JP2008019733A - Cooling control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain excessive cooling of an internal combustion engine when stopping the engine, while precisely restraining pre-ignition when beginning starting of the engine. <P>SOLUTION: The cooling control device cools an engine 1, by driving a cooling system, when the cooling water temperature is a threshold value or more, when stopping the engine 1. The threshold value is variably set as follows: when a crank angle when completing stopping of the engine 1, is one of positioning a piston 4 of a cylinder becoming a compression stroke in the first place at the bottom dead center after beginning starting of the next time, the threshold value is set at the cooling water temperature of not causing the pre-ignition in the cylinder when beginning starting of the next time. When the crank angle when completing stopping of the engine 1, is that where a position of the piston 4 of the cylinder becoming the compression stroke in the first place, becomes a position nearer to the top dead center than the bottom dead center after beginning starting of the next time, the threshold value is set so as to gradually becomes a higher value than the above-mentioned value, as the position of its piston 4 becomes a crank angle becoming near to the top dead center. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cooling control device for an internal combustion engine.

  In an internal combustion engine mounted on a vehicle such as an automobile, it is required that the start is completed at an early stage after the start of the engine. Fuel is burned in a cylinder that will be the second compression stroke later, and the first explosion after the start of the start is reached during the compression stroke.

  When the internal combustion engine is stopped, any one of the cylinders becomes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke, and the initial stage of each stroke is related to the pressure in the combustion chamber in each cylinder. The internal combustion engine is completely stopped. Therefore, when the internal combustion engine is stopped, the cylinder that is in the first compression stroke after the start of the next start is the cylinder that is stopped in the initial stage of the compression stroke, and the cylinder that is in the second compression stroke after the start of the next start Means that the cylinder is stopped at the beginning of the intake stroke.

  By the way, in the cylinders that reach the first compression stroke and the second compression stroke after the start of the internal combustion engine, the compression stroke is initial and the intake stroke is initial while the engine is stopped. The gas existing in the combustion chamber will be compressed after starting. Therefore, under the situation where the engine is started without a sufficient cooling period after the stop of the internal combustion engine, the temperature of the gas present in the combustion chamber is raised by the heat of the engine during the engine stop, Since the first compression stroke after the start of the engine starts and the second compression stroke are reached, the temperature of the gas in the combustion chamber during the compression stroke increases. When the temperature of the gas in the combustion chamber during the compression stroke becomes high, there is a risk that self-ignition (pre-ignition) of the fuel occurs in the combustion chamber. In particular, in an internal combustion engine in which the combustion operation is automatically stopped and restarted according to the running state of the vehicle to improve fuel consumption, the engine is restarted without a sufficient cooling period after the stop of the internal combustion engine. Since the situation of starting is likely to occur, the opportunity for occurrence of the pre-ignition described above increases.

  In the third and subsequent compression strokes after the start of the internal combustion engine, the cold air sucked into the combustion chamber from the intake passage is compressed in the compression stroke, so the temperature of the gas in the combustion chamber during the compression stroke is It does not become too high, and the possibility of occurrence of the pre-ignition is low.

  In the first compression stroke after the start of the internal combustion engine or the second compression stroke, the pressure in the combustion chamber may be higher than the pressure in the combustion chamber in the compression stroke during the normal combustion operation of the internal combustion engine. It has been confirmed, and this also causes pre-ignition. Hereinafter, the reason why the pressure in the combustion chamber is increased in the first compression stroke after the start of starting and the second compression stroke will be described.

  During normal combustion operation before the start of the stop in the internal combustion engine, that is, during idling operation, the pressure in the combustion chamber is large when the piston moves in the direction of expanding the combustion chamber during the intake stroke and the intake valve is open. The air pressure is lower than the atmospheric pressure (negative pressure), and air is sucked from the intake passage into the combustion chamber. Thereafter, the intake valve is closed while the piston is moving in the direction of expanding the combustion chamber, and the compression stroke is started. In the initial stage of the compression stroke, the pressure in the combustion chamber becomes lower than the atmospheric pressure (negative pressure) by the movement of the piston in the direction of expanding the combustion chamber. Therefore, when the internal combustion engine is completely stopped, the cylinder that becomes the compression stroke for the first time after the start of the next start that becomes the initial compression stroke, and the cylinder that becomes the second compression stroke after the start of the next time that becomes the initial of the intake stroke, The pressure in the combustion chamber is lower than atmospheric pressure.

  However, when a certain amount of time (for example, 1 or 2 seconds) elapses after the engine stop is completed, in each cylinder, gas enters the combustion chamber from around the engine valve or the piston ring, and the pressure in the combustion chamber starts from a negative pressure state. Rise to atmospheric pressure. In such a state, when the internal combustion engine is started and the compression of the gas in the combustion chamber is started in each cylinder, the pressure in the combustion chamber has increased from the negative pressure state to the atmospheric pressure at that time. The pressure in the combustion chamber after the start of compression becomes higher than the pressure in the combustion chamber during normal combustion operation of the internal combustion engine.

In view of the above, in an internal combustion engine that reaches the first explosion in the first compression stroke after the start of the start or the second compression stroke, the engine will be started without a sufficient cooling period after the stop of the internal combustion engine is completed. Then, preignition may occur due to the high temperature of the gas in the combustion chamber during the compression stroke and the high pressure in the combustion chamber. Therefore, as shown in Patent Document 1, a cooling device that is driven by a driving source different from the internal combustion engine and cools the engine with cooling water is provided, and the cooling water temperature that becomes a value corresponding to the engine temperature when the engine is stopped is increased. When the temperature is higher than the predetermined value, it is considered that the cooling device is driven until the cooling water temperature becomes lower than the predetermined value while the engine is stopped. In this case, since the engine temperature is lowered while the engine is stopped by setting the predetermined value to a low value, it is possible to suppress the occurrence of pre-ignition in the cylinder that reaches the first explosion after the start of the next engine start.
JP 2001-182580 A (paragraphs [0015], [0023], [0027], [0028] and FIG. 2)

  As described above, it is possible to suppress the occurrence of pre-ignition at the start of the next start of the internal combustion engine by driving the cooling device until the cooling water temperature becomes lower than a predetermined value while the engine is stopped to cool the internal combustion engine. It will be possible. However, in order to accurately suppress pre-ignition at the start of engine start, the predetermined value needs to be set appropriately.

