JP4577444B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine that controls operation characteristics of an intake valve and an exhaust valve of each cylinder during operation of the internal combustion engine.

  Conventionally, this type of device is used to optimize the operating characteristics of intake valves and exhaust valves corresponding to the rotational phase of the output shaft of an internal combustion engine, that is, the profile on the time axis related to the operation amount of each valve.

  For example, a valve timing control device known as a device for variably controlling the operation timing (valve timing) of intake valves and exhaust valves of an internal combustion engine shares one camshaft of the engine (internal combustion engine) as a rotation axis. A mechanism (variable valve timing mechanism) including the first rotating part and the second rotating part as constituent elements. The first rotating part is driven and connected to the crankshaft by a chain or the like and rotates in synchronization with the crankshaft. The second rotating part is formed integrally with the camshaft and rotates in synchronization with the camshaft. Furthermore, the relative rotational phase between the first rotating unit and the second rotating unit can be changed through hydraulic control. That is, the valve timing control device performs control (valve timing control) for continuously changing the valve timing by hydraulically driving the variable valve timing mechanism and changing the relative phase of the two rotating parts constituting the mechanism. Do.

  FIG. 14 is a cross-sectional view schematically showing an example of a conventionally known variable valve timing mechanism.

  As shown in FIG. 14, the variable valve timing mechanism 500 includes a housing (first rotating portion) 502 that is drivingly connected to an engine crankshaft (not shown), and an internal rotor (locked to the camshaft). 2nd rotation part) 501 is provided as a main component. The housing includes a plurality of protrusions 502a protruding from the inner peripheral surface thereof toward the rotation axis, and the internal rotor 501 includes a plurality of protrusions (vanes) 501a protruding radially from the outer peripheral surface thereof. The convex portions 502a of the housing 502 are partitioned by the vanes 501a of the internal rotor 501, and hydraulic chambers 501 and 502 are formed on the left and right sides of the vanes 501a. When the engine on which the mechanism is mounted is operating, the hydraulic chambers 501 and 502 are filled with hydraulic oil of a predetermined hydraulic pressure by the action of a hydraulic pump (not shown) driven by the engine output. Then, by appropriately changing the hydraulic pressure of these hydraulic oils based on a command signal from an electronic control device or the like, the relative phase of both rotating parts 501, 502, that is, the relative rotational phase between the crankshaft and the camshaft is variably controlled. Is done.

By the way, when the temperature of the hydraulic oil is low and its viscosity is high, such as when the engine is started, sufficient hydraulic pressure is not applied to each hydraulic chamber. Thus, under the condition that sufficient hydraulic pressure is not applied to the hydraulic chamber in the housing 502, for example, vibration (valve reaction force torque) resulting from the reciprocating motion of the valve is transmitted to the internal rotor via the camshaft, The vane 501 a of the internal rotor 501 swings in the housing 502. As a result, it is difficult not only to stabilize the relative phase of the rotating parts 501 and 502 in a desired arrangement, but also a problem such that the vane 501a and the inner wall of the housing 502 repeatedly collide and separate to generate a hitting sound. . Therefore, like the lock pin mechanism 531A shown in the figure, the engine is started using a mechanism configuration in which the housing 502 and the internal rotor 501 can be engaged with each other and the relative phases of the rotating parts can be fixed at a specific position. In some cases, it is common to fix the relative phases of the rotating parts 501 and 502 when the valve timing determined by the relative phase of the rotating parts 501 and 502 is most retarded. The relative phase of both rotating parts 501 and 502 at this time is hereinafter referred to as “most retarded angle position”.

  The lock pin mechanism 531A includes a columnar lock pin for appropriately connecting the internal rotor 501 and the housing 502, and a lock pin accommodation hole that is formed through the vane 501a of the internal rotor 501 in the camshaft direction and accommodates the lock pin therein. A coil spring for urging the lock pin accommodated in the lock pin accommodation hole toward the inner wall of the housing and a locking hole formed in the inner wall of the housing are provided as main components. Further, when both the rotating parts 501 and 502 are at the most retarded position, the lock pin accommodation hole and the locking hole communicate with each other.

  That is, when the variable valve timing mechanism 500 stops its operation, the spring force of the coil spring pushes the tip end portion of the lock pin into the locking hole, and the relative phases of the rotating portions 501 and 502 are at the most retarded position. It is fixed with. On the other hand, when the variable valve timing mechanism 500 is in an operating state, the hydraulic pressure of the hydraulic oil supplied into the locking hole and the lock pin accommodating hole through a predetermined oil passage acts in a direction opposite to the biasing force of the coil spring. Then, push the lock pin back into the lock pin accommodation hole.

  As a result, when the engine is started, the relative phases of the rotating parts 501 and 502 are locked at the most retarded position, and the hydraulic oil supplied into the housing 502 is sufficient as a medium for transmitting driving force to the variable valve timing mechanism 500. When the functions of the two rotating parts 501 and 502 become independent, the mutually independent operations are allowed.

  By applying the lock pin mechanism as described above (hereinafter referred to as the retard position lock pin mechanism) and locking the relative phase of both rotating parts at the most retarded position when starting the engine, the variable valve timing mechanism when starting the engine The instability of the operating state and the occurrence of sound are eliminated.

  However, when the retard position lock pin mechanism as described above is applied, after the engine is started, the engine operation must be continued while the relative phase of both rotating parts is locked at the most retarded position for a considerable period. Disappear. This is because it takes a considerably long time for the temperature of the hydraulic oil to rise so that the function of the variable valve timing mechanism can be fully exerted. In addition, the valve timing corresponding to the state where the relative phase of both rotating parts is at the most retarded position is considerably different from the optimum valve timing when the internal combustion engine is in a normal operating state. If the phase is kept locked at the most retarded position, suitable exhaust characteristics and drivability cannot be expected. That is, the opportunity to improve exhaust characteristics and dryness from the viewpoint of optimization of valve timing will be lost for a long time after the engine is started.

  With respect to such a problem, the control device described in Japanese Patent Application Laid-Open No. 11-210424 operates on substantially the same principle as the retard angle position lock pin mechanism, and the relative rotation of both rotating parts constituting the valve timing variable mechanism. A device configuration is employed in which a lock pin mechanism (hereinafter referred to as an intermediate position lock pin mechanism) capable of fixing the phase at an intermediate position in the variable range is provided separately from the retard position lock pin mechanism. That is, at the time of engine start, the relative phase of both rotating parts constituting the variable valve timing mechanism is fixed at the most retarded angle position by using the retard angle position lock pin mechanism, and then the operating state of the engine is referred to. While moving to an intermediate position, it is fixed there using an intermediate position lock pin mechanism. Then, when the oil temperature of the hydraulic oil rises and the function of the variable valve timing mechanism is fully exerted, the fixing of the relative phases of both rotating parts is released.

By utilizing such a function of the intermediate position lock pin mechanism, adjustment of the valve timing is sufficient even under conditions where sufficient controllability cannot be obtained when the variable valve timing mechanism is operated due to the low oil temperature. It is possible to minimize the deterioration of the engine performance caused by not being performed.

Japanese Patent Laid-Open No. 11-210424

  However, the intermediate position lock pin mechanism as described above has a functional characteristic that appropriately locks the relative phase of both rotating parts constituting the variable valve timing mechanism at the intermediate position of the variable range. When this happens, control to change the relative phase of both rotating parts is hindered in the middle of the variable range.

  When such a problem occurs, when performing valve timing control by driving the valve timing variable mechanism, not only the reliability of the control is impaired, but also based on the target valve timing in the valve timing control. The influence on other operation control is not small. As a result, the exhaust characteristics are deteriorated and drivability is lowered.

  In addition to the devices that control the valve timing using the variable valve timing mechanism as described above, the operating range for the reciprocating operation of the intake and exhaust valves (the lift amount of each valve, the working angle of the camshaft, etc.) Has a function of changing the relative operating characteristics of the intake valve and the exhaust valve with respect to the rotational operation of the crankshaft of the internal combustion engine, etc., and fixes the operating characteristics in the middle of the variable range. Such a problem has been common for devices equipped with mechanisms.

  The present invention has been made in view of such circumstances, and has a function of changing the relative operating characteristics of the intake valve and the exhaust valve with respect to the rotational operation of the crankshaft of the internal combustion engine, and the operating characteristics. An object of the present invention is to provide a control device for an internal combustion engine that can suitably suppress a decrease in engine operating performance due to a malfunction of the mechanism in a device having a mechanism for fixing the engine in the middle of its variable range.

  In order to achieve the above object, according to a first aspect of the present invention, at least one of an intake valve and an exhaust valve that reciprocates in conjunction with a rotation operation of an output shaft of an internal combustion engine varies an operation characteristic corresponding to the rotation operation of the output shaft. A valve characteristic variable mechanism, an actual characteristic detection means for detecting an actual operational characteristic corresponding to the rotational operation of the output shaft, and a valve whose operational characteristic is variable. A target characteristic setting means for setting a target operating characteristic based on the operating state of the engine, and based on the actual operating characteristic and the target operating characteristic, the actual operating characteristic becomes the target operating characteristic. Control gain setting means for setting the control gain of the variable valve characteristic mechanism so as to agree with the operating characteristic of the variable valve, In a control device for an internal combustion engine having a locking mechanism for locking at a position and a locking mechanism control means for controlling an operating state of the locking mechanism, a change is made based on the target operating characteristics and the control gain. The gist of the present invention is to include a difference calculating means for calculating a difference from the actual operating characteristic and a correcting means for correcting a parameter relating to operation control of the engine based on the calculated difference.

