JP2018172967A - Control device for internal combustion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit wrong learning of an initial position of a variable valve timing mechanism.SOLUTION: A control device controls an internal combustion engine having a variable valve timing mechanism attached thereto and changing opening/closing timing of an intake valve or an exhaust valve by advancing or delaying a rotation phase of a cam shaft for driving the intake valve or the exhaust valve to a crank shaft. The control device for the internal combustion engine learns a phase difference between a crank angle signal output from a crank angle sensor attached to the crank shaft and a cam angle signal output from a cam angle sensor attached to the cam shaft while the rotation phase of the cam shaft to the crank shaft is returned to an initial position. When a phenomenon in which rotating speed of the crank shaft sharply drops is detected or a phenomenon in which sharp drop of the rotating speed of the crank shaft is expected is detected, correction mount is added to the phase difference between the crank angle signal and the cam angle signal that has been actually measured during the learning.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a control apparatus for controlling an internal combustion engine associated with a variable valve timing mechanism of a phase change type.

  In a four-stroke internal combustion engine having a plurality of cylinders, it is necessary to know which stroke each cylinder is currently in and to perform fuel injection control and ignition control. An electronic control unit that controls operation of an internal combustion engine drives a crank angle signal output from a crank angle sensor attached to a crankshaft that is an output shaft of the internal combustion engine, and an intake valve or an exhaust valve. The cam angle signal output from the cam angle sensor attached to the camshaft is received, the current stroke of each cylinder is obtained by referring to them, and the fuel injection and ignition in accordance with the stroke of each cylinder are executed. .

  The crank angle sensor senses the rotation angle of the rotor that rotates integrally with the crankshaft. The rotor is formed with teeth or protrusions at predetermined angles along the rotation direction of the crankshaft. Typically, every time the crankshaft rotates 10 °, teeth or protrusions are placed. The crank angle sensor faces the outer periphery of the rotor, detects that individual teeth or protrusions pass near the sensor, and transmits a pulse signal as a crank angle signal each time.

  However, it does not output 36 pulses during one revolution of the crankshaft. The teeth or protrusions of the crankshaft rotor are partially missing, and due to the missing teeth, the crank angle signal pulse train is also partially missing. In the illustrated example, pulses corresponding to the seventeenth, eighteenth, twentieth, twenty-first, thirty-fifth, and thirty-sixth pulses are missing. Based on this defect, it is possible to know the absolute angle of the crankshaft. If the timing of the first pulse after the missing thirty-sixth pulse is 0 ° CA (crank angle), the timing of the nineteenth pulse following the missing eighteenth pulse is 180 ° CA. become.

  The cam angle sensor senses the rotation angle of the rotor that rotates integrally with the intake camshaft or the exhaust camshaft. The rotor is formed with teeth or protrusions for each angle obtained by dividing one rotation of the camshaft by the number of cylinders. In the case of a three-cylinder engine, teeth or protrusions are arranged each time the camshaft rotates 120 °. The camshaft is rotated by receiving a rotational driving force from the crankshaft via a winding transmission mechanism or the like, and its rotational speed is one half of that of the crankshaft. Therefore, the above teeth or protrusions are arranged every 240 ° CA in terms of the crank angle. In addition, the rotor is provided with one tooth or protrusion between the teeth or protrusions every 240 ° CA for generating an additional cam angle signal. The cam angle sensor faces the outer periphery of the rotor, detects that individual teeth or protrusions pass in the vicinity of the sensor, and transmits a pulse signal as a cam angle signal each time.

  As is well known, the camshaft is supplied with a rotational driving force from the crankshaft and rotates following the crankshaft. A winding transmission for transmitting the rotational driving force is interposed between the crankshaft and the camshaft. The winding transmission device includes a crank sprocket (or pulley) provided on the crankshaft, a cam sprocket (or pulley) provided on the camshaft, and a timing chain (or timing belt) wound around these sprockets. And The phase variable type VVT mechanism changes the rotation phase of the camshaft relative to the crankshaft by rotating the camshaft relative to the cam sprocket, thereby changing the opening / closing timing of the intake valve or the exhaust valve. The cam angle signal also represents the valve timing embodied by the VVT mechanism (see the following patent document).

