JP2003239747A - Internal combustion engine controlling degree of cooling based on knock index - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively improve engine performance by adequately cooling an internal combustion engine. <P>SOLUTION: An knock index representing easiness of generation of knocking is stored so as to accommodate for operation testing of the internal combustion engine. When the internal combustion engine is operated, operation conditions are detected, the knock index corresponding to detected operation conditions is found, and the degree of cooling of the internal combustion engine is varied based on the obtained knock index. By controlling the degree of cooling based on the knock index found according to the operation conditions like this, the generation of knocking is avoided by adequately cooling the internal combustion engine. Thus, the output of the engine is increased, fuel consumption efficiency is enhanced, and engine performance is effectively improved. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for cooling an internal combustion engine, and more particularly to a technique for improving engine performance by appropriately cooling in consideration of easiness of knocking.

[0002]

2. Description of the Related Art Since an internal combustion engine is relatively small and can output a large amount of power,
It is widely used as a power source for various transportation means such as aircraft. These internal combustion engines generate heat by burning fuel in a combustion chamber, convert a part of the generated heat into mechanical work, and output it as power. Due to such an operating principle, it is almost inevitable that at least a part of the internal combustion engine is exposed to combustion heat and a part of the combustion heat flows in. When the temperature of the member rises, the mechanical strength of the member decreases, or seizure on the sliding surface easily occurs.Therefore, in order to avoid such a problem, the internal combustion engine is operated while being cooled. Is normal.

As a cooling method, various methods such as air cooling, oil cooling and water cooling have been proposed. In addition to having a large heat capacity, it has a good cooling performance without carbonization under any high temperature conditions. Therefore, the water cooling method of cooling with cooling water is widely used. In such a water cooling system, the internal combustion engine is cooled by circulating the cooling water while guiding the cooling water to a radiator to radiate heat appropriately so that the water temperature does not exceed the allowable temperature.

Further, in recent years, there has been proposed a technique for improving engine performance by appropriately controlling the cooling water temperature according to the load of the internal combustion engine (Japanese Patent Laid-Open No. 5-33213).
6, JP-A-10-131753, etc.). According to such a proposal, the cooling water temperature is controlled to a high temperature when the load is low and the temperature of the cooling water is low when the load is high. When the cooling water temperature is controlled to be high, the viscosity of the lubricating oil is reduced, so that the friction loss of the internal combustion engine is reduced and the fuel consumption efficiency of the engine can be improved. Also, at the time of high load where seizure is likely to occur, by controlling the cooling water temperature to a lower level, the viscosity of the lubricating oil is kept in an appropriate range to prevent seizure and to prevent knocking and improve engine performance. It is possible.

[0005]

However, even if the setting of the cooling water temperature is changed according to the load of the internal combustion engine, the effect of improving the engine performance such as the expected improvement of the fuel consumption efficiency or the increase of the engine output is achieved. Was not obtained in some cases.

The present invention has been made to solve the above-mentioned problems in the prior art, and it is possible to effectively improve the fuel consumption efficiency and the engine performance by appropriately cooling the internal combustion engine. The purpose is to provide technology.

[0007]

Means for Solving the Problems and Their Actions / Effects In order to solve at least a part of the above problems, the internal combustion engine of the present invention has the following constitution. That is, an internal combustion engine that converts the combustion heat generated in the combustion chamber into mechanical work and outputs the mechanical work, and a cooling unit that cools the internal combustion engine to remove the combustion heat that has flowed into the internal combustion engine. An operating condition detecting means for detecting an operating condition of the internal combustion engine,
Knock index as an index related to the likelihood of knocking, a knock index calculating means for calculating based on the detected operating conditions, and by controlling the cooling means based on the calculated knock index, The gist of the present invention is to provide a cooling control means for changing the cooling degree of the internal combustion engine.

The cooling method for an internal combustion engine of the present invention corresponding to the above internal combustion engine is a method for cooling an internal combustion engine, which converts combustion heat generated in a combustion chamber into mechanical work and outputs the mechanical work. Detecting the operating conditions of the internal combustion engine, a knock index as an index related to the likelihood of knocking is calculated based on the detected operating conditions, based on the calculated knock index, cooling the internal combustion engine The point is to change the degree.

In the internal combustion engine or the cooling method for the internal combustion engine having such a configuration, a knock index relating to the likelihood of knocking is calculated, and the cooling degree is changed based on the knock index. Therefore, for the reasons described below, it is possible to appropriately cool the internal combustion engine and effectively improve the engine performance.

As described above, if the temperature of the cooling water for cooling the internal combustion engine is set to be high, the viscosity of the lubricating oil is lowered, so that the friction loss of the engine can be reduced and the cooling water temperature can be reduced. If the setting is made higher, knocking is less likely to occur, so it is possible to improve fuel consumption efficiency or increase engine output. Thus, it is known that the engine performance can be improved by appropriately cooling the internal combustion engine. Therefore, in order to appropriately cool the internal combustion engine and improve the engine performance, the cooling water temperature is set to a high value when the load is low when knocking is unlikely to occur,
At high loads where knocking is likely to occur, the cooling water temperature is set low. However, according to the experience of the inventor of the present application, the load of the engine does not exactly match the likelihood of knocking. For this reason, if the cooling water temperature is changed according to the load, the cooling water temperature may be controlled to a higher temperature and knocking may occur despite the condition that knocking is likely to occur.

If the internal combustion engine is operated while knocking occurs, the engine will be damaged, so the ignition timing of the fuel must be delayed to avoid the occurrence of knocking. Delaying the ignition timing is realized by delaying the ignition timing in the spark ignition type internal combustion engine and by delaying the fuel injection timing in the compression ignition type internal combustion engine. In any type of internal combustion engine, there is an optimum value for the ignition timing, and if the ignition timing is delayed in order to avoid the occurrence of knocking, engine performance will deteriorate. Therefore, even if the cooling water temperature is changed according to the engine load, the effect of improving the engine performance may not be obtained as expected as a whole. It is considered that this is the reason why the engine performance cannot be improved as expected by switching the temperature of the cooling water according to the load of the internal combustion engine. In particular, since internal combustion engines mounted on automobiles, ships, aircrafts, etc., which output power to them, have large fluctuations in operating conditions, it is considered that such a tendency is remarkable.

On the other hand, in the internal combustion engine of the present invention and the cooling method of the present invention, the knock index, which is an index relating to the ease with which knocking occurs, is calculated based on the operating conditions of the internal combustion engine, and the calculated knock index is calculated. The cooling degree of the internal combustion engine is changed based on the above. Here, in calculating the knock index, the knock index is described as a function of the driving condition,
The knock index is not limited to the one in which the knock index is calculated by calculating the function value. It also includes those that seek indicators. If the degree of cooling is changed based on the knock index calculated in this way, it is possible to appropriately cool the internal combustion engine and avoid occurrence of knocking by previously obtaining an appropriate knock index according to operating conditions. Therefore, it is possible to obtain a sufficient improvement effect on the engine performance.

When the internal combustion engine is cooled by circulating the cooling liquid, the cooling degree of the internal combustion engine may be changed by changing the temperature of the cooling liquid. Alternatively, the cooling degree of the internal combustion engine may be changed by changing the flow rate of the cooling liquid. According to these methods, it is possible to change the cooling degree of the internal combustion engine simply and reliably. As the cooling liquid, a liquid such as water or oil, especially a liquid having a large heat capacity can be preferably used.

When changing the cooling degree of the internal combustion engine, the knock index may be compared with a predetermined threshold value, and the cooling degree of the internal combustion engine may be switched based on the magnitude relationship between the two values.

When the internal combustion engine is cooled by circulating the cooling liquid, the temperature of the cooling liquid is controlled to the first cooling liquid temperature when the knock index is smaller than the predetermined threshold value. However, when the knock index is larger than the predetermined threshold value, the second cooling liquid temperature may be controlled to be lower than the first cooling liquid temperature. Changing the coolant temperature in this manner is preferable because the degree of cooling of the internal combustion engine can be easily changed.

In such an internal combustion engine, at least the rotational speed and engine load of the internal combustion engine may be detected, and the knock index may be calculated based on the detection results.

Since the operating conditions of the internal combustion engine can be specified by defining the rotational speed and the engine load,
If the knock index is calculated based on these parameters, an appropriate knock index corresponding to the operating condition of the internal combustion engine can be determined. If the degree of cooling is changed based on the appropriate knock index thus determined, the internal combustion engine can be cooled appropriately and the engine performance can be improved more effectively, which is preferable.

