JP2009019521A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of properly restraining overheating of a catalyst, in the internal combustion engine likely to put a valve overlap quantity in a negative state. <P>SOLUTION: This control device 80 executes driving control of an exhaust side variable valve train 60b of changing the valve timing of an exhaust valve 18, knocking control for correcting the ignition time for delaying when detecting knocking and overheating restraining control for restraining the overheating of the catalyst 70. When executing the overheating restraining control, the estimate temperature of the catalyst 70 is calculated based on an engine operation state, and when determining that the catalyst 70 is an overheating state based on its estimate temperature, a quantity increase correction of a fuel injection quantity is made as restraining processing for restraining the overheating of the catalyst 70. When calculating its estimate temperature, when the valve overlap quantity becomes negative and when the valve overlap quantity does not become negative, its estimate temperature is calculated so that the estimate temperature becomes different. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that suppresses overheating of a catalyst provided in an exhaust passage.

  A catalyst for purifying exhaust gas is provided in the exhaust passage of the internal combustion engine. For example, when the engine operating state is a high rotation high load state or the like, the catalyst is overheated by the high-temperature exhaust gas, and in some cases, the purification function may be deteriorated.

Therefore, for example, in the device described in Patent Document 1, the temperature of the catalyst is estimated based on the intake air amount and the engine rotational speed, and when the estimated temperature is excessively high, the fuel injection amount is increased and corrected. Suppression control is performed such that the temperature of the exhaust gas is reduced by increasing the heat of vaporization to suppress overheating of the catalyst.
JP 2002-47971 A

  By the way, in an internal combustion engine having a variable valve mechanism that varies the valve timing of an intake valve or an exhaust valve for the purpose of improving engine output, exhaust emission, etc., the valve overlap amount between the intake valve and the exhaust valve is limited by the engine. It is changed according to the driving state.

  Such valve overlap amount will be described with reference to FIG. Here, the valve overlap amount is defined as the crank angle from the opening timing of the intake valve to the closing timing of the exhaust valve, more precisely, from the crank angle when the exhaust valve is closed to the crank angle when the intake valve is opened. It is defined as the value obtained by subtracting the angle.

  For example, in the state shown in FIG. 12A, the exhaust valve is closed after the intake valve is opened, and both valves are opened between the opening timing of the intake valve and the closing timing of the exhaust valve. A valved valve overlap period exists. According to the above definition, the valve overlap amount at this time is a positive value.

In the state shown in FIG. 12B, the intake valve is opened and the exhaust valve is closed simultaneously, and the value of the valve overlap amount at this time is “0”.
On the other hand, in the state shown in FIG. 12C, the intake valve is opened after the exhaust valve is closed, and both valves are closed between the exhaust valve closing timing and the intake valve opening timing. Period exists. According to the above definition, the valve overlap amount at this time is a negative value.

  In a general internal combustion engine, the valve timing is hardly set so that the valve overlap amount becomes a negative value. However, in an internal combustion engine that performs early closing of the exhaust valve as described below, the valve overlap amount may be in a negative state. That is, early closing of the exhaust valve sets the exhaust valve closing timing to a timing that is more advanced than the exhaust top dead center, thereby recompressing the burned gas remaining in the cylinder and increasing its temperature. This is done to blow back to the intake port. The burned gas is blown back to promote atomization and atomization of the fuel adhering to the intake port wall surface.

  On the other hand, when the valve overlap amount is set to a negative state, the burnt gas is recompressed and the temperature thereof is increased. Therefore, the compression end temperature is likely to be increased particularly at the time of high rotation and high load. As the compression end temperature becomes higher in this way, knocking is likely to occur. Therefore, it is desirable to correct the ignition timing to the retard side when the valve overlap amount is negative as compared to when the valve overlap amount is not negative.

  By the way, when the ignition timing is corrected to the retard side as described above, the exhaust temperature tends to be higher than the case where such retard correction is not performed. However, the conventional apparatus does not take into account the increase in the exhaust gas temperature by correcting the ignition timing retarded when the valve overlap amount is negative. For this reason, in an internal combustion engine in which the valve overlap amount may be negative, the catalyst temperature cannot be accurately estimated by the above-described conventional device, and it may not be possible to appropriately suppress overheating of the catalyst. There is room for further improvement in this respect.

  The present invention has been made in view of such circumstances, and an object thereof is an internal combustion engine capable of appropriately suppressing overheating of a catalyst in an internal combustion engine in which a valve overlap amount may be set to a negative state. It is to provide a control device.

The means for achieving the above object and the effects thereof will be described below.
The invention according to claim 1 is an internal combustion engine comprising an exhaust side variable valve mechanism for changing a valve timing of the exhaust valve and a catalyst provided in the exhaust passage, and driving the exhaust side variable valve mechanism. In a control apparatus for an internal combustion engine, comprising: a control means for controlling the engine; and a suppression means for executing a suppression process for suppressing overheating of the catalyst when it is determined that the catalyst is in an overheated state based on the estimated temperature of the catalyst. When the overlap amount is negative, the estimated temperature is calculated based on the ignition timing correction means for correcting the ignition timing to the retard side and the engine operating state as compared to when the overlap amount is not negative. In the calculation, there is provided an estimation means for calculating the estimated temperature so that the estimated temperature differs between when the valve overlap amount is negative and when it is not negative. Rukoto is referred to as the gist thereof.

  According to this configuration, when the valve overlap amount is in a negative state, the valve overlap amount is not in a negative state in order to suppress the occurrence of knocking due to the rise in the compression end temperature. In comparison, the ignition timing is changed to the retard side.

  On the other hand, when the ignition timing is changed to the retard side as described above, the exhaust gas temperature rises. Therefore, when the valve overlap amount is made negative, compared to when the negative state is not made, that is, The catalyst temperature tends to be higher than when the valve overlap amount is positive or “0”. Therefore, in this configuration, the estimated temperature is calculated so that the estimated temperature of the catalyst differs between when the valve overlap amount is negative and when it is not negative. As a result, the estimated temperature is calculated according to the state of the valve overlap amount, and the accuracy of the estimated temperature calculated when the valve overlap amount is in a negative state is improved. Become. Therefore, the accuracy of the catalyst overheat determination is also improved, and the suppression process for suppressing overheating of the catalyst is appropriately performed. Therefore, in an internal combustion engine in which the valve overlap amount may be negative, overheating of the catalyst can be appropriately suppressed.