JP 2014-040780 A

  A timing chain for interlocking a crankshaft and a camshaft of an internal combustion engine may be extended due to deterioration over time. Further, when the timing chain is wound around the crank sprocket and the cam sprocket, the chain may not be hooked on the correct teeth of the sprocket, and the phases of the crank sprocket and the cam sprocket may deviate from the phases originally assumed. In addition, the sprocket teeth can be damaged.

  In order to realize the desired valve timing by controlling the VVT mechanism, it is necessary to know in advance the phase difference between the crank angle signal and the cam angle signal when the VVT mechanism is at the reference initial position. (Otherwise, the valve timing currently implemented by the VVT mechanism cannot be grasped). However, the phase difference between the crank angle signal and the cam angle signal when the VVT mechanism is at the initial position is not always constant due to the expansion or misalignment of the timing chain. Therefore, it is necessary to learn the phase difference while operating the internal combustion engine. Typically, during idle operation when the VVT mechanism returns to the initial position, the crank angle at which the cam angle signal is generated (the crank angle becomes clear from the crank angle signal) is measured, and the crank angle is used as a learning value. Remember.

  However, when the idle stop condition is satisfied, the above learning is performed when the rotation speed of the crankshaft sharply drops due to the fact that the idle stop is executed or the combustion of the air-fuel mixture in the cylinder becomes unstable or misfiring occurs. The error will be mixed in the learning value. Even if the rotation speed of the crankshaft suddenly drops, the camshaft continues to rotate due to inertia, and the timing chain is loosened, causing a temporary deviation between the rotation phase of the crankshaft and the rotation phase of the camshaft. It is.

  To give a specific example, the camshaft signal of the crankshaft is generated even though the cam angle signal is generated at the timing of −60 ° CA, 180 ° CA and 420 ° CA when the VVT mechanism is in the initial position. A cam angle signal may be generated at a timing of −70 ° CA, 170 ° CA, and 410 ° CA as the rotational speed rapidly drops. If learning is performed at this time, in the subsequent operation of the internal combustion engine, even if the VVT mechanism is controlled so that the valve timing is advanced by 20 ° CA from the initial position, the valve timing is actually 30 ° from the initial position. Will advance by CA. As described above, when the desired valve timing is not realized, there is a concern that the performance of the internal combustion engine is deteriorated.

  The present invention, which has been made by paying attention to the above problems for the first time, is intended to suppress erroneous learning of the initial position of the VVT mechanism.

  In the present invention, there is provided an internal combustion engine having a variable valve timing mechanism for changing an opening / closing timing of an intake valve or an exhaust valve by advancing or retarding a rotation phase of a camshaft that drives the intake valve or the exhaust valve with respect to a crankshaft. A control device for controlling a crank angle signal output from a crank angle sensor associated with the crankshaft and a cam associated with the camshaft when the rotational phase of the camshaft relative to the crankshaft is returned to the initial position This is to learn the phase difference from the cam angle signal output from the angle sensor, and when an event that the crankshaft rotation speed suddenly falls is detected, or an event that the crankshaft rotation speed is expected to fall suddenly is detected. Sometimes, the crank angle signal and cam angle signal measured during the learning To constitute a control apparatus for an internal combustion engine applying the correction amount of the phase difference.

  According to the present invention, erroneous learning of the initial position of the VVT mechanism can be appropriately suppressed.

The figure which shows schematic structure of the internal combustion engine and control apparatus in one Embodiment of this invention. The figure which shows the variable valve timing mechanism incidental to the internal combustion engine of the embodiment. The figure which shows typically the aspect of the crank angle sensor accompanying the internal combustion engine of the embodiment. The figure which shows typically the aspect of the cam angle sensor accompanying the internal combustion engine of the embodiment. The timing diagram which shows the relationship between the stroke of each cylinder of the internal combustion engine of the embodiment, a crank angle signal, and a cam angle signal.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition type 4-stroke gasoline engine, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). An injector 11 for injecting fuel toward the intake port is provided upstream of the intake valve of each cylinder 1 and in the vicinity of the intake port connected to each cylinder 1. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1.

