JP2009236049A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine control device capable of reducing the possibility of heat damage occurrence while sufficiently ensuring the output of an engine. <P>SOLUTION: During high-load driving on a flatland, a VVT mechanism is feed-back controlled so as to make an actual valve overlapping amount become a predetermined valve overlapping amount V1, namely to make an actual intake opening time become a target intake opening time, and an actual exhaust closing time become a target exhaust closing time. On the other hand, during lower and middle-load driving, the VVT mechanism is feed-back controlled so as to make the actual valve overlapping amount become the predetermined valve overlapping amount V2, namely to make the actual intake opening time become the target intake opening time, and the actual exhaust closing time become the target exhaust closing time. The temperature of a catalyst is detected by a temperature sensor. On the basis of the detection result, the target intake opening time and the target exhaust closing time are properly corrected. Therefore, the output of the engine is sufficiently ensured, and the excessive temperature rise of the catalyst is suppressed, so that the heat damage occurrence of the catalyst can be suppressed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention controls the variable valve timing mechanism so as to obtain an optimal valve overlap amount in accordance with the temperature of the catalyst, thereby ensuring a sufficient engine output and reducing the possibility of thermal damage of the catalyst. The present invention relates to a control device.

  Recently, a variable valve timing mechanism (VVT mechanism) capable of continuously changing the timing of opening an intake valve (intake opening timing) and the timing of closing an exhaust valve (exhaust closing timing) has been adopted for engines mounted on automobiles and the like. Some have. By controlling this VVT mechanism, it is possible to continuously change the valve overlap amount (section from the intake opening timing to the exhaust closing timing). In general, in a low and medium load region, the valve overlap amount is increased and the internal EGR amount is increased to improve exhaust gas purification performance and improve fuel efficiency by reducing pumping loss. On the other hand, in the high load range, the intake opening timing and the exhaust closing timing are controlled by the VVT mechanism from the viewpoint of improving the output, and the valve overlap amount is relatively small as the engine speed increases. It will change from a state to a larger state and again to a smaller state. Thus, the timing for opening the intake valve (intake opening timing) and the timing for closing the exhaust valve (exhaust closing timing) are appropriately controlled according to the operating state (see, for example, Patent Document 1).

By the way, in exhaust gas exhausted from an engine mounted on an automobile or the like, pollution that may adversely affect the environment, such as carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide (NO _x ), etc. Contains substances. For this reason, in general, for example, a catalyst for decomposing (reducing, etc.) the pollutants is disposed in the exhaust passage through which the exhaust gas discharged from the engine passes, and the exhaust gas is made as harmless as possible. It is made to be released into the atmosphere.

Japanese Patent No. 2749226

  In an engine equipped with the above-described VVT mechanism, desired intake opening timing and exhaust closing timing are appropriately set according to the operating state, and the valve overlap amount changes accordingly. Further, the amount of the unburned mixture flowing into the catalyst changes with the change in the valve overlap amount. For example, as the valve overlap amount increases, the amount of unburned mixture flowing into the catalyst also increases. If the amount of the unburned mixture flowing into the catalyst increases more than necessary, the temperature of the catalyst rises beyond the allowable temperature, and there is a risk that thermal damage such as thermal deterioration and melting damage may occur.

  Specifically, since the valve overlap amount is normally set according to the operation state of the flat ground (standard state), of course, it is set without any problem in the operation state of the flat ground. There is a risk that the setting may not be suitable for driving conditions at high altitudes.

  For example, on a flat ground, when a high output is required at a low and medium speed full load (throttle valve fully open), the valve overlap amount is a relatively small value from the viewpoint of improving the output. On the other hand, at high altitudes, the weight of intake air decreases as the air density decreases even when high output is required at full load. For this reason, the target valve overlap amount regardless of the full load is a relatively large value for the purpose of improving exhaust gas purification performance and improving fuel efficiency by reducing pumping loss. The air-fuel mixture is easily supplied to the catalyst more than necessary.

  Further, since the atmospheric pressure is lower than that on a flat ground at high altitude, the exhaust pressure decreases, and the differential pressure between the cylinder and the exhaust pipe increases. For this reason, considering the case where the valve overlap amount is fixed and the intake air weight into the cylinder is the same, the air weight that blows through the cylinder from the cylinder to the exhaust pipe during the valve overlap is higher than the flat ground at high altitude. As a result, a large amount of unburned mixture tends to flow into the catalyst at high altitudes. Further, when the operating state is a high load (the air-fuel ratio is aimed at the output air-fuel ratio), the air-fuel ratio is rich (the amount of unburned fuel is large), so a large amount of unburned air-fuel mixture is more likely to flow into the catalyst. .

  For this reason, in an engine equipped with a VVT mechanism, as described above, the temperature of the catalyst exceeds the allowable temperature, and there is a risk of causing thermal damage to the catalyst. Especially in high altitudes, such catalyst heat damage is likely to occur.

  In the control device described in Patent Document 1 and the like, the valve timing is appropriately set according to the atmospheric pressure to prevent a decrease in output at high altitude. By setting the valve timing (overlap amount) according to the atmospheric pressure in this way, the above-described problem such as the heat damage of the catalyst may be suppressed to some extent, but the heat damage of the catalyst is related to the flat ground and the high ground. There is a possibility that it may occur due to factors other than atmospheric pressure, and simply controlling the valve timing according to atmospheric pressure is not sufficient as a measure for avoiding thermal damage to the catalyst.

  Such a problem is particularly likely to occur at high altitudes, but, of course, may also occur at level.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide an engine control device that can reduce the possibility of thermal damage of a catalyst while sufficiently securing the output of the engine. To do.

  A first aspect of the present invention that solves the above problems includes a variable valve timing mechanism that changes the opening / closing timing of one or both of an intake valve and an exhaust valve, and a catalyst that is provided in an exhaust passage and purifies exhaust gas. An engine control apparatus comprising: an operation state detection unit that detects an operation state of the engine; a temperature detection unit that detects a temperature of the catalyst; and a detection result of the operation state detection unit Target value setting means for setting a target value of an intake opening timing that is a timing for opening the intake valve and a target value of an exhaust closing timing that is a timing for closing the exhaust valve; and the intake opening timing and the exhaust closing timing are respectively A control unit that feedback-controls the variable valve timing mechanism to achieve a target value, and a target value setting unit that is set based on a detection result of the temperature detection unit. Sometimes the engine control apparatus wherein the comprising a correction means for correcting the target value.