Here, the operation characteristic of the intake valve or the exhaust valve corresponding to the rotation operation of the output shaft is the time related to the opening / closing operation amount of each valve (for example, the lift amount of each valve, the working angle of the camshaft) with respect to the rotation phase of the output shaft. Means on-axis profile. Further, the intermediate position of the movable range means any position within the movable range.

  If the valve characteristic variable mechanism is functioning normally, the actual operating characteristics of the valve whose operating characteristics are variable follow the target operating characteristics sequentially. However, when a malfunction such as a malfunction occurs in the locking mechanism, the actual operating characteristic does not follow the target operating characteristic, and therefore the operating state of the internal combustion engine corresponding to the target operating characteristic ( For example, exhaust characteristics, torque characteristics, etc.) cannot be obtained. According to this configuration, even when a malfunction occurs in the operating state of the locking mechanism, the disturbance of the operation state of the internal combustion engine caused by such a malfunction is promptly synchronized with the timing of the occurrence of the disturbance. To be corrected. Therefore, when the internal combustion engine is operated, an operation state corresponding to the target operating characteristics of the variable valve is stably secured.

  Further, the second aspect of the present invention provides a variable valve characteristic in which the operation characteristic corresponding to the rotation operation of the output shaft is variable for at least one of the intake valve and the exhaust valve that reciprocate in conjunction with the rotation operation of the output shaft of the internal combustion engine. An actual characteristic detecting means for detecting an actual operating characteristic corresponding to the rotational operation of the output shaft, and a valve of which the operating characteristic is variable; Target characteristic setting means for setting a target operating characteristic based on an operating state; and the actual operating characteristic based on the actual operating characteristic and the target operating characteristic so that the actual operating characteristic matches the target operating characteristic Control gain setting means for setting the control gain of the valve characteristic variable mechanism, and when the actual operating characteristic is sufficiently approximated to the target operating characteristic, Holding control means for holding the operating characteristics of the valve, a locking mechanism for locking the operating characteristics of the variable valve at an intermediate position in the variable range, and a locking mechanism for controlling the operating state of the locking mechanism The control device of the internal combustion engine having the control means includes a holding prohibiting means for prohibiting the holding of the operating characteristics when the actual operating characteristics are in a predetermined range including the intermediate position.

  According to this configuration, since the operation characteristic of the valve having the variable operation characteristic is not held in the vicinity of the locking position by the locking mechanism, the malfunction of the locking mechanism may occur. It is preferably suppressed (occurrence probability is minimized). Accordingly, the followability and reliability of the control for causing the actual operating characteristic of the variable valve to follow the target operating characteristic is improved. That is, when the internal combustion engine is operated, an operation state corresponding to the target operation characteristic is stably secured for the valve whose operation characteristic is variable.

  According to a third aspect of the present invention, there is provided a variable valve characteristic in which an operation characteristic corresponding to the rotation operation of the output shaft is variable for at least one of an intake valve and an exhaust valve that reciprocate in conjunction with the rotation operation of the output shaft of the internal combustion engine. An actual characteristic detecting means for detecting an actual operating characteristic corresponding to the rotational operation of the output shaft, and a valve of which the operating characteristic is variable; Target characteristic setting means for setting a target operating characteristic based on an operating state; and the actual operating characteristic based on the actual operating characteristic and the target operating characteristic so that the actual operating characteristic matches the target operating characteristic Control gain setting means for setting the control gain of the valve characteristic variable mechanism, and when the actual operating characteristic is sufficiently approximated to the target operating characteristic, Holding control means for holding the operating characteristics of the valve, a locking mechanism for locking the operating characteristics of the variable valve at an intermediate position in the variable range, and a locking mechanism for controlling the operating state of the locking mechanism And a control means for controlling the internal combustion engine, wherein the target characteristic setting means sets the target operating characteristic outside a predetermined range including the intermediate position.

According to this configuration, since the operation characteristics of the valve whose operation characteristics are variable do not converge in the vicinity of the locking position by the locking mechanism, the malfunction of the locking mechanism is preferable. (Probability of occurrence is minimized). Accordingly, the followability and reliability of the control for causing the actual operating characteristic of the variable valve to follow the target operating characteristic is improved. That is, when the internal combustion engine is operated, the operation state corresponding to the target operation characteristic is stably secured for the valve whose operation characteristic is variable.

  According to a fourth aspect of the present invention, there is provided a variable valve characteristic for varying an operation characteristic corresponding to the rotation operation of the output shaft for at least one of an intake valve and an exhaust valve that reciprocates in conjunction with the rotation operation of the output shaft of the internal combustion engine. An actual characteristic detecting means for detecting an actual operating characteristic corresponding to the rotational operation of the output shaft, and a valve of which the operating characteristic is variable; Target characteristic setting means for setting a target operating characteristic based on an operating state; and the actual operating characteristic based on the actual operating characteristic and the target operating characteristic so that the actual operating characteristic matches the target operating characteristic Control gain setting means for setting the control gain of the variable valve characteristic mechanism, and a mechanism for locking the variable operation characteristic of the valve at an intermediate position in the variable range. In a control device for an internal combustion engine having a mechanism and a locking mechanism control means for controlling the operating state of the locking mechanism, when the operating characteristic of the variable valve is within a predetermined range including the intermediate position And an acceleration means for increasing the speed of changing the operating characteristics.

  According to this configuration, since the speed at which the operating characteristic is changed becomes high in the vicinity of the locking position of the locking mechanism, the malfunction of the locking mechanism is preferably generated. Suppressed (occurrence probability is minimized). Accordingly, the followability and reliability of the control for causing the actual operating characteristic of the variable valve to follow the target operating characteristic is improved. That is, when the internal combustion engine is operated, an operation state corresponding to the target operation characteristic is stably secured for the valve whose operation characteristic is variable.

  In each of the above-described configurations, for example, the operation phase of at least one of the intake valve and the exhaust valve (as an operation characteristic) is made variable (valve characteristic variable) by displacing the rotational phase of the camshaft with respect to the rotational phase of the output shaft of the internal combustion engine. A variable valve timing mechanism (as a mechanism) and an actual valve timing calculation that calculates the actual valve timing (as an operating characteristic) of the valve based on the phase difference between the rotation phase of the engine output shaft and the rotation phase of the camshaft Means, a calculation means for calculating a target valve timing of the valve based on the operating state of the engine, and a control gain of the valve timing variable mechanism based on these calculated values so that the actual operating valve timing matches the target valve timing Control means for setting the actual operation valve timing A locking mechanism for locking a range intermediate position, to the control apparatus for an internal combustion engine having, can be suitably applied.

  In addition, each of the above-described configurations includes, for example, a housing that is connected to one of a camshaft and an output shaft of an internal combustion engine and that has a partition wall formed radially therein, and the camshaft and the output shaft. A vane body connected to the other and rotatably disposed inside the housing and having a radial vane that divides a partition formed in the housing by the partition wall into an advance hydraulic chamber and a retard hydraulic chamber; , Hydraulic control for controlling the hydraulic oil pressure supplied to the advance hydraulic chamber and the retard hydraulic chamber and changing the relative rotational phase of the output shaft and the camshaft by rotating the vane body relative to the housing. An apparatus and the vane body, and when the pressure in the hydraulic chamber is lower than a predetermined pressure, the vane body protrudes from the vane body and engages with an engagement hole provided in the housing. Timing control of an internal combustion engine having an intermediate position lock pin (as a locking mechanism) for locking the relative rotational phase (valve timing) between the motor and the housing at an intermediate position between the most advanced position and the most retarded position The present invention can be suitably applied to the apparatus.

  Further, the valve timing control device, when the actual operating valve timing and the target valve timing are sufficiently approximated, calculates a holding control gain calculating means for calculating a holding control gain for holding the actual operating valve timing at that time. It is preferable to have further.

  As described above, according to the first aspect, even if a malfunction occurs in the operating state of the locking mechanism, the disturbance of the operating state of the internal combustion engine caused by such a malfunction is not affected by the disturbance. It is corrected promptly in synchronization with the occurrence timing. Accordingly, when the internal combustion engine is operated, an operation state corresponding to the target operating characteristics of the variable valve is stably secured.

  Further, according to the second aspect of the present invention, since the operating characteristics of the valve whose operating characteristics are variable are not held near the locking position by the locking mechanism, the malfunction of the locking mechanism is prevented. Generation is suitably suppressed (occurrence probability is minimized). Accordingly, the followability and reliability of the control for causing the actual operating characteristic of the variable valve to follow the target operating characteristic is improved. That is, when the internal combustion engine is operated, an operation state corresponding to the target operation characteristic is stably secured for the valve whose operation characteristic is variable.

  According to the third aspect of the invention, the operating characteristics of the valve whose operating characteristics are variable do not converge near the locking position by the locking mechanism, and thus the malfunction of the locking mechanism occurs. Is preferably suppressed (occurrence probability is minimized). Accordingly, the followability and reliability of the control for causing the actual operating characteristic of the variable valve to follow the target operating characteristic is improved. That is, when the internal combustion engine is operated, an operation state corresponding to the target operation characteristic is stably secured for the valve whose operation characteristic is variable.

