JP2008274822A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure intake manifold negative pressure in fail of an electronic throttle, in an engine controlling an intake valve and an exhaust valves to be in a minus overlap state in which the intake valve and the exhaust valve are closed together in cold engine. <P>SOLUTION: The engine has the electronic throttle system controlling opening of a throttle valve to control the intake valve and the exhaust valve to be in the minus overlap state in the cold engine. In the engine, when the fail of the electronic fail occurs, the minus overlap state is prohibited. Concretely, an exhaust valve side VVT is operated in the fail of the electronic throttle to retard open/close timing of the exhaust valve by a predetermined amount R with respect to a most advanced position, and the intake valve and the exhaust valves are controlled not to be in the minus overlap state, so that spit-back to an intake side (intake manifold side) is reduced to secure the intake manifold pressure, that is, to secure brake booster negative pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine equipped with a variable valve timing mechanism that controls opening / closing timing of an engine valve according to an engine operating state.

  In an internal combustion engine (hereinafter also referred to as an engine) mounted on a vehicle or the like, rotation of a crankshaft is transmitted to a camshaft via a timing belt or the like. The engine valve (intake valve / exhaust valve) of the engine is periodically pushed down by the cam of the camshaft and reciprocates to open and close the intake passage and the exhaust passage. In this type of engine, the rotational phase of the camshaft relative to the crankshaft is always constant. On the other hand, in recent years, a variable valve timing (VVT: Variable Valve Timing) mechanism is mounted on the engine (see, for example, Patent Documents 1 and 2). The variable valve timing mechanism is a mechanism for changing the opening / closing timing of the engine valve by changing the rotational phase of the camshaft relative to the crankshaft for the purpose of improving engine output, improving fuel consumption, and reducing exhaust emissions.

  Examples of the variable valve timing mechanism include a helical spline type and a vane type mechanism. Among these, the vane type variable valve timing mechanism is, for example, a housing in which a recess is formed on the inner peripheral surface, and the recess of the housing is divided into two hydraulic chambers (retarding-side hydraulic chamber, advance-side hydraulic chamber). An oil control valve for supplying hydraulic pressure to the retard side hydraulic chamber and the advance side hydraulic chamber in a state where the housing is connected to the crankshaft and the internal rotor is connected to the camshaft. By controlling by (OCV), the rotational phase of the crankshaft and the camshaft is shifted to continuously change the opening / closing timing of the engine valve.

  The oil control valve includes a spool that is reciprocally movable in the casing, a compression coil spring that urges the spool, and an electromagnetic solenoid that attracts the spool by applying a voltage. The voltage applied to the electromagnetic solenoid is duty-controlled, and the attractive force generated by the electromagnetic solenoid changes according to the duty ratio of the applied voltage. The larger the duty ratio of the voltage applied to the electromagnetic solenoid, the larger the hydraulic pressure supply amount to the advance hydraulic chamber, and the smaller the duty ratio, the greater hydraulic pressure supply to the retard hydraulic chamber. In this way, the variable valve timing mechanism is driven by adjusting the hydraulic pressure in the advance side hydraulic chamber and the retard side hydraulic chamber.

  Such a variable valve timing mechanism is disabled during engine start / idle operation and deactivated, and the opening / closing timings of the intake valve and the exhaust valve are set to initial positions. Specifically, the opening / closing timing of the intake valve is set to the most retarded position (advance value = 0), and the opening / closing timing of the exhaust valve is set to the most advanced position (retard value = 0).

  Here, in an engine with a variable valve timing mechanism, there is an engine that is set so that the exhaust valve is closed earlier than the valve timing of a normal engine for the purpose of improving startability during cold start and reducing emissions. is there. In the engine having such a setting, the operation of the variable valve timing mechanism is prohibited during idling or when the vehicle is decelerated (when the accelerator is off), and the valve timings of the intake valve and the exhaust valve are set to the initial positions. As shown in FIGS. 6 and 8, the open periods of the intake valve and the exhaust valve do not overlap (hereinafter sometimes referred to as minus overlap).

  In addition, an engine mounted on a vehicle is provided with an actuator (throttle motor) that drives a throttle valve provided in an intake passage, so that the throttle opening can be controlled independently of the driver's accelerator pedal operation. A throttle system is known.

