Thermostat failure detection device

Abstract

To provide a failure determination device for a thermostat capable of appropriately determining of failure of the thermostat for switching a circulation passage of cooling water without requiring evaluation and preparation of a water temperature evaluation model with respect to each vehicle in accordance with a vehicle model and specifications, etc. and with reduced man-hours.SOLUTION: A circulation passage of cooling water comprises a radiator passage and a bypass passage, and a thermostat switches the bypass passage and the radiator passage in accordance with a temperature of the cooling water. A failure determination device learns and stores a water temperature evaluation model related amount related to a water temperature evaluation model that is a temperature rise state for failure determination with respect to each vehicle on the basis of an actual temperature rise state of the cooling water in a normality determination period that is a predetermined period from product shipment of the vehicle and in which the thermostat is determined to be normal, and determines failure of the thermostat on the basis of the actual temperature rise state of the cooling water and the water temperature evaluation model with respect to each vehicle based on the stored water temperature evaluation model related amount after passage of the normality determination period.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a thermostat failure determination device that determines a failure of a thermostat that switches a circulation path of coolant that cools an internal combustion engine mounted on a vehicle. [Background technology]

[0002] Conventionally, the circulation path of the coolant that cools the internal combustion engine mounted on a vehicle has been set to include a radiator path in which the coolant discharged from the internal combustion engine is cooled in a radiator and returned to the internal combustion engine, and a bypass path in which the coolant discharged from the internal combustion engine is returned to the internal combustion engine without passing through the radiator. The circulation path is provided with a thermostat, and the thermostat switches the circulation path depending on the temperature of the coolant.

[0003] When the coolant temperature is below the warm-up completion temperature (for example, 70°C), the thermostat sets the circulation path to a bypass path (bypassing the radiator) to quickly raise the coolant temperature to the warm-up completion temperature. When the coolant temperature reaches or exceeds the warm-up completion temperature, the thermostat sets the circulation path to the radiator path to properly cool the internal combustion engine to prevent overheating.

[0004] If the thermostat malfunctions and the circulation path is set to the radiator path even though the coolant temperature is below the warm-up completion temperature, the warm-up time may become longer than necessary, which may delay the activation of the catalyst in the exhaust purification device, resulting in exhaust gas being discharged outside the vehicle without being sufficiently purified. Therefore, it is necessary to properly determine whether the thermostat has malfunctioned.

[0005] For example, Patent Document 1 discloses a thermostat failure determination device that can detect whether or not a thermostat has failed by monitoring the engine's warm-up performance during a cold start. This thermostat failure determination device uses a water temperature sensor to detect the temperature of the coolant that has passed through the engine and monitors the rise in the coolant temperature during a cold start, calculates a predicted engine water temperature from the start of startup, and determines that the thermostat has failed if the coolant temperature does not exceed a threshold when the predicted water temperature reaches the thermostat valve opening temperature. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-127324 Summary of the Invention [Problem to be solved by the invention]

[0007] The thermostat failure determination device described in Patent Document 1 determines whether the actual vehicle water temperature exceeds the water temperature threshold when the "predicted water temperature" reaches the thermostat valve opening temperature, so the "predicted water temperature" for that vehicle must be stored in advance in the failure determination device. Since the amount of heat generated by the engine and the amount of water in the coolant circulation path vary depending on the vehicle, the "predicted water temperature" also varies depending on the vehicle. Note that vehicles come in various models and specifications (e.g., for general use, for cold climates, etc.), and even for the same vehicle model, different specifications may result in different amounts of water in the circulation path. In other words, a "predicted water temperature" for each vehicle model and specification must be created in advance, based on the actual vehicle model and specifications.

[0008] For example, Figure 3 shows the temperature rise of the coolant after starting the internal combustion engine in a certain vehicle (e.g., vehicle model A, specification x) when the thermostat is normal (when the thermostat is normal) and the temperature rise of the coolant after starting the internal combustion engine when the thermostat is faulty (when the thermostat is faulty). For this vehicle, a "water temperature evaluation model" (predicted water temperature) that is intermediate between the temperature rise "when the thermostat is normal" and the temperature rise "when the thermostat is faulty" is created in advance, and whether the thermostat is faulty can be determined based on whether the actual temperature rise of the vehicle is higher than the "water temperature evaluation model." However, as mentioned above, the "when the thermostat is normal," "when the thermostat is faulty," and "water temperature evaluation model" differ depending on the vehicle model and specification, so it is necessary to create a "water temperature evaluation model" tailored to the vehicle, which requires a huge amount of work.

[0009] The present invention was devised in light of these points, and its objective is to provide a thermostat failure determination device that can properly determine failure of a thermostat that switches the cooling water circulation path with fewer steps, without the need to create a water temperature evaluation model for each vehicle depending on the vehicle model, specifications, etc. [Means for solving the problem]

[0010] In order to solve the above problems, a first aspect of the present invention is a thermostat failure determination device that determines a failure of a thermostat provided in a coolant circulation path of an internal combustion engine mounted on a vehicle. The circulation path includes a radiator path that cools the coolant discharged from the internal combustion engine in a radiator and returns it to the internal combustion engine, and a bypass path that returns the coolant discharged from the internal combustion engine to the internal combustion engine without passing through the radiator. The thermostat switches the circulation path so that it sets the circulation path to the bypass path when the coolant temperature is below a warm-up completion temperature, and sets the circulation path to the radiator path when the coolant temperature is equal to or higher than the warm-up completion temperature. The failure determination device has a water temperature evaluation model related quantity storage unit that assumes that the thermostat is normal during a predetermined period from the vehicle's product shipment state during which the thermostat can be assumed to be normal, and learns and stores in a non-volatile storage device, for each vehicle, water temperature evaluation model related quantities related to a water temperature evaluation model, which is the temperature rise state for determining whether the thermostat has failed, based on the actual temperature rise state of the coolant after the internal combustion engine is started, and a thermostat failure determination unit that, after the normal period has elapsed, determines whether the thermostat has failed based on the actual temperature rise state of the coolant after the internal combustion engine is started and the water temperature evaluation model for each vehicle which is based on the stored water temperature evaluation model related quantities.

[0011] A second aspect of the present invention is the thermostat failure determination device according to the first aspect of the present invention, wherein the water temperature evaluation model is capable of distinguishing between a normal temperature rise state, which is the state of the coolant temperature rise when the internal combustion engine is started from a state in which the coolant temperature is below the warm-up completion temperature, the thermostat is normal, and the circulation path is set to the bypass path, and a faulty temperature rise state, which is the state of the coolant temperature rise when the internal combustion engine is started from a state in which the coolant temperature is below the warm-up completion temperature, the thermostat is faulty, and the circulation path is set to the radiator path, and the temperature rise state is a state of the coolant temperature rise at a gentler slope than the normal temperature rise state, and the temperature rise state is between the normal temperature rise state and the faulty temperature rise state. The failure determination device also stores a reference water temperature evaluation model that serves as a reference for the state of the coolant temperature rise after the internal combustion engine is started. The failure determination device is a thermostat failure determination device in which the water temperature evaluation model related quantity memory unit learns the water temperature evaluation model related quantities for bringing the reference water temperature evaluation model closer to the water temperature evaluation model appropriate for the vehicle in which the device is installed, based on the actual temperature rise state of the coolant after the internal combustion engine is started, and stores the learned quantities in the non-volatile storage device, and the thermostat failure determination unit creates the water temperature evaluation model appropriate for the vehicle in which the device is installed, based on the reference water temperature evaluation model and the water temperature evaluation model related quantities, and determines whether the thermostat has failed.

[0012] Next, a third aspect of the present invention is a thermostat failure determination device according to the second aspect of the invention, wherein the water temperature evaluation model related quantity storage unit calculates a bypass path water volume, which is the amount of coolant circulating in the bypass path, based on the temperature of the coolant at the start of measurement when the internal combustion engine is started with the coolant temperature below the warm-up completion temperature and the temperature of the coolant at the end of measurement after a predetermined time has elapsed since the start of measurement, and an input heat quantity, which is the heat quantity based on the integrated amount of fuel injected into the internal combustion engine during the period from the start of measurement to the end of measurement, and learns the water temperature evaluation model related quantities based on the calculated bypass path water volume.

[0013] Next, a fourth aspect of the present invention is a thermostat failure determination device according to the second or third aspect of the present invention, wherein the vehicle may be provided with a passenger heater that discharges warm air to passengers in the vehicle cabin, and when the passenger heater is provided, a heater path that routes the cooling water to the passenger heater is added to the radiator path and the bypass path, and a heater usage state that can detect whether the passenger heater is being used or not is input to the failure determination device. When the failure determination device determines, based on the heater usage status, that the vehicle in which it is installed has a passenger heater, it separately learns and stores, in the water temperature evaluation model related quantity memory unit, the water temperature evaluation model related quantities for when the passenger heater is in use and the water temperature evaluation model related quantities for when the passenger heater is not in use, and, in the thermostat failure determination unit, creates the water temperature evaluation model for each vehicle based on the water temperature evaluation model related quantities for when the passenger heater is in use when the passenger heater is in use, and creates the water temperature evaluation model for each vehicle based on the water temperature evaluation model related quantities for when the passenger heater is not in use when the passenger heater is not in use.This is a thermostat failure determination device. [Effects of the Invention]

[0014] According to the first aspect of the present invention, during a predetermined period from the vehicle's shipping state during which the thermostat can be considered normal, water temperature evaluation model related quantities for creating a water temperature evaluation model tailored to the vehicle are learned and stored in a non-volatile storage device. After the normal period has elapsed, a water temperature evaluation model tailored to the vehicle is created based on the learned water temperature evaluation model related quantities and used to determine thermostat malfunction. This eliminates the need to create a water temperature evaluation model for each vehicle based on its make and specifications, enabling appropriate thermostat malfunction determination with fewer steps.

