JP2017133468A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress occurrence of abnormal combustion in a cylinder of an internal combustion engine.SOLUTION: In a control device of an internal combustion engine for controlling the internal combustion engine provided with a variable valve timing mechanism capable of changing an actual compression ratio of the cylinder by changing a valve opening timing or a valve closing timing of an intake valve, when a state in which the valve opening timing or the valve closing timing of the intake valve is advanced with respect to a prescribed timing is continued for a prescribed time or more, an upper limit of an opening of a throttle valve is determined to be lowered in comparison with an upper limit in the other case, or an opening of the throttle valve according to a step-in amount of an accelerator pedal is reduced in comparison with an opening in the other case.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a control device for controlling an internal combustion engine attached with a variable valve timing mechanism that can change the valve opening timing and / or valve closing timing of an intake valve.

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

JP, 2015-007413, A

  Recently, aiming to further improve the thermomechanical conversion efficiency of the internal combustion engine, the theoretical compression ratio of the cylinder (geometric compression ratio or nominal compression ratio. Clearance volume (combustion chamber volume when the piston is at compression top dead center) And the sum of the piston stroke volume and the clearance volume).

  On the other hand, the actual compression ratio of the cylinder of the internal combustion engine, that is, the effective compression ratio with respect to intake air (typically, the value obtained by dividing the combustion chamber volume at the start of compression of intake air by the combustion chamber volume at the end of compression) is VVT. It is affected by the intake valve timing embodied by the mechanism. That is, the actual compression ratio increases as the opening timing and closing timing of the intake valve advance, and conversely decreases as they retard.

  If the advance amount of the intake valve timing exceeds the limit, the risk of causing abnormal combustion such as pre-ignition or heavy knock in the cylinder increases in combination with the higher compression ratio of the cylinder. This kind of abnormal combustion may damage the internal combustion engine and is not preferable.

  An object of the present invention is to effectively suppress the occurrence of abnormal combustion in a cylinder of an internal combustion engine.

  In order to solve the above-described problems, the present invention controls an internal combustion engine with a variable valve timing mechanism that can change the actual compression ratio of a cylinder by changing the opening timing or closing timing of the intake valve. The upper limit of the throttle valve opening is not set when the intake valve opening timing or valve closing timing has advanced more than the predetermined timing for a predetermined time or longer. The control device for the internal combustion engine is configured such that the opening of the throttle valve is set to be lower than the opening of the throttle valve or the opening of the throttle valve corresponding to the amount of depression of the accelerator pedal is reduced compared with the opening when the throttle valve is not.

  According to the present invention, occurrence of abnormal combustion in a cylinder of an internal combustion engine can be effectively suppressed.

The figure which shows schematic structure of the internal combustion engine and control apparatus in one Embodiment of this invention. The figure which illustrates the relationship between the driving | operation area | region of an internal combustion engine, and the possibility of generation | occurrence | production of abnormal combustion. The flowchart which shows the example of a procedure of the process which the control apparatus of this embodiment performs.

  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). 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 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.

  The internal combustion engine of the present embodiment is accompanied by a VVT mechanism 6 that can variably control the opening / closing timing of the intake valve of each cylinder 1. The VVT mechanism 6 is a known one (motor drive VVT) in which the rotation phase of the intake camshaft that drives the intake valve of each cylinder 1 with respect to the crankshaft is changed by an electric motor. As is well known, an intake camshaft of an internal combustion engine is supplied with a rotational driving force from a crankshaft that is an output shaft of the internal combustion engine, and rotates following the crankshaft. A winding transmission device (not shown) for transmitting a rotational driving force is interposed between the crankshaft and the intake camshaft. The winding transmission includes a crank sprocket (or pulley) provided on the crankshaft side, a cam sprocket (or pulley) provided on the intake camshaft side, and a timing chain (or pulley) wound around these sprockets (or pulleys). Or a belt) as an element. The VVT mechanism 6 changes the rotation phase of the intake camshaft relative to the crankshaft by rotating the intake camshaft relative to the cam sprocket, thereby changing the opening / closing timing of the intake valve.

  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 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 signal b output from an engine rotation sensor that detects the rotation angle of the crankshaft and the engine speed, and an accelerator pedal. The accelerator opening signal c output from a sensor that detects the amount of depression of the engine or the opening of the throttle valve 32 as an accelerator opening (in other words, an engine load required for the internal combustion engine, a required output), 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, a vibration signal e output from a vibration type knock sensor for detecting the magnitude of vibration of the cylinder block containing the cylinder 1, an intake passage 3 ( In particular, the intake air temperature / intake output from the temperature / pressure sensor that detects the intake air temperature and intake pressure in the surge tank 33). Pressure signal f, cam angle signal g output from the cam angle sensor at a plurality of cam angles of the intake camshaft, a sensor that detects whether the brake pedal is depressed or the amount of depression of the brake pedal (brake switch or master cylinder) A brake signal h or the like output from a pressure sensor or the like is input.

