JP5313819B2 - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which can be favorably restarted even when a restart condition is established during inertial rotation of an internal combustion engine immediately after being automatically stopped. <P>SOLUTION: In an automatically stopped state of an internal combustion engine, fuel pressure is controlled to be higher than that during operation. When a restart condition is established, the first fuel injection is forced to be executed with respect to a cylinder stopped in an opened state of an intake valve during halts, thereby enhancing combustibility at the first fuel injection. While the internal combustion engine immediately after establishing the automatic stop condition is rotated by inertia (a transition period to a halt), fuel pressure is gradually increased as rotation speed is reduced so as to suppress setting with excessively high fuel pressure during inertial rotation. Thus, the startability with respect to a restart request during inertial rotation is enhanced. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a control apparatus for an internal combustion engine that includes an automatic stop unit that stops the internal combustion engine under a predetermined stop condition and restarts the internal combustion engine under a predetermined start condition.

  In Patent Document 1, while the internal combustion engine after the automatic stop is rotating with inertia, the drive of the fuel pump is continued to increase the fuel pressure supplied to the fuel injection valve to the target fuel pressure used at the time of restart. A control device for controlling the above is disclosed.

JP 2006-348908 A

  By the way, if the internal combustion engine immediately after the automatic stop is rotating with inertia, the restart condition is satisfied, and if the actual fuel pressure at that time has increased to the vicinity of the target fuel pressure used at the time of restart, Although the engine is rotating due to inertia and not stopped, fuel injection is performed at a pressure suitable for restarting from a state where the engine rotation is stopped. There was a problem that the combustibility at the time was reduced and the restartability was deteriorated.

  The present invention has been made in view of the above problems, and provides a control device for an internal combustion engine that can be restarted satisfactorily even if a restart condition is satisfied while the internal combustion engine immediately after an automatic stop is rotating with inertia. The purpose is to do.

Therefore, in the present invention, the fuel pressure supplied to the fuel injection valve is set higher than during operation while the internal combustion engine is stopped by the automatic stop means, while the internal combustion engine is actually started from the start of the automatic stop processing of the internal combustion engine. in stop transition period until the rotation is stopped, and as the fuel pressure becomes higher in accordance with the engine rotational speed range lower than the requested value in the stop is reduced.

  According to the above invention, even if a restart request is generated during the stop transition period, good restartability can be obtained with an appropriate fuel pressure.

1 is an overall configuration diagram showing an embodiment of an internal combustion engine to which a control device according to the present invention is applied. It is a block diagram which shows the fuel pressure control system of embodiment. It is a graph which shows the change of the open characteristic (valve lift amount VL, valve operation | movement OA, center phase SP) of the intake valve by the variable valve lift mechanism and variable valve timing mechanism of embodiment. It is a flowchart which shows the idle stop control in embodiment. It is a flowchart which shows the fuel pressure control at the time of idle stop control in embodiment. It is a time chart which shows the fuel pressure change at the time of idle stop control in an embodiment. It is a flowchart which shows the estimation process of the temperature of the intake valve in embodiment. It is a flowchart which shows the cylinder discrimination | determination process at the time of the engine stop in embodiment. It is a flowchart which shows the fuel-injection control at the time of the automatic start in embodiment. It is a flowchart which shows the fuel pressure control after the start in embodiment. It is a time chart which shows the fuel pressure change at the time of performing control of FIG. It is a flowchart which shows the valve timing control in embodiment. It is a figure for demonstrating the change of the valve lift by performing control of FIG. It is a time chart which shows the change of valve timing at the time of performing control of Drawing 12. It is a time chart which shows the change of the valve lift amount at the time of performing control of a variable valve lift mechanism in an embodiment.

Embodiments of the present invention will be described below.
FIG. 1 is a system configuration diagram of a vehicle internal combustion engine to which a control device according to the present invention is applied. An internal combustion engine 101 shown in FIG. 1 is an in-line four-cylinder engine, and its output is transmitted via a transmission not shown. Transmitted to the drive wheels of the vehicle.

  In the internal combustion engine 101, an intake pipe 102 for introducing air into each cylinder is provided with an intake air amount sensor 103 such as a hot-wire flow meter for detecting the intake air flow rate QA of the internal combustion engine 101.

An intake valve 105 for opening and closing the intake port of the combustion chamber 104 of each cylinder is provided, and a fuel injection valve 106 is arranged for each cylinder in the intake pipe 102 upstream of the intake valve 105.
The fuel injected from the fuel injection valve 106 is sucked together with air into the combustion chamber 104 through the intake valve 105, and the fuel in the combustion chamber 104 is ignited and burned by spark ignition by the spark plug 107, and the combustion When the pressure pushes down the piston 108 toward the crankshaft 109, the crankshaft 109 is rotationally driven.

An exhaust valve 110 that opens and closes the exhaust port of the combustion chamber 104 is provided. When the exhaust valve 110 is opened, exhaust gas in the combustion chamber 104 is discharged to the exhaust pipe 111.
A catalytic converter 112 is interposed in the exhaust pipe 111, and the exhaust gas is purified by the catalytic action of the catalytic converter 112 and discharged.

The intake valve 105 and the exhaust valve 110 are opened and closed by the rotation of a camshaft that is rotationally driven via a crankshaft 109.
The exhaust valve 110 opens and closes at a constant valve lift amount, valve operating angle, and valve timing. The maximum valve lift amount, valve operating angle, and valve timing of the intake valve 105 are controlled by the variable valve lift mechanism 113 and the variable valve. The timing mechanism 114 (variable valve mechanism) can be changed.

  The variable valve lift mechanism 113 is a mechanism for continuously changing the valve lift amount (maximum valve lift amount) and the valve operating angle (the valve opening period angle) of the intake valve 105, and the variable valve timing mechanism 114 is This is a mechanism that changes the central phase of the valve operating angle of the intake valve 105 by changing the rotational phase of the intake camshaft 115 with respect to the crankshaft 109.

  Each of the spark plugs 107 is provided with an ignition module 116 that supplies ignition energy to the spark plug 107. The ignition module 116 includes an ignition coil and a power transistor that controls energization of the ignition coil.

  Further, as shown in FIG. 2, the fuel injection valve 106 provided for each cylinder is connected to a fuel gallery pipe 141, and fuel in the fuel tank 142 is connected to the fuel gallery pipe 141 by an electric fuel pump. 143 is pumped.

  The fuel pressure in the fuel gallery pipe 141, that is, the fuel supply pressure to the fuel injection valve 106 (the fuel injection pressure of the fuel injection valve 106) is detected by the fuel pressure sensor 144, and the actual fuel pressure detected by the fuel pressure sensor 144. The drive current (discharge amount) of the fuel pump 143 is feedback-controlled so that the PF approaches the target fuel pressure PFtg.

  The fuel injection valve 106, the variable valve lift mechanism 113, the variable valve timing mechanism 114, the ignition module 116, and the fuel pump 143 are controlled by the engine control device 201.

  The engine control device 201 includes a microcomputer, inputs signals from various sensors and switches, and performs arithmetic processing according to a program stored in advance, whereby the fuel injection valve 106, variable valve lift The operation amounts of the mechanism 113, the variable valve timing mechanism 114, the ignition module 116, and the fuel pump 143 are calculated and output.

