JP6261211B2 - Control device for internal combustion engine. - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine that performs fuel cut when a predetermined condition is satisfied.

  In an internal combustion engine mounted on a vehicle, it is known to execute a fuel cut that interrupts fuel injection in accordance with the operation state. Normally, when the accelerator pedal depression amount is 0 or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permission speed, the fuel cut is started assuming that the fuel cut condition is satisfied. Then, when any fuel cut end condition is satisfied, such as when the accelerator pedal depression amount exceeds the threshold, the fuel cut ends and fuel injection resumes.

  In addition, it is also common to execute idle stop for stopping idle rotation of the internal combustion engine while the vehicle is stopped due to a signal waiting or the like. In the known idling stop system, the internal combustion engine is stopped when various conditions such as the vehicle speed is lower than a predetermined value, the brake pedal is depressed, and the coolant temperature and the battery voltage are sufficiently high are satisfied.

  In a vehicle that performs such fuel cut and idle stop, when the driver removes his or her foot from the accelerator pedal while the vehicle is running and the vehicle decelerates and stops, the fuel cut condition is satisfied first. Then, fuel cut is started, and then it shifts to idle stop.

  In recent years, it has been known that a predetermined vehicle speed, which is a condition for executing idle stop, is set higher than before in order to give priority to improvement in fuel consumption. In a vehicle in which such idle stop is executed at a higher vehicle speed than before, when the vehicle stops after the fuel cut is performed, the fuel injection is not performed again, and the rotation of the internal combustion engine is stopped before the vehicle stops. The so-called “eco-run” control is performed.

  Conventionally, in order to increase the resistance to movement in the top dead center direction of the piston in the cylinder that is in the compression stroke and the cylinder that is in the expansion stroke when the internal combustion engine that performs idling stop assuming the vehicle stop is stopped, the stop operation period A technique for controlling a throttle valve to be opened for a predetermined period only for a predetermined period is disclosed (for example, see Patent Document 1). Such a technique is intended to adjust the stop position of the piston to a desired position so that the subsequent restart can be performed satisfactorily.

  However, if an idling stop system in which a predetermined vehicle speed for executing the recent idle stop is set to a higher value than before is adopted, the vehicle speed, the number of revolutions and the number of revolutions at the start of the fuel cut leading to the vehicle stop There is a variation in the degree of descent due to the situation when the fuel cut condition is satisfied. That is, as in the above-mentioned patent document, the control of simply opening the throttle valve a predetermined time after the start of fuel cut does not stop the piston at a desired piston stop position regardless of the behavior of the rotational speed.

JP 2004-124754 A

  The present invention focuses on the above-mentioned problem for the first time, and aims to improve control when the vehicle is stopped and to improve restartability of the internal combustion engine after idling stop.

  In order to achieve such an object, the present invention takes the following measures.

That is, the control device for an internal combustion engine according to the present invention performs a fuel cut that stops fuel injection when the fuel cut condition is satisfied, and when the vehicle stops without performing the fuel injection from the execution of the fuel cut, The rotation speed of the internal combustion engine when the fuel cut condition is satisfied , the lowering speed of the rotation speed of the internal combustion engine during the fuel cut, and the valve opening operation of the throttle valve Based on the air responsiveness, which is the time lag until the intake air pressure increases, the timing for opening the throttle valve to stop the piston at the desired position is determined , and the intake air pressure becomes atmospheric pressure. Then, the opened throttle valve is closed .

  If this is the case, the throttle valve is opened after taking into account the parameters that affect the operation of the piston when the fuel cut condition is satisfied, regardless of the variation in the behavior of the rotational speed at the start of the fuel cut. It is possible to realize stopping the piston at a desired position. As a result, it is possible to perform a subsequent restart with the cylinders in a uniform state. As a result, it becomes easy to perform various controls for performing a reliable start while suppressing fuel injection, so that excessive increase in the number of revolutions at the start can be effectively avoided, which contributes to an improvement in fuel consumption.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the internal combustion engine which improves the startability of an internal combustion engine and contributes to the improvement of a fuel consumption can be provided.

