JP2023149294A - Internal combustion engine cooling system - Google Patents

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

The present disclosure relates to cooling systems for internal combustion engines.

BACKGROUND ART Cooling systems for internal combustion engines have been known that include passages that supply cooling water to parts that require cooling, such as cylinder heads and exhaust circulation devices of internal combustion engines (for example, see Patent Document 1). Such a cooling system for an internal combustion engine has a passage that supplies 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 includes a flow control valve that controls the flow rate of each passage, and controls the flow control valve so that an optimum flow rate of cooling water flows through each passage.

JP 2017-67014 Publication

Patent Document 1 discloses a cooling system for an internal combustion engine that relieves pressure by increasing the opening degree of a flow control valve when there is a possibility that the pressure in a cooling water circuit increases. Furthermore, Patent Document 1 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 pressure relief compared to the rate of change in the opening of the flow control valve at the start of pressure relief. However, Patent Document 1 discloses pressure relief control in a cooling system for an internal combustion engine that controls a 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. do not have.

The problem of the present disclosure is to cool an internal combustion engine that can perform optimal pressure relief control when controlling the flow control valve according to the difference between the target opening and the actual opening, which is the actual opening of the flow control valve. The goal is to provide a system.

A cooling system for an internal combustion engine according to the present disclosure includes a plurality of passages through which cooling water flows, a flow control valve that controls the flow rate of the cooling water flowing in each of the plurality of passages, and a temperature control valve that obtains the temperature of the cooling water and obtains a target temperature. determining the opening degree, and determining the speed such that the larger the difference between the target opening degree and the actual opening degree, which is the actual opening degree of the flow rate control valve, the faster the speed at which the flow rate control valve is moved; and a control device that controls the flow rate control valve based on the speed. When the pressure of the cooling water flowing through each of the plurality of passages is less than a predetermined value, the control device controls the flow rate control valve according to a first target opening determined based on the temperature, and When the pressure is above a predetermined value, determining the second target opening degree at which the opening degree of the plurality of passages is the maximum, and determining a third target opening degree that is larger than the second target opening degree; When performing pressure relief control to control the flow rate control valve using the third target opening degree and terminating the pressure relief control, an opening whose difference from the actual opening degree is smaller than the first target opening degree. The flow rate control valve is controlled using a fourth target opening degree.

According to this cooling system for an internal combustion engine, by moving the flow control valve at the third target opening degree that is larger than the second target opening degree, it is possible to more quickly reach the angle at which the cooling water flow passage opens to the maximum. can. Moreover, after the pressure release is completed, water hammer is prevented by slowly closing the flow rate control valve according to the fourth target opening degree. In this way, this cooling system for an internal combustion engine allows easy control to optimize the flow control valve according to the difference between the target opening and the actual opening, which is the actual opening of the flow control valve. It is possible to perform pressure relief control.

According to the present disclosure, cooling of an internal combustion engine allows optimal pressure relief control to be performed when controlling a 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. system can be provided.

FIG. 1 is a system diagram of a control system for an internal combustion engine according to an embodiment of the present disclosure. 6 is a graph showing an example of the relationship between the rotation angle of the rotary valve and the opening area (opening degree) of the square passage according to the embodiment of the present disclosure. 5 is a flowchart showing a control procedure executed by a control device according to an embodiment of the present disclosure. 5 is a timing chart showing a relationship between an actual rotation angle and a target rotation angle during pressure relief control according to an embodiment of the present disclosure.

Embodiments of the present disclosure will be described below with reference to the drawings. In the following specification, upstream will be referred to as upstream, and downstream will be referred to as downstream, based on the direction in which cooling water flows.

As shown in FIG. 1, a cooling system 1 for an internal combustion engine 2 is a device that cools various devices of the internal combustion engine 2. As shown in FIG. A cooling system 1 for an 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, and a cylinder. Head (C/H) 12, outlet fitting (O/F) 14, exhaust gas circulation gas cooler (EGR/C) 16, heater core (H/C) 18, and supercharger (T/C) 20. , throttle (Th/B) 22, motor generator (M/G) 24, transmission cooler (TM/C) 26, engine oil cooler (ENG/C) 28, radiator (RA) 30, and hot bottle. (HB) 32 and a control device 40. In this embodiment, the internal combustion engine 2 is a reciprocating internal combustion engine 2 that is mounted on a vehicle and has a piston (not shown) that rotates a crankshaft.

