JP5257400B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine represented by an automobile engine or the like. In particular, the present invention relates to control of an internal combustion engine that includes a variable valve mechanism that can change the working angle of an intake valve and that can perform working angle control to avoid engine stall.

  2. Description of the Related Art Conventionally, an internal combustion engine (hereinafter sometimes referred to as an engine) having a variable valve mechanism that can change the working angle of an intake valve is known (see, for example, Patent Document 1 and Patent Document 2 below). ). This variable valve mechanism changes the operating angle of the intake valve according to the operating state of the engine. For example, when the engine is running at a low speed and a low load, the operating angle of the intake valve is reduced to improve the fuel consumption rate. On the other hand, when the engine is running at high speed and high load, the required angle is secured by increasing the operating angle of the intake valve.

  Further, it is also known to perform “engine stop working angle control” that reduces the working angle of the intake valve in order to avoid engine stall in a situation where the engine speed decreases (for example, a situation where the engine speed decreases below the idling speed). Yes.

  Specifically, when the engine speed has decreased to a predetermined speed, the variable valve mechanism is controlled so as to reduce the operating angle of the intake valve because there is a possibility of engine stall. By reducing the working angle of the intake valve in this way, the closing timing of the intake valve is advanced from the retard side to the vicinity of the suction bottom dead center from the suction bottom dead center of the piston, and the effective compression ratio is increased. Further, the intake valve opening timing is shifted to the retard side from the suction top dead center, and the intake negative pressure at the intake valve opening timing is increased to increase the air filling amount. This increases the in-cylinder temperature when the piston reaches compression top dead center, reduces the amount of fuel adhering to the port wall surface, secures an appropriate air-fuel ratio in the cylinder, and increases the engine speed. The engine stall is avoided.

JP 2003-35167 A JP 2007-297964 A

  However, there is a possibility of incurring the following problems when returning to normal operation angle control (operation angle control according to engine load, etc.) after execution of the above-mentioned “engine avoidance operation angle control”. The inventors of the present invention have found. That is, the present inventors have found that when returning to the normal operation angle control from the “engine avoidance operation angle control”, a phenomenon occurs in which the engine speed decreases again and the possibility of engine stall increases.

  The cause will be described below. When the above-mentioned “engine avoidance operation angle control” is executed, the intake negative pressure increases as described above, the intake flow velocity in the intake port increases, and the amount of fuel injected from the injector on the wall surface of the port decreases. Is done. As a result, the air-fuel ratio in the cylinder is maintained at a stable value, for example, about the stoichiometric air-fuel ratio (stoichiometric). Then, after returning to normal operating angle control, the operating angle of the intake valve increases, but at this time, the intake negative pressure decreases rapidly, the intake air flow velocity in the intake port decreases, and the injector The amount of fuel injected from the fuel to the port wall surface increases rapidly. As a result, the air-fuel ratio in the cylinder largely shifts to the lean side, and the air-fuel ratio becomes unstable. Due to this, it is presumed that the possibility of an engine stall at the time of returning to the normal operating angle control is increased.

  In other words, the fact that the control for avoiding the engine stall (the engine stall avoidance operation angle control) is executed may cause the engine stall when returning to the normal operation angle control thereafter. The inventor of the invention found.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a control device for an internal combustion engine capable of avoiding an engine stall due to execution of engine stall avoidance operation angle control. is there.

-Principle of solving the problem-
The solution principle of the present invention taken to achieve the above object is that, when the wall surface temperature of the intake port is low, the engine stall does not occur when returning to the normal operating angle control after executing the engine stall avoiding operating angle control. If the wall surface temperature of the intake port is low, engine stall avoidance operation angle control is prohibited. In other words, when the engine stall avoidance operating angle control is executed, the wall surface temperature of the intake port is sufficiently high when returning from the engine stall avoidance operating angle control to the normal engine operating angle control. I try not to let you.

-Solution-
Specifically, the present invention is provided with a variable valve mechanism that can change the operating angle of the intake valve, and when a predetermined engine stall avoidance operating angle control execution condition is satisfied, the operating angle of the intake valve is changed to change the engine A control apparatus for an internal combustion engine capable of executing engine stall avoidance operating angle control for increasing the rotational speed is assumed. For the control device of the internal combustion engine, when the wall surface temperature recognition means for detecting or estimating the wall surface temperature of the intake port and the wall surface temperature of the intake port detected or estimated by the wall surface temperature recognition means are less than a predetermined temperature And an engine stall avoidance operation angle control prohibiting means for prohibiting execution of the engine stall avoidance operation angle control even when the engine stall avoidance operation angle control execution condition is satisfied.

  With this specific matter, for example, in a situation where the warm-up operation of the internal combustion engine is completed and the wall surface temperature of the intake port is sufficiently high, the operating angle of the intake valve is increased as the engine stall avoidance operating angle control execution condition is satisfied. Is changed to increase the engine speed, and the engine stall avoidance operation angle control is executed. In this case, when returning to the normal operating angle control after the end avoiding operating angle control is finished, the wall surface temperature of the intake port is sufficiently high, so that fuel adhesion to the wall surface of the intake port is suppressed, and the air-fuel ratio in the cylinder is reduced. It will be secured well and will not cause engine stall.

  On the other hand, for example, at the initial cold start time of the internal combustion engine, in the situation where the wall surface temperature of the intake port is still low and lower than the predetermined temperature, the engine stall avoidance angle control is performed even if the engine stall avoidance angle control execution condition is satisfied. Execution is prohibited. Thus, it is possible to prevent the occurrence of engine stall due to the low wall surface temperature of the intake port when returning to the normal operation angle control after the end avoidance operation angle control is completed.

  As described above, in the present solution, when the engine stall avoidance operating angle control is performed, the wall surface temperature of the intake port after the end is always sufficiently high. It is possible to prevent the engine from being stalled when returning to the state.

  The engine stall avoidance angle control execution condition includes the case where the engine speed has decreased to a predetermined predicted engine stall speed, or the detected or estimated cylinder air-fuel ratio has increased to a predetermined engine stall predicted air-fuel ratio. Is mentioned. In any case, it is possible to recognize the prediction of the engine stall with high accuracy and at a stage before the engine stall.

  The specific operation as the engine stall avoidance operation angle control is to reduce the operation angle of the intake valve by a variable valve mechanism.

