JP6079764B2 - Internal combustion engine cooling system and control method thereof - Google Patents

Description

  The present invention relates to a cooling system for an internal combustion engine and a control method therefor.

  In the engine cooling system, a first path for circulating cooling water so as to pass inside the engine (specifically, a water jacket) and a second path for circulating cooling water so as to bypass the engine A configuration including a route is known. A valve is provided between the downstream side of the engine of the first path and the second path. If the valve is closed when the engine is in the first state, the flow of the cooling water in the first path is interrupted, so that the engine can be suitably warmed up.

  On the other hand, if the valve is closed and the circulation of the cooling water is completely blocked, the temperature distribution in the cooling water in the engine may become uneven. Therefore, a hole is formed in the valve body of the valve. Thereby, even if the valve is closed, a small amount of cooling water is ensured through the hole. However, since foreign matter or the like may be clogged in the hole, a technique for estimating the clogging amount of the hole has been proposed (for example, see International Publication No. 2013/190619 (Patent Document 1)).

International Publication No. 2013/190619 International Publication No. 2011-067333

  Whether or not a flow passage (for example, a hole) for flowing a small amount of cooling water is clogged can be determined by detecting a temperature rise of the cooling water when the engine is started in a valve closed state. it can. More specifically, a water temperature sensor is provided between the engine and the valve (on the downstream side of the engine and the upstream side of the valve). When the flow part is not clogged, a small amount of cooling water can flow through the flow part even when the valve is closed. Therefore, even if the elapsed time from the start of the engine is relatively short, the cooling water warmed by the engine reaches the place where the water temperature sensor is installed. Thereafter, the temperature of the cooling water detected by the water temperature sensor increases with time.

  As the amount of clogging in the circulation part increases, the cooling water becomes difficult to circulate. Therefore, the time (response time) required for the cooling water warmed by the engine to reach the water temperature sensor and the temperature increase of the cooling water is detected becomes longer. When the flow of the cooling water is completely blocked by the foreign matter, it takes a long time to detect the temperature rise of the cooling water. Thus, there is a correlation between the clogging amount of the circulation part and the response time. Therefore, it is possible to determine whether or not the circulation portion is clogged by detecting the temperature rise of the cooling water using the water temperature sensor.

  When such a determination method is employed, the water temperature sensor may deteriorate and an abnormality may occur. If a water temperature sensor in which an abnormality (specifically, a deterioration in response characteristics for detecting an increase in the temperature of the cooling water) occurs is used, the response time becomes longer than when a normal water temperature sensor is used. As a result, there is a possibility that it is erroneously determined that the hole is clogged even though the hole is not actually clogged.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to prevent an erroneous determination that a clogging portion has occurred in a cooling system for an internal combustion engine.

  An internal combustion engine cooling system according to an aspect of the present invention includes a first path for circulating cooling water so as to pass through the interior of the internal combustion engine, and a first path for circulating cooling water so as to bypass the internal combustion engine. 2 path | route, a valve | bulb, a distribution part, a water temperature sensor, and the control apparatus which controls the opening degree of a valve | bulb. The valve is provided between the second path and the downstream side of the internal combustion engine of the first path, and circulates the first path to the cooling water flowing through the second path as the opening degree is increased. The amount of cooling water to be mixed is increased. The circulation unit causes a small amount of cooling water to flow through the first path even when the opening of the valve is lower than the first predetermined value. The water temperature sensor is provided between the internal combustion engine and the valve in the first path, and detects the temperature of the cooling water flowing through the first path. When the opening degree of the valve is lower than the first predetermined value, the control device determines whether the flow rate of the flow unit is based on the relationship between the change in the temperature of the cooling water detected by the water temperature sensor and the predetermined determination value. It is determined whether clogging has occurred. The control device learns the response characteristic of the water temperature sensor from the start of the internal combustion engine when the opening degree of the valve exceeds the second predetermined value that is larger than the first predetermined value. Further, the control device corrects the determination value using the learning result.

  In a control method for a cooling system for an internal combustion engine according to another aspect of the present invention, the cooling system bypasses the internal combustion engine with a first path for circulating cooling water so as to pass through the interior of the internal combustion engine. A second path for circulating the cooling water, a valve, a circulation part, and a water temperature sensor are provided. The valve is provided between the second path and the downstream side of the internal combustion engine of the first path, and circulates the first path to the cooling water flowing through the second path as the opening degree is increased. The amount of cooling water to be mixed is increased. The circulation unit causes a small amount of cooling water to flow through the first path even when the opening of the valve is lower than the first predetermined value. The water temperature sensor is provided between the internal combustion engine and the valve in the first path, and detects the temperature of the cooling water flowing through the first path. When the opening degree of the valve is lower than the first predetermined value, the control method is based on the relationship between the time variation of the temperature of the cooling water detected by the water temperature sensor and the predetermined determination value. The step of determining whether clogging has occurred and the response of the water temperature sensor from the start of the internal combustion engine when the opening of the valve exceeds a second predetermined value greater than the first predetermined value A step of learning characteristics, and a step of correcting the determination value using the learning result.