  When calculating the estimated temperature of the catalyst, as described in the second aspect of the present invention, the estimating means is more effective when the valve overlap amount is negative than when it is not negative. By adopting a configuration in which the estimated temperature is calculated so that the estimated temperature becomes high, the accuracy of the estimated temperature can be appropriately increased.

  When the estimated temperature is calculated based on the engine operating state, the estimating means calculates the estimated temperature based on the engine rotational speed and the engine load factor. It is possible to adopt a configuration such as. Incidentally, when the same configuration is adopted, the estimated temperature can be appropriately calculated by calculating the estimated temperature so that the estimated temperature becomes higher as the engine speed and the load factor of the engine are higher.

  According to a fourth aspect of the present invention, in the control device for an internal combustion engine according to any one of the first to third aspects, the suppression means uses a fuel injection amount injected from a fuel injection valve as the suppression process. When the valve overlap amount is negative, the fuel injection amount increases when the valve overlap amount is negative compared to when the valve overlap amount is negative. The main point is to make it larger.

  According to this configuration, when it is determined that the catalyst is in an overheated state, the fuel injection amount is corrected to increase based on the engine operating state. The exhaust temperature is reduced by this increase correction, and overheating of the catalyst can be suppressed by the reduction of the exhaust temperature. Here, according to this configuration, when the valve overlap amount is negative and the exhaust temperature tends to be higher, the fuel injection amount is smaller than when the valve overlap amount is not negative. Increase value is increased. Therefore, overheating of the catalyst when the valve overlap amount is negative can be appropriately suppressed. In this configuration, the increase value can be appropriately set by setting the increase value so that the engine rotation speed and the load factor of the engine are higher.

  According to a fifth aspect of the present invention, in the control device for an internal combustion engine according to any one of the first to third aspects of the present invention, as the suppression process, the suppression means determines a fuel injection amount injected from a fuel injection valve. The gist of the present invention is to correct it with an increase value set based on the estimated temperature.

  According to this configuration, when it is determined that the catalyst is in an overheated state, the exhaust temperature is decreased by correcting the fuel injection amount to be increased based on the estimated temperature of the catalyst, and the catalyst is overheated due to the decrease in the exhaust temperature. Can be suppressed. Here, as described above, the estimated temperature of the catalyst is calculated by the estimating means, so that the accuracy of the estimated temperature when the valve overlap amount is negative is improved. Accordingly, an increase value of the fuel injection amount set based on the estimated temperature of the catalyst is also set appropriately, so that overheating of the catalyst when the valve overlap amount is negative can be appropriately suppressed. become. In this configuration, the increase value can be set appropriately by setting the increase value so that the estimated temperature of the catalyst is higher.

  According to a sixth aspect of the present invention, in the control apparatus for an internal combustion engine according to any one of the first to third aspects, the internal combustion engine further includes an intake side variable valve mechanism that changes a valve timing of the intake valve. And when the catalyst is determined to be in an overheated state based on the estimated temperature calculated when the valve overlap amount is negative, the suppression means includes the intake valve as the suppression process. The gist of the invention is to drive the intake side variable valve mechanism so that the valve opening timing is more advanced than the valve closing timing of the exhaust valve.

  According to this configuration, when it is determined that the catalyst is in an overheated state based on the estimated temperature calculated when the valve overlap amount is negative, the opening timing of the intake valve is set to close the exhaust valve. By changing the timing so that the timing is more advanced than the timing, the state where the valve overlap amount is negative is eliminated. As a result, the compression end temperature decreases, knocking is less likely to occur, and the ignition timing is easily changed to the advance side. And since the exhaust gas temperature is lowered when the ignition timing is changed to the advance side in this way, overheating of the catalyst can be appropriately suppressed even with this configuration.

  According to a seventh aspect of the present invention, in the control apparatus for an internal combustion engine according to any one of the first to sixth aspects, the valve overlap amount when the valve timing of the exhaust valve is set to a most advanced position. The exhaust valve closing timing is set so as to be negative, and at the time of at least one of the engine start and the idle operation and at the time of abnormal control of the exhaust side variable valve mechanism The gist of the invention is that the exhaust-side variable valve mechanism is driven so that the valve timing of the exhaust valve becomes the most advanced position.

  According to this configuration, the burned gas remaining in the cylinder is recompressed and the temperature thereof is increased by setting the valve overlap amount to a negative state when the engine is started or idling. Blows back into the intake port. By blowing back the burned gas, the effect of promoting atomization and atomization of the fuel adhering to the wall surface of the intake port can be obtained at the time of low rotation and low load such as when the engine is started or during idling.

  On the other hand, when the control of the exhaust side variable valve mechanism is abnormal (for example, when the actual valve timing of the exhaust valve cannot be controlled to its target value), the valve timing of the exhaust valve becomes unstable. Cheap. Therefore, in this configuration, when the above control abnormality occurs, the exhaust side variable valve mechanism is driven so that the valve timing of the exhaust valve becomes the most advanced angle position. The destabilization will be suppressed. Here, when the control is abnormal, the valve overlap amount is set to a negative state. However, the control abnormality may occur regardless of the state of the engine speed or the engine load. For this reason, for example, when the above control abnormality occurs at high rotation and high load and the valve overlap amount is set to a negative state, the compression end temperature rises as described above, and the catalyst may be overheated. In this regard, according to the configuration, in the internal combustion engine in which the valve overlap amount may be in a negative state by providing the configuration according to any one of the first to fifth aspects, the catalyst is overheated. Can be suppressed appropriately.