  FIG. 2 shows an electric circuit for spark ignition. The spark plug 12 receives spark voltage generated by the ignition coil 14 and causes spark discharge between the center electrode and the ground electrode. The ignition coil 14 is integrally incorporated in a coil case together with an igniter 13 that is a semiconductor switching element.

  When the igniter 13 receives an ignition signal i from an ECU (Electronic Control Unit) 0 which is a control device for the internal combustion engine, the igniter 13 is first ignited and a current flows to the primary side of the ignition coil 14, and the ignition timing immediately thereafter Thus, the igniter 13 is extinguished and this current is cut off. Then, a self-induction action occurs, and a high voltage is generated on the primary side. Since the primary side and the secondary side share the magnetic circuit and the magnetic flux, a higher induced voltage is generated on the secondary side. This high induction voltage is applied to the center electrode of the spark plug 12, and a spark discharge occurs between the center electrode and the ground electrode.

  The ECU 0 of the present embodiment can detect an ionic current generated in the combustion chamber of the cylinder 1 during the ignition combustion of the air-fuel mixture, and can determine the combustion state with reference to this ionic current. As shown in FIG. 2, in this embodiment, a circuit for detecting an ionic current flowing through the electrode of the spark plug 12 is added to the electric circuit for spark ignition.

  An intake passage 3 for supplying intake air to the cylinder 1 takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The exhaust passage 4 for exhausting the exhaust from the cylinder 1 guides the exhaust generated by burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  The exhaust gas recirculation device 2 realizes a so-called high pressure loop EGR, and an external EGR that communicates the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3. The passage 21, an EGR cooler 22 provided on the EGR passage 21, and an EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of EGR gas flowing through the EGR passage 21 are used as elements. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined location downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, particularly to the surge tank 33.

  As shown in FIG. 2, in the internal combustion engine of the present embodiment, a timing chain 74 is wound around a crank sprocket 71, an intake-side sprocket 72, and an exhaust-side sprocket 73, and the rotational driving force provided from the crankshaft by this timing chain 74. Is transmitted to the intake camshaft via the intake side sprocket 72 and to the exhaust camshaft via the exhaust side sprocket 73.

  In addition, a VVT mechanism 6 is interposed between the intake side sprocket 72 and the intake camshaft. The VVT mechanism 6 changes the opening / closing timing of the intake valve by changing the rotational phase of the intake camshaft with respect to the crankshaft.

  The housing 61 of the VVT mechanism 6 is fixed to the intake side sprocket 72, and the intake side sprocket 72 and the housing 61 rotate integrally with the crankshaft. On the other hand, the rotor 62 fixed to one end portion of the intake camshaft is housed in the housing 61 and can rotate relative to the intake-side sprocket 72 and the housing 61. A plurality of fluid chambers into which hydraulic fluid flows in and out are formed inside the housing 61, and each fluid chamber is partitioned into an advance chamber 612 and a retard chamber 611 by a vane 621 formed on the outer peripheral portion of the rotor 62. Has been.

  The hydraulic pressure (hydraulic pressure) circuit of the VVT mechanism 6 is supplied with lubricating oil as hydraulic fluid stored in the oil pan 81 from a lubricating oil pump 82 as hydraulic fluid pump. The lubricating oil pump 82 is a hydraulic pump that operates by receiving rotational torque from a crankshaft that is an output shaft of the internal combustion engine. An OCV (Oil Control Valve) 9 that is a switching control valve is provided between the lubricating oil pump 82 and the VVT mechanism 6. By operating the flow rate and direction of the hydraulic fluid via the OCV 9, the hydraulic fluid pumped from the oil pan 81 can be selectively supplied to the advance chamber 612 or the retard chamber 611. Then, the housing 61 rotates relative to the rotor 62, and the opening / closing timing of the intake valve can be advanced or retarded.

