JP2008298059A - Cooling system abnormality diagnosis device and block heater determination device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent from incorrectly diagnosing abnormality/normality of a cooling system by difference in behavior of cooling water temperature dependent on execution of energization to a block heater during engine stopping. <P>SOLUTION: When operation of the engine 11 is stopped, the cooling water temperature detected by a cooling water temperature sensor 32 is stored in a backup RAM 45 as the cooling water temperature in engine stopping. At a time point when a predetermined time elapsed from the time of engine stopping, an ECU 41 is power on and is self-started to perform leak diagnosis of an evaporation-purge system and the cooling water temperature detected in the self-starting is stored as the cooling water temperature in self-starting in the backup RAM 45. Then, execution of energization to the block heater 34 is determined in engine starting by reading in a temperature difference between the cooling water temperature in engine stopping and the cooling water temperature in self-starting or the like from the backup RAM 45 and comparing it with a determination value and if energization to the block heater 34 is found to have been executed, abnormality diagnosis of the cooling system is prohibited. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cooling system abnormality diagnosis device for an internal combustion engine and a block heater having a function of energizing an external power supply to a block heater mounted on the internal combustion engine while the internal combustion engine is stopped in cold weather to keep the cooling water of the internal combustion engine warm. The invention relates to a determination device.

  As described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2002-30959), in a cold region, a block heater for preventing freezing is attached to a cylinder block of an engine (internal combustion engine), and the engine is stopped during cold. In addition, there is a type in which the block heater power cord is connected to a household power outlet and the block heater is energized to keep engine cooling water warm and prevent freezing.

Further, as described in Patent Document 2 (Japanese Patent No. 3538545), the cooling water temperature is estimated based on the engine operating state, and the estimated value of the cooling water temperature and the detected value of the cooling water temperature detected by the water temperature sensor are used. Some of them are compared with predetermined values, and radiator abnormality diagnosis is executed based on the comparison result.
JP 2002-30959 A Japanese Patent No. 3538545

  By the way, whether or not to keep the engine warm by connecting the plug of the power cord of the block heater to an external power outlet while the engine is stopped is left to the user's arbitrary judgment. Since the information on whether or not the block heater is energized is not given, the vehicle abnormality diagnosis device should perform the abnormality diagnosis of the radiator based on the behavior of the cooling water temperature after starting without knowing whether or not the block heater is energized. become.

  However, since the behavior of the cooling water temperature after start-up differs greatly depending on whether or not the block heater is energized while the engine is stopped, the influence of whether or not the block heater is energized is completely ignored as in the conventional case. When the abnormality diagnosis of the radiator is executed based on the behavior, the abnormality / normality of the radiator may be erroneously diagnosed due to the difference in the behavior of the cooling water temperature depending on whether the block heater is energized.

  Accordingly, an object of the present invention is to prevent a malfunction / normality of the cooling system from being erroneously diagnosed due to a difference in the behavior of the cooling water temperature depending on whether or not the block heater is energized while the internal combustion engine is stopped. Another object is to make it possible to accurately determine whether the block heater is energized.

  In order to achieve the former object, according to the first aspect of the present invention, the internal combustion engine cooling water is energized from an external power source to the anti-freezing block heater mounted on the internal combustion engine while the internal combustion engine is cold. In a cooling system abnormality diagnosis apparatus for an internal combustion engine that maintains heat and performs an abnormality diagnosis of the cooling system based on the behavior of the cooling water temperature during operation of the internal combustion engine, a block heater determination is made as to whether or not the block heater is energized while the internal combustion engine is stopped When the determination is made by the means and, as a result, it is determined that the block heater is energized, the abnormality diagnosis prevention means prohibits the abnormality diagnosis of the cooling system or corrects the abnormality diagnosis condition. In this configuration, when it is determined that the block heater is energized, the cooling system abnormality diagnosis is prohibited or the abnormality diagnosis condition is corrected. It is possible to prevent a malfunction / normality of the cooling system from being erroneously diagnosed due to the difference in behavior, and to improve the diagnostic accuracy and reliability of the abnormality diagnosis of the cooling system.

