Control device for internal combustion engine

Abstract

To correctly detect an abnormality such as incorrect attachment or significant elongation of a timing chain of an internal combustion engine at the time of shipment of a new product and at the time of a subsequent operation.SOLUTION: A control device for an internal combustion engine refers to a crank angle signal, which is generated each time a crankshaft of the internal combustion engine rotates by a certain angle, and a cam angle signal, which is generated each time a camshaft driven followingly to the crankshaft through a winding transmission mechanism rotates by a certain angle, and determines that an abnormality exists, on the condition that a phase difference between the generation of the crank angle signal, which indicates the timing at which an attitude of the crankshaft reaches a predetermined reference angle, and the generation of the cam angle signal exceeds a delay determination value. The control device of the internal combustion engine is configured to, in setting the delay determination value, add a correction value α, which varies according to a length of an operating period of the internal combustion engine, to a basic value.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a control device for controlling an internal combustion engine mounted on a vehicle or the like. [Background technology]

[0002] In a four-stroke internal combustion engine having multiple cylinders, a crankshaft that is connected to the pistons that move back and forth in each cylinder and serves as the output shaft of the internal combustion engine, and a camshaft equipped with cams that drive the opening and closing of the intake and exhaust valves of each cylinder are linked via a wrapping transmission mechanism. The wrapping transmission mechanism has elements such as a crank sprocket (or a toothed pulley) fixed to the crankshaft, a cam sprocket (or a toothed pulley) fixed to the camshaft, and a timing chain (or a toothed belt) that meshes with these sprockets.

[0003] When winding a timing chain around the crank sprocket and cam sprocket during the assembly process of an internal combustion engine, the chain can sometimes be misaligned (misassembled), meaning that the part of the chain that corresponds to a specific tooth on the sprocket does not engage with that tooth correctly (in other words, the tooth that should mesh with the specific part of the chain is misaligned). This causes the rotational phase of the camshaft and the rotational phase of the crankshaft to deviate from their normal relationship.

[0004] As a result, the intake valve or exhaust valve will not open or close at the correct timing, which may cause delayed or poor starting of the internal combustion engine, or unstable idling. Even if this is not the case, there is a concern that the accuracy of the control of the opening and closing timing of the intake or exhaust valve by the spark ignition timing or variable valve timing mechanism will decrease, resulting in a deterioration of the thermal efficiency of the internal combustion engine. Furthermore, the risk of the valve body of the open intake or exhaust valve coming into contact with the piston that has reached the vicinity of the top dead center cannot be completely denied. The same problem occurs when the timing chain stretches significantly due to aging.

[0005] Therefore, an electronic control unit that controls the operation of the internal combustion engine receives an output signal from a crank angle sensor attached to the crankshaft and an output signal from a cam angle sensor attached to the camshaft, obtains the rotational phase difference between the crankshaft and the camshaft based on the crank angle signal and cam angle signal, and constantly determines whether the phase difference is within an appropriate range. This makes it possible to detect abnormalities such as misalignment or stretching of the timing chain (see the following patent document). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2001-164980 A Summary of the Invention [Problem to be solved by the invention]

[0007] The ECU determines whether or not there is an abnormality based on whether the phase difference between the crank angle signal, which indicates the timing when the crankshaft position reaches a predetermined reference angle, for example 30° CA (crank angle) before top dead center of compression for each cylinder, and the corresponding cam angle signal, is within an appropriate range.

[0008] As an example, if the teeth of a sprocket are arranged at intervals of approximately 14° CA around its central axis of rotation, if the chain gets misaligned, the timing of the cam angle signal will deviate by more than 14° CA from the reference angle timing.

[0009] On the other hand, even if the chain is wrapped correctly and there is no misalignment, the timing of the cam angle signal generation may naturally deviate slightly from the timing of the reference angle due to variations within the dimensional tolerances of the components of the internal combustion engine, including the wrapping transmission mechanism, and expansion and contraction due to temperature. Therefore, a deviation of the cam angle signal from the timing of the reference angle is allowed within the appropriate range, for example, ±7° CA, and is determined to be not abnormal. Furthermore, taking into account the elongation of the chain that universally occurs as a change over time, the allowable amount of elongation is set to, for example, 5° CA, and even if the generation of the cam angle signal is delayed from the timing of the reference angle, the conventional method is to consider it to be within the appropriate range as long as the delay is within 12° CA (=7° CA+5° CA).