  When the ignition timing is corrected to the retarded side by the ignition timing correcting means, for example, when the valve overlap amount is negative, the ignition timing is changed to the retarded side by a preset correction amount. It is also possible to adopt a configuration such as, but in addition to this, as in the invention according to claim 8, when the knocking is detected, the configuration is executed by a knocking control that retards the ignition timing. Can also be adopted. In this case, the ignition timing retardation correction amount when the valve overlap amount is in a negative state can be appropriately set in accordance with the occurrence of knocking.

  Note that the above “when the valve overlap amount is negative” means that the exhaust valve is closed when the exhaust valve is closed at a timing more advanced than the exhaust top dead center. The value obtained by subtracting the crank angle at the time of opening of the intake valve from the crank angle at the time is negative.

(First embodiment)
Hereinafter, a first embodiment of a control device for an internal combustion engine according to the present invention will be described in detail with reference to FIGS.

FIG. 1 shows a schematic configuration of an engine 1 to which the control device for an internal combustion engine according to the present embodiment is applied.
The cylinder block 2 of the engine 1 includes a plurality of cylinders 3 (only one is shown in FIG. 1). A piston 4 provided in the cylinder 3 is connected to a crankshaft 5 via a connecting rod 6. The connecting rod 6 converts the reciprocating motion of the piston 4 into the rotational motion of the crankshaft 5.

  A cylinder head 7 is attached to the upper part of the cylinder block 2. In the cylinder 3, a combustion chamber 8 is formed between the upper end of the piston 4 and the cylinder head 7.

  A spark plug 11 is provided in the combustion chamber 8. An intake passage 14 and an exhaust passage 15 are connected to an intake port 12 and an exhaust port 13 provided corresponding to the combustion chamber 8, respectively. Further, fuel is injected from an injector 16 provided in the intake port 12 corresponding to the combustion chamber 8.

  An intake valve 17 and an exhaust valve 18 provided corresponding to the combustion chamber 8 open and close the intake port 12 and the exhaust port 13, respectively. The intake valve 17 and the exhaust valve 18 open and close as the cams provided on the camshafts 31 and 32 rotate in accordance with the rotation of the intake camshaft 31 and the exhaust camshaft 32, respectively. The timing pulleys 33 and 34 provided at the tips of the camshafts 31 and 32 are drivingly connected to the crankshaft 5 via a timing belt 35. When the crankshaft 5 rotates twice, the timing pulleys 33 and 34 are connected. Is designed to rotate once. During operation of the engine 1, the rotational force of the crankshaft 5 is transmitted to the intake side camshaft 31 and the exhaust side camshaft 32 via the timing belt 35 and the timing pulleys 33 and 34. Thus, the intake valve 17 and the exhaust valve 18 are driven to open and close at a predetermined timing in synchronization with the rotation of the crankshaft 5, that is, corresponding to the reciprocating movement of each piston 4.

  The timing pulley 33 provided on the intake side camshaft 31 is provided with an intake side variable valve mechanism (hereinafter referred to as IN-VVT mechanism) 60a. By driving the IN-VVT mechanism 60a, the relative rotational phase of the intake camshaft 31 with respect to the crankshaft 5 is changed, and the valve timing of the intake valve 17 is changed. The timing pulley 34 provided on the exhaust side camshaft 32 is provided with an exhaust side variable valve mechanism (hereinafter referred to as EX-VVT mechanism) 60b. By driving the EX-VVT mechanism 60b, the relative rotational phase of the exhaust camshaft 32 with respect to the crankshaft 5 is changed, and the valve timing of the exhaust valve 18 is changed.

  A surge tank 51 for suppressing intake air pulsation is provided in a part of the intake passage 14. On the upstream side of the surge tank 51, a throttle valve 53 whose opening degree is changed based on the operation of the accelerator pedal 52 is provided. The amount of air taken into the combustion chamber 8 is adjusted by changing the opening of the throttle valve 53.

  A high voltage output from the igniter 46 is supplied to the spark plug 11. The ignition timing of the spark plug 11 is determined by the output timing of the high voltage from the igniter 46. The spark plug 11 ignites an air-fuel mixture composed of intake air from the intake passage 14 and fuel injected from the injector 16, and the air-fuel mixture is combusted in the combustion chamber 8. Engine output occurs. Combustion gas resulting from the combustion of the air-fuel mixture is discharged to the exhaust passage 15. A catalyst 70 for purifying exhaust (combustion gas) from the combustion chamber 8 is provided in the middle of the exhaust passage 15.

  The engine 1 is provided with various sensors. For example, a crank angle sensor 41 is provided in the vicinity of the crankshaft 5. The crank angle sensor 41 detects the rotational phase (crank angle) of the crankshaft 5 and detects the engine rotational speed NE based on the detection result. Further, a cam angle sensor 42a is provided in the vicinity of the intake side camshaft 31, and the rotation phase of the intake side camshaft 31 is detected based on the output signals of the cam angle sensor 42a and the crank angle sensor 41. The valve timing of the intake valve 17 is detected. Similarly, a cam angle sensor 42b is provided in the vicinity of the exhaust side camshaft 32, and the rotational phase of the exhaust side camshaft 32 is detected based on the output signals of the cam angle sensor 42b and the crank angle sensor 41. As a result, the valve timing of the exhaust valve 18 is detected. A throttle opening sensor 54 for detecting the opening is attached to the throttle valve 53. Further, on the upstream side of the throttle valve 53, an air flow meter 56 that provides an output corresponding to the intake air amount GA taken into the engine 1 is provided. Further, a knock sensor 57 for detecting knocking generated in the combustion chamber 8 is also provided on the outer wall of the cylinder block 2.

  The control device 80 performs various controls such as the ignition timing control of the engine 1, the fuel injection amount control, or the valve timing control of the intake valve 17 and the exhaust valve 18 based on the phase control of the IN-VVT mechanism and the EX-VVT mechanism. Is called. The control device 80 is configured around a microcomputer including a central processing control device (CPU). For example, the control device 80 is provided with a read-only memory (ROM) in which various programs, maps, and the like are stored in advance, and a random access memory (RAM) in which CPU calculation results and the like are temporarily stored. The control device 80 is also provided with a backup RAM, an input interface, an output interface, and the like for storing calculation results and prestored data after the engine is stopped. And the operation state of the engine 1 is detected by the output signal from the said various sensors being input through an input interface.