In the above-described internal combustion engine, in addition to the rotational speed and engine load of the internal combustion engine, at least one of the temperature, humidity, atmospheric pressure of the air taken in by the internal combustion engine and the temperature of the cooling liquid is detected. It may be done. When calculating the knock index, the knock index may be calculated in consideration of the detected operating conditions in addition to the rotational speed and the engine load.

Since the temperature, humidity, atmospheric pressure of the air taken in by the internal combustion engine, or the temperature of the cooling liquid may affect the ease of knocking, the rotational speed of the internal combustion engine is determined when the knock index is obtained. And engine load,
If these operating conditions are taken into consideration, it becomes possible to obtain a more appropriate knock index.

In the above-described internal combustion engine, it is possible to detect whether knocking has occurred and correct the knock index based on the detection result. In this way, if the presence or absence of knocking is detected and the detection result is reflected in the knock index, it is possible to correct the knock index to an appropriate value, and by extension, cool the internal combustion engine appropriately to improve engine performance. It becomes possible to improve effectively.

When correcting the knock index depending on the presence or absence of knocking, the correction amount of the knock index may be changed as follows depending on the presence or absence of knocking. That is, the knock index may be corrected so that the correction amount when knocking occurs is larger than the correction amount when knocking is not detected.

In this way, when the occurrence of knocking is detected, the knock index can be promptly corrected to suppress the occurrence of knocking. Further, when knocking does not occur, it is possible to bring the knock index closer to a more appropriate knock index by correcting the knock index little by little.

When the degree of cooling of the internal combustion engine is changed based on the magnitude relationship between the knock index and the threshold value, in addition to the rotational speed and engine load of the internal combustion engine, the temperature and humidity of the air taken in by the internal combustion engine are changed. At least one of the atmospheric pressure and the temperature of the cooling liquid may be detected.
Then, the threshold value may be corrected in consideration of these detected operating conditions.

The temperature, humidity, atmospheric pressure of the air taken in by the internal combustion engine, or the temperature of the cooling liquid may affect the ease of knocking, so the threshold value should be corrected in consideration of these. For example, it is possible to appropriately detect the degree of knocking occurrence and appropriately change the cooling degree of the internal combustion engine.

Alternatively, the presence or absence of knocking may be detected, and the threshold correction amount may be increased based on the detection result. Furthermore, when the threshold value is corrected depending on whether knocking has occurred, the degree of correction may be changed as follows depending on whether knocking has occurred. That is, when knocking occurs, the threshold correction amount may be set to be larger than when the knocking is not detected.

In this way, when the occurrence of knocking is detected, the threshold value can be promptly corrected to suppress the occurrence of knocking. Further, when knocking does not occur, the threshold value can be corrected little by little so that the threshold value can be set more appropriately. Therefore, by appropriately cooling the internal combustion engine, the engine performance can be improved more effectively.

In the above-described internal combustion engine, the knock condition may be predicted by detecting the driving condition and predicting the driving condition after a predetermined time has elapsed. The cooling degree of the internal combustion engine is changed based on the knock index thus obtained.

Even if the cooling control is changed, there is a slight delay before it is actually reflected in the cooling degree of the internal combustion engine. However, if the control is changed by predicting the knock index after a predetermined time. It is preferable that the cooling degree can be changed more appropriately by supplementing the response delay of the cooling degree.

In this way, in the internal combustion engine for predicting the operating condition after the lapse of a predetermined time, the knock index for the current operating condition is compared with the knock index for the predicted operating condition,
The cooling degree may be changed based on the knock index having the larger value.

In this way, if the degree of cooling is changed based on the knock index having the larger value, the degree of cooling will be controlled so as to suppress knocking. For this reason, even if the prediction accuracy of the operating conditions is not sufficiently high, the occurrence of knocking can be avoided, and the engine performance can be effectively improved.

The above-described internal combustion engine may be applied to a vehicle that runs using the internal combustion engine as a power source. The internal combustion engine used as the power source of the vehicle also greatly changes in operating conditions of the internal combustion engine in accordance with changes in running conditions of the vehicle, and therefore is often used under operating conditions in which knocking easily occurs.
Therefore, it is preferable to change the cooling degree of the internal combustion engine based on the knock index obtained from the driving condition of the vehicle, because the performance of the engine can be greatly improved.

In a vehicle using the internal combustion engine as a power source, whether or not the vehicle is climbing is determined based on the detected driving condition. If the vehicle is climbing, the knock is performed. The index may be corrected to a large value. Alternatively, when the degree of cooling of the internal combustion engine is changed based on the magnitude relationship between the knock index and the predetermined threshold value, when it is determined that the vehicle is climbing uphill,
The threshold value may be corrected to a small value.

While the vehicle is climbing uphill, the high load area is frequently used, and the environment is such that knocking easily occurs. Therefore, if the knock index is corrected to a large value or the threshold value is corrected to a small value while the vehicle is climbing uphill, the knocking is controlled in a direction in which knocking is suppressed as compared with the case where the vehicle is traveling on a flat road. Therefore, the engine performance can be improved more effectively.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION In order to more clearly explain the function and effect of the present invention, an embodiment of the present invention will be described in the following order. A. Device configuration: B. Outline of engine control: C. First embodiment: C-1. Cooling control of the first embodiment: C-2. Modifications: (1) First Modification: (2) Second Modification: D. Second Example: D-1. Cooling control of the second embodiment: D-2. Modification: E. Third embodiment:

A. Device Configuration: FIG. 1 is an explanatory diagram showing a schematic configuration of an internal combustion engine of the present invention. In the following, the internal combustion engine will be described as being a so-called spark ignition type engine 10, but of course it may be a compression ignition type engine such as a diesel engine.

As is well known, the operating principle of an engine is to burn fuel in a combustion chamber, convert combustion heat generated at that time into mechanical work, and output it as power. The engine 10 shown in FIG. 1 includes a cylinder block 11 provided with a cylindrical cylinder, a cylinder head 20 mounted on the top of the cylinder block 11, and a piston 12 slidably mounted inside the cylinder. Form a combustion chamber.

The cylinder head 20 is provided with an intake valve 22 for sucking air into the combustion chamber, an exhaust valve 21 for discharging exhaust gas from the combustion chamber, and an ignition plug 23. Further, the cylinder head 20 is provided with an intake manifold 30 for introducing air into the combustion chamber and an exhaust manifold 1 for introducing exhaust gas discharged from the combustion chamber.
6 and 6 are attached.

The intake manifold 30 is a surge tank 3
1 and an air intake passage 32, and is connected to an air cleaner 34. When the outside air passes through the air cleaner 34,
The foreign matter is removed by the element provided in the air cleaner. An injector 35 for injecting fuel is also attached to the intake manifold 30.
The injector 35 is an electromagnetic valve that is driven to open and close under the control of energization to inject fuel, and is supplied with fuel pressurized by a fuel pump (not shown). The fuel injected from the injector 35 evaporates in the intake manifold 30 and mixes with the air in the intake manifold 30 to form an air-fuel mixture. Although the injector 35 injects fuel into the intake manifold 30 here, the injector may be provided in the cylinder head 20 to inject fuel directly into the combustion chamber.

Intake passage 32 upstream of surge tank 31
A throttle valve 36 for adjusting the amount of air flowing into the combustion chamber is provided therein, and the throttle valve 36 is opened and closed by a throttle motor 37.
If the throttle valve 36 is controlled to be closed while the engine 10 is operating, the amount of air passing through the throttle valve 36 decreases, and the negative pressure in the surge tank 31 and the intake manifold 30 increases. The surge tank 31 is also provided with an intake pressure sensor 38 for detecting the pressure inside the intake manifold 30.

The piston 12 is connected to a crankshaft 17 via a crank mechanism. When the crank shaft 17 rotates, the rotation of the crank mechanism is converted into a reciprocating linear motion by the action of the crank mechanism, and the piston 12 slides up and down in the cylinder. A crank angle sensor 41 for detecting the rotational position of the crankshaft is provided at the tip of the crankshaft 17.

When the piston 12 descends with the exhaust valve 21 closed and the intake valve 22 open, the intake manifold 30
The air and the fuel inside flow into the combustion chamber from the intake valve 22. Next, when the intake valve 22 is closed and the piston 12 is raised to compress the intake air-fuel mixture, and then a spark is blown from the spark plug 23, the air-fuel mixture compressed by the piston 12 burns explosively, causing the piston 12 to move. Push it down. This force is converted into rotary motion by the crank mechanism and output as power from the crankshaft 17.

