JP2004124798A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent overheat of an engine if failure occurs in a flow rate control valve for controlling the flow rate of cooling water flowed by bypassing a radiator. <P>SOLUTION: The presence of failure in the flow rate control valve 19 is diagnosed. When failure diagnosis detects the abnormality, then failure level is determined. If the failure level is a level 1 (the level in which the possibility of overheat is high), the heating value of the engine 11 is substantially reduced by carrying out throttle opening limit control for controlling the throttle opening at a throttle opening limit value for the level 1 and a cylinder operation control. If the abnormality level is a level 2 (the level in which the possibility of overheat is relatively low), the heating value of the engine 11 is reduced by carrying out only the throttle opening limit control for controlling the throttle opening at the throttle opening limit value for the level 2. If the failure level is a level 3 (the level in which the possibility of overheat is few), reduction control of the heating value is not carried out. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for an internal combustion engine that controls the flow rate of cooling water flowing by bypassing a radiator by a flow control valve to control the temperature of cooling water.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in a cooling system for an internal combustion engine (engine) mounted on a vehicle, for example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2000-45773) has been proposed for the purpose of early warming-up and reduction of friction loss from the viewpoint of improving fuel efficiency. As described in Japanese Patent Application Laid-Open Publication No. H10-163, a bypass flow path through which the cooling water bypasses the radiator is provided, and a flow rate of the cooling water flowing through the bypass flow path (bypass flow rate) and a flow rate of the cooling water flowing through the radiator (radiator) By providing a flow rate adjustment valve that can adjust the flow rate) and controlling the flow rate adjustment valve to adjust the flow rate ratio between the bypass flow rate and the radiator flow rate so that the cooling water temperature detected by the water temperature sensor matches the target cooling water temperature. A new cooling system for controlling the cooling water temperature with high accuracy has been developed.
[0003]
[Patent Document 1]
JP 2000-45773 A (page 2 etc.)
[0004]
[Problems to be solved by the invention]
However, in the cooling system equipped with the above-described flow control valve, the flow control valve does not operate normally due to foreign matter entering the flow control valve or a failure of its drive circuit, and the radiator flow rate is higher than normal. When an abnormal condition occurs, the amount of heat dissipated by the radiator decreases and the temperature of the cooling water flowing into the engine becomes higher than normal, so the engine cooling capacity of the cooling water decreases and the engine overheats. Could be done.
[0005]
The present invention has been made in view of such circumstances, and accordingly, an object of the present invention is to provide a control device for an internal combustion engine that can prevent overheating of the internal combustion engine due to an abnormality in a flow control valve. is there.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a control apparatus for an internal combustion engine according to claim 1 of the present invention diagnoses the presence or absence of an abnormality in a flow control valve by abnormality diagnosis means. The control for reducing the heat value of the engine (hereinafter referred to as “heat value reduction control”) is executed by the heat value reduction control means. In this way, even if the temperature of the cooling water flowing into the internal combustion engine rises due to an abnormality of the flow control valve and the cooling capacity of the internal combustion engine decreases, the calorific value of the internal combustion engine can be reduced by the calorific value reduction control. As a result, an increase in the engine temperature can be suppressed, and overheating of the internal combustion engine can be prevented.
[0007]
In this case, the overheating prevention effect can be enhanced as the calorific value of the internal combustion engine is reduced by the calorific value reduction control. However, in general, the control for reducing the calorific value of the internal combustion engine (mainly the calorific value of combustion) is performed by the internal combustion engine. Since it acts in the direction of lowering the output, the lower the calorific value of the internal combustion engine, the lower the output of the internal combustion engine and the lower the driving performance.
[0008]
In consideration of such circumstances, when it is diagnosed that there is an abnormality in the flow control valve, the degree of abnormality at that time is determined by the abnormality degree determining means, and the abnormality is determined according to the determined degree of abnormality. It is preferable to set a control item and / or a control amount to be subjected to the heat generation amount reduction control. When the flow control valve is abnormal, the amount of reduction in the amount of heat generated by the internal combustion engine required to prevent overheating varies depending on the degree of the abnormality at that time (for example, the degree of increase in the actual cooling water temperature with respect to the target cooling water temperature). By setting the control items and the control amount of the heat generation amount reduction control according to the degree of the abnormality, it is possible to appropriately adjust the reduction amount of the heat generation amount of the internal combustion engine by the heat generation amount reduction control according to the degree of the abnormality, The calorific value of the internal combustion engine can be reduced by an amount necessary to prevent overheating. As a result, it is possible to avoid a situation in which the calorific value of the internal combustion engine is reduced more than necessary during the calorific value reduction control, and it is possible to minimize a decrease in the operating performance of the internal combustion engine due to the calorific value reduction control.