  Preferably, the control device is a time required for the temperature of the cooling water detected by the water temperature sensor to increase by a predetermined temperature from the start of the internal combustion engine in a state where the opening degree of the valve is lower than the first predetermined value. If a certain response time exceeds the determination value, it is determined that the distribution unit is clogged. On the other hand, when the response time is less than the determination value, the control device determines that the clogging of the distribution unit has not occurred. More preferably, the control device learns the response characteristic based on a response time when the water temperature sensor is normal.

  Preferably, in a state in which the opening degree is less than the first predetermined value, the control device causes clogging of the circulation portion when the temperature increase amount within a predetermined period of the cooling water detected by the water temperature sensor is lower than the determination value. It is determined that On the other hand, the control device determines that the clogging of the flow section has not occurred when the temperature increase amount exceeds the determination value. More preferably, the control device learns the response characteristic with reference to a temperature rise amount when the water temperature sensor is normal.

  Preferably, the flow part is a hole formed in the valve body of the valve or a path formed so as to bypass the valve.

  In a state where the valve opening is lower than a first predetermined value (for example, in a closed state), the temperature change of the cooling water detected by the water temperature sensor (more specifically, the response time until a predetermined temperature rise occurs) Alternatively, the temperature rise amount within a predetermined period is determined according to whether or not the flow portion is clogged (that is, the flow rate of the cooling water) and the response characteristics of the water temperature sensor. On the other hand, in a state where the opening degree of the valve exceeds the second predetermined value (for example, an open state), the flow rate of the cooling water flowing through the valve is substantially equal regardless of whether or not the flow part is clogged. Therefore, the time change of the temperature of the cooling water in the open state of the valve is determined exclusively according to the response characteristic of the water temperature sensor. According to the above configuration and method, the response characteristic of the water temperature sensor is learned by opening the valve. And the determination value for determining in the closed state of a valve whether the clogging of a distribution part has arisen using the result of the learning is amended. Thereby, the influence of the deterioration of the response characteristic of a water temperature sensor can be excluded. Therefore, it is possible to prevent erroneous determination that the clogging of the distribution unit has occurred.

  ADVANTAGE OF THE INVENTION According to this invention, the misjudgment that the clogging of the distribution part has arisen in the cooling system of an internal combustion engine can be prevented.

1 is a block diagram schematically showing an overall configuration of a vehicle equipped with an engine cooling system according to an embodiment. It is a block diagram for demonstrating the structure of a cooling system in detail. It is a figure for demonstrating switching of a cooling water path | route. It is a figure for demonstrating the structure of an electromagnetic valve in detail. It is a figure for demonstrating the temperature distribution of the cooling water according to the presence or absence of clogging of a hole. It is a figure for demonstrating the determination method of whether the clogging of the hole has arisen. It is a figure for demonstrating the relationship between the flow volume of a cooling water, and response time. It is a time chart which shows an example of the calculation method of the delay of the response time resulting from the deterioration of the response characteristic of a water temperature sensor in the open state of an electromagnetic valve. It is a figure for demonstrating the correction method of the deterioration of the response characteristic of a water temperature sensor in the closed state of an electromagnetic valve. It is a flowchart for demonstrating control of the cooling system in this Embodiment. It is a flowchart for demonstrating learning control of a water temperature sensor. It is a flowchart for demonstrating determination control. It is a time chart which shows an example of the calculation method of the delay of the response time resulting from the deterioration of the response characteristic of the water temperature sensor based on the modification of this Embodiment. It is a figure for demonstrating the correction method of the deterioration of the response characteristic of a water temperature sensor based on the modification of this Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment]
<Overall configuration of vehicle>
FIG. 1 is a block diagram schematically showing the overall configuration of a vehicle equipped with an engine cooling system according to the present embodiment. Referring to FIG. 1, vehicle 1 is a hybrid vehicle, and includes an engine 100, a cooling system 200, a first motor generator (MG) 10, a second MG 20, a power split mechanism 30, and a deceleration. Machine 40, power control unit (PCU) 50, battery 60, electronic control unit (ECU) 300, and drive wheel 350.

  The vehicle 1 can travel with the driving force output from at least one of the engine 100 and the second MG 20. Engine 100 includes an internal combustion engine such as a gasoline engine or a diesel engine. When engine 100 is started by cranking of first MG 10, it supplies power to at least one of drive wheels 350 and first MG 10 via power split mechanism 30.

  Cooling system 200 cools engine 100 by conducting heat generated in engine 100 to cooling water. A detailed configuration of the cooling system 200 will be described later with reference to FIGS.

  The engine 100 is provided with an engine rotation speed sensor 102. Engine rotation speed sensor 102 detects a rotation speed (engine rotation speed) Ne of engine 100 and outputs a signal indicating the detection result to ECU 300. ECU 300 determines whether to drive or stop engine 100 based on engine rotational speed Ne.

  Each of first MG 10 and second MG 20 is a three-phase AC rotating electric machine in which, for example, a permanent magnet is embedded in a rotor (both not shown). First MG 10 can generate power using the power of engine 100 received through power split mechanism 30. For example, when the SOC (State Of Charge) of battery 60 reaches a predetermined lower limit value, engine 100 is started and power is generated by first MG 10. The electric power generated by the first MG 10 is converted into a voltage by the PCU 50 and stored in the battery 60 or directly supplied to the second MG 20.

  Second MG 20 generates driving force using at least one of the electric power stored in battery 60 and the electric power generated by first MG 10. The driving force of second MG 20 is applied to driving wheel 350 via the propeller shaft.