  In the variable valve lift mechanism 113, as shown by an arrow 301 in FIG. 3, the valve operating angle OA of the intake valve 105 and the maximum valve lift amount VL are maintained while the central phase SP of the valve operating angle of the intake valve 105 remains substantially constant. It is a mechanism that continuously changes.

  The engine control device 201 calculates a target valve lift amount according to engine operating conditions (engine load, engine speed, etc.), and based on the deviation between the actual valve lift amount and the target valve lift amount, the variable valve The amount of operation of the lift mechanism 113 is feedback controlled.

  As described above, the variable valve timing mechanism 114 is a mechanism that changes the central phase of the valve operating angle of the intake valve 105 by changing the rotational phase of the intake camshaft 115 with respect to the crankshaft 109. However, there is provided a lock mechanism that mechanically locks at an intermediate position (intermediate phase) of a variable range between the most retarded angle position and the most advanced angle position of the center phase.

  The intermediate phase locked by the locking mechanism is a phase that is more advanced than the most retarded angle position and more retarded than the most advanced angle position, and more specifically, the valve operating angle of the intake valve 105. The center phase (crank angle at which the valve lift is maximized) is a phase that becomes 70 deg to 120 deg after top dead center (ATDC), more preferably a phase that becomes about 90 deg after top dead center (ATDC), which will be described later. Thus, it is a request value for restart from the automatic stop state.

The lock by the lock mechanism is released by a lock release command from the engine control device 201.
The engine control device 201 calculates a target advance amount of the center phase of the valve operating angle of the intake valve 105 based on engine operating conditions (engine load, engine speed, etc.), and outputs of the crank angle sensor 203 and the cam sensor 204. An operation amount of the variable valve timing mechanism 114 based on a deviation between the actual advance amount and the target advance amount so that the actual advance amount detected based on the signal approaches the target advance amount. Feedback control.

  As the variable valve timing mechanism 114, various known variable valve timing mechanisms can be adopted. For example, as disclosed in Japanese Patent Laid-Open No. 2001-050063, the retarded-side hydraulic chamber and the advance angle are sandwiched between vanes. A variable valve timing mechanism that changes the relative rotation phase by controlling the hydraulic pressure of each hydraulic chamber by forming a side hydraulic chamber and a mechanism that rotates the intake camshaft relative to the crankshaft using gears, etc. In addition, a mechanism using an electric motor such as a DC motor or a brushless motor may be used as the actuator.

  The crank angle sensor 203 outputs a position signal POS for each unit crank angle by detecting, with a pickup 203c, protrusions 203b formed at equal intervals on the periphery of a signal plate 203a that is pivotally supported on the crankshaft 109. At the same time, the pickup 203e detects the protrusions 203d formed at two positions on the signal plate 203a at intervals of 180 deg, thereby outputting a reference signal REF for each reference crank angle position of each cylinder.

  The output interval of the reference signal REF corresponds to the ignition interval in the four-cylinder engine in this embodiment, and the reference signal REF is output for each piston position (for example, BTDC 75 deg) of each cylinder.

  Further, the engine control device 201 calculates the rotational speed NE of the internal combustion engine 101 based on the generation period of the reference signal REF or the number of position signals POS generated within a predetermined time.

  On the other hand, the cam sensor 204 outputs the number of cam signals CAM indicating the cylinder number at every generation interval of the reference signal REF, and when the reference signal REF is generated, from the time of generation of the previous reference signal REF to this time. The stroke of each cylinder at that time can be discriminated from the number of cam signals CAM output during this period.

  Further, when the phase of the intake camshaft 115 with respect to the crankshaft 109 is changed by the variable valve timing mechanism 114, the output position of the cam signal CAM relative to the output position of the reference signal REF changes.

  Therefore, for example, by measuring the angle from the generation of the reference signal REF to the generation of the cam signal CAM, the advance amount of the center phase by the variable valve timing mechanism 114 can be detected.

  The generation position of the cam signal CAM is set so that it does not change beyond the generation position of the reference signal REF even if the rotational phase of the intake camshaft 115 is changed by the variable valve timing mechanism 114. .

  The engine control device 201 receives signals from the intake air amount sensor 103, the angle sensor 202, the crank angle sensor 203, and the cam sensor 204, as well as an engine switch (main switch for operating / stopping the internal combustion engine 101). Ignition switch) 205 signal, accelerator pedal 207 opening signal ACC from the accelerator sensor 206, coolant temperature signal (engine temperature signal) TW from the water temperature sensor 208, air-fuel ratio signal AF from the air-fuel ratio sensor 209, vehicle speed sensor A vehicle speed signal VSP from 210 is input.

  The air-fuel ratio sensor 209 is a sensor (oxygen concentration sensor) that is provided in the exhaust pipe 111 and whose output changes in response to the oxygen concentration in the exhaust gas that is closely related to the air-fuel ratio of the internal combustion engine 101.

  The engine control apparatus 201 of the present embodiment includes an idle stop function (function as an automatic stop means) that automatically stops the internal combustion engine 101 under a predetermined stop condition and automatically restarts under a predetermined start condition. In the following, the idle stop function will be described with reference to the flowchart of FIG.

  In the flowchart of FIG. 4, first, in step S501, it is determined whether or not the vehicle is stopped and the internal combustion engine 101 is idling (accelerator fully closed), and the condition of step S501 is satisfied. In step S503, the process proceeds to step S502.

In step S502, it is determined whether the deceleration fuel cut condition is satisfied and the engine speed NE is equal to or lower than a predetermined speed.
The predetermined rotational speed is used to determine the transition from the deceleration fuel cut state of the engine to the idle stop operation. The predetermined rotation speed is set within a range of an idle rotation speed set during idle operation. Further, the maximum rotation speed in a range set as the target idle rotation speed or the fuel restart rotation speed from the fuel cut at the time of engine deceleration may be used. Moreover, you may set as arbitrary engine rotational speeds higher than the target rotational speed at the time of idle driving.

  Accordingly, when the engine speed is lower than the predetermined speed during fuel cut during engine deceleration, it is determined NO in step S502, the process returns, and the processes after step S503 are not performed, and the fuel cut is performed by another fuel injection processing program. And restarting of fuel injection is executed when acceleration is requested.

  On the other hand, in a state where the engine rotational speed decreases to the idle rotational speed after the engine is decelerated during fuel deceleration, a determination of YES is made in step S502, fuel is stopped continuously in step S505, and fuel is cut during deceleration. Since there is a transition from the state to the idle stop state, when there is no acceleration request from the driver, the fuel injection is continuously stopped and the idle stop is performed without restarting the fuel injection. However, it is possible to prevent an unintended increase in rotational speed and a feeling of acceleration, and to shift to idle stop without a sense of incongruity.

If the condition of step S502 is satisfied, the process proceeds to step S503. If the condition is not satisfied, the routine is terminated without automatically stopping the internal combustion engine 101.
In step S503, it is determined whether or not the accelerator is fully closed. If the accelerator is fully closed, the process further proceeds to step S504 to check whether or not the brake pedal is depressed. Judged from the signal from the switch.