  In the electronic throttle system, the throttle opening is controlled so that the optimum intake air amount (target intake air amount) is obtained according to the engine operating conditions such as the engine speed and the accelerator pedal depression amount (accelerator opening) of the driver. Is done. Specifically, the actual throttle opening of the throttle valve is detected using a throttle opening sensor or the like, and the actual throttle opening coincides with the throttle opening (target throttle opening) at which the target intake air amount can be obtained. Thus, the throttle valve actuator is feedback controlled. In the electronic throttle system, the throttle valve is also opened during idle operation. The throttle valve opening is adjusted so that the actual idle speed matches the target idle speed, and the idle speed is feedback controlled. (ISC: Idle Speed Control).

  In such an electronic throttle system (hereinafter sometimes simply referred to as “electronic throttle”), the vehicle is retracted when the throttle opening sensor, throttle valve, throttle motor or control system malfunctions (electronic throttle failure). In order to enable traveling, fail-time control is performed in which the opening of the throttle valve is fixed at the opening of the opener (see, for example, Patent Document 3).

On the other hand, as a device that controls the driving force of the vehicle, a brake booster is installed to obtain a strong brake braking force with a light depression force (stepping force) of the brake pedal, and the brake booster negative pressure is reduced to the intake pipe negative pressure ( In the following, there is known a device that secures the intake manifold negative pressure).
JP-A-11-324778 JP 2000-73803 A JP-A-6-2574 Japanese Patent Laid-Open No. 2005-255072 JP 2001-65376 A

  By the way, in an engine set so that the exhaust valve is closed earlier than the normal valve timing (hereinafter, sometimes referred to as an engine set early), as described above, during idle operation or when the vehicle decelerates (accelerator off). ), The variable valve timing mechanism is deactivated and the intake valve and the exhaust valve are simultaneously closed in a minus overlap state.

  On the other hand, in a vehicle equipped with an electronic throttle, the opening of the throttle valve is fixed at a predetermined opener opening regardless of the accelerator opening, in order to ensure retreat travel during electronic throttle failure as described above. For this reason, in an engine with an early closing setting, when the variable valve timing mechanism is deactivated at the time of electronic throttle failure (during deceleration), and the intake and exhaust valves are in a minus overlap state, the exhaust gas remaining and compressed in the exhaust process At the moment when the intake valve is opened in the intake process, it blows back to the intake side (intake manifold side) (see FIG. 10), and the intake manifold negative pressure decreases. If the intake manifold negative pressure decreases in this way, the brake booster negative pressure required at the time of electronic throttle failure may not be ensured, and the brake is applied even though the driver is stepping on the brake pedal. May be less effective.

  The present invention has been made in view of such circumstances, and has an electronic throttle system that controls the opening degree of the throttle valve, and controls the engine in a minus overlap state in which both the intake valve and the exhaust valve are closed when cold. An object of the present invention is to provide a control device capable of ensuring intake manifold negative pressure during an electronic throttle failure in an engine.

  The present invention provides an intake passage and an exhaust passage communicating with a combustion chamber, an intake valve that selectively opens and closes between the combustion chamber and the intake passage, and an opening and closing selectively between the combustion chamber and the exhaust passage. In an internal combustion engine control device comprising an exhaust valve and controlling the intake valve and the exhaust valve to close together when cold, the negative overlap state is prohibited when a negative pressure is required. Yes.

  In the present invention, when assuming a control device for an internal combustion engine provided with a throttle control means for controlling the throttle opening degree of a throttle valve disposed in the intake passage, when the throttle control means is abnormal, the negative pressure is requested. And

  As a specific configuration of the present invention, a variable valve timing mechanism is provided that adjusts the opening / closing timing of the exhaust valve by changing the rotational phase of the exhaust camshaft with respect to the crankshaft of the internal combustion engine. A configuration in which the mechanism is operated and the opening / closing timing of the exhaust valve is retarded by a predetermined amount to control the intake valve and the exhaust valve so as not to be in a minus overlap state.