  Power split mechanism 30 is, for example, a planetary gear mechanism, and is configured to be able to split the driving force generated by engine 100 into power for driving drive wheels 350 and power for driving first MG 10. Reducer 40 transmits the power from power split mechanism 30 or second MG 20 to drive wheels 350.

  PCU 50 is a drive device for driving first MG 10 and second MG 20 based on a control signal from ECU 300. Although not shown, PCU 50 includes an inverter for converting a voltage between battery 60 and first MG 10 and an inverter for converting a voltage between battery 60 and second MG 20. PCU 300 may further include a converter (not shown) for boosting or stepping down a DC voltage between battery 60 and the inverter.

  The battery 60 is a rechargeable DC power supply, and includes a secondary battery such as a lithium ion battery or a nickel metal hydride battery, or a capacitor such as an electric double layer capacitor.

  ECU 300 includes a CPU (Central Processing Unit), a memory, and a buffer (all not shown). ECU 300 outputs a control signal based on input of signals from each sensor and a map and a program stored in the memory, and controls each device so that vehicle 1 is in a desired state.

<Configuration of cooling system>
FIG. 2 is a block diagram for explaining the configuration of the cooling system 200 in detail. Referring to FIG. 2, engine body 110 includes a cylinder block 112, a cylinder head 114 (see FIG. 5), and the like. The engine main body 110 is provided with a water jacket 210. When the engine body 110 is hot, the engine body 110 can be cooled by circulating cooling water through the water jacket 210. On the contrary, when the temperature of the cooling water is higher than the temperature of the engine body 110, the engine body 110 can be warmed up earlier by circulating the cooling water.

  The cooling system 200 is provided with a water pump (W / P) 220 for circulating the cooling water in the cooling water path. Although not shown, the water pump 220 includes an impeller that sends cooling water by rotating, and an electric motor that rotates the impeller. The rotation speed of the electric motor is controlled according to a control signal Wp from ECU 300. Thereby, the discharge amount (or discharge pressure) per unit time of the cooling water from the water pump 220 can be changed.

  The cooling water path includes a supply path 232 (232A, 232B), a return path 234 (234A, 234B), a bypass path 236 (236A, 236B), and a branch path 238 (238A, 238B). Yes.

  The supply path 232 is a path for supplying cooling water from the water pump 220 to the water jacket 210. The return path 234 is a path for returning the cooling water flowing through the water jacket 210 to the water pump 220. The bypass path 236 is a path for circulating the cooling water so as to bypass the water jacket 210. The branch path 238 connects the return path 234A and the bypass path 236. The supply path 232B, the return path 234A, and the branch path 238 correspond to the “first path” according to the present invention. The bypass path 236 corresponds to a “second path” according to the present invention.

  A water temperature sensor 240, a radiator 250, a thermostat 260, and an electromagnetic valve 270 are provided in the cooling water path.

  The water temperature sensor 240 is provided in the vicinity of the connection portion between the water jacket 210 and the return path 234A. The water temperature sensor 240 detects the temperature (water temperature) Tw of the cooling water flowing through the return path 234A, and outputs a signal indicating the detection result to the ECU 300. ECU 300 determines whether cooling or warm-up of engine 100 has been completed based on water temperature Tw. Further, ECU 300 changes the opening degree of electromagnetic valve 270 according to the determination result.

  The radiator 250 is provided downstream of the water temperature sensor 240 in the return path 234A. The radiator 250 radiates the heat of the cooling water to the outside air by heat exchange between the cooling water flowing through the radiator 250 and the outside air.

  The thermostat 260 is provided so as to connect the return path 234 and the bypass path 236B. The opening degree of the thermostat 260 is automatically adjusted according to the temperature of the cooling water flowing through the thermostat 260. The thermostat 260 is opened when the cooling water is hot, while the thermostat 260 is closed when the cooling water is cold. The thermostat 260 is configured to allow the coolant to flow from the bypass path 236B toward the return path 234B regardless of the temperature of the coolant.

  The electromagnetic valve 270 is provided on the branch path 238. In other words, the electromagnetic valve 270 is provided between the return path 234A and the bypass path 236B. The electromagnetic valve 270 is configured such that the amount of the cooling water flowing through the return path 234A to the cooling water flowing through the bypass path 236B increases as the opening of the electromagnetic valve 270 increases.

  In the following, for simplification of description, a state where the electromagnetic valve 270 is completely closed will be typically described as the “closed state” of the electromagnetic valve 270. Further, as an “open state” of the electromagnetic valve 270, a state where the opening degree of the electromagnetic valve 270 is the largest will be described representatively. However, the “closed state” of the electromagnetic valve 270 is not limited to the state where the electromagnetic valve 270 is fully closed, and the opening degree of the electromagnetic valve 270 is equal to or less than a predetermined value V1 (first predetermined value). I just need it. Similarly, the “open state” of the electromagnetic valve 270 is not limited to the state in which the electromagnetic valve 270 is fully opened, but the opening degree of the electromagnetic valve 270 is greater than a predetermined value V1 (second predetermined value). Value) or more.

  In cooling system 200 configured as described above, first to third states exist depending on the warm-up condition of engine 100. And a cooling water path | route is switched according to each state.

