JP4415803B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine provided with a variable valve mechanism capable of adjusting a valve overlap amount between an intake valve and an exhaust valve.

  In an engine that performs port injection, since the intake port is cold when the engine is not warmed up, so-called fuel wet occurs in which the injected fuel is not sufficiently vaporized and part of it adheres to the inner wall surface of the intake port. Further, even in the cylinder (combustion chamber), fuel wet adheres to the inner wall surface of the cylinder liner and the upper surface of the piston, and further, a situation occurs in which the fuel is discharged to the exhaust pipe without being burned. Since most of such fuel wet does not contribute to combustion, the amount of combustible fuel in the cylinder is reduced by the generation of fuel wet. For this reason, if this decrease is not taken into account, the actual air-fuel ratio becomes leaner than the target air-fuel ratio, so that the fuel injection amount increase correction is performed.

  Further, as the engine warms up, the in-cylinder ambient temperature rises accordingly, and the amount of fuel wet vaporization increases. Therefore, if the fuel injection amount increase correction is performed without taking this increase in vaporization amount into consideration, the combustible fuel in the cylinder increases and the actual air-fuel ratio becomes richer than the target air-fuel ratio. The increase in vaporization is excluded from the increase in vaporization. Such a warm-up increase correction of the fuel injection amount during engine warm-up is disclosed in, for example, Patent Document 1 and Patent Document 2.

  By the way, for the purpose of reducing exhaust emissions and improving fuel efficiency, recent engines have a variable valve timing mechanism or the like that can adjust the valve overlap amount between the intake valve and the exhaust valve, as shown in Patent Document 3, for example. Those equipped with a variable valve mechanism have become mainstream.

However, during such warming up of the engine, the degree of increase in the in-cylinder ambient temperature differs depending on the operating state of the variable valve timing mechanism, etc. In Patent Document 3 and Patent Documents 1 and 2, the air-fuel ratio control accuracy deteriorates and exhaust emission deteriorates.
JP 2002-213281 A JP-A-6-264791 JP 2002-276431 A

  The present invention relates to an internal combustion engine having a variable valve mechanism that can improve the accuracy of air-fuel ratio control and improve exhaust emission by suitably performing warm-up increase correction of the fuel injection amount. The main purpose is to provide a control device.

  Hereinafter, effective means for solving the above-described problems will be described while showing effects.

Means 1. The internal combustion engine includes a variable valve mechanism that can adjust a valve overlap amount between an intake valve and an exhaust valve, and a fuel injection valve that injects fuel near the intake port of the internal combustion engine. The control device for the internal combustion engine calculates a warm-up increase value at each time during the warm-up period, and performs a warm-up increase correction of the fuel injection amount based on the calculated warm-up increase value. In such a control device for an internal combustion engine, a base value calculation means for calculating a warm-up increase base value for calculating a warm-up increase value, an overlap amount detection means for detecting a valve overlap amount, and temperature correction term warming increase value based on the calculated in-cylinder temperature estimation means for, calculated estimated cylinder ambient temperature so that the valve overlap amount larger the estimated in-cylinder ambient temperature the valve overlap amount with increases And a warm-up increase value calculating means for calculating the warm-up increase value by reflecting the temperature correction term in the warm-up increase base value.

  By the way, during the warm-up period of the internal combustion engine (non-warm-up state), fuel wet that cannot contribute to combustion occurs in the cylinder (combustion chamber) and the intake port where fuel injection is performed. The fuel injection warm-up increase correction is implemented. However, in an internal combustion engine having a variable valve mechanism, internal EGR occurs due to valve overlap, and high-temperature burned gas (EGR gas) remains in the cylinder. Further, the increase in the valve overlap amount promotes the increase in the internal EGR rate in the cylinder (the ratio occupied by the internal EGR in the combustion chamber) or the internal EGR amount, and this increase in the internal EGR rate or amount increases the in-cylinder ambient temperature. Promote the rise. Thereby, vaporization of fuel wet is promoted, and the fuel that can contribute to combustion increases. Therefore, if the increase in fuel wet vaporization based on the increase in the in-cylinder ambient temperature due to the valve overlap is removed in advance from the warm-up increase value, the combustible fuel in the cylinder becomes surplus. Thus, the rich state is prevented. As a result, the control accuracy of the air-fuel ratio can be improved, and the exhaust emission can be improved.

