JP5125755B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, to a control device for an internal combustion engine that is applied to an internal combustion engine including a thermostat and a water temperature sensor and uses a detected water temperature value as control information based on an output value of the water temperature sensor. It is about.

2. Description of the Related Art Conventionally, a cooling system for an internal combustion engine is known that includes a radiator and a cooling water passage that connects the radiator and the internal combustion engine, and circulates the cooling water between the internal combustion engine and the radiator. Further, a thermostat for controlling the cooling water temperature is generally provided in the middle of the cooling water passage (see, for example, Patent Document 1). In this cooling system, the thermostat is closed at a low temperature of the internal combustion engine (for example, 60 ° C. or less), whereby the circulation of the cooling water is stopped in the circulation path including the radiator. Thereby, since cooling with a radiator is not performed, an internal combustion engine is warmed up rapidly. On the other hand, when the thermostat is opened at a high temperature of the internal combustion engine (for example, 80 ° C. or higher), the cooling water is circulated in the circulation path including the radiator. As a result, the cooling water that has been heated from the internal combustion engine and heated to high temperature is cooled by the radiator, so that the internal combustion engine can be maintained at an appropriate temperature.
Japanese Patent Laid-Open No. 2007-1000076

  By the way, for example, when the thermostat is switched from the valve closing to the valve opening with the completion of warming up of the internal combustion engine, it is conceivable that the cooling water cooled by the radiator flows into the internal combustion engine at a stretch and the temperature of the cooling water is not stabilized. That is, the cooling water sufficiently warmed on the internal combustion engine side and the cooling water sufficiently cooled on the radiator side are mixed to make the temperature of the cooling water non-uniform. For this reason, the difference between the peak value (maximum value) and the bottom value (minimum value) of the detected water temperature value may increase, and the detected water temperature value may greatly fluctuate (hunting). If such a water temperature detection value is used as it is for the control of the internal combustion engine, the control system becomes unstable and the controllability may be reduced.

  The above problems are likely to occur in the case of a high response sensor. On the other hand, when the low response sensor is used, the response of the sensor output to the water temperature change is low, so the water temperature change at the start of the engine cannot be detected correctly, and there is a concern that the fuel injection amount may not be properly increased at the start. Is done.

  The present invention has been made in order to solve the above-described problems, and can satisfy the demand for the responsiveness of the sensor output and the demand for the stability of the water temperature sensor as needed, and thus is suitable for controlling the internal combustion engine. An object of the present invention is to provide a control device for an internal combustion engine that can be implemented in the first place.

  The present invention employs the following means in order to solve the above problems.

The first configuration includes a thermostat provided in a cooling water passage connecting the internal combustion engine and the radiator, and opening and closing according to the temperature of the cooling water in the cooling water passage, and a water temperature sensor for detecting the temperature of the cooling water. A control device for an internal combustion engine that is applied to an internal combustion engine that uses a detected water temperature value based on an output value of the water temperature sensor as control information, wherein the detected water temperature value is annealed at a predetermined annealing rate. And means for changing the embodiment of the annealing process according to opening and closing of the thermostat.

  For example, when the thermostat is switched from valve closing to valve opening, it is conceivable that the temperature of the cooling water is not stable because the low-temperature cooling water from the radiator flows into the internal combustion engine. For this reason, the detected water temperature value may fluctuate and the control system may become unstable. In that respect, in the present invention, the water temperature detection value is subjected to the annealing process in an embodiment according to the opening and closing of the thermostat. Specifically, for example, the degree of annealing is changed by switching whether to perform the annealing process according to the opening / closing of the thermostat or by changing the annealing rate according to the opening / closing of the thermostat. . As a result, among the responsiveness and stability of the sensor output, the degree of smoothing is reduced when responsiveness is required, and the degree of smoothing is increased when stability is required. The output can be used properly. Therefore, it is possible to satisfy the demand for the responsiveness of the sensor output and the demand for the stability as necessary, and thus it is possible to suitably control the internal combustion engine.