  The crank angle sensor senses the rotation angle of a rotor that is fixed to the shaft end of the crankshaft and rotates integrally with the crankshaft. The rotor is formed with teeth or protrusions at predetermined angles along the rotation direction of the crankshaft. Typically, each 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 b each time. However, the crank angle sensor does not output 36 pulses during one revolution of the crankshaft. Some of the teeth or protrusions of the rotor of the crankshaft are missing. Each missing tooth portion corresponds to a specific rotational phase angle of the crankshaft. Due to the missing tooth portion, a part of the pulse train of the crank angle signal b is also lost. Based on this missing pulse, the absolute angle (posture) of the crankshaft, in other words, the current position of the piston of each cylinder 1 can be known.

  The cam angle sensor senses the rotation angle of the rotor that is fixed to the shaft end of the intake camshaft and rotates integrally with the intake camshaft. Teeth or protrusions are formed on the rotor at predetermined angles along the rotation direction of the intake camshaft. The cam 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 the cam angle signal g each time. If both the crank angle signal b and the cam angle signal g are referred to, the current stroke of each cylinder 1 can be determined and known, and the current intake valve timing (the advance angle of the VVT mechanism 6) is realized. Amount) becomes clear.

  From the output interface of the ECU 0, the ignition signal i for the igniter, the fuel injection signal j for the injector 11, the opening operation signal k for the throttle valve 32, the opening operation signal l for the EGR valve 23, VVT. An intake valve timing control signal n or the like is output to the 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 n corresponding to the operation parameters via the output interface.

  The throttle valve 32, which is an intake throttle valve, is usually operated according to the amount of depression of the accelerator pedal by the driver. That is, the opening degree of the throttle valve 32 is increased as the amount of depression of the accelerator pedal is increased. However, when the actual compression ratio of the cylinder 1 is high, that is, when the throttle valve 32 is opened greatly when the advance amount of the opening / closing timing of the intake valve is large, the in-cylinder pressure and the in-cylinder temperature become very high, There is a concern of causing abnormal combustion such as pre-ignition and heavy knock.

  Therefore, the ECU 0 of this embodiment sets an upper limit on the opening degree of the throttle valve 32 in an operation region where the risk of causing abnormal combustion is high, and makes the throttle valve 32 exceed the upper limit opening degree no matter how large the accelerator pedal is depressed. Opening the door to prevent abnormal combustion.

  FIG. 2 shows the operating range of the internal combustion engine [engine speed, intake pressure in surge tank 33 (or opening of throttle valve 32) under the condition that the opening / closing timing of the intake valve is advanced most via the VVT mechanism 6. , The amount of intake (fresh air) or fuel injection amount charged into the cylinder 1)] and the possibility of occurrence of abnormal combustion. In FIG. 2, the hatched area is a high risk area that causes abnormal combustion. Basically, abnormal combustion is likely to occur in a high load region where the opening of the throttle valve 32 is large and in a region where the engine speed is high or low.

  As shown in FIG. 3, the ECU 0 of the present embodiment has the current intake valve opening / closing timing advanced by a predetermined timing, in other words, the intake valve timing (the reference timing or the most retarded timing). When the amount of advance angle is greater than the threshold value (step S1) and the state continues for a predetermined time or longer (step S2), control for preventing abnormal combustion is performed (step S1). S3).

  Specifically, as described above, the control for preventing abnormal combustion sets an upper limit for the opening of the throttle valve 32 (or the control for preventing abnormal combustion is performed without satisfying the conditions of steps S1 and S2). The upper limit of the opening degree of the throttle valve 32 is reduced as compared with the case of not performing (normal control).

  Regarding step S1, the threshold value to be compared with the advance amount of the intake valve timing is preferably adjusted according to the current engine speed. For example, a threshold value used in a high rotation region and / or a low rotation region where the risk of occurrence of abnormal combustion is high is set to a lower value than a threshold value used in a medium rotation region where the risk of occurrence of abnormal combustion is relatively low.

  Similarly, regarding step S2, the length of the predetermined time can be adjusted according to the engine speed. For example, the length of the predetermined time in the high rotation region and / or the low rotation region is shortened compared with that in the medium rotation region.