  Here, for a cylinder that reaches the first explosion after the start of the next engine start after the completion of the engine stop, the closer the piston position in the cylinder at the completion of the engine stop is to the bottom dead center, the compression at the time of the first explosion. The temperature of the gas in the combustion chamber and the pressure in the combustion chamber during the stroke increase, and preignition is likely to occur. This is because, as the piston position at the completion of engine stop in the cylinder is closer to bottom dead center, the amount of gas warmed up in the combustion chamber during engine stop increases, and the negative pressure in the combustion chamber at completion of engine stop increases. This is because the amount of increase in the pressure in the combustion chamber to the atmospheric pressure that occurs until the engine starts is increased. For this reason, it is assumed that the piston temperature of the cylinder at the time of completion of the engine stop is closest to the bottom dead center, and the engine temperature can be lowered while the engine is stopped to a value that does not cause preignition at the start of the engine start. It is conceivable to set the predetermined value and thereby avoid the pre-ignition at the start of engine start.

  However, when the predetermined value is set in this way, the occurrence of pre-ignition is suppressed when the piston position of the cylinder at the completion of the engine stop is closer to the top dead center than the position closest to the bottom dead center. In doing so, the internal combustion engine is cooled more than necessary. This is because when the piston position is near the top dead center, the gas in the combustion chamber during the compression stroke when the first explosion is started after the start of the engine is compared to when the piston is near the bottom dead center. This is because the temperature and the pressure in the combustion chamber do not increase, and the ease of pre-ignition is reduced. As described above, when the internal combustion engine is cooled more than necessary, energy for driving the cooling device is wasted, and the cooling device is driven longer than necessary while the engine is stopped. Will give the person a sense of incongruity.

  The present invention has been made in view of such circumstances, and its purpose is to suppress excessive cooling of the internal combustion engine while the engine is stopped while accurately suppressing pre-ignition at the start of engine start. It is an object of the present invention to provide a cooling control device for an internal combustion engine that can be used.

In the following, means for achieving the above object and its effects are described.
In order to achieve the above object, the invention according to claim 1 is applied to an internal combustion engine that undergoes an initial explosion in one of a first compression stroke and a second compression stroke after the start of engine start. Is a cooling device that is driven by another drive source to cool the engine, and at the completion of the stop of the internal combustion engine and after that, the engine temperature is higher than a predetermined value that may cause preignition at the start of the engine An internal combustion engine cooling control apparatus comprising: a control means for driving the cooling apparatus, and further comprising a setting means for variably setting the predetermined value according to a crank angle at the time of completion of the stop of the internal combustion engine, If the crank angle at the completion of the engine stop is the crank angle at which the piston position of the cylinder that will hit the first explosion after the next engine start is close to the top dead center, the crank angle at the completion of the engine stop will be the next time Than when the piston position of the cylinder before the first combustion after the engine starting operation is a crank angle which is a position of the bottom dead center toward, and are set as the predetermined value to a higher value.

  The compression stroke at which the first explosion occurs after the start of the engine when the crank angle at the completion of the stop of the internal combustion engine is the crank angle at which the piston position of the cylinder that reaches the first explosion after the start of the next engine start is closest to the bottom dead center The pre-ignition is most likely to occur. Also, the crank angle at the completion of the stop of the internal combustion engine is a crank angle that is closer to the top dead center than when the piston position of the cylinder that reaches the first explosion after the next start of the engine is closest to the bottom dead center. Certainly, the ease of occurrence of pre-ignition in the compression stroke that reaches the first explosion after the start of the engine is reduced. According to the above configuration, when the crank angle at the completion of the engine stop is the crank angle at which the piston position of the cylinder that reaches the first explosion after the next engine start is the position closest to the bottom dead center, the predetermined value is set to the next engine By reducing the value to a value at which pre-ignition does not occur at the start of starting, occurrence of the pre-ignition can be accurately suppressed. Further, when the crank angle at the completion of the engine stop is the crank angle at which the piston position of the cylinder that reaches the first explosion after the next engine start is the position closer to the top dead center than the position closest to the bottom dead center, the predetermined value However, since the value is higher than the above-described value, it is possible to suppress the cooling of the internal combustion engine more than necessary while the engine is stopped.

  According to a second aspect of the present invention, in the first aspect of the invention, the setting means is such that the crank angle when the stop of the internal combustion engine is completed is a position where the piston of the cylinder that reaches the first explosion after the next engine start is close to the top dead center. The predetermined value is gradually set higher as the crank angle becomes smaller.

  According to the above configuration, when the crank angle at the completion of the engine stop is the crank angle at which the cylinder of the first explosion after the next engine start is located closest to the bottom dead center, the predetermined value is set to start the next engine start. Occasionally, the occurrence of pre-ignition can be accurately suppressed by reducing the value to a value at which pre-ignition does not occur. Furthermore, the crank angle at the time when the engine stop is completed is set to a value higher than the above-mentioned value as the crank angle at which the piston of the cylinder that reaches the first explosion after the next engine start becomes closer to the top dead center. It can be changed gradually. Accordingly, it is possible to more appropriately achieve both the suppression of the unnecessary cooling of the internal combustion engine while the engine is stopped and the suppression of the pre-ignition at the next engine start.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the cooling device includes an electric pump that supplies cooling water to the internal combustion engine, and the control means is configured to control the engine temperature with respect to the predetermined value. The higher the flow rate, the greater the flow rate of the electric pump.