In the second configuration , opening and closing of the thermostat is determined based on the temperature of the cooling water in the cooling water passage, and the embodiment of the annealing process is changed according to the determination result. Since opening and closing of the thermostat and the temperature of the cooling water have a correlation, the opening and closing of the thermostat can be easily detected with the above configuration. Moreover, it becomes possible to set the annealing rate according to the opening degree of a thermostat, and it becomes possible to implement an annealing process in the aspect according to the grade of the temperature fluctuation of a cooling water.

During a cold start of the internal combustion engine, the temperature difference between the cooling water on the internal combustion engine side and the cooling water on the radiator side is increased by warming up with the thermostat closed. Therefore, if the thermostat is opened during the cold start of the internal combustion engine, fluctuation (hunting) of the detected water temperature is likely to occur as the valve is opened. On the other hand, since the cooling water does not flow from the radiator side before the thermostat is opened, the hunting of the water temperature detection value is considered to be minute. In view of that point, the third configuration is that when the internal combustion engine is cold-started and the thermostat shifts from closed to open, the embodiment of the annealing process is not smoothed. Switch to smoothing, or switch the annealing rate to a larger value. This makes it possible to maintain sensor responsiveness to temperature changes during periods where hunting of the water temperature detection value is difficult to occur, and to suppress hunting during periods where hunting of the water temperature detection value is likely to occur. It is possible to suitably improve the controllability.

It is considered that the temperature difference between the cooling water on the radiator side and the cooling water on the internal combustion engine side increases as the radiator cools, depending on the vehicle running state. In view of this point, the fourth configuration detects that the traveling state of the vehicle is a cooling promotion state in which cooling of the radiator is promoted, and detects that the vehicle traveling state corresponds to the cooling promotion state. And when the thermostat shifts from closing to opening, the embodiment of the annealing process is switched from non-annealing to smoothing, or the annealing rate is increased. Switch to value. According to this configuration, it is possible to suppress hunting of the water temperature detection value caused by the vehicle running state. Here, examples of the vehicle running state corresponding to the cooling promotion state include a case where the vehicle speed is equal to or higher than a predetermined high speed and a case where the outside air temperature is equal to or lower than a predetermined low temperature.

In the fifth configuration , the embodiment of the annealing process is returned to the mode before the change after a predetermined time has elapsed since the thermostat was switched from the closed valve to the opened valve. According to this configuration, when the detected water temperature value converges with time, priority can be given to sensor responsiveness to temperature changes, and thus controllability of the internal combustion engine can be improved.

When the water temperature sensor is a highly responsive sensor, it is sensitive to changes in the cooling water temperature. Therefore, when the cooling water flows from the radiator when the thermostat is opened, hunting of the detected water temperature is likely to occur. In view of this point, the sixth configuration makes the water temperature sensor a highly responsive sensor having relatively high responsiveness to temperature fluctuations. By doing so, in the high response sensor, hunting of the water temperature detection value accompanying the opening of the thermostat can be suitably suppressed. Here, the high-responsiveness sensor is a sensor that has a relatively high response to temperature fluctuation, and specifically has a time constant when it is poured into water at a normal temperature (for example, 20 ° C.) to a high temperature (for example, 100 ° C.). The one within about 5 seconds.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an engine control system is constructed for a multi-cylinder gasoline engine for a motorcycle. In this control system, an electronic control unit (hereinafter referred to as ECU) is used as a center to control the fuel injection amount, control the ignition timing, and the like. FIG. 1 shows an overall schematic configuration diagram of the engine control system.