Electronic control unit (hereinafter, ECU) 40
Controls the overall operation of the engine 10. ECU 40
Is a central processing unit (hereinafter, CPU), ROM, RAM,
It is a logical operation circuit configured by connecting input / output circuits and the like to each other by a bus. The ECU 40 injects an appropriate amount of fuel in accordance with the amount of air flowing from the throttle valve 36, so that the air-fuel ratio (air-fuel ratio) of the air-fuel mixture formed in the intake manifold 30 becomes an appropriate value. Various controls are carried out by keeping the sparks or flying a spark at an appropriate timing according to the rise of the piston 12. Further, if the timing of blowing the sparks is too early, a phenomenon called knocking in which the air-fuel mixture abnormally burns near the wall surface in the combustion chamber occurs, and the engine will be damaged if the engine is operated with knocking occurring. Therefore, the engine 10
The cylinder block 11 is provided with a knock sensor 13 for detecting the occurrence of knocking. When knocking occurs, the cylinder block 11 vibrates including a specific frequency component. Therefore, the knock sensor 13 can detect the occurrence of knocking by detecting this frequency component using a resonance phenomenon. ECU 40
When the knock sensor 13 detects the occurrence of knocking, the control also delays the ignition timing to avoid occurrence of knocking.

In such control, the ECU 40 detects various operating conditions such as the accelerator opening operated by the driver, the engine speed and the intake air amount, and the throttle motor 37, according to various programs stored in the ROM, This is performed by driving the spark plug 23, the injector 35, and the like. The accelerator opening can be detected by an accelerator opening sensor 42 provided on the accelerator pedal, the engine speed can be calculated based on the crank angle sensor 41, and the intake air amount can be calculated based on the intake pressure sensor 38. . Further, the ECU 40 includes an intake air temperature sensor 43, a humidity sensor 44, which are provided in the air cleaner 34,
The atmospheric pressure sensor 45 can be used to detect the intake temperature, the intake humidity, and the atmospheric pressure, respectively.

A part of the heat generated by the combustion of the air-fuel mixture is converted into mechanical work and output as power, but a part of the heat flows into the cylinder block 11 and the cylinder head 20 to heat them. . In order to prevent the cylinder block 11 and the cylinder head 20 from being heated beyond the allowable temperature, the cylinder block 11 and the cylinder head 20 are respectively provided with water galleries 14 and 1.
5 are provided. These water galleries 14,1
By cooling water by flowing cooling water to the cylinder 5, the cylinder block 11 and the cylinder head 2 can be operated even while the engine 10 is operating.
0 is kept in an appropriate temperature range. Below, a mechanism for maintaining the cylinder block 11 and the cylinder head 20 in an appropriate temperature range will be described. In addition, in order to cool the cylinder block 11 and the cylinder head 20, it is assumed here that the cooling water flows through the water galleries 14 and 15. However, when a cooling oil or a gas such as air is used instead of the cooling water. Also, the following description can be similarly applied.

FIG. 2 is an explanatory view showing the structure of the cooling system when the engine 10 is viewed from the top side. In Figure 2,
The engine 10 is a four-cylinder engine having four cylinders, and is indicated by “# 1”, “# 2”,
“# 3” and “# 4” represent the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder, respectively. The cooling system of the engine 10 includes a water gallery 14 provided on the cylinder block 11, a water gallery 15 provided on the cylinder head 20, a water pump 50 for sending cooling water to these gallery, and a heat of the cooling water. Radiator 55 for radiating heat to the outside, a downstream cooling water passage 51 that guides the cooling water discharged from the water gallery 15 to the radiator 55, and an upstream cooling water passage that guides the cooling water discharged from the radiator 55 to the water pump 50. 56, a bypass passage 52 that bypasses the radiator 55, a three-way valve 53 that switches between the upstream cooling water passage 56 and the bypass passage 52, and the like. Here, the water pump 50 is described as an electric pump that is driven by using the electric power of a battery (not shown), but it is of course possible to drive the belt by the power output from the engine 10.

The water gallery 14 provided on the cylinder block 11 and the water gallery 15 provided on the cylinder head 20 communicate with each other. The cooling water pumped from the water pump 50 first flows into the water gallery 14 on the cylinder block side, then flows into the water gallery 15 on the cylinder head side, and is discharged from the cylinder head 20 to the downstream cooling water passage 51. To be done. A water temperature sensor 44 is provided in the downstream cooling water passage 51 and can detect the temperature of the cooling water discharged from the cylinder head 20. In the following, the engine 10
The operation of the cooling system will be described.

FIG. 2A is an explanatory diagram showing the operation of the cooling system when the cooling water temperature is low. When the water temperature detected by the water temperature sensor 44 is equal to or lower than the predetermined temperature, the three-way valve 53 is switched to form a flow path in which the cooling water flowing out from the cylinder head 20 returns to the water pump 50 via the bypass passage 52. To be done. In the engine 10 of the present embodiment, the three-way valve 53 is a solenoid valve, and the switching element from the ECU 40 drives the valve element 54 to switch the flow path. Of course, a three-way valve in which a valve body is automatically driven by incorporating a wax that expands according to the water temperature or a bimetal that deforms according to the water temperature may be used.
In this way, the cooling water circulates through the water galleries 14 and 15, whereby the cylinder block 11 and the cylinder head 20 of the engine 10 are maintained in an appropriate temperature range.

FIG. 2B is an explanatory view showing the operation of the cooling system when the cooling water temperature is high. If the water temperature detected by the water temperature sensor 44 exceeds a predetermined temperature, the ECU 40
The three-way valve 53 is switched by the switching signal from. Then, the cooling water flowing out from the cylinder head 20 flows into the radiator 55 via the downstream side cooling water passage 51, releases heat to the outside air there, and then to the water pump 50 via the upstream side cooling water passage 56. After returning, it is again pressure-fed to the water gallery 14 of the cylinder block 11.
In this way, the cooling water flowing out of the cylinder head 20 and having a high temperature is cooled by the radiator 55, so that the cooling water temperature can be cooled to a predetermined temperature or lower.

The three-way valve 53 has been described here as being provided at the confluence of the upstream cooling water passage 56 from the radiator 55 to the water pump 50 and the bypass passage 52. Not limited to this, the cylinder head 20
A three-way valve 53 is provided at a branch point between the downstream side cooling water passage 51 and the bypass passage 52 for guiding the cooling water from the radiator 55 to the radiator 55.
Can also be provided.

As described above, the engine 10 causes the water pump 50 to circulate the cooling water,
The cylinder block 11 and the cylinder head 20 are cooled. The cooling water temperature is monitored by the water temperature sensor 44, and when the water temperature exceeds a predetermined temperature, the three-way valve 53 is switched to guide the cooling water to the radiator 55, and after being cooled by the outside air, it returns to the water pump 50 again and returns to the cylinder block 11. Pumped to. In this way, the cylinder block 11 and the cylinder head 20 can be maintained in an appropriate temperature range by circulating the cooling water while switching the three-way valve 53 according to the water temperature.

It is also known that if the internal combustion engine is appropriately cooled, engine performance can be improved. For example, if the internal combustion engine is maintained at a higher temperature, the temperature of the lubricating oil rises and the viscosity decreases, so that the friction loss of the internal combustion engine can be reduced. If the friction loss is reduced, the output of the engine can be increased and the efficiency of the engine can be improved accordingly.

On the contrary, when the internal combustion engine is maintained at a lower temperature, the temperature of the lubricating oil decreases and the viscosity increases, so that seizure due to the oil film running out on the lubrication surface is less likely to occur, and the engine The durability and reliability can be improved. In addition, if the temperature of the internal combustion engine is kept low, the temperature of the intake air flowing into the combustion chamber can be lowered. Since the density of air increases as the intake air temperature decreases, the intake air amount increases, and the engine output can be improved correspondingly. It is also known that a phenomenon called so-called knocking can be suppressed by lowering the intake air temperature. If the engine is operated with knocking occurring, the internal combustion engine will be damaged, so it is necessary to change the operating conditions of the engine to avoid the occurrence of knocking. Normally, in a gasoline engine, the occurrence of knocking is often avoided by delaying the ignition timing, but such a change in operating conditions is accompanied by adverse effects such as reduction in output and deterioration in fuel consumption efficiency. From this, if it is possible to avoid the occurrence of knocking due to a decrease in intake air temperature, it is possible to eventually increase the engine output and improve the fuel consumption efficiency.

As will be described below, in the engine 10 of this embodiment, by appropriately cooling the cylinder block 11 and the cylinder head 20, the output of the engine and the fuel consumption efficiency can be significantly and surely improved. It is possible.

C. First embodiment: C-1. Cooling control of the first embodiment: FIG. 3 is a flowchart showing the flow of cooling control of the first embodiment. Such control is performed by the CPU incorporated in the ECU 40 executing a program stored in the ROM.