  According to the above configuration, the cooling of the internal combustion engine with the cooling water while the engine is stopped is performed more strongly as the engine temperature is higher than the predetermined value, and is weakened as the engine temperature approaches the predetermined value. Therefore, the engine temperature when the engine is stopped is made to be less than the predetermined value quickly and wastefully without driving the electric pump.

  According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the cooling device includes an electric pump that circulates the cooling water so as to pass through the internal combustion engine, and an electric fan that cools the cooling water by blowing air. The control means increases the air blowing amount of the electric fan as the engine temperature is higher than the predetermined value.

  According to the above configuration, the cooling of the internal combustion engine with the cooling water while the engine is stopped is performed more strongly as the engine temperature is higher than the predetermined value, and is weakened as the engine temperature approaches the predetermined value. Therefore, the engine temperature when the engine is stopped is made to be less than the predetermined value quickly and without wastefully driving the electric fan.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the combustion operation of the internal combustion engine is automatically stopped upon establishment of an automatic stop condition during the execution of the combustion operation. The combustion operation is automatically restarted when the automatic start condition is satisfied while the combustion operation is stopped.

  In an internal combustion engine that automatically stops and restarts the combustion operation, there are many opportunities to start the engine without taking much time after the completion of the engine stop, and there are also many opportunities for occurrence of pre-ignition when starting the engine. However, while accurately suppressing the occurrence of such pre-ignition, the internal combustion engine during the engine stop when the piston position of the cylinder is at a crank angle closer to the top dead center than the bottom dead center when the engine stop is completed. Cooling more than necessary can be suppressed.

[First Embodiment]
Hereinafter, a first embodiment in which the present invention is applied to an in-line four-cylinder engine that is mounted on an automobile and automatically stopped and restarted will be described with reference to FIGS.

  In the engine 1 shown in FIG. 1, fuel is injected from the fuel injection valve 2 into the combustion chamber 3 during operation, and the piston 4 reciprocates due to combustion of fuel in the combustion chamber 3. The crankshaft 5 that is the output shaft rotates. The rotation of the crankshaft 5 is transmitted to the camshaft 6 via a belt or the like, and the opening and closing of engine valves such as the intake valve 7 and the exhaust valve 8 of the engine 1 is performed through the rotation of the camshaft 6. The strokes of the combustion cycle performed during the operation of the engine 1, that is, the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke are performed in the order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder, respectively. It will be. When starting the self-sustaining operation (combustion operation) of the stopped engine 1, fuel injection is performed in a state where the crankshaft 5 is forcibly rotated (cranking) through driving of the starter 15 connected to the crankshaft 5. Fuel injection from the valve 2 to the combustion chamber 3 is performed.

Next, a device for grasping the crank angle of the engine 1 will be described.
A rotor 9 made of a magnetic material is fixed to the crankshaft 5 of the engine 1, and a large number of protrusions 9 a are formed on the outer edges of the rotor 9 at equal intervals in the circumferential direction. Two crank position sensors 11 and 12 are provided in the vicinity of the rotor 9. When the rotor 9 rotates together with the crankshaft 5, signals corresponding to the protrusions 9 a of the rotor 9 are output from the crank position sensors 11 and 12. The crank position sensors 11 and 12 can output a pulse signal corresponding to the protrusion 9a even when the rotational speed of the rotor 9 is extremely slow, such as immediately before the stop of the engine 1 is completed. For example, a magnetoresistive element (MRE) sensor is used. The relative positions of the crank position sensor 11 and the crank position sensor 12 in the circumferential direction of the rotor 9 are set so that the phases of the pulse signals output from the sensors 11 and 12 are shifted from each other. Yes.

  On the other hand, a rotor 13 made of a magnetic material is also fixed to the camshaft 6, and a plurality of protrusions 13 a having different circumferential lengths are formed at different intervals on the outer edge of the rotor 13. A cam position sensor 14 is provided in the vicinity of the rotor 13. When the rotor 13 rotates together with the camshaft 6, a signal corresponding to each protrusion 13 a of the rotor 13 is output from the cam position sensor 14. The cam position sensor 14 can output a pulse signal corresponding to the protrusion 13a even when the rotational speed of the rotor 13 is extremely slow, such as immediately before the stop of the engine 1 is completed. For example, a magnetoresistive element (MRE) sensor is used similarly to the crank position sensors 11 and 12.

  Based on the pulse signals from the crank position sensors 11 and 12 and the pulse signal from the cam position sensor 14, the crank angle of the engine 1 is grasped. Further, regarding the determination of the crank angle, the MRE that can output the pulse signals corresponding to the protrusions 9a, 10a, and 13a of the rotors 9, 10, and 13 immediately before the stop of the engine 1 as the sensors 11, 12, and 14 described above. Since the sensor is used, it is possible immediately before the stop of the engine 1 is completed. Therefore, it is possible to grasp the crank angle when the stop of the engine 1 is completed based on the pulse signals from the crank position sensors 11 and 12 and the pulse signal from the cam position sensor 14.

Next, a cooling device for cooling the engine 1 will be described.
This cooling device includes a circulation path 16 for flowing cooling water to the engine 1. An electric water pump 17 and a radiator 18 are provided on the circulation path 16, and an electric cooling fan 19 is provided in the vicinity of the radiator 18. The electric water pump 17 and the electric cooling fan 19 of such a cooling device are driven by a motor through power feeding from the battery 20 of the automobile, and are driven by a driving source different from the engine 1.