  FIG. 1 is an overall schematic configuration diagram of an engine control system in the present embodiment. In FIG. 1, an engine 10 is provided with an air cleaner 12 at the most upstream portion of an intake pipe 11 (intake passage). A throttle valve 14 whose opening degree is adjusted by a throttle actuator 13 such as a DC motor is provided on the downstream side of the air cleaner 12. The opening degree of the throttle valve 14 (throttle opening degree) is detected by a throttle opening degree sensor built in the throttle actuator 13.

  An intake pipe pressure sensor 15 for detecting the intake pipe pressure is provided on the downstream side of the throttle valve 14, and on the downstream side, an electromagnetically driven fuel injection for supplying fuel to the vicinity of the intake port of each cylinder. A valve 16 is attached.

  An intake valve 17 and an exhaust valve 18 are provided at the intake port and the exhaust port of the engine 10, respectively. Then, the air / fuel mixture is introduced into the combustion chamber 19 by the opening operation of the intake valve 17, and the exhaust gas after combustion is discharged to the exhaust pipe 21 (exhaust passage) by the opening operation of the exhaust valve 18.

  A spark plug 22 is attached to the cylinder head of the engine 10. A high voltage is applied to the spark plug 22 at a desired ignition timing through an ignition device 23 made of an ignition coil or the like. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 22, and the air-fuel mixture introduced into the combustion chamber 19 is ignited and used for combustion.

  The engine 10 is provided with a cooling system for cooling the engine 10. FIG. 2 is an overall schematic configuration diagram of the cooling system 50. With respect to the cooling system 50, a water jacket 51 is formed inside the cylinder block and cylinder head of the engine 10, and cooling water is injected into the water jacket 51.

  The water jacket 51 is connected to the radiator 52 via a cooling water passage 53 constituted by an outward flow path and a return flow path. A water pump 55 is provided at the inlet of the water jacket 51. The cooling water circulates in the cooling water passage 53 by driving the water pump 55. Specifically, the cooling water takes heat of the engine 10 while passing through the water jacket 51 and is then introduced into the radiator 52 through one cooling water passage 53a. Then, after the cooling water is cooled by the radiator 52, it is returned again to the engine 10 through the cooling water passage 53b. As a result, the engine 10 is maintained at an appropriate temperature (for example, 80 ° C.).

  A thermostat 54 is provided in the middle of the cooling water passage 53a (engine 10 → radiator 52). The thermostat 54 changes the flow path of the cooling water by operating according to the cooling water temperature. Specifically, the thermostat 54 is closed when the coolant temperature is relatively low (for example, when the engine 10 is cold started), and stops the circulation of the coolant between the engine 10 and the radiator 52. Let Thereby, since the cooling water cooled by the radiator 52 is not supplied to the engine 10, the engine 10 is warmed up quickly. In the present embodiment, a bypass passage 53c that connects the cooling water passages 53a and 53b to the thermostat 54 on the engine side is provided, and the cooling water passage 53a → bypass passage by closing the thermostat 54. The cooling water circulates in the direction of 53c → cooling water passage 53b.

  When the coolant temperature on the engine side reaches a predetermined thermostat valve opening temperature (for example, about 70 ° C.), the thermostat 54 is opened, and the coolant circulates between the engine 10 and the radiator 52. Thereby, since the cooling water from the radiator 52 is supplied to the engine 10 side, the engine 10 is maintained at an appropriate temperature. A cooling fan 56 is provided in the vicinity of the radiator 52, and the heat dissipation effect of the radiator 52 is enhanced by the rotation of the cooling fan 56, and cooling of the cooling water in the radiator 52 is promoted.

  Returning to the description of FIG. 1, a cooling water temperature sensor 24 for detecting the cooling water temperature on the engine side is attached to the cylinder block of the engine 10. In addition, this system is provided with a crank angle sensor 25 for outputting a crank angle signal at every predetermined crank angle of the engine.