  By reducing the operating angle of the intake valve in this way, the opening timing of the intake valve is shifted to the retarded side, and the opening timing is shifted to the retarded side with respect to the suction top dead center of the piston. As a result, the intake valve is closed until the piston moves toward the bottom dead center, so that a large intake negative pressure is obtained at the opening timing of the intake valve. For this reason, after the intake valve is opened, the intake air flows into the cylinder at a high flow rate due to the large differential pressure between the intake port internal pressure and the cylinder internal pressure. The fuel injected from the fuel injection valve flows into the cylinder together with this high flow rate intake air, so that it hardly adheres to the wall surface of the intake port, and most of the fuel injected from the fuel injection valve enters the cylinder. Will be introduced. As a result, the air-fuel ratio in the cylinder does not greatly shift to the lean side, and is maintained at, for example, the theoretical air-fuel ratio.

  Further, by reducing the operating angle of the intake valve, the closing timing of the intake valve is shifted to the advance side and approaches the bottom suction dead center of the piston. As a result, the intake valve is closed from the state where the piston is in the vicinity of the bottom dead center, so that the effective compression ratio is increased. By increasing the effective compression ratio, the amount of air in the cylinder that is compressed in the subsequent compression stroke increases, and in the situation where the piston reaches compression top dead center, both the in-cylinder pressure and the in-cylinder temperature increase. . For this reason, vaporization of the fuel supplied into the cylinder is promoted, and the air-fuel ratio in the cylinder can be brought close to, for example, the stoichiometric air-fuel ratio as the fuel adhesion amount on the bore wall surface decreases. As a result, it is avoided that the air-fuel ratio in the cylinder becomes significantly lean, and combustion in the combustion chamber is favorably performed, so that engine stall is avoided.

  As the wall surface temperature estimating operation by the wall surface temperature recognition means, the wall surface temperature of the intake port is estimated to be higher as the integrated value of the intake air amount is larger.

  Further, it is estimated that the wall surface temperature of the intake port is higher as the integrated value of the intake air amount obtained based on the engine speed and the engine load factor is larger.

  The integrated value of the intake air amount is a value having a correlation with the warm-up state of the internal combustion engine and consequently the wall surface temperature of the intake port. For this reason, the wall surface temperature of the intake port is estimated to be higher as the integrated value of the intake air amount is larger. This makes it possible to estimate the wall surface temperature of the intake port with high accuracy, prohibiting the engine stalling angle control more than necessary (escape avoidance even though the wall surface temperature of the intake port is sufficiently high) The engine stall may occur when returning to the normal working angle control after the engine stall avoidance working angle control is finished (the engine stall is avoided even though the intake port wall temperature is low). By performing the working angle control, it is possible to avoid an engine stall (for example, when returning to the normal working angle control).

  Examples of the timing for starting the engine stall avoidance operating angle control from the state in which the engine stall avoidance operating angle control is prohibited include the following. That is, when the engine stall avoidance angle control execution condition is satisfied, the engine stall avoidance angle control is performed when the wall surface temperature of the intake port detected or estimated by the wall surface temperature recognition means reaches a predetermined temperature or more. I'm trying to get started.

  Thus, the engine stall avoidance operating angle control can be started as early as possible within a range in which engine stall at the time of return of the control is not caused from the state in which engine stall avoidance operating angle control is prohibited.

  In the present invention, for an internal combustion engine capable of executing engine stall avoidance operating angle control for changing the valve operating angle of the intake valve, the engine stall avoidance operating angle control execution condition is satisfied when the wall surface temperature of the intake port is lower than a predetermined temperature. Even so, execution of the engine stall avoidance angle control is prohibited. As a result, it is possible to prevent engine stall when returning to normal working angle control after the end avoidance working angle control is completed.

It is a figure which shows schematic structure of the intake-exhaust system and control system of the engine which concern on embodiment. It is a figure which shows the waveform pattern of the lift amount and working angle of the intake valve which are changed by the variable valve mechanism. FIG. 3A is a diagram showing the opening / closing timing of the intake valve during normal operation, and FIG. 3B is a diagram showing the opening / closing timing of the intake valve during execution of the engine stall avoidance operation angle control. It is a flowchart figure which shows the procedure of execution determination operation | movement of engine avoidance working angle control. It is a flowchart figure which shows 1st Embodiment of wall surface temperature estimation operation | movement. It is a flowchart figure which shows 2nd Embodiment of wall surface temperature estimation operation | movement. It is a figure which shows an example of the table for calculating | requiring a port wall surface temperature estimation parameter | index according to an engine speed and an engine load factor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where the present invention is applied to an in-line four-cylinder gasoline engine for automobiles will be described. In the present embodiment, as shown in FIG. 1, a four-cylinder DOHC engine will be described as an example of an engine mounted on an automobile. However, FIG. 1 shows only the configuration of one cylinder of the engine. The engine may be a diesel engine, and the number of cylinders of the engine may be other than four cylinders. Further, the engine type may be a V type or a horizontally opposed type.

-Outline configuration of engine-
As shown in FIG. 1, the engine according to this embodiment includes a cylinder block 1 and a cylinder head 2. Pistons 4 are accommodated in four cylinders (cylinders) 1a provided in the cylinder block 1 so as to reciprocate.

  A combustion chamber 6 is defined by the cylinder bore, the cylinder head 2 and the piston 4 of each cylinder 1 a of the cylinder block 1. The combustion chamber 6 is supplied with a mixture of air introduced from the intake passage 21 and the intake port 2 a and fuel injected from the injector (fuel injection valve) 7, and this mixture is supplied to the cylinder head 2. It is ignited and burned by the spark discharge of the installed spark plug 8. Due to this combustion, the piston 4 is lowered, and the crankshaft 10 is rotated via the connecting rod 9 to obtain the driving force (torque) of the engine. The exhaust gas after burning in the combustion chamber 6 is discharged from the exhaust port 2b to the exhaust passage 22.

  The intake passage 21 is provided with an air cleaner (not shown) at its upstream end and a throttle valve 5 in the middle thereof. The cylinder head 2 is provided with an intake valve 11 for opening and closing the intake port 2a and an exhaust valve 12 for opening and closing the exhaust port 2b. Both the intake valve 11 and the exhaust valve 12 are urged by valve springs 11a and 12a in the direction of closing the intake port 2a and the exhaust port 2b.

  The intake valve 11 is opened and closed by an intake camshaft 13 and the exhaust valve 12 is opened and closed by an exhaust camshaft 14, respectively. The intake camshaft 13 is provided with a cam lobe 13 a for opening and closing the intake valve 11. The exhaust camshaft 14 is provided with a cam lobe 14a for opening and closing the exhaust valve 12.

