JP7666382B2 - Cooling systems for internal combustion engines - Google Patents

Description

This disclosure relates to a cooling system for an internal combustion engine.

Internal combustion engine cooling systems have been known that have passages that supply cooling water to parts that require cooling, such as the cylinder head and exhaust gas recirculation system of the internal combustion engine (see, for example, Patent Document 1). Such internal combustion engine cooling systems have passages that supply cooling water to a radiator, and the cooling water is cooled by the radiator. Patent Document 1 discloses an internal combustion engine cooling system that has a flow control valve that controls the flow rate of each passage, and controls the flow of cooling water to an optimal flow rate in each passage.

JP 2020-176582 A

Patent Document 1 discloses a cooling system for an internal combustion engine that fully opens the flow control valve when the flow control valve fails, and releases the full opening when the water temperature drops. However, Patent Document 1 does not disclose control according to the type of failure of the flow control valve.

The objective of this disclosure is to provide a cooling system for an internal combustion engine that can perform optimal fail-safe control depending on the type of failure of the flow control valve.

The 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 through each of the plurality of passages, and a control device that determines a target opening based on the temperature of the cooling water flowing through the plurality of passages and controls the flow control valve toward the target opening. In the case of a first failure in which the opening of the flow control valve cannot be specified, the control device moves the flow control valve at a first speed, and in the case of a second failure in which the flow control valve does not follow the target opening, the control device sets the opening at which the cooling water flows through all of the passages as the target opening and moves the flow control valve.

According to this internal combustion engine cooling system, the way in which the flow control valve is moved is changed depending on whether a first failure occurs in which the position of the flow control valve cannot be identified, or whether a second failure occurs in which the flow control valve does not follow the target opening. This allows the flow control valve to be controlled according to the type of failure. As a result, optimal fail-safe control can be executed according to the type of failure of the flow control valve.

This disclosure provides a cooling system for an internal combustion engine that can perform optimal fail-safe control depending on the type of failure of the flow control valve.

1 is a system diagram of a cooling system for an internal combustion engine according to an embodiment of the present disclosure. 5 is a graph showing an example of a relationship between the rotation angle of the rotary valve and the opening area (opening degree) of each passage in the rotary valve according to an embodiment of the present disclosure. 4 is a flowchart showing a control procedure executed by a control device 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 description, the upstream side will be referred to as "upstream" and the downstream side will be referred to as "downstream" based on the direction in which the cooling water flows.

As shown in FIG. 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.

The cooling system 1 for the internal combustion engine 2 also includes multiple passages that supply cooling water to various devices. In this embodiment, the cooling system includes a main engine cooling passage 50, a radiator passage 52, an exhaust gas recirculation gas cooler passage (an example of an exhaust gas recirculation gas cooling passage) 54, a throttle hot water passage 56, an engine oil cooler passage 58, and a turbocharger cooling passage 60.

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.

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) that opens and closes 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 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 the paraffin wax. The thermostat 5 has a spring that biases the thermo valve in a direction that closes the second inlet 4c. The thermostat 5 may be an existing thermostat 5, and a more detailed description will be omitted.

The valve fitting 6 is a cylindrical member that is 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 that receives driving force from the crankshaft of the internal combustion engine 2 to rotate an impeller.

The 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. 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.

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 of the cooling water (water temperature WT) 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.

The internal combustion engine 2 of this embodiment is equipped 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 to the 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 (an example of an exhaust gas recirculation gas cooling device) 16 is a heat exchanger that cools the exhaust gas recirculation gas (see the dashed 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 cooling water. The heater core 18 is a heat exchanger of the air conditioning device (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 conditioning device 19 includes a blower fan 19a, and supplies the conditioned air warmed 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 obtain information transmitted from the control device 40. Similarly, the control device 40 can obtain information transmitted from the air conditioning control device 19b.

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

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

The throttle 22 is a device that controls the amount of intake air for the internal combustion engine 2. The motor generator 24 is a rotating electric machine that is connected to 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 allowing constantly heated cooling water to flow through it.

