JP2013160198A - Device and method for controlling internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely start fuel cut before the lapse of time fixed in advance from turning-off of an accelerator in a torque base type internal combustion engine controlled in output torque according to target torque.SOLUTION: Target torque Trof* of an engine during turning-off of an accelerator is set so that engine speed is gradually lowered and the target torque does not exceed upper limit guard toque Tug which is sequentially set. When the target torque Trof* is lowered to fuel cut permission torque Tfc, fuel cut is started. The upper limit guard torque Tug is gradually lowered so that the upper limit guard torque is lowered from an initial value T0 set at a point of time of turning-off of the accelerator to the fuel cut permission torque Tfc when a target fuel cut time tf elapses.

Description

  The present invention relates to a control device and a control method for an internal combustion engine, and more particularly to control for stopping fuel supply when an accelerator is off (hereinafter referred to as “fuel cut control”).

  Engine control for improving fuel efficiency by fuel cut control when the accelerator pedal is off is known.

  For example, Japanese Patent Laid-Open No. 2009-299667 (Patent Document 1) describes fuel cut control in a so-called torque demand type engine in which an actuator of an engine is controlled based on a required torque. Specifically, when the fuel cut permission condition is satisfied, the target torque is gradually decreased to the minimum torque, and the fuel supply is stopped after the output torque of the internal combustion engine has decreased to the minimum torque. Is described.

  Japanese Patent Application Laid-Open No. 3-194138 (Patent Document 2) discloses a method for controlling engine control torque, in which fuel cut or engine torque reduction during engine brake operation is determined as travel state quantities (travel speed, engine speed). , Gear position, presence / absence of lateral acceleration, friction value of tire of driving wheel, presence / absence of tire slip).

  Japanese Patent Laid-Open No. 2007-292031 (Patent Document 3) discloses that in torque-based engine control, when the engine speed increases rapidly, the target torque is decreased while the engine speed increases rapidly. In this case, torque control for canceling vehicle longitudinal vibration is described by increasing the target torque when the torque decreases to the above.

JP 2009-299667 A JP-A-3-194138 JP 2007-292031 A

  In the engine torque control described in Patent Document 3, there is a scene in which the torque is increased to cancel the vehicle longitudinal vibration even when the accelerator is off. For this reason, in application of fuel cut control like patent documents 1, there is a possibility that the start of fuel cut may be delayed because the target torque at the time of accelerator off does not fall. If the time from the accelerator off to the start of the fuel cut becomes longer than expected, the fuel efficiency may deteriorate from the design value.

  The present invention has been made to solve such problems, and an object of the present invention is predetermined when the accelerator is off in a torque-based internal combustion engine in which the output torque is controlled according to the target torque. It is to realize the control to start the fuel cut surely within the predetermined time.

  In one aspect of the present invention, an internal combustion engine control device includes setting means, output control means, and fuel cut control means. The setting means sets a target torque of the internal combustion engine when the accelerator is off. The output control means generates a control signal for the actuator so as to control the output torque of the internal combustion engine according to the target torque. The fuel cut control means starts the fuel cut of the internal combustion engine when the target torque decreases to the fuel cut permission torque when the accelerator is off. The setting means includes an upper limit guard setting means for setting an upper limit guard torque of the target torque, and a guard means for limiting the target torque so as not to exceed the upper limit guard torque. The upper limit guard setting means gradually decreases the upper limit guard torque so that the upper limit guard torque decreases to the fuel cut permission torque when a predetermined time has elapsed from the time when the accelerator is off.

  Preferably, the setting means includes means for setting the target torque so as to include a compensation component for controlling the rotation speed change rate of the internal combustion engine or the deceleration of the vehicle to be constant.

  Preferably, the upper limit guard setting means sets an initial value of the upper limit guard torque according to the output torque at that time when the accelerator is off, and gradually lowers the upper limit guard torque to the fuel cut permission torque over a predetermined time. Let

  Alternatively, preferably, the fuel cut permission torque decreases as the rotational speed of the internal combustion engine decreases.

  In one aspect of the present invention, an internal combustion engine control method configured to control an output torque according to a target torque at least when the accelerator is off includes a step of setting the target torque when the accelerator is off, and an upper limit guard torque of the target torque. A setting step, a step of limiting the target torque so as not to exceed the upper limit guard torque, and a step of starting a fuel cut of the internal combustion engine when the target torque decreases to a fuel cut permission torque when the accelerator is off. Then, the step of setting the upper limit guard torque includes a step of gradually lowering the upper limit guard torque so that the upper limit guard torque is reduced to the fuel cut permission torque when a predetermined time has elapsed from the time when the accelerator is off.