  On the other hand, the output interface is connected to the drive actuators and the like of the injector 16, the igniter 46, the IN-VVT mechanism 60a, and the EX-VVT mechanism 60b through corresponding drive circuits. The control device 80, based on the signals from the various sensors and the like, in accordance with the control program and initial data stored in the ROM, the injector 16, igniter 46, IN-VVT mechanism 60a, EX-VVT mechanism 60b, etc. To control.

  When the occurrence of knocking is detected based on the signal from knock sensor 57, control device 80 determines engine load factor KL (the ratio of current intake air amount GA to intake air amount GA at full load) and engine speed NE. A so-called knocking control for correcting the retardation of the basic ignition timing set based on the above is performed as one of the ignition timing controls. In this knocking control, the basic ignition timing is gradually corrected to the advance side when knocking is not detected. On the other hand, when knocking is detected, the basic ignition timing is corrected to the retard side by a preset correction amount until the knocking is not detected.

  Further, in order to prevent the purification function from deteriorating due to thermal deterioration of the catalyst 70, the control device 80 increases the fuel injection amount injected from the injector 16 when the temperature of the catalyst 70 is excessively high. Overheat suppression control is performed in which the temperature of the exhaust gas is reduced by suppressing the overheating of the catalyst 70 by increasing the heat of vaporization of the fuel.

  The control device 80 basically performs valve timing control of the intake valve 17 and the exhaust valve 18 in the following manner. That is, the control device 80 calculates the target overlap amount OLT and the target intake valve timing InVTT, which are target values of the valve overlap amount and the valve timing of the intake valve 17, based on the engine rotational speed NE, the engine load factor KL, and the like. Calculate each. Then, the control device 80 feedback-controls the operation of the intake side variable valve mechanism 60a so that the actual valve timing of the intake valve 17 (actual intake valve timing InVTR) finally becomes the target intake valve timing InVTT. On the other hand, the control device 80 feedback-controls the operation of the exhaust side variable valve mechanism 60b so that the actual valve overlap amount (actual overlap amount OLR) finally becomes the target overlap amount OLT. As described above, the valve timings and valve overlap amounts of the intake valve 17 and the exhaust valve 18 are adjusted to optimum values according to the engine operating state.

  In the present embodiment, the valve timing of the intake valve 17 is set to the valve timing advance amount (crank angle [°]) with the most retarded position of the valve timing change range of the intake valve 17 as the reference “0 °”. ). The valve overlap amount is expressed as a value obtained by subtracting the crank angle when the intake valve 17 is opened from the crank angle when the exhaust valve 18 is closed. Accordingly, the exhaust valve 18 is closed before the intake valve 17 is opened, and there is a period in which both valves are closed between the valve closing timing of the exhaust valve 18 and the valve opening timing of the intake valve 17. Sometimes the valve overlap amount is negative.

  By the way, in the control device of the present embodiment, the exhaust valve 18 is quickly closed when the engine 1 is started or during idling. The valve timing of the intake / exhaust valve at this time is set as shown in FIG. That is, the valve timing (actual intake valve timing InVTR) of the intake valve 17 at this time is set to “0 °” that is the most retarded position. Further, the valve overlap amount (actual overlap amount OLR) at this time is set to an initial value OLinit (<0 °) which is the minimum value of the variable range. As a result, the valve timing of the exhaust valve 18 is set to the most advanced angle position at which the valve closing timing of the exhaust valve 18 is advanced (for example, about 20 °) from the exhaust top dead center. In this way, the exhaust valve 18 is closed on the advance side from the exhaust top dead center, so that the burnt gas remaining in the cylinder 3 is recompressed and the temperature thereof is increased in the intake air state. Blowed back to port 12. And the atomization and atomization of the fuel adhering to the wall surface etc. of the intake port 12 are accelerated | stimulated by the blow-back of the burnt gas. In the engine 1, the valve timing of each valve is set so that the valve overlap amount is “0” or positive except at the time of starting and idling.

  On the other hand, when the control of the exhaust side variable valve mechanism 60b is abnormal (for example, when the valve timing of the exhaust valve 18 cannot be controlled to a target value corresponding to the target valve overlap amount OLT), the exhaust valve The valve timing of 18 cannot be appropriately controlled, and the valve timing tends to be unstable.

  Therefore, when the control abnormality occurs, the control device 80 drives the intake side variable valve mechanism 60a so that the valve timing of the intake valve 17 is fixed at the most retarded position, and the valve timing of the exhaust valve 18. The exhaust side variable valve mechanism 60b is driven so that is fixed at the most advanced position. As described above, the valve timing of the exhaust valve 18 is fixed at the most advanced position, so that the valve timing of the exhaust valve 18 is prevented from becoming unstable.

  By the way, in a state where the valve overlap amount is negative, the burnt gas is recompressed and its temperature becomes high. Therefore, especially at the time of high rotation and high load, the compression end temperature tends to be high and knocking is likely to occur. Therefore, when the valve overlap amount is negative, ignition timing retardation correction by the knocking control is more easily performed than when the valve overlap amount is not negative. As a result, when the valve overlap amount is negative, the exhaust temperature tends to be higher than when the valve overlap amount is not negative.

  When the control is abnormal, the valve timing of the intake valve 17 is fixed at the most retarded position, and the valve timing of the exhaust valve 18 is fixed at the most advanced position, so that the valve overlap amount is negative. Put into a state. Such a control abnormality may occur regardless of the state of the engine rotational speed NE or the engine load factor KL. Therefore, for example, the control abnormality occurs at a high rotation and a high load, and the valve overlap amount is negative. In this case, the exhaust gas temperature becomes higher compared to when the valve overlap amount is positive or “0”. Therefore, in the present embodiment, by performing the overheat suppression control in consideration of such a difference in exhaust temperature, in the engine 1 in which the valve overlap amount may be in a negative state, the catalyst 70 is appropriately overheated. I try to suppress it.