  FIG. 3 is a diagram for explaining switching of the cooling water path. 2 and 3, switching of the cooling water path is realized by changing the opening of electromagnetic valve 270 based on the cooling water temperature Tw and automatically adjusting the opening of thermostat 260. Is done. As the coolant temperature Tw, a first temperature corresponding to a state where the engine 100 is warmed up and a second temperature slightly lower than the first temperature are predetermined. In FIG. 3, “O” indicates that each path indicated by arrows AR1 to AR3 is formed, and “X” indicates that each path is not formed.

  (1) The first state is a state in which the water temperature Tw is lower than the second temperature, for example, immediately after the engine 100 is started. In the first state, since the thermostat 260 is closed, the inflow of cooling water to the radiator 250 is prohibited. The electromagnetic valve 270 is controlled to be closed by the ECU 300. Therefore, the cooling water circulates mainly through the water pump 220-supply path 232A-bypass path 236A, 236B-thermostat 260-return path 234B-water pump 220 as shown by an arrow AR1 in FIG. As described above, in the first state, the flow rate of cooling water flowing through the water jacket 210 per unit time (hereinafter abbreviated as “flow rate”) is reduced, so that warm-up of the engine 100 is promoted.

  (2) The second state is a state where the water temperature Tw is equal to or higher than the second temperature and lower than the first temperature, that is, a state where the warm-up is not completed. Even in the second state, since the thermostat 260 is closed, the inflow of the cooling water to the radiator 250 is prohibited. On the other hand, the electromagnetic valve 270 is controlled to be opened by the ECU 300. Therefore, as shown by the arrow AR2, a part of the cooling water is water pump 220-supply path 232A, 232B-water jacket 210-branch path 238A-electromagnetic valve 270-branch path 238B-bypass path 236B-thermostat 260-return. The path 234B is circulated. As a result, engine 100 can be warmed up more slowly than in the first state. The remaining cooling water circulates along the path indicated by the arrow AR1.

  (3) The third state is a state where the water temperature Tw is equal to or higher than the first temperature and the warm-up is completed. In the third state, since the thermostat 260 is opened, the cooling water is allowed to flow into the radiator 250. Therefore, the cooling water is mainly water pump 220-supply path 232A, 232B-water jacket 210-return path 234A-radiator 250-return path 234A-thermostat 260-return path 234B-water pump 220 as indicated by arrow AR3. Cycle through the path. Further, since the electromagnetic valve 270 is controlled to be in an open state, a part of the cooling water circulates along a path indicated by an arrow AR2. The remaining cooling water circulates along the path indicated by the arrow AR1.

  FIG. 4 is a diagram for explaining the configuration of the electromagnetic valve 270 in detail. 4A shows the open state of the electromagnetic valve 270, and FIG. 4B shows the closed state of the electromagnetic valve 270.

  Referring to FIGS. 2, 4 (A) and 4 (B), electromagnetic valve 270 includes an electric actuator 272. The electric actuator 272 changes the opening degree of the electromagnetic valve 270 in response to the control signal Vo from the ECU 300.

  A hole 276 is formed in the valve body 274 of the electromagnetic valve 270. Even when the electromagnetic valve 270 is in the closed state, the cooling water flows through the hole 276, whereby the cooling water flow in the branch path 238 (that is, the cooling water flow in the water jacket 210) can be ensured.

  However, the configuration for ensuring the circulation of the cooling water is not limited to this. For example, as shown in FIG. 4C, a path 278 through which a small amount of cooling water can be circulated may be formed. The path 278 is formed so as to bypass the branch path 238 at the installation location of the valve body 274. Hereinafter, a configuration in which the hole 276 is formed in the valve body 274 will be described, but the hole 276 can be appropriately read as the path 278.

<Clogged hole>
It is known that the hole 276 may be clogged with foreign matter or the like. Whether or not the hole 276 is clogged can be determined based on the temperature increase of the water temperature Tw detected by the water temperature sensor 240 when the electromagnetic valve 27 is in the closed state.

  FIG. 5 is a diagram for explaining the temperature distribution of the cooling water according to the presence or absence of clogging of the holes 276. As shown by arrows ARin and ARout in FIG. 5A, the water jacket 210 is configured such that cooling water flows in from the cylinder block 112 side and flows out from the cylinder head 114 side. The cylinder head 114 portion of the water jacket 210 has a longitudinal direction and a lateral direction. The longitudinal direction is indicated by P.

  FIG. 5B shows an example of the temperature distribution of the cooling water along the longitudinal direction P. With reference to FIG. 2 and FIG. 5 (B), it is assumed that engine 100 is stopped and in the first state. Therefore, both the thermostat 260 and the electromagnetic valve 270 are closed. As shown by a curve N0, it is assumed that the temperature distribution of the cooling water before the engine 100 is started is uniform.

  When the hole 276 is not clogged, a small amount of cooling water flows through the cooling water path. Therefore, when the engine 100 is started, the cooling water is warmed while flowing through the cooling water path. As shown by the curve N1, the coolant temperature is the lowest in the uppermost stream of the cooling water path and becomes higher toward the downstream side. Since the water temperature sensor 240 is provided on the most downstream side of the cooling water path, the water temperature Tw of the cooling water detected by the water temperature sensor 240 increases by T1 based on the state before the engine 100 is started (see the curve N0). To do.