  When the electric water pump 17 is driven in the cooling device, a flow is generated in the cooling water in the circulation path 16, and the cooling water circulates through the circulation path 16 and passes through the radiator 18 and the engine 1. The cooling water is cooled through heat exchange with the outside air when passing through the radiator 18. When the electric cooling fan 19 is driven and wind is sent toward the radiator 18, heat exchange between the cooling water and the outside air in the radiator 18 is promoted. The cooling water cooled by the radiator 18 takes heat through the heat exchange with the engine 1 when passing through the engine 1 and cools the engine 1.

  The cooling efficiency of the engine 1 by this cooling device is increased as the flow rate of the electric water pump 17 is increased and the amount of cooling water passing through the engine 1 is increased, and the blowing amount of the electric cooling fan 19 is increased. As the amount of heat exchange between the cooling water and the outside air in the radiator 18 is increased, the temperature is increased.

Next, an electrical configuration of the cooling control device that drives and controls the cooling device will be described.
The cooling control device includes an electronic control device 21 that controls driving of various mounted devices such as an engine 1 in an automobile. The electronic control unit 21 includes a CPU that executes various arithmetic processes related to the drive control of the various mounted devices, a ROM that stores programs and data necessary for the control, a RAM that temporarily stores CPU calculation results, and the like. Input / output ports for inputting / outputting signals to / from the.

  In addition to the signals from the crank position sensors 11 and 12 and the cam position sensor 14 described above, an accelerator position sensor 22 for detecting the accelerator operation amount, a vehicle speed sensor 23 for detecting the vehicle speed, Various sensors such as a water temperature sensor 26 for detecting the cooling water temperature in the circulation path 16 are connected. Further, the input port of the electronic control unit 21 includes a brake switch 24 that detects whether or not the brake pedal is depressed, and four types such as “off”, “accessory”, “on”, and “start” by the driver of the automobile. An ignition switch 25 or the like that is switched to one of the two switching positions and outputs a signal corresponding to the current switching position is also connected. On the other hand, to the output port of the electronic control unit 21, drive circuits such as the fuel injection valve 2, the electric water pump 17, the electric cooling fan 19, and the starter 15 are connected.

  The electronic control device 21 outputs a command signal to the drive circuit of each device connected to the output port in accordance with the driving state of the vehicle and the engine 1 that is grasped from the detection signals input from the sensors. . Thus, control of fuel injection from the fuel injection valve 2, starter 15 drive control at engine start, automatic stop / restart control of the engine 1, drive control of the electric water pump 17 and the electric cooling fan 19 in the cooling device, etc. These various controls are implemented by the electronic control unit 21.

  Here, the cooling of the engine 1 performed through the drive control of the electric water pump 17 and the electric cooling fan 19 by the electronic control device 21 is performed as follows, for example. That is, during normal combustion operation in the engine 1, the cooling water temperature in the circulation path 16 detected by the water temperature sensor 26 is used as a value corresponding to the engine temperature, and the cooling water temperature becomes a target value (for example, 95 ° C.) or less. Thus, the electric water pump 17 and the electric cooling fan 19 are driven. When the cooling water temperature becomes equal to or lower than the target value, the driving of the electric water pump 17 and the electric cooling fan 19 is stopped. Thus, the engine 1 is appropriately cooled during normal combustion operation of the engine 1 so that the engine temperature does not rise excessively.

Next, start and stop of the engine 1 performed through drive control of the fuel injection valve 2 and the starter 15 by the electronic control device 21 will be described.
Such starting and stopping of the engine 1 are performed based on the operation of the ignition switch 25 by the driver. In addition to starting and stopping as described above, the engine 1 is also automatically stopped and restarted in response to an output request to the engine 1 for the purpose of improving the fuel consumption of the engine 1. Hereinafter, procedures for starting and stopping the engine 1 will be described separately for [starting and stopping based on the operation of the ignition switch] and [automatic stopping and restarting based on the presence or absence of the engine output request].

[Starting and stopping based on ignition switch operation]
When the ignition switch 25 is sequentially switched from “off” to “accessory”, “on”, and “start” by the driver while the engine is stopped, the engine 1 starts when the switch 25 is switched to “start”. A command is made. Based on this start command, the starter 15 is driven to start cranking of the engine 1, and fuel is injected and supplied from the fuel injection valve 2 to the combustion chamber 3 during the cranking. And the engine 1 will be started start-up by burning the fuel in the combustion chamber 3 and operating the engine 1 independently. Further, when the ignition switch 25 is sequentially switched from “ON” to “ACCESSORY” and “OFF” by the driver during engine operation, the engine 1 stop command is issued when the switch 25 is switched to “ACCESSORY”. Is made. Based on this stop command, the combustion of fuel in the combustion chamber 3 is stopped, and the engine 1 is started to stop. Thereafter, the engine rotation speed decreases from the idle rotation speed to “0”, and the stop of the engine 1 is completed.

[Automatic stop and restart based on engine output request]
During engine operation, when there is no output request of the engine 1, combustion of fuel in the combustion chamber 3 is stopped, and the engine 1 is automatically stopped. The presence or absence of an output request to the engine 1 is, for example, (A) the accelerator depression amount is “0”, (B) the brake is depressed, (C) the vehicle speed is less than a predetermined value a close to “0”. Are determined based on whether or not all the conditions such as. When all of the conditions (A) to (C) are satisfied, it is determined that there is no output request to the engine 1, in other words, it is not necessary to operate the engine 1, and a stop command for the engine 1 is issued. The engine 1 is automatically stopped. In addition, when the engine 1 is automatically stopped as described above, an output request to the engine 1 is generated, that is, when one or more of the above conditions (A) to (C) are not satisfied. The engine 1 is instructed to start. Based on this start command, the starter 15 is driven to start cranking of the engine 1, and fuel is injected and supplied from the fuel injection valve 2 to the combustion chamber 3 during the cranking. The engine 1 is automatically restarted by burning the fuel in the combustion chamber and starting the self-sustaining operation of the engine 1.