  In the present invention, as a method of determining an abnormality of the throttle control means (electronic throttle failure), an accelerator opening sensor and a throttle opening sensor are used, and a throttle opening calculated based on an output signal of the accelerator opening sensor There may be mentioned a method of determining that the throttle control means is in an abnormal state when the difference from the actual throttle opening detected based on the output signal of the throttle opening sensor is larger than a predetermined value.

  Further, as a specific configuration of the present invention, a configuration in which the throttle opening of the throttle valve is regulated to a predetermined opener opening when the throttle control means is abnormal can be mentioned.

  According to the present invention, in an internal combustion engine that controls the negative overlap state in which both the intake valve and the exhaust valve are closed when cold, a negative overlap state occurs when a negative pressure is requested (specifically, during an electronic throttle failure). And the intake valve is opened before the exhaust valve closes.Therefore, exhaust gas does not remain in the cylinder of the internal combustion engine in a compressed state, and the intake side when the intake valve is opened ( Blow back to the intake manifold side) can be reduced, and a decrease in intake pipe negative pressure can be suppressed. As a result, the brake booster pressure at the time of electronic throttle failure can be secured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, an engine (internal combustion engine) to which the present invention is applied will be described.

-Engine-
FIG. 1 is a diagram showing a schematic configuration of an engine to which the present invention is applied. FIG. 1 shows only the configuration of one cylinder of the engine.

  The engine 1 is a port injection type multi-cylinder gasoline engine mounted on a vehicle, and a piston 1c that reciprocates in the vertical direction is provided in a cylinder block 1a constituting each cylinder. The piston 1c is connected to the crankshaft 15 via the connecting rod 16, and the reciprocating motion of the piston 1c is converted into rotation of the crankshaft 15 by the connecting rod 16.

  A signal rotor 17 is attached to the crankshaft 15. A plurality of protrusions (teeth) 17 a are provided at equal angles on the outer peripheral surface of the signal rotor 17. A crank position sensor (engine speed sensor) 37 is disposed near the side of the signal rotor 17. The crank position sensor 37 is, for example, an electromagnetic pickup, and generates a pulsed signal (output pulse) corresponding to the protrusion 17a of the signal rotor 17 when the crankshaft 15 rotates.

  A water temperature sensor 31 for detecting the cooling water temperature is disposed in the cylinder block 1 a of the engine 1. A cylinder head 1b is provided at the upper end of the cylinder block 1a, and a combustion chamber 1d is formed between the cylinder head 1b and the piston 1c. A spark plug 3 is disposed in the combustion chamber 1 d of the engine 1. The ignition timing of the spark plug 3 is adjusted by the igniter 4.

  An oil pan 18 for storing lubricating oil is provided below the cylinder block 1 a of the engine 1. The lubricating oil stored in the oil pan 18 is pumped up by an oil pump 19 through an oil strainer 20 (see FIG. 3) that removes foreign matters when the engine 1 is in operation, and the piston 1c, crankshaft 15, and connecting rod. 16 is used for lubrication and cooling of each part. The lubricating oil supplied in this way is used for lubrication and cooling of each part of the engine 1, and then returned to the oil pan 18 until it is pumped up again by the oil pump 19. Stored.

  In this example, the lubricating oil stored in the oil pan 18 is also used as hydraulic oil for variable valve timing mechanisms (hereinafter referred to as VVT) 100in and 100ex, which will be described later. The oil pump 19 is a mechanical pump that is driven by the rotation of the crankshaft 15 of the engine 1.

  An intake passage 11 and an exhaust passage 12 are connected to the combustion chamber 1 d of the engine 1. A part of the intake passage 11 is formed by an intake port 11a and an intake manifold 11b. A part of the exhaust passage 12 is formed by an exhaust port 12a and an exhaust manifold 12b.

The intake passage 11 includes an air cleaner 7, a hot-wire air flow meter 32, an intake air temperature sensor 33 (built in the air flow meter 32), an electronically controlled throttle valve 5 for adjusting the intake air amount of the engine 1, and the like. Has been placed. The throttle valve 5 is driven by a throttle motor 6. The opening degree of the throttle valve 5 is detected by a throttle opening degree sensor 36. In the exhaust passage 12 of the engine 1, an O ₂ sensor 34 for detecting the oxygen concentration in the exhaust gas and the three-way catalyst 8 are disposed.