  The ECU 0 in this embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface of the ECU 0 includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle output from a crank angle sensor (engine rotation sensor) that detects the rotation angle of the crankshaft and the engine speed. Signal b, accelerator pedal depression amount or throttle valve 32 opening as an accelerator opening (in other words, required engine load factor), a sensor that outputs an accelerator opening signal c, suggests the temperature of the internal combustion engine A cooling water temperature signal d output from a water temperature sensor for detecting the cooling water temperature, an intake air temperature / intake pressure signal output from a temperature / pressure sensor for detecting the intake air temperature and intake pressure in the intake passage 3 (particularly, the surge tank 33). e. Sensor that detects that the brake pedal is depressed or the amount of depression of the brake pedal (brake switch And the brake signal f output from the master cylinder pressure sensor, the cam angle signal g output from the cam angle sensor at a plurality of cam angles of the intake camshaft, and the combustion of the air-fuel mixture in the combustion chamber of the cylinder 1 The ion current signal h etc. output from the circuit for detecting the ion current generated by the input is input.

  Here, the crank angle signal b and the cam angle signal g will be supplemented. As shown in FIG. 3, the crank angle sensor senses the rotation angle of the rotor 75 that is fixed to the crankshaft and rotates integrally with the crankshaft. The rotor 75 is formed with teeth or projections 76 at every predetermined angle along the rotation direction of the crankshaft. Typically, each time the crankshaft rotates 10 °, a tooth or projection 76 is placed. The crank angle sensor faces the outer periphery of the rotor 75, detects that each tooth or protrusion 76 passes near the sensor, and transmits a pulse signal as the crank angle signal b each time. The ECU 0 receives this pulse as the crank angle signal b.

  However, the crank angle sensor does not output 36 pulses during one rotation of the crankshaft. The teeth or protrusions 76 of the crankshaft rotor 75 are partially missing. In the example shown in FIG. 3, the seventeenth, eighteenth, twentyth, and twentyth first missing tooth portions 761 and the thirty fifth and thirty sixth missing tooth portions 762 are roughly divided into two. There are missing tooth portions 761 and 762. The missing tooth portions 761 and 762 each correspond to a specific rotational phase angle of the crankshaft. That is, the continuous missing tooth portion 761 corresponds to 180 ° CA and 540 ° CA, and the single missing tooth portion 762 corresponds to 0 ° CA and 360 ° CA, and the position between them is about 180 ° CA. There is a phase difference.

  As shown in FIG. 5, due to the above-mentioned missing tooth portions 761 and 762, a part of the pulse train of the crank angle signal b is also lost. Based on this deficiency, it is possible to know the absolute angle (posture) of the crankshaft, in other words, the current position of the piston of each cylinder 1. If the timing of the first pulse after the missing thirty-sixth pulse is 0 ° CA (or 360 ° CA), the timing of the nineteenth pulse following the missing eighteenth pulse is 180 °. That is, CA (or 540 ° CA). The timing of the 0 ° CA pulse is substantially equal to the compression top dead center of a specific cylinder (second cylinder in the illustrated example) 1.

  As shown in FIG. 4, the cam angle sensor also senses the rotation angle of a rotor 77 that is fixed to the cam shaft and rotates integrally with the cam shaft. The rotor 77 is formed with teeth or protrusions 78 at every angle obtained by dividing at least one rotation of the camshaft by the number of cylinders. In the case of a three-cylinder engine, teeth or protrusions 78 are arranged every time the camshaft rotates 120 °. The camshaft is rotated by receiving a rotational driving force transmitted from the crankshaft via a winding transmission mechanism, and its rotational speed is one-half that of the crankshaft. Therefore, the above-described teeth or protrusions 78 are arranged every 240 ° CA in terms of the crank angle. In addition, in the present embodiment, the rotor 77 is provided with one tooth or protrusion 79 for generating an additional cam angle signal g between the teeth or protrusions 78 every 240 ° CA.