[0009]
In addition, even when it is diagnosed that there is an abnormality in the flow control valve, for example, when the radiator flow rate is higher than normal, or when the radiator flow rate is slightly lower than normal, However, since the temperature of the cooling water flowing into the internal combustion engine does not rise, or even if it rises, the rising width is small, so that the cooling capacity of the internal combustion engine by the cooling water hardly decreases. In such a case, even if the heat generation amount reduction control is not performed, there is almost no possibility of overheating.
[0010]
Therefore, even when it is diagnosed that there is an abnormality in the flow control valve, if the degree of the abnormality is equal to or less than a predetermined level, the heat generation amount reduction control may not be performed. In this way, even if an abnormality occurs in the flow control valve, if the degree of the abnormality is at a level at which there is almost no possibility of overheating, the heat generation amount reduction control need not be performed, and the heat generation amount can be reduced. It is possible to avoid a decrease in the operating performance of the internal combustion engine due to the control.
[0011]
As a specific method of the calorific value reduction control, the throttle opening restriction, fuel cut, stratified lean combustion, reduced cylinder operation, control of the variable valve mechanism on the intake side and / or the exhaust side may be mentioned. It is preferable to execute the heat generation amount reduction control by at least one of the amount changes.
[0012]
For example, if the throttle opening is limited, the amount of air to be charged into each cylinder can be limited to reduce the amount of combustion heat in each cylinder, thereby reducing the amount of heat generated by the internal combustion engine. Further, if the fuel cut is executed, the amount of heat of combustion and the amount of heat generated by the internal combustion engine can be reduced accordingly. In stratified lean combustion, by burning lean air-fuel mixture, the amount of heat of combustion in each cylinder can be reduced, and the amount of heat generated by the internal combustion engine can be reduced. Further, in the reduced cylinder operation, the fuel injection to some of the cylinders is suspended, so that the calorific value of the combustion can be reduced by the amount of the suspended cylinders, and the calorific value of the internal combustion engine can be reduced. In addition, if the control amounts (valve timing, valve lift amount, etc.) of the variable valve mechanisms on the intake side and / or the exhaust side are changed in a direction in which the amount of air charged to each cylinder decreases, the throttle opening is limited. Similarly, the calorific value and the calorific value of the internal combustion engine can be reduced.
[0013]
As a method of diagnosing the abnormality of the flow control valve, for example, in the case of a system for controlling the flow control valve so that the cooling water temperature detected by the water temperature detecting means matches the target cooling water temperature, It is preferable to compare the cooling water temperature detected by the water temperature detecting means with the target cooling water temperature during the execution of the control to diagnose the presence or absence of an abnormality in the flow rate control valve. With this configuration, it is possible to accurately diagnose whether or not the flow rate control valve is abnormal.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, a schematic configuration of the entire cooling system will be described with reference to FIG. An outlet of a cooling water passage (water jacket) of an engine 11 which is an internal combustion engine is connected to an inlet of a radiator 12 by a cooling water circulation pipe 13, and an outlet of the radiator 12 and an inlet of a cooling water passage of the engine 11 are connected to a cooling water circulation pipe 14. Connected by An electric water pump 16 driven by a motor 15 is provided in the middle of the cooling water circulation pipe 14. Thereby, a cooling water circulation circuit 17 in which the cooling water circulates in a route of the cooling water passage of the engine 11 → the cooling water circulation pipe 13 → the radiator 12 → the cooling water circulation pipe 14 (the electric water pump 16) → the cooling water passage of the engine 11 is constituted. Have been.