  Furthermore, according to the fourth aspect of the present invention, since the speed at which the operating characteristic is changed is increased in the vicinity of the locking position by the locking mechanism, the malfunction of the locking mechanism is caused. It is preferably suppressed (occurrence probability is minimized). Accordingly, the followability and reliability of the control for causing the actual operating characteristic of the variable valve to follow the target operating characteristic is improved. That is, when the internal combustion engine is operated, an operation state corresponding to the target operation characteristic is stably secured for the valve whose operation characteristic is variable.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the outline | summary of the engine provided with the valve timing control apparatus concerning the 1st Embodiment of this invention. Sectional drawing which mainly shows the front sectional structure of the valve timing variable mechanism concerning the embodiment. Sectional drawing which shows typically the front sectional structure of the valve timing variable mechanism concerning the embodiment. Sectional drawing which shows the cross-sectional structure of the retard position lock pin of the valve timing variable mechanism concerning the embodiment, and its periphery site | part. Sectional drawing which shows the cross-section of the intermediate position lock pin of the valve timing variable mechanism concerning the embodiment, and its peripheral part. The time chart which shows the transition aspect of the actual operation valve timing observed during implementation of the valve timing control concerning the embodiment, and the waveform of the duty command value adopted at this time on the same time axis. The flowchart which shows the valve timing control procedure of the same embodiment. Changes in the actual operating valve timing observed when a request to increase the internal EGR occurs in the engine, changes in the internal EGR, and changes in the amount of NOx discharged to the engine exhaust passage (NOx generation amount) The time chart which illustrates a mode on the same time axis. The flowchart which shows the fuel injection amount correction | amendment procedure of the embodiment. The flowchart which shows the valve timing control procedure concerning the 2nd Embodiment of this invention. Sectional drawing which shows typically the cross-section of the intermediate position lock pin of the valve timing variable mechanism concerning the embodiment, and its peripheral part. The flowchart which shows the valve timing control procedure concerning the 3rd Embodiment of this invention. The time chart which shows the transition aspect of the actual operation valve timing observed during implementation of the valve timing control concerning the embodiment, and the waveform of the duty command value adopted at this time on the same time axis. Sectional drawing which shows roughly the front sectional structure of the valve timing variable mechanism with which the conventional valve timing control apparatus is equipped.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described. The device of the present embodiment is a control device (valve timing control device) provided in an in-vehicle engine.

  In FIG. 1, an in-vehicle engine (hereinafter referred to as an engine) 1 as an internal combustion engine includes a plurality of cylinders 11. A piston 12 provided in each cylinder 11 so as to be able to reciprocate is connected to a crankshaft 14, which is an output shaft of the engine 1, via a connecting rod 13. A combustion chamber 15 is formed above the piston 12 in the cylinder 11. The igniter 16 induces a high voltage at an appropriate timing to generate an electric spark at the spark plug 17. The air-fuel mixture introduced into the combustion chamber 15 is ignited by an electric spark generated by the spark plug 17. The combustion chamber 15 communicates with the intake passage 31 through the intake port 30 and with the exhaust passage 41 through the exhaust port 40.

  A fuel injection valve 18 is provided so that the injection hole faces the intake port 30. The fuel injection valve 18 injects fuel (gasoline) transferred from a fuel tank (not shown) via a pressure pump (not shown) into the intake port 30 (in the direction toward the combustion chamber). In the middle of the intake passage 31, a surge tank 32 for suppressing intake air pulsation and an air cleaner box 33 for removing dust and dirt in the intake air are provided. An air flow meter 51 that outputs an electric signal corresponding to the mass of air (intake air mass) is attached. A throttle valve 34 for adjusting the flow rate of the intake air flowing in the intake passage 31 is provided in a portion downstream of the air flow meter 51 in the intake passage 31.

  The throttle valve 34 includes a throttle actuator 34 a that opens and closes the valve 34, and a throttle position sensor that outputs an electric signal corresponding to the opening (throttle opening) TA of the throttle valve 34 to an electronic control unit (ECU) 50. In addition to 52, an accelerator position sensor 53 that is mechanically connected to the accelerator pedal 35 and outputs an electric signal corresponding to the operation amount of the accelerator pedal 35 to the ECU 50 is attached.

  On the other hand, in the middle of the exhaust passage 41, a catalyst casing 42 and a muffler (not shown) are provided, and an electric signal corresponding to the air-fuel ratio of the exhaust gas flowing into the catalyst casing 42 through the passage 41 is output to the ECU 50. An air-fuel ratio sensor 54 is attached.

  For example, when the air-fuel ratio of the exhaust gas flowing into the catalyst casing 42 is a predetermined air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio, the catalyst casing 42 includes hydrocarbons (HC) and carbon monoxide (CO) contained in the exhaust gas. In addition, a three-way catalyst for purifying nitrogen oxide (NOx) is provided in the interior.

  The crank angle sensor 55 including a timing rotor 55a attached to the end of the crankshaft 14 and an electromagnetic pickup 55b attached in the vicinity of the timing rotor 55a is in accordance with the rotational phase of the crankshaft 14. An electric signal is output to the ECU 50. Based on the time interval of the signal output from the crank angle sensor 55, the engine speed NE is calculated. A cooling water passage 1 c is formed in the cylinder block 1 a that forms the outline of the cylinder 11 and the cylinder 11 head 1 b that forms the outline of the intake port 30 and the exhaust port 40. A water temperature sensor 56 is provided at a predetermined portion of the cooling water passage 1c, and an electric signal corresponding to the temperature (cooling water temperature) THW of the cooling water flowing through the cooling water passage 1c is output to the ECU 50.

  The open end of the intake port 30 facing the combustion chamber is opened and closed by an intake valve 36 supported so as to be able to advance and retreat in the cylinder head 1b. Further, the open end of the exhaust port 40 facing the combustion chamber is opened and closed by an exhaust valve 46 that is supported by the cylinder head 1b so as to be able to advance and retract. These valves 36 and 46 are interlocked with the rotational operations of the intake camshaft 37 and the exhaust camshaft 47, respectively. In addition, cam sprockets 38 and 48 attached to the leading ends of the intake camshaft 37 and the exhaust camshaft 47 are connected to the crankshaft 14 via the timing chain 19.

  During operation of the engine 1, the rotational force of the crankshaft 14 is transmitted to the camshafts 37 and 47 via the timing chain 19 and the intake cam sprockets 38 and 48. As a result, the camshafts 37 and 47 rotate in synchronization with the rotation of the crankshaft 14 and open and close the valves 36 and 46 at a predetermined timing corresponding to the reciprocation of the piston 12. That is, the valves 36 and 46 are operable at a predetermined timing in synchronization with the intake stroke, compression stroke, explosion / expansion stroke, and exhaust stroke of the engine 1 according to the vertical movement of the piston 12.

  The tip of the intake camshaft 37 to which the intake cam sprocket 38 is attached has a relative rotational phase between the intake cam sprocket 38 and the intake camshaft 37, in other words, a relative position between the crankshaft 14 and the intake camshaft 37. A variable valve timing mechanism 100 for variably adjusting the rotation phase (the valve timing of the intake valve 36) is configured. The variable valve timing mechanism 100 is operated by hydraulic control based on a command signal from the ECU 50. The cam angle sensor 57 including a timing rotor (not shown) attached to the end portion of the intake camshaft 37 and an electromagnetic pickup 57b attached in the vicinity of the timing rotor is an intake camshaft 37. An electric signal corresponding to the rotational phase of the ECU 50 is output to the ECU 50.

  The ECU 50 is a known microcomputer. Inside the ECU 50, a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), a backup RAM, a timer counter, an external input circuit including an A / D converter, an external output circuit, etc. Connected to form a logical operation circuit.

The ECU 50 configured as described above is attached to each part of the engine 1 in addition to the throttle position sensor 52, the accelerator position sensor 53, the air-fuel ratio sensor 54, the crank angle sensor 55, the water temperature sensor 56, and the cam angle sensor 57. Detection signals output from various sensors are input via an external input circuit, and various information related to the operating state of the engine 1 is grasped. And based on these various information, each component of the engine 1, such as the igniter 16, the fuel injection valve 18, the throttle valve 34, and the valve timing variable mechanism 100, is driven. That is, the ECU 50 determines the fuel injection control (fuel injection control) to the intake port 30 performed through the fuel injection valve 18 and the ignition timing of the air-fuel mixture introduced into the combustion chamber 15 (timing to apply current to the igniter). Various controls relating to the operation of the engine 1 such as control (ignition timing control) or drive control (valve timing control) of the variable valve timing mechanism 100 are also executed.

  The variable valve timing mechanism 100 constitutes a valve timing control device for the engine 1 together with various peripheral members (including the ECU 50) for hydraulically driving the mechanism 100.

  Hereinafter, the valve timing control apparatus having such a configuration will be described in detail.

  FIG. 2 shows a front sectional structure of the variable valve timing mechanism 100 and a schematic configuration of various peripheral members of the mechanism 100.

  As shown in FIG. 2, the internal rotor 101 provided in the variable valve timing mechanism 100 is fastened to the tip of the intake camshaft 37 with a bolt or the like so that it can rotate integrally with the intake camshaft 37. The Four blade bodies (vanes) 101 a are radially formed on the outer periphery of the inner rotor 101.

  A housing 102 is provided so as to cover the outer periphery of the inner rotor 101. These housings 102 can be integrally rotated with the intake cam sprocket 38 by being fixed to the intake cam sprocket 38 by a plurality of mounting bolts 103. The same number (four) of convex portions 102a as the vanes 101a of the inner rotor 101 are formed on the inner periphery of the housing 102, and individual vanes are formed in the concave portions 104 formed between the adjacent convex portions 102a. 101a is accommodated.

  The tip of the vane 101 a is in sliding contact with the inner periphery of the recess 104, and the tip of the protrusion 102 a is in sliding contact with the outer periphery of the internal rotor 101. As a result, the internal rotor 101 and the intake camshaft 37, the intake cam sprocket 38, and the housing 102 can be relatively rotated around the same axis.