FIG. 3 shows a processing procedure for the overheat suppression control. This process is repeatedly executed at predetermined intervals by the control device 80.
When this process is started, it is first determined whether or not the exhaust-side fail flag Fex is “ON” (S100). The exhaust-side fail flag Fex is changed from “OFF” to “ON” when the control abnormality of the exhaust-side variable valve mechanism 60b as described above occurs.

  When the exhaust side fail flag Fex is set to “OFF” and the exhaust side variable valve mechanism 60b is normally controlled (S100: NO), the engine speed NE and the engine load factor KL are set. Based on the above, the estimated temperature T of the catalyst 70 is calculated with reference to the first temperature map Tmap1 which is a two-dimensional map stored in the ROM of the control device 80 (S110). Here, the higher the engine speed NE or the higher the engine load factor KL, the higher the exhaust temperature tends to be, and the higher the temperature of the catalyst 70 becomes. Therefore, the first temperature map Tmap1 is set so that the estimated temperature T increases as the engine speed NE increases as shown in FIG. 4, and the engine load factor KL is set as shown in FIG. The higher the temperature, the higher the estimated temperature T.

  Next, it is determined whether or not the estimated temperature T calculated in step S110 is equal to or higher than the overheat determination value α (S120). As the overheat determination value α, a temperature at which the catalyst 70 may be thermally deteriorated is appropriately set. When the estimated temperature T is less than the overheat determination value α (S120: NO), it is determined that the catalyst 70 is not in an overheated state, and the present process is temporarily terminated.

  On the other hand, if the estimated temperature T is equal to or higher than the overheat determination value α (S120: YES), it is determined that the catalyst 70 is in an overheated state, and then the control is performed based on the engine speed NE and the engine load factor KL. The fuel injection amount increase value D is calculated with reference to a first increase map Dmap1 which is a two-dimensional map stored in the ROM of the device 80 (S130). Here, as described above, the higher the engine speed NE or the higher the engine load factor KL, the higher the exhaust temperature tends to be, and the higher the temperature of the catalyst 70. It is necessary to set the fuel injection amount increase value D in accordance with the tendency. Therefore, the first increase map Dmap1 is set so that the increase value D increases as the engine speed NE increases as shown in FIG. 6, and the engine load factor KL is set as shown in FIG. The increase value D is set to increase as the value increases. When the increase value D is calculated in this way, the present process is temporarily terminated. Then, the basic fuel injection amount set based on the engine operating state is increased and corrected by the increase value D, so that overheating of the catalyst 70 is suppressed.

  In step S100, when the exhaust-side fail flag Fex is “ON” (S100: YES), it is determined that the current valve overlap amount is negative.

  Based on the engine rotational speed NE and the engine load factor KL, the estimated temperature T of the catalyst 70 is calculated with reference to the second temperature map Tmap2, which is a two-dimensional map stored in the ROM of the control device 80 (S140). . The second temperature map Tmap2 is also set so that the estimated temperature T increases as the engine rotational speed NE increases as shown in FIG. 4, and the engine load increases as shown in FIG. It is set so that the estimated temperature T increases as the rate KL increases. Further, when a control abnormality has occurred in the exhaust side variable valve mechanism 60b and the valve overlap amount is in a negative state, the valve overlap amount is not in a negative state, that is, the valve overlap amount. The exhaust temperature tends to be higher than when the amount is positive or “0”. Therefore, in the second temperature map Tmap2, as shown in FIGS. 4 and 5, the estimated temperature T set at the same engine speed NE and the same as the first temperature map Tmap1 are compared. The estimated temperature T set at the engine load factor KL is set to a higher value.

  As described above, even when the engine speed NE and the engine load factor KL are the same, when the valve overlap amount is negative, the estimated temperature is lower than when the valve overlap amount is not negative. T is calculated to be higher. In other words, when the valve overlap amount is negative and when the valve overlap amount is not negative, even if the engine speed NE and the engine load factor KL are the same, the estimated temperature T The estimated temperature T is calculated so as to be different. Thus, the estimated temperature T is calculated according to the state of the valve overlap amount, and the accuracy of the estimated temperature T when the valve overlap amount is negative is improved.

  Next, it is determined whether or not the estimated temperature T calculated in step S140 is equal to or higher than the overheat determination value α (S150). Here, since the accuracy of the estimated temperature T is increased by the calculation of the estimated temperature T based on the second temperature map Tmap2, the accuracy of the overheat determination of the catalyst 70 by the comparison determination between the estimated temperature T and the overheat determination value α is performed. That is, the determination accuracy of whether or not the catalyst 70 is in an overheated state is naturally increased. When the estimated temperature T is less than the overheat determination value α (S150: NO), it is determined that the catalyst 70 is not in an overheated state, and the present process is temporarily terminated.

  On the other hand, when the estimated temperature T is equal to or higher than the overheat determination value α (S150: YES), it is determined that the catalyst 70 is in an overheated state, and then, based on the engine speed NE and the engine load factor KL, The fuel injection amount increase value D is calculated with reference to the second increase map Dmap2 which is a two-dimensional map stored in the ROM of the control device 80 (S160). The second increase map Dmap2 is also set so that the increase value D increases as the engine speed NE increases as shown in FIG. 6, and the engine load increases as shown in FIG. The increase value D is set to increase as the rate KL increases. Further, as described above, when the control abnormality has occurred in the exhaust side variable valve mechanism 60b and the valve overlap amount is in a negative state, it is compared with when the valve overlap amount is not negative. As a result, the exhaust temperature tends to increase. Therefore, in the second increase map Dmap2, as shown in FIGS. 6 and 7, the increase value D set at the same engine speed NE or the same value as the first increase map Dmap1 is compared. The increase value D set in the engine load factor KL is set to a larger value. Thus, even when the engine speed NE and the engine load factor KL are the same, when the valve overlap amount is negative, the increase value is larger than when the valve overlap amount is not negative. It is calculated so that D becomes larger.