  Preferably, the step of setting the target torque includes the step of setting the target torque so as to include a compensation component for controlling the speed change rate of the internal combustion engine or the deceleration of the vehicle to be constant.

  According to the present invention, in a torque-based internal combustion engine in which the output torque is controlled according to the target torque, the fuel cut can be reliably started before a predetermined time elapses after the accelerator is turned off.

It is a figure which shows the structural example of the engine controlled by the control apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the structure of the control apparatus of the internal combustion engine which concerns on embodiment of this invention. It is a functional block diagram explaining the structure of the target torque setting part shown in FIG. 2 further in detail. It is a wave form diagram which shows the operation example of the fuel cut control by the control apparatus of the internal combustion engine which concerns on embodiment of this invention. It is a flowchart for demonstrating the fuel cut start processing procedure by the control apparatus of the internal combustion engine which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

  FIG. 1 is a diagram illustrating a configuration example of an engine which is a control target of the control device according to the present embodiment.

  Referring to FIG. 1, an engine 10 is configured such that a cylinder head 110 abuts above a cylinder block 100, and a piston 120 is slidably held in a cylinder 102 formed in the cylinder block 100. ing. The reciprocating motion of the piston 120 in the cylinder 102 is converted into the rotational motion of the crankshaft 130 and transmitted to a transmission or the like. The crankshaft 130 is connected to the starter 30 via the flywheel 140 when the engine is started. In FIG. 1, the engine 10 is illustrated as a four-cylinder engine having four cylinders 102, but the number of cylinders 102 (the number of cylinders) is not limited to this example.

  A combustion chamber 1000 is formed above the piston 120 using the cylinder block 100 and the cylinder head 110 as chamber walls. When the mixture of fuel and air is burned in the combustion chamber 1000, the piston 120 reciprocates up and down by the explosive force. The air-fuel mixture is ignited by a spark plug 150 that passes through the cylinder head 110 and projects into the combustion chamber 1000.

  Supply of air constituting the air-fuel mixture is performed by an intake port 1012 formed in the cylinder head 110 and an intake passage 1010 connected to the intake port 1012. Further, exhaust from the combustion chamber 1000 is performed by an exhaust passage 1020. The cylinder head 110 includes an intake valve 160 for switching communication / blocking between the intake port 1012 (intake passage 1010) and the combustion chamber 1000, and an exhaust valve 170 for switching communication / blocking between the exhaust passage 1020 and the combustion chamber 1000. Is attached.

  A flap-like throttle valve 190 is provided in the intake passage 1010. The air flow rate in the intake passage 1010 is adjusted according to the opening degree of the throttle valve 190 (throttle opening degree).

  The fuel constituting the mixture is supplied by an electromagnetic injector 210. The injector 210 is provided so as to penetrate the cylinder head 110, and is provided so as to inject fuel from the tip nozzle portion into the intake port 1012. A mixture of the fuel injected from the injector 210 and the intake air from the intake passage 1010 is introduced into the combustion chamber 1000 when the intake valve 160 is opened. The injector 210 may be provided so as to inject fuel directly into the combustion chamber 1000 or to inject fuel into both the combustion chamber 1000 and the intake port 1012.

  The spark plug 150, the throttle valve 190, and the injector 210 are configured to operate in response to control signals from an ECU (Electronic Control Unit) 8000 that controls each part of the engine.

The ECU 8000 has a general configuration including a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), an A / D converter, and various drive circuits (drivers).

  ECU 8000 controls the operation of an actuator for controlling the output of engine 10 based on detection signals from various sensors. As the actuator, a spark plug 150, a throttle valve 190, an injector 210, and the like are provided. Specifically, ECU 8000 outputs a control signal to spark plug 150 to adjust the ignition timing, and outputs a control signal to throttle valve 190 to adjust the opening of throttle valve 190 (throttle opening). A control signal is output to 210 and the nozzle of the injector 210 is opened for a predetermined time at a predetermined timing.