  In this case, if the block heater is not energized while the internal combustion engine is stopped, the method of determining whether or not the block heater is energized is the temperature difference between the cooling water temperature and the outside air temperature when the operation of the internal combustion engine is stopped, and the stop of the internal combustion engine. While the cooling water temperature decreases with time, if the block heater is energized while the internal combustion engine is stopped, the internal combustion engine stop time is reduced by utilizing the characteristic that the cooling water temperature decreases less due to heat generated by the block heater. The presence or absence of energization of the block heater may be determined using the coolant temperature, the outside air temperature (intake air temperature), or information correlated therewith.

  By the way, when the operation of the internal combustion engine is stopped before the warm-up of the internal combustion engine is completed, the temperature of the cooling water when the operation of the internal combustion engine is stopped is low and the temperature difference from the outside air temperature is small. The amount of decrease in the cooling water temperature is small, and it is difficult to distinguish from the case where the block heater is energized.

  Therefore, as in claim 2, when the cooling water temperature when the operation of the internal combustion engine is stopped is equal to or lower than a predetermined temperature, it is preferable to prohibit the determination of whether or not the block heater is energized. In this way, it is possible to prevent erroneous determination of whether or not the block heater is energized when the cooling water temperature when the operation of the internal combustion engine is stopped is low and the temperature difference from the outside air temperature is small.

  Further, when the present invention is applied to a system having cooling water temperature estimating means for estimating the cooling water temperature of the internal combustion engine based on the operating state of the internal combustion engine as in claim 3, the block heater determining means uses the block heater determining means. It is preferable to correct the estimated coolant temperature when it is determined that there is energization. In this way, it is possible to improve the estimation accuracy of the cooling water temperature by correcting the estimation error of the cooling water temperature due to the energization of the block heater.

  Also, a system equipped with a self-starting means for temporarily turning on and self-starting an ECU (electronic control unit) for leak diagnosis of an evaporative gas purge system after elapse of a predetermined time since the operation of the internal combustion engine is stopped In this case, the presence / absence of energization of the block heater may be determined using self-activation as in the fourth aspect.

  In a system in which the ECU is temporarily turned on and self-started for a leak diagnosis after a predetermined time has passed since the operation of the internal combustion engine was stopped, the stop time of the internal combustion engine from the stop of the operation of the internal combustion engine to the self-startup Since it is always constant, using this self-activation to determine whether the block heater is energized or not can prevent a decrease in determination accuracy due to a difference in the stop time of the internal combustion engine. There is an advantage that the presence / absence of energization can be accurately determined, and it is not necessary to adapt / evaluate the determination condition using the stop time of the internal combustion engine as a parameter, thereby facilitating the work of adapting / evaluating the determination condition.

Hereinafter, an embodiment embodying the best mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 for detecting the amount of intake air is provided downstream of the air cleaner 13. An intake air temperature sensor (not shown) for detecting the intake air temperature (outside air temperature) is provided. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 for introducing air into each cylinder of the engine 11, and a fuel injection valve 21 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 20 of each cylinder. Yes. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each ignition plug 22.

  On the other hand, a catalyst 24 such as a three-way catalyst for purifying CO, HC, NOx, etc. in the exhaust gas is installed in the exhaust pipe 23 (exhaust passage) of the engine 11. An exhaust gas sensor 25 for detecting air-fuel ratio or rich / lean is installed. A crank angle sensor 26 that outputs a pulse signal every time the crankshaft rotates a predetermined crank angle is attached to the engine 11, and the crank angle and the engine rotation speed are detected based on the output signal of the crank angle sensor 26. The

  A cooling water circulation circuit 28 that circulates the cooling water of the engine 11 is provided with a radiator 29 that dissipates heat of the cooling water, a thermostat valve 30 that controls a cooling water circulation flow rate to the radiator 29, and the like. A cooling water temperature sensor 32 that detects the temperature (cooling water temperature) of the cooling water flowing into the cooling water circulation circuit 27 from the engine 11 is installed in the vicinity of the cooling water outlet of the engine 11. A cooling fan 33 for forcibly cooling the cooling water is installed on the back side of the radiator 29.

  Further, a block heater 34 for preventing freezing is attached to the cylinder block of the engine 11. A power cord 35 is connected to the block heater 34. When the engine is stopped in cold weather, the user plugs the plug 36 of the power cord 35 of the block heater 34 into a household power outlet (not shown). And the block heater 34 is energized to keep the cooling water of the engine 11 warm and prevent freezing. And before starting the engine 11, a user removes the plug 36 of the power cord 35 from a household power outlet, and stores it in an appropriate place in the engine room.