The figure which shows the whole structure of the internal combustion engine for vehicles in one Embodiment of this invention. The figure which shows the structure of the drive system of the vehicle in the embodiment. The timing chart which concerns on the same 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 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 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.

  FIG. 2 shows an example of a drive system provided in the vehicle. This drive system includes a torque converter 7 and automatic transmissions 8 and 9. In particular, in the present embodiment, a forward / reverse switching device 8 using a planetary gear mechanism and a belt-type CVT (Continuously Variable Transmission) 9 which is a type of continuously variable transmission are adopted as components of the automatic transmissions 8 and 9. doing.

  The rotational driving force output from the internal combustion engine is input from the crankshaft of the internal combustion engine to the pump impeller 71 on the input side of the torque converter 7 and transmitted to the turbine runner 72 on the output side. The rotation of the turbine runner 72 is transmitted to the drive shaft 94 of the CVT 9 via the forward / reverse switching device 8 and rotates the driven shaft 95 through a shift in the CVT 9. The rotation of the driven shaft 95 is transmitted to the output gear 101. The output gear 101 meshes with the ring gear 102 of the differential device, and rotates the axle 103 and the drive wheels (not shown) via the differential device.

  The torque converter 7 includes a lockup mechanism. The lock-up mechanism is known in this field, and a lock-up clutch 73 that fastens the input side and the output side of the torque converter 7 so as not to rotate relative to each other, and an operation for switching the connection of the lock-up clutch 73. A lock-up solenoid valve (not shown) for controlling the hydraulic pressure (hydraulic pressure) is used as an element. The lockup solenoid valve is a flow rate control valve that receives a control signal l and changes its opening.

  In principle, the torque converter 7 is almost always locked up under conditions where the vehicle speed is higher than a certain level, for example, at 10 km / h or higher. When the vehicle speed becomes lower than 10 km / h, the lockup of the torque converter 7 is released.

  During lockup, the lockup clutch 73 is pressed against the torque converter cover 74 and rotates together with the torque converter cover 74. During lock-up, the engine torque input to the drive plate on the input side of the torque converter 7 is directly transmitted from the torque converter cover 74 to the forward / reverse switching device 8 on the output side of the torque converter 7 via the lock-up clutch 73. Communicated. At the time of lockup, the speed ratio, which is the ratio of the output side rotational speed of the torque converter 7 to the input side rotational speed, is 1.

  When the lockup is not performed, the lockup clutch 73 is separated from the torque converter cover 74. At the time of non-lock-up, the engine torque input to the input side of the torque converter 7 is transmitted from the torque converter cover 74 to the pump impeller 71 and the turbine 72 and is transmitted to the forward / reverse switching device 8. At the time of non-lock-up, the speed ratio of the torque converter 7 becomes smaller or larger than 1 depending on the driving state.

  In the forward / reverse switching device 8, the sun gear 81 communicates with the turbine runner 72, and the ring gear 82 communicates with the drive shaft 94. Between the planetary carrier 83 that supports the planetary gear 831 and the transmission case, a forward brake 84 that is a hydraulic clutch that can be connected and disconnected is interposed. Further, a reverse clutch 85, which is a hydraulic clutch capable of switching connection / disconnection, is also interposed between the planetary carrier 83 and the sun gear 81 (or the output side of the torque converter 7).

  In the D range of the traveling range, the forward brake 84 is engaged and the reverse clutch 85 is disconnected. As a result, the rotation of the output shaft of the torque converter 7 is reversed and decelerated and transmitted to the drive shaft 94 for forward travel. In the R range, the reverse clutch 85 is engaged and the forward brake 84 is disconnected. As a result, the sun gear 81 and the planetary carrier 83 rotate integrally, and the output shaft of the torque converter 7 and the drive shaft 94 are directly connected to perform reverse travel. A solenoid valve (not shown) that controls the hydraulic pressure for driving the forward brake 84 or the reverse clutch 85 to connect / disconnect is a flow rate control valve that receives a control signal m and changes its opening.