  As for the start of the engine 1, in recent years, the start may be completed early after the start of the start, whether it is due to the operation of the ignition switch 25 or automatically according to the output request of the engine 1. It is requested. In order to meet such demands, the engine 1 burns fuel in the cylinder that is first in the compression stroke after the start of the start, and the first explosion after the start of the start is reached during the compression stroke. Here, FIG. 2A shows a fuel injection mode and a fuel combustion mode in the first to fourth cylinders of the engine 1 from the start of the stop of the engine 1 to the start of the next start.

  As can be seen from this figure, in the engine 1, fuel injection from the fuel injection valve 2 to the combustion chamber 3 is performed during the intake stroke, and the fuel in the combustion chamber 3 is combusted in the subsequent compression stroke to the expansion stroke. Transition. In the example of FIG. 2A, after the fuel injection from the fuel injection valve 2 to the combustion chamber 3 is performed in the intake stroke of the first cylinder, the engine 1 is stopped in the state where the same cylinder shifts to the compression stroke. (Timing T1). Thereafter, when the engine 1 is instructed to start (timing T3), the engine 1 is cranked and started to start, and the fuel present in the combustion chamber 3 in the first cylinder that is first subjected to the compression stroke after the start is started. Burns, and the first explosion after the start of the engine 1 starts. As described above, the engine 1 can be operated independently at an early stage after the start of the engine by starting the first explosion in the cylinder that is first in the compression stroke after the start of the engine 1 is started.

  By the way, in the first compression stroke after the start of the engine 1, the temperature of the gas in the combustion chamber 3 and the pressure in the combustion chamber 3 are changed in the combustion chamber 3 in the compression stroke during the normal combustion operation of the engine 1. Compared to the temperature of the gas and the pressure in the combustion chamber 3, it becomes higher for the reason described in the “Background Art” column. For this reason, there is a possibility that self-ignition (pre-ignition) of the fuel in the combustion chamber 3 may occur in the cylinder that first reaches the compression stroke after starting.

  For this reason, the cooling of the engine 1 by the cooling device described above is performed not only at the time of normal combustion operation but also at the completion of the stop of the engine 1 and thereafter. Specifically, as shown in FIG. 2B, the cooling water temperature in the circulation path 16 representing the temperature of the engine 1 is determined in advance at and after the completion of the stop of the engine 1 (after the timing T1). When it is equal to or greater than the threshold value, the electric water pump 17 is driven as shown in FIG. 2 (c), and the electric cooling fan 19 is driven as shown in FIG. 2 (d). As a result, the engine 1 is cooled, and the occurrence of pre-ignition in the first compression stroke after the start of the next start is suppressed. Thereafter, when the cooling water temperature becomes lower than the above threshold (timing T2), the electric water pump 17 and the electric cooling fan 19 are stopped, and the cooling of the engine 1 by the cooling device is stopped.

  Here, the ease of occurrence of pre-ignition in the cylinder that is initially in the compression stroke after the start of the engine 1 is determined by the position of the piston 4 in each cylinder at the completion of the stop of the engine 1 immediately before the start of the start. What changes depending on the situation is as described in the column [Problems to be solved by the invention]. That is, when the position of the piston 4 is at the bottom dead center as shown in FIG. 3A, the temperature of the gas in the combustion chamber 3 and the pressure in the combustion chamber 3 in the first compression stroke. Is the highest, so the pre-ignition is most likely to occur. Further, when the position of the piston 4 is closer to the top dead center than the bottom dead center as shown in FIG. 3B, the closer to the top dead center, the more the combustion in the first compression stroke. Since the temperature of the gas in the chamber 3 and the pressure in the combustion chamber 3 are lowered, the ease of occurrence of the pre-ignition gradually decreases. Therefore, if the threshold value is set to a low value so that the preignition can be avoided on the assumption that the position of the piston 4 is at the bottom dead center, the preignition can be accurately suppressed.

  However, when the actual position of the piston 4 is closer to the top dead center than the bottom dead center, the threshold value is too low to accurately suppress the pre-ignition, and when the stop of the engine 1 is completed. And after that, the engine 1 is cooled more than necessary by driving the cooling device. As described above, as the engine 1 is cooled more than necessary, power is wasted for driving the electric water pump 17 and the electric cooling fan 19 of the cooling device. Furthermore, since it takes a long time to lower the cooling water temperature of the engine 1 below the threshold value, the drive stop timing (T2 in FIG. 2) of the electric water pump 17 and the electric cooling fan 19 is delayed, and this is the operation. Cause discomfort to the person.

  Therefore, in the present embodiment, the above-described threshold value is variably set according to the crank angle when the stop of the engine 1 is completed. More specifically, when the crank angle at the completion of the stop of the engine 1 is the crank angle at which the position of the piston 4 of the cylinder that is first in the compression stroke after the start of the next start is the bottom dead center, the threshold value is set to the lowest value. Therefore, a value (cooling water temperature) that can accurately suppress the occurrence of pre-ignition in the cylinder at the start of the next start is set. Further, when the crank angle at the completion of the stop of the engine 1 is the crank angle at which the position of the piston 4 of the cylinder that is initially in the compression stroke after the start of the next start is a position closer to the top dead center than the bottom dead center, The threshold value is gradually set to a higher value as the crank angle is such that the position of the piston 4 is closer to the top dead center.

  Therefore, when the stop of the engine 1 is completed, the position of the piston 4 in the cylinder that is first subjected to the compression stroke after the start of the next start has the relationship as shown in FIG. That is, when the position of the piston 4 is at the bottom dead center, the threshold value becomes a low value that can accurately suppress the pre-ignition in the cylinder when the next start is completed. When the position of the piston 4 is closer to the top dead center than the bottom dead center, the threshold value is gradually changed to a higher value as the position of the piston 4 is closer to the top dead center. For this reason, the threshold value does not become too low to accurately suppress the occurrence of pre-ignition in the cylinder at the next engine start, and the cooling device is driven when the engine 1 is stopped and thereafter. The engine 1 is not cooled more than necessary.

