JP2009074430A - Failure diagnosis device and failure diagnosis method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stable failure judgment not influenced by an operation condition of an internal combustion engine. <P>SOLUTION: The failure diagnosis device of an internal combustion engine cooling system provided with a water pump for circulating cooling water for cooling the water cooled internal combustion engine, a thermostat for opening and closing a channel of cooling water flowing to a radiator, a radiator fan for accelerating heat radiation of the radiator, and a water temperature sensor measuring temperature of cooling water, has a failure judgment function capable of judging a failure of the internal combustion engine cooling system by temperature change of cooling water accompanying operation and stop of the water pump, the radiator fan and the thermostat during operation of the internal combustion engine. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an internal combustion engine cooling system failure diagnosis device and a failure diagnosis method for determining a failure in a cooling system of a water-cooled internal combustion engine.

  In general, in a water-cooled internal combustion engine, in order to prevent an excessive increase in temperature of the internal combustion engine, a cooling water passage, a water pump for circulating the cooling water, and the raised cooling water are radiated to the atmosphere. A radiator and a thermostat for opening and closing the water channel of the cooling water flowing to the radiator according to the cooling water temperature are provided.

  That is, when the cooling water temperature is lower than a predetermined value (usually 75 ° C.) immediately after starting the internal combustion engine or during warm-up operation, the thermostat is closed, while when the cooling water temperature is higher than the predetermined value, the thermostat is The valve is opened, and the cooling water is circulated between the internal combustion engine and the radiator.

  Further, the radiator dissipates the heat of the cooling water to the atmosphere by means of the vehicle running wind and the means for cooling the radiator (radiator fan) to prevent the cooling water from excessively rising (overheating).

  In addition to a system for driving the cooling water from the output shaft of the internal combustion engine, there is an electric pump that controls the cooling flow rate as required.

  If the above-mentioned components of the cooling system of the internal combustion engine fail, for example, if a failure occurs in which the water pump or the radiator fan is fixed in a stopped state, the cooling water temperature rises excessively and the internal combustion engine may be damaged. .

  On the other hand, if a failure occurs in which the water pump or radiator fan is fixed in the start-up state or a failure occurs in which the thermostat is fixed in the valve-open state, the cooling water temperature does not reach or reaches the reference temperature. Therefore, the temperature rise of the cooling water of the internal combustion engine may be hindered, leading to deterioration of fuel consumption, increase of exhaust emission, and deterioration of the heater performance of the vehicle.

  Therefore, as a technique for determining a failure in the cooling system, for example, a failure diagnosis of an open failure in which the thermostat remains open is proposed in Japanese Patent Laid-Open No. 2000-320389 (Patent Document 1). In the failure diagnosis of the above publication, when the fuel consumption from the start of the engine is equal to or greater than a predetermined amount, the thermostat is determined to be defective when the rise in the coolant temperature is small.

  Further, the present inventors have determined that the cooling system has failed based on the rate of water temperature rise when the radiator fan is started below the thermostat open set temperature, so that the operating mode in which the rate of temperature rise of the cooling water in the internal combustion engine is fast. (For example, even when the cooling water temperature at the start is high. The vehicle speed is low and the traveling wind does not sufficiently hit the radiator), a method for performing stable failure determination has been proposed.

JP 2000-320389 A

  Each of the above-described conventional inventions is a technique for determining a failure based on the change rate of the cooling water temperature during operation of the internal combustion engine. Accurate determination is possible due to the heat generation state due to the load of the internal combustion engine, the influence of traveling wind, etc. It was difficult.

  The present invention has been made in view of the above problems, and its object is to provide a stable failure determination that is not affected by the operating state of the internal combustion engine and to identify the content of the failure. It is to provide a failure diagnosis apparatus.

  The present invention relates to a cooling water circulation water pump for cooling a water-cooled internal combustion engine, a thermostat for opening and closing a cooling water flow path flowing through the radiator, and a radiator fan for promoting heat dissipation of the radiator, An internal combustion engine cooling system failure diagnosis device comprising: a water temperature sensor for measuring a temperature of the cooling water; and a temperature of the cooling water that is caused by operating and stopping the water pump, the radiator fan, and the thermostat during the operation of the internal combustion engine. It has a failure determination function capable of determining a failure of the internal combustion engine cooling system by a change.

  As described above, it is possible to eliminate the influence of the heat generation state of the internal combustion engine, traveling wind, and the like by determining the failure based on the temperature change of the cooling water when the water pump, the radiator fan, and the thermostat are operated.