[0015] According to the second aspect of the present invention, since the reference water temperature evaluation model is stored, there is no need to learn and store the entire water temperature evaluation model for the vehicle. For example, by simply storing the water temperature evaluation model related quantities as correction coefficients for the vehicle, it is possible to conveniently create a water temperature evaluation model for the vehicle.

[0016] As described above, the amount of water in the bypass route varies depending on the vehicle model and specifications, so in the past it was necessary to create a water temperature evaluation model for each vehicle. According to the third invention, by estimating the amount of water in the bypass route for the vehicle, it is possible to identify the vehicle model and specifications, and more appropriately learn the water temperature evaluation model related quantities.

[0017] For example, some vehicles are configured to have a passenger heater that uses the coolant temperature depending on the specifications. In such vehicles, even if the thermostat is normal, the state of coolant temperature rise differs depending on whether the passenger heater is in use or not. According to the fourth invention, by creating separate water temperature evaluation models for when the passenger heater is in use and when the passenger heater is not in use, it is possible to appropriately determine whether the thermostat is faulty. [Brief explanation of the drawings]

[0018] [Figure 1]1 is a diagram illustrating an outline of a circulation path (bypass path) of cooling water for an internal combustion engine and a failure determination device in a first embodiment. FIG. [Figure 2] 1 is a diagram illustrating an outline of a circulation path (radiator path) of coolant in an internal combustion engine and a failure determination device in a first embodiment. [Figure 3] 10A and 10B are diagrams illustrating examples of a cooling water temperature rise state when a thermostat is normal, a temperature rise state when a thermostat is faulty, and a water temperature evaluation model. [Figure 4] 4 is a flowchart illustrating an example of a processing procedure of “overall processing for determining a failure of a thermostat” performed by the failure determination device according to the first embodiment. [Figure 5] 6 is a flowchart illustrating an example of a process performed by the failure determination device to calculate an integrated injection amount. [Figure 6] 5 is a flowchart illustrating details of "Learning water temperature evaluation model related quantities" in the flowchart of FIG. 4. [Figure 7] 5 is a flowchart illustrating details of the "calculation of a water temperature evaluation model and thermostat failure determination" in the flowchart of FIG. 4. [Figure 8] FIG. 4 is a diagram illustrating an example of [water temperature evaluation model information] in the first embodiment. [Figure 9] This figure explains examples of a reference water temperature evaluation model, a water temperature evaluation model created using water temperature evaluation model related quantities for (vehicle type A, specification x), and a water temperature evaluation model created using water temperature evaluation model related quantities for (vehicle type A, specification y). [Figure 10] 4A to 4C are diagrams illustrating an example of the operation of the failure determination device when learning a water temperature evaluation model related quantity in the first embodiment. [Figure 11] FIG. 10 is a diagram illustrating an outline of a circulation path (bypass path) of cooling water for an internal combustion engine and a failure determination device in a second embodiment. [Figure 12] FIG. 10 is a diagram illustrating an outline of a circulation path (radiator path) of coolant for an internal combustion engine and a failure determination device in a second embodiment. [Figure 13]This figure explains examples of the cooling water temperature rise state when the thermostat is normal, the temperature rise state when the thermostat is faulty, and a water temperature evaluation model for when the passenger heater is ON and OFF, respectively. [Figure 14] 10 is a flowchart illustrating an example of a processing procedure of an "overall process of determining a failure of a thermostat" performed by the failure determination device according to the second embodiment. [Figure 15] 15 is a flowchart illustrating details of "Learning water temperature evaluation model related quantities" in the flowchart of FIG. 14. [Figure 16] This is a continuation of the flowchart in Figure 15. [Figure 17] 15 is a flowchart illustrating details of the "calculation of a water temperature evaluation model and thermostat failure determination" in the flowchart of FIG. [Figure 18] FIG. 10 is a diagram illustrating an example of [water temperature evaluation model information] in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings, with first and second embodiments being described in order.

[0020] [First embodiment (Figs. 1 to 10)] ●[Cooling water circulation path and fault detection device configuration (Fig. 1, Fig. 2)] 1 and 2 show an example of the overall configuration of an internal combustion engine system 1 having a thermostat failure determination device 50 according to a first embodiment. The internal combustion engine system 1 has an internal combustion engine 10, a radiator 20, a thermostat 40, the failure determination device 50, etc. Note that in the internal combustion engine system 1 shown in FIGS. 1 and 2, components other than the cooling water circulation path are omitted.

[0021] The internal combustion engine 10 is, for example, a diesel engine mounted on a vehicle. Coolant flows into the internal combustion engine 10, and the cooled coolant is discharged. One end (inflow side) of an internal combustion engine discharge pipe 61 is connected to a coolant outlet of the internal combustion engine 10. The other end (outflow side) of an internal combustion engine inlet pipe 65 is connected to a coolant inlet of the internal combustion engine 10. A coolant temperature detection device 31 that detects the temperature of the coolant after cooling the internal combustion engine 10 is provided near the coolant outlet of the internal combustion engine 10. The coolant temperature detection device 31 is, for example, a temperature sensor, and outputs a detection signal corresponding to the coolant temperature to the failure determination device 50. The internal combustion engine 10 is also provided with a crank rotation detection device 32 that detects the rotation state of the crankshaft. The crank rotation detection device 32 is, for example, a rotation sensor, and outputs a detection signal corresponding to the rotation angle of the crankshaft to the failure determination device 50. The internal combustion engine 10 is also provided with a water pump 34 that circulates the coolant.

[0022] The cooling water circulation path of the internal combustion engine 10 is made up of an internal combustion engine discharge pipe 61, a bypass pipe 62, a radiator inlet pipe 63, the radiator 20, a radiator discharge pipe 64, a thermostat 40, an internal combustion engine inlet pipe 65, etc. In the following description of each pipe, "one end" refers to the inlet side of the pipe where the cooling water flows in, and "the other end" refers to the outlet side of the pipe where the cooling water flows out.

[0023] One end of the internal combustion engine discharge pipe 61 is connected to a coolant discharge port of the internal combustion engine 10. The other end of the internal combustion engine discharge pipe 61 is connected to one end of a bypass pipe 62 and one end of a radiator inlet pipe 63. One end of the bypass pipe 62 is connected to the other end of the internal combustion engine discharge pipe 61 and one end of the radiator inlet pipe 63. The other end of the bypass pipe 62 is connected to a bypass inlet of the thermostat 40.

[0024] One end of the radiator inlet pipe 63 is connected to the other end of the internal combustion engine discharge pipe 61 and one end of the bypass pipe 62. The other end of the radiator inlet pipe 63 is connected to a coolant inlet of the radiator 20. One end of the radiator discharge pipe 64 is connected to a coolant outlet of the radiator 20. The other end of the radiator discharge pipe 64 is connected to a radiator inlet of the thermostat 40.

[0025] One end of the internal combustion engine inlet pipe 65 is connected to a coolant outlet of the thermostat 40. The other end of the internal combustion engine inlet pipe 65 is connected to a coolant inlet of the internal combustion engine .

[0026] Thermostat 40 has a valve element 41 that moves in accordance with the coolant temperature. When the coolant temperature is below the warm-up completion temperature (for example, below 70°C), thermostat 40 moves valve element 41 to close the connection with radiator discharge pipe 64 and open the connection with bypass pipe 62, as shown in Fig. 1, thereby setting the coolant circulation path to the "bypass path." When the coolant temperature is equal to or higher than the warm-up completion temperature (for example, equal to or higher than 70°C), thermostat 40 moves valve element 41 to open the connection with radiator discharge pipe 64 and close the connection with bypass pipe 62, as shown in Fig. 2, thereby setting the coolant circulation path to the "radiator path."

[0027] In the "bypass path" shown in Fig. 1, the valve body 41 of the thermostat 40 closes the connection with the radiator discharge pipe 64 and opens the connection with the bypass pipe 62. Therefore, as shown by the dotted arrow in Fig. 1, the coolant discharged from the internal combustion engine 10 flows from the internal combustion engine discharge pipe 61 to the bypass pipe 62, flows into the thermostat 40, and returns to the internal combustion engine 10 through the internal combustion engine inlet pipe 65. In the "bypass path," the coolant does not pass through the radiator 20 but bypasses the radiator 20, so the temperature of the coolant rises in a relatively short time.