  In the first aspect, the variable valve timing mechanism is controlled based on the target values of the intake opening timing and the exhaust closing timing corrected by the correcting means, so that the temperature of the catalyst can be maintained while sufficiently securing the engine output. It is possible to avoid a rise in excess of the allowable temperature and to reduce the possibility of thermal damage of the catalyst.

  According to a second aspect of the present invention, the correcting means delays the target value of the intake opening timing and / or closes the exhaust when the detection result of the temperature detecting means exceeds a preset set temperature. The engine control apparatus according to the first aspect is characterized in that the target value of the time is advanced. That is, in this aspect, the correction means corrects the target value so that the valve overlap amount is reduced.

  In the second aspect, the target value is corrected to suppress the catalyst temperature increase, and the catalyst temperature can be prevented from rising beyond the allowable temperature.

  According to a third aspect of the present invention, the correction means advances the target value of the intake opening timing and / or the target of the exhaust closing timing when the detection result of the temperature detection means is below the set temperature. The engine control apparatus according to the first or second aspect is characterized in that the value is delayed. That is, in this aspect, the correction means corrects the target value so that the valve overlap amount is increased.

  In the third aspect, it is possible to avoid a situation in which the temperature of the catalyst rises beyond the allowable temperature, and it is also possible to avoid the temperature of the catalyst from being lowered more than necessary. That is, since the temperature of the catalyst is maintained within a predetermined range, it is possible to avoid a situation in which the catalyst exhibits its function sufficiently and causes heat damage.

  The fourth aspect of the present invention further includes atmospheric pressure detection means for detecting atmospheric pressure, wherein the target value setting means sets the target value according to a detection result of the atmospheric pressure detection means, The engine control device according to any one of the first to third aspects is characterized in that the higher the value is, the longer the target value of the intake opening timing is delayed and / or the target value of the exhaust closing timing is advanced. That is, in this aspect, the setting means sets the target value so that the valve overlap amount is reduced according to the atmospheric pressure.

  In the fourth aspect, it is possible to more reliably reduce the possibility of thermal damage of the catalyst.

  According to a fifth aspect of the present invention, there is provided a turbocharger in which the engine rotates a turbine disposed in the exhaust passage by exhaust and rotates a compressor disposed in the intake passage to supercharge intake air. The correction means delays the target value of the intake opening timing and / or accelerates the target value of the exhaust closing timing when supercharging is performed by the turbocharger. It exists in the control apparatus of the engine of any one aspect. In other words, in this aspect, the correction means corrects the target value so that the valve overlap amount is reduced when supercharging is performed by the turbocharger.

  In the fifth aspect, it is possible to more reliably reduce the possibility of thermal damage of the catalyst while ensuring sufficient engine output.

  According to a sixth aspect of the present invention, there is provided an engine including a variable valve timing mechanism that changes an opening / closing timing of one or both of an intake valve and an exhaust valve, and a catalyst that is provided in an exhaust passage and purifies exhaust gas. An operation state detection means for detecting an operation state of the engine, a temperature detection means for detecting the temperature of the catalyst, and the intake valve and the exhaust gas according to a detection result of the operation state detection means. A target value setting means for setting a target value of a valve overlap amount with the valve, a control means for feedback controlling the variable valve timing mechanism so that the valve overlap amount becomes the target value, and a temperature detection means A control unit for correcting the target value set by the target value setting unit based on a detection result; A.

  In the sixth aspect, the variable valve timing mechanism is controlled based on the target value of the valve overlap amount corrected by the correcting means, so that the catalyst temperature can be set at the allowable temperature while sufficiently securing the engine output. It is possible to reduce the possibility of thermal damage of the catalyst by avoiding the rise beyond the range.

  According to a seventh aspect of the present invention, in the sixth aspect, the correction means decreases the target value when the detection result of the temperature detection means exceeds a preset temperature. In the engine control unit.

  In the seventh aspect, a decrease in the target value can suppress an increase in the temperature of the catalyst, and an increase in the temperature of the catalyst beyond the allowable temperature can be avoided.

  According to an eighth aspect of the present invention, in the sixth or seventh aspect, the correction means increases the target value when a detection result of the temperature detection means is below the set temperature. Located in the engine control unit.

  In the eighth aspect, it is possible to avoid a situation where the temperature of the catalyst rises beyond the allowable temperature, and it is also possible to avoid that the temperature of the catalyst falls more than necessary. That is, since the temperature of the catalyst is maintained within a predetermined range, it is possible to avoid a situation in which the catalyst exhibits its function sufficiently and causes heat damage.

  The ninth aspect of the present invention further includes atmospheric pressure detection means for detecting atmospheric pressure, wherein the target value setting means sets the target value according to the detection result of the atmospheric pressure detection means, The engine control device according to any one of the sixth to eighth aspects is characterized in that the target value is decreased as the value increases.

  In the ninth aspect, the target value is set so that the valve overlap amount is reduced as the atmospheric pressure is higher, so that the possibility of thermal damage of the catalyst can be more reliably reduced.

  According to a tenth aspect of the present invention, there is provided a turbocharger in which the engine rotates a turbine disposed in the exhaust passage by exhaust and rotates a compressor disposed in the intake passage to supercharge intake air. The correction means is the engine control device according to any one of the sixth to ninth aspects, wherein the target value is decreased when supercharging is performed by the turbocharger.

  In the tenth aspect, it is possible to more reliably reduce the possibility of thermal damage of the catalyst while ensuring sufficient engine output.

  In the engine control apparatus according to the present invention, the target value of the intake opening timing and the exhaust closing timing or the target value of the valve overlap amount is appropriately corrected according to the temperature of the exhaust purification catalyst. It is possible to avoid the occurrence of thermal damage by suppressing the excessive temperature rise accompanying the increase in the amount of unburned mixture flowing into the catalyst while ensuring the engine output sufficiently while ensuring the appropriate amount of overlap. it can.

  Hereinafter, the present invention will be described based on embodiments.

(Embodiment 1)
FIG. 1 is a diagram illustrating a schematic configuration of an engine system including a control device according to the first embodiment. Hereinafter, in this embodiment, the case where this control device is applied to an intake pipe injection type gasoline engine will be described as an example.

  An engine 11 shown in FIG. 1 is an intake pipe injection (Multi Point Injection) engine, and has a cylinder head 12 and a cylinder block 13. A piston 15 is accommodated in each cylinder 14 of the cylinder block 13 so as to be reciprocally movable. A combustion chamber 16 is formed by the piston 15, the cylinder 14, and the cylinder head 12. The piston 15 is connected to the crankshaft 18 via a connecting rod 17. The reciprocating motion of the piston 15 is transmitted to the crankshaft 18 via the connecting rod 17.

