JP2015078628A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform failsafe against the bite-in of foreign matters into a clearance between an intake/exhaust valve and a valve seat, and the accumulation of deposit to a valve or the valve seat.SOLUTION: A control device of an internal combustion engine can detect pressure in a combustion chamber of a cylinder, and controls the internal combustion engine having a variable valve timing mechanism which can change the close timing of an intake valve. On and after the pressure in the combustion chamber which is detected within a prescribed period in which both the intake valve and an exhaust valve during one cycle of the cylinder are closed reaches reference pressure or lower by a prescribed amount, the control device corrects the close timing of the intake valve of the cylinder to a direction in which the close timing approximates an intake lower dead point.

Description

  The present invention relates to a control device that controls an internal combustion engine with a variable valve timing mechanism.

  2. Description of the Related Art An internal combustion engine mounted on a vehicle or the like is known that includes a variable valve timing mechanism that can variably control the opening / closing timing of an intake valve (see, for example, the following patent document).

JP 2012-107594 A

  If foreign matter is caught between the intake valve or exhaust valve of the cylinder and the valve seat, or if deposits adhere to or accumulate on the valve or valve seat, the airtightness of the cylinder cannot be sufficiently secured. In this case, the air-fuel mixture leaks from the cylinder during the compression stroke and the expansion stroke, and the engine torque is reduced, resulting in an inappropriate rotation fluctuation. In addition, the combustion of the air-fuel mixture becomes unstable and misfires easily occur.

  An object of the present invention is to realize fail-safe against foreign object biting between the intake / exhaust valve and the valve seat and deposit accumulation on the valve or the valve seat.

  In order to solve the above-described problems, the present invention controls an internal combustion engine with a variable valve timing mechanism that can detect the pressure in a combustion chamber of a cylinder and can change the closing timing of an intake valve. If the pressure in the combustion chamber detected at a predetermined time when both the intake valve and the exhaust valve are closed during one cycle becomes lower than the reference pressure by a predetermined value or more, the intake valve closing timing of the cylinder is subsequently reduced to the intake bottom A control device for an internal combustion engine that corrects in a direction approaching a point is configured.

  That is, the pressure in the combustion chamber at the time when both the intake valve and the exhaust valve are closed is detected, and based on this, it is determined whether or not the air-fuel mixture leaks from the cylinder to the intake passage or the exhaust passage. If there is, the effective compression ratio is increased as much as possible by closing the intake valve close to the intake bottom dead center.

  According to the present invention, it is possible to realize fail-safe against foreign object biting between the intake / exhaust valve and the valve seat, and deposit accumulation on the valve or the valve seat.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The figure which shows the variable valve timing mechanism in the same embodiment. The figure explaining the content of the correction | amendment control of the intake valve timing by the control apparatus of the embodiment. The figure explaining the content of the correction | amendment control of the intake valve timing by the control apparatus of the embodiment.

  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 four-stroke engine (a series of intake-compression-expansion-exhaust is one cycle), and a plurality of cylinders 1 (one of which is shown in FIG. 1). It has). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode. The ignition coil is integrally incorporated in a coil case together with an igniter that is a semiconductor switching element.

  The intake passage 3 for supplying intake air 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 discharging the exhaust guides the exhaust generated as a result of 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.

  As shown in FIG. 2, in the internal combustion engine in 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 variable valve timing mechanism 6 is interposed between the intake side sprocket 72 and the intake camshaft. The variable valve timing mechanism 6 in the present embodiment 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 variable valve timing mechanism 6 is fixed to the intake side sprocket 72, and the intake side sprocket 72 and the housing 61 are integrally rotated in synchronization 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 fluid stored in the oil pan 81 is supplied from the hydraulic pump 82 to the hydraulic pressure (hydraulic pressure) circuit of the variable valve timing mechanism 6. The hydraulic pump 82 is driven by power from the internal combustion engine. An OCV (Oil Control Valve) 9 that is a switching control valve is provided between the hydraulic pump 82 and the variable valve timing 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 OCV 9 is a so-called electromagnetic four-way spool valve. As shown in FIG. 2, the OCV 9 has a supply port 91 connected to the discharge port of the hydraulic pump 82, an A port 92 connected to the advance chamber 612 of the housing 61, and a B port connected to the retard chamber 611 of the housing 61. 93 and drain ports 94 and 95 connected to the oil pan 81. The spool of the OCV 9 switches the internal particle path by an advancing and retreating operation, and connects the A port 92 and the B port 93 to one of the supply port 91 and the drain ports 94 and 95, respectively. Further, when the spool 96 is in the neutral position, the internal fluid path is interrupted, and the A port 92 and the B port 93 are not communicated with the supply port 91 and the drain ports 94 and 95. FIG. 2 shows a state where the spool 96 is in the neutral position.

  The spool 96 is driven by a solenoid 97. That is, the advance / retreat distance of the spool 96 changes according to the duty ratio of the pulse current (or voltage) input to the solenoid 97 as the control signal m.