[0028] In the "radiator path" shown in Figure 2, the valve body 41 of the thermostat 40 opens the connection with the radiator discharge pipe 64 and closes the connection with the bypass pipe 62. Therefore, the coolant discharged from the internal combustion engine 10 flows from the internal combustion engine discharge pipe 61 to the radiator inlet pipe 63 and then into the radiator 20, as shown by the dotted arrow in Figure 2. The coolant discharged from the radiator 20 then flows into the thermostat 40 from the radiator discharge pipe 64 and returns to the internal combustion engine 10 from the internal combustion engine inlet pipe 65. In the "radiator path," by passing through the radiator 20, the amount of temperature rise of the coolant discharged from the internal combustion engine 10 can be suppressed.

[0029] The radiator 20 dissipates heat from the coolant flowing in through a radiator inlet pipe 63 to lower the temperature, and discharges the coolant from a radiator outlet pipe 64.

[0030] The failure determination device 50 is a so-called control device that has a CPU 51, a RAM 52, a ROM 53 (e.g., Flash-ROM), a timer 54, a non-volatile storage device 55, etc. The failure determination device 50 receives detection signals from the coolant temperature detection device 31, detection signals from the crank rotation detection device 32, and a signal from the ignition switch 33. A water temperature evaluation model related quantity storage unit 51A and a thermostat failure determination unit 51B will be described later. The failure determination device 50 receives input of various signals that detect the operating state of the internal combustion engine 10 and outputs signals that control various actuators that control the internal combustion engine 10, but a description of these will be omitted.

[0031] ●[Example of temperature rise during normal / failure thermostat operation and water temperature evaluation model (Fig. 3)] FIG. 3 shows an example of the temperature rise of the coolant when the internal combustion engine 10 is started (cold started) at time Z1 (measurement start time Z1) from a state in which the coolant temperature is sufficiently lower than the warm-up completion temperature.

[0032] When the thermostat 40 is operating normally, as shown by the solid line "When the thermostat is normal," from time Z1 (measurement start time Z1) when the coolant temperature is below the warm-up completion temperature to time ZT (time when the warm-up completion temperature is reached), the circulation path is set to the bypass path (see Figure 1), so the coolant temperature rises in a relatively short time; after time ZT when the coolant temperature reaches or exceeds the warm-up completion temperature, the circulation path is switched to the radiator path (see Figure 2), so the rise in the coolant temperature becomes gradual and the temperature becomes stable.

[0033] When the thermostat 40 fails (when the thermostat is fixed in the radiator path), as shown by the dotted line "When the thermostat is failed," the circulation path is fixed to the radiator path (see Figure 2) regardless of the coolant temperature, and the coolant temperature rises more slowly than when the thermostat is normal.

[0034] The failure determination device 50 is set with a water temperature evaluation model (dashed line in FIG. 3) that represents a temperature rise state between the normal temperature rise state (solid line in FIG. 3), which is the temperature rise state when the thermostat is normal, and the failed temperature rise state (dotted line in FIG. 3), which is the temperature rise state when the thermostat is failed, as shown in FIG. 3. The water temperature evaluation model is a temperature rise state that can distinguish between the normal temperature rise state and the failed temperature rise state. The failure determination device 50 determines whether the thermostat 40 is failed using the actual coolant temperature rise state after the internal combustion engine 10 has started and the water temperature evaluation model.

[0035] In addition, the amount of temperature rise relative to time (amount of heat input) in the normal temperature rise state and the faulty temperature rise state differs depending on the vehicle, such as the amount of water in the bypass route, the amount of water in the radiator route, and the heat dissipation capacity of the radiator 20. For this reason, in the past, a water temperature evaluation model for each vehicle was created through experiments and simulations using an actual vehicle, requiring a significant amount of work. Moreover, even for vehicles of the same model, the piping route and water amount differ depending on the specifications (general specifications, cold climate specifications, etc.), so a water temperature evaluation model must be created for each vehicle, requiring a significant amount of work. In the present application, as will be explained below, this effort for each vehicle is reduced.

[0036] [Processing procedure for determining a thermostat failure by the failure determination device 50 (FIGS. 4 to 10)] 4 to 10, an example of the processing procedure for "determining a thermostat failure" by the failure determination device 50 will be described. The failure determination device 50 starts the processing shown in Fig. 4 at predetermined time intervals (for example, intervals of several tens to several hundreds of milliseconds), and proceeds to step S030.

[0037] In step S030, the failure determination device 50 determines whether the internal combustion engine 10 is starting up. If the rotation speed of the internal combustion engine 10 is less than a predetermined rotation speed, the failure determination device 50 determines that the internal combustion engine 10 is starting up. If it is determined that the internal combustion engine 10 is starting up (Yes), the process proceeds to step S090. If it is determined that the internal combustion engine 10 is not starting up (determined that the internal combustion engine 10 is after starting) (No), the process proceeds to step S035.

[0038] If the processing proceeds to step S090, the failure determination device 50 substitutes the coolant temperature (the coolant temperature detected using the coolant temperature detection device) for the water temperature at startup, sets the current learning execution flag to OFF, sets the current learning end flag to OFF, sets the current failure determination end flag to OFF, sets the injection cumulative amount to 0 (zero), stops and initializes the warm-up timer, and ends the processing shown in FIG. 4.

[0039] The water temperature at startup is the coolant temperature at startup used in step S125 of Fig. 6 and the like. The current learning in progress flag is a flag that is set ON while "learning water temperature evaluation model related quantities" in step S080 of Fig. 4 is being executed for the current startup of the internal combustion engine. The current learning completion flag is a flag that is set ON when "learning water temperature evaluation model related quantities" in step S080 of Fig. 4 has been executed for the current startup of the internal combustion engine. The current failure determination completion flag is a flag that is set ON when "calculating water temperature evaluation model and determining thermostat failure" in step S085 of Fig. 4 has been executed for the current startup of the internal combustion engine.

[0040] If the process proceeds to step S035, the failure determination device 50 acquires the cumulative mileage of the vehicle equipped with the internal combustion engine 10, and proceeds to step S040. For example, the failure determination device 50 is connected to a communication line with various other control devices equipped in the vehicle, and is capable of transmitting and receiving information to and from the various control devices via the communication line, and receives and acquires the cumulative mileage.

[0041] In step S040, the malfunction determination device 50 determines whether the accumulated mileage is equal to or less than the deemed-normal distance. If the accumulated mileage is equal to or less than the deemed-normal distance (Yes), the malfunction determination device 50 proceeds to step S080. If the accumulated mileage is greater than the deemed-normal distance (No), the malfunction determination device 50 proceeds to step S045. The accumulated mileage is the accumulated value of the mileage of the vehicle since its factory shipment, and the deemed-normal distance is a preset distance, for example, several hundred kilometers to 1,000 kilometers. If the accumulated mileage is equal to or less than the deemed-normal distance, it is determined that the period since the vehicle's factory shipment is short and that the thermostat is within the deemed-normal period during which it can be considered normal. During this deemed-normal period, the malfunction determination device 50 considers the thermostat to be normal, and in step S080, learns the water temperature evaluation model related quantities for each vehicle.

[0042] If the process proceeds to step S045, the failure determination device 50 determines whether the learning completion flag is OFF. If the learning completion flag is OFF (Yes), the failure determination device 50 proceeds to step S080, and if the learning completion flag is not OFF (No), the failure determination device 50 proceeds to step S085. The learning completion flag is a flag stored in a non-volatile storage device, and is set to ON when "Learning the water temperature evaluation model related quantities" in step S080 of FIG. 4 has been executed (completed). Even if the cumulative mileage is longer than the deemed-normal distance (even after the deemed-normal period has elapsed), if "Learning the water temperature evaluation model related quantities" has not been executed (completed), the failure determination device 50 executes "Learning the water temperature evaluation model related quantities."

[0043] When the process proceeds to step S080, the failure determination device 50 executes the process of "learning the related quantities of the water temperature evaluation model" and ends the process shown in Fig. 4. The details of "learning the related quantities of the water temperature evaluation model" will be described later.

[0044] If the process proceeds to step S085, the failure determination device 50 executes the process of "calculating a water temperature evaluation model and determining a thermostat failure" and ends the process shown in Fig. 4. The details of "calculating a water temperature evaluation model and determining a thermostat failure" will be described later.

[0045] ●[Calculating the cumulative injection amount (Fig. 5)] Next, the process of calculating the "cumulative injection amount" used in step S150 etc. of Fig. 6 will be described with reference to Fig. 5. The cumulative injection amount is the cumulative value of the amount of fuel injected from the injector provided in the internal combustion engine 10. In the process shown in Fig. 5, the process of step SZ020 is added after step SZ010 of the existing fuel injection process.

[0046] In step SZ020, the failure determination device 50 adds the current fuel injection amount to the cumulative injection amount to update the cumulative injection amount, and then ends the processing shown in FIG.

[0047] ●[Learning quantities related to the water temperature evaluation model (Figure 6)] Next, details of the process of "learning water temperature evaluation model related quantities" in step S080 in the flowchart of Fig. 4 will be described with reference to Fig. 6. When executing the process of step S080 in Fig. 4, the failure determination device 50 proceeds to the process of step S110 in Fig. 6.