  As is well known, the ECU 40 is mainly composed of a microcomputer (hereinafter referred to as a microcomputer) 41 composed of a CPU, ROM, RAM, and the like, and executes various control programs stored in the ROM, so that the engine operation state can be changed each time. In response, various controls of the engine 10 are performed. Specifically, the microcomputer 41 of the ECU 40 inputs various detection signals from the various sensors described above, calculates the fuel injection amount, ignition timing, etc. based on these various detection signals and the like, and calculates the fuel injection valve 16 and the ignition. The driving of the device 23 is controlled, or the driving of the water pump 55 and the cooling fan 56 is controlled.

  By the way, when the engine-side coolant temperature (temperature detected by the coolant temperature sensor 24) reaches the thermostat valve opening temperature and the thermostat 54 is switched from the closed valve to the opened valve, the low-temperature coolant sufficiently cooled by the radiator 52 is provided. Flows into the engine side, and the low-temperature cooling water mixes with the high-temperature cooling water sufficiently warmed on the engine side. For this reason, the cooling water temperature is not stabilized until the low-temperature cooling water and the high-temperature cooling water are sufficiently mixed, and the water temperature detection value based on the output value of the cooling water temperature sensor 24 may be hunted.

  FIG. 3 is a time chart showing the transition of the detected water temperature when the engine 10 is cold started. In FIG. 3, when the engine start is started, the engine 10 is warmed up with the thermostat 54 closed, so that the detected water temperature rises quickly. Then, when the thermostat valve opening temperature Top is reached at time t1, the thermostat 54 is opened, whereby the low-temperature cooling water on the radiator 52 side flows into the engine side. In such a case, it is conceivable that the temperature of the cooling water in the water jacket 51 is not stabilized and the detected water temperature causes hunting. That is, until the temperature in the water jacket 51 becomes uniform (until hunting disappears), the difference between the peak value and the bottom value of the water temperature detection value increases, and the water temperature detection value may vary greatly. Therefore, if the engine control is performed using the detected water temperature value as it is, the control system may become unstable.

  In particular, in a motorcycle, since the power per displacement of the engine 10 is generally larger than that of an automobile, the ratio of the amount of water in the radiator to the amount of water on the engine side is larger than in an automobile (for example, the amount of water in the radiator is It is conceivable that it is 1.5 times or more of the side). Therefore, in a motorcycle, the temperature difference between the cooling water on the engine side and the radiator side becomes larger, and the above event is likely to occur.

  In addition, when the cooling water temperature sensor 24 is a high response type water temperature sensor, the above phenomenon is likely to occur because it is sensitive to changes in the cooling water temperature. Here, the high response type water temperature sensor refers to a sensor that has a relatively fast time response to a change in water temperature. When a water temperature sensor is inserted into water, the time (time constant) required to reach 63.2% of the final value of the sensor output is, for example, within 5 seconds.

  Therefore, in the present embodiment, the water temperature detection value is subjected to the annealing process in an embodiment according to the opening / closing of the thermostat 54. Specifically, when the engine is started (for example, during cold start), the water temperature detection value reaches, for example, the thermostat valve opening temperature or a value near that (for example, minus 10 ° C. or minus 20 ° C. of the thermostat opening temperature). At that point, switch from smooth to smooth.

  In this embodiment, the annealing calculation is performed using the following equation (1) as the annealing process. Here, in the following formula (1), LTHWSM [i] indicates the current smoothing value, LTHWSM [i-1] indicates the previous smoothing value, ksm indicates the smoothing rate, and LTHWB [i] indicates the current water temperature raw value. . At the time of the first calculation, the current water temperature raw value LTHWB [i] is set to the previous smoothed value LTHWSM [i].

LTHWSM [i] = LTHWSM [i-1] +
ksm * (LTHWB [i] −LTHWSM [i−1]) (1)

  FIG. 4 is a flowchart illustrating an example of a processing procedure for calculating the control water temperature. This process is repeatedly executed by the microcomputer 41 of the ECU 40 at a predetermined cycle (for example, every 16 msec).