  Mean 2. In the above means 1, the in-cylinder temperature estimating means calculates the internal EGR rate or the internal EGR amount using the valve overlap amount and the intake air amount, and calculates the estimated in-cylinder atmosphere temperature using the internal EGR rate or the internal EGR amount. To do.

  That is, the estimated in-cylinder atmosphere temperature is calculated based on the internal EGR rate or amount calculated using the valve overlap amount and the intake air amount. As described above, increasing the valve overlap amount promotes an increase in the internal EGR rate or amount in the cylinder and promotes an increase in the in-cylinder atmosphere temperature. Therefore, the valve overlap amount and the internal EGR rate or amount are calculated. By using the intake air amount, which is an important factor for this, it is possible to detect the estimated in-cylinder ambient temperature with high accuracy. Therefore, the control accuracy of the air-fuel ratio can be improved more reliably.

  Means 3. In the above means 2, the in-cylinder temperature estimating means calculates the estimated in-cylinder atmosphere temperature using the internal EGR rate or the internal EGR amount, the estimated internal EGR temperature calculated using the ignition timing and the air-fuel ratio, and the intake air temperature. To do.

  That is, the in-cylinder atmosphere temperature is calculated based on the internal EGR rate or amount, the estimated internal EGR temperature, and the intake air temperature, which are important factors for calculating the estimated in-cylinder atmosphere temperature. A high estimated in-cylinder atmosphere temperature can be detected, and the control accuracy of the air-fuel ratio can be improved more reliably.

  Means 4. In any one of the above means 1 to 3, the temperature correction term calculation means is a temperature at which the warm-up increase value decreases as the estimated in-cylinder atmosphere temperature increases until the estimated in-cylinder atmosphere temperature reaches a predetermined temperature. A correction term is calculated.

  That is, in the normal range until the in-cylinder atmosphere temperature reaches the predetermined temperature, a temperature correction term is calculated such that the warm-up increase value decreases as the estimated in-cylinder atmosphere temperature increases. In the normal range of the in-cylinder ambient temperature, the in-cylinder ambient temperature rises as the internal combustion engine warms up, and the amount of vaporized fuel wet adhering to the in-cylinder and the intake port increases. Since the combustible fuel in the cylinder is supplemented, the control accuracy of the air-fuel ratio can be more reliably improved by decreasing the warm-up increase value.

  Means 5. In the above means 4, when the estimated in-cylinder atmosphere temperature exceeds the predetermined temperature, the temperature correction term calculating means increases the warm-up increase value from the warm-up increase value at the predetermined temperature in accordance with the increase in the estimated in-cylinder atmosphere temperature. Such a temperature correction term is calculated.

  That is, in an abnormal range where the in-cylinder ambient temperature exceeds the predetermined temperature, a temperature correction term is calculated such that the warm-up increase value is increased from the warm-up increase value at the predetermined temperature as the estimated in-cylinder atmosphere temperature increases. . In this abnormal range of the in-cylinder atmosphere temperature, the combustion becomes unstable as the in-cylinder atmosphere temperature increases. Therefore, the combustion can be stabilized by increasing the warm-up increase value.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In this embodiment, an engine control system is constructed for an in-vehicle multi-cylinder gasoline engine that is an internal combustion engine, and the engine of the control system is provided with a turbocharger with an electric motor as a supercharger. First, an overall schematic configuration diagram of the engine control system will be described with reference to FIG.

  In the engine 10 shown in FIG. 1, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11, and an air flow meter 13 for detecting the intake air amount is provided downstream of the air cleaner 12. A throttle valve 14 whose opening is adjusted by an actuator such as a DC motor and a throttle opening sensor 15 for detecting the throttle opening are provided on the downstream side of the air flow meter 13. A surge tank 16 is provided downstream of the throttle valve 14, and an intake pipe pressure sensor 17 for detecting the intake pipe pressure is provided in the surge tank 16. The surge tank 16 is connected to an intake manifold 18 that introduces air into each cylinder of the engine 10. In the intake manifold 18, an electromagnetically driven fuel injection that injects fuel near the intake port of each cylinder. A valve 19 is attached. That is, port injection is performed by the fuel injection valve 19.

  An intake valve 21 and an exhaust valve 22 are respectively provided in the intake port and the exhaust port of the engine 10, and an air / fuel mixture is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust valve 22. The exhaust gas after combustion is discharged into the exhaust pipe 24 by the opening operation. The intake valve 21 and the exhaust valve 22 are provided with variable valve mechanisms 25 and 26, respectively. These variable valve mechanisms 25 and 26 have a structure in which valve opening / closing operation conditions such as opening / closing timings and valve overlap amounts of the valves 21 and 22 can be continuously changed, and the engine operating state at each time The valve opening / closing operation conditions are appropriately adjusted according to the driver's request or the like.