  When the duty ratio of the control signal m is relatively large, the hydraulic fluid pressure discharged from the hydraulic pump 82 is supplied to the advance chamber 612 through the A port 92, while already stored in the retard chamber 611. The hydraulic fluid flows down toward the oil pan 81 through the B port 93, and the vane 621 and the rotor 62 are rotated so that the volume of the advance chamber 612 is enlarged and the volume of the retard chamber 611 is reduced. As a result, the rotational phase of the intake camshaft, in other words, the displacement angle of the intake camshaft with respect to the crankshaft is advanced, and the valve timing of the intake valve is advanced.

  On the contrary, when the duty ratio of the control signal m is relatively small, the hydraulic fluid pressure discharged from the hydraulic pump 82 is supplied to the retard chamber 611 through the B port 93, while already stored in the advance chamber 612. The working fluid that has flown down flows toward the oil pan 81 through the A port 92, and the vane 621 and the rotor 62 rotate so that the volume of the retard chamber 611 is expanded and the volume of the advance chamber 612 is decreased. . As a result, the displacement angle of the intake camshaft with respect to the crankshaft is retarded, and the valve timing of the intake valve is retarded.

  Generally speaking, the valve timing of the intake valve is advanced faster as the duty ratio of the control signal m is larger than neutral, and the valve timing of the intake valve is retarded faster as the duty ratio is smaller than neutral.

  An ECU (Electronic Control Unit) 0 serving as a control device for an internal combustion engine according to the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface includes 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 an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. An accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening (so-called required load), and a brake pedaling amount signal d output from a sensor that detects the amount of depression of the brake pedal , An intake air temperature / intake pressure signal e output from a temperature / pressure sensor that detects intake air temperature and intake pressure in the intake passage 3 (especially the surge tank 33), a cooling water temperature of the internal combustion engine (indicating the temperature of the engine) At a plurality of cam angles of the cooling water temperature signal f output from the water temperature sensor for detecting the intake camshaft or the exhaust camshaft A cam angle signal g outputted from the beam angle sensor, cylinder pressure signal h or the like to be output from the cylinder pressure sensor for detecting the combustion chamber pressure of each cylinder 1 are inputted.

  From the output interface, an ignition signal i is output to the igniter 13 of the spark plug 12, a fuel injection signal j is output to the injector 11, an opening operation signal k is output to the throttle valve 32, a control signal m is output to the OCV 9, and the like. To do.

  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. Various operating parameters such as required fuel injection amount, fuel injection timing (including the number of fuel injections per combustion), fuel injection pressure, ignition timing, intake valve timing, etc. To decide. The ECU 0 applies various control signals i, j, k, m corresponding to the operation parameters via the output interface.

  The ECU 0 determines the basic amount of the opening / closing timing of the intake valve based on the operating region of the internal combustion engine at that time [engine speed, required load (or intake pressure, intake amount, fuel injection amount)] and the like. The control mode of the intake valve timing differs depending on whether the internal combustion engine is an Atkinson (Miller) cycle engine or an Otto cycle engine. In the Atkinson cycle engine, the closing timing of the intake valve is significantly delayed from the intake bottom dead center, but the timing is most retarded in the medium load operation region, and tends to advance as the load becomes lower or higher. On the other hand, in an Otto cycle engine, the intake valve timing is usually advanced as the load or the rotational speed increases. In the memory of the ECU 0, map data that defines the relationship between a parameter that defines the operating region of the internal combustion engine and the like and the basic amount of the intake valve timing to be set is stored in advance. The ECU 0 searches the map using the current operation region or the like as a key to know the basic amount of intake valve timing.

  Then, the variable valve timing mechanism 6 is operated to realize the intake valve timing, but the air-fuel mixture leaks from the combustion chamber to the intake passage 3 or the exhaust passage 4 during the compression stroke or expansion stroke of the cylinder 1. When this is detected, fail-safe control for correcting the intake valve timing is executed.

  The ECU 0 of the present embodiment measures the pressure in the combustion chamber of the cylinder 1 at a predetermined timing when both the intake valve and the exhaust valve of the cylinder 1 are closed, for example, the timing of compression top dead center, via an in-cylinder pressure sensor. Compare with reference pressure. The reference pressure is the pressure in the combustion chamber that will be realized at the predetermined time (that is, at the timing of compression top dead center) if there is no air-fuel mixture leak. This reference pressure varies depending on the operation region, intake air temperature, cooling water temperature, and the like at that time. In the memory of the ECU 0, map data that defines the relationship between the parameter that defines the operating region of the internal combustion engine and the reference pressure is stored in advance. The ECU 0 searches the map using the current operation region or the like as a key to know the reference pressure.

  If the measured pressure in the combustion chamber is lower than the reference pressure and the difference between the two is greater than or equal to a predetermined value, the air-fuel mixture leaks into the intake passage 3 or the exhaust passage 4 in the compression stroke or the expansion stroke. Thereafter, the closing timing of the intake valve is corrected so as to approach the intake bottom dead center.