  Furthermore, another invention related to the present invention has the following features.

  During operation of the internal combustion engine, the water pump and the radiator fan are started, and the failure of the water pump, the radiator fan, and the thermostat is determined based on the change rate of the cooling water temperature at that time.

  When the water pump and the radiator fan are stopped during the operation of the internal combustion engine, the circulation of the cooling water and the cooling by the radiator fan are lost, and depending on the operating state, only the cooling by the traveling wind is performed, and the cooling water temperature rises for a certain period.

  Here, when the water pump and the radiator fan are started again, if the cooling water temperature does not drop, it is possible that the water pump or the radiator fan cannot be started in the stopped state and the stop state is fixed.

  On the other hand, if the cooling water temperature significantly decreases during the operation of the internal combustion engine, it is possible that the water pump or the radiator fan cannot be stopped in the activated state.

  Further, when the water pump and the radiator fan are started from a stopped state, the cooling water temperature is usually lowered due to heat radiation from the radiator. However, when the cooling water temperature decrease is small, it is possible that the water pump or the radiator fan is fixed in a stopped state where it cannot be started or that the performance is degraded.

  If it is determined that the water pump or radiator fan cannot be stopped, it is determined that the failure is fixed in the starting state, and the operation for determining the failure of the performance degradation of the water pump and radiator fan cannot be performed normally. Like that.

  Furthermore, if it is determined that the performance of the water pump and radiator fan has deteriorated, the malfunction of the thermostat cannot be determined normally because the cooling water circulation and the heat radiation from the radiator do not function sufficiently. Prohibit diagnosis.

  According to the present invention, it is possible to perform a stable failure diagnosis of the cooling system without being influenced by disturbances such as heat generation from the internal combustion engine and traveling wind.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an overall configuration of an engine system including a failure diagnosis device for a cooling system of an internal combustion engine according to the present embodiment.

  The internal combustion engine 1 is an in-line four-cylinder engine, and air sucked from the inlet 2 of the air cleaner 1 enters the throttle body 4 through the intake duct 3. The intake duct 3 has an air flow meter (air flow meter) 5 for detecting the amount of intake air, the throttle throttle body 4 has a throttle valve 6 for controlling the air flow rate, and the opening of the throttle valve 6 is measured. A throttle sensor 7 is installed at each appropriate position.

  Further, the throttle body 4 is provided with an auxiliary air valve (ISC valve) 8 that bypasses the throttle valve 6, and the air amount is controlled so that the idling speed is kept constant.

  The air passing through the throttle body 4 enters the surge tank 9, is distributed by the intake manifolds 10a, 10b, 10c, and 10d and enters the cylinder.

  On the other hand, fuel in a fuel tank (not shown) is sucked and pressurized by a fuel pump (not shown), passes through a fuel filter (not shown), and is installed in the intake manifolds 10a, 10b, 10c, and 10d. The fuel is supplied to the fuel injection valves (injectors) 11a, 11b, 11c, and 11d, which are one mode of the means for injecting the injected fuel into the combustion chamber.

  The air-fuel mixture in the cylinder is ignited and burned by a spark plug (not shown), then sent to the exhaust manifold (not shown) side and purified by a front catalyst and a main catalyst (not shown). It is discharged via (not shown).

  A water jacket 20 is provided inside the cylinder block and cylinder head of the engine, and cooling water is injected into the water jacket. The cooling water of the water jacket 20 flows into the radiator 21 and the heater core 22.

  The cooling water that has entered the heater core 22 is returned again into the water jacket 20 via the thermostat 23. Before returning to the water jacket 20, an electric water pump 24 is attached, and the water pump is driven according to the engine rotation load and the cooling water temperature to circulate the cooling water.

  At this time, if the cooling water flowing through the thermostat 23 is lower than the opening temperature of the thermostat, the cooling water circulates from the water jacket 20 → the heater core 22 → the thermostat 23 → the water pump 24 → the water jacket 20, and the cooling water rises. Promotes temperature.

  On the other hand, the heat of the cooling water that has entered the radiator 21 is dissipated to the atmosphere by the running radiator or the electric radiator fan 25 for cooling the radiator. The cooled cooling water reaches the aforementioned thermostat 23.

  Here, when the temperature of the cooling water circulating through the water jacket 20 exceeds the valve opening temperature of the thermostat 23, the thermostat is opened, and the cooling water cooled by the radiator 21 also passes through the water pump 24. Into the water jacket 20.