  An intake side cam angle sensor 27 and an exhaust side cam angle sensor 28 are attached to the cylinder head of the engine 10. The intake side cam angle sensor 27 detects the intake side cam angle provided in the variable valve mechanism 25 in order to calculate the opening / closing timing of the intake valve 21 and the like. The exhaust side cam angle sensor 28 detects an exhaust side cam angle provided in the variable valve mechanism 26 in order to calculate the opening / closing timing of the exhaust valve 22 and the like. The valve overlap amounts of both valves 21 and 22 are also calculated from the detected intake side and exhaust side cam angles.

  An ignition plug 29 is attached to the cylinder head of the engine 10 for each cylinder, and a high voltage is applied to the ignition plug 29 at a desired ignition timing by an ignition device 30 including an ignition coil and the ECU 40. The By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 29, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion. The exhaust pipe 24 from which the exhaust gas is discharged is provided with a catalyst 31 such as a three-way catalyst for purifying CO, HC, NOx, etc. in the exhaust gas, and the exhaust gas is detected upstream of the catalyst 31. An air-fuel ratio sensor 32 for detecting the air-fuel ratio of the air-fuel mixture is provided as a target.

  The cylinder block of the engine 10 has a cooling water temperature sensor 33 that detects the temperature (cooling water temperature) of the cooling water that circulates mainly in the engine 10, a predetermined position for detecting the crank position (rotation angle), the engine speed, and the like. A crank angle sensor 34 that outputs a rectangular crank angle signal for each crank angle (for example, at a cycle of 30 ° CA) is attached.

  As is well known, the ECU 40 is mainly composed of a microcomputer including a CPU, a ROM, a RAM, and the like. In addition to the various sensors described above, detection signals are also input to the ECU 40 from an intake air temperature sensor 35 for detecting intake air temperature (intake air temperature) and an atmospheric pressure sensor 36 for detecting atmospheric pressure. The ECU 40 grasps the engine operating state and the driver's request at that time based on various detection signals that are input as needed, and executes various controls according to the engine operating state according to the control program.

  That is, the ECU 40 controls the variable valve mechanism 25 so that the valve opening / closing operation conditions such as the valve opening timing and valve overlap amount of the intake valve 21 and the exhaust valve 22 correspond to the engine operating state and the driver's request at that time. , 26 are controlled. Incidentally, immediately after the engine is started, the ECU 40 is in the non-operating state of the variable valve mechanisms 25 and 26, and at this time, the valve overlap between the valves 21 and 22 is not generated. When a predetermined time has elapsed since the engine was started, the ECU 40 starts the operation of the variable valve mechanisms 25 and 26. As a result, the valve opening period of the exhaust valve 22 is shifted to the retard side, and the valve opening period of the intake valve 21 is shifted to the advance side, thereby causing valve overlap.

  Further, the ECU 40 performs the warm-up increase correction of the fuel injection amount when the engine is warmed up (period from when the engine is started to when warm-up is completed). That is, the ECU 40 calculates the warm-up increase base value Kwbase from engine parameters obtained from various detection signals. Further, an estimated in-cylinder atmosphere temperature (estimated atmosphere temperature in the combustion chamber 23) is calculated from a parameter that includes the valve overlap amount and affects the internal EGR rate and a parameter that affects the estimated internal EGR temperature. The temperature correction coefficient ktemp is calculated from the in-cylinder ambient temperature. Then, the warm-up increase value Kw is calculated by multiplying the calculated warm-up increase base value Kwbase by the temperature correction coefficient ktemp, and the fuel injection amount is increased and corrected by this warm-up increase value Kw.

  More specifically, the ECU 40 calculates the warm-up increase value Kw by the arithmetic logic shown in FIG. 3, and performs the calculation process along the calculation flow shown in FIG. The ECU 40 performs this calculation process every predetermined time.

  In step S101, it is determined whether or not the engine 10 is warming up, that is, during the period during which the engine 10 is warmed up from the start of the engine 10 and the warm-up increase correction of the fuel injection amount is being performed. . If it is determined that the warm-up of the engine 10 has been completed and the warm-up increase correction has not been performed, the process ends. In contrast, if it is determined that the warm-up increase correction is being performed (during the period during which the warm-up increase correction is being performed), the process proceeds to step S102.