  The cam angle sensor faces the outer periphery of the rotor 77, detects that individual teeth or protrusions 78 and 79 pass in the vicinity of the sensor, and transmits a pulse signal as the cam angle signal g each time. The ECU 0 receives this pulse as the cam angle signal g. The basic cam angle signal g generated due to the teeth or protrusions 78 indicates that one of the cylinders 1 has reached a predetermined stroke. As shown in FIG. 5, the basic cam angle signal g output from the cam angle sensor attached to the intake camshaft is a crank angle (specifically 60 ° CA) advance from the compression top dead center in each cylinder 1. Suggest the timing. The basic cam angle signal g also represents the intake valve timing (the advance amount) adjusted by the VVT mechanism 6. By referring to both the crank angle signal b and the cam angle signal g, in addition to being able to determine and know the current stroke of each cylinder 1, the current intake valve timing embodied by the VVT mechanism 6 becomes clear. .

  The additional cam angle signal g generated due to the teeth or protrusions 79 corresponds to a specific rotational phase angle of the camshaft and assists in determining the stroke of each cylinder 1. In the example shown in FIG. 5, a predetermined crank angle (specifically, 60 ° CA) is obtained from a pulse of the basic cam angle signal g indicating a timing at which a crank angle is advanced from the compression top dead center of the third cylinder 1. There is a pulse of the additional cam angle signal g at the retarded timing. When these two cam angle signal g pulses are successively received at a predetermined (60 ° CA) interval that is apparent from the pulse train of the crank angle signal b, the compression top dead of the third cylinder 1 is received together with the latter pulse. You can see that the dots are coming.

  From the output interface of the ECU 0, an ignition signal i for the igniter 13 of the spark ignition device, a fuel injection signal j for the injector 11, an opening operation signal k for the throttle valve 32, and an opening degree for the EGR valve 23. The control signal l and the control signal m are output to the OCV 9 for driving the VVT mechanism 6.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed, the intake air amount, etc., the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR rate) Volume), opening / closing timing of the intake valve, and the like. The ECU 0 applies various control signals i, j, k, l and m corresponding to the operation parameters via the output interface.

  Further, the ECU 0 executes an idle stop that stops the idle rotation of the internal combustion engine when a predetermined idle stop condition is satisfied. The ECU 0 indicates that the brake pedal depression amount or the master cylinder pressure is equal to or greater than a threshold value (the brake pedal is depressed), the cooling water temperature of the internal combustion engine is higher than a predetermined value, and the charge amount or terminal voltage of the in-vehicle battery exceeds a predetermined value. High, the shift range is the driving range, the absolute value of the slope of the road where the vehicle is located is less than the predetermined value, and the negative pressure stored in the brake booster (differential pressure between atmospheric pressure and brake booster negative pressure) The size is greater than or equal to a threshold, the vehicle has a history of acceleration up to a certain vehicle speed (eg, 10 km / h) since the end of the previous idle stop, and the current vehicle speed is less than a certain vehicle speed (eg, 9 km / h), etc. It is determined that the idle stop condition is satisfied when all the above conditions are satisfied.

  When a predetermined idle stop end condition is satisfied after the idle stop condition is satisfied, the internal combustion engine is restarted. The ECU 0 determines that the brake pedal depression amount or the master cylinder pressure is 0 or less than a threshold value close to 0 (the brake pedal is no longer depressed), and conversely, the brake pedal depression amount or the master cylinder pressure further increases (brake The pedal is depressed more strongly), the accelerator opening is increased (the accelerator pedal is depressed), the negative pressure stored in the brake booster is reduced below the threshold value, and the engine is stopped for a predetermined time (3 It is determined that the condition for ending the idle stop has been satisfied by any one of the following.