  It should be noted that since it is not necessary to keep the cooling water by the block heater 34 when it is not cold, the power cord 35 of the block heater 34 remains stored in the engine room even when the engine is stopped. Is not energized.

  Outputs of various sensors such as the cooling water temperature sensor 32 described above are input to a control circuit (hereinafter referred to as “ECU”) 41. The power supply terminal of the ECU 41 is supplied with a power supply voltage Vb from an in-vehicle battery (not shown) via the main relay 42. The relay drive coil 42b that drives the relay contact 42a of the main relay 42 is connected to the main relay control terminal of the ECU 41. When the relay drive coil 42b is energized, the relay contact 42a is turned on, and the ECU 41 Etc. are supplied with a power supply voltage. Then, by turning off the energization to the relay drive coil 42b, the relay contact 42a is turned off, and the power supply to the ECU 41 and the like is turned off.

  An ON / OFF signal of an ignition switch (hereinafter referred to as “IG switch”) 43 is input to the IG switch terminal of the ECU 41. When the IG switch 43 is turned on, the main relay 42 is turned on and power supply to the ECU 41 and the like is started. When the IG switch 42 is turned off, the main relay 42 is turned off after processing for stopping the engine is performed. The power supply to the ECU 41 and the like is turned off.

  In addition, the ECU 41 has a built-in soak timer 44 that operates with a backup power source (not shown) as a power source. The soak timer 44 starts a time measuring operation after the engine is stopped (after the IG switch 43 is turned off), and measures an elapsed time after the engine is stopped. As described above, when the IG switch 43 is turned off, the main relay 42 is turned off and the power supply to the ECU 41 and the like is turned off. However, in order to perform a leak diagnosis of an evaporation purge system (not shown) while the engine is stopped. When the measurement time of the soak timer 44 (elapsed time after engine stop) reaches a predetermined time (for example, 5 hours), the backup power source of the ECU 41 is used as a power source and the drive circuit of the main relay control terminal of the ECU 41 is activated. Then, the main relay 42 is temporarily turned on, and the ECU 41 is powered on to self-activate. This function corresponds to the self-starting means in the claims, and the ECU 41 performs a leak diagnosis of the evaporation purge system at the time of self-starting, and the data such as the cooling water temperature detected by the cooling water temperature sensor 32 at the time of self-starting. It is used to determine whether or not the block heater 34 described later is energized.

  The ECU 41 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount and ignition of the fuel injection valve 21 according to the engine operating state. The ignition timing of the plug 22 is controlled.

  Further, the ECU 41 determines whether or not the block heater 34 is energized while the engine is stopped by executing each routine shown in FIGS. 2 to 4 described later. As a result, it is determined that the block heater 34 is energized. In this case, the cooling system abnormality diagnosis by the cooling system abnormality diagnosis routine of FIG. When it is determined that the block heater 34 is energized, the coolant temperature estimated by the coolant temperature estimation routine of FIG. 5 described later is corrected.

  Here, as shown in FIG. 7, if the block heater 34 is not energized while the engine is stopped, the method for determining whether or not the block heater 34 is energized while the engine is stopped is the cooling water temperature and the external temperature when the operation of the engine 11 is stopped. While the cooling water temperature decreases according to the temperature difference from the air temperature and the engine stop time, when the block heater 34 is energized while the engine is stopped, the cooling water temperature is prevented from decreasing due to the heat generated by the block heater 34. Then, the presence or absence of energization of the block heater 34 may be determined using the engine stop time, the cooling water temperature, the outside air temperature (intake air temperature), or information correlated therewith.

  Specifically, (1) Blocking using the relationship between the amount of change in cooling water temperature while the engine is stopped (temperature difference between the cooling water temperature when the engine 11 is stopped and the cooling water temperature when starting) and the engine stop time It is determined whether or not the heater 34 is energized, and (2) whether or not the block heater 34 is energized is determined using the relationship between the temperature difference between the cooling water temperature at the start and the outside air temperature (intake air temperature) and the engine stop time. (3) The cooling water temperature at the start is estimated based on the cooling water temperature when the operation of the engine 11 is stopped, the outside air temperature (intake air temperature), and the engine stop time, and the estimated cooling water temperature is used as the cooling water temperature sensor. It can be considered that the block heater 34 is energized in comparison with the cooling water temperature detection value detected in 32, or that two or more of these three determination methods (1) to (3) are combined. It is done.