[0015]
The cooling water circulation circuit 17 is provided with a bypass flow path 18 in parallel with the radiator 12, and both ends of the bypass flow path 18 are connected in the middle of the cooling water circulation pipes 13 and 14. A flow control valve 19 is provided at the junction of the bypass flow passage 18 and the cooling water circulation pipe 14. The flow rate adjusting valve 19 rotates a rotary valve (not shown) by an actuator 20 such as a motor, so that the flow rate (bypass flow rate) Vb of the cooling water flowing through the bypass flow path 18 and the cooling flow rate flowing through the radiator 12 are reduced. The flow rate of the water flow rate (radiator flow rate) Vr can be adjusted. The rotary valve of the flow rate adjusting valve 19 is biased by a biasing means such as a return spring to a rotational position at which the radiator flow rate Vr is maximized (a rotational position at which the bypass flow rate Vb is minimized) or in the vicinity thereof.
[0016]
A first water temperature sensor 21 (water temperature detecting means) for detecting the temperature (pump water temperature) Tp of the cooling water flowing into the electric water pump 16 is provided upstream of the electric water pump 16 in the cooling water circulation pipe 14. ) Is provided, and a second water temperature sensor 22 (water temperature detecting means) for detecting the temperature (bypass water temperature) Tb of the cooling water flowing through the bypass flow path 18 is provided in the bypass flow path 18. A third water temperature sensor 23 (water temperature detection means) for detecting the temperature (radiator water temperature) Tr 2 of the cooling water flowing out of the radiator 12 is provided upstream of the flow rate adjusting valve 19 in the cooling water circulation pipe 14. ing. Note that an electric cooling fan 25 driven by a motor 24 is arranged near the radiator 12.
[0017]
On the other hand, a throttle valve 27 whose opening is adjusted by a DC motor or the like is provided in an intake pipe 26 of the engine 11, and an intake pipe pressure sensor 28 for detecting an intake pipe pressure is provided downstream of the throttle valve 27. Have been. The cylinder block of the engine 11 is provided with a crank angle sensor 29 that outputs a pulse signal every time the crankshaft of the engine 11 rotates at a constant crank angle (for example, 30 ° C. A). The crank angle and the engine speed are detected based on the output signal of the crank angle sensor 29.
[0018]
The outputs of the various sensors described above are input to an engine control circuit (hereinafter referred to as “ECU”) 30. The ECU 30 is mainly composed of a microcomputer, and executes various engine control programs stored in a ROM (storage medium) of the microcomputer to execute fuel injection of a fuel injection valve (not shown) according to an engine operating state. The amount and the ignition timing of a spark plug (not shown) are controlled.
[0019]
In addition, the ECU 30 executes a water temperature control routine (not shown) to function as a water temperature control unit, calculate a target cooling water temperature Ttg in accordance with an engine operating state, and calculate an actual cooling water temperature (detected by the water temperature sensor 21). The flow control valve 19 is controlled so that the pump water temperature Tp matches the target cooling water temperature Ttg. At this time, the ECU 30 calculates the actual flow ratio R of the radiator flow rate Vr and the bypass flow rate Vb based on the pump water temperature Tp, the bypass water temperature Tb, and the radiator water temperature Tr, and also sets the target cooling water temperature Ttg, the bypass water temperature Tb, and the radiator water temperature Tr. The target flow ratio Rtg of the radiator flow rate Vr and the bypass flow rate Vb is calculated on the basis of the above, and the change amount of the flow control valve 19 is calculated based on the difference between the actual flow rate R and the target flow rate Rtg.
[0020]
Further, the ECU 30 executes fail-safe control of the flow rate adjustment valve 19 by executing each routine shown in FIGS. To explain the outline of the fail-safe control, first, it is diagnosed whether the flow regulating valve 19 is abnormal based on the temperature difference between the actual cooling water temperature Tp detected by the water temperature sensor 21 and the target cooling water temperature Ttg. Then, when it is diagnosed that the flow control valve 19 is abnormal, it is determined which of the levels 1 to 3 is the abnormal level (degree of abnormality) at that time.
[0021]
Here, at the level 1, the temperature difference between the actual cooling water temperature Tp and the target cooling water temperature Ttg is larger than the first level determination value K1, and if the normal water temperature control is continued as it is, the engine 11 may overheat. High level.
[0022]
In the level 2, the temperature difference between the actual cooling water temperature Tp and the target cooling water temperature Ttg is equal to or less than the first level determination value K1, but is larger than the second level determination value K2 (where K2 <K1). However, if normal water temperature control is continued as it is, there is a relatively low possibility that the engine 11 will overheat.