  When starting the stopped internal combustion engine (including not only returning from an idling stop but also cold starting), the ECU 0 inputs a control signal o to an electric motor (starter or ISG (Integrated Starter Generator), not shown). Then, cranking is performed by rotating the crankshaft by the electric motor. Cranking is considered when the internal combustion engine has gone from the first explosion to the consecutive explosion and the engine speed, that is, the rotation speed of the crankshaft, exceeds the complete explosion judgment value determined according to the cooling water temperature, etc. )finish.

  Therefore, the ECU 0 of the present embodiment has a maximum volume of the retard chamber 611 when the rotor 62 of the VVT mechanism 6 takes the initial position in order to appropriately control the opening / closing timing of the intake valve via the VVT mechanism 6. The phase difference between the crank angle signal b and the cam angle signal g when the vane 621 transitions to a position where the volume of the advance chamber 612 is minimized and the opening / closing timing of the intake valve reaches the most retarded time is determined appropriately. To learn.

  When the rotor 62 of the VVT mechanism 6 assumes the initial position, the intake valve of each cylinder 1 opens at a timing near the exhaust top dead center and closes when a certain crank angle has elapsed after the intake bottom dead center. It becomes a state to speak. In addition, the ECU 0 responds to the operating region of the internal combustion engine [engine speed, engine load factor (or intake pressure in the surge tank 33, intake (fresh air) amount or fuel injection amount filled in the cylinder 1)]. Thus, the rotor 62 and its vane 621 are rotated relative to the housing 61 so that the volume of the retard chamber 611 is reduced and the volume of the advance chamber 612 is increased, whereby the intake air embodied by the VVT mechanism 6 is realized. Advance the valve timing from the initial position. The amount of advancement of the current intake valve timing, in other words, the amount of rotation of the rotor 62 from the initial position can be determined by matching the crank angle signal b and the cam angle signal g. For this purpose, the VVT mechanism It is necessary to know in advance the phase difference between the crank angle signal b and the cam angle signal g when the sixth rotor 62 is in the initial position.

  Learning of the phase difference between the crank angle signal b and the cam angle signal g when the VVT mechanism 6 is in the initial position is performed during an operation region where the intake valve timing is most retarded, typically during idling of the internal combustion engine. That is, during idle operation, it is measured how many times the pulse of the cam angle signal g is generated at the crank angle based on the pulse train of the crank angle signal b, and the value of the crank angle is stored in the memory of the ECU 0. Hold. Describing in accordance with the example shown in FIG. 5, the original normal cam angle signal g when the VVT mechanism 6 is in the initial position is −60 ° CA, 180 ° CA, 240 ° CA, and 420 ° CA. Occur. The ECU 0 stores the crank angle value as a learning value.

  However, when the idling stop condition is established, the learning is performed when the rotational speed of the crankshaft drops sharply due to the idling stop being executed, the combustion of the air-fuel mixture in the cylinder 1 becoming unstable or misfiring, or the like. If it is performed, an error is mixed in the learning value. Even if the rotation speed of the crankshaft suddenly drops, the camshaft continues to rotate due to inertia, and there is a temporary deviation between the rotation phase of the crankshaft and the rotation phase of the camshaft as the timing chain 74 is loosened. Responsible.

  Referring to the example shown in FIG. 5, the cam angle signal g is originally at the timing of −60 ° CA, 180 ° CA, 240 ° CA, and 420 ° CA with the VVT mechanism 6 in the initial position. Should occur. Nevertheless, the cam angle signal g is generated at timings of −70 ° CA, 170 ° CA, 230 ° CA, and 410 ° CA, for example, with a sudden drop in the rotational speed of the crankshaft. If learning is performed at this time, −70 ° CA, 170 ° CA, 230 ° CA, and 410 ° CA are stored as learning values, that is, an error of 10 ° CA from the original initial position occurs. Due to the error, in the subsequent operation of the internal combustion engine, even if the VVT mechanism 6 is controlled so that the intake valve timing is advanced by, for example, 20 ° CA from the initial position, the intake valve timing is actually the initial position. Will advance by 30 ° CA. As described above, when the desired valve timing is not realized, there is a concern that the performance of the internal combustion engine is deteriorated.

