addition to the rotation speed Er of the internal combustion engine 2 or the rotation speed of the water pump 8. As shown in FIG. 3, when the control device 40 establishes the depressurization control, the control device 40 proceeds to step S5 and starts the depressurization control.

[0036] In step S5, the control device 40 determines a second target rotation angle (an example of a second target opening) ωt2 at which the opening of each passage is maximized, and determines a third target rotation angle (an example of a third target opening) ωt3 at an opening greater than the second target rotation angle ωt2. As shown in FIG. 2, in this embodiment, when the rotation angle ω is between 150 degrees and 160 degrees (see section A in FIG. 2), the opening areas of the radiator passage 52, the exhaust gas recirculation cooler passage 54, and the engine oil cooler passage 58 (each passage) are maximized. For this reason, the control device 40 determines the second target rotation angle ωt2 when the rotation angle ω is between 150 degrees and 160 degrees. In addition, in this embodiment, the control device 40 determines the third target rotation angle ωt3 to be a maximum rotation angle ωmax greater than the second target rotation angle ωt2. However, the third target rotation angle ωt3 may be any rotation angle ω greater than the determined second target rotation angle ωt2. In other words, the third target rotation angle ωt3 may be any target rotation angle ωt that is greater than the difference between the actual rotation angle ωr and the second target rotation angle ωt2. After determining the second target rotation angle ωt2 and the third target rotation angle ωt3, the control device 40 proceeds to step S6.

[0037] In step S6, the control device 40 determines a second rotational speed ωv2 based on the difference between the actual rotational angle ωr and the third target rotational angle ωt3. After determining the second rotational speed ωv2, the control device 40 moves the rotary valve 4a toward the third target rotational angle ωt3 at the second rotational speed ωv2. After rotating the rotary valve 4a at the second rotational speed ωv2, the control device 40 advances the process to step S7.

[0038] In step S7, the control device 40 determines whether the actual rotation angle ωr has reached the second target rotation angle ωt2. If the control device 40 determines that the actual rotation angle ωr has reached the second target rotation angle ωt2 (YES in step S7), the process proceeds to step S8. If the control device 40 determines that the actual rotation angle ωr is less than the second target rotation angle ωt2 (NO in step S7), the process returns to step S6, and the rotary valve 4a continues to rotate toward the third target rotation angle ωt3 at the second rotational speed ωv2.

[0039] In step S8, the control device 40 switches the target rotation angle ωt from the third target rotation angle ωt3 to the second target rotation angle ωt2. As a result, the control device 40 causes the rotary valve 4a to rotate toward the second target rotation angle ωt2 at a third rotational speed ωv3 based on the difference between the actual rotation angle ωr and the second target rotation angle ωt2. After causing the control device 40 to rotate the rotary valve 4a toward the second target rotation angle ωt2, the control device 40 advances the process to step S9.

[0040] In step S9, the control device 40 judges whether the actual rotation angle ωr coincides with the second target rotation angle ωt2. If the control device 40 judges that the actual rotation angle ωr does not coincide with the second target rotation angle ωt2 (step S9: NO), the control device 40 returns the process to step S8 and continues to rotate the rotary valve 4a toward the second target rotation angle ωt2. If the control device 40 judges that the actual rotation angle ωr coincides with the second target rotation angle ωt2 (step S9: YES), the control device 40 proceeds to step S10.

[0041] As shown in the graph of the rotation angle ω in FIG. 4, by controlling the rotary valve 4a using the third target rotation angle ωt3 in this way (see the dashed line from time t1 to time t2 in FIG. 4), the control device 40 can rotate the rotary valve 4a faster than when determining the rotation speed ωv based on the difference between the actual rotation angle ωr and the second target rotation angle ωt2 (see the solid line from time t1 to time t2 in FIG. 4). The rotary valve 4a once exceeds the second target rotation angle ωt2 due to inertia, and then slowly returns to the second target rotation angle ωt2 (see the solid line from time t2 to time t3 in FIG. 4). By controlling the rotary valve 4a in this way, the control device 40 quickly moves the rotary valve 4a to a position where the opening degree of each passage is maximized, and prevents the rotary valve 4a from being stopped due to deviation from the second target rotation angle ωt2 due to the inertial force of the rotary valve 4a. As a result, the control device 40 can quickly execute the depressurization control. At this time, it is advisable to set the second target rotation angle ωt2 to a rotation angle ωt (150 degrees to 155 degrees) that is equal to or lower than the middle part of section A. This makes it easier to maintain the opening area of ​​each passage at a maximum even if the rotation angle ωt exceeds the second target rotation angle ωt2 due to the inertial force of the rotary valve 4a, such as from time t2 to time t3 in FIG.