[0048] In step S110, the failure determination device 50 determines whether the current learning end flag is ON. The current learning end flag is a flag that is set to ON in step S170 of FIG. 6 when learning of the water temperature evaluation model related quantities has already been completed since the current start of the internal combustion engine. If the current learning end flag is ON (Yes), the failure determination device 50 ends the processing shown in FIG. 6, returns the processing to below step S080 of FIG. 4, and ends the processing shown in FIG. If the current learning end flag is not ON (No), the failure determination device 50 proceeds to step S115.

[0049] If the process proceeds to step S115, the failure determination device 50 determines whether a current learning execution flag is ON. The current learning execution flag is a flag that is set to ON in step S130 of Fig. 6 if learning of the water temperature evaluation model related quantities is currently being executed since the current start of the internal combustion engine. If the current learning execution flag is ON (Yes), the failure determination device 50 proceeds to step S140, and if the current learning execution flag is not ON (No), the failure determination device 50 proceeds to step S120.

[0050] If the process proceeds to step S120, the failure determination device 50 determines whether the vehicle's soak time (the time during which the internal combustion engine is stopped) is equal to or greater than the sufficient soak time. The sufficient soak time is set to, for example, about 10 hours. If the soak time is equal to or greater than the sufficient soak time (Yes), the failure determination device 50 proceeds to step S125; if not (No), the process shown in FIG. 6 is terminated, and the process returns to step S080 in FIG. 4, thereby terminating the process shown in FIG. 4.

[0051] If the process proceeds to step S125, the failure determination device 50 determines whether the water temperature at startup (the temperature of the cooling water at startup substituted in step S090 of FIG. 4) is within a predetermined temperature range. For example, the predetermined temperature range is a temperature range (predetermined temperature range) that is sufficiently lower than the warm-up completion temperature shown in FIG. 10 and is suitable for learning the water temperature evaluation model related quantities. If the water temperature at startup is within the predetermined temperature range (Yes), the failure determination device 50 proceeds to step S130; if not (No), the process shown in FIG. 6 is terminated, the process returns to the step below step S080 of FIG. 4, and the process shown in FIG. 4 is terminated.

[0052] If the process proceeds to step S130, the failure determination device 50 sets the current learning execution flag to ON (see FIG. 10), and the process proceeds to step S135.

[0053] In step S135, the failure determination device 50 initializes and starts the warm-up timer, and acquires and stores the coolant temperature (measurement start temperature T1) and the time (measurement start time Z1) (see FIG. 10). The failure determination device 50 then proceeds to step S140.

[0054] When the process proceeds to step S140, the failure determination device 50 determines whether the time measured by the warm-up timer is equal to or longer than the measurement end time. The measurement end time is set to, for example, several tens of seconds to several minutes. If the time measured by the warm-up timer is equal to or longer than the measurement end time (Yes), the failure determination device 50 proceeds to step S145; if not (No), the process shown in FIG. 6 is terminated, and the process returns to step S080 in FIG. 4, whereupon the process shown in FIG. 4 is terminated.

[0055] If the process proceeds to step S145, the failure determination device 50 acquires and stores the coolant temperature (measurement end temperature T2) and the time (measurement end time Z2) (see FIG. 10). Then, the failure determination device 50 proceeds to step S150.

[0056] In step S150, the failure determination device 50 calculates the amount of heat input Qin to the internal combustion engine during the measurement period (the period during which the current learning execution flag is ON, from measurement start time Z1 to measurement end time Z2 in FIG. 10) based on the integrated injection amount, and proceeds to step S155. The failure determination device 50 calculates the amount of heat input Qin from the integrated injection amount based on a predetermined arithmetic expression.

[0057] In step S155, the failure determination device 50 estimates the temperature rise state (slope) of the coolant and the amount of coolant in the bypass path based on the input heat amount Qin, (measurement start temperature T1, measurement start time Z1), and (measurement end temperature T2, measurement end time Z2), and proceeds to step S160. When estimating the temperature rise state (slope), the failure determination device 50 estimates it based on, for example, "(measurement end temperature T2 - measurement start temperature T1) / input heat amount Qin" (based on the amount of temperature rise relative to the amount of heat input). When estimating the amount of bypass water, the failure determination device 50 estimates it based on, for example, "input heat amount Qin / (measurement end temperature T2 - measurement start temperature T1)" (based on the amount of heat input relative to the amount of temperature rise).

[0058] In step S160, the failure determination device 50 identifies the model and specifications of the vehicle in which it is installed based on the estimated bypass water volume and temperature rise state (slope), and proceeds to step S165. For example, the storage device (ROM) of the failure determination device 50 pre-stores water temperature evaluation model information shown in FIG. 8. In the water temperature evaluation information shown in FIG. 8, the "vehicle model" stores the name of the vehicle model (vehicle model A, vehicle model B in the example of FIG. 8), etc. In addition, the "specification" stores the name of the specification (specification x, specification y, specification z in the example of FIG. 8), etc. In addition, the "bypass path reference coolant volume" stores the reference water volume of the coolant in the bypass path for that vehicle model and specification. In addition, the "reference heat release volume" stores the reference heat release volume of the coolant into the atmosphere per unit time of the bypass path for that vehicle model and specification. In addition, "Temperature rise amount / input heat amount" stores "(measurement end temperature T2 - measurement start temperature T1) / input heat amount Qin" (slope) that serves as the standard for the bypass route for that vehicle model and specifications. In addition, "water temperature evaluation model standard correction coefficient" stores the water temperature evaluation model correction coefficient (water temperature evaluation model related quantity) that serves as the standard for the bypass route for that vehicle model and specifications.

[0059] The storage device (ROM) of the failure determination device 50 stores a reference water temperature evaluation model shown in FIG. 9. The reference water temperature evaluation model is a water temperature evaluation model that serves as a reference when the failure determination device 50 calculates a water temperature evaluation model for each vehicle in which the failure determination device 50 is installed. For example, a failure determination device 50 installed in a vehicle (vehicle type A, specification x) learns and stores water temperature evaluation model correction coefficients (corresponding to water temperature evaluation model related quantities), and by using these water temperature evaluation model correction coefficients, it is possible to create a "water temperature evaluation model created using water temperature evaluation model related quantities of (vehicle type A, specification x)" as shown by the dotted line in FIG. 9. Furthermore, a failure determination device 50 installed in a vehicle (vehicle type A, specification y) learns and stores water temperature evaluation model correction coefficients (corresponding to water temperature evaluation model related quantities), and by using these water temperature evaluation model correction coefficients, it is possible to create a "water temperature evaluation model created using water temperature evaluation model related quantities of (vehicle type A, specification y)" as shown by the dashed line in FIG. 9.

[0060] In step S165, the failure determination device 50 learns the water temperature evaluation model related quantities and stores them in the non-volatile storage device, and proceeds to step S170. For example, when the failure determination device 50 compares the estimated "temperature rise amount / input heat amount" and "bypass path water amount" with the [water temperature evaluation model information] shown in Fig. 8 and identifies (vehicle type A, specification x), it learns the water temperature evaluation model related quantity KG (water temperature evaluation model correction coefficient) for the vehicle based on the deviation between the estimated "temperature rise amount / input heat amount" and the "temperature rise amount / input heat amount" in the [water temperature evaluation model information] and the "water temperature evaluation model reference correction coefficient" in the [water temperature evaluation model information], and stores it in the non-volatile storage device.

[0061] In step S170, the failure determination device 50 sets the current learning execution flag to OFF, sets the current learning end flag to ON, sets the learning completion flag to ON and stores these in the non-volatile storage device (see FIG. 10), ends the processing shown in FIG. 6, returns the processing to below step S080 in FIG. 4, and ends the processing shown in FIG. 4.

[0062] ●[Calculation of water temperature evaluation model and thermostat failure judgment (Fig. 7)] Next, details of the process of [Calculation of water temperature evaluation model and thermostat failure determination] in step S085 in the flowchart of Fig. 4 will be described using Fig. 7. When executing the process of step S085 in Fig. 4, the failure determination device 50 proceeds to the process of step S210 in Fig. 7.

[0063] In step S210, the failure determination device 50 determines whether the current failure determination end flag is ON. The failure determination end flag is a flag that is set to ON when the thermostat failure determination has been completed since the current start of the internal combustion engine in step S250 of Fig. 7. If the current failure determination end flag is ON (Yes), the failure determination device 50 ends the processing shown in Fig. 7, returns the processing to below step S085 in Fig. 4, and ends the processing shown in Fig. 4; if not (No), the processing proceeds to step S215.

[0064] If the process proceeds to step S215, the failure determination device 50 determines whether the vehicle's soak time (the time during which the internal combustion engine is stopped) is equal to or greater than the sufficient soak time. The sufficient soak time is set to, for example, about 10 hours. If the soak time is equal to or greater than the sufficient soak time (Yes), the failure determination device 50 proceeds to step S225, and if not (No), the failure determination device 50 proceeds to step S220.

[0065] If the processing proceeds to step S220, the failure determination device 50 offsets the reference water temperature evaluation model (see FIG. 9) downward (toward the lower coolant temperature side) according to the outside air temperature, substitutes it into the pre-correction reference water temperature evaluation model, and proceeds to step S230.

[0066] If the process proceeds to step S225, the failure determining device 50 substitutes the reference water temperature evaluation model (see FIG. 9) into the pre-correction reference water temperature evaluation model, and then proceeds to step S230.