  In addition, when the sensor which detects the stroke amount and depression pressure of a brake pedal is provided, when the stroke amount and depression pressure are larger than a threshold value, it can be judged that the brake pedal is depressed.

  If the accelerator is fully closed and the brake pedal is depressed, it is determined that the idle stop start condition (automatic stop condition) is satisfied, and the process proceeds to step S505 (automatic stop means).

  On the other hand, when the accelerator is open and / or the brake pedal is not depressed, it is determined that the idle stop start condition is not satisfied, and the routine is terminated without automatically stopping the internal combustion engine 101.

  The idle stop start condition (automatic stop condition) is not limited to the above condition. For example, when at least one of the accelerator fully closed state and the brake pedal depression state is satisfied, the idle stop start condition is satisfied. That the engine speed NE is lower than the threshold, and that the transmission combined with the internal combustion engine 101 is in the neutral state, etc. Can do.

  When the idle stop start condition is satisfied and the process proceeds to step S505, the fuel injection by the fuel injection valve 106 and the ignition by the spark plug 109 are stopped, and the internal combustion engine 101 is automatically stopped. Even after the fuel injection by the fuel injection valve 108 is stopped, the internal combustion engine 101 gradually stops by gradually reducing the rotational speed by the inertial force.

  When the fuel injection is stopped in step S505 and the state is shifted to the idle stop state (automatic stop state of the internal combustion engine 101), a condition (idle stop end condition) for automatically restarting the internal combustion engine 101 is set in step S506 and subsequent steps. When it is determined whether or not a restart condition (idle stop end condition, start condition) is satisfied, the internal combustion engine 101 is automatically restarted.

  In step S506, it is determined whether or not the accelerator has changed from a fully closed state to an open state. If the accelerator pedal is depressed and the driver indicates the intention to start the vehicle, the process proceeds to step S508 (automatic start means). Then, a process for restarting the internal combustion engine 101 (cranking by the starter motor and resumption of fuel injection / ignition) is performed.

  If the accelerator is fully closed, the process proceeds to step S507, where it is determined whether or not the brake pedal has been depressed, that is, whether or not the driver has released his / her foot from the brake pedal. Judgment from signals.

  If the brake pedal has not been depressed, the process proceeds to step S508 to perform processing for restarting the internal combustion engine 101 (cranking by the starter motor and resumption of fuel injection / ignition).

  As an idle stop end condition, it can be determined that the range of the automatic transmission combined with the internal combustion engine 101 has been switched from the neutral to the travel range (D range or R range). It is not limited to the above conditions.

  Along with the idle stop control as described above, the engine control device 201 having a function as a stop time fuel pressure control means uses the pressure of fuel supplied to the fuel injection valve 106 (injection pressure by the fuel injection valve 106). A certain fuel pressure PF is controlled as shown in the flowchart of FIG.

  In step S521, it is determined whether or not it is within a stop transition period from when the fuel injection by the fuel injection valve 106 is stopped until the rotation of the internal combustion engine 101 stops after the idle stop start condition is satisfied.

  The engine stoppage can be determined based on the signal from the crank angle sensor 203 being interrupted for a predetermined time or more, and the engine speed NE calculated based on the signal from the crank angle sensor 203 is a threshold value NESL. The stop of the internal combustion engine 101 can be determined at a time point when it becomes lower than (NESL> 0).

  If it is within the stop transition period, that is, if the internal combustion engine 101 is rotating with inertia after stopping fuel injection, the routine proceeds to step S522, where the target fuel pressure PFtg is set according to the engine speed NE at that time. Set.

  The target fuel pressure PFtg is a target value in the control of the fuel pump 143, and the operation amount of the fuel pump 143 is feedback-controlled based on the target fuel pressure PFtg and the actual fuel pressure even after the idle stop start condition is satisfied. It is configured to be.

  In step S522, the target fuel pressure PFtg corresponding to the engine speed NE at that time is set based on a conversion table in which the target fuel pressure PFtg is stored in advance for each engine speed NE.

  The range of the engine rotational speed NE in the conversion table is set from the stop state to the vicinity of the idle rotational speed, the larger target fuel pressure PFtg is set as the engine rotational speed NE decreases from the idle rotational speed, and the idle rotational speed is set. The target fuel pressure PFtg corresponding to the engine rotational speed NE near the speed is equal to or slightly higher than the target fuel pressure PFtg set according to the engine rotational speed NE and the engine load as will be described later during engine operation. Is set.

Therefore, the target fuel pressure PFtg set in step S522 gradually changes as the engine speed NE decreases from a value immediately before the idle stop start condition is satisfied.
On the other hand, if it is determined in step S521 that it is not the stop transition period, the process proceeds to step S523, and it is determined whether or not the engine is in an idle stop state (automatic stop state) in which the rotation of the internal combustion engine 101 is stopped after the stop transition period. To do.

  If it is determined in step S523 that the engine is in the idle stop state, the process proceeds to step S524 (stop fuel pressure control means), and the target fuel pressure PFIStg for the idle stop state is set to the target fuel pressure PFtg.

  The target fuel pressure PFIStg is set to a value equal to or slightly higher than the target fuel pressure PFtg stored in correspondence with the engine stop state in the conversion table referred to in step S522.

  That is, as shown in FIG. 6, when the idling stop start condition is satisfied and the fuel injection is stopped, the target fuel pressure PFtg is changed from the value immediately before the fuel injection is stopped (immediately before the idling stop start condition is satisfied) to the engine rotational speed NE. As the pressure decreases, the pressure is gradually increased, and is maintained near the target fuel pressure PFtg reached by the increased setting during idle stop.

  The target fuel pressure PFIStg during the idling stop may be a predetermined value stored in advance, but is changed according to the temperature of the intake valve 105 (particularly the umbrella) of the cylinder that performs fuel injection first at the time of restart. It is preferable.

  When the temperature of the intake valve 105 is high, the temperature of the intake port (intake passage wall surface) and the like around the intake valve 105 is also high. Therefore, the vaporization characteristics of the fuel spray are good, and the influence of the amount of fuel adhering to the intake port is Relatively little vaporization characteristics can be obtained.

  On the other hand, if the temperature of the intake valve 105 is low, the temperature of the intake port around the intake valve 105 is also low, and if the amount of fuel adhering to the intake port increases, the fuel spray will not evaporate, so the target fuel pressure PFIStg is further increased. It is desired to reduce the amount of fuel adhering to the intake port by setting it high.

Therefore, it is preferable to set the target fuel pressure PFIStg to a higher value as the temperature of the intake valve 105 (or intake port) is lower.
The temperature of the intake valve 105 (or intake port) can be detected based on, for example, a hollow valve stem of the intake valve 105, a temperature sensor disposed in the valve stem, and the output of the temperature sensor. It can be estimated based on the elapsed time after the idle stop start condition is satisfied (after the fuel injection is stopped), the coolant temperature of the internal combustion engine 101, and the like.

In addition, in the structure which provides the said temperature sensor, since a valve structure becomes complicated and causes a cost increase, it is preferable to estimate temperature without providing a temperature sensor.
Further, in estimating the temperature of the intake valve 105 according to the elapsed time, depending on whether the intake valve 105 of the cylinder for which fuel injection is performed first is held in an open state or a closed state in an idle stop state. It is preferable to change the correlation between the elapsed time and the estimated temperature value.