  The intake side camshaft 13 and the exhaust side camshaft 14 are rotatably supported by the cylinder head 2. Sprockets are respectively attached to one end portions of the camshafts 13 and 14 and the crankshaft 10 in the axial direction, and timing chains are spanned around these sprockets. Therefore, when the crankshaft 10 rotates, the rotation is transmitted to the camshafts 13 and 14 through the sprockets and timing chains, and the camshafts 13 and 14 rotate to open and close the valves 11 and 12. It is supposed to be. A pulley and a timing belt may be used instead of the sprocket and the timing chain.

  Rocker arms having rollers 17a between the upper end portion of the intake valve 11 and the cam lobe 13a of the intake side camshaft 13 and between the upper end portion of the exhaust valve 12 and the cam lobe 14a of the exhaust side camshaft 14, respectively. Reference numeral 17 denotes a swingable arrangement. In addition, hydraulic lash adjusters 18 are disposed in the vicinity of the upper ends of the intake valve 11 and the exhaust valve 12, respectively. The rocker arm 17 is subjected to the compression reaction force of the valve springs 11 a and 12 a and the push-up force of the lash adjuster 18. Thereby, the roller 17a of the rocker arm 17 is urged substantially upward. The roller 17a is in direct contact with the cam lobe 14a of the exhaust side camshaft 14, while the variable valve mechanism 30 described below is applied to the cam lobe 13a of the intake side camshaft 13. Via indirect contact.

-Configuration of variable valve mechanism 30-
The engine according to the present embodiment is provided with the variable valve mechanism 30 for making the operating angle of the intake valve 11 variable.

  As shown in FIG. 2, the operating angle of the intake valve 11 is a valve opening period of the intake valve 11 with respect to the rotation direction of the intake camshaft 13 (expressed as a crank angle in FIG. 2). The variable valve mechanism 30 according to the present embodiment is configured such that the maximum lift amount is continuously changed as the operating angle of the intake valve 11 is changed. The maximum lift amount is a movement amount when the intake valve 11 moves (lifts) to the lowest position. These working angles and the maximum lift amount are changed in synchronization with each other by the variable valve mechanism 30. For example, the smaller the working angle, the smaller the maximum lift amount. As the operating angle decreases, the valve opening timing and the valve closing timing of the intake valve 11 approach each other, and the valve opening period becomes shorter.

  As shown in FIG. 1, the variable valve mechanism 30 includes a mediation drive mechanism 31 for each cylinder 1 a and a control shaft 32 common to all mediation drive mechanisms 31. The control shaft 32 is disposed so as to extend in a direction orthogonal to the paper surface of FIG. 1, but here, for convenience of explanation, the control shaft 32 is turned so that a part of the control shaft 32 extends in the left-right direction of the paper surface. Show.

  Each mediation drive mechanism 31 includes an input arm 33 and an output arm 34 on a control shaft 32 as disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-255851, and the control shaft 32 and the arms 33 and 34. A slider gear 35 for power transmission interposed therebetween is provided.

  When the intake camshaft 13 rotates, in the variable valve mechanism 30, the input arm 33 swings up and down around the control shaft 32 as a swing center. This swing is transmitted to the output arm 34 via the slider gear 35, and the output arm 34 swings up and down. By this swinging output arm 34, the intake valve 11 is pushed down against the urging force of the valve spring 11a to open.

  An electric actuator 36 for moving the control shaft 32 in the axial direction is connected to the control shaft 32. The electric actuator 36 includes an electric motor 37 and a rotary linear motion conversion mechanism 38 that converts the rotation of the electric motor 37 into a linear motion and transmits the linear motion to the control shaft 32. When the control shaft 32 is displaced in the axial direction along with the rotation of the electric motor 37, the variable valve mechanism 30 rotates while the slider gear 35 is displaced in the same direction, and the input arm 33 and the output arm 34 are swung in the swing direction. These relative phase differences are changed.

  In this embodiment, when the electric motor 37 is rotated in a predetermined direction and the control shaft 32 is displaced to the variable valve mechanism 30 side (the right side in FIG. 1), the input arm 33 and the output arm 34 swing. The relative position in the direction is changed so as to approach each other, and the relative phase difference is reduced. Further, when the electric motor 37 is rotated in the opposite direction to displace the control shaft 32 to the electric actuator 36 side (left side in FIG. 1), the swinging direction of the input arm 33 and the output arm 34 is changed. The relative positions are changed so as to be separated from each other, and the relative phase difference is increased.

  The working angle of each intake valve 11 continuously changes with the change of the relative phase difference in the swing direction of the input arm 33 and the output arm 34. The working angle decreases when the relative phase difference is small, whereas the working angle increases when the relative phase difference increases.

  In the engine according to the present embodiment, a pair that regulates the movable range of the variable valve mechanism 30 by contact with any movable part (for example, the control shaft 32) in the power transmission path from the electric motor 37 to the output arm 34. Stoppers 41 and 42 are provided. The variable valve mechanism 30 operates within this movable range to change the operating angle of the intake valve 11. With respect to both end positions of this movable range, that is, positions where the control shaft 32 contacts the stoppers 41 and 42 (movable limit positions), the movable limit position on the side where the operating angle is reduced is expressed as “Lo end”, and the operating angle is expressed as The movable limit position on the larger side is expressed as “Hi end”. The variable valve mechanism 30 cannot be operated to a side where the operating angle is smaller than the “Lo end” due to contact with the stopper 42, and the operating angle is set to be greater than that of the “Hi end” due to contact with the stopper 41. Cannot operate on the larger side. When restricting the movable range of the variable valve mechanism 30 by the both stoppers 41 and 42, in addition to restricting the stroke of the control shaft 32, the rotation amount of the electric motor 37 is also restricted.

  As described above, since the intake air amount can be adjusted by changing the operating angle of the intake valve 11, the same intake air amount can be realized by various combinations of the throttle opening and the operating angle of the intake valve 11. Is possible. For example, when the operating angle of the intake valve 11 is increased, the throttle opening is relatively reduced, and conversely, when the operating angle of the intake valve 11 is decreased, the throttle opening is relatively increased, so It is possible to keep the intake air amount constant.

  In adjusting the intake air amount, when reducing the intake air amount by reducing the operating angle of the intake valve 11, the intake air amount is decreased by reducing only the opening of the throttle valve 5. In comparison, the pumping loss can be reduced. Therefore, it becomes possible to suppress the output loss of the engine, and the fuel consumption rate can be improved.