[0067] If the process proceeds to step S230, the failure determination device 50 determines whether the water temperature at startup (the temperature of the cooling water at startup substituted in step S090 of FIG. 4) is within a predetermined temperature range. For example, the predetermined temperature range is a temperature range that is sufficiently lower than the warm-up completion temperature shown in FIG. 10 and is suitable for learning the water temperature evaluation model related quantities. If the water temperature at startup is within the predetermined temperature range (Yes), the failure determination device 50 proceeds to step S235; if not (No), the process shown in FIG. 7 is terminated, the process returns to step S085 of FIG. 4, and the process shown in FIG. 4 is terminated.

[0068] If the process proceeds to step S235, the failure determination device 50 reads the learned water temperature evaluation model related quantity KG (water temperature evaluation model correction coefficient) from the nonvolatile storage device, and proceeds to step S240.

[0069] In step S240, the failure determination device 50 calculates (creates) a water temperature evaluation model for each vehicle in which it is installed, as shown in FIG. 9, based on the pre-correction reference water temperature evaluation model and the water temperature evaluation model related quantities (water temperature evaluation model correction coefficients), and proceeds to step S245.

[0070] In step S245, the failure determination device 50 determines whether the thermostat is normal or malfunctioning based on the calculated (created) water temperature evaluation model and the actual state of temperature rise of the coolant in the vehicle, and proceeds to step S250. Note that the process of step S245 is an existing process, so details will be omitted.

[0071] In step S250, the failure determination device 50 sets the current failure determination end flag to ON, terminates the process shown in FIG. 7, returns the process to step S085 in FIG. 4, and terminates the process shown in FIG.

[0072] [Second embodiment (Figs. 11 to 18)] ●[Cooling water circulation path and fault detection device configuration (Fig. 11, Fig. 12)] 11 and 12 show an example of the overall configuration of an internal combustion engine system 2 having a thermostat failure determination device 50 of the second embodiment. The internal combustion engine system 2 of the second embodiment differs from the internal combustion engine system 1 of the first embodiment shown in FIGS. 1 and 2 in that it additionally includes a passenger heater 70, a heater switch 71, a heater fan 72, a heater inlet pipe 73, a heater outlet pipe 74, etc. For example, a passenger heater is not provided in a vehicle intended for a tropical region where temperatures are high throughout the year, whereas a passenger heater is provided in a vehicle intended for a region where temperatures are relatively low in winter. The following mainly describes the differences from the first embodiment.

[0073] Passenger heater 70 is a heater for discharging warm air to an occupant in the vehicle cabin. When an occupant turns on a heater switch 71 provided in front of the occupant's seat, a heater fan 72 provided in passenger heater 70 is driven to discharge warm air toward the occupant. Since the passenger heater 70 extracts heat from the coolant of internal combustion engine 10, when heater switch 71 is turned on, the passenger heater 70 dissipates heat, thereby slowing down the temperature rise of the coolant. The heater usage state (ON / OFF state of heater switch 71) that can detect whether the passenger heater is being used is input to failure determination device 50.

[0074] One end of the heater inlet pipe 73 is connected to a heater outlet port of the internal combustion engine 10. The other end of the heater inlet pipe 73 is connected to a coolant inlet port of the passenger heater 70. One end of the heater discharge pipe 74 is connected to a coolant outlet port of the passenger heater 70. The other end of the heater discharge pipe 74 is connected to the internal combustion engine discharge pipe 61.

[0075] The "bypass route" of the second embodiment shown in Fig. 11 is obtained by adding a "heater route" formed by heater inlet pipe 73, passenger heater 70, and heater discharge pipe 74 to the "bypass route" of the first embodiment shown in Fig. 1. Similarly, the "radiator route" of the second embodiment shown in Fig. 12 is obtained by adding a "heater route" formed by heater inlet pipe 73, passenger heater 70, and heater discharge pipe 74 to the "radiator route" of the first embodiment shown in Fig. 2.

[0076] ●[Example of temperature rise when the thermostat is normal / failed and water temperature evaluation model (Fig. 13)] The example of the temperature rise state of the second embodiment shown in FIG. 13 shows a "normal temperature rise state / fault temperature rise state / water temperature evaluation model when [heater present, heater not in use]" and a "normal temperature rise state / fault temperature rise state / water temperature evaluation model when [heater present, heater in use]" compared to the example of the temperature rise state of the first embodiment shown in FIG. 3. Note that "heater not in use" indicates that the heater is off, and "heater in use" indicates that the heater is on. The "normal temperature rise state / fault temperature rise state / water temperature evaluation model when [heater present, heater in use]" shows a slower temperature rise than the "normal temperature rise state / fault temperature rise state / water temperature evaluation model when [heater present, heater not in use]" due to the increased heat dissipation from the passenger heater.

[0077] [Processing procedure for determining a thermostat failure by the failure determination device 50 (FIGS. 14 to 18)] Next, an example of the processing procedure for "thermostat failure determination" by the failure determination device 50 according to the second embodiment will be described with reference to Figures 14 to 18. In the second embodiment, since some vehicles have an additional passenger heater 70, the water temperature evaluation model related quantities and the water temperature evaluation model are determined depending on whether the passenger heater is present or not and whether the passenger heater is on or off. The failure determination device 50 starts the processing shown in Figure 14 at predetermined time intervals (for example, intervals of several tens to several hundreds of milliseconds), and proceeds to step S010.

[0078] The "overall processing for determining a thermostat failure" of the second embodiment shown in Fig. 14 is different from the "overall processing for determining a thermostat failure" of the first embodiment shown in Fig. 4 in that steps S010 to S020 are added and steps SA105 to SA185 are modified. The following mainly describes the differences from the first embodiment.

[0079] In step S010, the failure determination device 50 determines whether the passenger heater has been turned on at least once in the past (whether the heater switch has been turned on). When the passenger heater has been turned on, the failure determination device 50 stores the history in a non-volatile storage device and uses it in step S010. If the passenger heater has been turned on at least once in the past (Yes), the failure determination device 50 proceeds to step S015, and if not (No), the failure determination device 50 proceeds to step S020.

[0080] If the process proceeds to step S015, the failure determination device 50 assigns (stores) "Yes" to the passenger heater and proceeds to step S030.

[0081] If the process proceeds to step S020, the failure determination device 50 assigns (stores) "absent" to the passenger heater, and proceeds to step S030.

[0082] Steps S030, S035, and S090 are the same as those in the first embodiment shown in FIG. 4, and therefore the description thereof will be omitted.

[0083] In step SA105, the malfunction determination device 50 determines whether the accumulated mileage is equal to or less than the deemed-normal distance. If the accumulated mileage is equal to or less than the deemed-normal distance (Yes), the malfunction determination device 50 proceeds to step SA140. If the accumulated mileage is greater than the deemed-normal distance (No), the malfunction determination device 50 proceeds to step SA110. The accumulated mileage is the accumulated value of the mileage of the vehicle since its factory shipment, and the deemed-normal distance is a preset distance, for example, several hundred kilometers to 1,000 kilometers. If the accumulated mileage is equal to or less than the deemed-normal distance, it is determined that the period since the vehicle was shipped is short and that the thermostat is within the deemed-normal period during which it can be considered normal. The malfunction determination device 50 determines that the thermostat is normal within this deemed-normal period, and proceeds to step SA140.

[0084] If the process proceeds to step SA110, the failure determination device 50 determines whether or not the passenger heater is "present." If the passenger heater is "present" (Yes), the failure determination device 50 proceeds to step SA115, and if not (No), the failure determination device 50 proceeds to step SA135.

[0085] If the process proceeds to step SA115, the failure determination device 50 determines whether the heater-on learning completion flag is OFF. The heater-on learning completion flag is a flag stored in a nonvolatile memory device, and is set to ON when the water temperature evaluation model related quantities for the case when the heater is ON have been learned in a vehicle equipped with a passenger heater. If the heater-on learning completion flag is OFF (Yes), the failure determination device 50 proceeds to step SA120, and if not (No), the failure determination device 50 proceeds to step SA125.

[0086] If the process proceeds to step SA120, the failure determination device 50 determines whether the heater (heater switch) is ON. If the heater is ON (Yes), the failure determination device 50 proceeds to step SA150, and if the heater is OFF (No), the failure determination device 50 proceeds to step SA125. Even if the cumulative mileage exceeds the deemed-normal distance, if the water temperature evaluation model related quantities for when the heater is ON have not yet been learned (heater ON learning completion flag = OFF), if the heater is currently ON, this is an opportunity to learn the water temperature evaluation model related quantities for when the heater is ON, so learning is performed.

[0087] If the process proceeds to step SA125, the failure determination device 50 determines whether a heater-off learning completion flag is OFF. The heater-off learning completion flag is a flag stored in a nonvolatile memory device, and is set ON when the water temperature evaluation model related quantities for the case where the heater is OFF have been learned in a vehicle equipped with a passenger heater. If the heater-off learning completion flag is OFF (Yes), the failure determination device 50 proceeds to step SA130, and if not (No), the failure determination device 50 proceeds to step SA185.