  As described above, it is possible to suppress the cooling of the engine 1 more than necessary by the cooling device while the engine is stopped while accurately suppressing the occurrence of pre-ignition in the cylinder at the next engine start. Will be able to avoid.

  Next, the drive control procedure of the cooling device will be described with reference to the flowchart of FIG. 5 showing the cooling control routine. The cooling control routine is periodically executed through the electronic control device 21 by, for example, a time interruption every predetermined time.

  In this routine, when the stop of the engine 1 is completed (S101: YES), the crank angle at the completion of the engine stop is detected based on signals from the crank position sensors 11, 12 and the cam position sensor 14, and the crank angle is detected. Based on the above, the above-mentioned threshold value is variably set (S102). Subsequently, it is determined whether or not the engine 1 is in a stopped state (S103). If the determination is negative, the engine 1 is performing a normal combustion operation, and the electric water pump 17 and the electric cooling fan 19 are set so that the cooling water temperature is equal to or lower than the target value (95 ° C. in this embodiment). Ordinary cooling control for controlling the driving is performed (S109).

  On the other hand, if a negative determination is made in step S103, it means that the engine 1 has been stopped and is stopped thereafter. In this case, cooling is performed while the engine is stopped on condition that the cooling water temperature is equal to or higher than the threshold value (S104: YES) and the remaining battery level, which is the amount of electricity stored in the battery 20, is equal to or higher than the lower limit value (S105: YES). Processing for driving the apparatus (S106, S107) is executed. In addition, the said battery remaining amount is calculated | required based on the charge amount of the battery 20 by the generator mounted in the motor vehicle, the discharge amount from the battery 20 at the time of operating the electric equipment mounted in the motor vehicle, etc.

  As a process for driving the cooling device while the engine is stopped, first, the temperature difference of the cooling water temperature with respect to the threshold value is calculated (S106), and then the flow rate of the electric water pump 17 and the electric cooling fan 19 according to the temperature difference. Is controlled (S107). More specifically, as the temperature difference becomes larger, the drive control of the pump 17 is performed so that the flow rate of the electric water pump 17 gradually increases as shown in FIG. 6, and the electric drive as shown in FIG. The drive control of the cooling fan 19 is performed so that the air flow rate of the cooling fan 19 gradually increases. Thereby, the cooling of the engine 1 by the cooling water while the engine is stopped is performed more powerfully as the cooling water temperature is higher than the threshold value, and is weakened as the cooling water temperature approaches the threshold value.

  As a result of cooling the engine 1 with such cooling water, when the cooling water temperature representing the temperature of the engine 1 becomes lower than the threshold (S105), the driving of the electric water pump 17 and the electric cooling fan 19 is stopped ( S108).

According to the embodiment described in detail above, the following effects can be obtained.
(1) When the crank angle at the completion of the stop of the engine 1 is the crank angle at which the piston 4 of the cylinder that is initially in the compression stroke after the start of the next start is located at the bottom dead center, the threshold value is Since the cooling water temperature is set so that no pre-ignition occurs in the cylinder, the occurrence of the pre-ignition can be accurately suppressed. Further, when the crank angle at the completion of the stop of the engine 1 is the crank angle at which the position of the piston 4 of the cylinder that is initially in the compression stroke after the start of the next start is a position closer to the top dead center than the bottom dead center, The threshold value is set to a value higher than the above value as the position of the piston 4 is closer to the top dead center. Accordingly, while the occurrence of the pre-ignition is appropriately suppressed, it is possible to suppress the threshold value from being too low for accurately suppressing the pre-ignition, and it is necessary for the engine 1 when the engine 1 is stopped. The above cooling can be suppressed.

  (2) When the stopped engine 1 is cooled, if the cooling water temperature is higher than the threshold value, the flow rate of the electric water pump 17 and the air blowing amount of the electric cooling fan 19 are increased. The flow rate of the water pump 17 and the air blowing amount of the electric cooling fan 19 were gradually reduced. For this reason, the cooling of the stopped engine 1 is performed more strongly as the cooling water temperature is higher than the threshold value, and is weakened as the cooling water temperature approaches the threshold value. Therefore, the cooling water temperature is set to be lower than the threshold value quickly and wastefully without driving the electric water pump 17 and the electric cooling fan.

  (3) In the engine 1 that automatically stops and restarts the combustion operation, there are many opportunities for starting to start without much time after the completion of the stop of the engine 1, and there are also many opportunities for occurrence of pre-ignition at the start of the start. Become. However, it is possible to suppress the cooling of the stopped engine 1 more than necessary while appropriately suppressing the occurrence of such pre-ignition.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
In this embodiment, in order to complete the start at an early stage after the start of the engine 1, the fuel is burned in the cylinder that becomes the second compression stroke after the start of the start, and the first explosion after the start of the start is reached during the compression stroke. It is what I did.

  FIG. 8A is a time chart showing the fuel injection mode and the fuel combustion mode in the first to fourth cylinders of the engine 1 from the start of the stop of the engine 1 to the start of the next start in this embodiment. is there. In the example of this figure, the engine 1 has been stopped in a state where the first cylinder has shifted from the intake stroke to the compression stroke, and the third cylinder has shifted from the exhaust stroke to the intake stroke (timing T1). . In this embodiment, fuel injection in the intake stroke immediately before completion of the stop is not performed in the cylinder that is in the compression stroke when the stop of the engine 1 is completed (the first cylinder in FIG. 8A). After that, when the engine 1 is instructed to start (timing T3), the engine 1 is cranked and started to start, and the cylinder that first enters the intake stroke after the start is started (the third cylinder in FIG. 8A). Thus, fuel injection from the fuel injection valve 2 to the combustion chamber 3 is performed. When the third cylinder reaches the compression stroke, that is, when the second compression stroke after starting starts, the fuel existing in the combustion chamber 3 of the third cylinder burns, and the engine 1 starts. It will be the first explosion after the start.