[0010] In the previous control, the allowable amount of chain elongation was always set to a constant value (5° CA) from the time of shipment of a new internal combustion engine. However, because the appropriate range of the timing of the cam angle signal generation was always expanded in the retard direction, in some cases where the dimensional variation of the components was relatively large, the cam angle signal could fall within the appropriate range even though the chain was actually misaligned. As a result, it was possible for internal combustion engines (or vehicles equipped with them) with performance lower than the desired highest level to be supplied to the market.

[0011] The present invention was developed with the above points in mind, and has as its intended purpose the accurate detection of abnormalities such as a misalignment or significant stretching of the timing chain (or belt) of an internal combustion engine both at the time of shipment of a new product and during subsequent operation. [Means for solving the problem]

[0012] In the present invention, a crank angle signal generated every time a crankshaft of an internal combustion engine rotates a certain angle, and a cam angle signal generated every time a camshaft, which is driven by the crankshaft via a wrapping transmission mechanism, rotates a certain angle, are referenced, and it is determined that an abnormality exists when a phase difference between the generation of a crank angle signal, which indicates the timing at which the attitude of the crankshaft reaches a predetermined reference angle, and the generation of a cam angle signal exceeds a delay determination value. In setting the delay determination value, A crank angle up to at least half the interval between the teeth of the sprocket or toothed pulley of the winding transmission mechanism is within a normal range, The base value is then corrected according to the length of time the internal combustion engine has been in operation. α Add Then, the ratio of the increase in the correction value α to the length of the operation period at the initial time X when the operation of the internal combustion engine is started is maximized, the ratio of the increase in the correction value α to the length of the operation period at a subsequent time Y is smaller than that at the initial time X, and the ratio of the increase in the correction value α to the length of the operation period at a further subsequent time Z is smaller than that at the time Y and minimized or set to 0. A control device for an internal combustion engine was constructed. Effect of the Invention

[0013] According to the present invention, abnormalities such as misalignment or significant stretching of the timing chain (or belt) of an internal combustion engine can be correctly detected both at the time of shipment of a new product and during subsequent operation. [Brief description of the drawings]

[0014] [Figure 1] 1 is a diagram showing a schematic configuration of an internal combustion engine and a control device according to an embodiment of the present invention; [Diagram 2] 2 is a diagram showing a wrapping transmission mechanism and a variable valve timing mechanism of the internal combustion engine according to the embodiment; [Diagram 3] 3 is a timing chart showing the relationship between the stroke of each cylinder of the internal combustion engine of the embodiment and a crank angle signal and a cam angle signal. [Figure 4] 5 is a timing chart illustrating a method for determining whether or not an abnormality occurs in the internal combustion engine by the control device of the embodiment. FIG. [Diagram 5] 4 is a diagram illustrating an example of the relationship between a correction value determined by the control device of the embodiment and the length of an operation period of the internal combustion engine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 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 this embodiment. The internal combustion engine in this embodiment is a spark-ignition type four-stroke gasoline engine having a plurality of cylinders 1 (for example, three cylinders, 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 near the intake port connected to each cylinder 1. Also, an ignition plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The ignition plug 12 generates a spark discharge between a center electrode and a ground electrode when an induced voltage generated by an ignition coil is applied to the ignition coil. The ignition coil is integrally built into a coil case together with an igniter, which is a semiconductor switching element.

[0016] An intake passage 3 for supplying intake air to the cylinders 1 takes in air from the outside and guides it to the intake port of each cylinder 1. An air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from upstream on the intake passage 3.

[0017] An exhaust passage 4 for discharging exhaust gas from the cylinders 1 guides exhaust gas generated by burning fuel inside the cylinders 1 to the outside through the exhaust port of each cylinder 1. An exhaust manifold 42 and a three-way catalyst 41 for purifying exhaust gas are arranged on this exhaust passage 4.