  In the N range and P range, which are non-traveling ranges, both the forward brake 84 and the reverse clutch 85 are disconnected. In short, the forward / reverse switching device 8 serves as a clutch for connecting between the internal combustion engine and the axle 103 and for disconnecting between the internal combustion engine and the axle 103.

  The CVT 9 includes a driving pulley 91 and a driven pulley 92, and a belt 93 wound around the pulleys 91 and 92 as elements. The drive pulley 91 is disposed behind the movable sheave 912, a fixed sheave 911 fixed to the drive shaft 94, a movable sheave 912 supported on the drive shaft 91 via a roller spline so as to be displaceable in the axial direction. A hydraulic servo 913 is provided, and the gear ratio can be changed steplessly by operating the hydraulic servo 913 and displacing the movable sheave 912. The driven pulley 92 is disposed on the back of the movable sheave 922, a fixed sheave 921 fixed to the driven shaft 95, a movable sheave 922 supported on the driven shaft 95 via a roller spline so as to be axially displaceable. A hydraulic servo 923 is provided, and a belt thrust necessary for torque transmission is applied by operating the hydraulic servo 923 and displacing the movable sheave 922.

  A hydraulic pump (hydraulic fluid) supplied to the forward brake 84 or the reverse clutch 85 to operate the travel range, and a hydraulic pump (discharge fluid) supplied to the hydraulic servos 913 and 923 to operate the gear ratio. (Not shown) is of a known mechanical type (non-electric type) that operates by receiving the rotational driving force from the crankshaft of the internal combustion engine. This hydraulic fluid is common to the fluid used for the torque converter 7.

  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 of the crankshaft and the engine speed, and the accelerator pedal. An accelerator opening signal c output from a sensor that detects the depression amount or the opening of the electronic throttle valve 32 as an accelerator opening (so-called required load), and a brake depression amount that is output from a sensor that detects the depression amount of the brake pedal A signal d, 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 (particularly, the surge tank 33), and a water temperature sensor that detects a cooling water temperature of the internal combustion engine. Sensor (or shift position switch) for knowing output coolant temperature signal f and shift lever range Shift range signal g which is et output, hydraulic fluid temperature signal h or the like to be outputted from the liquid temperature sensor for detecting the temperature of the working fluid used in the torque converter 7 and the automatic transmission 8 and 9 are inputted.

  From the output interface, an ignition signal i for the igniter of the spark plug 12, a fuel injection signal j for the injector 11, an opening operation signal k for the electronic throttle valve 32, and connection / disconnection switching of the lockup clutch 73. An opening degree control signal l is outputted to the lockup solenoid valve, an opening degree control signal m is outputted to the solenoid valve for switching connection / disconnection of the forward brake 84 or the reverse clutch 85, a transmission ratio control signal n is outputted to the CVT 9, etc. .

  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 amount of intake air. 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, and torque converter 7 lock-up are controlled. Various operation parameters such as whether or not to perform, connection / disconnection of the clutches 84 and 85, and the gear ratio of the automatic transmissions 8 and 9 are determined. As the operation parameter determination method itself, a known method can be adopted. The ECU 0 applies various control signals i, j, k, l, m, and n corresponding to the operation parameters via the output interface.

  Further, the ECU 0 inputs a control signal o to the electric motor (starter motor or motor generator) when the internal combustion engine is started (a cold start or a return from an idling stop). Cranking is performed by rotating the crankshaft. Cranking is considered when the internal combustion engine has changed from the first explosion to the continuous explosion, and the rotational speed of the internal combustion engine, that is, the rotation speed of the crankshaft exceeds a judgment value determined according to the cooling water temperature, etc. )finish.

  The ECU 0 of this embodiment stops fuel injection from the injector 11 (and spark ignition by the spark plug 12) when a deceleration request is made to the vehicle, and executes a fuel cut that interrupts fuel supply to the cylinder 1. The ECU 0 determines that the fuel cut condition is satisfied, at least when the accelerator pedal depression amount is 0 or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permission speed.