  Alternatively, the threshold value in step S1 and / or the length of the predetermined time in step S2 are set based on the current engine speed and the intake pressure in the surge tank 33 (or the opening of the throttle valve 32, the intake amount charged into the cylinder 1 or The fuel injection amount) may be adjusted. In that case, the threshold value is set to be lower as the intake pressure in the surge tank 33 (or the opening of the throttle valve 32, the intake air amount or the fuel injection amount charged into the cylinder 1) is larger, and / or the predetermined time is set. It will be set short.

  However, when the upper limit value irrelevant to the operating region of the internal combustion engine is set as the threshold value in step S1, and the state where the advance amount of the intake valve timing exceeds the upper limit value continues for a predetermined time or more, The control for preventing abnormal combustion is not hindered.

  Therefore, if the control for preventing abnormal combustion has already been carried out (step S0), the condition that the advance amount of the intake valve timing has been equal to or less than the above-mentioned threshold value has continued for a certain period of time. (Steps S4 and S5), the control for preventing abnormal combustion is terminated (Step S6), and the control returns to normal control.

  In the present embodiment, an internal combustion engine attached with a variable valve timing mechanism 6 that can change the actual compression ratio of the cylinder 1 by changing the opening / closing timing of the intake valve is controlled. An internal combustion engine in which the upper limit of the opening degree of the throttle valve 32 is set lower than the upper limit in the case where it is not (normal control) when the state of advancement from a predetermined timing continues for a predetermined time or more The control device 0 was configured. According to this embodiment, it is possible to appropriately prevent the abnormal combustion from occurring in the cylinder 1 and avoid damaging the internal combustion engine.

  The present invention is not limited to the embodiment described in detail above. In the above-described embodiment, when the state in which the opening / closing valve timing of the intake valve is advanced from the predetermined timing continues for a predetermined time or longer, the control of the opening degree of the throttle valve 32 is performed as control for preventing abnormal combustion. The upper limit was set lower than the upper limit in the case where it was not. However, instead of this, as the control for preventing abnormal combustion, the opening degree of the throttle valve 32 corresponding to the depression amount of the accelerator pedal may be reduced. That is, on the assumption that the amount of depression of the accelerator pedal is the same, the opening of the throttle valve 32 when the conditions of steps S1 and S2 are satisfied is the same as when the condition is not satisfied (normal condition) It is smaller than the opening degree in the control).

  Further, the specific mode of the VVT mechanism 6 for changing the valve opening timing and / or the valve closing timing of the intake valve of each cylinder 1 of the internal combustion engine is arbitrary and is not uniquely limited. In addition to those that advance / retard the rotation phase of the intake camshaft with respect to the crankshaft, multiple cams that drive the intake valve to open are prepared and used appropriately. The lever ratio of the rocker arm Are known, and the intake valve is an electromagnetic solenoid valve, etc., and it is allowed to be selected from these various mechanisms.

  In the VVT mechanism 6 in which the rotation phase of the intake camshaft relative to the crankshaft is advanced / retarded, the valve opening timing and the valve closing timing of the intake valve change synchronously, but the VVT mechanism 6 in other aspects Is mounted in the internal combustion engine, the valve opening timing and the valve closing timing of the intake valve can be changed asynchronously, or only the valve opening timing or only the valve closing timing can be changed. Therefore, the advance amount of the intake valve opening timing (from the reference timing or the most retarded timing) may be different from the advance amount of the same intake valve closing timing.

  Even if only the valve opening timing or only the valve closing timing of the intake valve is advanced / retarded, it is possible to increase / decrease the amount of intake air charged into the cylinder 1. Therefore, it is permitted to determine whether or not to perform control for preventing abnormal combustion in accordance with the advance amount of either the valve opening timing or the valve closing timing of the intake valve. That is, when the intake valve opening timing or valve closing timing has advanced more than the predetermined timing for more than the predetermined time, the upper limit of the throttle valve opening is compared with the upper limit of the other case Therefore, the throttle valve opening corresponding to the amount of depression of the accelerator pedal is reduced compared with the opening in the case where it is not.

  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)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 11 ... Injector 32 ... Throttle valve 6 ... Variable valve timing (VVT) mechanism b ... Crank angle signal c ... Accelerator opening signal g ... Cam angle signal k ... Opening operation signal n ... Control signal of intake valve timing

Claims (1)

Controlling an internal combustion engine with a variable valve timing mechanism that can change the actual compression ratio of the cylinder by changing the opening timing or closing timing of the intake valve,
Compare the upper limit of the throttle valve opening with the upper limit in the case where the opening timing or closing timing of the intake valve has advanced more than the predetermined timing for more than the predetermined time. A control device for an internal combustion engine that is set to a low value or reduces an opening degree of a throttle valve according to an accelerator pedal depression amount compared to an opening degree when the throttle valve is not.

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