  In order to avoid the above problem, the ECU 0 according to the present embodiment detects the event that the crankshaft rotational speed suddenly drops or detects the event that the crankshaft rotational speed is expected to fall sharply. A correction amount is added to the value of the phase difference between the crank angle signal b and the cam angle signal g actually measured in learning.

  The ECU 0 constantly monitors the rotational speed of the crankshaft of the internal combustion engine with reference to the crank angle signal b. Specifically, based on the pulse train of the crank angle signal b, the time required for the crankshaft to rotate at a predetermined crank angle, typically 30 ° CA, is repeatedly measured, and the required time measured this time By subtracting the required time measured last time, the amount of change in the required time of 30 ° CA, which is an indicator of the amount of decrease in the rotation speed every 30 ° CA, is obtained. A positive change in the required time of 30 ° CA means that the rotational speed of the internal combustion engine tends to decelerate, and a negative value means that the rotational speed of the internal combustion engine tends to accelerate. To do. When the amount of change in the required time of 30 ° CA is a positive value and is greater than a predetermined value, the ECU 0 determines that an event has occurred in which the rotational speed of the crankshaft has dropped sharply. The cause of the sudden drop in the rotational speed of the crankshaft can be the start of the idle stop, the unstable combustion of the air-fuel mixture in the cylinder 1, or misfiring.

  It is also possible to determine whether misfire has occurred in the cylinder 1 with reference to the ion current signal h flowing through the electrode of the spark plug 12 during the expansion stroke. The ECU 0 measures the length of the period during which the magnitude of the ion current signal h detected during the expansion stroke of the cylinder 1 exceeds the threshold, and when the length of the period is less than a predetermined value, It is determined that the combustion of the air-fuel mixture is unstable or misfire occurs in the expansion stroke of 1. In this case, the rotation of the crankshaft is not accelerated during the expansion stroke, and as a result, the rotation speed of the crankshaft may drop sharply. In short, the fact that the length of the period during which the magnitude of the ion current signal h exceeds the threshold value is less than the predetermined value corresponds to an event where a sudden drop in the rotational speed of the crankshaft is expected.

  Alternatively, it is conceivable to predict a sudden drop in the rotational speed of the crankshaft from the output of the air-fuel ratio sensor that detects the air-fuel ratio of the exhaust gas flowing into the catalyst 41, which is installed in the exhaust passage 4 of the internal combustion engine. If the air-fuel ratio of the air-fuel mixture is excessively lean or conversely excessively rich, the combustion of the air-fuel mixture in the cylinder 1 becomes unstable and the possibility of misfire increases. Therefore, the ECU 0 predicts a sudden drop in the rotational speed of the crankshaft when the air-fuel ratio of the gas detected via the air-fuel ratio sensor is lean above a predetermined value or excessively rich below a predetermined value. It is determined that the event to be performed has occurred.

  In the state where the VVT mechanism 6 is in the initial position, when the phase difference between the crank angle signal b and the cam angle signal g is learned, the crankshaft rotation speed as described above, When detecting an event where a sudden decrease in the rotational speed is detected, the ECU 0 does not learn the phase difference between the crank angle signal b and the cam angle signal g. Alternatively, a value obtained by adding a necessary correction amount to the phase difference between the crank angle signal b and the cam angle signal g actually measured at the learning opportunity is stored and held in the memory as a learning value. That is, in the specific example shown with FIG. 5, when values of −70 ° CA, 170 ° CA, 230 ° CA and 410 ° CA are obtained as the phase difference between the crank angle signal b and the cam angle signal g, Values of −60 ° CA, 180 ° CA, 240 ° CA, and 420 ° CA obtained by adding 10 ° CA or a correction amount close to this to the actually measured value are stored as learning values. The correction amount may be a constant value that does not depend on the amount of change in the rotational speed of the crankshaft, the amount of decrease in rotational speed per unit time when the rotational speed of the crankshaft suddenly drops, or a predetermined crank angle (particularly 30 It is good also as a value which increases / decreases according to the fall amount of the rotational speed for every degree (CA). In the latter case, the correction amount is set to be larger as the amount of decrease in the rotational speed of the crankshaft is larger.