When the cooling control is started, the ECU 40 first reads the operating conditions of the engine 10 (step S100). The engine rotation speed Ne and the engine load are used as the engine operating conditions. The engine rotation speed Ne can be calculated from the output of the crank angle sensor 41. The output of the accelerator opening sensor 42 is used as the engine load, and the maximum accelerator opening state is read as 100% engine load and the accelerator fully closed state is read as 0% engine load. Of course, the engine load may be calculated by detecting the opening of the throttle valve 36 instead of the accelerator opening. This is preferable because the engine load can be accurately detected even when the throttle opens and closes nonlinearly with respect to the accelerator operation.

Next, the read engine speed Ne is read.
The knock index Nindx is determined based on the engine load and the engine load (step S102). The knock index Nindx is an index indicating the ease of knocking. The Nindx value “0” means that there is no possibility of knocking occurrence, and the possibility of knocking occurrence increases as the value increases. Knocking is a phenomenon in which the air-fuel mixture that flows into the combustion chamber spontaneously ignites before being exposed to the flame due to ignition, and the ease of knocking is greatly affected by the engine load. This is because when the engine load increases and the amount of air that flows into the combustion chamber increases,
This is because the temperature rise due to compression becomes large and spontaneous ignition is likely to occur. However, it is also affected by factors other than engine load. Therefore, the knock index Nindx is measured in advance by an experimental method under various conditions depending on the combination of the engine rotation speed Ne and the engine load, and the obtained result is stored in the ROM as a map as shown in FIG. deep. In step S102 of FIG. 3, the knock index Nindx corresponding to the engine operating condition is obtained by referring to such a map. Here, the description has been made assuming that the knock index Nindx is obtained by referring to the map, but Nindx is described in the form of a function F (Ne, engine load) having variables of the engine speed Ne and the engine load. Alternatively, Nindx may be calculated by calculation.

When the knock index Nindx is determined in this way,
Nindx is compared with a predetermined threshold th (step S10).
4). If Nindx is larger than the threshold th, it is determined that knocking is likely to occur, and the set water temperature Tset is set to a predetermined value TLow (step S1).
06). Here, the threshold value th is set to "1.5", and therefore the set water temperature Tset is set to the predetermined value TLow under the operating conditions on the higher load side than the boundary shown by the broken line in FIG. The meaning of the set water temperature Tset will be described later. Conversely, if Nindx is smaller than the threshold value th, it is determined that knocking is unlikely to occur, and the set water temperature Tset is set to a different predetermined value Thigh (step S1).
08). That is, the set water temperature Tset is set to the predetermined value Thigh under the operating condition on the lower load side than the boundary shown by the broken line in FIG. The predetermined value Thigh is set to a value higher than the predetermined value TLow.

Next, the cooling water temperature Wtemp is detected (step S110), and the detected cooling water temperature Wtemp is compared with the previously set water temperature Tset (step S11).
2). The cooling water temperature Wtemp is detected by the water temperature sensor 44 (see FIG. 2). When the cooling water temperature Wtemp is higher than the set water temperature Tset (step S112: yes),
The three-way valve 53
Is switched to the "open" side (step S114). Then, the cooling water is guided to the radiator 55, radiates heat to the outside air to be cooled, and then flows into the water pump 50 (FIG. 2).
(See (b)). When the engine 10 is operated, a part of the combustion heat is transferred and the cylinder block 11 and the cylinder head 20 are constantly heated, so the temperature of the cooling water gradually rises. The water temperature can always be kept at an appropriate temperature. As a result, the cylinder block 11 and the cylinder head 20 can be maintained in an appropriate temperature range.

On the other hand, when the cooling water temperature Wtemp is lower than the set water temperature Tset (step S112: no), the three-way valve 53
Is switched to the "closed" side (step S116). Then, the cooling water flows into the water pump 50 via the bypass passage 52 without passing through the radiator 55 (see FIG. 2A). As described above, the set water temperature Tset is a reference temperature for determining whether to control the three-way valve 53 to the "open" side or the "closed" side. When the engine is operated with the three-way valve 53 switched to the "closed" side, the temperature of the cooling water is gradually raised by being heated by the combustion heat, and when the cooling water temperature Wtemp becomes higher than the set water temperature Tset, The three-way valve 53 is switched to the "open" side, and the radiator 55 radiates heat. Thus set water temperature Tset
By controlling the opening / closing of the three-way valve 53 in accordance with the above, the cooling water is always kept at a temperature near the set water temperature Tset.

When the three-way valve 53 is opened or closed as described above, it is detected whether or not the engine is stopped (step S118). If the engine is running, the process returns to step S100, The following process is repeated until the engine is stopped.

In the cooling control of the first embodiment described above, the knock index is determined based on the operating conditions of the engine, and if the determined knock index is higher than the predetermined threshold th, the cooling water has a lower set water temperature. It is kept near TLow. If the cooling water temperature is kept low, the cooling capacity is increased and the cylinder block 11 or the cylinder head 20 can be cooled to a lower temperature, so that knocking can be avoided. Knock index Nindx under various operating conditions
Can be determined in advance by an experimental method. Therefore, the knock index Nin thus obtained
If the cooling water temperature is set based on dx, the cooling capacity can be appropriately switched, and eventually knocking can be reliably avoided.

If the knock index is lower than the predetermined threshold value th, the cooling water is kept near the high set water temperature Thigh, so that the cylinder block 11 and the cylinder head 2
The temperature of 0 increases and the viscosity of the lubricating oil decreases. As a result, the friction loss of the engine 10 is reduced, the output of the engine is increased, and the fuel consumption efficiency can be improved. Of course, if the temperatures of the cylinder block 11 and the cylinder head 20 are high, knocking is likely to occur, and if knocking occurs, the ignition timing must be delayed, which rather lowers the output and deteriorates the fuel consumption efficiency. However, the engine 1 of the present embodiment
At 0, the cooling water temperature is set based on the knock index obtained according to the operating conditions by the experimental method.
For this reason, the cooling water temperature can be set higher only under the operating condition in which knocking is unlikely to occur, so that a situation such as output reduction and deterioration of fuel consumption efficiency due to knocking does not occur.

As described above, in the engine 10 of this embodiment, since the cooling capacity is switched based on the knock index, the occurrence of knocking is surely avoided, and the output of the engine is increased and the fuel consumption efficiency is improved. Can be realized.

In the above description, the cooling degree of the engine is switched by changing the cooling water temperature by controlling the three-way valve 53. Of course, instead of controlling the three-way valve 53, the water pump 5
It is also possible to control 0 to change the flow rate of the cooling water that circulates in the water gallery 14, 15. Since the cooling capacity of the engine can be increased by increasing the flow rate of the cooling water, it is also possible to control the cooling capacity by controlling the flow rate.

C-2. Modified Example: In the cooling control of the first embodiment described above, the cooling capacity is switched based on the knock index Nindx determined according to the engine operating conditions. By doing this, N that is appropriate for the operating conditions of the engine
Since the indx can be set in advance, the engine 10 can be appropriately cooled while surely avoiding the occurrence of knocking, and the effects of increasing the output and improving the fuel consumption efficiency can be obtained. In addition, if the value of the knock index Nindx is corrected to a more appropriate value in consideration of the operating condition of the engine, the cooling capacity of the engine can be switched more appropriately and the engine performance can be further improved. Below,
The cooling control of various modified examples of the first embodiment will be described.

(1) First Modification: FIG. 5 is a flowchart showing the flow of cooling control of the first modification of the first embodiment. The cooling control of the modified example is greatly different from the cooling control of the first embodiment shown in FIG. 3 in that Nindx is corrected. Hereinafter, a brief description will be given focusing on the differences from the first embodiment.

Also in the cooling control of the first modified example, when the control is started, first, the engine speed Ne and the engine load are read (step S200), and then E
The knock index Nindx is calculated by referring to the map (see FIG. 4) stored in the CU 40 (step S202).

Subsequently, in the cooling control of the first modified example, the process of correcting the knock index Nindx according to various operating conditions is started (step S204). FIG. 6 is a flowchart showing the flow of processing for correcting Nindx. Nindx
When the correction process is started, first, the cooling water temperature Wtemp, the intake air temperature Atemp, the intake humidity M, and the atmospheric pressure Pa are read (step S250). The cooling water temperature Wtemp is detected by the water temperature sensor 44 provided in the downstream cooling water passage 51. The intake air temperature Atemp, the intake air humidity M, and the atmospheric pressure Pa can be detected by using an intake air temperature sensor 43, a humidity sensor 44, and an atmospheric pressure sensor 45 provided in the air cleaner 34, as shown in FIG. .