  That is, as shown in FIG. 3, if the closing timing based on the basic amount of the intake valve timing corresponding to the operation region of the internal combustion engine or the like is later than the intake bottom dead center, the intake valve timing is advanced. As a result, the period during which the intake valve is opened after the intake bottom dead center of the cylinder 1 is shortened, and the amount of intake air stored in the combustion chamber of the cylinder 1 increases accordingly (toward the compression top dead center after the intake bottom dead center). As a result of the piston rising upward, the amount of intake air pushed out from the cylinder 1 into the intake passage 3 decreases), the effective compression ratio increases. In this way, adverse effects due to a decrease in the airtightness of the intake / exhaust valves are reduced. In the drawing, the intake valve timing before correction is indicated by a broken line, and the corrected intake valve timing is indicated by a solid line.

  In contrast, as shown in FIG. 4, if the closing timing based on the basic amount of the intake valve timing corresponding to the operating region of the internal combustion engine or the like is earlier than the intake bottom dead center, the intake valve timing is retarded. As a result, the period during which intake air is drawn into the cylinder 1 from the intake passage 3 is lengthened, the amount of intake air charged into the combustion chamber is increased, and the effective compression ratio is increased.

  When an air-fuel mixture leak is detected, the advance / retard angle correction amount added to the basic amount of the intake valve timing is increased as the difference between the measured pressure in the combustion chamber and the reference pressure increases. However, the upper limit is an amount that does not increase the effective compression ratio of the cylinder 1 even if the intake valve timing is changed further.

  In this embodiment, the pressure in the combustion chamber of the cylinder 1 can be detected and the internal combustion engine attached with the variable valve timing mechanism 6 that can change the closing timing of the intake valve is controlled. When the pressure in the combustion chamber detected at a predetermined time when both the intake valve and the exhaust valve of the engine are closed becomes lower than the reference pressure by a predetermined value or more, thereafter, the closing timing of the intake valve of the cylinder 1 is made closer to the intake bottom dead center. A control device 0 for the internal combustion engine that corrects the direction is configured.

  According to the present embodiment, the air-fuel mixture flows from the cylinder 1 to the intake passage 3 or the exhaust passage 4 due to the inclusion of foreign matter between the intake / exhaust valve and the valve seat or the accumulation of deposits on the valve or the valve seat. Decrease in engine torque, rotation fluctuation, and instability of combustion of air-fuel mixture, which occur when leakage occurs, can be suppressed even a little, and can contribute to maintenance of running performance of a vehicle or the like.

  The present invention is not limited to the embodiment described in detail above. For example, the process for determining the presence or absence of air-fuel mixture leakage by comparing the measured value of the pressure in the combustion chamber of the cylinder 1 with the reference pressure may be performed all the time during the operation of the internal combustion engine, or during non-combustion when the compression pressure is stable It may be performed during a fuel cut that temporarily interrupts fuel injection or immediately after the start of cranking for starting the engine.

  In the above embodiment, the measured value of the pressure in the combustion chamber at the compression top dead center timing of the cylinder 1 is compared with the reference pressure, but the pressure in the combustion chamber at other timings (for example, during the compression stroke) is compared. It is good also as what to do. Alternatively, the measured values of the pressure in the combustion chamber during a certain period in the compression stroke or the expansion stroke may be integrated (time integration) and compared with a reference pressure (integrated amount).

  In the above embodiment, the reference pressure is set according to the operation region of the internal combustion engine at that time, the intake air temperature, the cooling water temperature, etc., but instead, the reference pressure is a single value and is compared with the reference pressure. The measured value of the pressure in the combustion chamber to be adjusted may be adjusted according to the operating region of the internal combustion engine, the intake air temperature, the cooling water temperature, and the like at that time.

  The specific mode of the variable valve timing mechanism 6 is arbitrary and not uniquely limited. In addition to those in which the rotation phase of each of the intake camshaft and / or exhaust camshaft relative to the crankshaft is advanced / retarded by hydraulic pressure, the intake valve and / or the exhaust valve are each an electromagnetic solenoid valve, There are known a plurality of intake cams and / or exhaust cams that open and drive valves and / or exhaust valves and use them appropriately, and a mechanism that changes the lever ratio of the rocker arm with an electric motor. These various mechanisms are allowed to be selected and adopted.

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

  The present invention can be applied to control of an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
1 ... Cylinder 6 ... Variable valve timing mechanism

Claims (1)

Controlling the internal combustion engine with a variable valve timing mechanism that can detect the pressure in the combustion chamber of the cylinder and can change the closing timing of the intake valve,
If the pressure in the combustion chamber detected at a given time when both the intake valve and the exhaust valve in one cycle of the cylinder are closed is lower than the reference pressure by a predetermined level or more, the timing of closing the intake valve of the cylinder will be reduced below the intake air. A control device for an internal combustion engine that corrects the direction close to the dead center.

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