  A brake booster 300 is connected to the intake passage 11 (intake manifold 11 b) of the engine 1 via a negative pressure introduction passage 302. The brake booster 300 is operated by the intake pipe negative pressure (intake manifold negative pressure), and assists the stepping operation force (brake force) of the brake pedal 301. The assist force generated by the brake booster 300 is supplied to the wheel cylinder via the master cylinder and becomes a braking force that stops the rotation of the wheel.

  An intake valve 13 is provided between the intake passage 11 and the combustion chamber 1d. By opening and closing the intake valve 13, the intake passage 11 and the combustion chamber 1d are communicated or blocked. Further, an exhaust valve 14 is provided between the exhaust passage 12 and the combustion chamber 1d. By opening and closing the exhaust valve 14, the exhaust passage 12 and the combustion chamber 1d are communicated or blocked. The opening / closing drive of the intake valve 13 and the exhaust valve 14 is performed by each rotation of the intake camshaft 21 and the exhaust camshaft 22 to which the rotation of the crankshaft 15 is transmitted via a timing belt or the like. An intake side VVT 100in and an exhaust side VVT 100ex are provided at each end of the intake cam shaft 21 and the exhaust cam shaft 22, respectively. The intake side VVT 100in and the exhaust side VVT 100ex will be described later.

  Further, cam position sensors 38 and 39 are disposed in the vicinity of the intake camshaft 21 and the exhaust camshaft 22, respectively. Each of the cam position sensors 38 and 39 is, for example, an electromagnetic pickup, and is opposed to one protrusion (not shown) on the outer peripheral surface of the rotor provided integrally with the intake camshaft 21 and the exhaust camshaft 22. When the camshafts 21 and 22 are rotated, pulse signals are output. The intake camshaft 21 and the exhaust camshaft 22 rotate at a rotational speed that is 1/2 that of the crankshaft 15. Therefore, each time the crankshaft 15 rotates 720, each cam position sensor 38, 39 has one pulse shape. Signal is generated.

  A fuel injection injector (fuel injection valve) 2 is disposed in the intake passage 11. Fuel of a predetermined pressure is supplied from the fuel tank to the injector 2 by a fuel pump, and the fuel is injected into the intake port 11 a of the intake passage 11. This injected fuel is mixed with intake air to form an air-fuel mixture and introduced into the combustion chamber 1 d of the engine 1. The air-fuel mixture (fuel + air) introduced into the combustion chamber 1d is ignited by the spark plug 3 and combusted / exploded. The piston 1c reciprocates due to combustion / explosion of the air-fuel mixture in the combustion chamber 1d, and the crankshaft 15 rotates. The operating state of the engine 1 is controlled by an ECU (Electronic Control Unit) 400. And the control apparatus of the internal combustion engine of this invention is implement | achieved by the program run by this ECU400.

  Here, in the engine 1 of this example, the exhaust valve 14 opens and closes faster than a normal engine by a predetermined amount (for example, 20 degrees) for the purpose of improving startability during cold start and reducing exhaust emissions. The exhaust valve 14 is closed before exhaust top dead center (BTDC).

-VVT-
As shown in FIGS. 2 and 3, the intake side VVT 100 in and the exhaust side VVT 100 ex include a substantially hollow disk-shaped housing 101 and a vane rotor 104 rotatably accommodated in the housing 101. A plurality (four in this example) of vanes 105 are integrally formed on the vane rotor 104. The vane rotor 104 is fixed to the intake camshaft 21 (or the exhaust camshaft 22) by a center bolt 106, and rotates integrally with the intake camshaft 21 (or the exhaust camshaft 22).

  The front side of the housing 101 is covered with a front cover 107. The housing 101 and the front cover 107 are fixed to the timing pulley 109 with bolts 108, and the housing 101 and the front cover 107 rotate integrally with the timing pulley 109. The timing pulley 109 is connected to the crankshaft 15 via the timing belt 110.