[0023]
On the other hand, at level 3, when the temperature difference between the actual cooling water temperature Tp and the target cooling water temperature Ttg is equal to or less than the second level determination value K2, the engine 11 may overheat even if normal water temperature control is continued. It is a level with little sex.
[0024]
When it is determined that the abnormal level is level 1 (a level at which the engine 11 is likely to overheat), both the throttle opening restriction control and the reduced cylinder operation control are executed as the heat generation amount reduction control. . In the throttle opening limit control, the throttle opening is limited by a throttle opening limit value THRMX = f1 for level 1, so that the amount of air to be charged into each cylinder is greatly limited to reduce the amount of combustion heat, and the engine 11 Reduce heat generation. In the reduced-cylinder operation control, fuel injection to some of the cylinders is stopped, and the amount of combustion heat is reduced by the number of the stopped cylinders, thereby reducing the heat generation of the engine 11.
[0025]
If it is determined that the abnormal level is level 2 (the level at which the engine 11 is unlikely to overheat), only the throttle opening limit control is executed as the heat generation amount reduction control, and the throttle opening is performed. By limiting the degree by the throttle opening limit value THRMX = f2 (where f2> f1) for the level 2, the amount of air to be charged into each cylinder is limited to reduce the amount of combustion heat, thereby reducing the amount of heat generated by the engine 11. .
[0026]
On the other hand, when it is determined that the abnormal level is level 3 (a level at which the engine 11 is unlikely to overheat), the same control as in the normal state is executed without performing the heat generation amount reduction control.
Hereinafter, the processing contents of each routine for the fail-safe control of the flow control valve 19 shown in FIGS. 2 to 4 which are executed by the ECU 30 will be described.
[0027]
[Fail-safe control of flow control valve]
The fail-safe control base routine of the flow control valve shown in FIG. 2 is executed at a predetermined cycle after an ignition switch (not shown) is turned on. When this routine is started, first, in step 101, input processing is executed to read the output of various sensors and the like, and then the process proceeds to step 102, where the target throttle opening THR0 is calculated based on the accelerator opening and the like. .
[0028]
Thereafter, the routine proceeds to step 103, where the abnormality diagnosis and abnormality level determination routine shown in FIG. 3 described later are executed to diagnose the presence or absence of the abnormality of the flow control valve 19 and to diagnose the presence of the abnormality of the flow control valve 19. Then, it is determined which of the levels 1 to 3 is the abnormal level at that time (the degree of increase of the actual cooling water temperature Tp with respect to the target cooling water temperature Ttg).
[0029]
Thereafter, the process proceeds to step 104, where it is determined whether the abnormal level is level 1 or level 2. If the abnormal level is determined to be level 1 or level 2, the process proceeds to step 105, where the abnormal level is determined. Is determined to be level 1 or not.
[0030]
If it is determined in step 105 that the abnormal level is level 1 (the level at which the engine 11 is likely to overheat), the process proceeds to step 106, where the map of the throttle opening limit value f1 for level 1 is set. To calculate a throttle opening limit f1 (Ne) corresponding to the current engine rotation speed Ne, and set this value as the throttle opening limit THRMX.
THRMX = f1 (Ne)
[0031]
The map of the throttle opening limit f1 for level 1 is set such that the throttle opening limit f1 for level 1 is smaller than the throttle opening limit f2 for level 2. ing.
Thereafter, the routine proceeds to step 107, in which the reduced-cylinder operation control is executed, fuel injection to some cylinders is stopped, and the engine 11 is operated in the remaining cylinders.
[0032]
Thereafter, the routine proceeds to step 109, where the target throttle opening degree THR0 calculated in step 102 is compared with the throttle opening limit value THRMX = f1 (Ne) for level 1 calculated in step 106, and the smaller one is compared. The final target throttle opening THR is set.
[0033]
According to the above processing, when the abnormal level is level 1, the throttle opening is limited (guard processing) by the throttle opening limit value THRMX = f1 (Ne) for the level 1, whereby the charged air amount of each cylinder is set. Is reduced to reduce the amount of combustion heat of each cylinder, and further, the amount of combustion heat is reduced by the amount of the stopped cylinders by the reduced cylinder operation control, thereby greatly reducing the amount of heat generated by the engine 11.