  Various sensors are attached to each part of the engine in the present embodiment, and signals related to the environmental conditions of each part and the operating state of the engine are output. As these sensors, for example, a crank angle sensor 111, a cam angle sensor 112, a rotation angle sensor 113, an air flow meter 114, an accelerator opening sensor 115, a throttle opening sensor 116, and the like are used.

  The crank angle sensor 111 generates a pulse signal every time the crankshaft 10 rotates by a certain angle. This signal is used to calculate the crank angle, which is the rotation angle of the crankshaft 10, and the rotation speed of the crankshaft 10 per unit time (hereinafter also referred to as engine rotation speed).

  The cam angle sensor 112 is provided in the vicinity of the intake side camshaft 13 and detects the rotation angle (cam angle) of the intake side camshaft 13.

  The rotation angle sensor (working angle sensor) 113 detects the current value of the working angle of the intake valve 11, in other words, the operating position of the variable valve mechanism 30.

  The air flow meter 114 detects the amount of air flowing through the intake passage 21 (intake air amount). The accelerator opening sensor 115 detects the amount of depression of the accelerator pedal 25 by the driver. The throttle opening sensor 116 is provided in the vicinity of the throttle valve 5 and detects the opening of the throttle valve 5 (throttle opening).

  The rotation angle sensor 113 only needs to be able to detect the operation position of any movable part in the power transmission path from the electric motor 37 to the output arm 34. In this embodiment, the electric motor 37 rotates by a certain angle. An encoder that outputs a pulse signal every time, that is, every time the variable valve mechanism 30 operates by a certain amount, is used. Then, the rotation angle of the electric motor 37 is detected by counting the pulse signals, and based on this rotation angle, the operating position of the variable valve mechanism 30 and thus the actual operating angle (actual operating angle) of the intake side camshaft 13. Is calculated.

  In addition, the vehicle is provided with an electronic control unit (engine ECU) 100 that controls driving of each unit based on detection signals of the various sensors 111 to 116 and the like. The electronic control device 100 is configured around a microcomputer, and a central processing unit (CPU) performs arithmetic processing according to a control program, initial data, a control map, and the like stored in a read-only memory (ROM). Various controls are executed based on the calculation results. The calculation result by the CPU is temporarily stored in a random access memory (RAM).

  Moreover, the electronic control apparatus 100 controls the fuel injection from this injector 7, for example by controlling the electricity supply with respect to the injector 7. FIG. In this fuel injection control, the fuel injection amount for setting the air-fuel ratio of the air-fuel mixture to a predetermined value is calculated as the basic injection amount (basic injection time) based on the engine operating conditions such as the engine speed and the engine load. The engine load is obtained based on, for example, the intake air amount of the engine or parameters related thereto (for example, throttle opening, accelerator depression amount, etc.). The basic injection amount thus obtained is corrected based on the signals from the sensors 111 to 116, and the injector 7 is energized for a time corresponding to the corrected injection amount. By this energization, the injector 7 is opened, and the corrected amount of fuel is injected.

  The electronic control unit 100 performs the following control when adjusting the intake air amount. First, a control target value (required intake air amount) for the air amount is calculated from the map based on the engine operating state, for example, the accelerator depression amount and the engine speed. In the map, the relationship between the engine operating state determined by the accelerator depression amount and the engine speed and the intake air amount corresponding to the engine operating state is obtained and set in advance through experiments or the like.

  Subsequently, a control target value for the throttle opening (target throttle opening) and a control target value for the operating angle (target operating angle) are calculated through different map calculations based on the required intake air amount and the engine speed. To do. In each map used for the map calculation, the relationship between the engine operating state determined by the required intake air amount and the engine speed and the control target value suitable for the engine operating state is obtained and set in advance through experiments or the like. ing. Here, a control target position (control target position of the electric motor 37) required for the variable valve mechanism 30 in order to realize the target operating angle is calculated.

  Then, drive control (throttle control) of the throttle motor 16 is executed so that the actual throttle opening matches the target throttle opening, and the actual operating angle of the intake valve 11 matches the target operating angle. Drive control of the electric motor 37 is executed.

-Engine angle control-
Next, engine stall avoidance operating angle control will be described. This is a control operation in which the operating angle of the intake valve 11 is reduced by the variable valve mechanism 30 in order to avoid engine stall in a situation where the engine speed decreases (for example, a situation where the engine speed decreases below the idling speed). This will be specifically described below.

  When the engine speed calculated based on the signal from the crank angle sensor 111 decreases to a predetermined speed (for example, 500 rpm), the electronic control unit 100 determines that there is a possibility of engine stall, and the electronic control unit 100 operates the intake valve 11. The variable valve mechanism 30 is controlled to reduce the angle. That is, the electric motor 37 is driven to displace the control shaft 32 to the variable valve mechanism 30 side (the right side in FIG. 1). As a result, the relative positions of the input arm 33 and the output arm 34 in the swing direction are changed so as to approach each other, and the relative phase difference is reduced. In this way, the working angle of the intake valve 11 decreases as the relative phase difference decreases.

  FIG. 3 is a diagram showing the opening / closing timing of the intake valve 11 corresponding to the crank rotation position. That is, TDC in FIG. 3 indicates the crank rotation position corresponding to the suction top dead center of the piston 4, and BDC indicates the crank rotation position corresponding to the suction bottom dead center of the piston 4. 3A shows an example of the opening / closing timing of the intake valve 11 during normal control, and FIG. 3B shows an example of the opening / closing timing of the intake valve 11 during execution of engine stall avoidance operating angle control. .

  As shown in FIG. 3, the opening timing of the intake valve 11 during normal control is set near the suction top dead center (slightly advanced from the suction top dead center) (FIG. 3A). See the opening timing shown in

  When the engine stall avoidance operation angle control is started from this state, the opening timing of the intake valve 11 is shifted to the retard side as the operation angle becomes smaller (see the opening timing shown in FIG. 3B). The opening timing is shifted to the retard side from the top dead center. Thus, the intake valve 11 is closed until the piston 4 moves toward the bottom dead center (until the position corresponding to the predetermined crank angle is reached from the suction top dead center). A large negative suction pressure at the opening timing can be obtained. For this reason, after the intake valve 11 is opened, intake air flows into the cylinder 1a at a high flow rate due to the large differential pressure between the internal pressure of the intake port 2a and the cylinder internal pressure. The fuel injected from the injector 7 flows into the cylinder 1a together with this high flow rate intake air, so that it hardly adheres to the wall surface of the intake port 2a, and most of the fuel injected from the injector 7 is in the cylinder 1a. Will be introduced. As a result, the air-fuel ratio in the cylinder 1a is not greatly shifted to the lean side, and is maintained at, for example, the theoretical air-fuel ratio. In addition, the swirl flow and the tumble flow in the cylinder 1a can be greatly obtained by increasing the flow velocity of the intake air, the fuel vaporization is promoted, and a substantially uniform mixture is generated throughout the cylinder 1a. Will be.