[0088] If the process proceeds to step SA130, the failure determination device 50 determines whether the heater (heater switch) is OFF. If the heater is OFF (Yes), the failure determination device 50 proceeds to step SA155, and if the heater is ON (No), the failure determination device 50 proceeds to step SA185. Even if the cumulative mileage exceeds the deemed-normal distance, if the water temperature evaluation model related quantities for the heater OFF case have not yet been learned (heater OFF learning completion flag = OFF), if the heater is currently OFF, this is an opportunity to learn the water temperature evaluation model related quantities for the heater OFF case, so learning is performed.

[0089] If the process proceeds to step SA135, the failure determination device 50 determines whether the learning completion flag is OFF. The learning completion flag is a flag stored in a non-volatile storage device, and is set ON when the water temperature evaluation model related quantities are learned in a vehicle without a passenger heater. If the learning completion flag is OFF (Yes), the failure determination device 50 proceeds to step SA180, and if not (No), the failure determination device 50 proceeds to step SA185.

[0090] If the process proceeds to step SA140, the failure determination device 50 determines whether or not the passenger heater is "enabled." If the passenger heater is "enabled" (Yes), the failure determination device 50 proceeds to step S145, and if not (No), the failure determination device 50 proceeds to step SA180.

[0091] If the process proceeds to step SA145, the failure determination device 50 determines whether the heater (heater switch) is ON. If the heater is ON (Yes), the failure determination device 50 proceeds to step SA150, and if the heater is OFF (No), the failure determination device 50 proceeds to step SA155.

[0092] If the process proceeds to step SA150, failure determination device 50 sets the heater-on learning start flag to ON and the heater-off learning start flag to OFF, and then proceeds to step SA180. If the vehicle has a passenger heater and learning started with the heater on, the heater-on learning start flag is set to ON.

[0093] If the process proceeds to step SA155, failure determination device 50 sets the heater-on learning start flag to OFF, sets the heater-off learning start flag to ON, and proceeds to step SA180. If the vehicle has a passenger heater and learning started with the heater off, the heater-off learning start flag is set to ON.

[0094] When the process proceeds to step SA180, the failure determination device 50 executes the process of "learning the related quantities of the water temperature evaluation model" and ends the process shown in Fig. 14. The details of "learning the related quantities of the water temperature evaluation model" will be described later.

[0095] If the process proceeds to step SA185, the failure determination device 50 executes the process of [calculation of a water temperature evaluation model and determination of a thermostat failure] and ends the process shown in Fig. 14. Details of [calculation of a water temperature evaluation model and determination of a thermostat failure] will be described later.

[0096] ● [Learning quantities related to the water temperature evaluation model (Fig. 15-Fig. 16)] Next, details of the process of "learning water temperature evaluation model related quantities" in step SA180 in the flowchart of Fig. 14 will be described using Fig. 15. When executing the process of step SA180 in Fig. 14, the failure determination device 50 proceeds to the process of step S110 in Fig. 15. Note that steps S110 to S130 in Fig. 15 are the same as steps S110 to S130 in the first embodiment shown in Fig. 6, so their description will be omitted and the process from step SB110 onwards will be described.

[0097] In step SB110, failure determination device 50 initializes the warm-up timer and proceeds to step SB115. The use of the warm-up timer is the same as in the first embodiment.

[0098] In step SB115, the failure determination device 50 determines whether the passenger heater is "enabled." If the passenger heater is "enabled" (Yes), the failure determination device 50 proceeds to step SB120, and if not (No), the failure determination device 50 proceeds to step SB135.

[0099] If the process proceeds to step SB120, the failure determination device 50 determines whether the heater-ON learning start flag is ON. If the heater-ON learning start flag is ON (Yes), the failure determination device 50 proceeds to step SB125, and if not (No), the failure determination device 50 proceeds to step SB130.

[0100] If the process proceeds to step SB125, the failure determination device 50 acquires and stores the coolant temperature (ON measurement start temperature T21) and the time (ON measurement start time Z21). Then, the failure determination device 50 proceeds to step SB140.

[0101] If the process proceeds to step SB130, the failure determination device 50 acquires and stores the coolant temperature (OFF measurement start temperature T31) and the time (OFF measurement start time Z31). Then, the failure determination device 50 proceeds to step SB140.

[0102] If the process proceeds to step SB135, the failure determination device 50 acquires and stores the coolant temperature (measurement start temperature T1) and the time (measurement start time Z1). Then, the failure determination device 50 proceeds to step SB140.

[0103] When the process proceeds to step SB140, the failure determination device 50 determines whether the time measured by the warm-up timer is equal to or longer than the measurement end time. The measurement end time is set to, for example, several tens of seconds to several minutes. If the time measured by the warm-up timer is equal to or longer than the measurement end time (Yes), the failure determination device 50 proceeds to step SC110 in Fig. 16; if not (No), the process shown in Fig. 15 is terminated, and the process returns to step SA180 in Fig. 14, whereupon the process shown in Fig. 14 is terminated.

[0104] If the process proceeds to step SC110, the failure determination device 50 determines whether the passenger heater is "enabled." If the passenger heater is "enabled" (Yes), the failure determination device 50 proceeds to step SC115, and if not (No), the failure determination device 50 proceeds to step SE130.

[0105] If the process proceeds to step SC115, the failure determination device 50 determines whether the heater (heater switch) is ON. If the heater is ON (Yes), the failure determination device 50 proceeds to step SC120, and if the heater is OFF (No), the failure determination device 50 proceeds to step SD120.

[0106] If the process proceeds to step SC120, the failure determination device 50 determines whether the heater-ON learning start flag is ON. If the heater-ON learning start flag is ON (Yes), the failure determination device 50 proceeds to step SC130. If the heater-ON learning start flag is not ON (No), the failure determination device 50 ends the process shown in FIG. 16, returns the process to below step SA180 in FIG. 14, and ends the process shown in FIG. 14. If the failure determination device 50 started learning (measurement) with the heater ON, and if the heater is still ON when the learning (measurement) ends, it executes learning of the water temperature evaluation model related quantity KG(ON) when the heater is ON from step SC130 onwards.

[0107] If the process proceeds to step SC130, the failure determination device 50 acquires and stores the coolant temperature (ON measurement end temperature T22) and the time (ON measurement end time Z22). Then, the failure determination device 50 proceeds to step SC135.

[0108] In step SC135, the failure determination device 50 calculates the amount of heat input Qin to the internal combustion engine during the measurement period (the period during which the current learning execution flag is ON, from the ON measurement start time Z21 to the ON measurement end time Z22) based on the integrated injection amount, and proceeds to step SC140. The failure determination device 50 calculates the amount of heat input Qin from the integrated injection amount based on a predetermined arithmetic expression.

[0109] In step SC140, the failure determination device 50 estimates the temperature rise state (slope A2) of the coolant and the amount of coolant in the bypass path based on the input heat amount Qin, (ON measurement start temperature T21, ON measurement start time Z21), and (ON measurement end temperature T22, ON measurement end time Z22), and then proceeds to step SC145. When estimating the temperature rise state (slope A2), the failure determination device 50 estimates it based on, for example, "(ON measurement end temperature T22 - ON measurement start temperature T21) / input heat amount Qin" (based on the amount of temperature rise relative to the amount of heat input). When estimating the amount of bypass water, the failure determination device 50 estimates it based on, for example, "input heat amount Qin / (ON measurement end temperature T22 - ON measurement start temperature T21)" (based on the amount of heat input relative to the amount of temperature rise).

[0110] In step SC145, the failure determination device 50 identifies the model and specifications of the vehicle in which the failure determination device 50 is installed based on the estimated bypass water volume and temperature rise state (slope A2), and proceeds to step SC150. For example, the storage device (ROM) of the failure determination device 50 pre-stores water temperature evaluation model information shown in FIG. 18. In the water temperature evaluation information shown in FIG. 18, the "vehicle model" stores the name of the vehicle model (vehicle model A, vehicle model D in the example of FIG. 18). In addition, the "specification" stores the name of the specification (specification x, specification y, specification u, specification v in the example of FIG. 8). In addition, the "passenger heater" stores "not set," "not present," or "present" for the passenger heater. In addition, the "passenger heater usage state" stores "ON" or "OFF" to distinguish between the "bypass path reference coolant volume" and subsequent values ​​when the passenger heater is ON and the "bypass path reference coolant volume" and subsequent values ​​when the passenger heater is OFF. The "bypass route reference coolant volume" stores the reference volume of coolant in the bypass route for that vehicle model and specifications. The "reference heat release volume" stores the reference heat release volume of coolant into the atmosphere per unit time for that vehicle model and specifications (which differs depending on whether the heater is on or off). The "temperature rise / input heat volume" stores the reference "(measurement end temperature T2 - measurement start temperature T1) / input heat volume Qin" (slope) (which differs depending on whether the heater is on or off) for the bypass route for that vehicle model and specifications. The "water temperature evaluation model reference correction coefficient" stores the reference water temperature evaluation model correction coefficient (which differs depending on whether the heater is on or off) (a quantity related to the water temperature evaluation model) for the bypass route for that vehicle model and specifications.