Next, a correction coefficient corresponding to the detected values of these operating conditions is calculated (step S252). ECU4
In the ROM built in 0, the correction coefficient is stored in advance in the form of a one-dimensional map according to the detected values of these operating conditions. FIG. 7 is an explanatory view conceptually showing how correction coefficients are stored according to various operating conditions. Figure 7
(A) shows that the water temperature correction coefficient Kw is set according to the detected value of the cooling water temperature Wtemp. Knocking is unlikely to occur while the engine is warming up immediately after the engine is started, and is easy to knock when the engine temperature is transiently high such as after running on a mountain road. In consideration of this, the water temperature correction coefficient Kw is set to a small value when the cooling water temperature is low and a large value when the cooling water temperature is high.

Various conditions such as the intake air temperature, the intake air humidity, the atmospheric pressure, and the like affect the susceptibility of knocking as well as the cooling water temperature. Therefore, the influence of these conditions is also corrected using the correction coefficient. FIG. 7B shows how the intake air temperature correction coefficient Ka is set according to the detected value of the intake air temperature Atemp, and FIG. 7C shows the humidity correction coefficient Km set according to the intake air humidity M. FIG. 7D shows how the atmospheric pressure correction coefficient Kp is set according to the detected value of the atmospheric pressure Pa. In step S252 of FIG. 6, the correction coefficient for various conditions is obtained by referring to the one-dimensional map stored in the ROM, and then the correction coefficient K considering all these conditions is calculated by the following equation. K = Kw x Ka x Km x Kp

After obtaining the correction coefficient K in this way, the correction value of the knock index is calculated by multiplying the obtained correction coefficient K by the knock index Nindx (step S25).
4), the Nindx correction process is terminated, and the cooling control of the modified example shown in FIG. 5 is resumed.

When the knock index Nindx is corrected in this way,
This value is compared with a predetermined threshold th (step S2 in FIG. 5).
06), if the corrected knock index Nindx is larger,
It is determined that the condition is such that knocking easily occurs, and the set water temperature Tset is set to a predetermined value TLow (step S20).
8). Conversely, if the corrected Nindx is smaller, it is determined that knocking is unlikely to occur, and the set water temperature Tset is set to a different predetermined value Thigh (step S210). Similar to the cooling control of the first embodiment described above, the predetermined value Thigh
Is set to a value higher than the predetermined value TLow.

Next, the cooling water temperature Wtemp is detected (step S212), and the detected cooling water temperature Wtemp and the set water temperature Tse are detected.
It is compared with t (step S214). Cooling water temperature Wtemp
Is higher than the set water temperature Tset (step S214:
Yes), the three-way valve 53 is switched to the "open" side in order to lower the temperature of the cooling water (step S216). When the cooling water temperature Wtemp is lower than the set water temperature Tset (step S214: no), the three-way valve 53 is switched to the "closed" side (step S218). In this way, when the three-way valve 53 is opened or closed, it is detected whether or not the engine is stopped (step S220). If the engine is running, the process returns to step S200 and continues until the engine is stopped. Repeat the process.

In the first modified example of the first embodiment described above, various operating conditions affecting the ease with which knocking occurs are detected and the knock index Nindx is corrected to a more appropriate value. be able to. By setting the cooling water temperature based on the highly accurate Nindx obtained in this way, it is possible to switch the cooling capacity more appropriately, and by doing so, it is possible to reliably avoid knocking and further improve engine performance. be able to. In the modification described above,
As the conditions to be considered for correcting the knock index Nindx, only the cooling water temperature, the intake air temperature, the intake air humidity, and the atmospheric pressure were detected, but of course, any other conditions may affect the occurrence of knocking. It is also possible to consider various conditions.

(2) Second Modification: When the knock index Nindx is corrected, the knock sensor 13 may be used to detect the actual occurrence of knocking, and the detection result may be used for correction. In the second modified example described below,
The knock index Nindx is corrected by the output of the knock sensor.

FIG. 8 is a flow chart showing the flow of processing for correcting Nindx in the second modification. This processing is performed in step S2 in the cooling control shown in FIG.
This is the process performed in 04. Nin in the second modification
When the dx correction process is started, it is first determined whether or not the amount of change in engine operating conditions is smaller than a predetermined value (step S260). This is the following processing. In the Nindx correction process of FIG. 10, the cooling control loop shown in FIG.
It is executed once every time it turns. Therefore, the engine operating conditions (engine rotation speed, engine load) read in step S200 when the previous loop is rotated,
The engine operating conditions read in this loop are compared to determine whether the engine speed or engine load is significantly different.

The amount of change for any operating condition is
If it is larger than the predetermined value (step S260: no),
The value of the knock correction amount Knk is initialized to "0" (step S262). The meaning of the knock correction amount Knk will be described later. On the contrary, when the change amount of the operating condition is smaller than the predetermined value (step S260: yes), the knock correction amount Knk is not initialized.

Then, the presence or absence of knocking is detected (step S264). Figure 1 shows whether or not knocking has occurred.
It can be detected by the knock sensor 13 as described above with reference to. Then, if knocking has not occurred (step S264: no), the knock correction amount Knk is reduced by a slight predetermined value dnk1 and this value is set as a new knock correction amount Knk (step S266).
Conversely, if knocking has occurred (step S26
4: yes), the predetermined value dnk2 is added to the knock correction amount Knk, and the obtained value is set as a new knock correction amount Knk (step S268). The predetermined value dnk2 used when knocking occurs is set to be larger than the predetermined value dnk1 used when knocking does not occur. In this way, when the knock correction amount Knk is updated according to the presence or absence of knocking, this knock correction amount Knk is used as the knock index Nindx.
And the obtained value is set as a new Nindx (step S270).

After updating Nindx in this way, the Nindx correction process shown in FIG. 8 is terminated and the cooling control shown in FIG. 5 is restored. As described above, in the cooling control, the knock index N
The set water temperature Tset is set based on indx, and the set water temperature Tset
The three-way valve is controlled according to the magnitude relationship between the set and the cooling water temperature Wtemp.

As described above, in the cooling control of the second modification, the knock index Nindx calculated according to the engine operating condition in the cooling control routine of FIG. 5 is the Nindx of FIG.
It is corrected in the correction process. As is clear from this, the knock correction amount Knk is a variable used to correct the knock index Nindx. And knock correction amount Knk
Each time the cooling control routine turns once, a slight predetermined amount dnk1 is decreased when knocking has not occurred, and a predetermined amount dnk2 is increased when knocking has occurred.

FIG. 9 is an explanatory view conceptually showing how the knock index Nindx thus changes with time. As shown in the figure, Nindx is gradually corrected to a small value when knocking has not occurred, and is quickly returned to a large value when the occurrence of knocking is detected. Incidentally, at the point where the knock index Nindx is discontinuous in the figure, the engine operating condition is largely changed and the knock correction amount Knk is reset. In this way, when knocking has not occurred, it is determined that the knock index Nindx has some margin, and N is maintained until knocking occurs.
By decreasing indx little by little, the knock index Nindx can be set to a more appropriate value. Properly set Nin
If the cooling control is performed based on dx, the engine performance can be greatly improved.

Further, dnk1 which is subtracted from the knock correction amount Knk when knocking occurs is set to a value larger than dnk2 which is added to the knock correction amount Knk when knocking does not occur. Therefore, when the occurrence of knocking is detected, the knock index Nindx is quickly returned to a large value, and the cooling water temperature is controlled based on the Nindx, so that the occurrence of knocking can be suppressed quickly.

In the above description, the knock index Nindx stored in association with the engine operating condition is read out from the map, and a correction is added to this value according to the presence or absence of knocking. The present invention is not limited to this, and the value of the knock index Nindx stored in the map in association with the engine operating condition may be rewritten based on the detection of the occurrence of knocking. In this way, if the Nindx stored in the map is corrected according to the knocking detection result, the more appropriate knock index Nindx can be obtained by reflecting the individual difference of each engine. It becomes possible to cool the engine more appropriately.

D. Second Embodiment: In the cooling control of the first embodiment described above, the threshold value th is described as being constant, but an appropriate threshold value th may be set according to operating conditions. The cooling control of the second embodiment that changes the threshold value will be described below.

D-1. Cooling control of the second embodiment: There are various methods for cooling control that sets an appropriate threshold th in accordance with operating conditions. However, by changing the threshold th, a hysteresis characteristic is added to the switching of the cooling water temperature. An example will be described. By doing so, it becomes possible to more reliably avoid knocking even under transient operating conditions.

FIG. 10 is a flow chart showing the flow of cooling control of the second embodiment. The cooling control of the second embodiment shown in FIG. 10 is greatly different from the cooling control of the first embodiment described with reference to FIG. 3 in that the setting of the threshold th can be changed. Hereinafter, such differences will be mainly described.