  That is, when the intake valve 105 is held open in the idle stop state, the umbrella portion of the intake valve 105 is not in contact with the cylinder wall surface, so there is no heat dissipation through the cylinder wall surface, and the intake valve over time. The temperature drop at 105 is relatively gradual.

  On the other hand, when the intake valve 105 is kept closed in the idle stop state, the umbrella portion of the intake valve 105 is in contact with the cylinder head, so that the heat of the umbrella portion of the intake valve 105 is cooled by the cooling water. The temperature drop of the intake valve 105 with respect to the passage of time is greater than when the valve is kept open.

  Therefore, when the intake valve 105 of the cylinder for which fuel injection is performed first at the time of restart is in the open state, the idle stop start condition is compared to the case where the intake valve 105 is held in the closed state (the state immediately before the valve is opened). Is set so that the temperature reduction characteristic with respect to the elapsed time after the establishment of (after stopping fuel injection) becomes gentle, and conversely, when the valve is kept closed in the idle stop state, the valve is kept open. Compared to the case, the temperature drop characteristic is set to be larger with respect to the elapsed time after the idle stop start condition is satisfied (after the fuel injection is stopped).

  As described above, if the characteristic of the temperature estimation value with respect to the elapsed time after the idle stop start condition is satisfied (after the fuel injection is stopped) is changed according to the open / close state of the intake valve 105 in the cylinder to which fuel is initially injected upon restart. The temperature of the intake valve 105 can be estimated with high accuracy based on the elapsed time.

  The flowchart of FIG. 7 shows the details of the processing in step S524 (stopping fuel pressure control means), and shows the intake valve 105 in accordance with the elapsed time after the idle stop start condition is satisfied (after fuel injection is stopped). A process of estimating the temperature and setting the target fuel pressure PFIStg based on the estimated value is shown.

  In the flowchart of FIG. 7, first, in step S601, it is determined whether or not the intake valve 105 of the cylinder that is initially injected with fuel during the restart is held open during the idling stop.

  If the engine is held in the open state during the idling stop, the process proceeds to step S602, where the correlation between the elapsed time after the idling stop start condition is satisfied (after the fuel injection is stopped) and the temperature of the intake valve 105 is stored in advance. By referring to the state conversion table, the temperature corresponding to the elapsed time at that time is searched.

  The conversion table referred to in step S602 is adapted to the case where the intake valve 105 is held in the open state, and the temperature decrease with respect to the increase in elapsed time is more gradual than the closed state conversion table referred to in step S603 described later. Is set.

  On the other hand, if it is determined in step S601 that the intake valve 105 is maintained in the closed state during the idle stop, the process proceeds to step S603, and the elapsed time and intake air after the idle stop start condition is satisfied (after the fuel injection is stopped). The closed state conversion table in which the correlation with the temperature of the valve 105 is stored in advance is referred to, and the temperature corresponding to the elapsed time at that time is searched.

  The conversion table referred to in step S603 is adapted to the case where the intake valve 105 is held in the closed state, and the temperature decrease with respect to the increase in elapsed time is set larger than the open state conversion table referred to in step S602. ing.

  In step S602 or step S603, when the temperature of the intake valve 105 in the cylinder to be initially injected for restart is estimated based on the elapsed time (engine stop duration) and the open / closed state of the intake valve 105, the process proceeds to step S604. Based on the estimated temperature value, the target fuel pressure PFIStg in the idle stop state is set.

In step S604, the target fuel pressure PFIStg is set to a higher value as the estimated temperature value of the intake valve 105 becomes lower.
In the temperature estimation of the intake valve 105, the estimated temperature can be gradually decreased from the initial value at a decreasing speed that varies depending on the open / closed state, with the temperature at the time when the idle stop start condition is satisfied as the initial value.

The elapsed time may be not the time when the idle stop start condition is satisfied, but the time after the rotation of the internal combustion engine 101 is stopped.
Further, as described above, the temperature sensor is provided, and the target fuel pressure PFIStg can be set to a higher value as the temperature of the intake valve 105 detected by the temperature sensor becomes lower.

  Further, the longer the idle stop state continues, the lower the temperature of the intake valve 105. Therefore, the target fuel pressure PFIStg is changed to a higher value as the duration time of the idle stop state becomes longer. be able to.

  In this embodiment, as will be described later, the first fuel injection at the time of restart is performed for the cylinder in the middle of the intake stroke in which the intake valve 105 is held open during idle stop. Is the later stage of the intake stroke (immediately before the closing timing IVC of the intake valve 105 or just before the bottom dead center of the piston), and sufficient fuel cannot be introduced even if fuel is injected into the cylinder. The cylinder that is in the intake stroke, that is, the cylinder in which the intake valve 105 is kept closed during idle stop can be set as the initial injection cylinder, and fuel injection can be performed before the opening timing IVO of the intake valve 105.

  As described above, when selecting the cylinder to be subjected to the initial injection, the intake valve 105 of the initial injection cylinder is held in the open state and in the closed state during the idle stop. If the temperature of the intake valve 105 is estimated according to the above open / closed state, the temperature of the intake valve 105 of the cylinder that performs the initial injection is estimated with high accuracy, and an appropriate fuel pressure corresponding to the actual temperature is obtained. Can be controlled.

  Further, the cylinder in which the piston is stopped between the intake top dead center and the bottom dead center during idle stop is determined as the cylinder in the intake stroke, and the first fuel injection at the time of restart is performed on the cylinder. It can be set as the structure to perform.

  In this case, the piston is stopped between the intake top dead center and the open timing IVO of the intake valve 105 after the top dead center, and the intake valve 105 is closed, and the position where the piston is advanced from the open timing IVO. If the temperature of the intake valve 105 is estimated by changing the temperature decrease rate over time when the intake valve 105 is stopped and the intake valve 105 is open, the temperature of the intake valve 105 of the cylinder that performs the initial injection is determined. Can be estimated with high accuracy and controlled to an appropriate fuel pressure corresponding to the actual temperature.

  If it is determined in step S523 in the flowchart of FIG. 5 that the engine is not in the idling stop state, the process proceeds to step S525, and the first fuel injection in the restart from the idling stop state (the fuel to the cylinder that was stopped in the intake stroke) It is determined whether or not (injection) has been completed.

  If the initial fuel injection is not completed, the target fuel pressure PFIStg is maintained by proceeding to step S524. Such a function corresponds to the fuel pressure holding means.

  On the other hand, if it is determined that the first fuel injection has been completed, the routine proceeds to step S526, where it is determined whether or not the internal combustion engine 101 is in the start completed state (operating state). Judge based on whether it is high or not.

  If the engine has not been completed after the first fuel injection is completed, the process proceeds to step S527 (automatic fuel pressure control means at the time of automatic start), and the target fuel pressure PFSTtg stored in advance for the start is used as the target fuel pressure PFtg. Set to.

  As shown in FIG. 6, the starting target fuel pressure PFSTtg is lower than the target fuel pressure PFIStg for the idle stop state, and is a target set according to the engine speed NE and the engine load after the start is completed. The pressure is set higher than the fuel pressure PFORtg.