  The same number of convex portions 102 as the vanes 105 of the vane rotor 104 are formed inside the housing 101, and the vanes 105 of the vane rotor 104 are accommodated in the concave portions 103 formed between the convex portions 102. The front end surface of each vane 105 is slidably in contact with the inner peripheral surface of the recess 103. The vane rotor 104 rotates relative to the housing 101 by receiving the pressure of the hydraulic oil by the vane 105. Due to this relative rotation, the rotational phase of the intake camshaft 21 (or the exhaust camshaft 22) with respect to the crankshaft 15 changes.

  In each recess 103 of the housing 101, two spaces defined by the vane 105 of the vane rotor 104 are formed. Of these two spaces, the space behind the vane 105 in the camshaft rotation direction (the direction of the arrow in FIG. 3) constitutes the advance side hydraulic chamber 111, and the front space in the camshaft rotation direction. Constitutes the retard side hydraulic chamber 112.

  In the VVT 100 in and 100 ex having the above structure, the vane rotor 104 rotates relative to the housing 101 by the hydraulic pressure in the advance side hydraulic chamber 111 and the hydraulic pressure in the retard side hydraulic chamber 112. That is, when the hydraulic pressure in the advance hydraulic chamber 111 is made higher than the hydraulic pressure in the retard hydraulic chamber 112, the vane rotor 104 is relative to the housing 101 in the rotational direction of the intake camshaft 21 (or the exhaust camshaft 22). Rotate. At this time, the rotational phase of intake camshaft 21 (or exhaust camshaft 22) is advanced relative to the rotational phase of crankshaft 15 (advance angle). On the contrary, when the hydraulic pressure in the retarded-side hydraulic chamber 112 is made higher than the hydraulic pressure in the advanced-side hydraulic chamber 111, the vane rotor 104 rotates the intake camshaft 21 (or the exhaust camshaft 22) relative to the housing 101. The rotational phase of the intake camshaft 21 (or the exhaust camshaft 22) is delayed relative to the rotational phase of the crankshaft 15 (retarded angle). The valve timing of the intake valve 13 (or the exhaust valve 14) can be made variable by adjusting the rotational phase.

  Next, the configuration of a hydraulic control system that controls the hydraulic pressure of the hydraulic oil supplied to the advance side hydraulic chamber 111 and the retard side hydraulic chamber 112 will be described with reference to FIG.

  First, the intake-side VVT 100in and the exhaust-side VVT 100ex include oil control valves (hereinafter referred to as OCV) 200in, 200ex that control the hydraulic pressure of the hydraulic oil supplied to the advance-side hydraulic chamber 111 and the retard-side hydraulic chamber 112, respectively. Is connected.

  The OCV 200in, 200ex is supplied with lubricating oil (operating oil) pumped from the oil pan 18 via the oil strainer 20 by the oil pump 19 via the oil supply passage 131. In addition, two oil discharge passages 132 and 133 are connected to each OCV 200in and 200ex. The OCVs 200in and 200ex are electromagnetically driven flow control valves, which are controlled by the ECU 400.

  The OCV 200in, 200ex is a 4-port valve, and includes a spool 202 that is reciprocally movable inside the casing 201, a compression coil spring 203 that urges the spool 202 with an elastic force, and an electromagnetic solenoid 204. The spool 202 is attracted when a voltage is applied to the electromagnetic solenoid 204. The voltage applied to the electromagnetic solenoid 204 is duty-controlled by the ECU 400. The attractive force generated by the electromagnetic solenoid 204 changes according to the duty ratio of the applied voltage. The position of the spool 202 is determined by a balance between the attractive force generated by the electromagnetic solenoid 204 and the biasing force of the compression coil spring 203.

  As the spool 202 moves, the amount of communication between the advance side passage 121 and the retard side passage 122 and the oil supply passage 131 and the oil discharge passages 132 and 133 changes, and the advance side passage 121 and the retard side passage 122 change. The amount of hydraulic oil supplied to the corner side passage 122 or the amount of hydraulic oil discharged from the advance side passage 121 and the retard side passage 122 changes.