  When the increase value D is calculated in this way, this process is temporarily terminated. Then, the basic fuel injection amount set based on the engine operating state is corrected to increase by the amount of increase D calculated in step S160. In the increase correction at this time, the valve overlap amount is negative, and the increase value D is made larger than when the valve overlap amount is not negative. Therefore, overheating of the catalyst 70 when the valve overlap amount is negative is appropriately suppressed.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The estimated temperature T of the catalyst 70 is calculated based on the engine operating state, and when it is determined that the catalyst 70 is overheated based on the estimated temperature T, a suppression process for suppressing overheating of the catalyst 70 is executed. ing. The estimated temperature T is calculated so that the calculated estimated temperature T differs between when the valve overlap amount is negative and when the valve overlap amount is not negative. Yes. More specifically, when the valve overlap amount is negative, the calculated estimated temperature T is higher than when the valve overlap amount is not negative. As a result, the estimated temperature T is calculated according to the state of the valve overlap amount, and the accuracy of the estimated temperature T calculated when the valve overlap amount is in a negative state is improved. It becomes like this. Therefore, the accuracy of the overheating determination of the catalyst 70 is improved, and the above suppression process for suppressing the overheating of the catalyst 70 is appropriately performed. Therefore, overheating of the catalyst 70 can be appropriately suppressed in the engine 1 in which the valve overlap amount may be negative.

  (2) The estimated temperature T is calculated based on the engine speed NE and the engine load factor KL. More specifically, the estimated temperature T is calculated such that the estimated temperature T increases as the engine speed NE and the engine load factor KL are higher, and the estimated temperature T can be calculated appropriately.

  (3) As the suppression process, the fuel injection amount injected from the injector 16 is corrected with the increase value D set based on the engine operating state. When the valve overlap amount is negative and the exhaust temperature tends to be high, the increase value D is made larger than when the valve overlap amount is not negative. Yes. Therefore, overheating of the catalyst 70 when the valve overlap amount is negative can be appropriately suppressed.

  (4) The closing timing of the exhaust valve 18 is set so that the valve overlap amount becomes negative when the valve timing of the exhaust valve 18 is set to the most advanced angle position. During idle operation, the exhaust side variable valve mechanism 60b is driven so that the valve timing of the exhaust valve 18 is at the most advanced position. As a result, when the engine 1 is started or idling, the valve overlap amount is set to a negative state. At such a low rotation and low load, the fuel adhering to the wall surface of the intake port 12 is atomized or atomized. Can be promoted.

  Further, the exhaust side variable valve mechanism 60b is driven so that the valve timing of the exhaust valve 18 reaches the most advanced position even when the exhaust side variable valve mechanism 60b is abnormally controlled. Thereby, instability of the valve timing of the exhaust valve 18 at the time of such control abnormality can be suppressed. Here, when the control is abnormal, the valve overlap amount is set to a negative state. However, the control abnormality may occur regardless of the state of the engine speed NE or the engine load factor KL. . For this reason, for example, when the above control abnormality occurs at high rotation and high load and the valve overlap amount is made negative, the compression end temperature rises as described above and the catalyst 70 may be overheated. . In this regard, according to the present embodiment, overheating of the catalyst 70 can be appropriately suppressed in the engine 1 in which the valve overlap amount can be in a negative state.

(5) Compared to when the valve overlap amount is not in a negative state when the valve overlap amount is in a negative state, in order to suppress the occurrence of knocking due to an increase in compression end temperature. The ignition timing is corrected to the retard side. The ignition timing is corrected to the retard side through execution of the knocking control. Therefore, the retard correction amount of the ignition timing when the valve overlap amount is in a negative state can be appropriately set in accordance with the occurrence of knocking.
(Second Embodiment)
Next, a second embodiment of the internal combustion engine control device according to the present invention will be described with reference to FIGS.

  In the overheat suppression control of the first embodiment, the fuel injection amount increase value D is set based on the engine speed NE and the engine load factor KL. On the other hand, in the overheat suppression control of the present embodiment, the increase value D is set based on the estimated temperature T of the catalyst 70 described above. Except for this point, basically the same as in the first embodiment. It is. Therefore, hereinafter, the overheat suppression control performed in the present embodiment will be described focusing on the difference.

In FIG. 8, the process sequence of the overheat suppression control in this embodiment is shown. This process is also repeatedly executed by the control device 80 at predetermined intervals.
When this process is started, first, it is determined whether or not the above-described exhaust-side fail flag Fex is set to “ON” (S100).

  When the exhaust side fail flag Fex is set to “OFF” and the exhaust side variable valve mechanism 60b is normally controlled (S100: NO), the engine speed NE and the engine load factor KL are set. Based on the above, the estimated temperature T of the catalyst 70 is calculated with reference to the first temperature map Tmap1 described above (S110).

On the other hand, when the exhaust-side fail flag Fex is “ON” (S100: YES), it is determined that the current valve overlap amount is negative.
Based on the engine rotational speed NE and the engine load factor KL, the estimated temperature T of the catalyst 70 is calculated with reference to the second temperature map Tmap2 described above (S140).

  When the estimated temperature T is calculated in step S110 or step S140, it is determined whether the estimated temperature T is equal to or higher than the above-described overheat determination value α (S120). When the estimated temperature T is less than the overheat determination value α (S120: NO), it is determined that the catalyst 70 is not in an overheated state, and the present process is temporarily terminated.

  On the other hand, when the estimated temperature T is equal to or higher than the overheat determination value α (S120: YES), it is determined that the catalyst 70 is in an overheated state, and then stored in the ROM of the control device 80 based on the estimated temperature T. The fuel injection amount increase value D is calculated with reference to the third increase map Dmap3 which is the one-dimensional map (S200). As shown in FIG. 9, the third increase map Dmap3 is set so that the increase value D increases as the estimated temperature T increases. When the increase value D is calculated in this way, the present process is temporarily terminated.