In the cooling control of the second embodiment as well, similar to the first embodiment, when the control is started, first the engine speed Ne and the engine load are read (step S
300), the knock index Nindx is calculated (step S3).
02).

When the knock index Nindx is calculated in this way,
Then, the process of setting the threshold th is started (step S
304). FIG. 11 is a flowchart showing the flow of processing for setting the threshold th. In the threshold value setting process, first, the current value of the set water temperature Tset is acquired (step S350). As described above with reference to FIGS. 3 and 4, when the engine 10 is operated under conditions where knocking is likely to occur, the set water temperature Tset is set to a low value TLow. On the contrary, when operating under conditions where knocking is unlikely to occur, the set water temperature Tset is set to a higher value Thigh. Therefore, it can be determined from the current set value of the set water temperature Tset whether or not the engine 10 is being operated under conditions where knocking is likely to occur.

Then, it is judged whether or not the acquired set water temperature Tset is set to a value higher than the higher set value Thigh (step S352). When the set water temperature Tset is set to a value smaller than Thigh (step S35)
2: no), the engine 10 determines that the engine 10 is operated under conditions where knocking is likely to occur, and sets the threshold value th to a small predetermined value thL (step S354). vice versa,
When the set water temperature Tset is set to a value equal to or higher than Thigh (step S352: yes), the engine 10 determines that the engine 10 is operating under conditions where knocking is unlikely to occur, and a predetermined value normally used for the threshold th. Thn is set (step S356). When the value of the threshold value th is set in this way, the threshold value setting process shown in FIG. 11 is terminated, and the process returns to the cooling control of the second embodiment shown in FIG.

In the cooling control of the second embodiment, the threshold value th thus set is compared with the knock index Nindx (step S306 in FIG. 10), and the set water temperature Tset is set according to the comparison result.
Switch. That is, if the knock index Nindx is larger, the set water temperature Tset is set to a lower predetermined value TLow (step S308), and if the knock index Nindx is smaller, the set water temperature Tset is set to a higher predetermined value Thigh (step S308).
310).

Here, as described with reference to FIG. 11, when it is determined that the current set water temperature Tset is set low and the engine 10 is operated under the condition that knocking is easy (step S352 of FIG. 11). : No), the threshold value th is set to a lower predetermined value thL. In step S306 during the cooling control of the second embodiment shown in FIG. 10, such a low threshold value th and the knock index Nindx are compared. For this reason, it is easy to determine that the knock index Nindx is larger (that is, it is easy to determine that the operating condition is easier to knock), and the set water temperature Tset of the cooling water is likely to be maintained at the lower predetermined value TLow.

On the contrary, in the threshold value setting process of FIG. 11, when it is determined that the current set water temperature Tset is set to a high value and the engine 10 is operated under the condition that knocking is difficult (see FIG. 11). Step S352: yes),
The threshold value th is set to a normally used predetermined value thn.
Therefore, in step S306 in FIG. 10, the threshold th that is normally used and the knock index Nindx are compared.
If Nindx is larger, it is determined that the operating condition is such that knocking is likely to occur, and the set water temperature Tset is set to a lower predetermined value TLow.
Is set, and if Nindx is smaller, it is determined that the driving condition is such that knocking is difficult, and a higher predetermined value Thigh is set.

After setting the set water temperature Tset in this way, the cooling water temperature Wtemp is then detected and compared with the set water temperature Tset (steps S312 and S314). Then, if the cooling water temperature Wtemp is higher than the set water temperature Tset, the three-way valve 53 is switched to the "open" side (step S316), and the cooling water is guided to the radiator 55. If the cooling water temperature Wtemp is lower than the set water temperature Tset, the three-way valve 53 is switched to the “closed” side (step S318) and the cooling water is guided to the bypass passage 52. When the three-way valve 53 is switched to the open / closed state in this way, it is detected whether or not the engine is stopped (step S320). If the engine is running, the process returns to step S300 and continues until the engine is stopped. Repeat the process.

In the cooling control of the second embodiment described above, the threshold value t is set according to the current set temperature Tset of the cooling water.
The value of h is changed. Therefore, when the operating condition of the engine 10 shifts from a condition in which knocking is difficult to a condition in which knocking is easy, the set water temperature Tset is quickly switched to a lower water temperature. On the other hand, when moving from a condition where knocking is easy to a condition where knocking is difficult, unless the ease of knocking changes significantly, it does not switch to a higher water temperature, and keeps a low water temperature for a while, so-called It will have hysteresis characteristics.

FIG. 12 is an explanatory view conceptually showing how a hysteresis characteristic appears in the cooling water temperature by performing the cooling control of the second embodiment. As the engine load increases, the knock index Nindx also increases. Therefore, the set water temperature Tset of the cooling water switches to a lower water temperature at a certain point, as shown by the solid line in the figure. On the other hand, when the engine load is reduced, as shown by the broken line in the figure, the set water temperature Tset does not change easily even if Nindx decreases, and the water temperature is kept low for a while.

When the cooling control of the second embodiment is performed, such a hysteresis characteristic appears in the temperature change of the cooling water, so that the occurrence of knocking can be avoided more surely and, in turn, the engine performance. It is possible to make a sure improvement. That is, for example, while running on a mountain road,
Under operating conditions in which the engine load fluctuates greatly, most of the operating conditions are such that knocking is likely to occur, while operating under conditions where knocking is difficult for a short period (for example, several seconds). In such a case, if the set water temperature Tset is switched one by one in accordance with the knock index Nindx, after operating for a short period of time under conditions where knocking is difficult, immediately after shifting to operating conditions where knocking is easier,
Knocking may occur and reduce engine performance. On the other hand, as in the cooling control of the second embodiment,
By providing the hysteresis characteristic, it is possible to prevent knocking from occurring immediately after the driving condition is changed. Therefore, it is possible to more reliably achieve the performance improvement effect by optimizing the engine cooling.

Further, if the hysteresis characteristic is given, the set water temperature Tset is frequently switched between the high water temperature Thigh and the low water temperature TLow, and accordingly, the movable parts such as the three-way valve 53 are frequently opened and closed, This is preferable because it is possible to avoid the occurrence of a situation where the movable part fails.

In the second embodiment described above, the threshold value th
It has been described that the hysteresis characteristic is given by changing the setting of. It goes without saying that the method for imparting the hysteresis characteristic is not limited to setting the threshold value th, and well-known different methods can be applied. For example, when the set water temperature Tset is switched from the lower set value TLow to the higher set value Thigh, the set water temperature Tset is maintained at the lower set value TLow for a predetermined time (for example, several seconds) and then switched to the higher set value Thigh. May be. By doing so, it is possible to impart the hysteresis characteristic by a simple method.

D-2. Modification: In the above-described second embodiment, the threshold characteristic th is changed to give the hysteresis characteristic to the switching of the set water temperature Tset. When the internal combustion engine is mounted on the vehicle, it may be detected that the vehicle is traveling on an uphill road and the threshold value th may be changed so that the cooling water temperature is controlled to be low during the uphill travel. Good. The cooling control of the modified example of the second embodiment will be described below.

FIG. 13 shows a modification of the second embodiment.
7 is a flowchart showing a flow of processing for detecting whether or not the vehicle is traveling on an uphill and setting a threshold th. In the threshold value setting process of the modification, first, the operating condition of the engine and the setting of the gear ratio are detected, and the acceleration of the vehicle is calculated (step S370). The acceleration calculated here is the acceleration that will be realized when the vehicle is traveling on a flat ground in the detected engine operating condition and the setting of the gear ratio. The gear ratio can be detected from the position of a shift lever (not shown) of the transmission provided in the vehicle. Hereinafter, a method of calculating the acceleration of the vehicle will be described.

FIG. 14 is an explanatory diagram showing the principle of calculating the acceleration of the vehicle. The acceleration of the vehicle is generated when the driving torque of the vehicle overcomes the running resistance and accelerates the vehicle. The thick broken line shown in FIG. 14 indicates the running resistance of the vehicle. The running resistance of the vehicle is substantially determined by the vehicle speed, and the running resistance increases as the vehicle speed increases. For reference, the value of the vehicle speed is also displayed on the broken line indicating the running resistance. The vehicle speed is determined by the rotation speed of the wheels, and the rotation speed of the wheels is determined by the engine rotation speed and the gear ratio. From this, if the vehicle speed and the gear ratio are determined, the corresponding engine rotation speed is determined. The broken line showing the running resistance in FIG. 14 is a plot of the running resistance and the engine rotation speed at various vehicle speeds when the gear ratio is set to the fourth speed.