  On the other hand, if it is determined in step S526 that the internal combustion engine 101 has been started and the internal combustion engine 101 is in an operation continuation state, the process proceeds to step S528, in accordance with the engine rotational speed NE and the engine load at that time. The target fuel pressure PFORtg is set to the target fuel pressure PFtg.

The engine load is determined based on the intake air amount, basic fuel injection amount, intake pipe negative pressure, and the like.
Next, the injection control when the internal combustion engine 101 is restarted from the idle stop state will be described with reference to the flowcharts of FIGS.

  The routine shown in the flowchart of FIG. 8 is a cylinder that is stopped during the intake stroke (the intake valve 105 is open) when the internal combustion engine 101 is automatically stopped by idle stop control in preparation for the first injection at the time of restart. The process which detects and memorize | stores is shown.

  In step S541, it is determined whether or not an idle stop start condition is satisfied. When the idle stop start condition is satisfied and fuel injection is stopped, the process proceeds to step S542.

  In step S542, cylinder discrimination (stroke determination for each cylinder) based on the cam signal CAM from the cam sensor 204 is continued during the stop transition period, and each time a new cylinder discrimination is made, the stored value is stored. Instead, a new cylinder discrimination result is stored, and the cylinder discrimination result is updated and stored.

  In step S543, it is determined whether or not the rotation of the internal combustion engine 101 has stopped. Until the rotation stops, the cylinder determination in step S542 and the update and storage of the determination result are repeated, and the point in time when the rotation of the internal combustion engine 101 stops. When this routine is ended, the last cylinder discrimination result, that is, the cylinder (the cylinder in the middle of the intake stroke) in which the intake valve 105 is held in the open state when the engine rotation is stopped is stored and held.

  Instead of determining that the cylinder stopped when the intake valve 105 is in the open state is a cylinder stopped during the intake stroke, the piston is stopped between the intake top dead center and the bottom dead center as described above. Can be determined as a cylinder in the middle of the intake stroke.

The flowchart of FIG. 9 shows a routine for controlling fuel injection at the time of restart from the idle stop state.
First, in step S561, it is determined whether or not a restart request (idle stop end determination) has occurred due to depression of the accelerator pedal or release of the brake pedal from the idle stop state.

  When a restart request is generated from the idle stop state, the process proceeds to step S562, and the determination result of the intake stroke cylinder at the time of engine rotation stop (cylinder determination result) stored and held based on the routine shown in the flowchart of FIG. Is read.

  In the next step S563 (fuel injection control means, fuel injection start means), from the cylinder discrimination result read out in step S562, a cylinder that is stopped during the intake stroke (with the intake valve 105 opened) is identified, An injection pulse signal is output to the fuel injection valve 106 of the cylinder to start fuel injection.

  In this way, if fuel injection is performed in a cylinder that has been stopped in the middle of the intake stroke immediately before the start of cracking, the fuel is sucked into the cylinder immediately after the cranking starts, and ignition is performed through the compression stroke for the first explosion. Thus, the time until the first explosion can be shortened as much as possible, and the start performance of the vehicle can be improved.

  That is, when the internal combustion engine 101 is continuously operated, the intake valve 105 performs fuel injection before the opening timing IVO. Therefore, if the first fuel injection is restarted at the same injection timing, it stops in the middle of the intake stroke. The cylinder that is in the intake stroke next to the cylinder is the target cylinder for the first injection, but this increases the time until the first explosion.

Therefore, the first injection is performed on the cylinder that was stopped in the middle of the intake stroke (with the intake valve 105 opened) so that the first explosion can be obtained at the earliest possible timing.
In step S564, cranking by the starter motor is started. That is, immediately before the start of cranking, fuel injection is started for the cylinders that have been stopped during the intake stroke.

  When cranking is started in step S564, in step S565, the second and subsequent fuel injections (in accordance with the normal injection timing set during the period in which the intake valve 106 is closed (for example, during the exhaust stroke or during the expansion stroke) ( After the cranking is started, fuel injection is performed on the cylinder that is in the intake stroke).

  That is, for cylinders that have stopped in the middle of the intake stroke, fuel is injected while the intake valve 105 is open, but from the cylinder that is in the intake stroke next to the cylinder that has stopped in the middle of the intake stroke. The fuel injection is performed at the timing when the intake valve 106 is closed.

  In the present embodiment, the target fuel pressure is set according to the engine speed when the engine speed is in a reduced state, thereby enabling a continuous increase in the target fuel pressure with a small fuel pressure step corresponding to the decrease in the engine speed. However, the present invention is not limited to this, and a configuration may be adopted in which a decrease in restartability due to enrichment of the air-fuel ratio is suppressed, and the target fuel pressure is set in several steps within a range where acceptable startability is obtained. In this case, there may be a step between the target fuel pressures, and there is a concern that the startability will be reduced for continuous setting, but as described above, the setting is made so that the deterioration of the air-fuel ratio, the startability requirement of the product etc. do it.

Here, the setting of the target fuel pressure PFtg and the operation of the fuel injection control at the start will be described.
As described above, when the internal combustion engine 101 is restarted from the idle stop state, the fuel injection to the cylinders stopped in the middle of the intake stroke is started immediately before the start of cranking. Therefore, when the fuel pressure is low, the fuel spray spreads and the amount of fuel adhering to the wall surface of the intake port is increased, so that the startability is deteriorated.

  Here, if the fuel pressure (injection pressure) is set high, the penetration force (penetration) of the fuel spray from the fuel injection valve 106 increases, and even if the intake air is injected with almost no flow, the fuel adheres to the wall surface. Can be suppressed.

  Therefore, if the first fuel injection when the internal combustion engine 101 is restarted from the idle stop state is performed at a fuel pressure that can ensure a sufficient penetrating force even in a state where almost no intake air flows, the amount of fuel adhering to the wall surface can be reduced. It is possible to reduce the amount of air-fuel mixture that is sufficient for combustion, and to improve the combustibility and the startability.

Therefore, during idling stop, the target fuel pressure PFIStg higher than that during operation of the internal combustion engine 101 is maintained, and the first fuel injection is performed at the target fuel pressure PFIStg during restart.
In other words, the target fuel pressure PFIStg is set to a fuel pressure that can ensure sufficient penetrating force by the first fuel injection, and in order to perform the first fuel injection at the target fuel pressure PFIStg, an idle stop start condition is satisfied. The fuel pressure is increased up to the target fuel pressure PFIStg from the time point (the time point when fuel injection is stopped), and is maintained near the target fuel pressure PFIStg.

  By the way, there is a case where a restart request is generated due to an accelerator operation or the like from the time when the idle stop start condition is satisfied until the rotation of the internal combustion engine 101 actually stops (stop transition period). At this time, if the fuel pressure increases to the vicinity of the target fuel pressure PFIStg, the fuel injection is resumed at the fuel pressure near the target fuel pressure PFIStg.

  However, the target fuel pressure PFIStg is a pressure suitable for injecting fuel in a state where almost no intake air flows, and is a state where intake air is flowing while the engine is rotating (intake pipe negative pressure generation state). The pressure is too high for fuel injection.