The transmission cooler 26 is a heat exchanger that exchanges heat between the transmission oil filled in the transmission and the cooling water, thereby heating or cooling 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 heating or cooling the engine oil.

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.

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 a first radiator passage 52a and a second radiator passage 52b. Additionally, the radiator passage 52 branches off into a third radiator passage 52c that is connected to the turbocharger cooling passage 60 upstream of the radiator 30.

The hot bottle 32 functions as a reservoir tank for temporarily storing cooling water, and is also a tank for bleeding air from the cooling water. The upstream side of the hot bottle 32 is connected to the turbocharger cooling passage 60 downstream of the connection between the third radiator passage 52c and the turbocharger cooling passage 60. The downstream side 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 cooling water that has passed through the turbocharger 20.

The control device 40 is a device that controls the flow control valve 4 in response to the water temperature WT obtained by the water temperature sensor 15, the running state of the vehicle, the operating state of the internal combustion engine 2, etc., 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 response 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 the cooling water flowing through each passage.

The graph in FIG. 2 shows the rotation angle ω of the rotary valve 4a on the horizontal axis and the opening area (opening degree O) on the vertical axis. 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 the rotation angle sensor provided in the flow control valve 4 and monitors whether the actual rotation angle is following.

The flow control valve 4 of this embodiment also 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). The flow control valve 4 also 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.

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 amount of exhaust recirculation gas introduced is the determined introduction rate relative to the intake air volume. 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.

In addition, the control device 40 may control each device, such as the fuel injection valve (not shown), 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).

The control device 40 is actually an ECU (Electronic Control Unit) that is composed of a microcomputer including an arithmetic unit, memory, an input/output buffer, etc. The control device 40 controls each device based on maps and programs 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 processing by software, and can also be processed by dedicated hardware (electronic circuits).

Next, the control procedure executed by the control device 40 will be described using the flowchart in FIG. 3. 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. After acquiring the water temperature WT, the control device 40 proceeds to step S2, where it determines a target rotation angle ωt of the valve that adjusts the opening degree of each passage according to the water temperature WT, the running state of the vehicle, and the operating state of the internal combustion engine 2. After determining the target rotation angle ωt, the control device 40 proceeds to step S3.

In step S3, the control device 40 obtains the difference between the target rotation angle ωt and the actual rotation angle ωr, which is the current angle of the rotary valve 4a, and determines the rotation speed ωv of the rotary valve 4a 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 S4.

In step S4, the control device 40 judges whether a position identification failure failure (an example of a first failure) has occurred in which the position of the rotary valve 4a (the opening degree of the flow control valve 4) cannot be identified. The control device 40 may judge whether a position identification failure failure has occurred based on the execution result of the first failure judgment control. For example, the control device 40 may execute the first failure judgment control in which the flow control valve 4 is moved toward the regulating portion and the flow control valve 4 is abutted against the regulating portion to judge a position identification failure failure, and may judge whether a position identification failure failure has occurred based on the execution result of the first failure judgment control. Specifically, the control device 40 continues to move the rotary valve 4a toward the first stopper and judges whether the actual rotation angle ωr is at the minimum rotation angle ωmin. Thereafter, the control device 40 continues to move the rotary valve 4a from the first stopper toward the second stopper and judges whether the actual rotation angle ωr of the rotary valve 4a is at the maximum rotation angle ωmax. If it is determined that the position of the rotary valve 4a is not at the minimum rotation angle ωmin or the maximum rotation angle ωmax, it is determined that a position identification failure has occurred, and a position identification failure flag is stored. The control performed in the above procedure is referred to as position identification failure failure determination control (an example of a first failure determination control). The control device 40 executes the position identification failure failure determination control when the ignition switch is turned off. If the control device 40 has stored a position identification failure flag, it determines that a position identification failure has occurred. If the control device 40 determines that a position identification failure has occurred (step S4 YES), it proceeds to step S5.