[0034]
On the other hand, if it is determined in step 106 that the abnormal level is level 2 (the level at which the possibility of the engine 11 becoming overheated is relatively low), the process proceeds to step 108, where the throttle opening limit for level 2 is restricted. A map of the value f2 is searched to calculate a throttle opening limit value f2 (Ne) corresponding to the current engine rotational speed Ne, and this value is set as a throttle opening limit value THRMX.
THRMX = f2 (Ne)
[0035]
The map of the throttle opening limit value f2 for level 2 is set such that the throttle opening limit value f2 for level 2 is larger than the throttle opening limit value f1 for level 1. ing.
[0036]
Thereafter, the routine proceeds to step 109, where the target throttle opening degree THR0 calculated in step 102 is compared with the throttle opening limit value THRMX = f2 (Ne) for level 2 calculated in step 108, and the smaller one is compared. The final target throttle opening THR is set.
[0037]
Accordingly, when the abnormal level is level 2, the throttle opening is limited by the throttle opening limit value THRMX = f2 (Ne) for level 2 (guard processing), thereby limiting the amount of air charged in each cylinder. Then, the amount of combustion heat of each cylinder is reduced, and the amount of heat generated by the engine 11 is reduced.
[0038]
The processing of these steps 104 to 109 plays a role as a heating value reduction control means referred to in the claims.
[0039]
On the other hand, in step 104, if the abnormal level is neither level 1 nor level 2, that is, if the abnormal level is level 3 (the level at which the engine 11 is unlikely to overheat) or the flow control valve 19 If it is determined that there is no abnormality, the routine proceeds to step 110, where the target throttle opening THR0 calculated based on the accelerator opening and the like in step 102 is directly set as the final target throttle opening THR. In this case, the heat generation amount reduction control is not executed.
[0040]
[Abnormality diagnosis and abnormality level judgment]
The abnormality diagnosis and abnormality level determination routine shown in FIG. 3 is a subroutine started in step 103 of FIG. When this routine is started, first, in step 201, an input process is executed to read the output of various sensors and the like, and then the process proceeds to step 202, where a disconnection / short circuit determination routine (not shown) is executed to execute the flow control valve. It is determined whether there is a disconnection or short circuit of the actuator 19 or the power supply line.
[0041]
Here, if the actuator 20 of the flow control valve 19 or the power supply line is disconnected, the power supply to the actuator 20 is disabled, so that the rotary valve of the flow control valve 19 is biased by a biasing means such as a return spring. Moves to or near the rotational position where the radiator flow rate Vr is maximized. As a result, the amount of heat radiation of the cooling water by the radiator 12 increases, and the engine cooling performance by the cooling water increases, so that the overheating of the engine 11 can be prevented.
[0042]
On the other hand, when a short circuit occurs in the actuator 20 or the power supply line of the flow control valve 19, the actuator 20 is always energized, and the rotary valve of the flow control valve 19 reduces the radiator flow Vr. In the direction (the direction in which the bypass flow rate Vb is increased). For this reason, the amount of heat radiation of the cooling water by the radiator 12 decreases, and the engine cooling ability by the cooling water decreases, and the engine 11 may be overheated.
[0043]
Therefore, in order to prevent overheating of the engine 11 due to an electric short circuit between the actuator 20 of the flow control valve 19 and the power supply line, first, the process proceeds to step 203, and an electric short circuit between the actuator 20 of the flow control valve 19 and the power supply line is performed. It is determined whether or not it is present, and if it is determined that there is a short circuit, the process proceeds to step 204, and the power supply of the actuator 20 of the flow regulating valve 19 is cut off.
[0044]
In this case, the energization of the actuator 20 is cut off, so that the rotary valve of the flow rate adjusting valve 19 is moved to or near the rotational position where the radiator flow rate Vr is maximized by the urging force of the urging means such as a return spring. Moving. As a result, the amount of heat radiation of the cooling water by the radiator increases, and the engine cooling capacity by the cooling water increases, so that overheating of the engine 11 can be prevented.