  Sensors that input signals to the ECU 8000 include a flow meter 510, a crank angle sensor 520, an A / F sensor 530, an intake air temperature sensor 540, a cooling water temperature sensor 550, a vehicle speed sensor 560, and an accelerator opening sensor 570.

  The flow meter 510 detects the flow rate of air flowing through the intake passage 1010 (intake air amount QA). The crank angle sensor 520 detects the rotational angle (crank angle) CA of the crankshaft 130 and the rotational speed (engine rotational speed) NE per unit time. The A / F sensor 530 detects the air fuel efficiency A / F of the exhaust passage 1020. The intake air temperature sensor 540 detects the temperature (intake air temperature) THA of the air flowing through the intake passage 1010. Cooling water temperature sensor 550 detects engine water temperature THW. Vehicle speed sensor 560 detects vehicle speed V from the rotational speed of a drive shaft (not shown). The accelerator opening sensor 570 detects an accelerator pedal opening (accelerator opening) ACC. Each of these sensors transmits a signal representing the detection result to ECU 8000.

  ECU 8000 cranks engine 10 by starter 30 when there is a request to start engine 10 from the driver. Alternatively, when the engine 10 is mounted on a hybrid vehicle, a vehicle having an idle stop function, or the like, the start request for the engine 10 may be automatically generated according to the vehicle state.

  ECU 8000 starts combustion of engine 10 by controlling the fuel injection amount, fuel injection timing, and ignition timing based on signals from each sensor at a predetermined timing during cranking. With these controls, the engine 10 is in an optimal combustion state, and the engine 10 can have high output and low emission.

  The control device for an internal combustion engine according to the present embodiment sets the target torque of the engine 10 according to the traveling state at least when the accelerator is off, preferably during traveling, and the engine output torque is set to the target torque. Actuator operation is controlled to match. That is, it is assumed that torque-based engine control is executed for engine 10 at least when the accelerator is off.

  Further, the ECU 8000 supplies fuel from the injector 210 to the engine 10 when the accelerator opening degree ACC becomes substantially zero (when the accelerator pedal is off) in a state where the vehicle speed V is higher than a predetermined speed in order to improve fuel efficiency. Execute fuel cut control to stop. Further, ECU 8000 stops fuel cut control and resumes fuel supply from injector 210 to engine 10 when a predetermined fuel cut return condition is satisfied during execution of fuel cut control.

  The control apparatus for an internal combustion engine according to the present embodiment is characterized by control from when the accelerator pedal is turned off until fuel cut is started. Therefore, hereinafter, the control behavior in a vehicle state in which the fuel cut permission condition is satisfied when the accelerator pedal is turned off will be described. Hereinafter, turning off the accelerator pedal in such a state is also simply referred to as “accelerator off”.

  FIG. 2 is a schematic block diagram showing a configuration of ECU 8000 which is a control device for the internal combustion engine according to the embodiment of the present invention.

  ECU 8000 includes an input interface (input I / F) 8100, an arithmetic processing unit 8200, a storage unit 8300, and an output interface (output I / F) 8400.

  The input I / F 8100 includes an intake air amount QA from the flow meter 510, a crank angle CA and an engine speed NE from the crank angle sensor 520, an air fuel consumption A / F from the A / F sensor 530, and an intake air temperature sensor 540. The intake air temperature THA, the engine water temperature THW from the cooling water temperature sensor 550, the vehicle speed V from the vehicle speed sensor 560, and the accelerator opening ACC from the accelerator opening sensor 570 are received and transmitted to the arithmetic processing unit 8200.

  Various information, programs, threshold values, maps, and the like are stored in the storage unit 8300, and data is read from or stored in the arithmetic processing unit 8200 as necessary.

  The arithmetic processing unit 8200 has a plurality of functional blocks that indicate control functions realized by the arithmetic processing. In the example illustrated in FIG. 2, the arithmetic processing unit 8200 includes an output control unit 8210, a target torque setting unit 8250, and a fuel cut control unit 8260. Output control unit 8210 includes a fuel injection control unit 8220, an ignition timing control unit 8230, and an intake air amount control unit 8240.

  FIG. 2 representatively shows only functional blocks corresponding to some of the functions related to the fuel cut control according to the present embodiment, among the control functions realized in engine control by ECU 8000. ing. Each illustrated functional block is described as functioning as software that is realized by the CPU that is the arithmetic processing unit 8200 executing a program stored in the storage unit 8300, but is realized by hardware. You may make it do. Such a program is recorded on a storage medium and mounted on the vehicle.