  For example, in the intake side OCV 200in, the larger the duty ratio of the voltage applied to the electromagnetic solenoid 204, the greater the amount of hydraulic oil supplied to the advance side passage 121, and the rotational phase of the intake camshaft 21 advances. Horned. On the other hand, as the duty ratio is smaller, the amount of hydraulic oil supplied to the retard side passage 122 is increased and the rotational phase of the intake camshaft 21 is retarded. By adjusting the hydraulic pressure in the advance side hydraulic chamber 111 and the retard side hydraulic chamber 112 in this way, the rotational phase of the vane rotor 104 (the rotational phase of the intake camshaft 21 relative to the crankshaft 15) can be adjusted. Thus, the valve timing of the intake valve 13 can be arbitrarily adjusted in the range from the most retarded position to the most advanced position.

  The exhaust-side OCV 200ex is also duty-controlled in the same manner as the intake-side OCV 200in, and the valve timing of the exhaust valve 14 can be arbitrarily adjusted in the range from the most advanced position to the most retarded position. However, the relationship between the retard angle and the advance angle is opposite to that of the OCV 200 in on the intake side.

  The operation of the intake side VVT 100in and the exhaust side VVT 100ex (control of the OCV 200in, 200ex) is controlled by the ECU 400. The ECU 400 controls the operation of the VVTs 100in and 100ex with reference to maps individually set for the VVTs 100in and 100ex based on the operating state of the engine 1 (for example, the engine speed and load).

  Here, in this example, the intake side VVT 100in and the exhaust side VVT 100ex are prohibited from operating (inactive) during idle operation and during deceleration (when the accelerator is off), and the opening and closing timings of the intake valve 13 and the exhaust valve 14 are initial. Set to position. Specifically, the opening / closing timing of the intake valve 13 is set to the most retarded position (advance value = 0) and is mechanically locked by a lock pin. The opening and closing timing of the exhaust valve 14 is set to the most advanced angle position (retard angle value = 0) and is mechanically locked by a lock pin.

  As described above, the engine 1 of this example is set so that the exhaust valve 14 opens and closes faster than a normal engine by a predetermined amount (for example, 20 degrees). When the VVTs 100in and 100ex are not operating, the intake valve 13 and the exhaust valve 14 are in a minus overlap state as shown in FIGS.

-ECU-
As shown in FIG. 4, the ECU 400 includes a CPU 401, a ROM 402, a RAM 403, a backup RAM 404, and the like. The ROM 402 stores various control programs, maps that are referred to when the various control programs are executed, and the like.

  The CPU 401 executes arithmetic processing based on various control programs and maps stored in the ROM 402. The RAM 403 is a memory for temporarily storing calculation results in the CPU 401, data input from each sensor, and the backup RAM 404 is a non-volatile memory for storing data to be saved when the engine 1 is stopped. is there.

  The CPU 401, ROM 402, RAM 403, and backup RAM 404 are connected to each other via a bus 407, and are connected to an input interface 405 and an output interface 406.

The input interface 405 includes a water temperature sensor 31, an air flow meter 32, an intake air temperature sensor 33, an O ₂ sensor 34, an accelerator opening sensor 35 that detects an accelerator opening, a throttle opening sensor 36, a crank position sensor 37, and a cam. Various sensors such as position sensors 38 and 39 are connected. Connected to the output interface 406 are the injector 2, the igniter 4 of the spark plug 3, the throttle motor 6 of the throttle valve 5, and OCV 200 in, 200 ex.

  Then, ECU 400 executes various controls of engine 1 including the injection timing control of injector 2 and the ignition timing control of spark plug 3 based on the output signals of the various sensors described above. The ECU 400 executes the following “idle speed control”, “failure throttle control”, and “failure VVT control”.

-Idle speed control-
The idle speed control is executed when the engine 1 is idling. The engine 1 is adjusted by adjusting the opening of the throttle valve 5 so that the actual idling speed during idling matches the target idling speed. Feedback control of the amount of intake air to

  Specifically, the target idle speed is calculated with reference to a map or the like based on the operating state of the engine 1, and the actual idle speed (engine speed) is read from the output signal of the crank position sensor 37. The opening of the throttle valve 5 is controlled so that the actual idle speed matches the target idle speed, and the intake air amount to the engine 1 is feedback-controlled.