[0018] The exhaust gas recirculation device 2 includes elements: an external EGR passage 21 that communicates between the exhaust passage 4 and the intake passage 3, an EGR cooler 22 provided on the EGR passage 21, and an EGR valve 23 that opens and closes the EGR passage 21 to control the flow rate of EGR gas flowing through the EGR passage 21. The inlet of the EGR passage 21 is connected to a predetermined position downstream of the catalyst 41 in the exhaust passage 4. The outlet of the EGR passage 21 is connected to a predetermined position downstream of the throttle valve 32 in the intake passage 3 (in particular, the surge tank 33 or the intake manifold 34).

[0019] As shown in Fig. 2, in the internal combustion engine of this embodiment, a crank sprocket (or a toothed pulley) 71 is fixed to the crankshaft, an intake side cam sprocket (or a toothed pulley) 72 is fixed to the intake camshaft, and an exhaust side cam sprocket (or a toothed pulley) 73 is fixed to the exhaust camshaft, and a timing chain (or a toothed belt) 74 is wound around these sprockets 71, 72, and 73 to form a winding transmission mechanism 7. The timing chain 74 transmits engine torque provided by the crankshaft and the crank sprocket 71 to the intake camshaft via the intake side cam sprocket 72 and to the exhaust camshaft via the exhaust side cam sprocket 73. As a result, the intake camshaft and the exhaust camshaft rotate following the rotation of the crankshaft.

[0020] Thus, a phase-changing type VVT ​​mechanism 6 is interposed between the intake cam sprocket 72 and the intake camshaft. The VVT ​​mechanism 6 is a known mechanism that changes the rotational phase of the intake camshaft relative to the crankshaft to change the opening and closing timing of the intake valve.

[0021] A housing 61 of the VVT ​​mechanism 6 is fixed to a cam sprocket 72, and the cam sprocket 72 and the housing 61 rotate integrally in synchronization with the crankshaft. In contrast, a rotor 62 fixed to one end of an intake camshaft is contained within the housing 61 and is capable of rotating relatively to the cam sprocket 72 and the housing 61. A plurality of fluid chambers through which hydraulic fluid flows in and out are formed inside the housing 61, and each fluid chamber is divided into an advance chamber 612 and a retard chamber 611 by a vane 621 formed on the outer periphery of the rotor 62.

[0022] Lubricating oil, which serves as a hydraulic fluid stored in an oil pan 81, is supplied to the hydraulic (hydraulic) circuit of the VVT ​​mechanism 6 by a lubricating oil pump 82, which serves as a hydraulic fluid pump. An OCV (Oil Control Valve) 9, which is a switching control valve, is provided between the lubricating oil pump 82 and the VVT ​​mechanism 6. By controlling the flow rate and direction of the hydraulic fluid via this OCV 9, the hydraulic fluid pumped up from the oil pan 81 can be selectively supplied to the advance chamber 612 or the retard chamber 611. In this way, the housing 61 rotates relative to the rotor 62, and the opening and closing timing of the intake valve can be advanced or retarded.

[0023] Incidentally, the VVT ​​mechanism 6 may be a motor-driven VVT that changes the phase angle of the camshaft relative to the cam sprocket 72 using an electric motor.

[0024] The ECU0, which is a control device for an internal combustion engine in this embodiment, is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

[0025] The input interface of ECU0 receives inputs such as a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crankshaft and the engine speed, an accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal or the opening of the throttle valve 32 as the accelerator opening (in other words, the required engine torque or engine load factor), a coolant temperature signal d output from a water temperature sensor that detects the coolant temperature of the internal combustion engine, an intake air temperature / intake pressure signal e output from a temperature / pressure sensor that detects the intake air temperature and intake pressure in the intake passage 3 (particularly, the surge tank 33 or the intake manifold 34), a brake signal f output from a sensor (such as a brake switch or a master cylinder pressure sensor) that detects whether the brake pedal is being depressed or the amount of depression of the brake pedal, a cam angle signal g output from a cam angle sensor at multiple cam angles of the intake camshaft, and an atmospheric pressure signal h output from an atmospheric pressure sensor that detects atmospheric pressure.