The cooling system 1 for the internal combustion engine 2 also includes a plurality of passages that supply cooling water to various devices. This embodiment includes a main engine cooling passage 50, a radiator passage 52, an exhaust circulation gas cooler passage 54, a throttle hot water passage 56, an engine oil cooler passage 58, and a supercharger cooling passage 60.

The flow control valve 4 is a device that adjusts the amount of cooling water flowing into the passage. This embodiment is a device that adjusts the amount of cooling water flowing into a radiator passage 52, an exhaust gas circulation gas cooler passage 54, and an engine oil cooler passage 58 (hereinafter sometimes referred to as each passage in the specification). In this embodiment, the flow rate control valve 4 controls the flow rate of the cooling water flowing into each passage by varying the degree of opening of the inlet into which the cooling water enters the flow rate 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. Thereby, the flow control valve 4 can control the flow rate of cooling water flowing into each passage. The flow rate control valve 4 is electrically connected to a control device 40, and the rotation angle of the valve is controlled by the control device 40. Further, 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.

The flow control valve 4 has a first inlet 4b that is directly connected to the rotary valve 4a as an inlet for cooling water, and a first inlet 4b that bypasses the rotary valve 4a via a thermostat (T) 5 and is connected to a valve fitting 6. It has a second inlet 4c, and a third inlet 4d that bypasses the thermovalve (not shown) that opens and closes the second inlet 4c of the thermostat 5 and the rotary valve 4a and is connected to the valve fitting 6. When the cooling water reaches a predetermined temperature, the paraffin wax melts and the thermostat 5 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 it. The thermostat 5 has a spring that biases the thermovalve in the direction of closing the second inlet 4c. Note that the thermostat 5 may be any existing thermostat 5, and a more detailed explanation will be omitted.

The valve fitting 6 is a cylindrical member attached to the cooling water outlet of the flow control valve 4. A water pump 8 is connected downstream of the valve fitting 6 to supply cooling water to each passage. In this embodiment, the water pump 8 is a mechanical pump whose impeller rotates by receiving driving force from the crankshaft of the internal combustion engine 2.

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 the cylinder (not shown) of the cylinder block 10, and a second water jacket (not shown) formed near the exhaust port of the cylinder head. including. The main engine cooling passage 50 cools the cylinder block 10 and the cylinder head 12 by allowing cooling water to pass through the first water jacket and the second water jacket.

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 installed 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 of the cooling water passing through the outlet fitting 14 (water temperature WT). 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.

The internal combustion engine 2 of this embodiment includes an exhaust circulation device 17 including an exhaust circulation valve (not shown), and introduces the exhaust gas of the internal combustion engine 2 into the intake air. The exhaust circulation valve is electrically connected by the control device 40, and the amount of exhaust gas flowing into the intake is adjusted by the exhaust circulation valve. The exhaust circulation gas cooler (an example of an exhaust circulation gas cooling device) 16 is a heat exchanger that uses cooling water to cool the exhaust circulation gas (see broken line in FIG. 1) introduced from the exhaust gas of the internal combustion engine 2 into the intake by the exhaust circulation device 17. It is a vessel. The heater core 18 is a heat exchanger of an air conditioner (HVAC) 19 that supplies conditioned air to the interior of the vehicle. The heater core 18 absorbs heat from the cooling water and warms the conditioned air. The air conditioner 19 includes a blower fan 19a, and supplies conditioned air heated by the heater core 18 indoors by rotating the blower fan 19a. The air conditioner 19 includes an air conditioning control device 19b. The air conditioning control device 19b is electrically connected to the control device 40 by 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.

The exhaust gas circulation gas cooler 16 and the heater core 18 are connected to an exhaust gas circulation gas cooler passage 54 that is connected to the outlet fitting 14, and are supplied with cooling water. The exhaust circulation gas cooler passage 54 is a passage formed by a rubber hose, a metal pipe, or the like. The exhaust circulation gas cooler passage 54 includes a first exhaust circulation 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 circulation gas cooler passage 54b connected to the third inlet 4d. , branches into. The second exhaust gas circulation gas cooler passage 54b is a temperature sensing passage for the thermostat 5. Specifically, when the cooling water reaches a high temperature, the cooling water flowing through the second exhaust circulation gas cooler passage 54b melts the paraffin wax, and when the paraffin wax melts and the second inlet 4c opens, the rotation angle ω of the rotary valve 4a changes. Cooling water is supplied to the radiator passage 52 regardless of the condition.