  On the other hand, when the hole 276 is clogged and the circulation of the cooling water is interrupted, the temperature of the cooling water becomes the highest at the central portion in the longitudinal direction P of the cooling water path as shown by the curve N2. However, the cooling water heated in the central portion hardly flows downstream. As a result, heat transfer is less likely to occur, so that the cooling water temperature Tw at the most downstream is lower than the water temperature at the central portion. Therefore, when the elapsed time from the start of the engine 100 is equal, the increase amount T2 of the water temperature Tw when the hole 276 is clogged is larger than the increase amount T1 of the water temperature Tw when the hole 276 is not clogged. Get smaller. As described above, when the hole 276 is clogged, the water temperature Tw is less likely to rise than when the hole 276 is not clogged.

  FIG. 6 is a diagram for explaining a method for determining whether or not the hole 276 is clogged. The horizontal axis of FIG. 6 and FIGS. 8 and 9 described later indicates the elapsed time. 6, 8, and 9, the vertical axis indicates the temperature increase ΔTw of the coolant temperature Tw based on the opening degree of the electromagnetic valve 270, the engine rotation speed Ne, and the state before starting the engine 100 in order from the top. Indicates.

  Referring to FIG. 6, at start time (0), for example, engine 100 is stopped and is in the first state. Therefore, both the thermostat 260 and the electromagnetic valve 270 are closed.

  A curve L1 represents an example of a temporal change in the temperature increase ΔTw when the hole 276 is not clogged at all. When the engine 100 is started at time t0, a small amount of cooling water flows through the branch path 238 through the hole 276, so that the temperature of the cooling water starts increasing at a relatively early time t10. The temperature increase amount ΔTw increases with time, and reaches a predetermined reference value Tc at time t11. When the time from the start time (t0) of the engine 100 to the time when the temperature increase amount ΔTw reaches the reference value Tc is defined as “response time”, the response time when the hole 276 is not clogged is Δt1.

  A curve L2 represents an example of a temporal change in the temperature increase ΔTw when the hole 276 is completely blocked. Since the electromagnetic valve 270 is closed and the hole 276 is clogged, the cooling water hardly flows through the branch path 238. Therefore, the time t20 at which the water temperature Tw starts to rise is later than the time t10 when the hole 276 is not clogged at all. Thereafter, the temperature increase amount ΔTw reaches the reference value Tc at time t21. Therefore, the response time when the hole 276 is clogged is Δt2 (= t21−t0), which is longer than the response time Δt1 when the hole 276 is normal.

  In view of such a property, whether or not the hole 276 is clogged is determined using the response time defined by the curve Lc. The response time defined by the curve Lc is Δtc (= tc−t0). Hereinafter, this response time is referred to as “determination value”. When the response time is equal to or less than the determination value Δtc (see, for example, the curve L1), it is determined that the hole 276 is not clogged so as to affect the flow of the cooling water in the branch path 238. The response time increases as the degree of clogging of the holes 276 increases. When the response time is longer than the determination value Δtc (see, for example, the curve L2), it is determined that the hole 276 is clogged until the required amount of cooling water cannot be secured.

  When the above-described determination method is employed, there is a possibility that the water temperature sensor 240 deteriorates and an abnormality of the water temperature sensor 240 occurs. Specifically, in the water temperature sensor 240, there is a possibility that the response characteristic for detecting the temperature rise of the cooling water is deteriorated. A curve L3 represents an example of a time change of the temperature increase ΔTw when the hole 276 is normal (no clogging) but an abnormality (deterioration of response characteristics) occurs in the water temperature sensor 240.

  As shown by the curve L3, the response time Δt3 when the response characteristic of the water temperature sensor 240 deteriorates is longer than the determination value Δtc. As a result, there is a possibility that it is erroneously determined that the hole 276 is clogged even though the hole 276 is not actually clogged.

  In order to solve this problem, the present inventor has focused on the fact that when the electromagnetic valve 270 is in an open state, the flow rate of the cooling water flowing through the branch path 238 is almost equal regardless of whether the hole 276 is clogged. According to the present embodiment, a configuration is adopted in which the response characteristic of water temperature sensor 240 from the start of engine 100 is learned in the open state of electromagnetic valve 270, and determination value Δtc is corrected using the learning result. .

  FIG. 7 is a diagram for explaining the relationship between the flow rate of the cooling water and the response time. The horizontal axis in FIG. 7 indicates the flow rate per unit time of the cooling water flowing through the branch path 238. The vertical axis in FIG. 7 indicates the response time. A curve C1 represents a response time when the water temperature sensor 240 is normal. A curve C2 represents a response time when abnormality occurs in the water temperature sensor 240.

  Referring to FIG. 2, FIG. 4, FIG. 6, and FIG. 7, the response time increases as the flow rate of the cooling water decreases. First, the response time in the closed state of the electromagnetic valve 270 will be described. As shown by the curve C1, the response time when the water temperature sensor 240 is normal and the hole 276 is not clogged is Δt1 (see the curve L1 in FIG. 6). When the hole 276 is clogged while the water temperature sensor 240 is maintained normally, the response time becomes Δt2 (see the curve L2 in FIG. 6). The difference between these response times (Δt2−Δt1) is due to the clogging of the holes 276.