[0026] A supplementary explanation regarding the crank angle signal b and the cam angle signal g. The crank angle sensor senses the rotation angle of a rotor that is fixed to the crankshaft and rotates integrally with the crankshaft. Teeth or protrusions are formed on the rotor at predetermined angles along the rotation direction of the crankshaft. Typically, a tooth or protrusion is provided for every 10° CA rotation of the crankshaft. The crank angle sensor faces the outer periphery of the rotor, detects when each tooth or protrusion passes near the sensor, and transmits a pulse signal as the crank angle signal b each time. The ECU0 receives this pulse as the crank angle signal b.

[0027] However, the crank angle sensor does not output 36 pulses per revolution of the crankshaft. The teeth or protrusions of the rotor of the crankshaft are partially missing. For example, there are roughly two missing tooth portions: the 17th, 18th, 20th, and 21st missing tooth portions, and the 35th and 36th missing tooth portions. Each missing tooth portion corresponds to a specific rotation phase angle of the crankshaft. That is, consecutive missing tooth portions correspond to 180° CA and 540° CA, and a single missing tooth portion corresponds to 0° CA and 360° CA, with a phase difference of approximately 180° CA between the two.

[0028] As shown in Fig. 3, due to the missing teeth, a part of the pulse train of the crank angle signal b is also missing. Based on this missing part, it is possible to know the absolute attitude (angle) of the crankshaft, in other words, the current position of the piston of each cylinder 1. If the timing of the first pulse following the missing 36th pulse is 0° CA (or 360° CA), then the timing of the 19th pulse following the missing 18th pulse is 180° CA (or 540° CA). The timing of the 0° CA pulse is approximately equal to the compression top dead center of a specific cylinder 1 (the second cylinder in the illustrated example).

[0029] The cam angle sensor also senses the rotation angle of a rotor fixed to the camshaft and rotating together with the camshaft. The rotor has teeth or protrusions formed at least at every angle obtained by dividing one rotation of the camshaft by the number of cylinders. In the case of a three-cylinder engine, a tooth or protrusion is arranged every 120° rotation of the camshaft. The camshaft rotates by receiving a rotational driving force from the crankshaft via a winding transmission mechanism, and its rotation speed is half that of the crankshaft. Therefore, the above teeth or protrusions are arranged every 240° CA when converted into crank angles. In addition, the rotor may have one or more teeth or protrusions between the teeth or protrusions every 240° CA to generate an additional cam angle signal g.

[0030] The cam angle sensor faces the outer circumference of the rotor, detects each tooth or protrusion passing near the sensor, and transmits a pulse signal as a cam angle signal g. The ECU 0 receives this pulse as the cam angle signal g. The basic cam angle signal g generated due to the tooth or protrusion indicates that any one of the cylinders 1 is about to reach a predetermined stroke. As shown in FIG. 3, the basic cam angle signal g output by the cam angle sensor associated with the intake camshaft indicates a certain crank angle from the compression top dead center in each cylinder 1, specifically, a timing advanced by 30° CA. However, in an internal combustion engine equipped with a VVT mechanism 6, the generation timing of the basic cam angle signal g is advanced or retarded depending on the valve timing realized by the VVT ​​mechanism 6 at that time. In other words, the basic cam angle signal g also indicates the intake valve timing (the amount of advance) adjusted by the VVT ​​mechanism 6. By referring to both the crank angle signal b and the cam angle signal g, not only can the current stroke of each cylinder 1 be determined, but the current intake valve timing realized by the VVT ​​mechanism 6 also becomes clear.

[0031] The additional cam angle signal g generated due to a tooth or protrusion corresponds to a specific rotational phase angle of the camshaft and assists in identifying the stroke of each cylinder 1. In the example shown in Fig. 3, the pulse of the additional cam angle signal g is present at a predetermined crank angle, specifically, a timing retarded by 60° CA, from the pulse of the basic cam angle signal g, which indicates a timing advanced by a certain crank angle from the compression top dead center of the third cylinder 1. When the ECU 0 receives these two cam angle signal g pulses consecutively with a predetermined interval (60° CA) between them, it can be seen that the compression top dead center of the third cylinder 1 has arrived together with the latter pulse.

[0032] The output interface of ECU0 outputs an ignition signal i to an igniter connected to the spark plug 12, a fuel injection signal j to the injector 11, an opening operation signal k to the throttle valve 32, an opening operation signal l to the EGR valve 23, a control signal m to the OCV 9 for driving the VVT ​​mechanism 6, and the like.