[0111] In step SC150, the failure determination device 50 learns the water temperature evaluation model related quantity KG(ON) when the passenger heater is "present" and the heater is ON, stores it in the nonvolatile storage device, and proceeds to step SC155. For example, when the failure determination device 50 compares the estimated "temperature rise amount / input heat amount" and "bypass path water volume" with the [water temperature evaluation model information] shown in Figure 18 and identifies (vehicle type D, specification u, heater ON), it learns the water temperature evaluation model related quantity KG(ON) (water temperature evaluation model correction coefficient) for the vehicle based on the deviation between the estimated "temperature rise amount / input heat amount" and the "temperature rise amount / input heat amount" in the [water temperature evaluation model information] and the "water temperature evaluation model reference correction coefficient" in the [water temperature evaluation model information], and stores it in the nonvolatile storage device.

[0112] In step SC155, the failure determination device 50 sets the current learning in progress flag to OFF, sets the current learning end flag to ON, sets the heater-ON learning completion flag to ON and stores these in the non-volatile storage device, ends the processing shown in FIG. 16, returns the processing to below step SA180 in FIG. 14, and ends the processing shown in FIG. 14.

[0113] If the process proceeds to step SD120, the failure determination device 50 determines whether the heater-off learning start flag is ON. If the heater-off learning start flag is ON (Yes), the failure determination device 50 proceeds to step SD130. If the heater-off learning start flag is not ON (No), the failure determination device 50 ends the process shown in FIG. 16, returns the process to below step SA180 in FIG. 14, and ends the process shown in FIG. 14. If the failure determination device 50 started learning (measurement) with the heater off, and if the heater is still off when the learning (measurement) ends, it executes learning of the water temperature evaluation model related quantity KG(OFF) when the heater is off from step SD130 onwards.

[0114] If the process proceeds to step SD130, the failure determination device 50 acquires and stores the coolant temperature (OFF measurement end temperature T32) and the time (OFF measurement end time Z32). Then, the failure determination device 50 proceeds to step SD135.

[0115] In step SD135, the failure determination device 50 calculates the input heat quantity Qin to the internal combustion engine during the measurement period (the period during which the current learning execution flag is ON, from the OFF measurement start time Z31 to the OFF measurement end time Z32) based on the integrated injection amount, and proceeds to step SD140. The failure determination device 50 calculates the input heat quantity Qin from the integrated injection amount based on a predetermined arithmetic expression.

[0116] In step SD140, the failure determination device 50 estimates the temperature rise state (slope A3) of the coolant and the amount of coolant in the bypass path based on the input heat amount Qin, (OFF measurement start temperature T31, OFF measurement start time Z31), and (OFF measurement end temperature T32, OFF measurement end time Z32), and then proceeds to step SD145. When estimating the temperature rise state (slope A3), the failure determination device 50 estimates it based on, for example, "(OFF measurement end temperature T32 - OFF measurement start temperature T31) / input heat amount Qin" (based on the amount of temperature rise relative to the amount of heat input). When estimating the amount of bypass water, the failure determination device 50 estimates it based on, for example, "input heat amount Qin / (OFF measurement end temperature T32 - OFF measurement start temperature T31)" (based on the amount of heat input relative to the amount of temperature rise).

[0117] In step SD145, the failure determination device 50 identifies the model and specifications of the vehicle in which it is installed based on the estimated bypass water volume and temperature rise state (gradient A3), and proceeds to step SD150. For example, the water temperature evaluation model information shown in Fig. 18 is pre-stored in the storage device (ROM) of the failure determination device 50. Note that the water temperature evaluation model information shown in Fig. 18 has already been explained, so its explanation will be omitted.

[0118] In step SD150, the failure determination device 50 learns the water temperature evaluation model related quantity KG(OFF) when the passenger heater is "present" and the heater is OFF, stores it in the nonvolatile storage device, and proceeds to step SD155. For example, when the failure determination device 50 compares the estimated "temperature rise amount / input heat amount" and "bypass path water volume" with the [water temperature evaluation model information] shown in Figure 18 and identifies (vehicle type D, specification u, heater OFF), it learns the water temperature evaluation model related quantity KG(OFF) (water temperature evaluation model correction coefficient) for the vehicle based on the deviation between the estimated "temperature rise amount / input heat amount" and the "temperature rise amount / input heat amount" in the [water temperature evaluation model information] and the "water temperature evaluation model reference correction coefficient" in the [water temperature evaluation model information], and stores it in the nonvolatile storage device.

[0119] In step SD155, the failure determination device 50 sets the current learning in progress flag to OFF, sets the current learning end flag to ON, sets the heater-off learning completion flag to ON and stores these in the non-volatile memory device, ends the processing shown in FIG. 16, returns the processing to below step SA180 in FIG. 14, and ends the processing shown in FIG. 14.

[0120] If the process proceeds to step SE130, the failure determination device 50 acquires and stores the coolant temperature (measurement end temperature T2) and the time (measurement end time Z2). Then, the failure determination device 50 proceeds to step SE135.

[0121] In step SE135, the failure determination device 50 calculates the amount of heat input Qin to the internal combustion engine during the measurement period (the period during which the current learning execution flag is ON, from measurement start time Z1 to measurement end time Z2) based on the integrated injection amount, and proceeds to step SE140. The failure determination device 50 calculates the amount of heat input Qin from the integrated injection amount based on a predetermined arithmetic expression.

[0122] In step SE140, the failure determination device 50 estimates the temperature rise state (slope A1) of the coolant and the amount of coolant in the bypass path based on the input heat amount Qin, (measurement start temperature T1, measurement start time Z1), and (measurement end temperature T2, measurement end time Z2), and proceeds to step SE145. When estimating the temperature rise state (slope A1), the failure determination device 50 estimates it based on, for example, "(measurement end temperature T2 - measurement start temperature T1) / input heat amount Qin" (based on the amount of temperature rise relative to the amount of heat input). When estimating the amount of bypass water, the failure determination device 50 estimates it based on, for example, "input heat amount Qin / (measurement end temperature T2 - measurement start temperature T1)" (based on the amount of heat input relative to the amount of temperature rise).

[0123] In step SE145, the failure determination device 50 identifies the model and specifications of the vehicle in which it is installed based on the estimated bypass water volume and temperature rise state (gradient A1), and proceeds to step SE150. For example, the storage device (ROM) of the failure determination device 50 pre-stores water temperature evaluation model information shown in Fig. 18. Note that the water temperature evaluation model information shown in Fig. 18 has already been explained, so its explanation will be omitted.

[0124] In step SE150, the failure determination device 50 learns the water temperature evaluation model related quantity KG for the case where the passenger heater is "not provided" and stores it in the nonvolatile storage device, and then proceeds to step SE155. For example, when the failure determination device 50 compares the estimated "temperature rise amount / input heat amount" and "bypass route water volume" with the [water temperature evaluation model information] shown in Fig. 18 and identifies the vehicle as (vehicle type D, specification x), it learns the water temperature evaluation model related quantity KG (water temperature evaluation model correction coefficient) for the vehicle based on the deviation between the estimated "temperature rise amount / input heat amount" and the "temperature rise amount / input heat amount" in the [water temperature evaluation model information] and the "water temperature evaluation model reference correction coefficient" in the [water temperature evaluation model information], and stores it in the nonvolatile storage device.

[0125] In step SE155, the failure determination device 50 sets the current learning in progress flag to OFF, sets the current learning end flag to ON, sets the learning completion flag to ON and stores these in the non-volatile storage device, ends the processing shown in FIG. 16, returns the processing to below step SA180 in FIG. 14, and ends the processing shown in FIG. 14.

[0126] ●[Calculation of water temperature evaluation model and thermostat failure judgment (Fig. 17)] Next, details of the processing of [Calculation of water temperature evaluation model and thermostat failure determination] in step SA185 in the flowchart of Fig. 14 will be described using Fig. 17. When executing the processing of step SA185 in Fig. 14, the failure determination device 50 proceeds to the processing of step S210 in Fig. 17. Note that steps S210 to S230 and steps S240 to S250 in Fig. 17 are similar to steps S210 to S230 and steps S240 to S250 in the first embodiment shown in Fig. 7, so their description will be omitted and the processing of steps SF110 to SF130 will be described.

[0127] If the process proceeds to step SF110, the failure determination device 50 determines whether the passenger heater is "enabled." If the passenger heater is "enabled" (Yes), the failure determination device 50 proceeds to step SF115, and if not (No), the failure determination device 50 proceeds to step SF130.

[0128] If the process proceeds to step SF115, the failure determination device 50 determines whether the heater (heater switch) is ON. If the heater is ON (Yes), the failure determination device 50 proceeds to step SF120, and if the heater is OFF (No), the failure determination device 50 proceeds to step SF125.

[0129] If the process proceeds to step SF120, the failure determination device 50 reads the water temperature evaluation model related quantity KG(ON) corresponding to the passenger heater being "enabled" and the heater being ON from the nonvolatile storage device, and proceeds to step S240.

[0130] If the process proceeds to step SF125, the failure determination device 50 reads the water temperature evaluation model related quantity KG(OFF) corresponding to passenger heater="Yes" and heater="Off" from the nonvolatile storage device, and proceeds to step S240.

[0131] If the process proceeds to step SF130, the failure determination device 50 reads the water temperature evaluation model related quantity KG corresponding to passenger heater="none" from the nonvolatile storage device, and proceeds to step S240.