  In step S102, a warm-up increase base value Kwbase is calculated. In calculating the warm-up increase base value Kwbase, the calculation result obtained by referring to the two-dimensional map using the cooling water temperature at the start of the engine and the current cooling water temperature, the engine speed and the engine load, and the two-dimensional map By multiplying the calculation result obtained by reference, a base value calculation calculation value K1 is calculated. A vaporized fuel correction coefficient; an atmospheric pressure correction coefficient obtained by referring to the one-dimensional map using the atmospheric pressure; an intake pipe pressure correction coefficient obtained by referring to the one-dimensional map using the intake pipe pressure; A base value calculation calculation value K2 is calculated by multiplying the estimated cylinder temperature obtained by referring to the two-dimensional map using the number of times of combustion after the start and the coolant temperature at the start of the engine. Then, the base value calculation calculation value K2 and the base value calculation calculation value K1 are added to calculate the warm-up increase base value Kwbase.

  In step S103, it is determined whether valve overlap has occurred based on the valve overlap amount. If it is determined that the valve overlap has not occurred, the process proceeds to step S104, where the warm-up increase base value Kwbase is used as it is as the warm-up increase value Kw, and the process ends.

  On the other hand, if it is determined in step S103 that a valve overlap has occurred, the process proceeds to step S105, where a temperature correction coefficient ktemp is calculated. In calculating the temperature correction coefficient ktemp, first, the internal EGR rate obtained by referring to the two-dimensional map using the valve overlap amount and the intake air amount, the ignition timing, and the air-fuel ratio (A / F) are used. The estimated in-cylinder atmosphere temperature is calculated using the estimated internal EGR temperature obtained by referring to the two-dimensional map and the intake air temperature. In this case, the internal EGR amount may be calculated instead of the internal EGR rate, and the estimated in-cylinder atmosphere temperature may be calculated using the internal EGR amount.

Here, when valve overlap occurs, internal EGR occurs, and high-temperature burned gas (EGR gas) remains in the cylinder (inside the combustion chamber 23). Further, the increase in the valve overlap amount promotes an increase in the internal EGR rate in the cylinder (the ratio of the EGR gas in the combustion chamber 23), and this increase in the internal EGR rate promotes an increase in the in-cylinder ambient temperature. . Accordingly, since the valve overlap amount is one of the important factors for calculating the estimated in-cylinder atmosphere temperature, this valve overlap amount is set as one of the parameters for calculating the estimated in-cylinder atmosphere temperature.
And the temperature correction coefficient ktemp is calculated | required from FIG. 4 using the estimated in-cylinder atmosphere temperature calculated in this way.

  FIG. 4 shows the relationship between the estimated in-cylinder atmosphere temperature and the temperature correction coefficient ktemp. Until the estimated in-cylinder atmosphere temperature reaches a predetermined temperature Tlimit which is the maximum value in the normal range, the temperature correction coefficient ktemp is gradually decreased from “1” as the estimated in-cylinder atmosphere temperature increases. This is because the in-cylinder ambient temperature rises as the warm-up of the engine 10 progresses, and the amount of vaporization of fuel wet adhering to the inside of the cylinder and the intake port increases. This is because it is considered that additional fuel is supplied. In an abnormal range where the in-cylinder ambient temperature exceeds the predetermined temperature Tlimit due to excessive increase in the EGR gas in the cylinder and the ignition timing being over-retarded, combustion becomes unstable as the in-cylinder atmosphere temperature increases. become. Therefore, when the calculated estimated in-cylinder atmosphere temperature exceeds the predetermined temperature Tlimit, the temperature correction coefficient ktemp is gradually increased as the estimated in-cylinder atmosphere temperature rises, and eventually becomes greater than “1”.

  Then, the process proceeds to step S106 based on the calculation of the temperature correction coefficient ktemp. In step S106, the warm-up increase value Kw is calculated by multiplying the warm-up increase base value Kwbase by the temperature correction coefficient ktemp, and the process ends. To do.

  In this way, as shown in FIG. 5, the ECU 40 sets the warm-up increase base value Kwbase to the warm-up increase value Kw as it is during the period when the valve overlap does not occur during engine warm-up, and the valve overlap occurs. During the period, the warm-up increase value Kw is obtained by multiplying the warm-up increase base value Kwbase by the temperature correction coefficient ktemp, and the warm-up increase correction of the fuel injection amount is performed based on the warm-up increase value Kw.