  An intake port 19 is formed in the cylinder head 12. An intake manifold 20 is connected to the intake port 19. The intake port 19 is provided with an intake valve 22, which operates in accordance with the cam 23 a of the camshaft 23 that rotates in accordance with the engine rotation, and allows communication between the combustion chamber 16 and the intake port 19. It is configured to block. For example, an electromagnetic fuel injection valve 24 is provided in the intake manifold 20, and a fuel supply device having a fuel tank is connected to the fuel injection valve 24 via a fuel valve (not shown).

  An exhaust port 25 is further formed in the cylinder head 12. One end of an exhaust manifold 26 is connected to the exhaust port 25, and an exhaust pipe (exhaust passage) 27 is connected to the other end of the exhaust manifold 26. The exhaust port 25 is provided with an exhaust valve 28, and the exhaust valve 28 operates following the cam 29 a of the camshaft 29, similar to the intake valve 22 in the intake port 19, and the combustion chamber 16 and the exhaust port. It is comprised so that communication and interruption | blocking with 25 may be performed.

  The cylinder head 12 is provided with variable valve timing mechanisms (VVT mechanisms) 30 and 31 for varying the opening and closing timings of the intake valve 22 and the exhaust valve 28 by advancing or retarding the rotational phase of the cams 23a and 29a. ing. By changing the phases of the cams 23a and 29a that drive the intake valve and the exhaust valve with respect to the crankshaft by the variable valve timing mechanisms 30 and 31, respectively, the intake opening timing and the exhaust valve 28 that are the timing for opening the intake valve 22 are changed. The exhaust closing timing, which is the timing for closing the engine, can be changed.

  Various known variable valve timing mechanisms 30 and 31 can be applied. For example, a hydraulic type capable of continuously changing the phases of the cams 23a and 29a is preferably used. In this embodiment, the variable valve timing mechanisms 30 and 31 are provided on the intake cam 23a and the exhaust cam 29a, respectively. However, the variable valve timing mechanisms 30 and 31 are provided on either the intake cam 23a or the exhaust cam 29a. It may be provided.

  A spark plug 32 is attached to the cylinder head 12 for each cylinder. Each spark plug 32 is connected to an ignition coil 33 that outputs a high voltage. A surge tank 34 is provided on the upstream side of the intake manifold 20. A throttle valve 35 that adjusts the intake air amount is provided upstream of the surge tank 34, and a throttle position sensor (TPS) 36 that detects the opening of the throttle valve 35 is also provided. Although not shown, the throttle valve 35 is adjusted in opening degree in conjunction with the operation of the accelerator pedal. An air flow sensor 37 that measures the intake air amount is interposed upstream of the throttle valve 35.

An exhaust pipe 27 connected to the exhaust manifold 26 is provided with an exhaust purification catalyst 38. On the upstream side of the catalyst 38, for example, an O ₂ sensor 39 that detects the oxygen concentration in the exhaust gas before passing through the catalyst 38 is provided. That is, the exhaust air / fuel ratio is detected based on the output information of the O ₂ sensor 39, and the fuel injection amount is feedback controlled in accordance with the exhaust air / fuel ratio. The catalyst 38 is provided with a temperature sensor (temperature detection means) 40 for detecting the temperature of the catalyst 38.

  As will be described in detail later, in the present embodiment, the target values of the intake opening timing and the exhaust closing timing are corrected based on the detection result of the temperature sensor 40 (correction means), and the VVT mechanism 30 is adjusted so as to have the corrected target values. , 31 is controlled by feedback (control means) to suppress the occurrence of thermal damage to the catalyst 38.

The ECU (electronic control unit) 41 includes an input / output device, a storage device (ROM, RAM, etc.), a central processing unit (CPU), a timer counter, and the like. The ECU 41 performs comprehensive control of the engine 11. On the input side of the ECU 41, in addition to the throttle position sensor 36, the air flow sensor 37, the O ₂ sensor 39, the temperature sensor 40, etc., the crank angle sensor 42 for detecting the crank angle of the engine 11 and the water temperature of the engine 11 are detected. Various sensors such as a water temperature sensor 43 that detects atmospheric pressure and an atmospheric pressure sensor 44 that detects atmospheric pressure are connected, and detection information from these sensors is input.

  On the other hand, various output devices such as the fuel injection valve 24, the ignition coil 33, the VVT mechanisms 30, 31, and the throttle valve 35 are connected to the output side of the ECU 41. These various output devices output predetermined information from the ECU 41 based on detection information from various sensors.

  The control device 10 of the present embodiment is configured by such various sensors and the ECU 41, and as described in detail below, based on information such as the operating state of the engine 11 detected by the various sensors, the intake air opening and closing is performed. The target values of the timing and the exhaust closing timing are appropriately set (target value setting means), and the VVT mechanisms 30 and 31 are feedback-controlled so that the actual intake opening timing and exhaust closing timing become the target values (control means). Further, by appropriately correcting the target values of the intake opening timing and the exhaust closing timing in accordance with the temperature of the catalyst 38 detected by the temperature sensor (temperature detection means) 40 (correction means), the temperature rise of the catalyst 38 is suppressed and the heat is increased. The occurrence of harm is suppressed.

  In the present embodiment, the engine rotation speed Ne and the charging efficiency Ec of the engine 11 are detected as the operating state of the engine 11, and the target value (target intake opening time) for opening the intake valve 22 (intake opening timing) according to the detection result. Timing) and a target value (target exhaust closing timing) for closing the exhaust valve 28 (exhaust closing timing) are set (target value setting means), and the actual intake opening timing and exhaust closing timing are set to the above target values. Thus, the VVT mechanisms 30 and 31 are appropriately feedback controlled.

  Here, the target intake opening timing (target IO) and the target exhaust closing timing (target EC) are set with reference to each map stored in the ECU 41. In each map, the target intake opening timing or the target exhaust closing timing according to the engine rotation speed Ne and the charging efficiency Ec of the engine 11 on the flat ground (standard time) is mapped. Then, based on the engine rotation speed Ne of the engine 11 detected by the crank angle sensor 42 as the operating state detecting means and the charging efficiency Ec calculated from the intake air amount detected by the airflow sensor 37 as the operating state detecting means. The target intake opening timing and target exhaust closing timing are set with reference to each map.