The supercharger 20 is a device that supercharges the intake air of the internal combustion engine 2. The supercharger 20 is connected to a supercharger cooling passage 60 branched from the exhaust circulation gas cooler passage 54 upstream of the exhaust circulation gas cooler 16, and cools the turbine shaft of the supercharger 20. The supercharger cooling passage 60 is connected to the hot bottle 32.

The throttle 22 is a device that controls the intake air amount 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. Throttle 22 and motor generator 24 are connected to a throttle hot water passage 56 that is connected to outlet fitting 14 . The throttle hot water passage 56 is connected to the valve fitting 6 without passing through the radiator 30. Throttle hot water passage 56 prevents freezing of throttle 22 and motor generator 24 by constantly flowing warm cooling water.

The transmission cooler 26 is a heat exchanger that exchanges heat between transmission oil and cooling water filled in the transmission to raise or cool the transmission oil. The engine oil cooler 28 is a heat exchanger that exchanges heat between engine oil filled in the internal combustion engine 2 and cooling water, and heats or cools the engine oil.

The transmission cooler 26 and the engine oil cooler 28 are connected to an engine oil cooler passage 58 that branches 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.

The radiator 30 includes an upper passage 30a (not shown), a radiator core 30b disposed downstream of the upper passage 30a, and a lower passage 30c disposed 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 cooling water and the outside air of the vehicle to cool the cooling water. The upper passage 30a of the radiator 30 is connected to a radiator passage 52 that is 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 a first radiator passage 52a and a second radiator passage 52b. Furthermore, the radiator passage 52 branches into a third radiator passage 52c that is connected to the supercharger cooling passage 60 upstream of the radiator 30.

The hot bottle 32 functions as a reservoir tank for temporarily storing cooling water, and is a tank for removing air from the cooling water. The upstream side of the hot bottle 32 is connected to the downstream side of the connection part between the third radiator passage 52c and the supercharger cooling passage 60 in the supercharger cooling passage 60. The downstream side of the hot bottle 32 is connected to the throttle hot water passage 56 downstream from the motor generator 24 . Cooling water that has passed through the supercharger 20 is supplied to the hot bottle 32 .

The control device 40 is a device that controls the flow rate control valve 4 according to 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, etc., and controls the flow rate of the cooling water. More specifically, the control device 40 determines the opening degree O of each passage, that is, the target rotation angle ωt of the rotary valve 4a, according to 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 cooling water flowing into the passage.

In the graph of FIG. 2, the horizontal axis shows the rotation angle ω of the rotary valve 4a, and the vertical axis shows the opening area (opening degree O). The control device 40 determines the target rotation angle ωt according to the water temperature WT, the driving 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 cooling water flowing into each passage is controlled. That is, determining the target rotation angle ωt is synonymous with determining the target opening degree Ot. During this time, the control device 40 acquires the actual rotation angle ωr of the rotary valve 4a from the rotation angle sensor provided in the flow control valve 4, and monitors whether the actual rotation angle is tracking.

Further, the flow rate control valve 4 of this embodiment has a first stopper that restricts the rotation of the rotary valve 4a at a position of the minimum rotation angle ωmin of the rotary valve 4a (for example, the -40 degree position in FIG. 2 in this embodiment). (an example of a regulatory department). Further, the flow rate control valve 4 has a second stopper (an example of a regulating portion) that regulates the rotation of the rotary valve 4a at the position of the maximum rotation angle ωmax (in this embodiment, for example, the position of 210 degrees in FIG. 2). The control device 40 controls the rotary valve 4a in the section from the first stopper to the second stopper.

Further, the control device 40 determines the introduction ratio of the exhaust recirculation gas, and controls the opening degree of the exhaust recirculation valve so that the introduction amount of the exhaust recirculation gas becomes the determined introduction ratio with respect to the intake air amount. The control device 40 may determine the introduction ratio of the exhaust recirculation gas based on a map that defines the introduction ratio of the exhaust recirculation gas for each operating region of the internal combustion engine 2.