  For this reason, if a restart request is generated during the stop transition period (while the engine 101 is rotating with inertia) and the fuel pressure at that time is increased to the vicinity of the target fuel pressure PFIStg, the fuel pressure is excessively high. The fuel injection amount at unit time increases the fuel injection amount per unit time, injects more fuel than the fuel amount required by the internal combustion engine 101, and the air-fuel ratio becomes overrich, resulting in unstable combustion. Restartability may be reduced.

  Therefore, in this embodiment, during the stop transition period, the target fuel pressure PFtg is gradually increased according to the decrease in the engine speed NE, so that even if a restart request occurs during the stop transition period, a high The startability can be maintained.

  That is, by gradually increasing the target fuel pressure PFtg in accordance with the decrease in the engine speed NE, it is possible to avoid boosting to the vicinity of the target fuel pressure PFIStg in a state where the engine rotates at the inertia. The optimum fuel pressure can be controlled in accordance with the engine speed NE.

  The lower the engine speed NE, the more energy required for starting, and the weaker the flow of intake air into the cylinder, so the lower the engine speed NE during the stop transition period, the higher the target fuel pressure PFtg. Then, the vaporized fuel is increased by atomizing the fuel spray at a high fuel pressure, and more vaporized fuel is introduced into the cylinder to generate a large engine torque for starting.

  On the other hand, the target fuel pressure PFtg is set to be relatively low in a state where the engine speed NE immediately after the start of the idling stop start condition has not decreased so much, even if a restart request occurs in this state, an excessive amount It is possible to suppress over-rich caused by the injection of this fuel.

  Therefore, if the target fuel pressure PFtg is gradually increased in accordance with the decrease in the engine speed NE during the stop transition period, a restart request is generated at a timing when the engine speed NE during the stop transition period is different. Also, good startability can be ensured.

  With the above fuel pressure control, as shown in FIG. 6, during the stop transition period from the idling stop start determination (time t1) to the time t2 when the rotation of the internal combustion engine 101 stops, the target is set according to the decrease in the engine speed NE. The fuel pressure PFtg is gradually increased to maintain the target fuel pressure PFIStg during the idle stop from the time when the rotation of the internal combustion engine 101 stops (time t2) until the idle stop end determination (time t3). Is maintained at the target fuel pressure PFIStg from time (time t3) until time t4 when the first fuel injection to the cylinders stopped in the middle of the intake stroke is completed, and when the first fuel injection is completed (time t4). , The fuel pressure is reduced to the target fuel pressure PFSTtg suitable for starting, and further, at the time of starting completion (time t5), the load / rotation Etc. to change the target fuel pressure PFORtg to be set from.

  In other words, the first fuel injection is performed with almost no intake air flowing, so a high fuel pressure is set and the amount of fuel adhering to the intake port is reduced to improve the combustibility. Fuel adhesion cannot be completely prevented.

  On the other hand, as the engine speed NE increases with the start of cranking, the flow rate of the intake air increases and the attached fuel is vaporized. Therefore, if the fuel pressure remains high after the first injection, the attached fuel ( By introducing the fuel vaporized from the wall flow into the cylinder, the air-fuel mixture becomes overrich, the combustibility after the first explosion deteriorates, the increase in the engine speed NE slows down, and the engine speed There is a possibility that the startability is deteriorated, for example, the NE fluctuates.

  Therefore, in the above embodiment, by reducing the target fuel pressure PFtg after the end of the initial injection, the amount of fuel injected from the fuel injection valve 106 per unit time is reduced, and the engine rotational speed NE increases as cranking starts. Therefore, even if vaporization from the attached fuel proceeds, the mixture is prevented from being over-rich and the combustibility after the first explosion can be maintained well.

  In the second and subsequent injections after the first injection, the injection timing is set during the exhaust stroke, and the time from the injection timing until combustion (ignition) is longer than that during the first injection, and the fuel vaporization time is increased. Therefore, even if the second and subsequent fuel injections are executed in a state where the fuel pressure is lowered, the wall flow rate is hardly affected.

  In the present embodiment, the second and subsequent injections (fuel injection into the cylinder that will be in the intake stroke after the second) are performed in the closed state of the intake valve 105 during the exhaust stroke and the expansion stroke. However, it may be performed while the intake valve 105 is open.

  Further, in a cylinder that is stopped in the intake stroke during idle stop (a cylinder in which the intake valve 105 is kept open), the piston position is close to bottom dead center or close to the closing timing IVC of the intake valve 105, If it is determined that a sufficient amount of fuel spray cannot be introduced into the cylinder with the remaining intake stroke even after fuel injection is performed, the cylinder that will be the next intake stroke is set as the initial injection cylinder, and the fuel injection is performed. Can be done.

Further, the cylinder in the middle of the intake stroke may be a cylinder in which the piston is stopped between the intake top dead center and the bottom dead center, and the fuel injection at the first restart can be performed on the cylinder.
As described above, according to the above-described embodiment, after the idling stop start condition is satisfied, while the internal combustion engine 101 is rotating with inertia, the target fuel pressure PFtg corresponding to the engine speed NE at that time is set, Since the actual fuel pressure is changed following the target fuel pressure PFtg, when the automatic start request, that is, the driver's intention to start the vehicle is detected before the internal combustion engine 101 is completely stopped, the engine speed NE at that time is detected. The fuel injection can be performed at a fuel pressure suitable for restarting at the engine, so even if a restart request occurs before the engine rotation stops completely, the fuel injection amount is excessive and the air-fuel ratio is overrich. Thus, deterioration of combustibility can be suppressed and restartability can be improved.

  In the above embodiment, the target fuel pressure PFIStg during idling stop, in other words, the fuel pressure of the initial injection at the time of restart is set according to the temperature of the intake valve 105 of the cylinder that performs the initial injection. During the injection, an optimal fuel spray that can be vaporized by collision of the fuel spray with the intake valve 105 can be formed, improving the vaporization performance in the first fuel injection and improving the combustibility in the first explosion be able to.

  In the above embodiment, the temperature drop characteristic of the intake valve 105 with respect to the elapsed stop time of the internal combustion engine 101 is set to a different characteristic depending on the open / closed state of the intake valve 105. Thus, the actual temperature can be estimated with high accuracy.

  Furthermore, in the above embodiment, when the idle stop termination condition is satisfied and the automatic start is started, the first fuel injection is performed on the cylinder that is stopped in the middle of the intake stroke. Also in the internal combustion engine 101 provided with the fuel injection valve 106 for each cylinder, the time until the first explosion of the first injection cylinder can be shortened, the engine start time can be shortened, and further, the start performance of the vehicle can be improved. Can do.

  Further, in the above embodiment, since the fuel injection is performed at a fuel pressure lower than the first time at the second and subsequent fuel injections at the time of restart, the initial fuel injection is performed with the intake air flow velocity almost close to zero. When the adhering fuel is vaporized and introduced into the cylinder together with the second and subsequent injection fuels, the air-fuel ratio can be prevented from becoming over-rich, and the deterioration of combustibility due to over-rich can be suppressed. The start can be completed.