As shown in FIG. 2, the control device 40 moves the rotary valve 4a from the first stopper toward the second stopper in this manner and executes the position identification failure failure judgment control, so that after executing the position identification failure failure judgment control, the rotary valve 4a moves in the direction in which the opening of the radiator passage 52 becomes larger. This makes it easier to ensure the flow rate of cooling water to the radiator passage 52 even when the position identification failure failure judgment control determines that a position identification failure failure has occurred. As a result, the control device 40 can execute safer position identification failure failure judgment control.

In addition to the above-mentioned position identification failure determination control, the determination of a position identification failure may also include a determination of a power fault or ground fault of the rotation angle sensor. A power fault of the rotation angle sensor may be determined by whether or not a state in which the output of the rotation angle sensor is equal to or higher than a first output that is not output under normal control continues for a predetermined period of time, and a ground fault may be determined by whether or not a state in which the output of the rotation angle sensor is equal to or lower than a second output that is not output under normal control continues for a predetermined period of time. The determination of a power fault or ground fault may be performed at all times while the internal combustion engine is running.

As shown in FIG. 3, in step S5, the control device 40 executes the first control to rotate the flow control valve 4 at a first speed ωv1 without determining the target opening Ot (target rotation angle ωt). In this embodiment, the first speed ωv1 is an angular speed at which the rotary valve 4a is rotated. The first speed ωv1 is a predetermined angular speed at which the rotary valve 4a can be safely rotated. In other words, in step S5, the control device 40 does not determine the target rotation angle ωt, and rotates the rotary valve 4a at a constant angular speed (an example of the first speed ωv1). As a result, even if the position of the rotary valve 4a cannot be specified, the rotary valve 4a safely moves to the first stopper or the second stopper. In this embodiment, the movement of the rotary valve 4a in this step is executed when the ignition switch is turned off.

In this embodiment, the rotary valve 4a is rotated toward the second stopper. This increases the opening area of the radiator passage 52 as shown in FIG. 2. As a result, even if a location identification failure occurs, the flow rate of the cooling water passing through the radiator can be ensured, and the internal combustion engine 2 can be cooled. As shown in FIG. 3, after the control device 40 executes the first control in step S5, the process proceeds to step S6.

In step S6, the control device 40 judges whether a predetermined time has elapsed since the rotary valve 4a started to rotate. The predetermined time is, for example, the time required for the rotary valve 4a to move from -40 degrees to 210 degrees when it is rotated at the first speed ωv1. In other words, the predetermined time may be the time required for the rotary valve 4a to hit the second stopper when it is moved at the first speed ωv1. This makes it possible to maximize the opening area of the radiator passage 52 even if a position identification failure occurs, and to reduce the power required for this. If the control device 40 judges that the predetermined time has elapsed (step S6 YES), it proceeds to step S7. If the control device 40 judges that the predetermined time has not elapsed (step S6 NO), it returns to step S5 and continues the rotational movement of the rotary valve 4a.

In step S7, the control device 40 executes a first output limiting control that limits the output of the internal combustion engine 2 to a first output that is lower than a second output, which will be described later. In the case of a poor location identification failure, it is difficult to control the temperature of the cooling water. For this reason, it is preferable to suppress the amount of heat generated by the internal combustion engine 2 as much as possible. Therefore, the control device 40 suppresses the output of the internal combustion engine 2 and suppresses the amount of heat generated by limiting it to the first output. The first output may be, for example, an output (limp form output) that is sufficient to evacuate the vehicle to a safe place. After executing the first output limiting control, the control device 40 proceeds to step S8.

In step S8, the control device 40 closes the exhaust recirculation valve of the exhaust recirculation device 17 to stop the exhaust recirculation gas. As shown in FIG. 2, in this embodiment, the position of the second stopper corresponds to the position where the rotary valve 4a closes (closes) the passage of the exhaust recirculation gas cooler passage 54. Therefore, cooling water cannot be supplied to the exhaust recirculation gas cooler 16. As a result, the control device 40 stops the introduction of the exhaust recirculation gas to protect the exhaust recirculation device 17 and the internal combustion engine 2. After the control device 40 stops the introduction of the exhaust recirculation gas, the process proceeds to step S9.