  First, in step S11 of FIG. 4, a raw water temperature value LTHWB calculated based on the output value of the cooling water temperature sensor 24 is read. For details on the water temperature raw value LTHWB, the sensor output value (analog value) is AD converted at a predetermined AD cycle to calculate the digital value, and a map based on the relationship between the predetermined sensor output value and the water temperature is referred to. Thus, the water temperature raw value LTHWB is calculated from the sensor output value (digital value).

  In a succeeding step S12, it is determined whether or not the engine 10 is cold started. Here, it is determined that the engine 10 is in a cold start when it is the first engine start period after the ignition is turned on (for example, within a predetermined time after the ignition is turned on).

  If it is during the cold start of the engine 10, the process proceeds to step S13, and it is determined whether or not the control water temperature LTHW is equal to or higher than the smoothing switching temperature kLTHWH. Here, the control water temperature LTHW is a water temperature detection value actually used in engine control, and is a value updated in accordance with the current value of the control water temperature LTHW in steps S14 to S16 described below. Further, the annealing switching temperature kLTHWH is a thermostat valve opening temperature in the present embodiment.

  When the control water temperature LTHW is lower than the annealing switching temperature kLTHWH, the process proceeds to step S14, and the water temperature raw value LTHWB is set to the control water temperature LTHW. That is, when the thermostat 54 is closed, the raw water temperature value LTHWB is used as it is as the control water temperature LTHW without performing the smoothing process. On the other hand, if the control water temperature LTHW is equal to or higher than the annealing switching temperature kLTHWH, the process proceeds to step S15, the water temperature annealing value LTHWSM is calculated using the above equation (1), and the water temperature annealing value LTHWSM is calculated in step S16. Set to control water temperature LTHW. That is, after the thermostat 54 is switched from valve closing to valve opening, the water temperature raw value LTHWB is subjected to a smoothing process, and the water temperature smoothing value LTHWSM is set as the control water temperature LTHW.

  When the cold start of the engine 10 is finished, a negative determination is made in step S12, and the processes of steps S15 and S16 are executed. That is, after the engine is started, after the smoothing switching temperature kLTHWH has been reached, the smoothing process of the water temperature raw value LTHWB is continued as it is after the switching from smoothing to smoothing.

  FIG. 5 is a time chart showing the transition of the control water temperature LTHW at the time of engine cold start. In the figure, the solid line indicates the transition of the control water temperature LTHW, the dotted line indicates the transition of the water temperature raw value LTHWB, and the two-dot chain line indicates the transition of the water temperature smoothing value LTHWSM. The dotted line in FIG. 5 corresponds to the solid line in FIG. Moreover, about the water temperature annealing value LTHWSM, the figure has shown the value at the time of performing the annealing process from the start.

  After the start of the engine 10, until the time t1 when the control water temperature LTHW becomes the annealing switching temperature kLTHWH, the water temperature raw value LTHWB is not executed, and the water temperature raw value LTHWB is used as it is as the control water temperature LTHW. Thereby, it is possible to respond quickly to the temperature change of the cooling water accompanying the engine warm-up.

  Thereafter, when the control water temperature LTHW reaches the smoothing switching temperature kLTHWH during engine warm-up, the water temperature raw value LTHWB is started to be treated as the control water temperature LTHW. As a result, hunting of the control water temperature LTHW is suppressed as compared with the case without annealing (in the case of the dotted line in the figure).