Then, the basic fuel injection amount set based on the engine operating state is corrected to increase by the increase value D.
In this way, when it is determined that the catalyst 70 is overheated, the fuel injection amount is corrected to be increased based on the estimated temperature T of the catalyst 70, so that the exhaust gas temperature is lowered. Can be suppressed. Here, when the valve overlap amount is negative, the estimated temperature T is calculated using the second temperature map Tmap2, and when the valve overlap amount is not negative, the first temperature map Tmap1 is used. Thus, the estimated temperature T is calculated. Thus, when the valve overlap amount is negative, the estimated temperature T of the catalyst 70 is calculated to be higher than when the valve overlap amount is not negative, and the valve overlap amount is calculated. The accuracy of the estimation of the temperature of the catalyst 70 when is negative is improved. Therefore, the increase value D set based on the estimated temperature T is also set appropriately. More specifically, even when the engine speed NE and the engine load factor KL are the same, when the valve overlap amount is negative, the valve overlap amount is not negative. The estimated temperature T of the catalyst 70 is calculated to be higher. Therefore, even if the engine speed NE and the engine load factor KL are the same, when the valve overlap amount is negative, the increase value D is smaller than when the valve overlap amount is not negative. The increase value D is set appropriately. As described above, also according to this embodiment, it is possible to appropriately suppress overheating of the catalyst 70 when the valve overlap amount is negative.
(Third embodiment)
Next, a third embodiment of the control device for an internal combustion engine according to the present invention will be described with reference to FIGS.

  In the first embodiment, the fuel injection amount increase correction is performed as a suppression process for suppressing overheating of the catalyst 70. On the other hand, in the present embodiment, as the suppression process when the valve overlap amount is not negative, the fuel injection amount increase correction is performed and the suppression process when the valve overlap amount is negative is performed. Is configured to change the valve timing of the intake valve 17 to the advance side, and is otherwise basically the same as that of the first embodiment. Therefore, hereinafter, the overheat suppression control performed in the present embodiment will be described focusing on the difference.

In FIG. 10, the process sequence of the overheat suppression control in this embodiment is shown. This process is also repeatedly executed by the control device 80 at predetermined intervals.
When this process is started, first, it is determined whether or not the above-described exhaust-side fail flag Fex is set to “ON” (S100).

  When the exhaust side fail flag Fex is set to “OFF” and the exhaust side variable valve mechanism 60b is normally controlled (S100: NO), the engine speed NE and the engine load factor KL are set. Based on the above, the estimated temperature T of the catalyst 70 is calculated with reference to the first temperature map Tmap1 described above (S110).

  Next, it is determined whether or not the estimated temperature T calculated in step S110 is equal to or higher than the above-described overheat determination value α (S120). When the estimated temperature T is less than the overheat determination value α (S120: NO), it is determined that the catalyst 70 is not in an overheated state, and the present process is temporarily terminated.

  On the other hand, when the estimated temperature T is equal to or higher than the overheat determination value α (S120: YES), fuel injection is performed with reference to the first increase map Dmap1 described above based on the engine speed NE and the engine load factor KL. The amount increase value D is calculated (S130), and the process is temporarily terminated. Then, the basic fuel injection amount set based on the engine operating state is increased and corrected by the increase value D, so that overheating of the catalyst 70 is suppressed.

  On the other hand, when the exhaust-side fail flag Fex is “ON” in step S100 (S100: YES), it is determined that the current valve overlap amount is negative.

Based on the engine rotational speed NE and the engine load factor KL, the estimated temperature T of the catalyst 70 is calculated with reference to the second temperature map Tmap2 described above (S140).
Next, it is determined whether or not the estimated temperature T calculated in step S140 is equal to or higher than the overheat determination value α described above (S150). When the estimated temperature T is less than the overheat determination value α (S150: NO), it is determined that the catalyst 70 is not in an overheated state, and the present process is temporarily terminated.

  On the other hand, when the estimated temperature T is equal to or higher than the overheat determination value α (S150: YES), it is determined that the catalyst 70 is in an overheated state, and the valve timing of the intake valve 17 is changed to the advance side. (S300). In this step S300, the target intake valve timing InVTT is set such that the opening timing of the intake valve 17 is advanced from the closing timing of the exhaust valve 18, and the actual intake valve timing InVTR is set to the target intake valve. The intake side variable valve mechanism 60a is driven so that the valve timing InVTT is reached. And this process is once complete | finished.

  Thus, according to the overheat suppression control, it is determined that the catalyst 70 is in an overheated state when the exhaust-side fail flag Fex is “ON”, that is, when the valve overlap amount is negative. In this case, as shown in FIG. 11, the opening timing of the intake valve 17 is changed to be a timing that is more advanced than the closing timing of the exhaust valve 18. This eliminates the state where the valve overlap amount is negative. By setting the valve overlap amount to a non-negative state in this way, the compression end temperature decreases, knocking is less likely to occur, and the ignition timing is easily changed to the advance side. As described above, when the ignition timing is changed to the advance side, the exhaust gas temperature is lowered. Therefore, also in the present embodiment, overheating of the catalyst 70 can be appropriately suppressed.

In addition, each said embodiment can also be implemented with the following forms which changed this suitably.
The engine load factor KL may be calculated based on other parameters such as the basic fuel injection amount, the operation amount of the accelerator pedal 52, or the opening degree of the throttle valve 53.

  Although the estimated temperature T of the catalyst 70 is calculated based on the engine speed NE and the engine load factor KL, the estimated temperature T may be calculated based on other parameters related to the engine operating state. Good. For example, an exhaust temperature sensor that detects the exhaust temperature may be provided in the exhaust passage 15, and the estimated temperature T of the catalyst 70 may be calculated based on the detected exhaust temperature.

The estimated temperature T and the increase value D are calculated using a map, but may be calculated using an appropriate relational expression.
-Whether or not the valve overlap amount is in a negative state is determined based on the value of the exhaust-side fail flag Fex, but such determination is performed based on the actual overlap amount OLR and the target overlap amount OLT. You may make it perform.

  In the third embodiment, when it is determined that the catalyst 70 is in an overheated state when the valve overlap amount is negative, the process of step S300 is performed, and the exhaust temperature is decreased by executing step S300. The fuel injection amount increase correction may be performed while taking the minute into consideration.