  By the way, when the operation of the engine 11 is stopped before the warm-up of the engine 11 is completed, the cooling water temperature when the operation of the engine 11 is stopped is low and the temperature difference from the outside air temperature is small. The amount of decrease in the water temperature is reduced, making it difficult to distinguish from the case where the block heater 34 is energized.

  Therefore, in this embodiment, when the coolant temperature when the operation of the engine 11 is stopped is equal to or lower than a predetermined temperature (for example, 60 ° C. or lower), the determination as to whether the block heater 34 is energized is prohibited. In this way, it is possible to prevent erroneous determination of whether the block heater 34 is energized or not when the coolant temperature when the operation of the engine 11 is stopped is low and the temperature difference from the outside air temperature is small.

  Further, for example, when determining whether or not the block heater 34 is energized using the change amount of the cooling water temperature while the engine is stopped or the temperature difference between the cooling water temperature and the outside air temperature (intake air temperature) at the time of starting, The amount of change in cooling water temperature and the temperature difference between the cooling water temperature and the outside air temperature at start-up change depending on the engine stop time, so it is necessary to set a judgment condition with the engine stop time as a parameter. There is also a concern that the above-described work becomes troublesome and the determination accuracy is lowered due to a difference in engine stop time.

  Therefore, in this embodiment, attention is paid to the fact that the ECU 41 is temporarily turned on and self-started for a leak diagnosis after a predetermined time (for example, after 5 hours) has elapsed since the operation of the engine 11 is stopped. The self-activation is used to determine whether the block heater 34 is energized. Since the engine stop time from the stop of operation of the engine 11 to the self-start is always a fixed time (for example, 5 hours), if the self-start is used to determine whether the block heater 34 is energized, the engine It is possible to avoid a decrease in determination accuracy due to the difference in stop time, and there is no need to adapt / evaluate the determination condition using the engine stop time as a parameter, which makes it easier to adapt and evaluate the determination condition. .

  In this embodiment, the coolant temperature detected by the coolant temperature sensor 32 at the time of self-activation is stored in the backup RAM 45 of the ECU 41 (a rewritable storage means that retains stored data even when the power of the ECU 41 is turned off). Whether the block heater 34 is energized or not is determined using the cooling water temperature at the time of self-starting read from the backup RAM 45 of the ECU 41 when the power is turned on (at the next start-up). It is also possible to determine whether or not the current is energized and store the determination result in the backup RAM 45.

  Hereinafter, the processing content of each routine shown in FIGS. 2 to 6 executed by the ECU 41 will be described. In the following description, “when the engine is stopped” means “when the operation of the engine 11 is stopped”.

[Cooling water temperature detection routine when the engine is stopped]
2 is started at a predetermined cycle (for example, 32 msec cycle) while the ECU 41 is powered on. When this routine is started, it is first determined in step 101 whether or not the engine is stopped (when the IG switch 43 is switched from ON to OFF). finish.

Thereafter, when the IG switch 43 is switched from ON to OFF and the operation of the engine 11 is stopped, “Yes” is determined in Step 101, the process proceeds to Step 102 and detected by the cooling water temperature sensor 32 when the engine is stopped. The coolant temperature thw is stored in the backup RAM 45 as the engine stop coolant temperature thw0, and this routine is terminated.
[Self-starting cooling water temperature detection routine]
The self-starting cooling water temperature detection routine of FIG. 3 is started at a predetermined cycle (for example, 32 msec cycle) while the ECU 41 is powered on. When this routine is started, first, at step 201, it is determined whether or not it is self-starting (after 5 hours have passed since the operation of the engine 11 was stopped). Exit.

  After that, when the self-start is started, “Yes” is determined in step 201, and the process proceeds to step 202, and is detected by the cooling water temperature sensor 32 at the time of self-start (after 5 hours have passed since the operation of the engine 11 is stopped). The cooling water temperature thw is stored in the backup RAM 45 as the self-starting cooling water temperature thw1, and this routine is terminated.

[Block heater judgment routine]
The block heater determination routine of FIG. 4 is started at a predetermined cycle (for example, 32 msec cycle) while the ECU 41 is powered on, and serves as a block heater determination means in the claims. When this routine is started, it is first determined at step 301 whether or not the engine is starting (when the IG switch 43 is switched from OFF to ON). finish.