  By the way, even in the second compression stroke after the start of the engine 1, the temperature of the gas in the combustion chamber 3 and the pressure in the combustion chamber 3 are in the combustion chamber 3 in the compression stroke during the normal combustion operation of the engine 1. Compared to the temperature of the gas and the pressure in the combustion chamber 3, it becomes higher for the reason described in the “Background Art” column. For this reason, pre-ignition in the combustion chamber 3 may occur even in the cylinder that reaches the compression stroke on the second day after starting. In order to suppress such pre-ignition, the cooling device is driven so that the cooling water temperature of the engine 1 becomes lower than the threshold value as shown in FIGS. 8B to 8D when the stop of the engine 1 is completed and thereafter.

  With respect to the above threshold value, the crank angle at the completion of the stop of the engine 1 is controlled so as to suppress the unnecessary cooling of the engine 1 by the cooling device while the engine is stopped while accurately suppressing the occurrence of pre-ignition at the start of the start. It is variably set accordingly.

  More specifically, the position of the piston 4 of the cylinder in which the crank angle when the stop of the engine 1 is completed becomes the second compression stroke after the start of the next start is the position closest to the bottom dead center as shown in FIG. When the crank angle is, the threshold value is set to the lowest value (cooling water temperature) that can accurately suppress the occurrence of pre-ignition in the cylinder at the start of the next start. This is because when the position of the piston 4 is closest to the bottom dead center as shown in FIG. 9A, the temperature of the gas in the combustion chamber 3 and the combustion chamber in the second compression stroke. This is because the pressure within 3 is the highest and the pre-ignition is most likely to occur.

  Further, the position of the piston 4 of the cylinder in which the crank angle when the stop of the engine 1 is completed becomes the second compression stroke after the start of the next start is the position closest to the bottom dead center as shown in FIG. When the crank angle is closer to the top dead center than 9 (a)), the threshold value is gradually set higher as the piston 4 is closer to the top dead center. To do. This is close to the top dead center when the position of the piston 4 is closer to the top dead center than the position closest to the bottom dead center (FIG. 9A) as shown in FIG. 9B. This is because the temperature of the gas in the combustion chamber 3 and the pressure in the combustion chamber 3 in the second compression stroke are lower as the position is higher, and the ease of occurrence of the pre-ignition is gradually reduced. is there.

  Accordingly, the position of the piston 4 in the cylinder that becomes the second compression stroke after the start of the next start when the stop of the engine 1 is completed has the relationship as shown in FIG. That is, when the position of the piston 4 is closest to the bottom dead center, the threshold value is a low value that can accurately suppress the pre-ignition in the cylinder when the next start is completed. When the position of the piston 4 is closer to the top dead center than the position closest to the bottom dead center, the threshold value gradually increases to a higher value as the position of the piston 4 becomes closer to the top dead center. Can be changed. For this reason, the threshold value does not become too low to accurately suppress the occurrence of pre-ignition in the cylinder at the next engine start, and the cooling device is driven when the engine 1 is stopped and thereafter. The engine 1 is not cooled more than necessary.

According to the embodiment described in detail above, the following effects can be obtained.
(4) When the crank angle at the completion of the stop of the engine 1 is the crank angle at which the piston 4 of the cylinder that is in the second compression stroke after the start of the next start is located closest to the bottom dead center, the above threshold is the next start Since the cooling water temperature at which no pre-ignition is generated in the cylinder is set at the start, the occurrence of the pre-ignition can be accurately suppressed. Further, the crank angle when the stop of the engine 1 is completed is the crank angle at which the position of the piston 4 of the cylinder that becomes the second compression stroke after the start of the next start is closer to the top dead center than the position closest to the bottom dead center. If the crank angle is such that the position of the piston 4 approaches the top dead center, the threshold value is set to a value higher than the above-described value. Accordingly, while the occurrence of the pre-ignition is appropriately suppressed, it is possible to suppress the threshold value from being too low for accurately suppressing the pre-ignition, and it is necessary for the engine 1 when the engine 1 is stopped. The above cooling can be suppressed.

(5) The same effects as (2) and (3) of the first embodiment can be obtained.
In addition, each said embodiment can also be changed as follows, for example.
In the first embodiment, the threshold value is linearly changed as shown in FIG. 4 in accordance with the change in the piston position in the cylinder that first reaches the compression stroke after the start of the next start when the engine stop is completed. Instead of this, the threshold value may be changed stepwise in accordance with the change in the piston position. For example, the threshold value may be changed in two steps as shown in FIG. 11 according to the change in the piston position, or may be changed in three steps or more. In this case, the same effect as (1) of the first embodiment can be obtained. In addition, if the threshold value is linearly changed according to the change in the piston position as in the first embodiment described above, the cooling of the engine 1 more than necessary while the engine 1 is stopped and the next engine are suppressed. There is an effect that it is possible to more appropriately achieve the suppression of the occurrence of pre-ignition in the cylinder at the start of 1.

  In the second embodiment, the threshold value is linearly changed as shown in FIG. 10 in accordance with the change in the piston position in the cylinder that reaches the second compression stroke after the start of the next start when the engine stop is completed. Instead of this, the threshold value may be changed stepwise in accordance with the change in the piston position. For example, the threshold value may be changed in two stages as shown in FIG. 12 according to the change in the piston position, or may be changed in three stages or more. In this case, the same effect as (4) of the second embodiment can be obtained. In addition, if the threshold value is linearly changed according to the change in the piston position as in the second embodiment, the cooling of the engine 1 more than necessary during the stop of the engine 1 and the next engine are suppressed. There is an effect that it is possible to more appropriately achieve the suppression of the occurrence of pre-ignition in the cylinder at the start of 1.