  On the other hand, as shown in the curve C2, when the hole 276 is not clogged but the water temperature sensor 240 is abnormal, the response time is Δt3 (see the curve L3 in FIG. 6). The difference in response time (Δt3−Δt1) when the hole 276 is not clogged is caused by the deterioration of the response characteristic of the water temperature sensor 240.

  Thus, a difference in response time can occur due to a plurality of factors. However, under the actual usage conditions of the cooling system 200, the occurrence point of abnormality is identified whether the difference in response time is due to clogging of the holes 276 or the deterioration of the response characteristics of the water temperature sensor 240. Difficult to do.

  On the other hand, when the electromagnetic valve 270 is opened, the flow rate of the cooling water flowing through the branch path 238 is substantially equal regardless of whether the hole 276 is clogged. Therefore, there is almost no difference in response time due to clogging of the holes 276. That is, when a difference in response time occurs in the open state of the electromagnetic valve 270, it can be said that the difference is mainly due to the deterioration of the response characteristic of the water temperature sensor 240.

  FIG. 8 is a time chart showing an example of a method for calculating a delay in response time due to deterioration of the response characteristic of the water temperature sensor 240 in the open state of the electromagnetic valve 270. Referring to FIG. 8, curve M1 represents an example of a temporal change in cooling water temperature increase ΔTw when both water temperature sensor 240 and hole 276 are normal. The curve M1 can be acquired in the initial state of the cooling system 200 (for example, the state immediately after the vehicle 1 is manufactured). When the electromagnetic valve 270 is opened, the response time of the normal water temperature sensor 240 is Δu1.

  A curve M represents an example of a temporal change in the temperature rise amount ΔTw of the cooling water when the response characteristic of the water temperature sensor 240 is deteriorated. The curve M is acquired, for example, in a state where the aging has progressed to some extent. The response time Δu of the deteriorated water temperature sensor 240 is longer than the response time Δu1 of the normal water temperature sensor 240 by A (= Δu−Δu1). The difference A in the response time indicates the degree of deterioration of the response characteristic of the water temperature sensor 240 with reference to the response time when the water temperature sensor 240 is normal. The ECU 300 corrects the determination value Δtc (see FIG. 6) by using the difference A as a “learning value”.

  FIG. 9 is a diagram for explaining a correction method for deterioration of the response characteristic of the water temperature sensor 240 in the closed state of the electromagnetic valve 270. With reference to FIG. 9, the curve Lc is a curve for determining whether or not the hole 276 is clogged as described in FIG. The determination value before correction defined by the curve Lc is Δtc.

  A curve Lc * is a curve indicating the corrected curve Lc. As an example, a curve obtained by translating the curve Lc by the learning value A in the positive direction of the response time can be a curve Lc *. At this time, the corrected determination value Δtc * is (Δtc + A). The correction method using the learning value is not limited to this. Other examples will be described later.

  FIG. 10 is a flowchart for describing control of cooling system 200 in the present embodiment. This flowchart is called from the main routine and executed when a predetermined condition is satisfied or every elapse of a predetermined period. Each step of the flowchart is basically realized by software processing by the ECU 300, but may be realized by hardware processing by an electronic circuit manufactured in the ECU 300.

  1 to 4 and 10, in step (hereinafter abbreviated as S) 10, ECU 300 determines whether or not electromagnetic valve 270 is in an open state. When electromagnetic valve 270 is in the open state (YES in S10), ECU 300 determines whether engine 100 is stopped (S20).

  When engine 100 is stopped (YES in S20), ECU 300 executes control (learning control) for learning the response characteristic of water temperature sensor 240 (S30). On the other hand, when engine 100 is already in the drive state (NO in S20), ECU 300 skips the process of S30 and returns the process to the main routine.

  When electromagnetic valve 270 is in the closed state in S10 (NO in S10), ECU 300 determines whether engine 100 is in the first state (S40). When engine 100 is in the first state (YES in S40), that is, when thermostat 260 is closed, ECU 300 determines whether or not hole 276 formed in electromagnetic valve 270 is clogged. (Decision control) is executed (S50). On the other hand, when engine 100 is not in the first state (NO in S40), that is, when thermostat 260 is opened, ECU 300 skips the process of S50 and returns the process to the main routine.

  FIG. 11 is a flowchart for explaining the learning control of the water temperature sensor 240 (see S30 in FIG. 10). 1 to 4 and 11, engine 100 is in the second state or the third state, and therefore electromagnetic valve 270 is opened.

  In S210, ECU 300 drives water pump 220. If the water pump 220 is already driven, the process of S210 can be omitted.

  In S220, ECU 300 starts engine 100 (see time t0 in FIG. 8).

  In step S230, the ECU 300 calculates a response time Δu from when the engine 100 is started until the temperature increase amount ΔTw detected by the water temperature sensor 240 reaches the reference value Tc. Note that the measurement start time of the response time is not limited to the start time of engine 100, and can be any time after the start of engine 100. The reference value Tc is the form of the hole 276 (for example, cross-sectional area or position), the response characteristic (specification value) of the water temperature sensor 240, the discharge amount of cooling water from the water pump 220 per unit time, the specific heat of cooling water, etc. It can be determined appropriately according to design or experiment.