  As described above, in the present embodiment, the target intake opening timing and the target exhaust closing timing are set with reference to the map created according to the operating condition of the flat ground. For this reason, for example, when a change in atmospheric pressure or the like occurs, the target intake opening timing and the target exhaust closing timing deviate from the optimum values, and accordingly, the temperature of the catalyst 38 may excessively increase.

  However, in the present invention, the temperature of the catalyst 38 is detected by the temperature sensor 40 serving as the temperature detection means, and the target intake opening timing and the target exhaust closing timing are corrected based on the detection result. Temperature rise can be suppressed.

  FIG. 2 is an example of a timing chart according to the first embodiment, and is a diagram illustrating a relationship among atmospheric pressure, throttle position sensor (TPS), charging efficiency Ec, catalyst temperature, target intake opening timing, and target exhaust closing timing.

  For example, as shown in FIG. 2, on a flat ground where the atmospheric pressure is relatively high, the charging efficiency Ec also increases to a value close to the maximum value during high load operation (when the opening of the TPS is close to full open). In this case, the target intake opening timing and the target exhaust closing timing are set with emphasis on output. Although depending on the engine speed, the target intake opening timing and the target exhaust closing timing are set such that the valve overlap amount V1 is relatively small. That is, the target intake opening timing is set to the retard side by a predetermined amount with reference to the intake top dead center, and the target exhaust closing timing is set to the advance side by a predetermined amount with reference to the intake top dead center. The VVT mechanisms 30 and 31 are feedback-controlled so that the actual intake opening timing becomes the target intake opening timing and the actual exhaust closing timing becomes the target exhaust closing timing.

  On the other hand, during low and medium load operation, for example, when the opening of the TPS is about half open, the charging efficiency Ec is also about half the maximum value (near the intermediate value). In this case, the target intake opening timing and the target exhaust closing timing are set such that the valve overlap amount V2 is larger than the valve overlap amount V1 during high-load operation with an emphasis on fuel efficiency. That is, the amount of retardation based on the intake top dead center at the target intake opening timing is further increased than that at the time of high load operation, and the advance amount of the target exhaust closing timing is further increased. The VVT mechanisms 30 and 31 are feedback-controlled so that the actual intake opening timing becomes the target intake opening timing and the actual exhaust closing timing becomes the target exhaust closing timing.

  When the target intake opening timing and the target exhaust closing timing change in this way, the amount of unburned mixture flowing into the exhaust purification catalyst 38 increases or decreases accordingly, and the temperature of the catalyst 38 changes. However, as described above, the target intake opening timing and the target exhaust closing timing are set with reference to a map created according to the operating state of the engine 11 on the flat ground, and therefore are optimal values on the flat ground. Basically, the temperature of the catalyst 38 does not rise beyond the allowable temperature.

  At high altitudes where the atmospheric pressure is lower than the flat ground, the density of air decreases, so the charging efficiency Ec decreases even at the same TPS opening as the flat ground. The filling efficiency Ec is lower as the atmospheric pressure is lower. As shown in FIG. 2, during high load operation at high altitude, the charging efficiency Ec does not increase to the vicinity of the maximum value. The target intake opening timing and target exhaust closing timing at this time are set with reference to a map created in accordance with the operation state on a flat ground. Therefore, at high altitudes, the valve overlap amount V3 becomes equal to the valve overlap amount V2 at low to medium load operation on flat ground even during high load operation.

  For this reason, at high altitudes (particularly during high load operation), the valve overlap amount becomes too large, and the amount of unburned mixture flowing into the catalyst 38 increases. Furthermore, since the exhaust pressure decreases as the atmospheric pressure decreases at high altitudes, the amount of unburned mixture flowing into the catalyst 38 increases even if the valve overlap amount is the same as that on flat ground. Therefore, at high altitudes (particularly during high load operation), the temperature of the catalyst 38 rises above the allowable temperature and heat damage is likely to occur.

  However, in this embodiment, the temperature of the catalyst 38 is detected by the temperature sensor 40, and the target intake opening timing and the target exhaust closing timing are appropriately corrected based on the detection result. Thereby, the excessive temperature rise of the catalyst 38 can be prevented, and the occurrence of heat damage of the catalyst 38 can be suppressed.

  Hereinafter, the setting and correction processing of the target intake opening timing and the target exhaust closing timing will be described in detail. FIG. 3 is a flowchart showing a target intake opening timing setting and correction process, and FIG. 4 is a flowchart showing a target exhaust opening timing setting and correction process. The target intake opening timing and the target exhaust closing timing are actually set and corrected at the same time. First, the setting and correction processing of the target intake opening timing will be described with reference to FIG.

  As shown in FIG. 3, first, in step S11, a predetermined map is referred to based on detection results of the air flow sensor 37 and the crank angle sensor 42 as the operating state detecting means, that is, the engine rotational speed Ne and the charging efficiency Ec. The initial value IO_base of the target intake opening timing is obtained and set. The VVT mechanism 30 is feedback-controlled so that the actual intake opening timing becomes the target intake opening timing (IO_base).

  In the following steps, the target intake opening timing (IO_base) thus set is corrected as appropriate according to the temperature of the catalyst 38. In the present embodiment, the target intake opening timing is corrected at predetermined intervals, and the gain (correction gain: Gio) of the target intake opening timing in one correction is constant.

  First, in step S12, it is determined whether or not the temperature of the catalyst 38 detected by the temperature sensor 40 is higher than a preset upper limit value limitT_U of the set temperature, and the temperature of the catalyst 38 is higher than the upper limit value of the set temperature. If it is higher (step S12: Yes), the correction gain Gio is subtracted from the previous correction amount ΔIO (n−1) to obtain the current correction amount (correction amount from the initial value IO_base) ΔIO (n) (step). S13). For example, in the case of the first correction, the target intake opening timing is the initial value IO_base and the correction amount ΔIO (n−1) = 0, so that the correction amount ΔIO (n) = Gio.

  On the other hand, if the temperature of the catalyst 38 is equal to or lower than the upper limit value limitT_U of the set temperature in step S12 (step S12: No), whether or not the temperature of the catalyst 38 is lower than the lower limit value limitT_L of the set temperature in step S14. Determine whether. Here, if the temperature of the catalyst 38 is equal to or lower than the lower limit value of the set temperature (step S14: Yes), the correction gain Gio is added to the previous correction amount ΔIO (n−1) and the current correction amount ΔIO (n). (Step S15). When the temperature of the catalyst 38 is higher than the lower limit value of the set temperature (step S14: No), the current correction amount ΔIO (n) is maintained as the previous correction amount ΔIO (n−1) (step S16). . After calculating the current correction amount ΔIO (n) in this way, the target intake opening timing is corrected. That is, a value obtained by adding the current correction value ΔIO (n) to the initial value IO_base of the target intake opening timing is set as the target intake opening timing (step S17).