  When the coolant temperature measured by the coolant temperature sensor 26 installed in the water jacket rises and exceeds the set temperature, the cooling electric radiator fan 25 attached to the radiator 21 is activated, and the heat of the coolant by the radiator 21 is activated. Promotes heat dissipation to the atmosphere.

  Cam angle sensor (not shown), air flow meter 5, throttle angle sensor 7, O2 sensor (not shown), which are basic signals for controlling engine speed detection, fuel injection timing and ignition timing, A signal indicating the engine state, such as the water temperature sensor 26 that detects the temperature, is input to an engine control device (control unit) 30 including the diagnosis device 30.

  Based on these signals, the control unit 30 performs various arithmetic operations such as air-fuel ratio control by performing predetermined arithmetic processing, and injectors 11a, 11b, 11c, 11d, the ISC valve 8, the electric radiator fan 21, the electric water. Each drive signal is output to the pump 24 and the like.

  FIG. 2 shows the internal configuration of the control unit 30.

  The control unit 30 is composed of an MPU 31, a read / write RAM 32, a read-only ROM 33, and an I / O LSI 34 for controlling input / output, which are connected via buses 35, 36 and 37, respectively, and exchange data.

  Specifically, the MPU 31 receives from the signal I / OLSI 34 indicating the engine state such as the air flow meter 5, the throttle angle sensor 8, the water temperature sensor 26, etc. through the bus 37, and sequentially calls the processing contents stored in the ROM 33. After the processing is performed and stored in the RAM 32, each drive signal is output again from the I / O LSI 34 to the injectors 11a, 11b, 11c, 11d, the radiator cooling electric fan 21, the ISC valve 8, the electric water pump 24, and the like. .

  FIG. 3 is an overall control flowchart of the engine system including the failure diagnosis apparatus for the cooling system of the internal combustion engine according to the present embodiment.

  First, at step 101, when the state is shifted to during the operation of the internal combustion engine, the routine proceeds to stage 1 of step 102 where it is determined whether the water pump and the radiator fan are stationary or not. Next, in step 103, a failure is determined in stage 1, and if it is not determined to be normal, the process proceeds to stage 2 in step 106 where a failure in fixing the startup state of the water pump and the radiator fan is determined.

  If it is determined in stage 103 of step 103 that the water pump and the radiator fan are in a fixed stop state, the contents of the failure are stored in the engine control unit (control unit) 30 in step 104, and a warning is issued in step 105. Turns on the lamp and gives a warning to the driver.

  When the process proceeds to stage 2 in step 106, it is determined in step 107 whether or not the coolant temperature TW is not higher than the thermostat valve opening or valve closing set temperature THMO [° C.] (for example, 75 ° C.) (eg, 75 ° C.). If YES, the routine proceeds to step 108, where the failure determination of the thermostat valve open fixed state is performed. A failure in which the thermostat is restrained in the valve open state and cannot be closed is called a valve closing failure.

  If it is not determined in step 108 that the thermostat is in a fixed valve open state, it is determined normal in all the failure diagnosis apparatuses according to the embodiments of the present invention, and the failure diagnosis is terminated.

  If it is determined in step 108 that the thermostat is in a valve open fixed state, the failure content is stored in the engine control device (control unit) 30 in step 109, the failure information is stored, and in step 110. The warning lamp is turned on, and the failure diagnosis according to the embodiment of the present invention is terminated.

  The above-mentioned fault diagnosis is performed by performing arithmetic processing on the signals of various devices including thermostats, water pumps, radiator fans, and water temperature sensors according to the program, so stable diagnosis is easy without using complicated hardware configurations. It can be realized with a simple configuration.

  FIG. 4 shows an actual operation diagram of the above-described failure diagnosis contents.

  FIG. 4 shows the operating conditions of the water pump, the radiator fan, and the thermostat in the embodiment of the present invention, and the transition of the cooling water temperature when the internal combustion engine cooling system is normal.

  Next, details of the diagnosis contents of each stage will be described.

  First, the contents of failure diagnosis of stage 1 will be described with reference to FIG.

  When stage 1 is started in step 201, the coolant temperature TW is captured as TWST11 in step 202. In step 203, the radiator fan is activated.

  Next, in step 204, it is determined whether or not ST1TM1 [sec] (for example, 120 sec) has elapsed since the start of stage 1, and if it has elapsed, the process proceeds to step 206. If not, the determination in step 204 is performed. repeat.