[0042] In this embodiment, the cooling system 1 has a second inlet 4c that bypasses the rotary valve 4a via the thermostat 5 and is connected to the valve fitting 6. The thermostat 5 is biased by a coil spring so as to block the second inlet 4c. In other words, the cooling system 1 of the internal combustion engine 2 has a bypass passage that bypasses the rotary valve 4a, which is an example of the flow control valve 4, from the second inlet 4c and is connected to the valve fitting 6. The thermostat 5 that functions as a vent valve that releases pressure from each passage is disposed on the bypass passage. As a result, when the pressure in each passage rises beyond a predetermined pressure that balances with the biasing force of the coil spring, the thermostat 5 opens and the pressure in each passage can be released. In this way, by disposing the existing thermostat 5, not only pressure control but also the pressure in each passage can be released using the thermostat 5.

[0043] In step S10, the control device 40 ends the depressurization control. The control device 40 ends the depressurization control when the state in which the pressure of the cooling water flowing through each passage is less than a predetermined value, in this embodiment, the state in which the rotation speed of the internal combustion engine 2 is less than a predetermined rotation speed, continues for a second predetermined time. The second predetermined time may be a time that can determine that the rotation speed of the internal combustion engine 2 is stable at less than the predetermined rotation speed. Note that, if the pressure of the cooling water flowing through each passage becomes less than a predetermined value while the rotary valve 4a is being moved toward the third target rotation angle ωt3 in step S6, the depressurization control may be ended at that time. When the control device 40 ends the depressurization control, it records the flag of the depressurization control to the non-established side as shown in FIG. 4 (see time t4 in FIG. 4). When the control device 40 records the flag to the non-established side, the process proceeds to step S11.

[0044] In step S11, the control device 40 determines a fourth target rotation angle (an example of a fourth target opening) ωt4. As shown from time t4 to time t5 in FIG. 4, the fourth target rotation angle ωt4 is a target rotation angle ωt set to gradually decrease the actual rotation angle ωr toward the first target rotation angle ωt1. In this embodiment, the fourth target rotation angle ωt4 is a value obtained by subtracting a predetermined rotation angle from the actual rotation angle ωr. Therefore, the control device 40 rotates the rotary valve 4a by the fourth target rotation angle ωt4 at every predetermined time. As a result, the rotary valve 4a rotates and moves gradually toward the first target rotation angle ωt1 at a constant third rotation speed ωv3. As a result, the occurrence of a water hammer due to a sudden pressure increase in each passage is suppressed. The fourth target rotation angle ωt4 may be a value obtained by dividing the rotation angle ω from the second target rotation angle ωt2 to the first target rotation angle ωt1 into a plurality of angles. In any case, the fourth target rotation angle ωt4 may be a value that causes the rotary valve 4a to rotate gently toward the first target rotation angle ωt1. As shown in Fig. 3, after determining the fourth target rotation angle ωt4, the control device 40 advances the process to step S12. Note that the first target rotation angle ωt1 here does not need to be the same value as in step S2, and may be set based on the water temperature WT, the running state of the vehicle, and the operating state of the internal combustion engine 2 at that time.

[0045] In step S12, the control device 40 moves the rotary valve 4a at the third rotational speed ωv3, and proceeds to step S13. In step S13, the control device 40 judges whether a first predetermined time has elapsed since the rotary valve 4a was moved at the third rotational speed ωv3. The first predetermined time may be a time sufficient to prevent a sudden increase in pressure in each passage. If the control device 40 judges that the predetermined time has not elapsed (step S13 NO), the control device 40 returns the process to step S12 and continues to rotate the rotary valve 4a at the third rotational speed ωv3 toward the first target rotational angle ωt1. If the control device 40 judges that the first predetermined time has elapsed (step S13 YES), the control device 40 proceeds to step S14. In step S14, the control device 40 rotates the rotary valve 4a at the first rotational speed ωv1.

[0046] In step S3, when the control device 40 determines that the rotation speed Er of the internal combustion engine 2 is less than the predetermined rotation speed Et, the control device 40 advances the process to step S14. In step S14, when the rotary valve 4a is rotated at the first rotation speed ωv1, the control device 40 advances the process to step S15. In step S15, the control device 40 determines whether the actual rotation angle ωr matches the first target rotation angle ωt1. When the control device 40 determines that the actual rotation angle ωr does not match the first target rotation angle ωt1 (step S15 NO), the control device 40 returns the process to step S14 and continues to rotate the rotary valve 4a toward the first target rotation angle ωt1 at the first rotation speed ωv1. When the control device 40 determines that the actual rotation angle ωr matches the first target rotation angle ωt1 (step S15 YES), the control device 40 returns the process to step S1.