  In the present embodiment, a control device for controlling an internal combustion engine associated with a variable valve timing mechanism 6 that changes the opening / closing timing of the intake valve by advancing or retarding the rotational phase of the camshaft that drives the intake valve with respect to the crankshaft. The crank angle signal b output from the crank angle sensor associated with the crankshaft and the cam angle sensor associated with the camshaft when the rotational phase of the camshaft with respect to the crankshaft is returned to the initial position. Is used to learn the phase difference from the cam angle signal g output from the camshaft, and when an event in which the crankshaft rotational speed suddenly falls is detected or an event in which the crankshaft rotational speed is expected to fall sharply is detected In addition, the phase difference between the crank angle signal b and the cam angle signal g actually measured during the learning is corrected. To constitute a control apparatus 0 for an internal combustion engine is added.

  According to the present embodiment, it is possible to avoid erroneous learning of the phase difference between the crank angle signal b and the cam angle signal g when the VVT mechanism 6 is in the initial position, and the performance of the internal combustion engine is degraded due to the erroneous learning. Can be prevented. In particular, in a port injection type internal combustion engine, the timing at which fuel is injected from the injector 11 depends on the opening / closing timing of an intake valve implemented by the VVT mechanism 6. If the ECU 0 cannot correctly grasp the intake valve timing that is currently implemented by the VVT mechanism 6, the fuel injection timing from the injector 11 will not be optimal, and a necessary and sufficient amount of fuel will not be drawn into the cylinder 1. As a result, the air-fuel ratio of the air-fuel mixture filled in the cylinder 1 may deviate from the target air-fuel ratio, leading to unstable combustion, a decrease in engine torque and engine speed, and a deterioration in emissions. According to the present embodiment, the risk that the ECU 0 erroneously recognizes the intake valve timing implemented by the VVT mechanism 6 is reduced, the combustion is stabilized, the engine torque and the engine speed are prevented from being lowered, and the emission is deteriorated. Contribute to deterrence.

  The present invention is not limited to the embodiment described in detail above. For example, the specific mode of the VVT mechanism is not limited to a hydraulic type (vane type) that rotates the vane with the hydraulic pressure. The present invention can also be applied to a motor drive VVT in which the rotational phase of the camshaft relative to the crankshaft is advanced / retarded by an electric motor.

  Although the exhaust VVT mechanism for variably controlling the opening / closing timing of the exhaust valve is not mounted on the internal combustion engine of the above embodiment, an exhaust VVT mechanism similar to the intake VVT mechanism may be attached to the internal combustion engine. . In that case, it is naturally possible to apply the present invention to learning of the phase difference between the crank angle signal and the cam angle signal when the exhaust VVT mechanism is in the initial position. A cam angle sensor is attached to the exhaust camshaft that drives the exhaust valve, and the cam angle signal output from the cam angle sensor determines the rotation angle of the exhaust camshaft and the rotation of the exhaust camshaft relative to the crankshaft. It may represent the phase.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be used for controlling an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
1 ... Cylinder 6 ... Variable valve timing (VVT) mechanism b ... Crank angle signal g ... Cam angle signal

Claims (1)

A control device for controlling an internal combustion engine with a variable valve timing mechanism that changes the opening / closing timing of an intake valve or an exhaust valve by advancing or retarding the rotational phase of a camshaft that drives the intake valve or the exhaust valve with respect to the crankshaft Because
The crank angle signal output from the crank angle sensor associated with the crankshaft and the cam angle output from the cam angle sensor associated with the camshaft when the rotational phase of the camshaft with respect to the crankshaft has returned to the initial position. It learns the phase difference with the signal,
When an event in which the crankshaft rotational speed suddenly drops is detected, or an event in which the crankshaft rotational speed is expected to fall sharply is detected, the phase difference between the crank angle signal and the cam angle signal measured during the learning is calculated. A control device for an internal combustion engine that adds a correction amount.

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