Now, it is assumed that the engine operating condition detected in step S370 is the condition indicated by a black star mark * in FIG. When the operating condition of the engine is determined, the generated torque is also determined, so that one corresponding coordinate point can be determined in FIG. As described above, when the gear ratio is determined, the engine rotation speed and the vehicle speed have a one-to-one correspondence, and when the gear ratio is the fourth speed, the engine rotation speed indicated by a star corresponds to a vehicle speed of about 50 km / h. Since the difference between the running resistance at this vehicle speed and the torque actually output by the engine is the torque used for accelerating the vehicle, the acceleration can be calculated if the vehicle weight is given. In FIG. 14, the torque used for accelerating the vehicle is indicated by a white arrow. As described above, in step S370 of FIG. 13, the engine operating condition and the gear ratio are detected, and the acceleration on the flat ground is calculated. The vehicle weight required for the calculation is given separately.

Then, the actual acceleration of the vehicle is measured (step S372 in FIG. 13). The actual acceleration can be calculated based on the output change of a rotation speed sensor (not shown) provided on the axle of the vehicle. The actual acceleration thus obtained is compared with the previously calculated acceleration (step S374). If the vehicle is traveling on a substantially flat ground, the actual acceleration should be approximately equal to the calculated acceleration. Therefore, if the difference between the calculated acceleration and the actual acceleration is less than or equal to a predetermined value, it can be determined that the vehicle is traveling on a flat ground. If the actual acceleration is separated from the calculated acceleration by a predetermined value or more, it can be considered that the running resistance has changed because the vehicle is climbing or descending.

From this, it can be considered that the vehicle is climbing a slope when the actual acceleration is smaller than a predetermined value with respect to the calculated acceleration, and in this case (step S374:
Yes), and sets the value of the threshold th to a small predetermined value thL (step S376). When it is determined that the vehicle is not climbing the slope (step S374: no), the threshold value th is set to the normal predetermined value thn (step S37).
8). When the value of the threshold th is set in this way, the threshold setting process of the modification shown in FIG. 13 is ended, and the cooling control of the second embodiment shown in FIG. 10 is restored.

When the cooling control of the second embodiment of FIG. 10 is restored, the threshold value th thus set is compared with the knock index Nindx (step S306). If the knock index Nindx is larger, the set water temperature Tset is set to a lower value. The value TLow is set, and if the Nindx is smaller, the set water temperature Tset is set to a higher predetermined value Thigh (step S308, step S308).
S310). As a result, when it is determined that the vehicle is climbing a slope, the cooling water temperature is easily controlled to be low. Since the engine is often operated under a high load condition when climbing, knocking easily occurs. Therefore, if the cooling water temperature is controlled to be low, knocking can be suppressed and engine performance can be improved.

E. Third Embodiment: In the various embodiments described above, the knock index Nin corresponding to the current engine operating condition is used.
The cooling control was performed based on dx. On the other hand, the engine operating condition after a predetermined time may be predicted, and the cooling control may be performed based on the knock index (predicted knock index Nantx) corresponding to the predicted condition. The cooling control of the third embodiment will be described below.

FIG. 15 is a flow chart showing the flow of cooling control of the third embodiment. The illustrated cooling control of the second embodiment is greatly different from the cooling control of the first embodiment described above with reference to FIG. 3 in that control for predicting engine operating conditions after a predetermined time is performed. In the following, a brief description will be given focusing on such differences.

In the cooling control of the third embodiment, as in the first embodiment, when the control is started, the engine speed Ne and the engine load are first read to calculate the knock index Nindx (step S400).

Next, a process of predicting the engine operating condition after a predetermined time and calculating the predicted knock index Nantx is performed (step S402). FIG. 16 is a flowchart showing the flow of processing for predicting engine operating conditions and calculating the predicted knock index Nantx. Such processing is performed by the ECU 4
This is performed by the CPU incorporated in 0 executing the program stored in the ROM.

When the predicted knock index determination process is started, first, the accelerator opening and the vehicle speed are detected (step S450). The accelerator opening is measured by the accelerator opening sensor 4
2 to detect. The vehicle speed is detected by a rotation speed sensor (not shown) provided on the axle of the vehicle.

Next, the required output required by the driver of the vehicle is calculated from the accelerator opening and the vehicle speed (step S452). This is the following processing. When the driver of the vehicle desires to increase the torque generated by the engine 10 while the vehicle is traveling, the driver of the vehicle performs an operation of further pressing the accelerator pedal in accordance with the desired amount of torque increase. From this, the generated torque required by the driver can be obtained based on the accelerator opening and the vehicle speed. For more information,
The value of the required output is stored in advance in the ROM built in the ECU 40 in the form of a map having the accelerator opening and the vehicle speed as variables, and the map is detected in step S450 by referring to this map. The value of the required output corresponding to the above condition is obtained.

When the required output is obtained in this way, the engine operating condition corresponding to the required output value is determined (step S454). As described above, the engine operating condition is also defined here by the engine speed and the engine load. In response to the request output,
The reason why the engine operating condition can be determined will be described. Generally, the output generated by the engine is determined according to the engine operating conditions. If this is seen from the opposite, the operating conditions for generating the required output are narrowed down to some operating conditions among the operating conditions that the engine 10 can adopt. In fact, by considering the current engine operating conditions, one suitable operating condition can be determined from these operating conditions. For example, if the engine rotation speed is maintained, one operating condition for generating the required output can be determined. Further, the engine operating condition may be determined by considering the vehicle speed and the shift pattern, estimating the engine rotation speed after a predetermined time (for example, several seconds), and obtaining the engine load at that time.

FIG. 17 is an explanatory view conceptually showing how the engine operating condition after the predetermined time has been predicted. In FIG. 17, it is shown that, from the current engine operating condition indicated by a black star, it is predicted that the operating condition indicated by a white star will be reached after a predetermined time.

After the predicted engine operating condition is determined in this way, the knock index Nantx corresponding to the predicted engine operating condition is determined by referring to the map stored in the ROM (step S456 in FIG. 16).
When the knock index Nantx corresponding to the predicted engine operating condition is determined as described above, the predicted knock index determination process is terminated and the cooling control of the third embodiment shown in FIG. 13 is resumed.

When returning to the cooling control, the knock index Nindx determined based on the current engine operating conditions and the predicted knock index Nantx determined based on the predicted engine operating conditions are compared, and the knock value is determined by the larger value. Index N
Indx is updated (step S404 in FIG. 5). In the example shown in FIG. 17, the knock index Nindx corresponding to the current engine operating condition indicated by a black star mark has a value of around “1” and corresponds to the predicted engine operating condition indicated by a white star mark. The predicted knock index Nantx takes a value around “2”. From this, in step S404 of FIG. 13, the value of the knock index Nindx is equal to the predicted knock index N.
It will be overwritten by the value of antx.

After updating the value of the knock index Nindx in this way, the subsequent processing is the same as in the first embodiment described above. Only the outline will be described below. The knock index Nindx is compared with the threshold th (step S406). If Nindx is larger, a lower predetermined value TLow is set, and if not, a higher predetermined value Thigh is set to the set water temperature Tset (step S408). , S410). Next, the cooling water temperature Wtemp is detected and compared with the set water temperature Tset (step S41).
2, S414), and switches the three-way valve to either "open" or "closed" depending on the result (steps S416 and S41).
8). Then, it is detected whether or not the engine is stopped (step S420), and if the engine is running, the process returns to step S400, and the subsequent processing is repeated until the engine is stopped.

In the cooling control of the third embodiment described above, the knock index Nin corresponding to the current engine operating condition is set.
In addition to dx, the engine operating condition after a predetermined time is predicted, and the predicted knock index Nantx under the operating condition is calculated. Next, these knock indexes are compared, and the cooling index is controlled using the larger index value as the knock index Nindx.
Even if the cooling capacity of the engine is switched, there is usually some delay before the change of the cooling water temperature appears, but if the control that predicts the engine operating condition after a predetermined time is performed in this way, the response of the cooling water temperature will change. The delay can be shortened. For this reason, it is possible to reliably avoid the occurrence of knocking, and it is possible to further enhance the effect of improving the engine performance by appropriately cooling the engine.

Although various embodiments have been described above, the present invention is not limited to all the embodiments described above, and can be implemented in various modes without departing from the scope of the invention.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of the configuration of an internal combustion engine of this embodiment.

FIG. 2 is an explanatory diagram showing an outline of a cooling system adopted in the internal combustion engine of the present embodiment.

FIG. 3 is a flowchart showing a flow of cooling control according to the first embodiment.

FIG. 4 is an explanatory diagram conceptually showing how a knock index is stored in association with an engine operating condition.

FIG. 5 is a flowchart showing a flow of cooling control in a first modification of the first embodiment.