  Even in an internal combustion engine that does not include the intake side variable valve mechanism 60a and the valve timing of the intake valve 17 is fixed, the exhaust valve 18 is closed during the exhaust stroke, and then the intake valve 17 Is opened, a period in which both valves are closed occurs between the closing timing of the exhaust valve 18 and the opening timing of the intake valve 17, and the valve overlap amount becomes negative. Therefore, by applying the first and second embodiments also to the internal combustion engine in which the valve timing of the intake valve 17 is fixed as described above, it is possible to obtain the operational effects equivalent to the respective embodiments.

  In each of the above embodiments, correction of the ignition timing to the retard side when the valve overlap amount is negative is performed through execution of the knocking control. When the overlap amount is negative, the ignition timing may be corrected to the retard side compared to when the overlap amount is not negative. For example, when the valve overlap amount is negative, the ignition timing may be changed to the retard side by a preset correction amount. Also in this case, the occurrence of knocking due to the valve overlap amount being made negative and the compression end temperature rising can be suppressed.

  The engine 1 is an internal combustion engine in which the valve overlap amount is set to a negative state when the engine is started or idling, or when the exhaust side variable valve mechanism is abnormally controlled. The present invention can be similarly applied to an internal combustion engine in which the valve overlap amount is set to a negative state.

  The variable valve mechanism in each of the above embodiments is a mechanism that changes only the valve timing of the intake valve 17 and the exhaust valve 18. In addition, for example, the present invention can be similarly applied to an internal combustion engine including a variable valve mechanism that changes both the maximum lift amount and the valve timing of the intake valve 17 and the exhaust valve 18.

1 is a schematic configuration diagram of an internal combustion engine to which the control device for an internal combustion engine according to the first embodiment of the present invention is applied. The figure which shows the initial state about the valve timing of the intake valve and exhaust valve of the embodiment. The flowchart which shows the process sequence of the overheat suppression control in the embodiment. The graph which shows the correspondence of an engine speed and the estimated temperature of a catalyst. The graph which shows the correspondence of an engine load factor and the estimated temperature of a catalyst. The graph which shows the correspondence of an engine speed and the increase value of fuel injection quantity. The graph which shows the correspondence of an engine load factor and the increase value of fuel injection quantity. The flowchart which shows the process sequence of the overheat suppression control in 2nd Embodiment. The graph which shows the correspondence of the estimated temperature of a catalyst, and the increase value of fuel injection quantity. The flowchart which shows the process sequence of overheat suppression control in 3rd Embodiment. The figure which shows the example about the valve timing of an intake valve when the suppression process is performed in the embodiment. (A) is the valve timing when the valve overlap amount is positive, (b) is the valve timing when the valve overlap amount is "0", and (c) is the negative valve overlap amount. The figure which shows the valve timing at the time of.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder block, 3 ... Cylinder, 4 ... Piston, 5 ... Crankshaft, 6 ... Connecting rod, 7 ... Cylinder head, 8 ... Combustion chamber, 11 ... Spark plug, 12 ... Intake port, 13 ... Exhaust port , 14 ... intake passage, 15 ... exhaust passage, 16 ... injector, 17 ... intake valve, 18 ... exhaust valve, 31 ... intake side camshaft, 32 ... exhaust side camshaft, 33, 34 ... timing pulley, 35 ... timing belt 41 ... Crank angle sensor, 42a ... Cam angle sensor, 42b ... Cam angle sensor, 46 ... Igniter, 51 ... Surge tank, 52 ... Accelerator pedal, 53 ... Throttle valve, 54 ... Throttle opening sensor, 56 ... Air flow meter, 57 ... Knock sensor, 60a ... Intake side variable valve mechanism (IN-VVT mechanism), 60b ... Exhaust side Variable valve mechanism (EX-VVT mechanism), 70 ... catalyst 80 ... control unit.

Claims (8)

An internal combustion engine comprising an exhaust side variable valve mechanism for changing a valve timing of an exhaust valve and a catalyst provided in an exhaust passage, the control means for controlling driving of the exhaust side variable valve mechanism, and the catalyst An internal combustion engine control device comprising: suppression means for executing a suppression process for suppressing overheating of the catalyst when it is determined that the catalyst is in an overheated state based on the estimated temperature of
Ignition timing correction means for correcting the ignition timing to the retard side when the valve overlap amount is negative, compared to when the valve overlap amount is not negative;
The estimated temperature is calculated based on the engine operating state, and the estimated temperature is calculated so that the estimated temperature differs between when the valve overlap amount is negative and when it is not negative. An internal combustion engine control apparatus comprising: estimation means for calculating The estimation means calculates the estimated temperature so that the estimated temperature calculated based on the engine operating state is higher when the valve overlap amount is negative than when the valve overlap amount is not negative. The control device for an internal combustion engine according to claim 1. The control device for an internal combustion engine according to claim 1 or 2, wherein the estimation means calculates the estimated temperature based on an engine speed and a load factor of the engine. The suppression means corrects the fuel injection amount injected from the fuel injection valve with the increase value set based on the engine operating state as the suppression process,
The internal combustion engine according to any one of claims 1 to 3, wherein when the valve overlap amount is negative, the increase value of the fuel injection amount is increased compared to when the valve overlap amount is not negative. Control device. The internal combustion engine according to any one of claims 1 to 3, wherein the suppression unit corrects the fuel injection amount injected from the fuel injection valve with an increase value set based on the estimated temperature as the suppression process. Engine control device. The internal combustion engine further includes an intake side variable valve mechanism that changes a valve timing of the intake valve,
When it is determined that the catalyst is in an overheated state based on the estimated temperature calculated when the valve overlap amount is negative, the suppression means opens the intake valve as the suppression process. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the intake-side variable valve mechanism is driven so that the timing is a timing that is more advanced than the closing timing of the exhaust valve. The valve closing timing of the exhaust valve is set so that the valve overlap amount becomes negative when the valve timing of the exhaust valve is set to the most advanced position.
The exhaust valve is set so that the valve timing of the exhaust valve is at the most advanced position during at least one of engine start and idle operation and when the exhaust side variable valve mechanism is abnormally controlled. The control apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the side variable valve mechanism is driven. The correction to the retard side of the ignition timing by the ignition timing correction means is executed by knocking control that retards the ignition timing when knocking is detected. Control device for internal combustion engine.

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