[0047] Note that even if the control device 40 determines in step S13 that the predetermined time has not elapsed (NO in step S13), if the first target rotation angle ωt1 changes to a rotation angle ω larger than the actual rotation angle ωr, that is, if the opening of each passage changes to be larger, the control device 40 may proceed to the process in step S14. In such a case, the rotary valve 4a rotates in a direction to increase the opening of each passage, so that the pressure in each passage decreases.

[0048] As described above, according to the cooling system 1 for the internal combustion engine 2 of the present disclosure, optimal depressurization control can be performed by controlling the rotary valve 4a in accordance with the difference between the first target rotation angle ωt1 to the fourth target rotation angle ωt4 and the actual rotation angle ωr.

[0049] Furthermore, according to the cooling system 1 for the internal combustion engine 2, the rotary valve 4a is moved by the third target rotation angle ωt3, which is larger than the second target rotation angle ωt2, so that the passage for the cooling water to open to the maximum angle can be reached more quickly. After the depressurization is completed, the rotary valve 4a is slowly closed by the fourth target rotation angle ωt4, thereby preventing water hammer. Thus, according to the cooling system 1 for the internal combustion engine 2, in a system in which the rotation speed of the rotary valve 4a is determined according to the difference between the target rotation angle ωt and the actual rotation angle ωr, optimal depressurization control can be performed by simple control.

[0050] <Other embodiments> Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention. In particular, the multiple modifications described in this specification can be arbitrarily combined as necessary.

[0051] (a) In the above embodiment, the flow control valve 4 is described using a rotary valve 4a as an example, but the present disclosure is not limited to this. The flow control valve 4 may be, for example, a flow control valve 4 that controls the flow rate of each passage by a slide-type valve. In this case, the restricting portion may be a stopper that restricts the movement of the slide-type valve.

[0052] (b) In the above embodiment, an example has been described in which the control device 40 controls the flow rate of the cooling water flowing through each passage using the relationship between the opening area of ​​each passage in Fig. 2 and the rotation angle ω of the rotary valve 4a, but the present disclosure is not limited to this. The control device 40 may control the flow control valve 4 using, for example, a sensor that detects the flow rate. In addition, the opening area of ​​each passage in Fig. 2 and the rotation angle ω of the rotary valve 4a may be changed as appropriate. [Explanation of symbols]

[0053] 1: Cooling system 2: Internal combustion engine 4: Flow control valve 5: Thermostat 40: Control device 52: Radiator passage 54: Exhaust gas cooler passage O: Opening degree Ot:Target opening ωr: Actual rotation angle ωt: target rotation angle ωv: Rotation speed

Claims

1. A cooling system for an internal combustion engine, comprising: A plurality of passages through which cooling water flows; a flow control valve for controlling a flow rate of the cooling water flowing through each of the plurality of passages; a control device that acquires a temperature of the cooling water and determines a target opening, determines a speed such that the speed at which the flow control valve is moved increases as a difference between the target opening and an actual opening that is an actual opening of the flow control valve increases, and controls the flow control valve based on the speed; Equipped with the control device controls the flow control valve with a first target opening determined based on the temperature when a pressure of the cooling water flowing through each of the plurality of passages is less than a predetermined value; When the pressure of the cooling water is equal to or higher than a predetermined value, a second target opening degree at which the opening degrees of the plurality of passages are maximized is determined, and a third target opening degree that is greater than the second target opening degree is determined, and a pressure relief control is executed to control the flow control valve using the third target opening degree. When the depressurization control is terminated, the flow control valve is controlled using a fourth target opening degree, the fourth target opening degree being smaller in difference from an actual opening degree than the first target opening degree. Cooling system of an internal combustion engine.

2. the control device controls the flow control valve using the fourth target opening degree until a first predetermined time has elapsed after the depressurization control is completed, and controls the flow control valve using the first target opening degree after the first predetermined time has elapsed.

2. The cooling system for an internal combustion engine according to claim 1.

3. When the control device executes the depressurization control, if the actual opening degree reaches the second target opening degree, the control device switches from control using the third target opening degree to control using the second target opening degree.

3. A cooling system for an internal combustion engine according to claim 1 or 2.

4. a bypass passage that bypasses the flow control valve; a vent valve provided in the bypass passage and opening when the pressure in the bypass passage is equal to or higher than a predetermined pressure; Further comprising:

4. A cooling system for an internal combustion engine according to claim 1.

5. The vent valve is a thermostat.

5. The cooling system for an internal combustion engine according to claim 4.

6. The control device terminates the depressurization control when a state in which the pressure of the cooling water is lower than a predetermined pressure continues for a second predetermined time.

6. A cooling system for an internal combustion engine according to any one of claims 1 to 5.

Images