  In fact, even if the fuel cut condition is satisfied, the fuel injection is not immediately stopped. If the fuel supply is suddenly cut off at a stage where the engine torque is relatively large, a torque shock is generated in which the engine speed and the vehicle speed drop stepwise, causing the passengers including the driver to feel the shock. In order to reduce the torque shock, the fuel injection is stopped only after the elapse of the delay time after the fuel cut condition is satisfied. During this delay time, the ignition timing is retarded and the engine torque is actively reduced.

  If a predetermined fuel cut end condition is satisfied during the fuel cut, the fuel cut is ended and fuel injection (and ignition) is restarted. The ECU 0 determines that the fuel cut end condition is satisfied, for example, when the accelerator pedal depression amount exceeds a threshold value or the engine speed decreases to the lower limit speed (fuel cut return speed). To do.

  In addition, the ECU 0 of the present embodiment executes an idling stop that stops the idle rotation of the internal combustion engine when the vehicle stops due to a signal waiting or the like. ECU0 is idling when the vehicle speed is below a predetermined value, the brake pedal is depressed, the coolant temperature and battery voltage are sufficiently high, and the brake booster negative pressure is sufficiently secured. It is determined that the stop condition is satisfied.

  When a predetermined idling stop end condition is satisfied after the idling stop condition is satisfied, the internal combustion engine is restarted. The ECU 0 is one in which the driver has lifted his / her foot from the brake pedal, the brake pedal has been further depressed, the accelerator pedal has been depressed, a predetermined time (for example, 3 minutes) has elapsed in the idling stop state, etc. In any case, it is determined that the idling stop end condition is satisfied.

  Here, in the present embodiment, when the driver removes his / her foot from the accelerator pedal while the vehicle is traveling and the vehicle decelerates and stops, the fuel cut condition is first satisfied and the fuel cut is started, and then the idling stop is performed. The condition is met and the system shifts to idling stop. As an example of such control, the fuel cut condition is established when the vehicle speed drops to about 13 km / h, and then the lockup of the torque converter 7 is released and the idling stop condition is established, and then fuel injection is performed. Without performing the procedure, the rotation of the internal combustion engine is stopped before the vehicle is stopped, and the vehicle is stopped.

  Therefore, as shown in FIG. 3, the ECU 0 as the control device for the internal combustion engine according to the present embodiment, when the fuel cut condition is satisfied, the lowering speed θ, which is the lowering degree at which the rotational speed α decreases, Based on the air responsiveness β derived from the timing at which the intake pressure changes, the valve opening timing x at which the throttle valve 32 is opened to stop the piston at a desired position is determined.

  Hereinafter, the control of this embodiment will be described with reference to the timing chart of FIG. In the figure, the fuel cut flag, fuel cut time, throttle valve 32 open / close state, intake pressure behavior, internal combustion engine speed, and internal combustion engine stoppage from the establishment of the fuel cut condition to the stop of the vehicle. The position of the piston of any cylinder 1, that is, the crank angle is shown. In the figure, for convenience, the crank angle of 0 ° (720 °) is the exhaust top dead center of the corresponding cylinder 1.

  In this embodiment, in various operating conditions, the rotational speed α when the fuel cut condition is executed, the speed decrease speed θ during the fuel cut that appears as a gradient of the rotational speed, and the opening operation of the electronic throttle valve 32 are absorbed. The ECU 0 stores a correlation between a parameter such as an air responsiveness β that is a time lag until the pressure rise is affected and a valve opening timing x at which the electronic throttle valve 32 is opened as a map in advance. Data constituting such a map may be stored at the adaptation stage for manufacturing the vehicle, or may be stored by learning from various driving conditions of the vehicle. Of course, these data may be appropriately rewritten when the vehicle is driven.