Note that steps S7 and S8 may be processed in parallel with step S5. That is, when the control device 40 determines that a position identification failure has occurred, it may rotate the flow control valve 4 at the first speed ωv1, limit the output of the internal combustion engine 2 to the first output, and close the exhaust recirculation valve of the exhaust recirculation device 17. Also, the order of steps S5, S7, and S8 may be reversed.

In step S9, the control device 40 determines whether the position identification failure failure has been resolved. In this embodiment, the control device 40 determines that the position identification failure failure has been resolved when the position identification failure failure flag has disappeared. However, the control device 40 may determine that the position identification failure failure has been resolved by other methods. If the control device 40 determines that the position identification failure failure has been resolved (step S9 YES), it returns the process to step S1. If the control device 40 determines that the position identification failure failure has not been resolved (step S9 NO), it proceeds to step S7 and continues the first output limit control and the stop of the introduction of exhaust recirculation gas.

In step S4, if the control device 40 determines that the failure is not a position identification failure, which is the first failure (step S4 NO), the process proceeds to step S10. In step S10, the control device 40 determines whether or not the failure is a tracking failure (an example of a second failure). A tracking failure is a failure in which the flow control valve 4 does not follow the target opening Ot. In this embodiment, the control device 40 determines that a tracking failure has occurred when the actual rotation angle ωr of the rotary valve 4a does not follow the target rotation angle ωt (a state in which the difference between the actual rotation angle ωr and the target rotation angle ωt is greater than or equal to a predetermined value continues for a predetermined period of time). On the other hand, in the case of a tracking failure, the control device 40 is able to identify the position of the rotary valve 4a. The control device 40 constantly determines a tracking failure while the internal combustion engine is running. If the control device 40 determines that a tracking failure has occurred (step S10 YES), the process proceeds to step S11. If the control device 40 determines that the failure is not due to poor tracking (step S10 NO), it returns the process to step S1.

In step S11, the control device 40 rotates the rotary valve 4a toward a position where the opening degree O of each passage is maximum at the rotation speed ωv (an example of the second speed) determined in step S3. As shown in FIG. 2, in this embodiment, when the rotation angle ω is between 150 degrees and 160 degrees, the opening area (opening degree) of the radiator passage 52, the exhaust gas recirculation cooler passage 54, and the engine oil cooler passage 58 (each passage) is maximum. The control device 40 determines the target rotation angle ωt to be between 150 degrees and 160 degrees, and rotates the rotary valve 4a at a rotation speed ωv based on the difference between the target rotation angle ωt and the actual rotation angle ωr. This allows the control device 40 to move the rotary valve 4a as quickly as possible to a safe valve opening position that can prevent overheating of the internal combustion engine 2. In addition, in the case of a poor tracking failure, there are cases where the rotary valve 4a cannot move due to clogging, but by attempting to move the rotary valve 4a as described above, the clogging may be cleared and tracking may be restored. If tracking does not return, the rotary valve 4a may not reach the target rotation angle ωt, so if the target rotation angle ωt is not reached even after a predetermined time considering the load on the rotary valve 4a has elapsed, the movement of the rotary valve 4a may be terminated. As shown in FIG. 3, after the control device 40 rotates and moves the rotary valve 4a, the process proceeds to step S12.

In step S12, the control device 40 executes a second output limiting control that limits the output of the internal combustion engine 2 to a second output corresponding to the target opening degree Ot. In this embodiment, the output is limited to the second output corresponding to the target rotation angle ωt determined in step S11. The target rotation angle ωt determined in step S11 is the position where the opening degree O of each passage is maximum. Therefore, even if the second output is higher than the first output, overheating of the internal combustion engine 2 does not occur. Therefore, the second output may be, for example, higher than the limp form output and less than the full throttle output of the internal combustion engine 2. After executing the second output limiting control, the control device 40 proceeds to step S13.