  On the other hand, if it is determined in step 301 that the engine is starting, the process proceeds to step 302, where it is determined whether the self-start has been executed based on whether the engine stop time is 5 hours or longer. If it is determined that the engine stop time is less than 5 hours (before self-starting execution), this routine is terminated as it is.

  On the other hand, if it is determined in the above step 302 that the engine stop time is 5 hours or longer (already self-started), the process proceeds to step 303, and the engine stop-time cooling water temperature thw0 read from the backup RAM 45 is a predetermined value (eg 60 ° C.). It is determined whether it is above. As a result, if it is determined that the cooling water temperature thw0 when the engine is stopped is equal to or less than a predetermined value, it is determined that there is a possibility of erroneous determination of whether the block heater 34 is energized, and whether the block heater 34 is energized is not determined. Then, this routine is finished as it is.

  If it is determined in step 303 that the engine stop cooling water temperature thw0 is equal to or greater than a predetermined value, the process proceeds to step 304, and the temperature difference (thw0) between the engine stop cooling water temperature thw0 read from the backup RAM 45 and the self startup cooling water temperature thw1. -Thw1), that is, it is determined whether or not the cooling water temperature decrease amount (thw0-thw1) during the engine stop from the engine stop to the self start is equal to or less than the determination value. As a result, if it is determined that the cooling water temperature decrease amount (thw0-thw1) while the engine is stopped is equal to or less than the determination value, the process proceeds to step 305, where it is determined that the block heater 34 is energized, and the cooling water temperature decrease when the engine is stopped. If it is determined that the amount (thw0-thw1) is greater than or equal to the determination value, it is determined that the block heater 34 is not energized, and this routine is terminated.

  As described above, the method for determining whether or not the block heater 34 is energized may be changed as appropriate. For example, in step 304 above, the temperature difference (thw1) between the self-starting cooling water temperature thw1 and the outside air temperature (intake air temperature) tha. It is determined whether or not −tha) is equal to or smaller than a determination value. If the temperature difference (thw1−tha) is equal to or larger than the determination value, it may be determined that the block heater 34 is energized. In this case, as the data of the outside air temperature (intake air temperature) tha, the outside air temperature (intake air temperature) detected by the outside air temperature sensor (or the intake air temperature sensor) at the time of self-starting may be stored in the backup RAM 45.

  In addition, the temperature difference (thw1-thw) between the cooling water temperature thw1 at the time of self-starting and the cooling water temperature thw at the time of starting the engine, or the temperature difference (thw0) between the cooling water temperature thw0 at the time of stopping the engine and the cooling water temperature thw at the time of starting the engine. -Thw) may be used.

[Cooling water temperature estimation routine]
The cooling water temperature estimation routine of FIG. 5 is started at a predetermined period (for example, 32 msec period) while the ECU 41 is turned on, and serves as a cooling water temperature estimation means in the claims. When this routine is started, it is first determined in step 401 whether or not the engine is starting (when the IG switch 43 is switched from OFF to ON). If the engine is starting, the process proceeds to step 402. Based on the processing result of the block heater determination routine of FIG. 4, it is determined whether or not the block heater 34 is energized. If it is determined that the block heater 34 is not energized, the process proceeds to step 404 to estimate. The coolant temperature thwst at the time of engine start detected by the coolant temperature sensor 32 is set to the coolant temperature initial value thwe0.
thwe0 = thwst

On the other hand, if it is determined that the block heater 34 is energized, the process proceeds to step 403, and a value obtained by subtracting a predetermined water temperature correction value k from the cooling water temperature thwst at the start of the engine is set as the estimated cooling water temperature initial value thwe0. To do.
thwe0 = thwst-k
If it is determined in step 401 that the engine is not started, the processes in steps 402 to 404 are omitted.

  Thereafter, the process proceeds to step 405, where the estimated coolant temperature thwe is calculated using the estimated coolant temperature initial value thwe0 and the thermal load parameter contributing to the increase of the coolant temperature among the engine operation parameters. At this time, the thermal load parameter may be obtained from the engine load integrated value and the integrated cooling loss value (cooling loss value due to the heater for indoor heating or traveling wind).