  In addition, the closing timing of the intake valve 11 during normal control is set to a relatively large delay side with respect to the suction bottom dead center (see the closing timing shown in FIG. 3A).

  When the engine stall avoidance operation angle control is started from this state, the closing timing of the intake valve 11 is shifted to the advance side as the operation angle becomes smaller (see the closing timing shown in FIG. 3B). The closing timing approaches the bottom dead center of inhalation. Thereby, since the intake valve 11 is closed from the state where the piston 4 is in the vicinity of the bottom dead center, the effective compression ratio is increased. By increasing the effective compression ratio, the amount of air (air filling amount) in the cylinder 1a to be compressed in the subsequent compression stroke increases, and in the situation where the piston 4 has reached the compression top dead center, Both pressure and in-cylinder temperature increase. For this reason, the vaporization of the fuel supplied into the cylinder is promoted, and the air-fuel ratio in the cylinder can be brought close to, for example, the theoretical air-fuel ratio as the amount of fuel attached to the bore wall surface decreases. It is avoided that the air-fuel ratio in 1a becomes significantly lean.

  Thus, by executing the engine stall avoidance operation angle control such as reducing the operation angle of the intake valve 11, the combustion in the combustion chamber 6 is favorably performed, and the engine stall is avoided.

-Execution judgment operation of engine stall avoidance angle control-
Next, an execution determination operation for engine stall avoidance operating angle control, which is an operation characteristic of the present embodiment, will be described. This operation is an operation for determining whether the engine stall avoidance angle control is executed or not. Specifically, the wall surface temperature of the intake port 2a is estimated, and the wall surface temperature of the intake port 2a is less than the predetermined temperature even when the engine speed decreases to a predetermined speed (for example, 500 rpm). In the case of the estimated situation, the execution of the engine stall avoidance operation angle control described above is prohibited (the engine stall avoidance operation angle control is not executed). That is, the engine stall avoidance angle control described above is executed only when it is estimated that the wall surface temperature of the intake port 2a has reached a predetermined temperature or higher in a state where the engine speed has decreased to a predetermined speed.

  Hereafter, the procedure of this operation | movement is demonstrated along the flowchart of FIGS. The flowchart shown in FIG. 4 is a main routine of the execution determination operation for the engine stall avoidance operating angle control. In addition, the flowchart shown in FIG. 5 is a first implementation of the wall surface temperature estimating operation for estimating the wall surface temperature of the intake port 2a used when determining whether to execute and prohibit the engine stall operation angle control in the main routine. It is a flowchart which shows a form. Further, the flowchart shown in FIG. 6 shows a second implementation of the wall surface temperature estimating operation for estimating the wall surface temperature of the intake port 2a used when determining whether to execute and prohibit the engine stall operation angle control in the main routine. It is a flowchart figure which shows a form.

<First Embodiment of Wall Surface Temperature Estimation Operation>
First, a first embodiment of a procedure (wall surface temperature estimation routine) for estimating the wall surface temperature of the intake port 2a will be described with reference to FIG. The processing shown in this flowchart is repeatedly executed by the electronic control device 100 at a predetermined cycle (for example, every 16 msec).

  First, in step ST11, it is determined whether or not the engine start flag is set to “1”. This engine start flag is reset to “0” when the engine is not started, and is set to “1” when the engine is started by an ignition ON operation or the like.

  If the engine has not yet been started and the engine start flag has been reset to “0”, a NO determination is made in step ST11 and the process proceeds to step ST12. In step ST12, it is determined whether or not an ignition ON operation has been performed, that is, whether or not the engine has been started. If the ignition ON operation is not performed and the engine is still stopped, NO is determined in step ST12 and the process returns.

  On the other hand, when the ignition ON operation is performed and the engine starts, YES is determined in step ST12 and the process proceeds to step ST13. In step ST13, the intake air amount detected by the air flow meter 114 is read.

  Thereafter, the process proceeds to step ST14, where the intake air amount (Gp) read in step ST13 is added to the integrated value (Gm) of the intake air amount accumulated up to the previous routine, and this is added to the new intake air amount. Is stored as an integrated value (Gm). The integrated value (Gm) of the intake air amount is set to “0” when the engine is started, and is added in step ST14 every time the intake air amount (Gp) is read in step ST13. is there.

  In step ST15, it is determined whether or not an ignition OFF operation has been performed, that is, whether or not the engine has been stopped. If the ignition OFF operation is not performed and the engine driving state is continued, NO is determined in step ST15 and the process returns.

  In this case, since the engine start flag is already set to “1”, the determination in step ST11 is YES, and the intake air amount reading operation in step ST13 described above and the integrated value (Gm) of the intake air amount in step ST14 are determined. A calculation operation is performed.

  This operation is repeated until the ignition OFF operation is performed, that is, until YES is determined in step ST15, and the integrated value (Gm) of the intake air amount increases.

  When the ignition OFF operation is performed and the engine is stopped, and YES is determined in step ST15, the process proceeds to step ST16, and the engine start flag is reset to “0”. Thereafter, the integrated value (Gm) of the intake air amount is reset to “0” in step ST17.

  In this way, in the wall surface temperature estimation routine, the read intake air amount (Gp) is sequentially added during the period from the engine start to the engine stop, and the integrated value (Gm) of the intake air amount is obtained. It will be done.

  The integrated value (Gm) of the intake air amount is obtained as a value correlated with the warm-up state of the engine and consequently the wall surface temperature of the intake port 2a. That is, as the integrated value (Gm) of the intake air amount is larger, it can be estimated that the wall surface temperature of the intake port 2a is higher, and the fuel is less likely to adhere to the wall surface of the intake port 2a. It is estimated that the fuel evaporates in a relatively short time even if the fuel adheres. For this reason, the operations in steps ST13 and ST14 described above correspond to the wall surface temperature estimation operation of the intake passage by the wall surface temperature recognition means in the present invention.