  Basically, the VVT mechanism 30 is feedback-controlled so that the target intake opening timing corrected in this way is reached. In this embodiment, the target intake opening timing is further set within a predetermined range. The upper limit and lower limit of the intake opening timing are set.

  Specifically, first, in step S18, it is determined whether or not the current target intake opening timing is greater than the initial value IO_base. That is, in this embodiment, the upper limit value of the target intake opening timing is set to the initial value IO_base, and it is determined in step S18 whether the target intake opening timing is larger than the upper limit value.

  The upper limit value of the target intake opening timing is set to the initial value IO_base. As described above, the initial value IO_base of the target intake opening timing is set with reference to a map created according to the driving condition of the flat ground. For this reason, it is already on the retard side of the target intake opening timing that is optimal for the driving condition in high altitudes.

  If the target intake opening timing is larger than the upper limit value (IO_base) (step S18: Yes), the target intake opening timing is set to the initial value IO_base in step S19 and the correction value ΔIO (n) is corrected last time. The value is returned to ΔIO (n−1), and the process is terminated. On the other hand, when the target intake opening timing is less than or equal to the upper limit value (IO_base) (step S18: No), the target intake opening timing is equal to or less than the value obtained by subtracting the limit value limit ΔIO of the correction amount ΔIO from the initial value (IO_base) in step S20. It is determined whether or not. That is, it is determined whether or not the target intake opening timing is equal to or lower than the lower limit value. The limit value limit ΔIO is an arbitrary value set in advance, and may be determined as appropriate according to the temperature characteristics of the catalyst 38 and the like.

  If the target intake opening timing is equal to or lower than the lower limit value (step S20: Yes), the lower limit value is set as the target intake opening timing in step S21 and the correction value ΔIO (n) is set to the previous correction value ΔIO (n−). Returning to 1), the process is terminated. If the target intake opening timing is larger than the lower limit value (step S20: No), the process is terminated as it is.

  As described above, in the present invention, the target value (target intake opening timing) of the valve overlap amount is appropriately corrected according to the detection result of the temperature detection means 40 (temperature of the catalyst 38). That is, when the temperature of the catalyst 38 exceeds the set temperature, the valve overlap amount is decreased to suppress the temperature increase of the catalyst 38. As a result, an excessive temperature rise of the catalyst 38 can be suppressed, and heat damage to the catalyst 38 can be suppressed.

  In the example shown in FIG. 2, for example, the temperature Te1 of the catalyst 38 at time T1 is equal to or lower than the lower limit value limitT_L of the set temperature (step S14), so the correction amount ΔIO (1) = ΔIO (0) + Gio at this time (Step S15). The correction at time T1 is the first correction, and since the correction amount ΔIO (0) = 0 at time T0, the current correction amount ΔIO (1) = Gio. Therefore, normally, the target intake opening timing is (IO_base + Gio) (step S17), but in this embodiment, the upper limit value of the target intake opening timing is set to the initial value IO_base (step S18). The intake opening timing becomes the initial value IO_base, and the current correction amount ΔIO (1) is returned to the previous correction amount ΔIO (0) (step S19).

  At time T2, since the temperature Te2 of the catalyst 38 has risen to a temperature higher than the upper limit value limitT_U of the set temperature (step S12), the correction amount ΔIO (2) = ΔIO (1) −Gio (step S13). . Since ΔIO (1) has been returned to ΔIO (0) as described above, the correction amount ΔIO (2) = − Gio. Therefore, the target intake opening timing is (IO_base-Gio) (step S17). That is, the target intake opening timing is set to the advance side by Gio from the initial value IO_base with reference to the intake top dead center.

  At time T3, similarly to time T2, the temperature Te3 of the catalyst 38 is maintained at a temperature higher than the upper limit value limitT_U of the set temperature (step S12), so that the correction amount ΔIO (3) = ΔIO (2) −Gio = -2Gio (step S13). Therefore, the target intake opening timing is (IO_base-2Gio) (step S17). That is, the target intake opening timing is set to the advance side by 2 Gio from the initial value IO_base with reference to the intake top dead center.

  Incidentally, assuming that the limit value limitΔIO = Gio of the correction amount is set, the lower limit value of the target intake opening timing is IO_base-Gio. In this case, since the target intake opening timing is equal to or lower than the lower limit value at time T3 (step S20), the target intake opening timing is IO_base-Gio, and the correction amount ΔIO (3) is the previous correction amount ΔIO (2 ) (Step S21).

  At time T4, the temperature Te4 of the catalyst 38 decreases and is lower than the upper limit value limitT_U of the set temperature and higher than the lower limit value limitT_L of the set temperature (step S14), so the correction amount ΔIO (4) is the previous time. The correction amount ΔIO (3) is maintained (step S16). In this example, ΔIO (4) = − 2Gio. Accordingly, the target intake opening timing is also maintained as (IO_base-2Gio) (step S17).

  At time T5, since the temperature Te5 of the catalyst 38 has fallen below the lower limit value limitT_L of the set temperature (step S14), the correction amount ΔIO (5) = ΔIO (4) + Gio (step S15). Since the correction amount ΔIO (4) = − 2Gio, ΔIO (5) = − Gio. Therefore, the target intake opening timing is (IO_base-Gio) (step S17). That is, the target intake opening timing is set to the retard side by Gio with respect to the intake top dead center with respect to the value at time T4.

  If the throttle valve is fully closed after that, the upper limit value and the lower limit value of the target intake opening timing coincide with each other. Therefore, the above calculation itself is continued, but the target intake opening timing is actually increased. Will not be corrected.

  As described above, the target intake opening timing is set and corrected, and similarly, the target exhaust closing timing is set and corrected. That is, the setting and correction processing of the target exhaust gas closing timing is the same as in the case of the target intake air opening timing except that the addition and subtraction of the correction gain Gec are reversed. Hereinafter, setting and correction of the target exhaust gas closing timing will be briefly described.

  As shown in FIG. 4, first, in step S31, an initial value EC_base of the target exhaust gas closing timing is obtained and set with reference to a predetermined map based on the detection results of the air flow sensor 37 and the crank angle sensor 42. In step S32, it is determined whether or not the temperature of the catalyst 38 is higher than the upper limit value limitT_U of the set temperature. If the temperature of the catalyst 38 is higher than the upper limit value of the set temperature (step S32: Yes), the previous time The correction gain Gec is added to the correction amount ΔEC (n−1) to obtain the current correction amount (correction amount from the initial value) ΔEC (n) (step S33).