  As a result, when the engine warms up, valve overlap begins to occur, and when the valve overlap amount increases, the increase in the internal EGR rate in the cylinder is promoted, and this increase in the internal EGR rate increases the in-cylinder ambient temperature. Promote. Therefore, when the increase in the in-cylinder ambient temperature increases, the amount of vaporization of the fuel wet adhering to the in-cylinder or the intake port increases. Correspondingly, when a valve overlap that promotes an increase in the in-cylinder atmosphere temperature (increase in the internal EGR amount) occurs, a temperature correction coefficient that is made smaller than “1” in accordance with the increase in the in-cylinder atmosphere temperature. Since ktemp is multiplied by the warm-up increase base value Kwbase, the decrease in the warm-up increase value Kw and the increase in vaporization of the fuel wet are offset, and the in-cylinder combustible fuel becomes surplus and becomes rich. Is prevented. As a result, the control accuracy of the air-fuel ratio can be improved, and the exhaust emission is improved.

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

  In the present embodiment, the ECU 40 calculates the warm-up increase base value Kwbase for calculating the warm-up increase value Kw, calculates the estimated in-cylinder atmosphere temperature using the detected valve overlap amount, and calculates the estimated cylinder Calculate the temperature correction coefficient ktemp of the warm-up increase value Kw based on the internal ambient temperature, calculate the warm-up increase value Kw by reflecting the temperature correction coefficient ktemp in the warm-up increase base value Kwbase, and calculate the calculated warm-up increase value The warm-up increase correction of the fuel injection amount is performed based on Kw. That is, in the engine 10 provided with the variable valve mechanisms 25 and 26 as in the present embodiment, internal EGR occurs due to valve overlap, and high temperature burned gas (inside the combustion chamber 23) ( EGR gas) remains. An increase in the valve overlap amount promotes an increase in the internal EGR rate in the cylinder, and an increase in the internal EGR rate promotes an increase in the in-cylinder atmosphere temperature. Thereby, vaporization of fuel wet is promoted, and the fuel that can contribute to combustion increases. For this reason, if the increase in fuel wet vaporization based on the increase in the in-cylinder ambient temperature due to the valve overlap is removed in advance from the warm-up increase value Kw, the fuel that can be combusted in the cylinder will be surplus. Thus, the rich state can be prevented. As a result, the control accuracy of the air-fuel ratio can be improved, and the exhaust emission can be improved.

  In the present embodiment, the ECU 40 calculates the internal EGR rate using the valve overlap amount and the intake air amount, and calculates the estimated in-cylinder atmosphere temperature using the internal EGR rate. That is, as described above, an increase in the valve overlap amount promotes an increase in the internal EGR rate in the cylinder and promotes an increase in the in-cylinder ambient temperature. Therefore, the valve overlap amount and the internal EGR rate are calculated. The estimated in-cylinder atmosphere temperature can be detected with high accuracy by using the intake air amount, which is an important factor for. Therefore, the control accuracy of the air-fuel ratio can be improved more reliably.

  In the present embodiment, the ECU 40 calculates the estimated in-cylinder atmosphere temperature using the internal EGR rate, the estimated internal EGR temperature calculated using the ignition timing and the air-fuel ratio, and the intake air temperature. That is, the in-cylinder atmosphere temperature is calculated based on the internal EGR rate, the internal EGR estimated temperature, and the intake air temperature, which are important factors for calculating the estimated in-cylinder atmosphere temperature. The in-cylinder atmosphere temperature can be detected, and the control accuracy of the air-fuel ratio can be improved more reliably.

  Further, in the present embodiment, the ECU 40 corrects the temperature correction coefficient ktemp so that the warm-up increase value Kw decreases as the estimated in-cylinder atmosphere temperature increases in the normal range until the in-cylinder atmosphere temperature reaches the predetermined temperature Tlimit. Is calculated. In the normal range of the in-cylinder ambient temperature, the in-cylinder ambient temperature rises as the engine 10 warms up, and the amount of vaporized fuel wet adhering to the in-cylinder and the intake port increases. Thus, the combustible fuel in the cylinder is supplemented, so that the control accuracy of the air-fuel ratio can be improved more reliably by reducing the warm-up increase value Kw.

  In the present embodiment, the ECU 40 determines that the warm-up increase amount from the warm-up increase value Kw at the predetermined temperature according to the increase in the estimated in-cylinder atmosphere temperature in the abnormal range where the in-cylinder ambient temperature exceeds the predetermined temperature Tlimit. A temperature correction coefficient ktemp is calculated such that the value Kw increases. In this abnormal range of the in-cylinder atmosphere temperature, the combustion becomes unstable as the in-cylinder atmosphere temperature increases. Therefore, the combustion can be stabilized by increasing the warm-up increase value Kw.