  Target torque setting unit 8250 sets target torque Trof * of engine 10 when the accelerator is off.

  The output control unit 8210 controls the actuator of the engine 10 based on the target torque Trof * at least when the accelerator is off. For example, the fuel injection control unit 8220, the ignition timing control unit 8230, and the intake air amount control unit 8240 control the fuel injection, the ignition timing, and the intake air amount so that the output torque of the engine 10 becomes the target torque Trof *. .

  In an engine to which so-called torque demand control is applied, the target torque setting unit 8250 always sets the target torque of the engine 10 according to the vehicle state and the driver's operation even during traveling other than when the accelerator is off. In that case, the output control unit 8210 constantly controls the actuator of the engine 10 on a torque basis so that the target torque is achieved.

  The fuel injection control unit 8220 calculates a fuel injection amount and fuel injection timing for obtaining a necessary engine output, and generates a fuel injection control signal corresponding to the calculation result. The fuel injection control signal is output to the injector 210 to be injected via the output I / F 8400. Thereby, the fuel according to a fuel-injection control signal is injected from the injector 210 which should inject fuel. The fuel injection control unit 8220 calculates the fuel injection amount and the fuel injection timing according to the target torque Trof * set by the target torque setting unit 8250 when the accelerator is off.

  The ignition timing control unit 8230 calculates an ignition timing for obtaining a necessary engine output, and generates an ignition timing control signal corresponding to the calculation result. The ignition timing control signal is output to each spark plug 150 via the output I / F 8400. Thereby, the air-fuel mixture in the combustion chamber 1000 is ignited by the spark plug 150 at a timing according to the ignition timing control signal. The ignition timing control unit 8230 calculates the ignition timing according to the target torque Trof * set by the target torque setting unit 8250 when the accelerator is off.

  The intake air amount control unit 8240 calculates a necessary intake air amount and generates a throttle valve control signal according to the calculated intake air amount. The throttle valve control signal is output to the throttle valve 190 via the output I / F 8400. Thus, the calculated intake air amount flows into the intake passage 1010 by adjusting the throttle opening. The intake air amount control unit 8240 calculates the intake air amount according to the target torque Trof * set by the target torque setting unit 8250 when the accelerator is off.

  The fuel cut control unit 8260 controls the start / end of the fuel cut based on the vehicle state and the target torque Trof * when the accelerator is off. While the fuel cut is being executed, the flag FC is turned on, while when the fuel cut is not being executed, the flag FC is turned off. When executing the fuel cut, the fuel injection control unit 8220 generates a fuel injection control signal so as to stop the fuel injection from the injector 210.

  Further, the fuel cut control unit 8260 stops the fuel cut control and restarts the fuel supply from the injector 210 to the engine 10 when a predetermined fuel cut return condition is satisfied during execution of the fuel cut.

  Fuel cut control in the control apparatus for an internal combustion engine according to the present embodiment will be described in detail with reference to FIGS.

  FIG. 3 is a functional block diagram for explaining the configuration of the target torque setting unit 8250 in more detail.

  Referring to FIG. 3, target torque setting unit 8250 includes a drive-off torque calculation unit 8252, a fuel cut permission torque calculation unit 8253, an upper limit guard torque setting unit 8254, and an upper limit guard processing unit 8256.

  The drive-off torque calculation unit 8252 calculates a drive-off torque Trof that is a basic value of the target torque when the accelerator is off. The initial value of the drive-off torque Trof is set based on the engine torque TE at the accelerator-off time. Thereafter, the drive-off torque Trof is sequentially calculated so as to decrease the engine speed NE at a constant rate.

  The fuel cut permission torque calculation unit 8253 calculates a fuel cut permission torque Tfc that is a torque threshold value for starting fuel cut when the accelerator is off. The fuel cut permission torque Tfc is sequentially calculated according to the engine speed NE and the shift position (gear stage).

  Upper limit guard torque setting unit 8254 sequentially sets upper limit guard value Tug (hereinafter also referred to as upper limit guard torque) of target torque Trof * when accelerator is off, based on fuel cut permission torque Tfc and target fuel cut time tf.