  In addition, two spaces 105 and 106 are formed in the recess 104 by being partitioned by the vane 101a. Thereafter, of these two spaces 105 and 106, the space 105 on the rotation direction (arrow arrow α direction) side of the intake camshaft 37 with respect to the vane 101a is the retard hydraulic chamber, and the space 106 on the opposite side is the advance hydraulic chamber. That's it. Further, through holes (accommodating holes) 120 and 130 are formed through the two vanes 101 a provided in the inner rotor 101 along the axial direction of the camshaft 37. A retard position lock pin 121 is accommodated in the accommodation hole 120, and an intermediate position lock pin 131 is accommodated in the accommodation hole 130. The retard position lock pin 121 and the intermediate position lock pin 131 have a function of fixing the inner rotor 101 and the housing 102 to a specific relative phase.

  In the variable valve timing mechanism 100 configured in this way, the relative phase between the rotating parts 101 and 102 can be freely controlled by controlling the hydraulic pressure supplied to each part such as the retard hydraulic chamber 105 and the advance hydraulic chamber 106. Changed or retained.

  Next, a hydraulic control system that controls the hydraulic pressure supplied to each part of the variable valve timing mechanism 100 will be described.

  In FIG. 2, the oil pump 201 is mechanically driven based on the rotational force of the crankshaft 37, sucks the hydraulic oil in the oil pan 202, and supplies it to the oil control valve (OCV) 203 via the supply oil path P1. Supply hydraulic oil.

  The OCV 203 is a four-port valve whose opening degree is controlled based on duty control. In addition to the supply oil path P1, the OCV 203 has two discharge oil paths P2 and P3 for returning hydraulic oil to the oil pan 202, and the variable valve timing. A retard oil passage P4 that communicates with the retard hydraulic chamber 105 of the mechanism 100 and an advance oil passage P5 that communicates with the advance hydraulic chamber 106 are connected. The OCV 203 includes a spool 204 that is slidably disposed, a coil spring 205 that biases the spool 204, and an electromagnetic solenoid (not shown) that attracts the spool 204 in the arrow β direction when a voltage is applied. To do.

  The voltage applied to the electromagnetic solenoid is duty-controlled by the ECU 50. The attractive force generated by the electromagnetic solenoid changes according to the duty ratio of the applied voltage. The position of the spool 204 is determined by the balance between the attractive force generated by the electromagnetic solenoid and the urging force of the coil spring 205.

  As the spool 204 moves, the amount of communication between the retard oil passage P4 and the advance oil passage P5 and the supply oil passage P1 and the discharge oil passages P2 and P3 changes, and the retard oil passage P4 and the advance oil are changed. The amount of hydraulic oil supplied to the path P5 or the amount of hydraulic oil discharged from the oil paths P4 and P5 changes. Thus, the ECU 50 adjusts the hydraulic pressure in the retard hydraulic chamber 105 and the advance hydraulic chamber 106 in this manner, so that the relative movement of the internal rotor 101 and the housing 102 and the operating state of the retard position lock pin 121 are determined. Are also controlled.

  On the other hand, part of the hydraulic oil sucked by the oil pump 201 is supplied to the oil switching valve (OSV) 250 through the oil passage P6 branched from the supply oil passage P1. Like the OCV 203, the OSV 250 has a built-in spool (not shown) that reciprocates by the cooperation of an electromagnetic solenoid (not shown) and a coil spring (not shown), and the supply voltage to the electromagnetic solenoid is duty-controlled by the ECU 50. It is a three-port valve whose opening degree is controlled by. In addition to the oil path P6, the OSV 250 includes a discharge oil path P7 that returns the working oil to the oil pan 202, and a lock that communicates with a predetermined portion in the recess 104 in which the vane 101a including the intermediate position lock pin 131 is accommodated. A pin control oil path P8 is connected. The ECU 50 controls the operation state of the intermediate position lock pin 131 by adjusting the hydraulic pressure of the hydraulic oil supplied through the lock pin control oil passage P8, as in the OCV 203.

  Here, the structure and function of the retard position lock pin 121 and the intermediate position lock pin 131 will be described in detail.

  As schematically shown in FIG. 3A, the retard position lock pin 121 is a valve of the intake valve 36 that is determined by the relative phases of the internal rotor 101 (intake camshaft 37) and the housing 102 (intake cam sprocket 38). The relative phase between the internal rotor 101 and the housing 102 is fixed when the timing (hereinafter simply referred to as valve timing) is most retarded. Note that the relative phase of the rotating parts 101 and 102 at this time is hereinafter referred to as “most retarded angle position”.

  On the other hand, as schematically shown in FIG. 3B, the intermediate position lock pin 131 has a valve timing determined by the relative phase of the internal rotor 101 (intake camshaft 37) and the housing 102 (intake cam sprocket 38). At the intermediate state within the variable range, the relative phase between the internal rotor 101 and the housing 102 is fixed. The valve timing corresponding to this relative phase is hereinafter referred to as “interval valve timing”.

  4 (a) and 4 (b) show a cross-sectional structure of the retard position lock pin 121 and its peripheral portion when the relative phase between the internal rotor 101 and the housing 102 is at the most retarded position, that is, FIG. A sectional structure taken along line IV-IV of the variable valve timing mechanism 100 in the state of a) is shown. FIG. 4A shows a state in which no hydraulic pressure is applied to the hydraulic chambers 105 and 106. FIG. 4B shows a state in which hydraulic oil is supplied through the oil passages P4 and P5 (see also FIG. 2) and a predetermined hydraulic pressure is applied to the hydraulic chambers 105 and 106.

  As shown in FIGS. 4 (a) and 4 (b), the receiving hole 120 is formed so that the retard position lock pin 121 can reciprocate inside thereof. The housing cover 110 and the side plate 111 are integrally formed with the housing 102 by bolt fastening or the like, and sandwich the internal rotor 101 from both axial ends of the crankshaft 37.

  The side plate 111 is provided with a locking hole 111 a having a shape that engages with the tip 121 a of the lock pin 121. The locking hole 111a is opened in a direction facing the housing cover 110. Further, a spring accommodating hole 121c for accommodating the coil spring 121b is provided at the rear end portion of the retard position lock pin 121. The coil spring 121b urges the retard position lock pin 121 accommodated in the accommodation hole 120 from the housing cover 110 side toward the side plate 111 side.

  The vane 101a in which the accommodation hole 120 is formed is formed with an oil passage 101b for communicating the retard hydraulic chamber 105 and the accommodation hole 120 and an oil passage 101c for communicating the advance hydraulic chamber 106. . 4A and 4B, the advance hydraulic chamber 106 does not exist because the relative phase of the internal rotor 101 and the housing 102 is at the most retarded position.

  Here, as shown in FIG. 4A, when the hydraulic pressure is not applied to each of the hydraulic chambers 105 and 106, the distal end portion 121a of the retard position lock pin 121 is locked by the spring force of the coil spring 121b. 111a is engaged, and the relative phase of the internal rotor 101 and the housing 102 is fixed.

  On the other hand, as shown in FIG. 4B, when a sufficiently high hydraulic pressure is applied in the directions of the arrows A and B through the oil passages 101a and 101b, the hydraulic pressure overcomes the spring force of the coil spring 121b and the retard position lock pin. The tip 121a of 121 is separated from the locking hole 111a.

  The retard position lock pin 121 is when the hydraulic oil viscosity is higher than a certain reference (for example, when the temperature of the hydraulic oil is lower than a predetermined value at the start of the engine 1 or immediately after the start). Is engaged with the locking hole 111a (FIG. 4A). When the viscosity of the hydraulic oil is lower than a certain standard (when the engine 1 is in a normal operation state), the state of being separated from the locking hole 111a is maintained (FIG. 4B).

  Next, FIGS. 5A and 5B show a cross-sectional structure of the intermediate position lock pin 131 and its peripheral portion when the relative phase of the internal rotor 101 and the housing 102 is in the middle of the variable range, that is, FIG. A sectional structure taken along line VV of the variable valve timing mechanism 100 in the state 3 (b) is shown. FIG. 5A shows a state in which hydraulic oil (hydraulic pressure) is not supplied to the lock pin control oil passage P8 by the OSV 250 (see also FIG. 2). FIG. 5B shows a state in which hydraulic oil (hydraulic pressure) is supplied to the lock pin control oil passage P8 by the OSV 250 (see also FIG. 2).

As shown in FIGS. 5A and 5B, the accommodation hole 130 is formed so that the intermediate position lock pin 131 can reciprocate inside thereof. As described above, the housing cover 110 and the side plate 111 are integrally formed with the housing 102 by bolt fastening or the like, and the internal rotor 101 is clamped from both axial ends of the crankshaft 37.

  The side plate 111 is provided with a locking hole 111b having a shape that engages with the distal end portion 131a of the lock pin 131 in addition to the locking hole 111a described with reference to FIGS. 4 (a) and 4 (b). The locking hole 111 b opens in a direction facing the housing cover 110. Further, the inner part of the locking hole 111b communicates with the lock pin control oil path P8. On the other hand, a spring accommodating hole 131c for accommodating the coil spring 131b is provided at the rear end portion of the intermediate position lock pin 131. The coil spring 131b biases the intermediate position lock pin 131 accommodated in the accommodation hole 130 from the housing cover 110 side toward the side plate 111 side.

  Here, as shown in FIG. 5A, in a state where the operating oil (hydraulic pressure) is not supplied to the lock pin control oil passage P8 by the OSV 250, the spring force of the coil spring 131b causes the intermediate position lock pin 131 to move. The tip 121a engages with the locking hole 111b, and the relative phase between the internal rotor 101 and the housing 102 is fixed.

  On the other hand, as shown in FIG. 5B, when a sufficiently high hydraulic pressure is applied in the direction of the arrow C through the lock pin control oil passage P8, the hydraulic pressure overcomes the spring force of the coil spring 131b and the tip of the intermediate position lock pin 131 is reached. The part 131a is separated from the locking hole 111b.