  On the other hand, when the temperature of the catalyst 38 is equal to or lower than the upper limit value limitT_U of the set temperature (step S32: No), it is further determined in step S34 whether the temperature of the catalyst 38 is lower than the lower limit value limitT_L of the set temperature. To do. Here, if the temperature of the catalyst 38 is equal to or lower than the lower limit value of the set temperature (step S34: Yes), the correction gain Gec is subtracted from the previous correction amount ΔEC (n−1), and the current correction amount ΔEC (n). (Step S35). When the temperature of the catalyst 38 is higher than the lower limit value of the set temperature (step S34: No), the current correction amount ΔEC (n) is maintained as the previous correction amount ΔEC (n−1) (step S36). . After calculating the current correction amount ΔEC (n) in this way, the target exhaust gas closing timing is corrected. That is, a value obtained by adding the current correction value ΔEC (n) to the initial value EC_base of the target exhaust closing timing is set as the target exhaust closing timing (step S37).

  Next, in step S38, it is determined whether or not the target exhaust closing timing is equal to or smaller than the initial value EC_base of the target exhaust closing timing. That is, in this embodiment, the lower limit value of the target exhaust gas closing timing is set to the initial value EC_base, and it is determined in step S38 whether the target exhaust gas closing timing is equal to or lower than the lower limit value.

  If the target exhaust closing timing is equal to or lower than the lower limit (initial value) (step S38: Yes), the target exhaust closing timing is set to the initial value EC_base in step S39 and the correction value ΔEC (n) is set to the previous value. The process returns to the correction value ΔEC (n−1) and the process ends. On the other hand, when the target exhaust gas closing timing is larger than the lower limit value (initial value) (step S38: No), the target exhaust gas closing timing is obtained by adding the limit value limit ΔEC of the correction amount ΔEC to the initial value EC_base in step S40. It is determined whether or not it is larger. That is, it is determined whether the target exhaust gas closing timing is greater than the upper limit value.

  If the target exhaust closing timing is larger than the upper limit value (step S40: Yes), the upper limit value is set as the target exhaust closing timing in step S41, and the process is terminated. If the target exhaust closing timing is less than or equal to the upper limit value (step S40: No), the process is terminated as it is.

  As described above, in the present embodiment, the target intake opening timing and the target exhaust closing timing are set according to the temperature of the catalyst 38, that is, when the temperature of the catalyst 38 exceeds the upper limit value of the set temperature. Since the correction for decreasing the target exhaust gas closing timing is performed, an excessive temperature rise of the catalyst 38 can be suppressed. Therefore, it is possible to suppress the occurrence of heat damage due to the temperature of the catalyst 38 exceeding the allowable temperature.

  Further, in the present embodiment, when the temperature of the catalyst 38 is equal to or lower than the lower limit value of the set temperature, correction for increasing the target intake opening timing and the target exhaust closing timing again is performed. Furthermore, in this embodiment, the upper limit value and the lower limit value of the target intake opening timing and the target exhaust closing timing are set. As a result, the temperature of the catalyst 38 is stabilized, and the exhaust purification performance of the catalyst 38 is maintained well.

  In this embodiment, since the set temperature is provided with hysteresis, the temperature of the catalyst 38 can be stabilized. Of course, this set temperature does not necessarily have hysteresis. That is, the upper limit value and the lower limit value of the set temperature described in the present embodiment may match.

  FIG. 2 shows an example in which the target intake opening timing at high altitude is corrected. Of course, the target intake opening timing at flat ground may be corrected. Also, as described above, the temperature of the catalyst 38 is particularly likely to rise at high altitudes, so of course, only the target intake opening timing at high altitudes may be corrected. Specifically, for example, when the detection result of the atmospheric pressure sensor 44 is lower than a predetermined value, the target intake opening timing may be corrected.

(Embodiment 2)
In the first embodiment, an example in which the target intake opening timing and the target exhaust closing timing are set with reference to a map mapped according to the operation state on the flat ground regardless of whether it is a flat ground or a high ground, that is, regardless of the atmospheric pressure. However, in the present embodiment, maps for flat land and high ground are stored, and the target intake opening timing and target exhaust closing timing corresponding to the atmospheric pressure are set with reference to these maps. This is an example. Specifically, the target intake opening timing and the target exhaust closing timing are set so that the target value of the valve overlap amount decreases as the atmospheric pressure increases. In addition, since the structure of the engine system containing the control apparatus 10 is the same as that of Embodiment 1, description is abbreviate | omitted.

  FIG. 5 is an example of a timing chart according to the second embodiment, and is a diagram illustrating a relationship among the atmospheric pressure, the throttle position sensor (TPS), the charging efficiency Ec, the catalyst temperature, the target intake opening timing, and the target exhaust closing timing. FIG. 6 is a flowchart showing target intake opening timing setting and correction processing according to the second embodiment, and FIG. 7 is a block diagram showing a target intake opening timing (initial value) calculation method. FIG. 8 is a flowchart showing target exhaust opening timing setting and correction processing according to the second embodiment. In this embodiment, the target intake opening timing and the target exhaust closing timing are actually set and corrected simultaneously. First, the setting and correction processing of the target intake opening timing will be described.

  As shown in FIG. 6, in steps S51 to S53, the initial value IO_base of the target intake opening timing is obtained and set according to the operating state of the engine 11 and the atmospheric pressure. In the present embodiment, for example, as shown in FIG. 7, a map (planar map) 101 of the target intake opening timing (IO_base) indicated by the relationship between the rotational speed Ne of the engine 11 and the charging efficiency Ec on a flat ground, A target intake opening timing (IO_base) map (high altitude map) 102 indicated by the relationship between the rotational speed Ne of the engine 11 and the charging efficiency Ec, and a coefficient map 103 indicating the relationship between the atmospheric pressure and the interpolation coefficient. Then, the target intake opening timing (IO_base) optimum for the current atmospheric pressure is set from these maps 101, 102, 103. The high altitude map 102 of the target intake opening timing indicates the target intake opening timing at the highest point (lowest atmospheric pressure) in the assumed range.

  Specifically, in step S51, the initial value IO_l of the target intake opening timing on the flat ground is obtained from the flat land map 101 based on the detection results of the air flow sensor 37 and the crank angle sensor 42, and the high ground map 102 An initial value IO_h of the target intake opening timing is obtained. Next, in step S52, the interpolation coefficient K is obtained with reference to the coefficient map 103 based on the detection result of the atmospheric pressure sensor 44. In step S53, the initial value IO_base of the target intake opening timing optimum for the current atmospheric pressure is calculated and set from these values using the following equation (1).