  In step 206, the coolant temperature TW is captured again as TWST12, and the process proceeds to step 207.

  In step 207, it is determined whether or not the value obtained by subtracting the coolant temperature TWST11 captured in step 204 from the coolant temperature TWST12 captured in step 206 is greater than a failure determination value JTWST11 (eg, 3 ° C.), and is equal to or greater than JTWST11. If this is the case, it is determined as normal in step 208, and the stage 1 failure diagnosis is terminated.

  If it is determined in step 207 that the failure determination value is JTWST11S1 or less, the cooling water temperature does not decrease even if the cooling water is not circulated by the water pump or the air in the engine room is circulated by the radiator fan. Therefore, it is determined in step 209 that the water pump is in a fixed start state failure (water pump start-up failure) or a radiator fan start-up state fixed failure (radiator fan start-up failure). Proceed to

  In step 210, it is determined whether or not a value obtained by subtracting the coolant temperature TWST11 captured in step 204 from the coolant temperature TWST12 captured in step 206 is greater than a failure determination value JTWST12 (for example, −10 ° C.).

  If it is greater than JTWST12, it is determined at step 211 that the water pump only has a fixed start-up failure, and the stage 1 failure diagnosis is terminated.

  If it is determined in step 210 that JTWST122 or lower, the cooling water is circulated by the water pump and the cooling water is assumed to have been radiated from the radiator by the radiator fan. Therefore, both the water pump and the radiator fan are started in step 212. It is determined that the state is fixed, and the failure diagnosis of stage 1 is terminated.

  In FIG. 6, the operation of the water pump, the radiator fan, and the thermostat in the above-described stage 1, the transition of the cooling water temperature when the water pump and the radiator fan are normal, and the failure state where the water pump and the radiator fan are fixed in the starting state. Shows the transition of the cooling water temperature.

  According to FIG. 6, the operation of the water pump and the radiator fan is instructed for a predetermined time width from the stage 1 during operation of the internal combustion engine, and the temperature change amount of the cooling water detected within the predetermined time width is equal to or less than a predetermined value ( At the time of the dotted line), it is determined that the water pump or the radiator fan has failed to start.

  Conversely, when the temperature change amount of the cooling water is equal to or greater than a predetermined value (solid line), it is determined that the water pump or the radiator fan is normally started.

  Next, the failure diagnosis contents of stage 2 will be described with reference to FIG.

  First, when stage 2 is started in step 301, the cooling water temperature TW at that time is captured as TWST 21 in step 302, and the process proceeds to step 303.

  In step 303, it is determined whether or not ST2TM1 [sec] (for example, 30 sec) has elapsed from stage 2, and if ST2TM1 has elapsed, the process proceeds to step 304.

  If ST2TM1 has not elapsed, the determination in step 304 is repeated until it has elapsed. In step 304, the coolant temperature TW at that time is captured again as TWST22, and the process proceeds to step 305.

  In step 305, the temperature change amount DTWST21 of the cooling water is calculated by equation (1), and the process proceeds to step 306.

DTWST21 = TWST21-TWST22 (1) Equation (1) In step 306, the cooling water temperature TW is less than or equal to the set temperature THMO [° C.] (eg, 75 ° C.) of the thermostat installed in the internal combustion engine. It is determined whether or not there is, and if it is determined that the temperature is equal to or lower than THMO [° C.], the process proceeds to step 307.

  If it is determined that it is greater than THMO [° C.] (the diagnosis ends as OK), the operation of step 306 is repeated until it is determined that THMO [° C.] or less.

  In step 307, it is determined whether or not the elapsed time from establishment of 306 has passed ST2TM2 [sec] (for example, 60 sec). If ST2TM2 has passed, the process proceeds to step 308, and if S2TM2 has not passed, The operation of step 307 is repeated.

  In step 308, the water temperature TW at that time is captured as TWST 23, and the process proceeds to step 309.

  In step 309, it is determined whether or not the elapsed time after capturing the water temperature in step 308 has elapsed ST2TM3 [sec] (for example, 300 sec). If S2TM3 has elapsed, the process proceeds to step 310, and ST2TM3 has elapsed. If not, the operation of step 309 is repeated.

  In step 310, the coolant temperature TW at that time is captured as TWST 24, and the process proceeds to step 311. In step 311, the cooling water temperature change amount DTW 22 is calculated by equation (2), and the process proceeds to step 312.