[0033] The processor of the ECU0 interprets and executes a program stored in the memory in advance, and calculates the operating parameters to control the operation of the internal combustion engine. The ECU0 acquires various pieces of information a, b, c, d, e, f, g, and h required for controlling the operation of the internal combustion engine via an input interface, and determines the engine speed and the amount of intake air filled into the cylinder 1. Then, based on the engine speed and the amount of intake air, the ECU0 determines various operating parameters such as the required fuel injection amount, fuel injection timing (including the number of fuel injections per combustion), fuel injection pressure, ignition timing (including the number of ignitions per combustion), required EGR rate (or EGR gas amount), and intake valve opening and closing timing. The ECU0 applies various control signals i, j, k, l, and m corresponding to the operating parameters via an output interface.

[0034] Furthermore, when starting a stopped internal combustion engine (including cold start and recovery from idling stop), the ECU 0 inputs a control signal o to an electric motor (a starter or cell motor, an ISG (Integrated Starter Generator) or a motor generator; not shown) to perform cranking (or motoring) by rotating the crankshaft using the electric motor, and determines the current stroke of each cylinder 1 by referring to a crank angle signal b and a cam angle signal g. The stroke determination can be performed according to a known method. Then, the ECU 0 starts fuel injection from the injector 11 and ignition by the spark plug 12. Cranking ends (deemed to be complete combustion) when the internal combustion engine goes from initial combustion to continuous combustion and the engine speed, i.e., the rotational speed of the crankshaft, exceeds a threshold value determined according to the cooling water temperature, etc.

[0035] After completing stroke discrimination for cylinder 1, ECU0 judges whether or not an abnormality has occurred in the winding transmission mechanism 7 or the VVT ​​mechanism 6. During cranking of the internal combustion engine and immediately after the completion of starting, the opening and closing timing of the intake valve realized by the VVT ​​mechanism 6 is in an initial position, typically the most retarded position. At this time, the basic cam angle signal g should ideally be generated at a timing corresponding to the initial position. As shown in FIG. 3, this timing is the timing when the attitude of the crankshaft is advanced by a predetermined reference angle, specifically, 30° CA from the compression top dead center of each cylinder 1.

[0036] However, if timing chain 74, which is an element of winding transmission mechanism 7, is misaligned when it is wound around crank sprocket 71 and cam sprockets 72, 73, basic cam angle signal g will deviate from the reference angle timing, which is 30° CA before top dead center of compression. If the teeth of sprockets 71, 72, and 73 are arranged at intervals of approximately 14° CA around their central axes of rotation, when the chain is misaligned, the generation timing of basic cam angle signal g will be advanced or retarded by 14° CA or more from the reference angle timing.

[0037] On the other hand, even if the chain 74 is correctly wound and not misaligned, the generation timing of the basic cam angle signal g may deviate slightly from the reference angle timing due to variations within the dimensional tolerances of the components of the internal combustion engine, including the winding transmission mechanism 7 and the VVT ​​mechanism 6, and due to temperature-dependent expansion and contraction of the components. Furthermore, the generation timing of the crank angle signal b and the cam angle signal g are affected by the rotational speeds and accelerations of the crankshaft and camshaft at that time.

[0038] Therefore, deviations in the basic cam angle signal g from the reference angle timing up to, for example, at least ±7° CA, which is half the tooth spacing of sprockets 71, 72, and 73, are tolerated as being within the appropriate range, that is, are determined to be normal and not abnormal.

[0039] As shown in FIG. 4, after completing stroke discrimination for cylinder 1, ECU0 of this embodiment calculates a phase difference from when it receives a crank angle signal b indicating the timing of 30° CA before top dead center of compression for each cylinder 1, which is the reference angle, to when it receives a basic cam angle signal g corresponding to the crank angle signal b.

[0040] Then, when the phase difference is negative, that is, when the basic cam angle signal g occurs earlier than the crank angle signal b of the reference angle, if the absolute value of the phase difference does not exceed the advance judgment value 7° CA, which is the advance limit of the appropriate range (if the basic cam angle signal b is not more advanced than 37° CA before the compression top dead center of cylinder 1), it is determined that no abnormality has occurred in the winding transmission mechanism 7 or the VVT ​​mechanism 6. On the other hand, if the absolute value of the phase difference exceeds the advance judgment value 7° CA (if the basic cam angle signal b is more advanced than 37° CA before the compression top dead center of cylinder 1), it is determined that an abnormality has occurred in the winding transmission mechanism 7 or the VVT ​​mechanism 6. One of the causes of the abnormality is the incorrect placement of the timing chain 74, as described above.