[0045]
Thereafter, the routine proceeds to step 205, in which a flow control valve abnormality diagnosis routine shown in FIG. 4 described below is executed, and the flow control valve is controlled based on the temperature difference between the actual cooling water temperature Tp detected by the water temperature sensor 21 and the target cooling water temperature Ttg. A diagnosis is made as to whether or not there is an abnormality in the flow control valve 19 (for example, an operation abnormality due to entry of a foreign substance into the flow control valve 19 or sticking of the valve).
[0046]
Thereafter, the routine proceeds to step 206, where it is determined whether or not the flow control valve 19 is abnormal. If it is determined that the flow control valve 19 is not abnormal, the routine ends.
[0047]
On the other hand, if it is diagnosed that the flow control valve 19 is abnormal, the process proceeds to step 207, where the temperature difference between the actual cooling water temperature Tp detected by the water temperature sensor 21 and the target cooling water temperature Ttg is equal to the first level determination value K1. It is determined whether it is greater than or equal to. As a result, when it is determined that the temperature difference between the actual cooling water temperature Tp and the target cooling water temperature Ttg is larger than the first level determination value K1, the process proceeds to step 208, where the abnormal level is set to level 1 (the engine 11 (A level at which overheating is likely to occur).
[0048]
On the other hand, when it is determined in step 207 that the temperature difference between the actual cooling water temperature Tp and the target cooling water temperature Ttg is equal to or less than the first level determination value K1, the process proceeds to step 209, and It is determined whether or not the temperature difference between the water temperature Tp and the target cooling water temperature Ttg is greater than a second level determination value K2 (where K2 <K1). As a result, when it is determined that the temperature difference between the actual cooling water temperature Tp and the target cooling water temperature Ttg is larger than the second level determination value K2, the process proceeds to step 210, where the abnormal level is set to level 2 (the engine 11 (A level at which the possibility of overheating is relatively low).
[0049]
If it is determined that the temperature difference between the actual cooling water temperature Tp and the target cooling water temperature Ttg is equal to or less than the second level determination value K2, the process proceeds to step 211, where the abnormal level is level 3 (the engine 11 is overheated). ).
The processing of these steps 206 to 211 plays a role as an abnormal degree determining means referred to in the claims.
[0050]
[Flow control valve abnormality diagnosis]
The flow control valve abnormality diagnosis routine shown in FIG. 4 is a subroutine started in step 205 in FIG. 3, and plays a role as abnormality diagnosis means in the claims. When this routine is started, first, in step 301, input processing is executed to read the output of various sensors, etc., and then the process proceeds to step 302, where it is determined whether or not the abnormality diagnosis execution condition is satisfied, for example, The determination is made based on whether or not the engine operation state is a steady state. If the abnormality diagnosis execution condition is not satisfied, the process proceeds to step 308, where the count value of a counter Cnt described later is reset to “0”, and then this routine ends.
[0051]
On the other hand, when it is determined that the abnormality diagnosis execution condition is satisfied, the routine proceeds to step 303, where an error of the actual cooling water temperature Tp with respect to the target cooling water temperature Ttg is obtained as a control water temperature error Te.
Te = | Ttg-Tp |
[0052]
Thereafter, the routine proceeds to step 304, where it is determined whether or not the control water temperature error Te is smaller than the abnormality determination value β. The abnormality determination value β is set according to the engine operating state (for example, engine speed and load).
[0053]
If it is determined in step 304 that the control water temperature error Te is smaller than the abnormality determination value β, the process proceeds to step 308, where the count value of a counter Cnt, which will be described later, is reset to “0”. I do.
[0054]
On the other hand, if it is determined in step 304 that the control water temperature error Te is equal to or greater than the abnormality determination value β, the process proceeds to step 305, and the duration of the state where the control water temperature error Te is equal to or greater than the abnormality determination value β is determined. After incrementing the count value of the counter Cnt to be counted by "1", the process proceeds to step 306, and it is determined whether or not the count value of the counter Cnt has exceeded a predetermined value C. As a result, when it is determined that the count value of the counter Cnt is equal to or smaller than the predetermined value C, the present routine is terminated as it is.
[0055]
On the other hand, when the count value of the counter Cnt exceeds the predetermined value C, that is, when the duration of the state where the control water temperature error Te is equal to or more than the abnormality determination value β exceeds the predetermined value C, the process proceeds to step 307. The driver determines that there is an abnormality in the flow control valve 19, turns on a warning lamp (not shown) provided on an instrument panel in the driver's seat, or displays a warning on a warning display unit (not shown) to display the driver. And the abnormality information (abnormality code) is stored in the backup RAM (not shown) of the ECU 30, and the routine ends.