DTWST22 = TWST23−TWST24 (2) Expression (2) In step 312, the temperature change amounts DTWST21 and DTWST22 calculated in step 305 and step 311 determine the expression (3).

JTWST21> DTWST21, -DTWST22 (3) Expression If the expression (3) is established, the process proceeds to step 313, and if not, the process proceeds to step 314.

  In step 313, there is a difference between the amount of water temperature decrease when the thermostat opens or closes the valve closing set temperature, and the amount of change in cooling water temperature when the thermostat falls below the valve closing set temperature. Since it is considered to function normally, it is determined that the failure diagnosis at stage 2 is normal, and the failure diagnosis at stage 2 is terminated.

  In step 314, since it is considered that the thermostat has not been closed, it is determined that the failure is fixed in the open state (valve closing failure), and the failure diagnosis in stage 2 is terminated.

  FIG. 8 shows the transition of the cooling water temperature when the water pump, the radiator fan, and the thermostat in the above-described stage 3 are in a normal state, and the transition of the cooling water temperature when the thermostat is fixed in the valve-open state.

  The main features described above are listed below.

  1. The first feature has a failure determination function capable of determining a failure of the internal combustion engine cooling system based on a change in temperature of the cooling water caused by operating and stopping the water pump, the radiator fan, and the thermostat during operation of the internal combustion engine.

  According to the first feature, by investigating the temperature change of the cooling water, a complicated hardware configuration that makes stable diagnosis of a cooling system stable without being influenced by disturbances such as heat generated from the internal combustion engine or traveling wind This can be realized with a simple configuration without using.

  2. The second feature is that when the temperature of the cooling water detected when the water pump and the radiator fan are started after a predetermined time from the start of operation of the internal combustion engine is lower than the thermostat valve opening or valve closing set temperature. And a failure determination function for determining that the thermostat is in a valve-open state and cannot be closed.

  According to the second feature, by checking the temperature change of the cooling water, a stable diagnosis of the thermostat valve closing failure can be realized with a simple configuration without using a complicated hardware configuration.

  3. The third feature is that when the operation of the water pump and the radiator fan is instructed for a predetermined time width during the operation of the internal combustion engine and the temperature change amount of the cooling water detected in the predetermined time width is equal to or less than the predetermined value, It has a failure determination function for determining that the starter failure of the turbo pump or the radiator fan.

  According to the third feature, by checking the temperature change of the cooling water, stable diagnosis of a start failure of the water pump or the radiator fan can be realized with a simple configuration without using a complicated hardware configuration. .

  4). The fourth feature has a function of determining whether the start-up failure is either the water pump or the radiator fan or both the water pump and the radiator fan according to the temperature change amount.

  According to the fourth feature, by examining the temperature change of the cooling water, a stable diagnosis is complicated whether the start failure is either the water pump or the radiator fan, or both the water pump and the radiator fan. This can be realized with a simple configuration without using a hardware configuration.

  5). The fifth feature is that depending on the amount of temperature change, the cause of the start-up failure is due to the performance degradation of the water pump, the performance degradation of the radiator fan, or the performance degradation of the water pump and the radiator fan. And a function of discriminating between the two.

  According to the fifth feature, by examining the temperature change of the cooling water, the cause of the start failure is whether the performance of the water pump is deteriorated, the performance of the radiator fan is deteriorated, or the water pump and the radiator fan. This can be realized with a simple configuration without using a complicated hardware configuration for stable diagnosis.

  6). The sixth feature is that, when it is determined that the water pump or radiator fan has a start failure, is the cause of the start failure caused by a decrease in performance of the water pump or a decrease in performance of the radiator fan? And a function of prohibiting diagnosis for checking whether the performance of the water pump and the radiator fan is reduced.

  According to the sixth feature, when a start failure failure of the water pump or the radiator fan occurs, there is a case where the operation for determining the failure of the performance degradation of the water pump and the radiator fan can be normally performed. Therefore, by providing a function for prohibiting diagnosis, the burden of software processing related to diagnosis can be reduced.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various changes can be made in the design without departing from the content of the invention described in the claims. Is.

  In particular, in this failure diagnosis device, by appropriately changing the threshold value of the coolant temperature used for each failure determination, it is possible to determine the failure of the fixed start state and the failure of the fixed stop state described in the above embodiment. In addition, it is also possible to determine the state before the completely fixed state.