  The upper limit guard processing unit 8256 sets the target torque Trof so as not to exceed the upper limit guard torque Tug based on the comparison between the drive-off torque Trof and the upper limit guard torque Tug. Specifically, when Trof ≦ Tug, Trof * = Trof is set, while when Trof> Tug, Trof * = Tug is set.

  FIG. 4 shows an example of an operation waveform of fuel cut control, in particular, setting of the target torque Trof * from the accelerator off to the start of fuel cut.

  Referring to FIG. 4, when the driver turns off the accelerator pedal at time t0, an initial value T0 of drive-off torque Trof is set based on engine torque TE at that time. For example, the relationship between the engine torque TE and the initial value T0 when the accelerator is off is preset by a map.

  When the accelerator is off, the drive-off torque Trof is set so that the amount of change NER per unit time (hereinafter also referred to as the change rate NER) of the engine speed NE is controlled to the target value NER *. The target value NER * is a negative value because it is during deceleration due to accelerator off.

  As a result, the drive-off torque Trof generally decreases to the right according to the inclination corresponding to the target value NER *. Preferably, feedback control for adjusting the drive-off torque Trof is executed in accordance with the change rate deviation ΔNER (ΔNER = NER−NER *). As a result, as shown in the example of FIG. 4, a compensation amount for controlling the change rate NER to the target value NER * to be constant appears as an AC component of the target torque Trof *. As a result, by controlling the engine speed change rate NER to be constant, the amount of decrease in vehicle speed per unit time (that is, vehicle deceleration) can be controlled to be constant, thereby improving drivability during deceleration. In order to more precisely control the deceleration of the vehicle, the target value NER * may be adjusted during deceleration without being a constant value.

  Thus, when the accelerator is off, the target torque Trof * decreases with time. Then, the fuel cut control unit 8260 sequentially compares the target torque Trof * and the fuel cut permission torque Tfc, and starts the fuel cut from the time when Trof * <Tfc.

  The fuel cut permission torque Tfc is adjusted in advance corresponding to the engine speed NE as a torque value that does not cause a shock even when the fuel cut is started. For example, a map for setting the fuel cut permission torque Tfc with respect to the engine speed NE for each shift position (gear stage) is created in advance based on experimental results and the like. Then, the fuel cut permission torque calculation unit 8253 sequentially sets the fuel cut permission torque Tfc by referring to the map according to the shift position (gear stage) and the engine speed NE at each time point.

  When the engine speed is high, the fuel cut permission torque Tfc is set to a high value because the shock is hardly detected even when the fuel cut is started with a relatively high torque. As shown in FIG. 4, the fuel cut permission torque Tfc is gradually reduced as the engine speed NE decreases.

  The target torque Trof * needs to be set within a range from the minimum torque Tmin calculated corresponding to the misfire limit torque to the maximum torque Tmax calculated corresponding to MBT (Minimum Advance for Best Torque). . Further, in the present embodiment, an upper limit guard torque Tug lower than the maximum torque Tmax is provided. Then, an upper limit guard process is performed to limit the target torque Trof * when the accelerator is off so as not to exceed the upper limit guard torque Tug.

  The initial value of the upper limit guard torque Tug at the time when the accelerator is off is set to the maximum torque Tmax at that time. Thereafter, the upper limit guard torque Tug is sequentially updated according to the following equation (1), reflecting the fuel cut permission torque Tfc and the target fuel cut time tf.

Tug (t) = Tug (t−Δt) − (Tug (t−Δt) −Tfc (t)) / (tf−t) (1)
In the equation (1), Tug (t) is the upper limit guard torque Tug at the time when the time t has elapsed from the accelerator off time (time t0). Since Δt represents the calculation period of the upper limit guard torque Tug, Tug (t−Δt) is the previous value of the upper limit guard torque Tug. Tfc (t) is fuel cut permission torque Tfc at time t.

  The target fuel cut time tf is a target value of the elapsed time from the accelerator off to the start of fuel cut. The target fuel cut time tf is determined in advance according to the shift position (gear stage). For example, in a gear stage having a large driving force change such as the first speed, if fuel cut is performed at an early stage, drivability may be reduced due to fluctuations in engine output. For this reason, it is preferable that the target fuel cut time tf is set to be long at a low gear and is set to be short at a high gear.

  According to the equation (1), the upper limit guard torque Tug can be gradually decreased so as to reach the fuel cut permission torque Tfc when the target fuel cut time tf has elapsed from the accelerator off time (time t0). Understood.