[0041] If the phase difference is positive, in other words, if the basic cam angle signal g occurs later than the reference angle crank angle signal b, and the absolute value of the phase difference does not exceed the delay judgment value of 7° CA, which is the limit on the retard side of the appropriate range (if the basic cam angle signal b is not retarded more than 23° CA before top dead center of compression of cylinder 1), it is determined that no abnormality has occurred in the winding transmission mechanism 7 and the VVT ​​mechanism 6.

[0042] However, when the internal combustion engine is continuously operated, the timing chain 74 gradually stretches over time. When the chain 74 stretches, the difference between the rotational phase of the crankshaft and the rotational phase of the camshaft increases accordingly, causing the cam angle signal g to lag behind the crank angle signal b.

[0043] If the delay judgment value, which is the limit of the retard side of the appropriate range, is always set to a constant value of 7° CA, in an internal combustion engine in which the dimensions of the components vary relatively widely, even a small stretch of the timing chain 74 could cause the timing of the generation of the basic cam angle signal b to deviate from the appropriate range, and this could be judged to be abnormal even though it does not impair the operation or performance of the engine.

[0044] On the other hand, if the delay judgment value is set to take into account the elongation of the chain 74 in advance, for example by setting the delay judgment value to 12° CA (= 7° CA + 5° CA) from the beginning, in an internal combustion engine with relatively large dimensional variation in its components, even if the chain is actually misaligned, the timing of the generation of the basic cam angle signal b will fall within the appropriate range, creating a concern that abnormal engines that may cause problems in operation or performance will be supplied to the market.

[0045] Therefore, in this embodiment, the ECU0 sets the delay judgment value, which is the limit on the retard side of the appropriate range, to (7+α)°CA, which is the basic value 7°CA plus a correction value α that changes depending on the length of the operation period of the internal combustion engine.

[0046] The relationship between the operation period of the internal combustion engine and the correction value α is illustrated in Fig. 5. As a parameter indicating the length of the operation period of the internal combustion engine, for example, the accumulated travel distance of the vehicle measured by an on-board odometer, the accumulated value of the vehicle speed (time integral, i.e., travel distance) obtained by referring to the output signal a of the vehicle speed sensor, the accumulated value of the engine speed (time integral, i.e., the cumulative number of revolutions of the internal combustion engine) obtained by referring to the crank angle signal b, etc. can be used.

[0047] At the initial time X when a new internal combustion engine starts to operate, the timing chain 74 is likely to stretch, so the ratio of the increase in the correction value α to the length of the operation period is set to be large. The time X is, for example, the period from shipment until the vehicle equipped with the new internal combustion engine has traveled approximately 10,000 to 20,000 km.

[0048] At a later time Y, the timing chain 74 becomes difficult to stretch any further, so the ratio of the increase in the correction value α to the length of the operation period is made smaller than that at time X. The time Y is, for example, the period until the vehicle has traveled approximately 100,000 km to 200,000 km.

[0049] At a later time Z, the timing chain 74 is almost fully extended, so the ratio of the increase in the correction value α to the length of the operation period is minimized or set to 0 (α is set constant). At the time Z, the correction value α approaches or converges to a predetermined value, for example, 5° CA.

[0050] The memory of the ECU0 stores map data or a function formula that defines the relationship between the length of the operation period of the internal combustion engine and the correction value α. The ECU0 searches the map using the length of the current operation period, for example, the accumulated mileage or the accumulated number of revolutions of the internal combustion engine, as a key, or substitutes it into the function formula to perform calculations and obtain the correction value α. Then, when the basic cam angle signal g occurs later than the crank angle signal b of the reference angle, the absolute value of the phase difference between them is compared with the delay judgment value (7+α)° CA, and if the phase difference does not exceed the delay judgment value (if the basic cam angle signal b is not delayed from (23-α)° CA before the compression top dead center of the cylinder 1), it is judged that no abnormality has occurred in the winding transmission mechanism 7 and the VVT ​​mechanism 6. On the other hand, if the absolute value of the phase difference exceeds the delay judgment value (7+α)°CA (if the basic cam angle signal b is retarded more than (23-α)°CA before the compression top dead center of cylinder 1), it is determined that an abnormality has occurred in the winding transmission mechanism 7 or the VVT ​​mechanism 6.