  At the time of switching of the annealing process, in this embodiment, the control water temperature LTHW immediately before the switching, that is, the water temperature raw value LTHWB is used as the previous value of the water temperature smoothing value LTHWSM, and the water temperature is smoothed as the control water temperature by the above equation (1). The value LTHWSM is calculated. Here, the water temperature raw value LTHWB (dotted line in the figure) and the water temperature smoothed value LTHWSM (two-dot chain line in the figure) are obtained from the start of the engine start, and the control water temperature LTHW reaches the gentle switching temperature kLTHWH. In the configuration in which the water temperature raw value LTHWB is switched to the water temperature smoothed value LTHWSM, the point A is shifted from the point A on the dotted line to the point B on the two-dot chain line, and the control water temperature LTHW is greatly reduced at the time of the transition, resulting in a step. (See FIG. 5). On the other hand, in the present embodiment, the control water temperature LTHW at the time of switching of the smoothing process is calculated by calculating the current smoothing value LTHWSM [i] using the water temperature raw value LTHWB immediately before switching as the previous smoothing value LTHWSM [i-1]. Suppresses fluctuations.

  According to the first embodiment described above, the following excellent effects can be obtained.

  When the thermostat 54 is switched from closed to open, the water temperature raw value LTHWB is smoothed and the water temperature smoothed value LTHWSM is set to the control water temperature LTHW. As a result, the controllability of the engine 10 can be improved.

  Further, since the water temperature raw value LTHWB is set to the control water temperature LTHW until the thermostat 54 is opened, it is possible to maintain the responsiveness to the temperature change in the period in which the control water temperature LTHW hardly changes. That is, since the raw water temperature value LTHWB is not smoothed at the initial stage of engine start, the actual engine water temperature can be accurately detected. As a result, it is possible to suitably perform the start-up increase control of the fuel injection amount based on the engine water temperature, and to improve the controllability of the engine 10.

  Since the thermostat 54 is determined based on the control water temperature LTHW that the valve has been switched from closed to open, the start timing of the annealing process can be easily detected. Thereby, the annealing process can be started at an appropriate time, which is suitable for stabilizing the control system.

  Since the cooling water temperature sensor 24 is a highly responsive sensor, the control water temperature LTHW is likely to fluctuate due to good sensor responsiveness. According to this embodiment, the control water temperature associated with the opening of the thermostat 54 is controlled. The variation in LTHW can be suitably suppressed.

  When the mode of the smoothing process for the water temperature raw value LTHWB is switched from non-smoothing to smoothing, the control water temperature LTHW immediately before the switching is configured to perform the smoothing process as the previous smoothing value LTHWSM [i-1]. The control water temperature LTHW can be prevented from fluctuating during the switching.

(Second Embodiment)
Next, a second embodiment of the present invention will be described focusing on differences from the first embodiment. In the first embodiment, the annealing process is performed when the engine 10 is cold-started and the control water temperature LTHW reaches the annealing switching temperature kLTHWH. However, in the present embodiment, the vehicle is running further. If necessary, perform an annealing process.

  Specifically, when the control water temperature LTHW reaches the smoothing switching temperature kLTHWH after the engine cold start, execution of the smoothing process of the water temperature raw value LTHWB is started. Thereafter, the execution of the annealing process is stopped when a predetermined time (for example, several minutes) elapses after the annealing switching temperature kLTHWH is reached. Further, after the execution of the annealing process is stopped, the annealing process is performed again when the vehicle running state is in a state where cooling of the radiator 52 is promoted (cooling acceleration state). That is, when the vehicle travels, the cooling condition of the radiator 52 changes according to the travel conditions, and in this embodiment, the smoothing and the non-smoothing are switched according to the vehicle travel conditions.

  FIG. 6 is a flowchart illustrating an example of a processing procedure for calculating the control water temperature LTHW. This process is repeatedly executed by the microcomputer 41 of the ECU 40 at a predetermined cycle (for example, every 16 msec).

  In FIG. 6, the water temperature raw value LTHWB is read in step S21, and it is determined in step S22 whether or not the engine 10 is cold started. If it is during cold start, it is determined in step S23 whether the control water temperature LTHW is equal to or higher than the smoothing switching temperature kLTHWH. When the control water temperature LTHW is lower than the annealing switching temperature kLTHWH, the process proceeds to step S24, and the water temperature raw value LTHWB is set to the control water temperature LTHW.