[0056]
According to the present embodiment described above, the presence / absence of an abnormality of the flow control valve 19 is diagnosed, and when the abnormality of the flow control valve 19 is diagnosed, the heat generation amount reduction control (in the present embodiment, the throttle opening limit control, (Reduced cylinder operation control) is executed, so that even if the cooling water temperature rises due to an abnormality of the flow rate control valve 19 and the engine cooling capacity decreases, the calorific value of the engine 11 is reduced by the calorific value reduction control. Thus, an increase in the engine temperature can be suppressed, and overheating of the engine 11 can be prevented. Thus, even when the flow control valve 19 is abnormal, the vehicle can be evacuated without causing the engine 11 to overheat.
[0057]
Further, in the present embodiment, when it is diagnosed that the flow control valve 19 is abnormal, the abnormality level at that time (for example, the degree of increase of the actual cooling water temperature Tp with respect to the target cooling water temperature Ttg) is determined. When the abnormal level is level 1 (the level at which the engine 11 is likely to be overheated), the throttle opening limit control for limiting the throttle opening with the throttle opening limit value THRMX = f1 for level 1 is performed. By executing both the reduced cylinder operation control, the calorific value of the engine 11 is significantly reduced. On the other hand, when the abnormal level is level 2 (the level at which the possibility of the engine 11 becoming overheated is relatively low), the throttle opening limit is set such that the throttle opening is limited by the throttle opening limit value THRMX = f2 for level 2. By executing only the control, the calorific value of the engine 11 is reduced. With this configuration, the amount of reduction in the amount of heat generated by the engine 11 by the heat generation amount reduction control according to the abnormal level can be varied, and the amount of heat generated by the engine 11 can be reduced by an amount necessary to prevent overheating. Can be. As a result, it is possible to prevent the calorific value of the engine 11 from being reduced more than necessary, and it is possible to minimize the decrease in the operation performance of the engine 11 due to the calorific value reduction control.
[0058]
Further, even when it is diagnosed that the flow regulating valve 19 is abnormal, for example, when the radiator flow is in an abnormal state in which the radiator flow is increased from the normal state or in an abnormal state in which the radiator flow is slightly decreased from the normal state. In this case, the temperature of the cooling water flowing into the engine 11 does not rise, or even if it rises, the rising width is small, so that the cooling capacity of the engine by the cooling water hardly decreases. In such a case, it is considered that there is almost no possibility that the engine 11 will be overheated without executing the heat generation amount reduction control.
[0059]
Therefore, in the present embodiment, even if it is diagnosed that the flow control valve 19 is abnormal, if the abnormal level is level 3 (the level at which the engine 11 is unlikely to overheat), the heat generation amount reduction control is not performed. Since the same control as that in the normal state is executed, the heat generation amount reduction control need not be executed in a situation where the engine 11 is unlikely to be overheated. Can be avoided.
[0060]
In this embodiment, the throttle opening restriction control and the reduced cylinder operation control are executed as the heat generation amount reduction control, but the fuel cut control may be executed as the heat generation amount reduction control. If the fuel cut is executed, the amount of heat of combustion can be reduced by that amount, so that the amount of heat generated by the engine 11 can be reduced.
[0061]
In the case of an engine capable of stratified lean combustion such as an in-cylinder injection engine, stratified lean combustion control may be executed as heat generation amount reduction control. In the stratified lean combustion, by burning the lean air-fuel mixture, the heat of combustion of each cylinder can be reduced, and the calorific value of the engine 11 can be reduced.
[0062]
Also, in the case of a system having a variable valve mechanism for varying the valve control amount (valve timing, valve lift amount, etc.) of the intake valve and the exhaust valve, the valve control amount change control is executed as the heat generation amount reduction control. May be. If the valve control amounts (valve timing, valve lift amount, etc.) of the intake valve and the exhaust valve are changed in the direction in which the amount of air charged to each cylinder decreases, the engine 11 can be controlled in the same manner as in the case of limiting the throttle opening. The amount of heat generated can be reduced.