  For example, after the engine 1 starts to start, the temperature of the hydraulic oil rises (the viscosity of the hydraulic oil decreases) and the controllability of the valve timing control is not sufficiently secured. The intermediate position lock pin 131 is locked under the condition that the valve timing is advanced from the most retarded position so that the operating state of the engine 1 can be optimized from the viewpoint of exhaust characteristics and fuel consumption. It will be engaged with the hole 111b (FIG. 5A). Incidentally, when the viscosity of the hydraulic oil is higher than this, the retard position lock pin 121 is normally engaged with the locking hole 111a. Further, when the viscosity of the hydraulic oil is lower than this, the ECU 50 controls the intermediate position lock pin 131 to be separated from the locking hole 111b by increasing the hydraulic pressure of the hydraulic oil in the oil passage P8 ( FIG. 5B).

  That is, for example, at the start of the engine 1 or immediately after the start, the valve timing is fixed at the most retarded position by the retard position lock pin 121. Thereafter, when the temperature of the hydraulic oil rises to some extent (when the viscosity of the hydraulic oil drops to some extent), the function of fixing the valve timing by the retard position lock pin 121 is released, and subsequently, the intermediate position lock pin 131 is moved to the valve. The timing is fixed at the middle position of the variable range. Further, when the temperature of the hydraulic oil rises (when the viscosity of the hydraulic oil decreases), the valve timing fixing function by the intermediate position lock pin 131 is released based on the hydraulic control of the ECU 50, and is released as long as the normal operation state continues. The state will be maintained.

  Next, the operation control of the variable valve timing mechanism 100 will be described.

The ECU 50 sequentially updates / calculates a target value (hereinafter referred to as “target valve timing”) VTT of the valve timing based on the operating state of the engine 1 grasped from the detection results of various sensors such as the crank angle sensor 55. Then, the ECU 50 determines the duty command based on the comparison between the actual valve timing (hereinafter referred to as “actual operation valve timing”) VT obtained from the output signals of the crank angle sensor 55 and the cam angle sensor 57 and the target valve timing VTT. The value DT is calculated. Further, the ECU 50 applies a command signal (voltage) having a duty ratio corresponding to the calculated duty command value DT to the electromagnetic solenoid of the OCV 203. By adjusting the opening of the OCV 203 in this way, the hydraulic pressure in each of the hydraulic chambers 105 and 106 of the variable valve timing mechanism 100 is appropriately adjusted, and the mechanism 100 is operated. In the above-described manner, the ECU 50 controls the operation of the variable valve timing mechanism 100, and thereby changes and controls the valve timing of the intake valve 36.

  Further, the valve timing control includes holding control and learning control for the holding control in addition to normal feedback control performed so that the actual operation valve timing VT converges to the target valve timing. The holding control is a control for setting a duty command value (voltage) DT for driving the OCV 203 so as to hold the valve timing at a predetermined phase to a predetermined value (holding duty). In this control, the result obtained by the holding control is evaluated, and the accurate holding duty is sequentially updated and stored.

  For example, FIG. 6A and FIG. 6B show how the actual operating valve timing VT follows the updated target valve timing VTT during execution of the valve timing control (FIG. 6A) and at this time It is an example of the time chart which shows on the same time axis the waveform WDT (FIG.6 (b)) of the duty command value DT provided to OCV203.

As shown in FIGS. 6A and 6B, when a new target valve timing VTT is set (updated) at an arbitrary time t0, the ECU 50 causes the actual operation valve timing VT to match the target valve timing VTT. The duty command value DT is changed so as to perform (feedback control is performed). Here, as the deviation (control gain) between the applied duty command value DT and the holding duty DTH is larger, the change speed when the actual operation valve timing VT approaches the target valve timing VTT (the solid line in FIG. 6A). (Equivalent to the slope) becomes larger. At this time, the ECU 50 adopts a relatively large control gain to start changing the actual operation valve timing VT, and uses the smaller control gain to drive the OCV 203 as the actual operation valve timing VT approaches the target valve timing. To do. When the actual operation valve timing VT matches the target valve timing VTT and is held in that state (for example, time t1), the ECU 50 updates the duty command value DT at this time as a new holding duty DTH.・ I will remember it.

  Hereinafter, regarding the valve timing control performed by the engine 1 of the present embodiment, the basic control procedure will be described with reference to flowcharts.

  FIG. 7 shows a “valve timing control routine” for performing the valve timing control. This routine is executed every predetermined time during the operation of the engine 1 through the ECU 50.

  When the processing shifts to the routine, first, in step S101, the ECU 50 performs information necessary for performing the valve timing control, for example, the engine speed NE, the intake air amount GA, the throttle opening degree TA, the coolant temperature THW, and the current actual operation. Grasp valve timing VT and the like.

  In step S102, the ECU 50 determines a target valve timing VTT with reference to a map (not shown) and the like based on the various parameters NE, GA, TA, THW, etc. grasped in step S101.

  The target valve timing VTT is determined in the following manner in light of the operating range (state) of the engine 1 determined from the relationship between the (engine) speed NE and the (engine) load.

For example, if the valve overlap period (the period in which both the exhaust valve 46 and the intake valve 36 are in the open state) is set to be long in a light load operation region such as during idle operation, the combustion chamber 15 will start after the combustion of the engine. Exhaust gas (inert gas component) exhausted to the exhaust port 40 tends to blow back to the intake port 30 via the combustion chamber 15 and prevent the intake air from being introduced into the combustion chamber 15. Therefore, during light load operation such as idling operation, the valve timing is retarded (the opening timing of the intake valve 36 is delayed), thereby shortening (or eliminating) the valve overlap period and combustion of the engine 1. Stabilize the state.

  Further, in the middle load region, the valve timing is advanced (the opening timing of the intake valve 36 is advanced), thereby prolonging the valve overlap period and positively returning the exhaust gas to the intake port 30. To do. Then, the amount of the inert gas component in the air-fuel mixture introduced into the combustion chamber is increased, and the combustion temperature is lowered, so that the amount of NOx component in the exhaust gas is reduced. Furthermore, since the unburned gas in the exhaust is used again for engine combustion, the amount of HC components in the exhaust is also reduced. Hereinafter, the amount of exhaust gas blown back to the intake system (intake port 30) through the combustion chamber 15 is referred to as an internal EGR (Emission Gas Recirculation) amount.

  Further, in the high-load low-medium rotation region, the valve timing is advanced (the intake valve 36 is closed earlier) to suppress the air-fuel mixture from being blown back to the intake port 30 at the initial stage of the compression stroke.

  Further, since the operating speed of the piston 12 is high in the high load and high rotation region, if the closing timing of the intake valve 36 is too early, a sufficient amount of intake air cannot be introduced into the combustion chamber 15. For this reason, the valve timing is retarded (the valve closing timing of the intake valve 36 is delayed) so that the efficiency of charging the intake air into the combustion chamber 15 is increased.

  In step S103, a deviation DLVTT between the target valve timing VTT and the actual operation valve timing VT is calculated.

  In the subsequent step S104, it is determined whether or not the absolute value of the deviation DLVTT calculated in step S103 is greater than a predetermined value DL1. Here, if the absolute value of the deviation DLVTT exceeds a predetermined value, the ECU 50 determines that the target valve timing VTT and the actual operation valve timing VT are not sufficiently approximated, and FIGS. ), The duty command value DT is appropriately changed according to the control mode before time t1, and the actual operation valve timing VT is converged to the target valve timing VTT (step S105). On the other hand, if the absolute value of the deviation DLVTT exceeds a predetermined value, it is determined that the target valve timing VTT and the actual operation valve timing VT are sufficiently approximated, and the time in FIGS. 6 (a) and 6 (b) above. In accordance with the control mode after t1, processing for maintaining the current actual operation valve timing VT (update of the holding duty DTH) is performed (step S106).

  After finishing the process in step S105 or S106, the ECU 50 once exits this routine.

  The ECU 50 basically repeats the above processing procedure at a predetermined cycle unless the retard position lock pin 121 and the intermediate position lock pin 131 are engaged with the locking holes 111a and 111b. . That is, the ECU 50 continuously performs feedback control so that the actual operation valve timing VT maintains the optimum value (target valve timing VTT) obtained in light of the operating state of the engine 1.

  By the way, when the engine 1 is operated under normal conditions, the intermediate position lock pin 131 can be used even when the relative phase between the internal rotor 101 and the housing 102 is in the arrangement state shown in FIG. As described above, it is held in the accommodation hole 130 of the vane 101a by the hydraulic action.

  However, for example, when the engine rotation NE is reduced under a condition where the hydraulic oil is at a high temperature, that is, under a condition where the viscosity of the hydraulic oil decreases and the amount of leakage increases, the operation supplied through the lock pin control oil path P8. The oil hydraulic pressure may not support the intermediate position lock pin 131, and the lock pin 131 may protrude from the accommodation hole 130 toward the locking hole 111b. Further, the hydraulic pressure of the hydraulic oil may pulsate due to fluctuations in the engine speed NE, and the intermediate position lock pin 131 in the accommodation hole 130 may vibrate. In either case, the intermediate position lock pin 131 is caught in the locking hole 111b. Under such conditions, when the housing hole 130 and the locking hole 111b are arranged to communicate with each other, the tip 131a of the intermediate position lock pin 131 in the housing hole 130 is caught by the locking hole 111b, and the actual operation with respect to the target valve timing VTT is performed. There is a problem that the followability of the valve timing VT is lowered or a step is generated in the movement, that is, a malfunction of the valve timing variable mechanism 100 occurs.