In addition, the control device 40 controls the fuel injection valves 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). (not shown), an exhaust circulation valve (not shown), the supercharging pressure of the supercharger 20, and other devices may be controlled.

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

Next, the control procedure executed by the control device 40 will be explained using the flowchart of FIG. 3. Note that the control device 40 starts the control operation when an ignition switch (not shown) is turned on.

In step S1, the control device 40 acquires the water temperature WT. Upon acquiring the water temperature WT, the control device 40 advances the process to step S2, and sets the first target rotation angle (an example of the first target opening degree) ωt1 of the valve according to the driving state of the vehicle and the operating state of the internal combustion engine 2. Determine. The control device 40 acquires the difference between the first target rotation angle ωt1 and the actual rotation angle (an example of the actual opening degree) ωr, which is the current angle of the rotary valve 4a, and calculates the difference between the target rotation angle ωt and the actual rotation angle ωr. Based on this, the first rotational speed ωv1 at which the rotary valve 4a is moved is determined. The control device 40 determines the rotational speed ωv such that the larger the difference between the target rotational angle ωt and the actual rotational angle ωr, the larger the rotational speed ωv. After determining the rotational speed ωv, the control device 40 advances the process to step S3.

In step S3, the control device 40 determines whether the pressure of the cooling water flowing through each passage is at least a predetermined value, and in this embodiment, whether the rotation speed Er of the internal combustion engine 2 is at least 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 rotational speed Et is based on the rotational speed Er of the internal combustion engine 2 at which the pressure in each passage increases to such a pressure that there is a risk of hose disconnection as the rotation of the water pump 8 increases. It is determined. The predetermined rotation speed Et may be, for example, a rotation speed near a red zone that is set in a range from a rotation speed 1000 rpm lower than the allowable rotation speed of the internal combustion engine 2 to an allowable rotation speed. Further, the predetermined rotation speed Et may be a rotation speed slightly lower than the red zone. When the control device 40 determines that the rotation speed Er of the internal combustion engine 2 is equal to or higher than the predetermined rotation speed Et (step S3 YES), the control device 40 advances the process to step S4.

In step S4, the control device 40 establishes pressure relief control. As shown in FIG. 4, in this embodiment, the control device 40 determines that pressure relief control is necessary when the rotation speed Er of the internal combustion engine 2 is equal to or higher than the predetermined rotation speed Et, and records a flag for pressure relief control. . However, if the water pump 8 is an electric water pump, for example, the control device 40 may obtain the rotation speed of the water pump 8 and determine whether pressure relief control is necessary. Further, the control device 40 may measure the pressure of the cooling water flowing through each passage using a sensor or the like. Furthermore, in addition to the rotational speed Er of the internal combustion engine 2 or the rotational speed of the water pump 8, the control device 40 may take into account water temperature WT, etc., to determine whether pressure relief control is necessary. As shown in FIG. 3, upon establishing the pressure relief control, the control device 40 advances the process to step S5 and starts the pressure relief control.

In step S5, the control device 40 determines the second target rotation angle ωt2 (an example of the second target opening degree) at which the opening degree of each passage is the maximum, and also determines the second target rotation angle ωt2 that is larger than the second target rotation angle ωt2. A third target rotation angle (an example of the third target opening degree) ωt3 is determined. 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 radiator passage 52, the exhaust circulation gas cooler passage 54, and the engine oil cooler passage 58 ( The opening area of each passage) is maximized. Therefore, the control device 40 determines the second target rotation angle ωt2 when the rotation angle ω is between 150 degrees and 160 degrees. Furthermore, in the present embodiment, the control device 40 determines the third target rotation angle ωt3 to be the maximum rotation angle ωmax that is larger than the second target rotation angle ωt2. However, the third target rotation angle ωt3 may be any rotation angle ω larger 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 larger 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 advances the process to step S6.

In step S6, the control device 40 determines the 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.

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

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. Thereby, the control device 40 rotates the rotary valve 4a toward the second target rotation angle ωt2 at a third rotation speed ωv3 based on the difference between the actual rotation angle ωr and the second target rotation angle ωt2. After the control device 40 rotates the rotary valve 4a toward the second target rotation angle ωt2, the control device 40 advances the process to step S9.