  On the other hand, if the control water temperature LTHW is equal to or higher than the annealing switching temperature kLTHWH, the process proceeds to step S25 to determine whether or not a predetermined time to (for example, several minutes) has elapsed since the control water temperature LTHW reached the annealing switching temperature kLTHWH. judge. If the predetermined time to has not yet elapsed, the process proceeds to step S26, where the water temperature annealing value LTHWSM is calculated using, for example, the above equation (1), and the water temperature annealing value LTHWSM is controlled in step S27. Set to water temperature LTHW.

  On the other hand, when the predetermined time to has elapsed since the control water temperature LTHW reached the smoothing switching temperature kLTHWH, the process proceeds to step S24. That is, when the predetermined time to elapses after the start of the annealing process, the temperature is switched from being smoothed to not being smoothed at that time, and the water temperature raw value LTHWB is used as the control water temperature LTHW.

  If it is after the cold start of the engine 10 is completed, the process proceeds to step S28, and it is determined whether or not the vehicle is in a vehicle running state (cooling acceleration state) in which cooling of the radiator 52 is promoted. In this embodiment, when the vehicle speed is equal to or higher than a predetermined speed, or when the outside air temperature is in a predetermined low temperature region, it is determined that the vehicle is in a cooling acceleration state. If not in the cooling acceleration state, the process proceeds to step S29, and the water temperature raw value LTHWB is set to the control water temperature LTHW.

  On the other hand, in the cooling acceleration state, the process proceeds to steps S26 and S27, and the water temperature smoothing value LTHWSM is set to the control water temperature LTHW. In other words, in a situation where the radiator 52 is likely to be cooled due to vehicle driving wind, low temperature outside air, etc., the hunting of the control water temperature LTHW when the thermostat 54 is opened is suppressed by performing a smoothing process on the water temperature raw value LTHWB. To do.

  According to the second embodiment described above, the following excellent effects can be obtained.

  Since the smoothing process of the water temperature raw value LTHWB is performed when the radiator 52 becomes easy to cool while the vehicle is running, the fluctuation of the control water temperature LTHW caused by the difference in the cooling condition of the radiator 52 is suppressed. can do.

  Since the execution of the smoothing process is stopped when a predetermined time has elapsed since the opening of the thermostat 54, priority is given to the responsiveness of the cooling water temperature sensor 24 when the control water temperature LTHW converges as time elapses. As a result, the controllability of the engine 10 can be improved. In particular, in the cooling fan control of the radiator 52, it is necessary to correctly detect a change in the engine temperature while the vehicle is running or stopped in order to prevent the engine 10 from being overheated. For this reason, when the cooling water temperature sensor 24 is required to have high responsiveness, in the present embodiment, when a predetermined time has elapsed after the thermostat 54 is opened, the radiator is returned from the presence of the annealing process to the absence of the annealing process. The sensor output hunting can be suppressed while accurately controlling the fan 52.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  In the first embodiment, the configuration is such that the smoothing process is performed as it is after the engine has been started and then the smoothing process is performed. However, after the smoothing process is started, the smoothing process is performed again. You may stop. Specifically, for example, in FIG. 4, when it is determined in step S12 that the engine is not cold start, that is, it is determined that the predetermined time has passed since the ignition was turned on, the process proceeds to step S14, and the control water temperature LTHW is changed to the water temperature raw value LTHWB. And By doing so, priority can be given to the responsiveness of the coolant temperature sensor 24 in the engine control after the engine cold start is completed.

  In the above embodiment, the opening / closing of the thermostat 54 is determined based on the control water temperature LTHW. However, even if a sensor for measuring the opening degree of the thermostat 54 is provided and the opening / closing of the thermostat 54 is determined based on the detection value of the sensor. Good. In this way, the opening / closing of the thermostat 54 can be determined more accurately than in the determination based on the control water temperature LTHW.