In step S13, the control device 40 determines whether the poor tracking failure has been resolved. The control device 40 may determine that the poor tracking failure has been resolved when the actual rotation angle ωr of the rotary valve 4a resumes tracking the target rotation angle ωt. If the control device 40 determines that the poor tracking failure has been resolved (step S13 YES), it returns the process to step S1. If the control device 40 determines that the poor tracking failure has not been resolved (step S13 NO), it returns the process to step S12 and continues the second output limit control.

As described above, according to the cooling system 1 for the internal combustion engine 2 disclosed herein, the manner in which the rotary valve 4a is moved is changed depending on whether a position identification failure occurs or a tracking failure occurs. Specifically, in the case of a position identification failure, the control device 40 does not know whether the target rotation angle ωt has been reached, so it moves the rotary valve 4a toward the open side without determining the target rotation angle ωt. On the other hand, in the case of a tracking failure, the control device 40 knows that the target rotation angle ωt has been reached. Therefore, the control device 40 sets the rotary valve 4a to the safest opening. This allows the rotary valve 4a to be controlled in accordance with the failure mode. As a result, optimal fail-safe control can be executed in accordance with the failure mode of the rotary valve 4a.

Furthermore, the control device 40 executes a first output limiting control and a second output limiting control according to the failure mode. This allows the output limiting to be executed according to the flow rate of the cooling water.

<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.

(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 regulating portion may be a stopper that regulates the movement of the slide-type valve.

(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.

1: Cooling system 2: Internal combustion engine 4: Flow control valve 17: Exhaust gas recirculation device 30: Radiator 40: Control device 52: Radiator passage 54: Exhaust gas recirculation gas cooler passage O: Opening degree Ot: Target opening degree ωmax: Maximum rotation angle ωmin: Minimum rotation angle ωr: Actual rotation angle ωt: Target rotation angle ωv: Rotational speed ωv1: First speed

Claims (7)

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 determines a target opening degree based on temperatures of cooling water flowing through the plurality of passages and controls the flow control valve toward the target opening degree;
Equipped with
When a first failure occurs in which the opening degree of the flow control valve cannot be identified, the control device moves the flow control valve at a first speed;
In the case of a second failure in which the flow control valve does not follow the target opening, the flow control valve is moved to set the target opening to an opening at which the cooling water flows through all of the passages.
Cooling system of an internal combustion engine. the controller moves the flow control valve at the first speed for a predetermined time in the event of the first fault;
2. The cooling system for an internal combustion engine according to claim 1. When the second failure occurs, the control device moves the flow control valve to the target opening at a second speed determined according to a difference between the target opening and an actual opening.
3. A cooling system for an internal combustion engine according to claim 1 or 2. The control device includes:
When it is determined that the second malfunction has occurred, a second output limiting control is executed to limit the output of the internal combustion engine to a second output corresponding to the target opening degree;
when it is determined that the first malfunction has occurred, a first output limiting control is executed to limit an output of the internal combustion engine to a first output which is lower than the second output.
4. A cooling system for an internal combustion engine according to claim 1. Further comprising an exhaust gas recirculation device;
When the control device determines that the first malfunction has occurred, the control device stops exhaust gas recirculation by the exhaust gas recirculation device.
5. A cooling system for an internal combustion engine according to any one of claims 1 to 4. the plurality of passages includes a radiator passage that supplies the cooling water to a radiator,
the flow control valve has a restriction portion that restricts a position of the flow control valve to a position where the radiator passage has a maximum opening degree,
The control device executes a first fault determination control to move the flow control valve toward the restriction portion and to abut the flow control valve against the restriction portion to determine the first fault.
5. A cooling system for an internal combustion engine according to any one of claims 1 to 4. An exhaust gas recirculation device;
an exhaust gas recirculation gas cooling device that cools the exhaust gas recirculated by the exhaust gas recirculation device;
Further equipped with
the plurality of passages include an exhaust recirculation gas cooling passage that supplies cooling water to the exhaust recirculation gas cooling device,
the restriction portion corresponds to a position where the flow control valve closes the exhaust recirculation gas cooling passage,
When the control device determines that the first malfunction has occurred, the control device stops exhaust gas recirculation by the exhaust gas recirculation device.
7. The cooling system for an internal combustion engine according to claim 6.