  In addition, this invention is not limited to the content of description of the said embodiment, For example, you may implement as follows.

  In the above embodiment, the warm-up increase value Kw is calculated by the arithmetic logic shown in FIG. 3, but the calculation of the warm-up increase value Kw is not limited to this and may be changed as appropriate. For example, the parameter for calculating the warm-up increase base value Kwbase or the estimated in-cylinder atmosphere temperature, the combination thereof, or the like may be changed as appropriate. In this case, in addition to addition multiplication, subtraction division may be used for calculation. Also, the internal EGR rate (or amount) was calculated from the valve overlap amount, and the estimated in-cylinder atmosphere temperature was calculated based on this internal EGR rate (or amount), the internal EGR estimated temperature, and the intake air temperature. The estimated in-cylinder atmosphere temperature may be calculated directly from the lap amount.

  In the above embodiment, the temperature correction coefficient ktemp is obtained from the relationship between the estimated in-cylinder atmosphere temperature shown in FIG. 4, but the relationship between the estimated in-cylinder atmosphere temperature and the temperature correction coefficient ktemp shown in FIG. 4 is limited to this. It may be changed as appropriate.

It is a block diagram which shows the outline of the engine control system in embodiment of invention. It is a flowchart for calculating the warm-up increase value used at the time of warm-up increase correction. It is a functional block diagram which shows the arithmetic logic for calculating a warm-up increase value. It is a figure which shows the relationship between cylinder atmospheric temperature and a temperature correction coefficient. It is a figure which shows the change of the warming-up increase value until the time of warming-up completion.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 21 ... Intake valve, 22 ... Exhaust valve, 25, 26 ... Variable valve mechanism, 40 ... ECU (base value calculation means, overlap amount detection means, in-cylinder temperature estimation means, temperature correction term calculation means, Warm-up increase value calculation means), Kw ... Warm-up increase value, Kwbase ... Warm-up increase base value, ktemp ... Temperature correction coefficient (temperature correction term), Tlimit ... Predetermined temperature.

Claims (5)

During the warm-up period of the internal combustion engine, which includes a variable valve mechanism that can adjust the valve overlap amount between the intake valve and the exhaust valve, and a fuel injection valve that injects fuel near the intake port of the internal combustion engine. A control device for an internal combustion engine that calculates a warm-up increase value from time to time and performs a warm-up increase correction of a fuel injection amount based on the calculated warm-up increase value,
Base value calculating means for calculating a warm-up increase base value for calculating the warm-up increase value;
An overlap amount detecting means for detecting the valve overlap amount;
In-cylinder temperature estimation means that calculates the estimated in-cylinder atmosphere temperature as the valve overlap amount increases using the detected valve overlap amount;
A temperature correction term calculation means for calculating a temperature correction term of the warm-up increase value based on the calculated estimated in-cylinder atmosphere temperature;
A control apparatus for an internal combustion engine, comprising: a warm-up increase value calculating means for calculating the warm-up increase value by reflecting the temperature correction term on the warm-up increase base value.     The in-cylinder temperature estimating means calculates an internal EGR rate or an internal EGR amount using the valve overlap amount and the intake air amount, and calculates the estimated in-cylinder ambient temperature using the internal EGR rate or the internal EGR amount. The control device for an internal combustion engine according to claim 1.     The in-cylinder temperature estimating means calculates the estimated in-cylinder atmosphere temperature using the internal EGR rate or the internal EGR amount, the estimated internal EGR temperature calculated using the ignition timing and the air-fuel ratio, and the intake air temperature. The control apparatus for an internal combustion engine according to claim 2.     The temperature correction term calculation means calculates the temperature correction term such that the warm-up increase value decreases as the estimated in-cylinder atmosphere temperature increases until the estimated in-cylinder atmosphere temperature reaches a predetermined temperature. The control apparatus for an internal combustion engine according to any one of claims 1 to 3.     When the estimated in-cylinder ambient temperature exceeds a predetermined temperature, the temperature correction term calculating means increases the warm-up increase value from the warm-up increase value at the predetermined temperature in accordance with an increase in the estimated in-cylinder atmosphere temperature. 5. The control apparatus for an internal combustion engine according to claim 4, wherein the temperature correction term is calculated.

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