  In S240, ECU 300 calculates a learned value of the response characteristic of water temperature sensor 240. More specifically, the response time Δu1 (see FIG. 8) of the normal water temperature sensor 240 is stored in the memory (not shown) of the ECU 300. ECU 300 calculates difference (Δu−Δu1) between response time Δu calculated in S230 and response time Δu1 of normal water temperature sensor 240 as learning value A.

  In S250, ECU 300 corrects determination value Δtc using learned value A. As an example, as described with reference to FIG. 9, a value obtained by adding the learning value A to the determination value Δtc before correction can be used as the correction value Δtc * after correction (see the following formula (1)).

Δtc * = Δtc + A (1)
Alternatively, as another example, as shown in the following formula (2), a coefficient α (0 <0) between a determination value Δtc before correction and a value (Δtc + A) obtained by adding the learning value A to the determination value Δtc before correction. The corrected determination value Δtc * may be calculated by performing weighting using α <1).

Δtc * = (1−α) × Δtc + α × (Δtc + A) = Δtc + αA (2)
Since the learning value A is calculated based on the detection result of one response time, it may include a relatively large error. When the learning value A is calculated to be excessively large due to the detection error, in the above equation (1), the determination value Δtc * can be rapidly changed by one correction. As a result, it may be erroneously determined whether or not the hole 276 is clogged. If α is appropriately set in Expression (2), a rapid change in the determination value is suppressed, so that the possibility of erroneous determination can be reduced. When the processing of S250 ends, ECU 300 returns the processing to the flowchart shown in FIG.

  FIG. 12 is a flowchart for explaining determination control (see S50 in FIG. 10). 1 to 4 and 12, since engine 100 is in the first state, thermostat 260 and electromagnetic valve 270 are both closed.

  In S310, ECU 300 starts engine 100. In S320, ECU 300 drives water pump 220. When engine 100 and water pump 220 are already driven at the start of determination control, the driving state of engine 100 and water pump 220 can be maintained.

  When the water pump 220 is driven, the temperature distribution of the cooling water in the cooling water path may be uneven. Therefore, after driving water pump 220, ECU 300 stands by until a predetermined time has elapsed so as to reduce the temperature unevenness of the cooling water (NO in S330). However, the predetermined time is determined so that the water temperature Tw does not reach the temperature at which the thermostat 260 is opened.

  When the predetermined time has elapsed (YES in S330), ECU 300 detects water temperature Tw using water temperature sensor 240 to calculate response time Δt (S340).

  In S350, ECU 300 determines the magnitude relationship between response time Δt calculated in S340 and corrected determination value Δtc * (see S250 in FIG. 11) calculated in learning control.

  When response time Δt is longer than corrected determination value Δtc * (YES in S350), ECU 300 determines that hole 276 of electromagnetic valve 270 is clogged (S360). In this case, for example, when the engine 100 in the first state is warmed up, the flow of the cooling water can be ensured by making the opening degree of the electromagnetic valve 270 larger than when the hole 276 is not clogged. .

  On the other hand, when response time Δt is equal to or less than corrected determination value Δtc * (NO in S350), ECU 300 determines that hole 276 of electromagnetic valve 270 is not clogged (S370). When the process of S360 or S370 ends, ECU 300 returns the process to the flowchart shown in FIG.

  As described above, according to the present embodiment, the response characteristic of the water temperature sensor 240 is learned in the open state of the electromagnetic valve 270. Then, using the learning result, the determination value Δtc for determining whether or not the hole 276 is clogged is corrected. Thereby, the influence of the deterioration of the response characteristic of the water temperature sensor 240 can be excluded. Accordingly, it is possible to prevent erroneous determination that the hole 276 is clogged.

[Modification]
In the above-described embodiment, learning and correction of the determination value are performed using a response period required for obtaining a predetermined temperature increase amount. In the modification of the present embodiment, a configuration in which learning and correction are performed using a temperature rise amount within a predetermined period will be described.

  FIG. 13 is a time chart showing an example of a method for calculating a delay in response time caused by deterioration of the response characteristics of the water temperature sensor 240 according to a modification of the present embodiment. Referring to FIG. 13, a curve M1 represents an example of a temporal change in the cooling water temperature increase ΔTw when both the water temperature sensor 240 and the hole 276 are normal. When the electromagnetic valve 270 is opened, the normal water temperature sensor 240 increases the water temperature Tw by ΔT1 before the predetermined period Kc1 elapses from when the engine 100 is started.

  A curve M represents an example of a temporal change in the temperature rise amount ΔTw of the cooling water when the response characteristic of the water temperature sensor 240 is deteriorated. When the deteriorated water temperature sensor 240 is used, the temperature increase amount ΔT within the predetermined period Kc1 is smaller than the temperature increase amount ΔT1 of the normal water temperature sensor 240 by B (= ΔT1−ΔT). In the modification, ECU 300 corrects the determination value by using difference B of temperature increase ΔTw as a “learning value” with reference to temperature increase ΔT1 when water temperature sensor 240 is normal.

  FIG. 14 is a diagram for explaining a method for correcting deterioration of the response characteristic of the water temperature sensor 240 according to a modification of the present embodiment. Referring to FIG. 14, the determination value before correction defined by curve Lc for determining whether or not hole 276 is clogged is ΔTc. In other words, ECU 300 determines that hole 276 is clogged when the temperature increase amount ΔTw of the cooling water within predetermined period Kc2 is equal to or smaller than determination value ΔTc in the closed state of electromagnetic valve 270. On the other hand, when the temperature increase amount ΔTw is larger than the determination value ΔTc, it is determined that the hole 276 is not clogged.