<Second Embodiment of Wall Surface Temperature Estimation Operation>
Next, a second embodiment of the procedure for estimating the wall surface temperature of the intake port 2a (wall surface temperature estimation routine) will be described with reference to FIG. The processing shown in this flowchart is repeatedly executed by the electronic control device 100 at a predetermined cycle (for example, every 16 msec).

  First, in step ST21, it is determined whether or not the engine start flag is set to “1”.

  If the engine has not yet been started and the engine start flag has been reset to “0”, a NO determination is made in step ST21 and the process proceeds to step ST22. In step ST22, it is determined whether or not an ignition ON operation has been performed, that is, whether or not the engine has been started. If the ignition ON operation is not performed and the engine remains stopped, NO is determined in step ST22 and the process returns.

  On the other hand, when the ignition ON operation is performed and the engine is started, YES is determined in step ST22 and the process proceeds to step ST23. In step ST23, the engine speed and the engine load factor are read. The engine speed is calculated based on the pulse signal output from the crank angle sensor 111. The engine load factor is a value indicating the current load ratio with respect to the maximum engine load of the engine. For example, refer to a load factor map based on the intake air amount detected by the air flow meter 114 and the engine speed. Is required. Alternatively, it is calculated based on the throttle opening detected by the throttle opening sensor 116, the accelerator depression amount detected by the accelerator opening sensor 115, and the like.

  Thereafter, the process proceeds to step ST24, where the port wall surface temperature estimation index (Tp) is acquired based on the read engine speed and engine load factor. This port wall surface temperature estimation index (Tp) is obtained from, for example, the port wall surface temperature estimation index table written in the ROM. FIG. 7 shows an example of the port wall surface temperature estimation index table. As shown in FIG. 7, the port wall surface temperature estimation index table is used to obtain the port wall surface temperature estimation index from the engine speed (vertical axis in FIG. 7) and the engine load factor (horizontal axis in FIG. 7). Yes, the higher the engine speed, the higher the port wall temperature estimation index, and the higher the engine load factor, the higher the port wall temperature estimation index.

  For example, when the engine speed is 1000 rpm and the engine load factor is 20%, “1.0” is acquired as the port wall surface temperature estimation index, and when the engine speed is 3000 rpm and the engine load factor is 60%. In some cases, “4.0” is acquired as the port wall surface temperature estimation index, and when the engine speed is 5000 rpm and the engine load factor is 80%, the port wall temperature estimation index is “6.0. "Will be acquired. When the engine speed and the engine load factor are values between the values indicated on the port wall surface temperature estimation index table (for example, the engine speed is 1500 rpm and the engine load factor is 30%). In such a case, the port wall surface temperature estimation index is calculated by a predetermined interpolation calculation.

  After the port wall surface temperature estimation index is calculated in this way, in step ST25, the port wall surface temperature estimation obtained in step ST24 is added to the current estimated index integrated value (Tm) stored in advance in the RAM or the like. The index (Tp) is added and stored as a new estimated index integrated value (Tm). This estimated index integrated value (Tm) is set to “0” when the engine is started, and is added at step ST25 every time the port wall surface temperature estimated index (Tp) is acquired at step ST24. It is.

  In step ST26, it is determined whether or not an ignition OFF operation has been performed, that is, whether or not the engine has been stopped. If the ignition OFF operation is not performed and the engine drive state is continued, NO is determined in step ST26 and the process returns.

  In this case, since the engine start flag has already been set to “1”, a YES determination is made in step ST21, the engine speed and engine load factor reading operation in step ST23 described above, and the port wall surface temperature estimation index (step ST24) An operation of obtaining Tp) and an operation of calculating the estimated index integrated value (Tm) in step ST25 are performed.

  This operation is repeated until the ignition OFF operation is performed, that is, until YES is determined in step ST26, and the estimated index integrated value (Tm) is increased.

  When the ignition OFF operation is performed and the engine is stopped, and YES is determined in step ST26, the process proceeds to step ST27, and the engine start flag is reset to “0”. Thereafter, the estimated index integrated value (Tm) is reset to “0” in step ST28.

  In this way, in this wall surface temperature estimation routine, the port wall surface temperature estimation index (Tp) obtained based on the engine speed and the engine load factor is sequentially added during the period from engine start to engine stop. The estimated index integrated value (Tm) is obtained.

  This estimated index integrated value (Tm) is a value correlated with the intake air amount of the engine, and as a result, is obtained as a value correlated with the warm-up state of the engine and consequently the wall surface temperature of the intake port 2a. That is, as the estimated index integrated value (Tm) is larger, it can be estimated that the wall surface temperature of the intake port 2a is higher, and it is difficult for the fuel to adhere to the wall surface of the intake port 2a or the fuel adheres. Even so, it is estimated that the fuel evaporates in a relatively short time. For this reason, the above-described operation of step ST23 to step ST25 (operation for calculating the estimated index integrated value (Tm)) corresponds to the wall surface temperature estimation operation of the intake passage by the wall surface temperature recognition means referred to in the present invention.

<Execution judgment operation of engine stall avoidance angle control>
Next, the execution determination operation of the engine stall avoidance operating angle control using the estimated index integrated value (Tm) obtained by the wall surface temperature estimation routine (FIG. 6) described above will be described with reference to the flowchart of FIG. Here, the execution determination operation of the engine stall avoidance operating angle control using the estimated index integrated value (Tm) will be described. However, the engine stall avoidance operating angle control execution determination using the integrated value (Gm) of the intake air amount is described. An operation may be performed. In this case, the following “estimated index integrated value (Tm)” is read as “intake air amount integrated value (Gm)”, and the following “estimated index threshold (Tthr)” is “intake air amount threshold”. Will be read as

  The process shown in the flowchart of FIG. 4 is repeatedly executed by the electronic control device 100 at a predetermined cycle (for example, every 16 msec), and is performed in parallel with the wall surface temperature estimation routine.

  In the execution determination operation for the engine stall avoidance operating angle control, first, in step ST1, it is determined whether or not the engine start flag is set to “1”.

  If the engine has not yet been started and the engine start flag has been reset to “0”, a NO determination is made in step ST1 and the process proceeds to step ST10. In step ST10, the operating angle control execution flag is reset to “0”. This working angle control execution flag is a flag that is set to “1” (set in step ST7) when the engine stall avoidance working angle control is executed.

  On the other hand, if the engine is started and YES is determined in step ST1, the process proceeds to step ST2 where the engine speed (Ne) is read. That is, the engine speed (Ne) is calculated based on the pulse signal output from the crank angle sensor 111.