  In the above embodiment, the execution of the smoothing process is started when the thermostat 54 is switched from the closed valve to the open valve. However, when the opening of the thermostat 54 (thermostat opening) exceeds the predetermined opening, It may be configured to start the process. In this way, the sensor response can be kept good for as long as possible. Here, in order to detect that the thermostat opening degree exceeds the predetermined opening degree, for example, based on the elapsed time after reaching the thermostat valve opening temperature, the water temperature detection value, the detection value of the sensor, or the like. You may go.

  In the above embodiment, the annealing process is performed in two modes, that is, whether the annealing is performed or not. However, the annealing rate ksm may be changed according to the opening / closing of the thermostat 54. Specifically, for example, the first smoothing rate ksm1 is set when the control water temperature LTHW is less than the smoothing switching temperature kLTHWH, and the second smoothing rate larger than the first smoothing rate ksm1 when the control water temperature LTHW is equal to or higher than the smoothing switching temperature kLTHWH. The rate is ksm2.

  -In the above-mentioned embodiment, it was set as the structure which switches whether the annealing process is performed with the annealing switching temperature kLTHWH as a boundary, but the structure which makes the annealing rate Ks variable in multiple steps according to the control water temperature LTHW It is good. By doing so, it is possible to set the annealing rate according to the opening degree of the thermostat 54, and it is possible to realize the control according to the degree of the temperature fluctuation of the cooling water.

1 is an overall schematic configuration diagram of an engine control system. The whole schematic block diagram of a cooling system. The time chart which shows transition of the water temperature detection value at the time of cold start. The flowchart which shows the process sequence which calculates control water temperature. The time chart which shows transition of the water temperature control value in the cold start. The flowchart which shows the process sequence which calculates the control water temperature in other embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 24 ... Cooling water temperature sensor, 40 ... ECU, 41 ... Microcomputer, 50 ... Engine cooling system, 51 ... Water jacket, 52 ... Radiator, 53 ... Coolant passage, 54 ... Thermostat.

Claims (5)

The invention is applied to an internal combustion engine provided with a thermostat provided in a cooling water passage connecting the internal combustion engine and a radiator and opening and closing according to the temperature of the cooling water in the cooling water passage, and a water temperature sensor for detecting the temperature of the cooling water. A control device for an internal combustion engine that uses a water temperature detection value based on an output value of the water temperature sensor as control information,
An annealing process means for performing an annealing process on the water temperature detection value at a predetermined annealing rate;
When the internal combustion engine is cold-started and the thermostat shifts from valve closing to valve opening, the embodiment of the smoothing process is switched from non-smoothing to smoothing or An annealing change means for switching the bracing rate to a larger value ,
A control device for an internal combustion engine, comprising: An opening / closing determination means for determining opening / closing of the thermostat based on the temperature of the cooling water in the cooling water passage;
The control apparatus for an internal combustion engine according to claim 1, wherein the annealing change unit changes an embodiment of the annealing process according to a determination result by the opening / closing determination unit. A running state detecting means for detecting that the running state of the vehicle is a cooling promotion state in which cooling of the radiator is promoted;
The smoothing changing means is a case where the running state detecting means detects that the vehicle running state corresponding to the cooling acceleration state is detected, and when the thermostat shifts from valve closing to valve opening, The control apparatus for an internal combustion engine according to claim 1 or 2 , wherein an embodiment of the annealing process is switched from non-annealing to annealing, or the annealing rate is switched to a larger value. The smoothing changing means any of claims 1 to 3, characterized in that return to the mode before the change the implementation of the smoothing processing from the time when the thermostat is switched to open from the closed after a predetermined time has elapsed The control apparatus for an internal combustion engine according to claim 1. The control apparatus for an internal combustion engine according to any one of claims 1 to 4 , wherein the water temperature sensor is a high-responsiveness sensor having relatively high responsiveness to temperature fluctuations.

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