  IO_base = K × IO_h + (1−K) × IO_l (1)

  As shown in FIG. 5, the initial value IO_base is set between an initial value IO_l of the target intake opening timing on flat ground and an initial value IO_h of the target intake opening timing on high ground. At this time, the VVT mechanism 30 is feedback-controlled so that the actual intake opening timing becomes the target intake opening timing (IO_base).

  In the following steps, the target intake opening timing set in this way is corrected as appropriate according to the temperature of the catalyst 38. Specifically, the target intake opening timing is appropriately corrected in steps S12 to S17 described in the first embodiment. In addition, since the process of step S12-step S17 is as above-mentioned, description is abbreviate | omitted.

  Basically, the VVT mechanism 30 is feedback-controlled so as to achieve the target intake opening timing corrected in this way. However, as in the case of the first embodiment, this target intake opening is further performed in this embodiment. The upper limit value and the lower limit value of the target intake opening timing are set so that the timing falls within a predetermined range. In the present embodiment, the upper limit value of the target intake opening timing is set to the initial value IO_l of the target intake opening timing on flat ground, and the lower limit value is set to the initial value IO_base of the target intake opening timing optimum for the current atmospheric pressure. Yes.

  Specifically, first, in step S54, it is determined whether or not the target intake opening timing is greater than the initial value IO_l on a flat ground. That is, it is determined whether or not the target intake opening timing is greater than the upper limit value.

  If the target intake opening timing is greater than the upper limit value (IO_l) (step S54: Yes), the target intake opening timing is set to the upper limit value (IO_l) and the correction value ΔIO (n) is set to the previous value in step S55. The process returns to the correction value ΔIO (n−1) and the process is terminated. On the other hand, when the target intake opening timing is equal to or lower than the upper limit value (IO_l) (step S54: No), the target intake opening timing is equal to or less than the initial value IO_base of the target intake opening timing optimum for the current atmospheric pressure in step S56. It is determined whether or not there is. That is, it is determined whether or not the target intake opening timing is equal to or lower than the lower limit value.

  If the target intake opening timing is equal to or lower than the lower limit value (step S56: Yes), the lower limit value (IO_base) is set as the target intake opening timing in step S57 and the correction value ΔIO (n) is set to the previous correction value ΔIO. Returning to (n-1), the process is terminated. If the target intake opening timing is larger than the lower limit value (IO_base) (step S56: No), the processing is ended as it is.

  The target exhaust closing timing is set and corrected in the same manner as the target intake opening timing. As shown in FIG. 8, in steps S61 to S63, an initial value EC_base of the target exhaust gas closing timing is obtained and set according to the operating state of the engine 11 and the atmospheric pressure. That is, as in the case of the target intake opening timing, the target exhaust closing timing (EC_base) that is optimal for the current atmospheric pressure is set from the flat map, the high map, and the coefficient map.

  Specifically, in step S61, an initial value EC_l of the target exhaust closing timing on the flat ground is obtained from the flat map based on the detection results of the airflow sensor 37 and the crank angle sensor 42, and the target exhaust at the high ground is calculated from the high map. The initial value EC_h of the closing time is obtained. Next, in step S62, based on the detection result of the atmospheric pressure sensor 44, the interpolation coefficient K is obtained with reference to the count map. In step S63, the initial value EC_base of the target exhaust gas closing timing optimum for the current atmospheric pressure is calculated and set from these values using the following equation (2).

  EC_base = K * EC_h + (1-K) * EC_l (2)

  As shown in FIG. 5, the initial value EC_base is set between the initial value EC_l of the target exhaust gas closing timing on flat ground and the initial value EC_h of the target exhaust gas closing timing on high ground. At this time, the VVT mechanism 30 is feedback-controlled so that the actual exhaust closing timing becomes the target exhaust closing timing (EC_base).

  In the following steps, the target exhaust gas closing timing set in this way is corrected as appropriate according to the temperature of the catalyst 38. Specifically, the target exhaust gas closing timing is corrected as appropriate in steps S32 to S37 described in the first embodiment. In addition, since the process of step S32-step S37 is as above-mentioned, description is abbreviate | omitted.

  Basically, the VVT mechanism 31 is feedback-controlled so that the target exhaust closing timing corrected in this way is reached. As in the case of the first embodiment, the target exhaust closing is further performed in the present embodiment. The upper limit value and the lower limit value of the target exhaust gas closing timing are set so that the timing falls within a predetermined range. In this embodiment, the upper limit value of the target exhaust gas closing timing is set to the initial value EC_base of the target exhaust gas closing timing optimum for the current atmospheric pressure, and the lower limit value is set to the initial value EC_l of the target exhaust gas closing timing on flat ground. Yes.

  Specifically, first, in step S64, it is determined whether or not the target exhaust gas closing timing is larger than the initial value EC_base of the target exhaust gas closing timing optimum for the current atmospheric pressure. That is, it is determined whether the target exhaust gas closing timing is greater than the upper limit value.

  If the target exhaust closing timing is larger than the upper limit value (EC_base) (step S64: Yes), the target exhaust closing timing is set to the upper limit value (EC_base) in step S65 and the correction value ΔEC (n) is set to the previous value. The process returns to the correction value ΔEC (n−1) and the process ends. On the other hand, if the target exhaust closing timing is equal to or lower than the upper limit value (EC_base) (step S64: No), whether or not the target exhaust closing timing is equal to or lower than the initial value EC_l of the target exhaust closing timing on flat ground in step S66. Determine. That is, it is determined whether the target exhaust gas closing timing is equal to or lower than the lower limit value.

  If the target exhaust closing timing is equal to or lower than the lower limit value (step S66: Yes), the lower limit value (EC_l) is set as the target exhaust closing timing in step S67 and the correction value ΔEC (n) is set to the previous correction value ΔEC ( Returning to n-1), the process is terminated. If the target exhaust closing timing is larger than the lower limit value (EC_l) (step S66: No), the process is terminated as it is.

  As described above, in the present embodiment, the initial values of the target intake opening timing and the target exhaust closing timing, which are correction references, are set according to the current atmospheric pressure. By appropriately correcting the intake opening timing and the target exhaust closing timing, an excessive temperature rise of the catalyst 38 can be more reliably suppressed. Therefore, it is possible to more reliably reduce the possibility of heat damage such as melting damage and thermal deterioration occurring in the catalyst 38.