-Throttle control during failure-
In this example, when the throttle opening sensor 36, the throttle valve 5, the throttle motor 6 or the control system is out of order (electronic throttle failure), the throttle can be prevented to prevent the vehicle from moving forward (withdrawing) and preventing engine stall. The control of the opening is restricted (prohibited), and the opening of the throttle valve 5 is fixed to the opener opening by a mechanical device such as a spring.

  Here, as a method of detecting an electronic throttle failure, for example, when the electronic throttle is normal, the nonlinear throttle opening obtained from the accelerator opening and the actual throttle opening move with a certain relationship. Is used, and when the difference between the nonlinear throttle opening and the actual throttle opening is larger than a predetermined value, it is determined that the electronic throttle has failed. The accelerator opening used for the fail determination is calculated from the output signal of the accelerator opening sensor 35, and the actual throttle opening is calculated from the output signal of the throttle opening sensor 36.

-VVT control during failure-
First, as described above, the engine 1 of this example is an engine that is set to be closed early, and the exhaust valve 14 is set to close at a timing before exhaust top dead center. Therefore, at the time of electronic throttle failure (during deceleration), if the intake side VVT 100in and the exhaust side VVT 100ex are inoperative, the intake valve 13 and the exhaust valve 14 are in a minus overlap state (see FIGS. 6 and 8). As shown in FIG. 10, blowback to the intake side (intake manifold side) may occur and the intake manifold negative pressure may decrease.

  Therefore, in this example, when an electronic throttle failure occurs, the exhaust side VVT 100ex is operated to retard the opening / closing timing of the exhaust valve 14 by a predetermined amount with respect to the most advanced position, thereby reducing the intake manifold negative pressure. It is characterized by its suppression. An example of the specific control will be described with reference to the flowchart of FIG. The control routine of FIG.

  First, in step ST1, it is determined whether or not the electronic throttle is failing. If the determination result is negative (when the electronic throttle is normal), normal control of the exhaust side VVT 100ex is continued (step ST4).

  If the determination result in step ST1 is affirmative, that is, if an electronic throttle failure has occurred, the process proceeds to step ST2. When an electronic throttle failure occurs, control of the throttle opening is limited (prohibited) and the opening of the throttle valve 5 is fixed to the opener opening.

  Here, when an electronic throttle failure occurs, in the conventional control, the operation of the intake side VVT 100in and the exhaust side VVT 100ex is prohibited, but in this example, the operation of the exhaust side VVT 100ex is permitted when an electronic throttle failure occurs. In step ST3, the operation of the exhaust side VVT 100ex is controlled, and as shown in FIGS. 7 and 9, the closing timing of the exhaust valve 14 is set to a predetermined retardation amount R (with respect to the most advanced position). The angle is delayed by, for example, 20 degrees.

  By such retardation control, the closing timing of the exhaust valve 14 can be set to the exhaust top dead center (TDC) side with respect to the opening timing of the intake valve 13, and the minus of the intake valve 13 and the exhaust valve 14 is negative. Overlap can be eliminated. As a result, exhaust gas does not remain in the cylinder of the engine 1 in a compressed state, and blowback to the intake side (intake manifold side) when the intake valve 13 is opened can be reduced. As a result, a decrease in intake manifold negative pressure can be suppressed, and a brake booster pressure at the time of electronic throttle failure can be secured.

  Here, in the above-described VVT control at the time of failure, the retard amount R with respect to the most advanced position shown in FIG. 7 is set so that the timing at which the exhaust valve 14 is closed is near the exhaust TDC when an electronic throttle failure occurs. If the exhaust valve 14 is an engine that opens and closes, for example, 20 to 30 degrees earlier than a normal engine for the purpose of reducing startability and exhaust emission during cold start, the opening and closing timing of the exhaust valve 14 is delayed. The angular amount R may be set to, for example, a retard amount (for example, about 20 to 30 degrees) that returns to the opening / closing timing of the exhaust valve of the normal engine.

-Other embodiments-
In the above example, the control of the engine equipped with the vane type VVT has been described. Instead, the present invention is also applied to the control of the engine equipped with another type of VVT such as a helical spline type VVT. Can do. Further, the present invention is not limited to a hydraulic VVT, and can be applied to an engine equipped with an electric VVT.