[Abnormal diagnosis routine]
The cooling system abnormality diagnosis routine of FIG. 6 is started at a predetermined cycle (for example, 32 msec cycle) while the ECU 41 is powered on. When this routine is started, first, at step 501, it is determined whether or not the block heater 34 is energized based on the processing result of the block heater determination routine of FIG. If it is determined, the routine is terminated without performing the subsequent abnormality diagnosis process. The processing in step 501 serves as a false diagnosis prevention means in the claims.

  If it is determined in step 501 that the block heater 34 is not energized, the process proceeds to step 502, where it is determined whether or not the cooling system abnormality diagnosis execution condition is satisfied, for example, (1) whether the engine is warming up or not. (2) The determination is made based on whether or not the abnormality diagnosis result of the intake air temperature (outside air temperature) sensor or the like is normal. If the cooling system abnormality diagnosis execution condition is not satisfied, this routine is ended as it is.

  On the other hand, if it is determined in step 502 that the cooling system abnormality diagnosis execution condition is satisfied, the process proceeds to step 503, where the actual cooling water temperature thw detected by the cooling water temperature sensor 32 and the cooling water temperature estimation routine of FIG. Depending on whether or not an error from the calculated estimated cooling water temperature thwe (absolute value of the difference between the actual cooling water temperature Thw and the estimated cooling water temperature thwe) is larger than the abnormality determination value, the cooling system (thermostat valve 30, cooling water temperature sensor 32, The presence or absence of abnormality in the radiator 29 or the like is determined. If it is determined in step 503 that the error between the actual cooling water temperature Thw and the estimated cooling water temperature Te is equal to or less than the abnormality determination value, the process proceeds to step 504, where it is determined that the cooling system is normal, and this routine ends.

  On the other hand, if it is determined in step 503 that the error between the actual cooling water temperature Thw and the estimated cooling water temperature Te is larger than the abnormality determination value, the process proceeds to step 504, where the cooling system is determined to be abnormal and the operation is started. The warning lamp 46 provided on the instrument panel of the passenger seat is turned on or displayed on the warning display unit to warn the driver, and the abnormality information (abnormal code) is stored in the backup RAM 45 of the ECU 41, End the routine.

A control example of the present embodiment described above will be described with reference to the time chart of FIG.
At the time t1 when the IG switch 43 is turned off, the operation of the engine 11 is stopped, and the coolant temperature thw detected by the coolant temperature sensor 32 when the engine is stopped is stored in the backup RAM 45 as the coolant temperature thw0 when the engine is stopped. The relay 42 is turned off to turn off the power supply to the ECU 41 and the like.

  When the block heater 34 is not energized while the engine is stopped, the cooling water temperature decreases according to the temperature difference between the cooling water temperature at the time t1 when the engine is stopped and the outside air temperature (intake air temperature) and the engine stop time. When the block heater 34 is energized, the cooling water temperature decreases less due to the heat generated by the block heater 34.

  Thereafter, at a time t2 when a predetermined time (for example, 5 hours) has elapsed from the time t1 when the engine is stopped, the main relay 42 is turned on and the ECU 41 is powered on to self-activate, and the leak diagnosis of the evaporation purge system is performed. The cooling water temperature thw detected by the cooling water temperature sensor 32 at the time of self activation t2 is stored in the backup RAM 45 as the cooling water temperature thw1 at the time of self activation. At time t3 when the leak diagnosis is finished, the main relay 42 is turned off to turn off the power supply to the ECU 41 and the like.

  Thereafter, at the time t4 when the IG switch 43 is turned on, the main relay 42 is turned on, the ECU 41 is powered on, and the engine 11 is started. And the temperature difference (thw0-thw1) between the cooling water temperature thw0 at the time of engine stop and the cooling water temperature thw1 at the time of self-starting read from the backup RAM 45, or the temperature difference between the cooling water temperature thw1 at the time of self-starting and the outside air temperature (intake air temperature) tha. (Thw1-tha) or the like is compared with a determination value to determine whether the block heater 34 is energized. As a result, if it is determined that the block heater 34 is energized, the cooling system abnormality diagnosis is prohibited. At this time, instead of prohibiting the abnormality diagnosis of the cooling system, the abnormality diagnosis conditions (abnormality determination value, cooling water temperature, etc.) may be corrected.