(Other embodiments)
As mentioned above, although embodiment of this invention was described, of course, this invention is not limited to such embodiment.

  The configuration of the engine to which the control device of the present invention is applied is not particularly limited. For example, the engine may include a turbocharger that performs supercharging of the intake air by rotating a compressor provided in the intake system by rotating a turbine provided in the exhaust system by exhaust gas.

  Then, when controlling an engine equipped with such a turbocharger, correction for reducing the target intake opening timing when supercharging is performed by the turbocharger is performed together with the correction of the target intake opening timing based on the catalyst temperature described above. Is preferable. For example, in the above-described embodiment, when the temperature of the catalyst 38 is equal to or lower than the upper limit value limitT_U of the set temperature and higher than the lower limit value limitT_L of the set temperature, the target intake air opening timing is not corrected. Maintained. However, even when the temperature of the catalyst 38 is such a temperature, correction may be performed to decrease the target intake opening timing if supercharging is performed by the turbocharger.

  When supercharged by a turbocharger, the output can be improved, but the amount of unburned mixture flowing into the catalyst also greatly increases, so the catalyst is particularly susceptible to thermal damage. By reducing the target intake opening timing when supercharging is performed, it is possible to more reliably avoid the heat damage of the catalyst while ensuring sufficient output of the engine 11.

  In the above-described embodiment, the example in which the valve overlap amount is determined by setting the target intake opening timing and the target exhaust closing timing by the setting means has been described. However, the present invention is limited to such an embodiment. It is not something. For example, the setting means may set a target value of the valve overlap amount, and the target intake opening timing and the target exhaust closing timing may be determined according to the target value of the valve overlap amount.

  Further, in the above-described embodiment, the present invention has been described by exemplifying an intake pipe injection type engine. However, the present invention can be applied to other types of engines such as a cylinder injection type, for example. Needless to say.

1 is a schematic configuration diagram of an engine system including a control device according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating an example of a timing chart according to the first embodiment. 4 is a flowchart showing a target intake opening timing setting and correction process according to the first embodiment. 6 is a flowchart showing a target exhaust gas closing timing setting and correction process according to the first embodiment. 6 is a diagram illustrating an example of a timing chart according to Embodiment 2. FIG. 6 is a flowchart showing a target intake opening timing setting and correction process according to the second embodiment. It is a block diagram which shows the calculation method of the initial value of the target intake opening timing which concerns on Embodiment 2. FIG. 6 is a flowchart showing a target exhaust gas closing timing setting and correction process according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Control apparatus 11 Engine 12 Cylinder head 13 Cylinder block 14 Cylinder 15 Piston 16 Combustion chamber 17 Connecting rod 18 Crankshaft 19 Intake port 20 Intake manifold 22 Intake valve 23a Cam 23 Camshaft 24 Fuel injection valve 25 Exhaust port 26 Exhaust manifold 27 Exhaust pipe 28 Exhaust valve 29a Cam 29 Camshaft 30, 31 Variable valve timing mechanism (VVT mechanism)
32 Spark plug 33 Ignition coil 34 Surge tank 35 Throttle valve 36 Throttle position sensor (TPS)
37 Airflow sensor 38 Catalyst 39 O ₂ sensor 40 Temperature sensor 41 ECU
42 Crank angle sensor 43 Water temperature sensor 44 Atmospheric pressure sensor

Claims (10)

An engine control device comprising a variable valve timing mechanism that changes the opening / closing timing of either or both of an intake valve and an exhaust valve, and a catalyst that is provided in an exhaust passage and purifies exhaust gas,
An operating state detecting means for detecting an operating state of the engine;
Temperature detecting means for detecting the temperature of the catalyst;
Target value setting means for setting a target value of an intake opening timing that is a timing of opening the intake valve and a target value of an exhaust closing timing that is a timing of closing the exhaust valve according to a detection result of the operating state detection means;
Control means for feedback-controlling the variable valve timing mechanism so that the intake opening timing and the exhaust closing timing become respective target values;
Correction means for correcting the target value set by the target value setting means based on the detection result of the temperature detection means;
An engine control device comprising:   The correction means delays the target value of the intake opening timing and / or accelerates the target value of the exhaust closing timing when the detection result of the temperature detection means exceeds a preset set temperature. The engine control device according to claim 1.   The correction means, when the detection result of the temperature detection means is below the set temperature, advances the target value of the intake opening timing and / or delays the target value of the exhaust closing timing. Item 3. The engine control device according to Item 1 or 2. It further comprises an atmospheric pressure detection means for detecting atmospheric pressure,
The target value setting means sets the target value according to the detection result of the atmospheric pressure detecting means, and delays the target value of the intake opening timing and / or sets the target value of the exhaust closing timing as the atmospheric pressure increases. The engine control device according to any one of claims 1 to 3, wherein the engine control device is advanced. The engine includes a turbocharger that supercharges intake air by rotating a compressor disposed in an intake passage by rotating a turbine disposed in the exhaust passage by exhaust.
The correction means delays the target value of the intake opening timing and / or accelerates the target value of the exhaust closing timing when supercharging is performed by the turbocharger. The engine control device according to claim 1. An engine control device comprising a variable valve timing mechanism that changes the opening / closing timing of either or both of an intake valve and an exhaust valve, and a catalyst that is provided in an exhaust passage and purifies exhaust gas,
An operating state detecting means for detecting an operating state of the engine;
Temperature detecting means for detecting the temperature of the catalyst;
Target value setting means for setting a target value of a valve overlap amount between the intake valve and the exhaust valve according to a detection result of the operating state detection means;
Control means for feedback-controlling the variable valve timing mechanism so that the valve overlap amount becomes the target value;
Correction means for correcting the target value set by the target value setting means based on the detection result of the temperature detection means;
An engine control device comprising:   7. The engine control apparatus according to claim 6, wherein the correction unit decreases the target value when a detection result of the temperature detection unit exceeds a preset temperature.   The engine control device according to claim 6 or 7, wherein the correction unit increases the target value when a detection result of the temperature detection unit is lower than the set temperature. It further comprises an atmospheric pressure detection means for detecting atmospheric pressure,
The target value setting means sets the target value according to the detection result of the atmospheric pressure detection means, and decreases the target value as the atmospheric pressure is higher. The engine control device according to Item. The engine includes a turbocharger that supercharges intake air by rotating a compressor disposed in an intake passage by rotating a turbine disposed in the exhaust passage by exhaust.
The engine control device according to any one of claims 6 to 9, wherein the correction unit decreases the target value when supercharging is performed by the turbocharger.

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