1 is an overall configuration diagram of an engine system including a failure diagnosis device for an internal combustion engine cooling system according to an embodiment. The internal block diagram of the control unit provided with the failure diagnosis apparatus of the cooling system shown in FIG. 2 is an overall control flowchart of the cooling system failure diagnosis apparatus shown in FIG. 1. The graph which showed transition of the cooling water temperature at the time of the operation | movement of the water pump of the failure diagnosis apparatus of a cooling system shown in FIG. 1, a radiator fan, and a thermostat, and a cooling system normal. 6 is a control flowchart showing failure diagnosis in stage 1; FIG. 5 is a graph showing the operation of the water pump, radiator fan, and thermostat shown in FIG. 6 is a control flowchart showing failure diagnosis in stage 2; FIG. 8 is a graph showing the operation of the water pump, radiator fan, and thermostat shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Air cleaner which removes dust etc. of the external air to inhale, 3 ... Intake duct through which clean air that has passed through the air cleaner passes, 4 ... Throttle throttle valve, throttle body constituting throttle opening sensor, 5 ... Measurement of intake air amount Air flow sensor, 6 ... throttle throttle valve for adjusting the intake air amount, 7 ... throttle opening sensor for measuring the throttle opening, 8 ... adjusting the air amount when the throttle throttle valve is fully closed, ISC (idle speed control valve) for controlling engine speed, 11a, 11b, 11c, 11d ... means bank (injector) for injecting fuel into the combustion chamber, 20 ... water jacket for an internal combustion engine into which cooling water is injected, 21: Radiator that releases heat of cooling water to the atmosphere, 22: Heat quantity of cooling water, Heater core, 23 ... thermostat that opens and closes at the set cooling water temperature, 24 ... electric water pump that circulates the cooling water, 25 ... cooling electric fan that promotes the heat radiation effect of the radiator, 26 ... cooling water temperature in the water jacket Cooling water temperature sensor to measure.

Claims (7)

A water pump for circulating cooling water for cooling a water-cooled internal combustion engine, a thermostat for opening and closing a cooling water channel flowing through the radiator, a radiator fan for promoting heat dissipation of the radiator, and the cooling In a failure diagnosis device for an internal combustion engine cooling system comprising a water temperature sensor for measuring the temperature of water,
A failure determination function capable of determining a failure of a cooling system of the internal combustion engine by a change in temperature of the cooling water caused by operating and stopping the water pump, the radiator fan, and the thermostat during operation of the internal combustion engine; Characteristic failure diagnosis device. The failure diagnosis apparatus according to claim 1,
When the temperature of the cooling water detected when the water pump and the radiator fan are started after a predetermined time from the start of the operation of the internal combustion engine is lower than the thermostat valve opening or valve closing set temperature A failure diagnosis device having a failure determination function for determining that the thermostat is restricted to an open state and cannot be closed. The failure diagnosis apparatus according to claim 1,
When the operation of the water pump and the radiator fan is instructed during a predetermined time period during the operation of the internal combustion engine, and the temperature change amount of the cooling water detected during the predetermined time period is less than a predetermined value, the water pump or the radiator A failure diagnosis device having a failure determination function for determining a fan start-up failure. The failure diagnosis apparatus according to claim 3,
A failure diagnosis apparatus having a function of determining whether the start-up failure is either the water pump or the radiator fan or both the water pump and the radiator fan according to the temperature change amount . The failure diagnosis apparatus according to claim 4,
Depending on the amount of temperature change, whether the cause of the start-up failure is due to the performance degradation of the water pump, the performance degradation of the radiator fan, or the performance degradation of the water pump and the radiator fan. A fault diagnosis apparatus having a function of discriminating. The failure diagnosis apparatus according to claim 4,
When it is determined that the water pump or the radiator fan has a start failure, the cause of the start failure is a decrease in the performance of the water pump, a decrease in the performance of the radiator fan, A failure diagnosis apparatus characterized by having a function of prohibiting diagnosis for checking whether the performance of a radiator fan is reduced. A water pump for circulating cooling water for cooling a water-cooled internal combustion engine, a thermostat for opening and closing a cooling water channel flowing through the radiator, a radiator fan for promoting heat dissipation of the radiator, and the cooling In a failure diagnosis method for an internal combustion engine cooling system comprising a water temperature sensor for measuring the temperature of water,
A failure determination function capable of determining a failure of the cooling system of the internal combustion engine based on a change in temperature of the cooling water caused by operating and stopping the water pump, the radiator fan, and the thermostat during operation of the internal combustion engine; Fault diagnosis method.

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