[0063]
The control items of the calorific value reduction control such as the throttle opening limit, the reduced cylinder operation, the fuel cut, the stratified lean combustion, and the change of the valve control amount may be executed by only one control item. The above control items may be executed in combination. Further, the combination of control items of the heat generation amount reduction control and the control amount may be changed according to the abnormal level.
[0064]
In the present embodiment, the abnormal level is determined in three stages, but the abnormal level may be determined in two stages or four or more stages.
Further, in order to simplify the fail-safe control, the determination of the abnormal level is omitted, and when it is diagnosed that the flow control valve 19 is abnormal, the heat generation amount reduction control of the same control item and control amount is always executed. You may do it.
[0065]
In the present embodiment, the bypass flow rate Vb and the radiator flow rate Vr are controlled by the single flow rate control valve 19 by providing the flow rate control valve 19 at the junction of the bypass flow path 18 and the cooling water circulation pipe 14. However, a flow rate adjusting valve may be provided in each of the bypass flow path 18 and the cooling water circulation pipe 14, and the bypass flow rate Vb and the radiator flow rate Vr may be controlled by two flow rate adjusting valves. In this case, it is diagnosed whether or not the two flow control valves are operating normally, and if one of the two flow control valves is determined to be abnormal, the calorific value reduction control is executed. You can do it.
[0066]
In addition, the present invention can be implemented with various changes such as changing the mounting position of the water temperature sensor as appropriate, for example, installing the water temperature sensor at a position close to the cooling water outlet of the engine 11.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a cooling system according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a flow of a process of a fail-safe control base routine of a flow control valve;
FIG. 3 is a flowchart showing the flow of processing of an abnormality diagnosis and abnormality level determination routine;
FIG. 4 is a flowchart showing a flow of a process of a flow control valve abnormality diagnosis routine;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Radiator, 18 ... Bypass flow path, 19 ... Flow control valve, 21, 22, 23 ... Water temperature sensor (water temperature detection means), 27 ... Throttle valve, 30 ... ECU (Water temperature control means) , Abnormality diagnosis means, heat generation amount reduction control means, abnormality degree determination means).

Claims (5)

A control device for an internal combustion engine, comprising: a flow control valve capable of adjusting a flow rate of cooling water flowing by bypassing a radiator; and a water temperature control unit configured to control the flow rate control valve to control a cooling water temperature.
Abnormality diagnosing means for diagnosing the presence or absence of an abnormality of the flow control valve,
A heat generation amount reduction control unit that executes control for reducing the heat generation amount of the internal combustion engine (hereinafter, referred to as “heat generation amount reduction control”) when the abnormality diagnosis unit diagnoses that the flow control valve is abnormal; A control device for an internal combustion engine. When the abnormality diagnosing unit is diagnosed as having an abnormality in the flow rate adjustment valve, the abnormality diagnosing unit includes an abnormality degree determining unit that determines a degree of the abnormality at that time,
2. The control method according to claim 1, wherein the heat generation amount reduction control unit sets a control item and / or a control amount to be subjected to the heat generation amount reduction control according to the degree of abnormality determined by the abnormality degree determination unit. A control device for an internal combustion engine according to claim 1. The heat generation amount reduction control means is configured such that, even when the abnormality diagnosis means diagnoses that the flow rate control valve is abnormal, if the degree of abnormality determined by the abnormality degree determination means is equal to or less than a predetermined level, the heat generation amount The control device for an internal combustion engine according to claim 2, wherein the reduction control is not performed. The heat generation amount reduction control means is configured to reduce the heat generation amount by at least one of throttle opening restriction, fuel cut, stratified lean combustion, reduced cylinder operation, and control amount change of a variable valve mechanism on an intake side and / or an exhaust side. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein control is performed. A cooling water temperature detecting means for detecting a cooling water temperature,
The water temperature control means controls the flow rate adjustment valve so that the cooling water temperature detected by the water temperature detection means matches the target cooling water temperature,
The abnormality diagnosis means compares the cooling water temperature detected by the water temperature detection means with a target cooling water temperature during execution of the cooling water temperature control by the water temperature control means, and diagnoses whether there is an abnormality in the flow rate adjustment valve. The control device for an internal combustion engine according to any one of claims 1 to 4, wherein

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