In step S9, the control device 40 determines whether the actual rotation angle ωr matches the second target rotation angle ωt2. If the control device 40 determines that the actual rotation angle ωr does not match the second target rotation angle ωt2 (step S9 NO), the control device 40 returns the process to step S8 and rotates the rotary valve 4a toward the second target rotation angle ωt2. Keep moving. When the control device 40 determines that the actual rotation angle ωr matches the second target rotation angle ωt2 (step S9 YES), the process proceeds to step S10.

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 broken line from time t1 to time t2 in FIG. 4), the control device 40 can rotate the rotary valve 4a faster than 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 the position where the opening degree of each passage is maximum, and also adjusts the second target rotation angle by the inertia force of the rotary valve 4a. This prevents the rotary valve 4a from stopping due to deviation from ωt2. As a result, the control device 40 can quickly perform pressure relief control. Note that at this time, it is preferable to set the second target rotation angle ωt2 to a rotation angle ωt (150 degrees to 155 degrees) below the middle part of section A. Thereby, even if the rotation angle ωt exceeds the second target rotation angle ωt2 due to the inertia force of the rotary valve 4a from time t2 to time t3 in FIG. 4, the opening area of each passage can be easily maintained at the maximum state. .

In addition, in this embodiment, the rotary valve 4a is bypassed via the thermostat 5, and the second inlet 4c is connected to the valve fitting 6. The thermostat 5 is biased by a coil spring so as to close the second inlet 4c. In other words, the cooling system 1 for the internal combustion engine 2 has a bypass passage that connects from the second inlet 4c to the valve fitting 6 by bypassing the rotary valve 4a, which is an example of the flow control valve 4. A thermostat 5 is arranged on the bypass passage, which functions as a vent valve to release pressure from each passage. As a result, when the pressure in each passage increases beyond a predetermined pressure balanced with the biasing force of the coil spring, the thermostat 5 opens and the pressure in each passage can be released. By arranging the existing thermostat 5 in this way, it is possible not only to control the pressure but also to release the pressure in each passage using the thermostat 5.

In step S10, the control device 40 ends the pressure relief control. When the pressure of the cooling water flowing through each passage continues to be lower than a predetermined value (in this embodiment, the rotational speed of the internal combustion engine 2 is lower than a predetermined rotational speed) for a second predetermined period, the control device 40 performs pressure relief. End control. The second predetermined time may be any time when it can be determined that the rotation speed of the internal combustion engine 2 has stabilized below 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, pressure relief control is performed at that point. You may quit. When the control device 40 finishes the pressure relief control, it records the pressure relief control flag on the failure side as shown in FIG. 4 (see time t4 in FIG. 4). When the control device 40 records the flag on the non-established side, the control device 40 advances the process to step S11.

In step S11, the control device 40 determines a fourth target rotation angle (an example of a fourth target opening degree) 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 in order to gradually lower 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 rotationally moves the rotary valve 4a by the fourth target rotation angle ωt4 every predetermined time. As a result, the rotary valve 4a slowly rotates toward the first target rotation angle ωt1 at a constant third rotational speed ωv3. As a result, the occurrence of 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 any value that allows 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.

In step S12, the control device 40 moves the rotary valve 4a at the third rotational speed ωv3, and advances the process to step S13. In step S13, the control device 40 determines whether a first predetermined period of 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 pressure increase in each passage. If the control device 40 determines that the predetermined time has not elapsed (NO in step S13), the process returns to step S12 and rotates the rotary valve 4a toward the first target rotation angle ωt1 at the third rotation speed ωv3. continue. When the control device 40 determines that the first predetermined time has elapsed (step S13 YES), the process proceeds to step S14. In step S14, the control device 40 rotates the rotary valve 4a at the first rotational speed ωv1.

In step S3, if 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. After rotating the rotary valve 4a at the first rotational speed ωv1 in step S14, 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. If the control device 40 determines that the actual rotation angle ωr does not match the first target rotation angle ωt1 (NO in step S15), the control device 40 returns the process to step S14, and rotates the rotary valve 4a to the first target rotation at the first rotation speed ωv1. The rotational movement continues toward the angle ωt1. When the control device 40 determines that the actual rotation angle ωr matches the first target rotation angle ωt1 (step S15 YES), the process returns to step S1.