  The flow rate of the electric water pump 17 during the stop of the engine 1 does not necessarily need to be gradually changed according to the temperature difference of the cooling water temperature with respect to the threshold as shown in FIG. It may be changed to.

The flow rate of the electric water pump 17 may be fixed.
The amount of air blown by the electric cooling fan 19 when the engine 1 is stopped does not necessarily need to be gradually changed according to the temperature difference as shown in FIG. 7, but is changed stepwise according to the temperature difference. May be.

-The ventilation volume of the electric cooling fan 19 may be fixed.
-Although the cooling water temperature in the circulation path 16 was used as a parameter showing the temperature of the engine 1, other parameters, such as the lubricating oil temperature of the engine 1, may be used instead.

  -Although this invention was applied to the engine 1 which stops and restarts automatically according to an output request | requirement, you may apply this invention to the engine in which a stop and start are performed only by the ignition switch 25 by a driver | operator.

Although the present invention is applied to the direct injection type engine 1 that injects fuel into the combustion chamber 3, the present invention may be applied to a port injection type engine that injects fuel into the intake port.
The present invention may be applied to engines of types other than four cylinders, such as in-line six cylinders, V-type six cylinders, and V-type eight cylinders.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the whole structure of the engine of 1st Embodiment, and its cooling device. (A)-(d) is a time chart which shows the change for every cylinder of each stroke of a combustion cycle, the change of cooling water temperature, the change of the drive state of an electric water pump, and the change of the drive state of an electric cooling fan. (A) And (b) is the schematic which shows the piston position in the cylinder which reaches a compression stroke first after the next starting start at the time of an engine stop completion. The graph which shows the change of the threshold value with respect to the change of the piston position in the said cylinder at the time of an engine stop completion. The flowchart which shows the execution procedure of the engine cooling control by a cooling device. The graph which shows the change of the flow volume of the electric water pump with respect to the change of the temperature difference of the cooling water temperature with respect to a threshold value. The graph which shows the change of the ventilation volume of the electric cooling fan with respect to the change of the temperature difference of the cooling water temperature with respect to a threshold value. (A)-(d) shows the change for every cylinder of each stroke of the combustion cycle in 2nd Embodiment, the change of cooling water temperature, the change of the drive state of an electric water pump, and the change of the drive state of an electric cooling fan. Time chart. (A) And (b) is the schematic which shows the piston position in the cylinder which reaches the 2nd compression stroke after the next starting start at the time of engine stop completion. The graph which shows the change of the threshold value with respect to the change of the piston position in the said cylinder at the time of an engine stop completion. The graph which shows the other example of the change of the threshold value with respect to the change of the piston position in the said cylinder at the time of an engine stop completion. The graph which shows the other example of the change of the threshold value with respect to the change of the piston position in the said cylinder at the time of an engine stop completion.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Fuel injection valve, 3 ... Combustion chamber, 4 ... Piston, 5 ... Crankshaft, 6 ... Camshaft, 7 ... Intake valve, 8 ... Exhaust valve, 9 ... Rotor, 9a ... Projection, 10 ... Rotor DESCRIPTION OF SYMBOLS 10a ... Projection, 11, 12 ... Crank position sensor, 13 ... Rotor, 13a ... Projection, 14 ... Cam position sensor, 15 ... Starter, 16 ... Circulation path, 17 ... Electric water pump (electric pump), 18 ... Radiator, DESCRIPTION OF SYMBOLS 19 ... Electric cooling fan (electric fan), 20 ... Battery, 21 ... Electronic control unit (control means, setting means), 22 ... Accelerator position sensor, 23 ... Vehicle speed sensor, 24 ... Brake switch, 25 ... Ignition switch, 26 ... Water temperature sensor.

Claims (5)

Cooling that is applied to an internal combustion engine that reaches the first explosion in either the first compression stroke or the second compression stroke after the start of engine startup, and that is driven by a drive source different from that internal combustion engine to cool the engine An internal combustion engine comprising: and a control means for driving the cooling device when the engine temperature is equal to or higher than a predetermined value that may cause pre-ignition at the time of starting the engine after the completion of the stop of the internal combustion engine In the cooling control device of
Setting means for variably setting the predetermined value according to a crank angle at the time of completion of stop of the internal combustion engine;
When the crank angle at the completion of the engine stop is a crank angle at which the piston position of the cylinder that reaches the first explosion after the next engine start is a position near the top dead center, the crank angle at the completion of the engine stop is The internal combustion engine cooling control apparatus according to claim 1, wherein the predetermined value is set to a higher value than when the piston position of the cylinder that reaches the first explosion after starting the engine is a crank angle at a position close to bottom dead center. The setting means increases the predetermined value gradually as the crank angle at the completion of the stop of the internal combustion engine is a crank angle at which the piston of the cylinder that reaches the first explosion after the next engine start becomes a position close to top dead center. The cooling control apparatus for an internal combustion engine according to claim 1, wherein The cooling device includes an electric pump that supplies cooling water to the internal combustion engine,
The internal combustion engine cooling control device according to claim 1 or 2, wherein the control means increases the flow rate of the electric pump as the engine temperature is higher than the predetermined value. The cooling device includes an electric pump that circulates cooling water so as to pass through the internal combustion engine, and an electric fan that cools the cooling water by blowing air.
The cooling control device for an internal combustion engine according to claim 1 or 2, wherein the control means increases the amount of air blown by the electric fan as the engine temperature is higher than the predetermined value. The internal combustion engine is automatically stopped when the automatic stop condition is satisfied during execution of the combustion operation, and is automatically restarted when the automatic start condition is satisfied while the combustion operation is stopped. The cooling control device for an internal combustion engine according to any one of claims 1 to 4.

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