  For example, FIGS. 8A to 8D show the transition modes of the actual operating valve timing VT observed when a request for increasing the internal EGR occurs in the engine 1 (FIGS. 8A and 8B). ), The transition mode of the internal EGR (FIG. 8C), and the transition mode of the amount of NOx discharged to the exhaust passage of the engine 1 (NOx generation amount) (FIG. 8D) on the same time axis. It is a time chart illustrated to. Note that the transition mode of the internal EGR shown in FIG. 8 (c) and the transition mode of the NOx generation amount shown in FIG. 8 (d) are both the transition mode of the actual operating valve timing VT shown in FIG. 8 (b). Corresponding.

  First, FIG. 8A shows the case where the intermediate position lock pin 131 does not malfunction (hook) and the change in the actual valve timing VT quickly follows the change in the target valve timing VTT. Shows the transition of both parameters VVT and VT.

  In FIG. 8A, when a request to increase the internal EGR occurs at time t10, the target valve timing VVT that has been set to a constant value so far shifts to the advance side. When feedback control (see FIG. 6) for making the actual operation valve timing VT coincide with the target valve timing VTT is suitably performed, the movement of the actual operation valve timing VT immediately follows the movement of the target valve timing VTT. To do. For this reason, when viewed macroscopically, the transition modes of the two parameters VT and VVT observed on the time axis are substantially the same.

  On the other hand, FIG. 8B shows that the intermediate position lock pin 131 is engaged with the engagement hole while the actual operation valve timing VT shifts to the advance side (advance control is performed) following the movement of the target valve timing VTT. A transition mode of the two parameters VT and VTT observed when caught by 111b is shown.

  As shown in FIG. 8B, if the intermediate position lock pin 131 is caught in the locking hole 111b during the transition of the actual operation valve timing VT to the advance side (time t11), the actual operation valve timing VT. (Solid line) cannot follow the movement of target valve timing VTT (dashed line), and both parameters VT and VTT deviate during a predetermined period (time t11 to t13).

  As shown in FIG. 8C, the internal EGR changes in a substantially similar manner according to the change in the actual operation valve timing VT. For this reason, when the above divergence occurs between the actual operation valve timing VT and the target valve timing VTT, between the actual internal EGR (solid line) and the control internal EGR (one-dot chain line). The same divergence occurs.

  As a result, as shown in FIG. 8 (d), the amount of NOx generated despite the control that suppresses the generation of NOx by increasing the internal EGR of the engine 1 through the adjustment of the valve timing. Will temporarily increase.

  In the valve timing control apparatus according to the present embodiment, when the actual operation valve timing VT is changed, the intermediate position lock pin 131 malfunctions during the change process, and the actual operation valve timing VT moves differently from the target valve timing VT. In such a case, the deviation between the two parameters VT and VTT is quantitatively recognized. Then, the disturbance of the operating state of the engine 1 caused by such a difference between the two parameters VT and VTT (for example, the difference between the internal EGR movement scheduled for control and the actual internal EGR movement). ) Is corrected by correcting other control parameters (for example, fuel injection amount) relating to engine operation of the engine 1.

  FIG. 9 shows a “fuel injection amount correction routine” for correcting the fuel injection amount to the engine 1 by the fuel injection valve 18. This routine is executed at predetermined intervals during the operation of the engine 1 through the ECU 50, as in the previous “valve timing control routine”. Through this routine, the ECU 50 performs control corresponding to the processing content while sequentially referring to the processing content of the “valve timing control routine”.

  When the process proceeds to this routine, the ECU 50 first determines in step S111 whether the advance angle control based on the request for increasing the internal EGR is currently performed from the latest information on the “valve timing control routine”. If the determination is affirmative, the process proceeds to step S112. If the determination is negative, the routine is temporarily exited.

  In step S113, while the actual operation valve timing VT is shifted to the advance side toward the target valve timing VVT (during the advance angle control), the intermediate position lock pin 131 malfunctions and the locking hole 111b. It is determined whether or not it has been caught. Such a determination regarding the malfunction of the intermediate position lock pin 131 may be made based on, for example, the magnitude of the difference between the target valve timing VTT and the actual operation valve timing VT and the expansion speed (see FIG. 8B). For example, when a phenomenon in which a deviation between the target valve timing VTT and the actual operation valve timing VT is enlarged at a speed exceeding a predetermined value is observed during the advance angle control, the intermediate position lock pin 131 malfunctions (hangs). What is necessary is just to judge that has occurred. Even if the intermediate position lock pin 131 is not caught, the followability of the actual valve timing VT with respect to the target valve timing VTT depends on the operating state of the engine 1 (for example, the viscosity of the hydraulic oil or the engine speed NE). Usually (see FIG. 6) is different. For this reason, when determining whether or not the intermediate position lock pin 131 is caught, it is preferable to consider the difference in the followability of the actual operation valve timing VT with respect to the target valve timing VTT. If it is determined in step S113 that the intermediate position lock pin 131 is caught, the ECU 50 proceeds to step S113. On the other hand, when it is determined that the intermediate position lock pin 131 is not caught, this routine is temporarily exited.

  In step S113, an increase in the internal EGR amount that was originally planned to reduce the NOx amount in the exhaust gas and an element that has an equivalent effect (NOx reduction effect) on the exhaust characteristics are reflected in the fuel injection control described above. To do.

Specifically, for example, a shortage of the internal EGR amount due to the hooking of the intermediate position lock pin 131 (the actual internal EGR (solid line) in FIG. 8C and the internal EGR (one-dot chain line) which is a control target) A correction amount corresponding to the difference between the two is set in advance and added to the fuel injection amount to the engine 1 by the fuel injection valve 18. The shortage of the internal EGR amount is, for example, the behavior of the actual valve timing VT in FIG. 8B and the behavior of the target valve timing VVT (
Alternatively, calculation (estimation) may be performed based on a difference from the actual operation valve timing VT behavior estimated when it is assumed that no malfunction of the intermediate position lock pin 131 has occurred.

  Incidentally, as the air-fuel ratio of the combustion gas becomes lower, the combustion temperature of the engine 1 tends to decrease and the amount of NOx generated tends to be suppressed. As the shortage of the EGR amount (difference between the target value and the actual value) increases, the (positive) correction amount added to the fuel injection amount is set larger.

  After step S113, the ECU 50 once exits this routine.

  As described above, in the valve timing control device of the present embodiment, the feedback control for shifting the actual operation valve timing VT to the target valve timing VTT that is appropriately updated according to the operating state of the engine 1, and the valve timing as the current phase. The internal control caused by the malfunction of the intermediate position lock pin 131 when performing the control (advance control) to advance the actual operation valve timing VT in response to a request for increasing the internal EGR amount. An insufficient amount of EGR is calculated quantitatively, and the fuel injection amount to the engine 1 is corrected based on the calculation result.

  Here, in the valve timing control device including the intermediate position lock pin 131 as described above, if the intermediate position lock pin 131 malfunctions (hangs) during execution of the valve timing control, the reliability of the control is impaired. In addition to the above, other operation control performed based on the target valve timing VTT in the valve timing control is also affected, and as a result, the exhaust characteristics and the drivability are deteriorated. As described in the related art.

  In this regard, according to the valve timing control device according to the present embodiment, the shortage of the internal EGR amount caused by the malfunction of the intermediate position lock pin 131 is successively canceled based on other operation control. Therefore, during the execution of the valve timing control to suppress the amount of NOx generated in the exhaust, the intermediate position lock pin 131 malfunctions and the movement that the actual operation valve timing VT is scheduled for control is. Even when different movements are made, the NOx generation amount in the exhaust gas shows a transition indicated by a one-dot chain line in FIG. That is, it is preferably suppressed as planned in the control.

  Therefore, the exhaust characteristic of the engine 1 is maintained in a suitable state.

  In the “fuel injection amount correction routine”, the fuel injection amount to the engine 1 through the fuel injection valve 18 is corrected in order to eliminate the shortage of the internal EGR amount due to the malfunction of the intermediate position lock pin 131. It was decided. Further, even if a control mode for correcting the air-fuel ratio of the combustion gas by correcting the opening degree of the throttle valve 34, for example, is applied instead of the control mode for correcting the fuel injection amount, the effect equivalent to the present embodiment is obtained. I can.

  Further, even if a control mode for correcting (retarding) the ignition timing of the engine 1 is applied instead of the control mode for eliminating the shortage of the internal EGR through correction of the air-fuel ratio, the combustion temperature of the engine 1 is reduced, The amount of NOx generated can be suppressed. That is, an effect equivalent to or equivalent to the present embodiment can be achieved.

  Furthermore, a well-known exhaust gas recirculation (EGR) device that includes a gas passage that bypasses the intake system and the exhaust system of the engine 1 and a control valve that can control the opening and closing of the gas passage is applied. An amount of exhaust that compensates for the shortage of the internal EGR amount may be recirculated from the intake system.

  In the present embodiment, as described with reference to FIG. 8, when performing control (advance control) to advance the actual operating valve timing VT in response to a request for increasing the internal EGR amount, the intermediate position lock pin 131 is used. In order to eliminate the shortage of internal EGR caused by the malfunction of the engine, control for correcting parameters (fuel injection amount, etc.) relating to operation control of the engine 1 is performed. Not limited to this, when performing control (retarding control) for retarding the actual operating valve timing VT, problems relating to the operating state (exhaust characteristics and output characteristics) of the engine 1 caused by malfunction of the intermediate position lock pin 131 are eliminated. Therefore, it is possible to perform control for correcting a parameter (fuel injection amount or the like) related to operation control of the engine 1.