  By the way, in the above embodiment (first embodiment), the target fuel pressure PFtg is set with different characteristics by dividing the period from the end of the initial injection to the completion of the start (during start) and the period after the start is completed. However, as in the second embodiment shown in the flowchart of FIG. 10 and the time chart of FIG. 11, if it is determined in step S525 that the initial fuel injection has been completed, whether or not the start has been completed. The target fuel pressure PFtg can be set according to the temperature of the intake valve 105 at that time.

The function of setting the target fuel pressure PFtg according to the temperature of the intake valve 105 corresponds to the post-startup fuel pressure control means.
In the flowchart of FIG. 10, when it is determined in step S525 that the first fuel injection has been completed, the process proceeds to step S611, the operation continuation time after restart (after cranking starts), the operation state of the internal combustion engine 101 ( The temperature of the intake valve 105 (umbrella) is estimated based on the engine load, the engine speed NE, and the like.

  Here, a higher temperature is estimated as the temperature of the intake valve 105 (umbrella part) as the operation continuation time becomes longer, and the rate of increase of the estimated temperature with respect to the operation continuation time is set faster as the load is higher and the rotation is higher.

  Next, in step S612, the fuel pressure in the second and subsequent fuel injections at the time of restart is set according to the temperature of the intake valve 105 estimated in step S611. Specifically, the temperature of the intake valve 105 is The lower the value, the higher the target fuel pressure PFtg is set.

  In such a configuration, when the temperature of the intake valve 105 immediately after the restart is low, the target fuel pressure PFtg is set high, so that the penetration force (penetration) of the fuel spray is high, so that it can be prevented from adhering to the intake port.

Accordingly, the fuel spray is easily introduced into the cylinder together with the intake air, and the air-fuel mixture can be formed sufficiently for combustion while suppressing the amount of wall surface adhesion, and the combustibility can be improved.
Further, since the target fuel pressure PFtg is lowered as the temperature of the intake valve 105 rises as the number of combustion increases (engine speed NE increases), the fuel spray penetration force (penetration) weakens and adheres to the intake port wall surface. By increasing the amount, it is possible to widen the adhesion area of the fuel, thin the wall flow, promote vaporization of the adhered fuel using the heat of the intake port, and improve the vaporization performance.

  Further, by gradually decreasing the fuel pressure with respect to the temperature rise of the intake valve 105, the fuel injection amount per unit time in the fuel injection valve 106 is reduced, and the fuel adhering to the wall surface is vaporized by the fuel injection at the initial stage of restart. Thus, it is possible to suppress over-riching of the air-fuel ratio due to being introduced into the cylinder, and it is possible to suppress deterioration in startability.

The time chart of FIG. 11 shows the fuel pressure change when the target fuel pressure PFtg after the completion of the first injection is set according to the flowchart of FIG.
As shown in FIG. 11, the target fuel pressure PFtg is set from the idle stop start determination (time t1) to the initial injection completion time (time 4), as in the first embodiment, but after the initial injection is completed (time 4 and later), the target fuel pressure PFtg is gradually reduced as the temperature of the intake valve 105 increases with time.

  In the first and second embodiments, since the first fuel injection is started for the cylinders that are stopped in the intake stroke in the idle stop state, the fuel injected for the first time is easily introduced into the cylinder. In this case, the combustibility (combustion torque) of the first explosion is improved. The ease of introducing the fuel spray into the cylinder is improved by increasing the opening area (valve lift amount) of the intake valve 105 in the idle stop state as much as possible.

  A third embodiment for executing valve timing control for increasing the opening area (valve lift amount) of the intake valve 105 in the cylinder to be injected for the first time will be described below with reference to the flowchart of FIG.

The engine control device 201 has a function as valve lift amount control means as shown in the flowchart of FIG.
In the flowchart of FIG. 12, first, in step S621, it is determined whether an idle stop start condition is satisfied and fuel injection is stopped.

  Then, in the operating state of the internal combustion engine 101 before the idle stop start condition is satisfied, the target valve timing is set according to, for example, the engine load and the engine rotational speed NE by bypassing steps S622 to 625 and proceeding to step S626. Set and control the variable valve timing mechanism 114.

  When the idle stop start condition is established from the control state of the variable valve timing mechanism 114, the process proceeds to step S622, and the valve timing is set so that the central phase of the valve operating angle of the intake valve 105 approaches 90 deg (ATDC 90 deg) after top dead center. The advance angle control is performed.

  In the idle state of the internal combustion engine 101 immediately before the idle stop start condition is satisfied, the central phase of the valve operating angle of the intake valve 105 is set to be slower than 90 deg after top dead center. Therefore, in step S622, the valve timing Is advanced to change the center phase closer to 90 deg after top dead center.

  In step S623, it is determined whether or not the actual center phase is near 90 deg after top dead center by the control in step S622, and the advance in step S622 is performed until the actual center phase is near 90 deg after top dead center. Continue control.

  When the actual center phase is around 90 deg after top dead center, the process proceeds to step S624, the lock mechanism of the variable valve timing mechanism 114 is operated, and the valve timing at that time is locked.

In other words, the lock mechanism of the variable valve timing mechanism 114 is set so as to lock the valve timing in an intermediate phase state in which the center phase is around 90 deg after top dead center.
In step S625, it is determined whether or not the first fuel injection at the time of restart from the idling stop state is completed, and the center phase is moved to a position near 90 deg after the top dead center until the first fuel injection is completed. Keep the locked state of.

  When the first fuel injection is completed, the process proceeds to step S626, the locked state is released, the target valve timing is set according to the engine load and the engine speed NE, and the variable valve timing mechanism 114 is shifted to a control state. , Change the valve timing by retarded angle.

  That is, when the first fuel injection is completed, the valve timing is delayed until the start of the next fuel injection, thereby suppressing the vaporization of the fuel adhering to the intake port and improving the startability and the subsequent sustainability. .

When the internal combustion engine 101 is automatically stopped, a cylinder that stops in the middle of the intake stroke has a high probability that the piston position will be around 90 deg after top dead center.
Since the central phase of the valve operating angle of the intake valve 105 is the timing at which the valve lift amount of the intake valve 105 becomes the largest, if the valve timing is controlled so that the central phase is around 90 deg after top dead center, The intake valve 105 of the cylinder stopped in the intake stroke is in the state of the largest opening area (valve lift amount).

  If the valve timing is controlled so that the center phase is around 90 deg after top dead center while the internal combustion engine 101 is rotating with inertia, the friction in changing the valve timing is small and the driving load of the actuator can be reduced. it can.

  If a mechanism that locks the center phase around 90 deg after top dead center is provided, the center phase around 90 deg after top dead center can be reliably maintained during idle stop. For example, in the hydraulic variable valve timing mechanism, the supply of hydraulic pressure If the center phase can be maintained during idle stop by stopping the drain, the variable valve timing mechanism may not include the lock mechanism.

  Further, when a variable valve timing mechanism using an electrically responsive actuator is used as the actuator, the center phase is changed toward about 90 deg after top dead center from the time when it is determined that the idle stop end condition is satisfied. It is possible to advance the valve timing.

  In this case, even if the opening area (valve lift amount) of the intake valve 105 is not the maximum at the start of the first injection, the valve timing is advanced to change the opening area (valve lift amount) while fuel injection continues. Will change.