  In the example of FIG. 4, at time t1 when the target fuel cut time tf has elapsed from time t0, the drive-off torque Trof is higher than the fuel cut permission torque Tfc. For this reason, when the upper limit guard process by the upper limit guard torque Tug is not introduced, the fuel cut cannot be started from the time t1. Thus, there is a possibility that fuel consumption may deteriorate due to the start of fuel cut being delayed from the expected time.

  On the other hand, in the fuel cut control according to the present embodiment, the target torque Trof * is reliably obtained up to the fuel cut permission torque Tfc when the target fuel cut time tf has elapsed from the accelerator off by the upper limit guard process using the upper limit guard torque Tug. It has dropped to. As a result, fuel cut can be reliably started when the target fuel cut time tf elapses, and fuel efficiency can be improved.

  In FIG. 2, the target torque setting unit 8250 corresponds to “setting unit”, and the output control unit 8210 corresponds to “output control unit”. In FIG. 3, the upper limit guard torque setting unit 8254 corresponds to “upper limit guard setting unit”, and the upper limit guard processing unit 8256 corresponds to “guard unit”. Furthermore, the drive off torque calculation unit 8252 can set the target torque so as to include a compensation component for controlling the engine speed change rate to be constant.

  FIG. 5 shows a fuel cut start processing procedure by the control apparatus for an internal combustion engine according to the embodiment of the present invention. The control process according to the flowchart shown in FIG. 5 is repeatedly executed by ECU 8000 every predetermined control period when fuel cut is not executed.

  Referring to FIG. 5, ECU 8000 detects that the accelerator pedal is turned off as a fuel cut permission condition in step S100. For example, when the vehicle speed is higher than a predetermined value and the condition that allows fuel cut is satisfied by turning off the accelerator pedal, step S100 is determined as YES.

  On the other hand, when conditions for permitting fuel cut are not satisfied, including when the accelerator pedal is not turned off, ECU 8000 determines that step S100 is NO and does not execute subsequent processing related to fuel cut control.

  ECU 8000 sets drive-off torque Trof in step S110 when the accelerator is off (when YES is determined in S100). As described above, the drive-off torque Trof is set so as to control the engine speed change rate NER. That is, the processing in step S110 corresponds to the function 8252 of the drive-off torque calculation unit in FIG.

  Further, ECU 8000 sets fuel cut permission torque Tfc in step S120. As described above, fuel cut permission torque Tfc is determined based on the shift position (gear stage) and engine speed NE. That is, the process of step S120 corresponds to the function of 8253 of the fuel cut permission torque calculation unit in FIG.

  ECU 8000 sets upper limit guard torque Tug in step S130. The upper limit guard torque Tug is sequentially set according to the above equation (1) so that Tug = Tfc when the target fuel cut time tf elapses from the accelerator off time. The process of step S130 corresponds to the function of the upper limit guard torque setting unit 8254 in FIG.

  In step S140, ECU 8000 sets a target torque Trof * when the accelerator is off by an upper limit guard process according to the upper limit guard torque Tug set in step S130. Thus, the target torque Trof * is set within a range not exceeding the upper limit guard torque Tug based on the drive-off torque Trof. The processing in step S150 corresponds to the function of the upper limit guard processing unit 8256 in FIG.

  In step S150, ECU 8000 compares target torque Trof * set in step S140 with fuel cut permission torque Tfc set in step S120. When Trof * <Tfc (when YES is determined in S150), ECU 8000 advances the process to step S160 and starts fuel cut.

  On the other hand, when Trof *> Tfc (when NO is determined in S150), ECU 8000 advances the process to step S170 and maintains the fuel cut not being executed. That is, the fuel cut is not started.

  As described above, according to the control of the internal combustion engine according to the present embodiment, by providing the upper limit guard torque when the accelerator is off, the target torque can be reliably ensured until the predetermined time (target fuel cut time tf) elapses from the accelerator off. Trof * can be reduced to the fuel cut permission torque Tfc. As a result, fuel cut can be reliably started before a predetermined time has elapsed since the accelerator was turned off, so that fuel efficiency can be improved.

  In particular, in order to improve drivability during deceleration, even when the target torque Trof * when the accelerator is off is set so as to control the engine speed change rate NER to the target value, the fuel cut is surely started. It becomes possible. That is, it is possible to improve drivability during deceleration without deteriorating fuel consumption.