  Furthermore, the present invention can also be applied to an engine equipped with an electromagnetically driven valve that opens and closes a valve body of an engine valve (intake / exhaust valve) by electromagnetic force of an electromagnet.

  In the above example, an example in which the present invention is applied to control of a port injection type gasoline engine equipped with a VVT (or electromagnetically driven valve) is shown, but the present invention is not limited to this, and the VVT (or electromagnetically driven valve) It can also be applied to control of direct-injection gasoline engines with cylinders. In addition to the in-line multi-cylinder gasoline engine, the present invention can be applied to control of a V-type multi-cylinder gasoline engine.

It is a schematic structure figure showing an example of an engine to which the present invention is applied. It is a disassembled perspective view of VVT mounted in the engine of FIG. FIG. 3 is a diagram illustrating a cross-sectional view of the VVT in FIG. 2 and a schematic configuration diagram of a hydraulic control system of the VVT. It is a block diagram which shows the structure of control systems, such as ECU. It is a flowchart which shows an example of the exhaust side VVT control at the time of electronic throttle failure. It is a figure which shows the opening / closing timing of the intake / exhaust valve at the time of VVT non-operation. It is a figure which shows the opening / closing timing of the intake / exhaust valve at the time of electronic throttle failure and exhaust side VVT operation. It is a figure which shows the opening / closing timing of the intake / exhaust valve at the time of VVT non-operation. It is a figure which shows the opening / closing timing of the intake / exhaust valve at the time of electronic throttle failure and exhaust side VVT operation. It is a figure which shows the problem at the time of electronic throttle failure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 1d Combustion chamber 5 Throttle valve 6 Throttle motor 11 Intake passage 11b Intake manifold 12 Exhaust passage 13 Intake valve 14 Exhaust valve 15 Crankshaft 21 Intake camshaft 22 Exhaust camshaft 35 Accelerator opening sensor 36 Throttle opening sensor 37 Crank position Sensor 100in Intake side VVT
100ex Exhaust side VVT
200in, 200ex OCV
300 Brake booster 400 ECU

Claims (6)

An intake passage and an exhaust passage communicating with the combustion chamber, an intake valve that selectively opens and closes between the combustion chamber and the intake passage, and an exhaust valve that selectively opens and closes between the combustion chamber and the exhaust passage. A control apparatus for an internal combustion engine that controls to a minus overlap state in which both the intake valve and the exhaust valve are closed when cold,
A control apparatus for an internal combustion engine, wherein the negative overlap state is prohibited when a negative pressure is requested. The control apparatus for an internal combustion engine according to claim 1,
A control apparatus for an internal combustion engine, comprising throttle control means for controlling a throttle opening of a throttle valve disposed in the intake passage, wherein the negative pressure is requested when the throttle control means is abnormal. The control apparatus for an internal combustion engine according to claim 1 or 2,
A variable valve timing mechanism that adjusts the opening / closing timing of the exhaust valve by changing the rotational phase of the exhaust camshaft relative to the crankshaft of the internal combustion engine, and operates the variable valve timing mechanism when the negative pressure is requested, A control apparatus for an internal combustion engine, wherein the valve opening / closing timing is retarded by a predetermined amount so that the intake valve and the exhaust valve do not enter a minus overlap state. The control apparatus for an internal combustion engine according to any one of claims 2 and 3,
An accelerator opening sensor and a throttle opening sensor; calculate the throttle opening based on the output signal of the accelerator opening sensor; detect the actual throttle opening based on the output signal of the throttle opening sensor; A control apparatus for an internal combustion engine, wherein when the difference between the calculated throttle opening and the actual throttle opening is greater than a predetermined value, the throttle control means is determined to be in an abnormal state. The control apparatus for an internal combustion engine according to any one of claims 2 to 4,
A control apparatus for an internal combustion engine, comprising throttle opening restriction means for restricting the throttle opening to a predetermined opener opening when the throttle control means is abnormal. The control apparatus for an internal combustion engine according to any one of claims 2 to 5,
A control apparatus for an internal combustion engine, comprising a brake booster that uses an intake pipe negative pressure downstream of a throttle valve disposed in the intake passage.

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