FIG. 6 is a flowchart showing a flow of processing for correcting a knock index in the cooling control of the first modified example.

FIG. 7 is an explanatory diagram conceptually showing how correction coefficients are stored for various operating conditions.

FIG. 8 is a flowchart showing a flow of processing for correcting a knock index in cooling control of a second modified example of the first embodiment.

FIG. 9 is an explanatory diagram conceptually showing how the knock index is corrected in accordance with the presence or absence of knocking in the cooling control of the second modified example.

FIG. 10 is a flowchart showing a flow of cooling control according to the second embodiment.

FIG. 11 is a flowchart showing a flow of processing for correcting a threshold value in the cooling control of the second embodiment.

FIG. 12 is an explanatory view conceptually showing how hysteresis characteristics are added to the setting of the cooling water temperature in the cooling control of the second embodiment.

FIG. 13 is a flowchart showing the flow of processing for correcting the threshold value in the cooling control of the modified example of the second embodiment.

FIG. 14 is an explanatory diagram showing a method of determining whether or not the vehicle is climbing a slope based on driving conditions.

FIG. 15 is a flowchart showing the flow of cooling control of the third embodiment.

FIG. 16 is a flowchart showing a flow of processing for predicting a knock index after a lapse of a predetermined time in the cooling control of the third embodiment.

FIG. 17 is an explanatory diagram conceptually showing how the knock index after a predetermined time has elapsed is predicted in the cooling control of the third embodiment.

[Explanation of symbols]

10 ... Engine 11 ... Cylinder block 12 ... Piston 13 ... Knock sensor 14, 15 ... Water Gallery 16 ... Exhaust manifold 17 ... Crank shaft 20 ... Cylinder head 21 ... Exhaust valve 22 ... Intake valve 23 ... Spark plug 30 ... Intake manifold 31 ... Surge tank 32 ... Intake passage 34 ... Air cleaner 35 ... Injector 36 ... Throttle valve 37 ... Throttle motor 38 ... Intake pressure sensor 40 ... ECU 41 ... Crank angle sensor 42 ... Accelerator opening sensor 43 ... Intake air temperature sensor 44 ... Humidity sensor 44 ... Water temperature sensor 45 ... Atmospheric pressure sensor 50 ... Water pump 51 ... Downstream cooling water passage 52 ... Bypass passage 53 ... Three-way valve 54 ... Valve 55 ... radiator 56 ... Upstream cooling water passage

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02P 17/12 F02P 17/00 R

Claims (18)

[Claims] 1. An internal combustion engine that converts combustion heat generated in a combustion chamber into mechanical work and outputs the mechanical work, wherein the combustion heat flowing into the internal combustion engine is removed by cooling the internal combustion engine. Cooling means, operating condition detection means for detecting the operating conditions of the internal combustion engine, knock index as an index related to the ease of occurrence of knocking, knock index calculating means for calculating based on the detected operating conditions, An internal combustion engine comprising: a cooling control unit that changes a cooling degree of the internal combustion engine by controlling the cooling unit based on the calculated knock index. 2. The internal combustion engine according to claim 1, wherein the cooling unit is a unit that circulates a cooling liquid to cool the internal combustion engine, and the cooling control unit changes a temperature of the cooling liquid. By doing so, an internal combustion engine that is means for changing the cooling degree of the internal combustion engine. 3. The internal combustion engine according to claim 1, wherein the cooling unit is a unit that circulates a cooling liquid to cool the internal combustion engine, and the cooling control unit changes a flow rate of the cooling liquid. By doing so, an internal combustion engine that is means for changing the cooling degree of the internal combustion engine. 4. The internal combustion engine according to claim 1, wherein the cooling control unit cools the internal combustion engine based on a magnitude relationship between the knock index and a predetermined threshold value. An internal combustion engine that is a means of changing the degree. 5. The internal combustion engine according to claim 4, wherein the cooling unit is a unit that circulates a cooling liquid to cool the internal combustion engine, and the cooling control unit has the knock index of the predetermined value. When it is smaller than the threshold value, the temperature of the cooling liquid is controlled to the first cooling liquid temperature, and when the knock index is larger than the predetermined threshold value, the temperature of the cooling liquid is lower than the first cooling liquid temperature. 2. An internal combustion engine which is a means for controlling the temperature of the cooling liquid. 6. The internal combustion engine according to claim 1, wherein the operating condition detecting means is a means for detecting at least a rotational speed and an engine load of the internal combustion engine, The knock index calculating means is an internal combustion engine that is a means for calculating the knock index based on the rotational speed and the engine load. 7. The internal combustion engine according to claim 6, wherein the cooling unit is a unit that circulates a cooling liquid to cool the internal combustion engine, and the operating condition detection unit is sucked by the internal combustion engine. At least one of the temperature of air, humidity, atmospheric pressure, or the temperature of the cooling liquid is a means for detecting in addition to the rotation speed and the engine load, and the knock index calculation means is the rotation speed and the engine. An internal combustion engine that is means for calculating the knock index in consideration of at least a part of the detected operating conditions in addition to the load. 8. The internal combustion engine according to any one of claims 1 to 7, wherein the knock detection means detects whether or not knocking has occurred, and the knocking based on a result of detection of whether or not knocking has occurred. An internal combustion engine comprising: a knock index correcting means for correcting an index. 9. The internal combustion engine according to claim 8, wherein the knock index correction means corrects the knock index correction amount when the knocking occurrence is detected, and when the knocking occurrence is not detected. To be bigger than
An internal combustion engine that is means for correcting the knock index. 10. The internal combustion engine according to claim 4, wherein the cooling unit is a unit that circulates a cooling liquid to cool the internal combustion engine, and the operating condition detection unit is sucked by the internal combustion engine. Air temperature, humidity, atmospheric pressure, or a means for detecting at least one of the temperature of the cooling liquid, based on at least one of the temperature of the detected air, humidity, atmospheric pressure, or the temperature of the cooling liquid An internal combustion engine, which comprises threshold correction means for correcting the threshold, and wherein the cooling control means is means for switching the cooling degree of the internal combustion engine by comparing the knock index with the corrected threshold. 11. The internal combustion engine according to claim 4, further comprising knock detection means for detecting whether knocking has occurred, and threshold correction means for correcting the threshold value based on a detection result of whether knocking has occurred. The internal combustion engine, wherein the cooling control means is means for switching a cooling degree of the internal combustion engine by comparing the knock index with the corrected threshold value. 12. The internal combustion engine according to claim 11, wherein the threshold value correction means is a means for correcting the threshold value to be larger when detecting the occurrence of knocking than when not detecting the occurrence of knocking. Internal combustion engine. 13. The internal combustion engine according to claim 1, further comprising operating condition predicting means for predicting an operating condition after a predetermined time has elapsed, based on the detected operating condition. The knock index calculating means is an internal combustion engine that is a means for calculating the knock index based on the predicted operating condition. 14. The internal combustion engine according to claim 13, wherein a knock index corresponding to the detected operating condition and a knock index corresponding to the predicted operating condition are compared to determine a knock index having a large value. An internal combustion engine comprising: knock index selecting means for selecting, wherein the cooling control means is means for controlling the cooling means based on the selected knock index. 15. A vehicle equipped with an internal combustion engine as a power source, the cooling means removing the combustion heat transmitted to the internal combustion engine by cooling the internal combustion engine, and operating conditions of the vehicle are detected. Operating condition detecting means, a knock index calculating means for calculating a knock index, which is an index related to the likelihood of knocking, based on the detected operating condition, and the cooling means based on the calculated knock index. And a cooling control means for changing the cooling degree of the internal combustion engine by controlling the vehicle. 16. The vehicle according to claim 15, wherein climbing condition detecting means for detecting whether or not the vehicle is climbing on the basis of the detected driving condition, and: A vehicle that is provided with a knock index correcting unit that corrects the knock index to a large value, and the cooling control unit is a unit that controls the cooling unit based on the corrected knock index. 17. The vehicle according to claim 15, wherein the cooling control means is means for switching a cooling degree of the internal combustion engine by comparing the knock index with a predetermined threshold value, and the vehicle is climbing a slope. Whether the vehicle is in the middle, climbing condition detecting means for detecting based on the detected driving condition, and while the vehicle is climbing, a threshold correcting means for correcting the threshold value to be compared with the knock index to a small value. Vehicle equipped. 18. A method of cooling an internal combustion engine, which converts combustion heat generated in a combustion chamber into mechanical work and outputs the mechanical work, the operating condition of the internal combustion engine being detected to relate to knocking easiness. A cooling method in which a knock index, which is the index, is calculated based on the detected operating condition, and the degree of cooling of the internal combustion engine is changed based on the calculated knock index.