  According to the present embodiment described above, the cooling system abnormality diagnosis is prohibited (or the abnormality diagnosis condition is corrected) when it is determined that the block heater 34 is energized. Therefore, it is possible to prevent the abnormality / normality of the cooling system from being erroneously diagnosed by the difference in the behavior of the cooling water temperature depending on whether the electric current is supplied or not, and the diagnostic accuracy and reliability of the abnormality diagnosis of the cooling system can be improved.

  In addition, in this embodiment, when the cooling water temperature when the operation of the engine 11 is stopped is equal to or lower than the predetermined temperature, the determination of whether or not the block heater 34 is energized is prohibited, so that the cooling when the operation of the engine 11 is stopped is prohibited. When the water temperature is low and the temperature difference from the outside air temperature is small, it is possible to prevent erroneous determination of whether the block heater 34 is energized.

  Further, in this embodiment, when it is determined that the block heater 34 is energized, the estimated coolant temperature is corrected. Therefore, the estimated coolant temperature error due to the energization of the block heater 34 is corrected to estimate the coolant temperature. Accuracy can be improved.

  In this embodiment, self-start for leak diagnosis or the like is used to determine whether the block heater 34 is energized. However, the present invention can be applied to a system that does not perform self-start. Needless to say.

  In addition, this invention is not limited to the said Example, For example, you may change suitably the determination method of the presence or absence of electricity supply of the block heater 34, the abnormality diagnosis method of a cooling system, and the estimation method of cooling water temperature, for example.

It is a schematic block diagram of the whole engine control system in one Example of this invention. It is a flowchart which shows the flow of a process of the cooling water temperature detection routine at the time of an engine stop. It is a flowchart which shows the flow of a process of the cooling water temperature detection routine at the time of self starting. It is a flowchart which shows the flow of a process of a block heater determination routine. It is a flowchart which shows the flow of a process of a cooling water temperature estimation routine. It is a flowchart which shows the flow of a process of a cooling system abnormality diagnosis routine. It is a time chart explaining the example of control of one example of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 28 ... Cooling water circulation circuit, 29 ... Radiator, 30 ... Thermostat valve, 32 ... Cooling water temperature sensor, 34 ... Block heater, 35 ... Power cord, 36 ... Plug, 41 ... ECU (block heater judgment) Means, misdiagnosis prevention means, cooling water temperature estimation means, self-starting means), 42 ... main relay, 43 ... ignition switch (IG switch), 44 ... soak timer, 45 ... backup RAM, 46 ... warning lamp

Claims (4)

While the internal combustion engine is cold, the block heater installed in the internal combustion engine is energized from an external power source to keep the cooling water of the internal combustion engine warm, and the cooling system abnormality diagnosis is performed based on the behavior of the cooling water temperature during operation of the internal combustion engine In the cooling system abnormality diagnosis device for an internal combustion engine that executes
Block heater determination means for determining whether or not the block heater is energized while the internal combustion engine is stopped;
An internal combustion engine comprising: an erroneous diagnosis preventing means for prohibiting abnormality diagnosis of the cooling system or correcting an abnormality diagnosis condition when the block heater determining means determines that the block heater is energized. Cooling system abnormality diagnosis device.   2. The internal combustion engine according to claim 1, wherein the block heater determination unit includes a unit that prohibits determination of whether the block heater is energized or not when a coolant temperature when the operation of the internal combustion engine is stopped is equal to or lower than a predetermined temperature. Engine cooling system abnormality diagnosis device. A cooling water temperature estimating means for estimating the cooling water temperature of the internal combustion engine based on the operating state of the internal combustion engine;
3. The internal combustion engine according to claim 1, wherein the cooling water temperature estimating means includes means for correcting an estimated value of the cooling water temperature when the block heater determining means determines that the block heater is energized. 4. Cooling system abnormality diagnosis device. While the internal combustion engine is cold, the block heater mounted on the internal combustion engine is energized from an external power source to keep the cooling water of the internal combustion engine warm, and whether or not the block heater is energized while the internal combustion engine is stopped is determined by at least the cooling water temperature and the internal combustion engine. In a block heater determination device for an internal combustion engine comprising block heater determination means for determining based on the engine stop time,
Self-starting means for temporarily turning on and self-starting the block heater determination means after a predetermined time has elapsed since the operation of the internal combustion engine was stopped,
The block heater determination device for an internal combustion engine, wherein the block heater determination means determines whether or not the block heater is energized using the self-activation.

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