  Further, not only the valve timing control related to the adjustment of the internal EGR amount, but the advance angle of the actual operation valve timing VT performed to optimize other parameters relating to the operating state of the engine 1, such as engine torque, engine output, or knocking suppression, for example. For the malfunction caused by the malfunction of the intermediate position lock pin 131 that occurs during the execution of the control or the retard angle control, the control structure substantially similar to the “valve timing control routine” and the “fuel injection amount correction routine” is applied. This can be solved. In this case, not only the exhaust characteristics of the engine 1 but also the output characteristics and drivability can be stabilized.

(Second Embodiment)
Next, a second embodiment embodying the present invention will be described focusing on differences from the first embodiment. The device according to the present embodiment is a valve timing control device provided in an in-vehicle engine as in the first embodiment.

  Even in the apparatus according to the second embodiment, the configuration of the vehicle-mounted engine 1 including the variable valve timing mechanism 100 and the ECU 50, that is, the hardware configuration to be applied is basically the same as the apparatus according to the first embodiment. It is. For this reason, the duplicate description here about those structures is omitted.

  The valve timing control apparatus according to the present embodiment basically performs feedback control of valve timing according to the same control structure (see FIG. 7) as the valve timing control routine applied in the first embodiment. On the other hand, execution of holding control is prohibited under specific conditions.

  Hereinafter, regarding the valve timing control performed by the engine 1 of the present embodiment, the basic control procedure will be described with reference to flowcharts.

  FIG. 10 shows a “valve timing control routine” for performing the valve timing control. This routine is executed every predetermined time during the operation of the engine 1 through the ECU 50. Note that the processing performed in steps S101, S102, S103, S104, S105, and S106 of this routine is equivalent to the processing in each step described in the valve timing control routine (FIG. 7) in the first embodiment. Because of this, redundant explanation here is omitted.

  In this routine (FIG. 10), after the target valve timing VTT is determined (step S102), the ECU 50 proceeds to step S121.

In step S121, it is determined whether or not the current actual operation valve timing VT is within a predetermined range. The predetermined range here is, for example, an actual position corresponding to the state where the intermediate position lock pin 131 is disposed in the position shown in FIG. 11A and the state shown in FIG. The operating valve timing VT may be set as an end point. If the determination in step S121 is affirmative, execution of control (holding control) that maintains the current actual valve timing VT at the current value is prohibited (step S122), and the target valve timing VVT is at least outside the above range. Correct (reset) to. On the other hand, if the determination in step S121 is negative, execution of holding control is permitted.

  After either step S123 or S124, the ECU 50 shifts the process to step S103, and the same processing procedure as the “valve timing control routine” (FIG. 7) described in the first embodiment. In accordance with the control, the advance control or retard control (step S105) or the holding control (step S106) of the actual operation valve timing VT is performed. However, if execution of the holding control is prohibited in this routine (step S122), even if the process proceeds to step S106, the routine is temporarily exited without holding control.

  The ECU 50 continuously changes and holds the actual operation valve timing VT during the operation of the engine 1 based on the above processing procedure.

  Generally, when the holding control is executed, the actual operation valve timing VT stays in the vicinity of the current phase. For this reason, when the holding control is performed even though the actual operation valve timing VT is in the phase range in which the intermediate position lock pin 131 may be caught in the locking hole 111b as in the conventional control device, The malfunction of the intermediate position lock pin 131 is likely to occur when the hydraulic pressure of the hydraulic oil is reduced or the pulsation is generated as described in the embodiment.

  In this regard, according to the valve timing control device of the present embodiment, during execution of the valve timing control, the actual operation valve timing VT is maintained in the phase range in which the intermediate position lock pin 131 may be caught in the locking hole 111b. In order to prohibit, such malfunction of the intermediate position lock pin 131 is preferably avoided.

  As a control mode for prohibiting execution of holding control in a specific phase range, a method of prohibiting execution of holding control when the target valve timing VTT is in a specific phase range, or a target valve timing VTT specified by a specific A method of not setting the phase range can also be applied.

  However, since the followability (responsiveness) of the actual operation valve timing VT with respect to the target valve timing VTT varies depending on the operating conditions and the like, the deviation between both parameters VT and VTT varies. That is, when the followability is very high, both parameters VT and VTT are substantially the same at each time. On the other hand, when the followability is lowered, the deviation between the two parameters VT and VTT tends to deviate. Further, under the condition that the following performance is very low, a new target valve timing VTT may be set (updated) before the actual operation valve timing VT reaches (approximates) the target valve timing VTT. This can occur many times in implementing the valve timing control.

  For example, under the condition that the followability is low and the actual operation valve timing VT is less likely to reach the target valve timing VTT, execution of the holding control is prohibited when the target valve timing VTT is in a specific phase range. Rather than applying a control structure such that the target valve timing VTT is not set to a specific phase range, when the actual operating valve timing VT shifts to the specific phase range, the actual operating valve timing VT Prohibiting holding tends to have an excellent effect in avoiding malfunction of the intermediate position lock pin 131.

On the other hand, if the target valve timing VTT is within a specific phase range, the following performance is high and the actual valve timing VT and the target valve timing VTT almost coincide with each other at each time. The application of a control mode in which the execution of control is prohibited or a control mode in which the target valve timing VTT is not set to a specific phase range prefetches the movement of the actual operation valve timing VT. The performance of avoiding malfunction of the intermediate position lock pin 131 may increase.

  Therefore, for example, in accordance with conditions set based on the temperature of the hydraulic oil, the engine load, the engine speed NE, etc., the control for prohibiting the execution of the holding control when the actual operation valve timing VT is in a specific phase range. A mode, a control mode in which execution of holding control is prohibited when the target valve timing VTT is in a specific phase range, or a control mode in which the target valve timing VTT is not set in a specific phase range is switched and applied. It is good to do.

(Third embodiment)
Next, a third embodiment embodying the present invention will be described focusing on differences from the first and second embodiments. The device according to the present embodiment is a valve timing control device that is provided in an in-vehicle engine as in the first and second embodiments.

  Even in the apparatus of the third embodiment, the configuration of the vehicle-mounted engine 1 including the variable valve timing mechanism 100 and the ECU 50, that is, the hardware configuration to be applied is the same as that of the apparatuses of the first and second embodiments. Are equivalent. For this reason, the duplicate description here about those structures is omitted.

  The valve timing control apparatus according to this embodiment performs feedback control of valve timing according to the same control structure (see FIG. 7) as the valve timing control routine applied in the first embodiment. The change speed (phase displacement speed) required for changing the operating valve timing VT (retard angle or advance angle) is accelerated under specific conditions.

  Hereinafter, the basic control procedure of the valve timing control performed by the valve timing control apparatus according to the present embodiment will be described with reference to flowcharts.

  FIG. 12 shows a “valve timing control routine” for performing the valve timing control. This routine is executed every predetermined time during the operation of the engine 1 through the ECU 50. Note that the processing performed in steps S101, S102, S103, S104, S105, and S106 of this routine is equivalent to the processing in each step described in the valve timing control routine (FIG. 7) in the first embodiment. Because of this, redundant explanation here is omitted.

  In this routine (FIG. 12), after the target valve timing VTT is determined (step S102), the ECU 50 proceeds to step S121.

  In step S131, when the actual operation valve timing VT is changed from the current phase toward the target valve timing VTT, the intermediate position lock pin 131 is moved to both the positions described in FIGS. 11 (a) and 11 (b). It is determined whether or not it passes through a range (hereinafter referred to as a malfunction occurrence region) defined with the arrangement as an end point.

  When the determination in step S132 is affirmative, the ECU 50 proceeds to step S132 and changes the waveform (control gain) of the duty command value DT to be given to the OCV 203 when changing the actual operation valve timing VT.

13 (a) and 13 (b) show the waveform WDT1 of the duty command value DT employed in normal advance angle control and the transition mode (broken line) of the actual operating valve timing VT1 corresponding to the waveform WDT1. It is an example of the time chart which shows together on the same time axis the waveform WDT2 of the duty command value DT set in step S132 and the actual operation valve timing VT2 (solid line) corresponding to the waveform WDT2.

  As shown in FIGS. 13A and 13B, in the normal advance angle control, as described in the first embodiment (FIG. 6A), the ECU 50 is relatively large. The control gain (deviation between the duty command value DT and the holding duty DTH) is adopted to start changing the actual operation valve timing VT1, and a smaller control gain is adopted as the actual operation valve timing VT1 approaches the target valve timing. Then, the OCV 203 is driven. When the actual valve timing VT (VT1) matches the target valve timing VTT and is held in that state, the ECU 50 updates and stores the duty command value DT at this time as a new holding duty DTH. .

  On the other hand, according to the process in step S132, when the ECU 50 changes the actual operation valve timing VT, if it is predicted that the arrangement of the intermediate position lock pin 131 will pass the malfunction occurrence region, the actual operation will be performed. A waveform WDT2 of the duty command value DT is set as a control gain for controlling the valve timing VT.

  Then, by changing the actual operation valve timing VT (VT2) based on the waveform WDT2 of the duty command value DT, the actual operation valve whose change speed (displacement speed) corresponds to the waveform WDT1 of the duty command value DT. This is faster than the change speed of the timing VT1. As the actual operation valve timing VT is accelerated, the speed of the intermediate position lock pin 131 passing through the malfunction occurrence region also increases. Since the malfunction of the intermediate position lock pin 131 occurs when the lock pin 131 and the locking hole 111b are mechanically engaged, by increasing the speed of the intermediate position lock pin 131 that passes through the malfunction occurrence region, The probability of occurrence is extremely low. In step S132, the waveform (control gain) WDT2 of the duty command value DT is set so as to increase the change speed (displacement speed) when the actual operation valve timing VT is changed in the same manner when the retard angle control is performed. Set.