  A curve Lc ** is a curve indicating the corrected curve Lc. As an example, a curve obtained by translating the curve Lc by the learning value B in the negative direction of the temperature increase amount ΔTw can be used as the curve Lc **. At this time, the corrected determination value ΔTc ** is (ΔTc−B). Note that the corrected determination value ΔTc ** may be calculated using the coefficient β (0 <β <1) as in the above-described equation (2) (see the following equation (3)).

ΔTc ** = (1−β) × ΔTc + β × (ΔTc−B) = ΔTc + βB (3)
In the flowchart for explaining the control of the cooling system 200 in the modification of the present embodiment, the “response time” in the process related to “response time” (S230 in FIG. 11 and S340, 350 in FIG. 12) is “ Changing to “temperature rise amount” is equivalent to the flowcharts shown in FIGS. 10 to 12, and thus detailed description will not be repeated.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Vehicle, 10 1st motor generator (1st MG), 20 2nd motor generator (2nd MG), 30 Power split mechanism, 40 Reducer, 50 Power control unit (PCU), 60 Battery, 100 Engine, 102 Engine rotational speed Sensor 110 Engine body 112 Cylinder block 114 Cylinder head 200 Cooling system 210 Water jacket 220 Water pump 232 (232A, 232B) Supply path 234 (234A, 234B) Return path 236 (236A, 236B) Bypass path, 238 (238A, 238B) Branch path, 240 Water temperature sensor, 250 Radiator, 260 Thermostat, 270 Electromagnetic valve, 272 Electric actuator, 274 Valve body, 276 hole 278 path, 300 ECU, 350 drive wheels.

Claims (7)

A cooling system for an internal combustion engine,
A first path for circulating cooling water so as to pass through the internal combustion engine;
A second path for circulating cooling water so as to bypass the internal combustion engine;
The first path to the cooling water which is provided between the downstream side of the internal combustion engine of the first path and the second path and which circulates through the second path as the opening degree is increased. A valve configured to increase the amount of cooling water flowing through the
Even if the opening degree is less than the first predetermined value, a circulation part for circulating a small amount of cooling water through the first path;
A water temperature sensor that is provided between the internal combustion engine and the valve in the first path and detects the temperature of cooling water flowing through the first path;
A control device for controlling the opening;
The controller is
When the opening degree is lower than the first predetermined value, the flow section is clogged based on the relationship between the time change of the temperature of the cooling water detected by the water temperature sensor and the predetermined determination value. Whether or not
When the opening degree is in a state exceeding a second predetermined value larger than the first predetermined value, the response characteristic of the water temperature sensor from the start of the internal combustion engine is learned,
A cooling system for an internal combustion engine that corrects the determination value using a result of the learning.   The control device is a time required for the temperature of the cooling water detected by the water temperature sensor to increase by a predetermined temperature from the start of the internal combustion engine in a state where the opening is less than the first predetermined value. If the response time exceeds the determination value, it is determined that the circulation section is clogged, while if the response time is less than the determination value, it is determined that the distribution section is not blocked. The cooling system for an internal combustion engine according to claim 1.   The cooling system for an internal combustion engine according to claim 2, wherein the control device learns the response characteristic with reference to the response time when the water temperature sensor is normal.   In the state where the opening degree is less than the first predetermined value, the control device, when the temperature increase amount within a predetermined period of the cooling water detected by the water temperature sensor is lower than the determination value, 2. The cooling system for an internal combustion engine according to claim 1, wherein, when it is determined that clogging has occurred, and when the temperature increase amount exceeds the determination value, it is determined that clogging of the circulation portion has not occurred.   The cooling system for an internal combustion engine according to claim 4, wherein the control device learns the response characteristic based on the temperature increase amount when the water temperature sensor is normal.   The cooling system for an internal combustion engine according to any one of claims 1 to 5, wherein the flow part is a hole formed in a valve body of the valve or a path formed so as to bypass the valve. A control method for a cooling system of an internal combustion engine, comprising:
The cooling system includes:
A first path for circulating cooling water so as to pass through the internal combustion engine;
A second path for circulating cooling water so as to bypass the internal combustion engine;
The first path to the cooling water which is provided between the downstream side of the internal combustion engine of the first path and the second path and which circulates through the second path as the opening degree is increased. A valve configured to increase the amount of cooling water flowing through the
Even if the opening degree is less than the first predetermined value, a circulation part for circulating a small amount of cooling water through the first path;
A water temperature sensor that is provided between the internal combustion engine and the valve in the first path and detects the temperature of cooling water flowing through the first path;
The control method is:
When the opening degree is lower than the first predetermined value, the flow section is clogged based on the relationship between the time change of the temperature of the cooling water detected by the water temperature sensor and the predetermined determination value. Determining whether or not
Learning the response characteristic of the water temperature sensor from the start of the internal combustion engine when the opening is in a state exceeding a second predetermined value larger than the first predetermined value;
A method for controlling the cooling system of the internal combustion engine, comprising: correcting the determination value using a result of the learning.

Images