  The control of the internal combustion engine according to the present embodiment can be applied to an engine configured to control an actuator according to a target torque. Therefore, typically, the fuel cut control according to the present embodiment can be applied to torque demand type engine control. In addition, since the present invention relates to the control from the accelerator off to the start of the fuel cut, even if the vehicle does not perform the engine control with the target torque set during normal driving, the torque-based engine control is limited to the time when the accelerator is off. By performing the above, it is possible to apply the fuel cut control according to the present embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be used for control of an internal combustion engine having a fuel cut function.

  10 engine, 30 starter, 100 cylinder block, 102 cylinder, 110 cylinder head, 120 piston, 130 crankshaft, 140 flywheel, 150 spark plug, 160 intake valve, 170 exhaust valve, 190 throttle valve, 210 injector, 510 flow meter 520 Crank angle sensor, 530, 540 sensor, 550 Cooling water temperature sensor, 560 Vehicle speed sensor, 570 Accelerator opening sensor, 1000 Combustion chamber, 1010 Intake passage, 1012 Intake port, 1020 Exhaust passage, 8100 Input I / F, 8200 Processing unit, 8210 Output control unit, 8220 Fuel injection control unit, 8230 Ignition timing control unit, 8240 Intake air amount control unit, 8250 Target torque setting unit, 8252 Drive Torque calculation unit, 8253 fuel cut permission torque calculation unit, 8254 upper limit guard torque setting unit, 8256 upper limit guard processing unit, 8260 fuel cut control unit, 8300 storage unit, 8400 output I / F, CA crank angle, NE engine speed, NER engine speed change rate, NER * target value (engine speed change rate), QA intake air amount, T0 initial value (drive-off torque), TE engine torque, THA intake air temperature, THW engine water temperature, Tfc Fuel cut permission Torque, Tmax maximum torque, Tmin minimum torque, Trof * target torque (when accelerator is off), Trof drive off torque, Tug upper limit guard torque, tf target fuel cut time.

Claims (8)

Setting means for setting a target torque of the internal combustion engine when the accelerator is off;
Output control means for generating an actuator control signal to control the output torque of the internal combustion engine according to the target torque;
A fuel cut control means for starting a fuel cut of the internal combustion engine when the target torque decreases to a fuel cut permission torque when the accelerator is off;
The setting means includes
Upper limit guard setting means for setting an upper limit guard torque of the target torque;
Guard means for limiting the target torque so as not to exceed the upper limit guard torque,
The upper limit guard setting means controls the internal combustion engine to gradually reduce the upper limit guard torque so that the upper limit guard torque decreases to the fuel cut permission torque when a predetermined time has elapsed from the time when the accelerator is off. apparatus.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the setting means includes means for setting the target torque so as to include a compensation component for controlling the rotation speed change rate of the internal combustion engine to be constant.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the setting means includes means for setting the target torque so as to include a compensation component for controlling the deceleration of the vehicle to be constant.   The upper limit guard setting means sets an initial value of the upper limit guard torque according to the output torque at that time when the accelerator is off, and gradually increases the upper limit guard torque to the fuel cut permission torque over the predetermined time. The control device for an internal combustion engine according to claim 1, wherein   The control device for an internal combustion engine according to claim 1, wherein the fuel cut permission torque decreases as the rotational speed of the internal combustion engine decreases. A control method for an internal combustion engine configured to control an output torque according to a target torque at least when an accelerator is off,
Setting the target torque when the accelerator is off;
Setting an upper limit guard torque of the target torque;
Limiting the target torque so as not to exceed the upper limit guard torque;
A step of starting fuel cut of the internal combustion engine when the target torque decreases to a fuel cut permission torque when the accelerator is off,
The step of setting the upper limit guard torque includes a step of gradually lowering the upper limit guard torque so that the upper limit guard torque is reduced to the fuel cut permission torque when a predetermined time has elapsed from the time when the accelerator is turned off. A control method for an internal combustion engine.   The method for controlling an internal combustion engine according to claim 6, wherein the step of setting the target torque includes the step of setting the target torque so as to include a compensation component for controlling the rate of change of the rotation speed of the internal combustion engine to be constant. .   The internal combustion engine control method according to claim 6, wherein the step of setting the target torque includes the step of setting the target torque so as to include a compensation component for controlling the deceleration of the vehicle to be constant.

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