  First, when the fuel cut flag is turned on due to the establishment of the fuel cut condition, the fuel cut is executed at a slightly delayed timing as described above, and the rotational speed is thereby lowered. Then, in the predetermined period y after the descent starts, the above-described parameters α, θ, β are read from the map, and the valve opening timing x set within the determination period z is determined. The valve opening timing x is determined in consideration of the predetermined time y as well.

  In the figure, once the electronic throttle valve 32 is opened, the degree of decrease in the rotational speed once becomes slow, because the pump loss of each cylinder 1 is reduced by opening the valve. Thereafter, when the rotation speed continues to decrease and the rotation of the internal combustion engine stops, that is, reaches 0 rpm, it stops at the exhaust top dead center.

  Further, the intake pressure continues to rise gradually from the opening timing x of the electronic throttle valve 32 through the air response β, that is, the response delay time. In this embodiment, the electronic throttle valve 32 is closed when it is detected from the intake pressure signal e that the intake pressure becomes atmospheric pressure.

  Thereby, at the time of restart after the vehicle stops, any cylinder 1 is positioned at the exhaust top dead center, and the intake pressure is adjusted to atmospheric pressure. That is, at the time of restart, since any cylinder 1 starts from the intake stroke and the intake pressure is adjusted to the atmospheric pressure, the fuel injection amount corresponding to the intake amount corresponding to the atmospheric pressure can be accurately specified. In addition, the air-fuel mixture can be quickly introduced into the cylinder 1. As a result, a stable start in which the increase in the rotational speed is suppressed at the time of start-up is quickly realized.

  By doing so, in the present embodiment, the rotational speed α at the time of fuel cut execution, the speed of decrease in rotational speed θ, and the air responsiveness β, which are parameters that affect the operation of the piston when the fuel cut condition is satisfied, are taken into account. In addition, since the electronic throttle valve 32 is opened, the piston is stopped at a desired position regardless of variations in the behavior of the rotational speed at the start of fuel cut. As a result, the cylinder 1 can be restarted after the state in which the cylinders 1 are always aligned. In other words, during restart, it becomes easy to perform various controls for performing reliable start while suppressing fuel injection, so that excessive increase in the number of revolutions during start-up can be effectively avoided, contributing to improved fuel efficiency. Yes.

  The present invention is not limited to the embodiment described in detail above. The specific configuration of each part can be variously modified without departing from the spirit of the present invention.

  For example, in the above embodiment, the rotational speed at the time of fuel cut is taken into account as a parameter for determining the valve opening timing of the throttle valve. However, the degree of decrease in the rotational speed and the air responsiveness without taking into account the rotational speed. It is good also as an aspect which determines valve opening timing by. Moreover, although the aspect which applied the electronic throttle valve was disclosed in the said embodiment, of course, you may provide the idle speed control valve in the bypass channel provided before and behind the throttle valve. In this case, the valve opening timing of either or both valves is determined. Further, specific modes of the fuel cut condition and the idling stop condition are not limited to those of the above-described embodiment, and various modes including the existing ones can be applied.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  The present invention can be used as a control device for an internal combustion engine that performs fuel cut when a predetermined condition is satisfied.

0 ... Control device (ECU) for internal combustion engine
32 ... Electronic throttle valve α ... Rotational speed θ ... Speed of decrease in rotational speed β ... Air responsiveness x ... Opening timing

Claims (1)

A fuel cut that stops fuel injection when the fuel cut condition is satisfied, and when the vehicle stops without performing fuel injection from the execution of the fuel cut, the rotation of the internal combustion engine is stopped before the vehicle stops Because
Air response that is the time lag until the speed of the internal combustion engine when the fuel cut condition is satisfied, the speed at which the speed of the internal combustion engine during the fuel cut is decreasing, and the opening operation of the throttle valve affects the intake pressure rise based on gender, with the piston determining the timing for opening the throttle valve in order to stop at a desired position, the control apparatus for an internal combustion engine that closes the throttle valve opens When the intake pressure becomes the atmospheric pressure.

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