[0132] The failure determination device 50 (CPU 51), which executes the processing of steps S040 and S080 in FIG. 4 ("Learning water temperature evaluation model related quantities" in FIG. 6) and steps SA105 and SA180 in FIG. 14 ("Learning water temperature evaluation model related quantities" in FIGS. 15 and 16), corresponds to a water temperature evaluation model related quantity memory unit 51A (see FIGS. 1, 2, 11, and 12), which assumes that the thermostat is normal during a predetermined period from the vehicle's factory shipping state during which the thermostat can be assumed to be normal, and learns and stores in a non-volatile memory device, for each vehicle, water temperature evaluation model related quantities related to the water temperature evaluation model, which is a temperature rise state for determining whether the thermostat has failed, based on the actual temperature rise state of the coolant after the start of the internal combustion engine.

[0133] Furthermore, the failure determination device 50 (CPU 51) that executes the processing of step S040 and step S085 in FIG. 4 (calculation of water temperature evaluation model and determination of thermostat failure) in FIG. 7 and step SA105 and step SA185 in FIG. 14 (calculation of water temperature evaluation model and determination of thermostat failure) in FIG. 17 corresponds to a thermostat failure determination unit 51B (see FIGS. 1, 2, 11, and 12) that determines a thermostat failure after the normality-presuming period has elapsed, based on the actual temperature rise state of the coolant after the internal combustion engine has been started and a water temperature evaluation model for each vehicle that is based on stored water temperature evaluation model-related quantities.

[0134] In the second embodiment, an example has been described in which one passenger heater is provided (only in the front seat), but there are also vehicles in which two passenger heaters are provided (one in the front seat and one in the rear seat). When passenger heaters are provided in the front seat and the rear seat, a passenger heater 70 for the rear seat, a heater switch 71, a heater fan 72, a heater inlet pipe 73, and a heater outlet pipe 74 are further added to the configurations in Figures 11 and 12.

[0135] In the processing procedure of the second embodiment, which assumes that one passenger heater is provided (only in the front seat), the cases are divided into passenger heater (no passenger heater), passenger heater (present) and heater OFF, and passenger heater (present) and heater ON. Therefore, in the processing procedure assuming that two passenger heaters are provided (in the front seat and in the rear seat), the cases can be divided into passenger heater (no passenger heater), passenger heater (present) and front seat heater OFF and rear seat heater OFF, passenger heater (present) and front seat heater ON and rear seat heater OFF, passenger heater (present) and front seat heater OFF and rear seat heater ON, and passenger heater (present) and front seat heater ON and rear seat heater ON, but detailed explanations will be omitted.

[0136] According to the failure determination device 50 described above in the first and second embodiments, the failure determination device 50 creates a water temperature evaluation model for each vehicle depending on the vehicle model, specifications, etc., and therefore can appropriately determine a thermostat failure with fewer steps.

[0137] ●[Other] The thermostat failure determination device 50 of the present invention is not limited to the appearance, configuration, structure, processing procedures, etc. described in this embodiment, and various changes, additions, and deletions are possible within the scope of the present invention. For example, the processing procedures of the failure determination device 50 are not limited to the processing of the flowcharts shown in Figures 4 to 7 and Figures 14 to 17.

[0138] In the description of this embodiment, the deemed-normal period is defined as the period during which the cumulative mileage of the vehicle from the factory shipping state is equal to or less than the deemed-normal distance, but this is not limited to this. For example, the deemed-normal period may be a period of a predetermined number of days or less from the factory shipping state of the vehicle, or may be a period until the water temperature evaluation model related quantities have been learned N times (for example, 20 times).

[0139] Furthermore, expressions such as "greater than or equal to (≧)," "less than or equal to (≦)," "greater than (>)," and "less than (<)" may or may not include an equal sign. Furthermore, the numerical values ​​used in the description of this embodiment are merely examples, and the present invention is not limited to these numerical values. [Explanation of symbols]

[0140] 1, 2 Internal combustion engine system 10 Internal combustion engine 20 Radiator 31 Coolant temperature detector 32 Crank rotation detector 33 Ignition switch 34 Water pump 40 Thermostat 41 Valve body 50 Failure determination device 51 CPU 51A Water temperature evaluation model related quantity memory section 51B Thermostat failure determination unit 52 RAM 53 ROM 54 Timer 55 Non-volatile storage 61 Internal combustion engine discharge piping 62 Bypass piping 63 Radiator inlet pipe 64 Radiator discharge pipe 65 Internal combustion engine inlet piping 70 Passenger heater 71 Heater switch 72 Heater fan 73 Heater inlet piping 74 Heater discharge piping

Claims

1. A thermostat failure determination device that determines a failure of a thermostat provided in a cooling water circulation path of an internal combustion engine mounted on a vehicle, comprising: The circulation path is a radiator path that cools the cooling water discharged from the internal combustion engine in a radiator and returns the cooling water to the internal combustion engine; and a bypass path that returns the cooling water discharged from the internal combustion engine to the internal combustion engine without passing through the radiator, The thermostat comprises: the circulation path is switched so that when the temperature of the cooling water is lower than a warm-up completion temperature, the circulation path is set to the bypass path, and when the temperature of the cooling water is equal to or higher than the warm-up completion temperature, the circulation path is set to the radiator path; The failure determination device a water temperature evaluation model related quantity storage unit that, during a predetermined period from the product shipping state of the vehicle during which the thermostat can be considered to be normal, considers the thermostat to be normal, and learns and stores in a non-volatile storage device, for each vehicle, a water temperature evaluation model related quantity that is related to a water temperature evaluation model that is the temperature rise state for determining whether the thermostat has failed, based on an actual temperature rise state of the coolant after startup of the internal combustion engine; a thermostat malfunction determination unit that, after the deemed-normal period has elapsed, determines whether the thermostat has malfunctioned based on the actual temperature rise state of the coolant after the internal combustion engine has been started and the water temperature evaluation model for each vehicle that is based on the stored water temperature evaluation model related quantities; and The water temperature evaluation model is a normal temperature rise state, which is a temperature rise state of the cooling water when the internal combustion engine is started from a state in which the temperature of the cooling water is lower than the warm-up completion temperature, the thermostat is normal, and the circulation path is set to the bypass path; a failure temperature rise state in which the temperature of the cooling water rises at a gentler rate than the normal temperature rise state when the internal combustion engine is started from a state in which the temperature of the cooling water is lower than the warm-up completion temperature and the thermostat is malfunctioning and the circulation path is set to the radiator path; the temperature rise state is distinguishable between the normal temperature rise state and the fault temperature rise state, The failure determination device includes: a reference water temperature evaluation model that serves as a reference for the temperature rise state of the cooling water after the start of the internal combustion engine is stored; The failure determination device the water temperature evaluation model related quantity storage unit learns the water temperature evaluation model related quantity for making the reference water temperature evaluation model closer to the water temperature evaluation model corresponding to the vehicle in which the reference water temperature evaluation model is installed, based on the actual temperature rise state of the coolant after the start of the internal combustion engine, and stores the learned water temperature evaluation model related quantity in the non-volatile storage device; the thermostat failure determination unit creates the water temperature evaluation model according to the vehicle in which the thermostat failure determination unit is installed, based on the reference water temperature evaluation model and the water temperature evaluation model related quantity, and determines whether the thermostat has failed. Thermostat failure detection device.

2. A failure determination device for a thermostat according to claim 1, The failure determination device includes, in the water temperature evaluation model related quantity storage unit, an amount of temperature rise of the cooling water in the bypass path during a period from the start of measurement to the end of measurement, based on the temperature of the cooling water at the start of measurement when the internal combustion engine is started in a state where the temperature of the cooling water is lower than the warm-up completion temperature, and the temperature of the cooling water at the end of measurement after a predetermined time has elapsed from the start of measurement; an input heat quantity that is a heat quantity based on an integrated amount of fuel injection amount into the internal combustion engine during a period from the start of the measurement to the end of the measurement; a bypass passage water volume, which is the volume of the cooling water circulating in the bypass passage, based on the calculated bypass passage water volume; and learning the water temperature evaluation model related quantity based on the calculated bypass passage water volume. Thermostat failure detection device.

3. A failure determination device for a thermostat according to claim 1 or 2, The vehicle includes: The vehicle may be provided with a passenger heater that discharges warm air to passengers in the vehicle cabin. When the passenger heater is provided, a heater path for passing the cooling water to the passenger heater is added to the radiator path and the bypass path; The failure determination device receives a heater usage status that can detect whether the passenger heater is in use, The failure determination device When it is determined based on the heater usage state that the vehicle in which the vehicle is installed has the passenger heater, the water temperature evaluation model related quantity storage unit separately learns and stores the water temperature evaluation model related quantity when the passenger heater is in use and the water temperature evaluation model related quantity when the passenger heater is not in use; the thermostat failure determination unit creates the water temperature evaluation model for each vehicle based on the water temperature evaluation model related quantities for when the passenger heater is used, when the passenger heater is used, and creates the water temperature evaluation model for each vehicle based on the water temperature evaluation model related quantities for when the passenger heater is not used, when the passenger heater is not used; Thermostat failure detection device.

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