  Thereafter, in step ST3, whether the calculated engine speed (Ne) has decreased to a preset engine stall estimated engine speed (Nst: engine stall predicted engine speed) or less (engine stall avoidance operating angle control). Whether or not the execution condition is satisfied). The engine stall prediction engine speed (Nst) is set to a value (for example, 500 rpm) lower than the idling speed, for example. In other words, the situation in which the engine speed (Ne) drops below the engine predicted engine speed (Nst) is a state in which engine stall may occur thereafter. In step ST3, engine stall is possible. Judging the presence or absence of sex.

  If the engine speed (Ne) has decreased below the engine predicted engine speed (Nst) and the determination is YES in step ST3, the routine proceeds to step ST4, where the wall temperature estimation routine (FIG. 6) is used. It is determined whether or not the current estimated index integrated value (Tm) being set is equal to or greater than a preset estimated index threshold value (Tthr) (or obtained by the wall surface temperature estimation routine (FIG. 5)). It is determined whether the integrated value (Gm) of the current intake air amount is equal to or greater than a preset intake air amount threshold value). The estimated index threshold value (Tthr) is arbitrarily set according to the number of cylinders and the displacement of the engine, and is set to “500”, for example. The estimated index threshold value (Tthr) is a value corresponding to the integrated intake air amount until the coolant temperature after starting reaches about 20 ° C. when the engine is cold started, for example, when the outside air temperature is 0 ° C. Set as The intake air amount threshold value is set in the same manner.

  If the estimated index threshold value (Tthr) is set to a value larger than necessary (or the intake air amount threshold value is set to a value larger than necessary), engine stall avoidance operation angle control is started. Engine stall (before YES is determined in step ST4). For this reason, this estimated index threshold value (Tthr) (or intake air amount threshold value) must be set as a value at which the wall surface temperature of the intake port 2a reaches a temperature (for example, 30 ° C.) that exhibits a certain degree of fuel adhesion suppression effect. There is. This is appropriately set by experiment or simulation according to the engine displacement or the number of cylinders.

  As described above, the estimated index integrated value (Tm) (or the integrated value (Gm) of the intake air amount) is a value that gradually increases as the engine is continuously operated. At the initial stage, the estimated index integrated value (Tm) is less than the estimated index threshold (Tthr) (or the intake air amount integrated value (Gm) is less than the intake air amount threshold). For this reason, in a situation where the engine speed (Ne) decreases to the engine predicted engine speed (Nst) or less at the initial cold start of the engine, YES is determined in step ST3 and NO is determined in step ST4, and engine stall is avoided. The operating angle control is returned without being executed. That is, conventionally, even in a situation where engine stall avoidance operating angle control is executed (previously engine stall avoidance operating angle control has been executed only on condition that the engine speed has decreased to a predetermined engine speed), In the embodiment, on the condition that the estimated index integrated value (Tm) is less than the estimated index threshold value (Tthr) (or the intake air amount integrated value (Gm) is less than the intake air amount threshold value. The execution of the engine stall avoidance operating angle control is prohibited (provided that the engine stall avoidance operating angle control is prohibited by the engine stall avoidance operating angle control prohibiting means).

  In this way, the engine is continuously operated in a situation where the execution of the engine stall avoidance operating angle control is prohibited, and the estimated index integrated value (Tm) obtained in the wall surface temperature estimation routine increases, and this estimation is performed. When the index integrated value (Tm) exceeds the estimated index threshold (Tthr) (or the integrated value (Gm) of the intake air amount increases, the integrated value (Gm) of the intake air amount exceeds the intake air amount threshold. Then, YES is determined in step ST4, and the operation proceeds to step ST5 and subsequent steps.

  In step ST5, it is determined whether the operating angle control execution flag is “0”, that is, whether engine stall avoiding operating angle control has not yet been started. If the working angle control execution flag is “0” and YES is determined in step ST5, the process proceeds to step ST6 to start the engine stall avoidance working angle control. That is, the variable valve mechanism 30 reduces the operating angle of the intake valve 11 and stabilizes the air-fuel ratio by increasing the intake air flow velocity resulting from shifting the opening timing of the intake valve 11 to the retarded angle side. Control for avoiding engine stall is executed by increasing the effective compression ratio caused by advancing the closing timing of 11 toward the suction bottom dead center.

  With the start of the engine stall avoidance operation angle control, the operation angle control execution flag is set to “1” in step ST7, and the process returns.

  When the engine stall avoidance angle control is started in this way, the engine stall avoidance action is performed until the engine speed (Ne) becomes higher than the engine stall predicted engine speed (Nst) (until NO is determined in step ST3). Angular control will continue. In this case, a NO determination is made at step ST5 and the process returns.

  If the engine speed (Ne) becomes higher than the engine predicted engine speed (Nst) and NO is determined in step ST3, the process proceeds to step ST8, and whether or not the operating angle control execution flag is set to “1”. Determine. That is, it is determined whether the engine stall avoidance angle control is currently being executed. If the engine stall avoidance operating angle control is being executed and YES is determined in step ST8, the routine proceeds to step ST9 where the engine stall avoidance operating angle control is canceled (stopped). That is, the engine speed (Ne) is higher than the engine predicted engine speed (Nst), and it is determined that there is no risk of engine stall, and engine stall avoidance operating angle control is canceled. Thereafter, in step ST10, the operating angle control execution flag is reset to “0”.

  On the other hand, when the engine is stopped due to the ignition OFF operation being performed during the engine stall avoidance operation angle control, a NO determination is made in step ST1 while the operation angle control execution flag remains set to “1”. . In this case, as described above, the working angle control execution flag is reset to “0” in step ST10, and the engine is stopped.

  As described above, in the present embodiment, the condition that the engine speed (Ne) has decreased to the engine predicted engine speed (Nst) or less in a situation where the estimated wall surface temperature of the intake port 2a is sufficiently high. The engine stall avoidance angle control is executed as the engine stall avoidance angle control execution condition.

  On the other hand, at the initial cold start of the engine or the like, the estimated wall surface temperature of the intake port 2a is still low and less than a predetermined temperature (the estimated index integrated value (Tm) is less than the estimated index threshold (Tthr)). In the situation, even if the engine speed (Ne) falls below the engine predicted engine speed (Nst) (even if the engine stall avoidance operating angle control execution condition is satisfied), the engine stall avoidance operating angle control is prohibited. Yes. As a result, it is possible to prevent the occurrence of engine stall due to the low wall surface temperature of the intake port 2a after the end avoidance operation angle control is finished and when returning to the normal operation angle control.