  On the other hand, if the determination in step S131 is negative, the control gain setting is left to normal control. That is, the normal waveform WDT1 is adopted as the waveform of the duty command value DT.

  After either step S132 or S133, the ECU 50 proceeds to step S103, and the same processing procedure as the “valve timing control routine” (FIG. 7) described in the first embodiment. In accordance with the control, the advance angle control, the retard angle control (step S105), or the holding control (step S106) of the actual operation valve timing VT is performed, and this routine is temporarily exited.

  The ECU 50 continuously changes and holds the actual operation valve timing VT during the operation of the engine 1 based on the above processing procedure.

  Thus, according to the valve timing control apparatus of the present embodiment, the intermediate position lock pin 131 is accelerated by accelerating the speed of the intermediate position lock pin 131 that passes through the malfunction occurrence region during the valve timing control. Becomes difficult to be caught in the locking hole 111b. Accordingly, the accuracy and reliability of the actual operation valve timing VT is improved when the control is performed so as to match the target valve timing VTT.

Note that the waveform of the duty command value DT employed as a control gain for accelerating the change speed (displacement speed) of the actual operating valve timing VT is not limited to that shown in FIG. In accordance with the above characteristics, mechanical characteristics, etc., the optimum one for accelerating the speed of the intermediate position lock pin 131 (locking mechanism) that passes through the malfunction occurrence area (speed of changing the operating characteristics) is appropriately set. Is preferred.

  Further, the operation control of the variable valve timing mechanism 100 based on the hydraulic pressure control is not limited to the method of duty-controlling the voltage applied to the OCV 203. For example, the hydraulic pressure supplied to the variable valve timing mechanism 100 such as duty-controlling the applied current. Even if other configurations and control methods that can control the above are applied, the effect equivalent to this embodiment can be obtained.

  Further, in each of the above embodiments, the configuration in which the intermediate position lock pin 131 is provided separately from the retard position lock pin 121 is applied. However, the single lock pin has both functions (121, 131). A configuration may be applied. Specifically, a locking hole for locking the lock pin may be provided at an end point (for example, the most retarded angle position) and an intermediate position in the movable range of the lock pin.

  In each of the above embodiments, when the valve timing is changed, the intermediate position lock pin 131 accommodated in the accommodation hole 130 provided in the vane 101a appropriately protrudes toward the locking hole 111b provided in the housing 102. By doing so, the structure which applies the structure which fixes valve timing in the intermediate position of the variable range was applied. On the other hand, when changing the valve timing, the intermediate position lock pin accommodated in the accommodation hole provided in the housing appropriately protrudes toward the locking hole provided in the vane, so that the valve timing can be changed within the variable range. It is good also as applying the structure fixed in the intermediate position of.

  Furthermore, even if the device adopts any mechanism that fixes the valve timing at an intermediate position of the variable range, it is not a mechanism configured by combining the lock pin and the locking hole as described above. A control structure similar to the control structure to be applied in the form can be applied.

  The variable valve timing mechanism may be provided not on the intake camshaft side but on the exhaust camshaft side, or on both the intake camshaft and the exhaust camshaft.

  Further, in each of the above embodiments, the valve timing control device provided with a so-called vane type valve timing variable mechanism has been described. However, a valve timing variable mechanism based on another operating principle, for example, a valve provided with a helical spline type valve timing variable mechanism or the like. Even in the timing control device, the same control structure as in each of the above embodiments can be applied as long as it is a device that performs similar valve timing control based on hydraulic control.

  Further, in each of the above embodiments, the present invention is applied to a so-called valve timing control device, that is, a mechanism (valve timing variable mechanism) that changes the rotational phase of the intake camshaft (or exhaust camshaft) with respect to the rotational phase of the crankshaft of the engine. It was decided to apply. On the other hand, for example, with respect to the opening / closing operation of the intake valve or the exhaust valve, the same control structure of each of the above embodiments is also applied to a mechanism for variably adjusting the lift amount (so-called valve lift amount variable mechanism). Can do. The point is that any device that variably adjusts a parameter (intake valve or exhaust valve lift profile) that appears on the time axis as a change in operating characteristics relative to the rotational phase of the crankshaft. If a mechanism for fixing at an intermediate position is provided, a control structure similar to that of each of the above embodiments can be applied to achieve an effect equivalent to or equivalent to that of each of the above embodiments.

1 engine (internal combustion engine)
1a Cylinder block 1b Cylinder head 1c Cooling water passage 11 Cylinder 12 Piston 13 Connecting rod 14 Crankshaft 15 Combustion chamber 16 Igniter 17 Spark plug 18 Fuel injection valve 19 Timing chain 30 Intake port 31 Intake passage 32 Surge tank 33 Air cleaner box 34 Throttle valve 34a Throttle actuator 35 Accelerator pedal 36 Intake valve 37 Intake camshafts 38 and 48 Cam sprocket 40 Exhaust port 41 Exhaust passage 42 Catalyst casing 46 Exhaust valve 47 Exhaust camshaft 50 Electronic control unit (ECU)
51 Air Flow Meter 52 Throttle Position Sensor 53 Accelerator Position Sensor 54 Air-fuel Ratio Sensor 55 Crank Angle Sensor 55a Timing Rotor 55b Electromagnetic Pickup 56 Water Temperature Sensor 57 Cam Angle Sensor 57b Electromagnetic Pickup 100 Valve Timing Variable Mechanism (Valve Characteristic Variable Mechanism)
101 Inner rotor 101a Vane 101a, 101b Oil passage 101b Oil passage 101c Oil passage 101, Inner rotor 102 Housing 102a Protrusion 103 Bolt 104 Concavity 105 Retarded hydraulic chamber 106 Advance hydraulic chamber 110 Housing cover 111 Side plates 111a, 111b Locking Hole 120, 130 Through hole (accommodating hole)
121 Delay angle position lock pin 121a Tip 121b Coil spring 121c Spring accommodation hole 131 Intermediate position lock pin (constituting locking mechanism)
131a Tip 131b Coil spring 131c Spring accommodating hole 201 Oil pump 202 Oil pan 203 Oil control valve (OCV)
204 Spool 205 Coil spring 250 Oil switching valve (OSV)
P1 Supply oil path P2, P3 Drain oil path P4 Retarded oil path P5 Advance oil path P6 Oil path P7 Drain oil path P8 Lock pin control oil path

Claims (3)

A valve characteristic variable mechanism that varies an operation characteristic corresponding to the rotation operation of the output shaft with respect to at least one of the intake valve and the exhaust valve that reciprocates in conjunction with the rotation operation of the output shaft of the internal combustion engine;
For the valve whose operating characteristics are variable, an actual characteristic detecting means for detecting actual operating characteristics corresponding to the rotational operation of the output shaft;
For the valve whose operating characteristic is variable, target characteristic setting means for setting a target operating characteristic based on the operating state of the engine;
A control gain setting means for setting a control gain of the variable valve characteristic mechanism so that the actual operation characteristic matches the target operation characteristic based on the actual operation characteristic and the target operation characteristic;
When the actual operating characteristics are sufficiently approximate to the target operating characteristics, holding control means for holding the operating characteristics at that time;
A locking mechanism for locking the operating characteristics of the variable valve at an intermediate position in the variable range;
Locking mechanism control means for controlling the operating state of the locking mechanism;
In a control device for an internal combustion engine having
A control device for an internal combustion engine, comprising: holding prohibiting means for prohibiting holding of the operating characteristics when the actual operating characteristics are in a predetermined range including the intermediate position. A valve characteristic variable mechanism that varies an operation characteristic corresponding to the rotation operation of the output shaft with respect to at least one of the intake valve and the exhaust valve that reciprocates in conjunction with the rotation operation of the output shaft of the internal combustion engine;
For the valve whose operating characteristics are variable, an actual characteristic detecting means for detecting actual operating characteristics corresponding to the rotational operation of the output shaft;
For the valve whose operating characteristic is variable, target characteristic setting means for setting a target operating characteristic based on the operating state of the engine;
A control gain setting means for setting a control gain of the variable valve characteristic mechanism so that the actual operation characteristic matches the target operation characteristic based on the actual operation characteristic and the target operation characteristic;
When the actual operating characteristics are sufficiently approximate to the target operating characteristics, holding control means for holding the operating characteristics at that time;
A locking mechanism for locking the operating characteristics of the variable valve at an intermediate position in the variable range;
Locking mechanism control means for controlling the operating state of the locking mechanism;
In a control device for an internal combustion engine having
The control apparatus for an internal combustion engine, wherein the target characteristic setting means sets the target operating characteristic outside a predetermined range including the intermediate position. A valve characteristic variable mechanism that varies an operation characteristic corresponding to the rotation operation of the output shaft with respect to at least one of the intake valve and the exhaust valve that reciprocates in conjunction with the rotation operation of the output shaft of the internal combustion engine;
For the valve whose operating characteristics are variable, an actual characteristic detecting means for detecting actual operating characteristics corresponding to the rotational operation of the output shaft;
For the valve whose operating characteristic is variable, target characteristic setting means for setting a target operating characteristic based on the operating state of the engine;
A control gain setting means for setting a control gain of the variable valve characteristic mechanism so that the actual operation characteristic matches the target operation characteristic based on the actual operation characteristic and the target operation characteristic;
A locking mechanism for locking the operating characteristics of the variable valve at an intermediate position in the variable range;
Locking mechanism control means for controlling the operating state of the locking mechanism;
In a control device for an internal combustion engine having
Accelerating means for increasing the change speed of the operating characteristic when the operating characteristic of the variable valve is within a predetermined range including the intermediate position;
A control device for an internal combustion engine, comprising:

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