[0051] In addition, instead of comparing the phase difference between the crank angle signal b and the cam angle signal g with the delay judgment value (7+α)° CA, the same result can be obtained by subtracting the correction value α from the phase difference and comparing the result with the basic value 7° CA of the delay judgment value.

[0052] The ECU0, which has determined that an abnormality has occurred in the wrapping transmission mechanism 7 or the VVT ​​mechanism 6, notifies the driver of the abnormality in a manner that appeals to the driver's visual or auditory senses, for example (turning on a warning light (engine check lamp) provided in the cockpit of the vehicle, displaying a message on a display, outputting a warning sound, etc.), and / or executes a fail-safe that changes some or all of the control of the internal combustion engine, specifically the valve timing by the VVT ​​mechanism 6, the opening degree of the throttle valve 32 (total, the amount of intake air), the opening degree of the EGR valve 23 (EGR amount), the amount of fuel injection, the ignition timing, etc., from the normal case in which no abnormality is detected.

[0053] In this embodiment, the control device 0 for an internal combustion engine refers to a crank angle signal b generated every time the crankshaft of the internal combustion engine rotates a certain angle, and a cam angle signal g generated every time the camshaft, which is driven by the crankshaft via the wrapping transmission mechanism 7, rotates a certain angle, and determines that an abnormality exists if the phase difference from the generation of the crank angle signal b to the generation of the cam angle signal g, which indicates the timing at which the attitude of the crankshaft reaches a predetermined reference angle, exceeds a delay determination value.In setting the delay determination value, the control device 0 for an internal combustion engine is configured to add a correction value α, which changes depending on the length of the operating period of the internal combustion engine, to the basic value.

[0054] According to this embodiment, abnormalities such as misalignment or significant stretching of the timing chain 74 of the internal combustion engine can be correctly detected both at the time of shipment of a new product and during subsequent operation.

[0055] The present invention is not limited to the embodiment described above. The internal combustion engine of the above embodiment is not equipped with an exhaust VVT mechanism for variably controlling the opening and closing timing of the exhaust valve, but the internal combustion engine may be equipped with an exhaust VVT mechanism similar to the intake VVT ​​mechanism. In addition, the present invention can also be applied to a case where a cam angle sensor is attached to an exhaust camshaft and the cam angle signal output from the cam angle sensor is referred to together with the crank angle signal b output from a crank angle sensor.

[0056] In addition, the specific configuration of each part can be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0057] 0...Control unit (ECU) 1…Cylinder 6...Variable valve timing (VVT) mechanism 7...Winding transmission mechanism b…Crank angle signal g…Cam angle signal α…Correction value

Claims

[Claim 1] The crank angle signal, which is generated each time a crankshaft of an internal combustion engine rotates a certain angle, and the cam angle signal, which is generated each time a camshaft, which is driven by the crankshaft via a wrapping transmission mechanism, rotates a certain angle, are referenced, and it is determined that an abnormality exists when a phase difference between the generation of a crank angle signal, which indicates the timing when the attitude of the crankshaft reaches a predetermined reference angle, and the generation of a cam angle signal exceeds a delay determination value. When setting the delay judgment value, a crank angle corresponding to at least half the interval between the teeth of the sprocket or toothed pulley of the winding transmission mechanism is set within a proper range that is not abnormal, and a correction value α that changes according to the length of the operation period of the internal combustion engine is added to the basic value. Furthermore, the control device for an internal combustion engine maximizes the ratio of the increase in the correction value α to the length of the operation period at an initial time X when the operation of the internal combustion engine is started, and makes the ratio of the increase in the correction value α to the length of the operation period at a subsequent time Y smaller than that at the initial time X, and further minimizes the ratio of the increase in the correction value α to the length of the operation period at a subsequent time Z smaller than that at the time Y or sets it to zero.

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