  Thus, in this embodiment, when the engine stall avoidance operating angle control is performed, the wall surface temperature of the intake port 2a after the end is always sufficiently high. For this reason, it is possible to prevent an engine stall caused by a large fluctuation in the air-fuel ratio when returning to the normal working angle control, and a malfunction caused by the execution of the engine stall avoidance working angle control (to the above normal working angle control). (Occurrence of engine stall at the time of return) can be avoided.

(Modification)
Next, a modification of the present invention will be described. In this modification, the engine stall avoidance operating angle control execution condition is different from that in the above embodiment. Since the configuration and control of other engines are the same as those in the above embodiment, only differences from the above embodiment will be described here.

  In the above embodiment, the engine stall avoidance operating angle control execution condition is satisfied when the engine speed (Ne) is reduced to the engine predicted engine speed (Nst) or less. Instead of this, the engine stall avoidance angle control execution condition is established when the air-fuel ratio in the cylinder 1a rises to a predetermined engine stall predicted air-fuel ratio (shifts to the lean side).

  Specifically, the air-fuel ratio in the cylinder 1a is estimated by detecting the oxygen concentration in the exhaust gas from the output signal of an A / F sensor (not shown) provided in the exhaust passage 22. When the estimated air-fuel ratio is equal to or higher than a predetermined air-fuel ratio (for example, air-fuel ratio 20.0), it is determined that there is a possibility of engine stall.

  Also in the present modified example, when the estimated wall surface temperature of the intake port 2a is sufficiently high, the condition that the air-fuel ratio in the cylinder 1a has increased to the engine stall predicted air-fuel ratio (condition for executing the engine stall avoidance operation angle control) ) To perform engine stall avoidance operation angle control. On the other hand, at the initial cold start of the engine or the like, the estimated wall surface temperature of the intake port 2a is still low and less than a predetermined temperature (the estimated index integrated value (Tm) is less than the estimated index threshold (Tthr), or In a situation where the integrated value (Gm) of the intake air amount is less than the intake air amount threshold), even if the air-fuel ratio in the cylinder 1a rises to the predicted engine stall air-fuel ratio (the engine stall avoidance operating angle control execution condition is satisfied). Even) Execution of engine stall avoidance angle control is prohibited. As a result, as in the case of the above-described embodiment, after the engine stall avoidance operation angle control is finished and when returning to the normal operation angle control, the engine stall due to the low wall temperature of the intake port 2a is prevented. Can be prevented. Also in the present modification, it is possible to recognize the engine stall prediction with high accuracy and at a stage before the engine stall.

(Other embodiments)
In the embodiment and the modification described above, the case where the present invention is applied to an engine mounted on an automobile has been described. The present invention is not limited to this, and can also be applied to an engine mounted on a device other than an automobile.

  In the embodiment and the modification described above, the case where the present invention is applied to the engine including the variable valve mechanism 30 only for the intake valve 11 has been described. The present invention is not limited to this, and can be applied to an engine provided with a variable valve mechanism for the exhaust valve 12 as well.

  In the embodiment and the modification, the wall surface temperature of the intake port 2a is estimated from the integrated value (Gm) and estimated index integrated value (Tm) of the intake air amount. The temperature may be detected directly. For example, the structure etc. which attach temperature sensors, such as a thin film thermocouple, to the wall surface of the intake port 2a are mentioned. In this case, the temperature sensor is attached to the downstream side of the intake port 2a where the injector 7 is attached (the downstream side of the intake flow), and the amount of fuel injected from the injector 7 is the largest. A region is preferred. Further, the wall surface temperature of the intake port 2a may be estimated from the continuous operation time of the engine, the coolant temperature, or the like.

  The present invention is applied to an engine control capable of preventing engine stall due to execution of engine stall avoidance operating angle control with respect to a diesel engine capable of executing engine stall avoidance operating angle control for reducing the valve operating angle of the intake valve. Is possible.

2a Intake port 4 Piston 6 Combustion chamber 11 Intake valve 30 Variable valve mechanism 100 Electronic control unit 111 Crank angle sensor

Claims (7)

Equipped with a variable valve mechanism that allows the operating angle of the intake valve to be changed, when the predetermined engine stall avoidance operating angle control execution condition is satisfied, the engine stall avoiding operation that increases the engine speed by changing the operating angle of the intake valve In a control device for an internal combustion engine capable of executing angle control,
Wall surface temperature recognition means for detecting or estimating the wall surface temperature of the intake port;
When the wall surface temperature of the intake port detected or estimated by the wall surface temperature recognition means is lower than a predetermined temperature, the execution of the engine stall avoidance operation angle control is prohibited even if the engine stall avoidance operation angle control execution condition is satisfied. A control device for an internal combustion engine, comprising: an engine stall avoidance operating angle control prohibiting unit. The control apparatus for an internal combustion engine according to claim 1,
The engine control apparatus for an internal combustion engine, wherein the engine stall avoidance operating angle control execution condition is satisfied when the engine speed is reduced to a predetermined engine stall predicted speed. The control apparatus for an internal combustion engine according to claim 1,
The control device for an internal combustion engine, wherein the engine stall avoidance operating angle control execution condition is established when the detected or estimated air-fuel ratio in the cylinder rises to a predetermined engine stall predicted air-fuel ratio. The control device for an internal combustion engine according to claim 1, 2, or 3,
The control device for an internal combustion engine, wherein the engine stall avoidance operating angle control is to reduce the operating angle of the intake valve by a variable valve mechanism. In the control device for an internal combustion engine according to any one of claims 1 to 4,
The control apparatus for an internal combustion engine, wherein the wall surface temperature recognition means is configured to estimate that the wall surface temperature of the intake port is higher as the integrated value of the intake air amount is larger. In the control device for an internal combustion engine according to any one of claims 1 to 4,
The wall surface temperature recognizing means is configured to estimate that the wall surface temperature of the intake port is higher as the integrated value of the intake air amount calculated based on the engine speed and the engine load factor is larger. Engine control device. The control apparatus for an internal combustion engine according to any one of claims 1 to 6,
The engine stall avoidance operation angle control is started when the wall surface temperature of the intake port detected or estimated by the wall surface temperature recognition means reaches a predetermined temperature or more in a state where the engine stall avoidance operation angle control execution condition is satisfied. A control apparatus for an internal combustion engine, characterized by being configured as described above.

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