Note that even if the control device 40 determines in step S13 that the predetermined time has not elapsed (step S13 NO), the first target rotation angle ωt1 has changed to a rotation angle ω larger than the actual rotation angle ωr. In other words, if the degree of opening of each passage changes to become larger, the control device 40 may proceed to step S14. In such a case, since the rotary valve 4a rotates in a direction that increases the opening of each passage, the pressure in each passage decreases.

As explained above, according to the cooling system 1 for the internal combustion engine 2 of the present disclosure, the rotary valve 4a is controlled according to the difference between the first target rotation angle ωt1 to the fourth target rotation angle ωt4 and the actual rotation angle ωr. By doing so, optimal pressure relief control can be executed.

Further, according to the cooling system 1 for the internal combustion engine 2, by moving the rotary valve 4a at a third target rotation angle ωt3 that is larger than the second target rotation angle ωt2, the passage through which the cooling water flows is opened to the maximum more quickly. angle can be reached. Further, after the pressure release is completed, water hammer is prevented by slowly closing the rotary valve 4a at the fourth target rotation angle ωt4. As described above, according to the cooling system 1 for the internal combustion engine 2, in a system that determines the rotational speed of the rotary valve 4a according to the difference between the target rotational angle ωt and the actual rotational angle ωr, the optimum rotational speed can be achieved by simple control. Pressure relief control can be executed.

<Other embodiments>
Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various changes can be made without departing from the gist of the invention. In particular, the plurality of modifications described in this specification can be arbitrarily combined as necessary.

(a) In the above embodiment, the flow control valve 4 has been explained using the rotary valve 4a as an example, but the present disclosure is not limited thereto. The flow rate control valve 4 may be, for example, a slide type valve that controls the flow rate of each passage. In this case, the restriction portion may be a stopper that restricts movement of the sliding valve.

(b) The above embodiment is explained using an example in which the control device 40 controls the flow rate of cooling water flowing into each passage using the relationship between the opening area of each passage and the rotation angle ω of the rotary valve 4a shown in FIG. However, the present disclosure is not limited thereto. The control device 40 may control the flow rate control valve 4 using, for example, a sensor that detects the flow rate. Further, the area of the entrance of each passage and the rotation angle ω of the rotary valve 4a in FIG. 2 may be changed as appropriate.

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

Claims (6)

A cooling system for an internal combustion engine,
Multiple passages through which cooling water flows,
a flow control valve that controls the flow rate of cooling water flowing into each of the plurality of passages;
A target opening degree is determined while acquiring the temperature of the cooling water, and the larger the difference between the target opening degree and the actual opening degree, which is the actual opening degree of the flow rate control valve, the faster the speed at which the flow rate control valve is moved is determined. a control device that determines the speed so as to increase the speed, and controls the flow control valve according to the speed;
Equipped with
The control device controls the flow rate control valve according to a first target opening determined based on the temperature when the 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, the second target opening degree at which the opening degree of the plurality of passages becomes the maximum is determined, and a third target opening degree that is larger than the second target opening degree is determined. determine the opening degree, and execute pressure relief control to control the flow rate control valve using the third target opening degree,
When terminating the pressure relief control, controlling the flow rate control valve using a fourth target opening having a smaller difference from the actual opening than the first target opening;
Internal combustion engine cooling system. The control device controls the flow rate control valve using the fourth target opening degree until a first predetermined time period elapses after the pressure relief control ends, and after the first predetermined time elapses, the control device controls the flow rate control valve using the fourth target opening degree. controlling the flow rate control valve using a target opening degree;
A cooling system for an internal combustion engine according to claim 1. When executing the pressure relief control, the control device changes the second target opening from control using the third target opening when the actual opening reaches the second target opening. switch to the control used,
A cooling system for an internal combustion engine according to claim 1 or 2. a bypass passage that bypasses the flow control valve;
a vent valve provided in the bypass passage that opens at a predetermined pressure or higher;
further comprising;
A cooling system for an internal combustion engine according to any one of claims 1 to 3. the vent valve is a thermostat;
A cooling system for an internal combustion engine according to claim 4. The control device terminates the pressure relief control when a state in which the pressure of the cooling water is less than a predetermined time continues for a second predetermined time.
A cooling system for an internal combustion engine according to any one of claims 1 to 5.