  As described above, if the valve timing is advanced so that the opening area of the intake valve 105 of the cylinder that stops in the middle of the intake stroke is increased, the fuel injected at the first time can be easily introduced into the cylinder, The flammability of the first explosion is improved, and the time to complete the start-up can be shortened.

  The target in the valve timing control is not limited to the piston position of the cylinder that stops in the middle of the intake stroke, but the target can be set near the piston position (for example, 70 deg to 120 deg after top dead center). The valve timing may be controlled in the angular direction.

  FIG. 13 is a diagram for explaining the effect of the advance timing control of the valve timing. For example, when the valve timing when the advance angle control is not performed is the setting indicated by the dotted line in FIG. In the cylinder stopped at ATDC 90 deg in the middle of the intake stroke, the valve lift amount VL1 is kept open in the idle stop state.

  On the other hand, if the advance is made so that ATDC 90 deg becomes the center phase, the cylinder stopped at ATDC 90 deg in the middle of the intake stroke will keep the valve lift amount VL2 open in the idle stop state, and this largest valve If the fuel is injected toward the intake valve 105 that is opened with the lift amount VL2, the fuel is easily introduced into the cylinder, and the combustibility of the first explosion is improved.

  It suffices if the valve lift amount can be made larger than the valve lift amount VL1 at ATDC 90 deg in the setting shown by the dotted line in FIG. 13, and the valve lift amount can be increased even if the central phase is advanced from ATDC 90 deg.

  FIG. 14 is a time chart showing the change in the opening timing IVO of the intake valve 105 when the valve timing control is performed, and the valve timing advance control is performed from the time when the idling stop start determination is made (time t1). In the stop transition period (time t1 to time t2), the opening timing IVO gradually advances.

If the target valve timing is not reached within the stop transition period, the open state during idle stop is determined at the valve timing immediately before the rotation stop.
When the rotation of the internal combustion engine 101 stops, the opening and closing of the intake valve 105 is stopped, and the intake valve 105 of the cylinder stopped in the middle of the intake stroke is held in a large valve lift amount by the advance angle control. .

  Then, the idling stop end determination is made at time t3, and further, the valve timing advanced during the stop transition period is held until the time t4 when the first fuel injection in the cylinder in which the intake valve 105 is open is held. When the fuel injection is completed, the valve timing is retarded to return to the valve timing corresponding to the load and rotation speed at that time.

  In the third embodiment, the variable valve timing mechanism 114 performs the advance control of the valve timing that brings the center phase of the intake valve 105 close to 90 deg after top dead center, whereby the first fuel injection is performed in the cylinder. In the internal combustion engine 101 having the variable valve lift mechanism 113, while the internal combustion engine 101 after the idle stop start condition is established is rotating with inertia, the valve lift amount ( By performing the control to increase the maximum valve lift amount), the opening area of the intake valve 105 of the cylinder stopped during the intake stroke can be increased.

  That is, even if the valve timing is not changed, if the variable valve lift mechanism 113 is controlled in the direction in which the valve lift amount increases, the opening area of the intake valve 105 of the cylinder stopped in the middle of the intake stroke becomes large. The fuel injected into the cylinder can be easily introduced into the cylinder, the combustibility of the first explosion is improved, and the time until the start is completed can be shortened.

  That is, as shown in FIG. 15, in the stop transition period from time t1 to time t2, the variable valve lift mechanism 113 is controlled in a direction in which the valve lift amount increases, and in the idle stop state from time t2 to time t3, When the initial fuel injection is completed at time t4, the valve lift amount is reduced until the next fuel injection is started, the vaporization of the fuel adhering to the intake port is suppressed, the startability and thereafter Improve the sustainability of.

The target in the valve lift amount control is not limited to the maximum value in the variable range of the valve lift amount, but may be any target that increases and changes the valve lift amount.
Here, when the variable valve timing mechanism 114 and the variable valve lift mechanism 113 are provided as in the present embodiment, both the valve timing advance control and the valve lift amount increase control are executed. The opening area of the intake valve 105 can be increased, and the fuel injected for the first time can be easily introduced into the cylinder.

  By the way, the fuel injection at the time of restart for the cylinder stopped in the middle of the intake stroke may be configured to supply the necessary amount by one injection, or the necessary amount is intermittently injected in a plurality of times. It may be.

  If the required amount is divided into multiple injections and the injection with a short pulse width is repeated, the speed of fuel spray decreases, so the amount of fuel floating in the intake port of the injected fuel increases, and the intake air The amount of fuel adhering to the wall surface of the port can be reduced.

  Furthermore, during the idle stop, the actual fuel pressure is controlled to the target fuel pressure PFIStg, and the first fuel injection is performed at a high pressure state of the target fuel pressure PFIStg. Fine fuel spray floats in the intake port by the injection, and by combining the fuel pressure control by the target fuel pressure PFIStg and the injection divided into multiple times, the fuel adhesion to the wall surface is further reduced, and the fuel The vaporization of spray can be further promoted.

  It should be noted that the number of divided injections when performing the injection divided into a plurality of times is such that the greater the number of times (the shorter the injection time per time), the lower the spray speed and the less the fuel adhering. By increasing the total time of the interval from one injection to the next, the time until the completion of the injection becomes longer, and when the injection time per injection becomes shorter, the fuel measurement accuracy decreases.

  Therefore, the first fuel injection amount can be injected within the period until the intake valve 105 is closed, and the minimum injection amount in the linearity region in which the injection amount changes in proportion to the injection pulse width. It is preferable to set the number of divisions so that one injection can be performed with an injection pulse width equal to or greater than (minimum injection amount with no variation in injection amount characteristics with respect to the injection pulse width).

  By setting the number of divided injections in this way, it is possible to maintain the injection accuracy while setting the number of divided injections as much as possible, so that the required amount of fuel can be injected while suppressing the adhesion of fuel to the wall surface.

  Note that, when the temperature of the intake valve 105 or the intake port wall surface is low, the vaporization performance decreases, so it is preferable to increase the number of divided injections. For example, the temperature of the intake valve 105, the coolant temperature of the engine 101, etc. Therefore, the lower the temperature, the greater the number of divided injections.

  Further, in the first fuel injection, the spray shape can be switched as a means for suppressing fuel adhesion to the intake port wall surface and introducing more fuel into the cylinder.

  Specifically, the spray angle of the fuel injection valve 106 is switched, the spray angle is set to a narrow angle at the first injection in the restart from the idle stop state, and the spray angle is set to a wide angle at the second and subsequent injections. As a result, the startability is improved and the operation sustainability thereafter is ensured.

  As a fuel injection valve in which the spray angle can be switched, for example, as disclosed in Japanese Patent Laid-Open No. 2000-097128, a fuel injection valve whose spray angle changes depending on the fuel pressure, or disclosed in Japanese Patent Laid-Open No. 2006-022713. As described above, it is possible to use a fuel injection valve that can change the spray angle by opening / closing control of the electromagnetic valve (control of the actuator).

  In the above embodiment, the fuel injection valve 106 in the internal combustion engine 101 is provided on the upstream side of the intake valve 105. However, in the in-cylinder direct injection internal combustion engine in which the fuel injection valve 106 directly injects fuel into the cylinder, When changing to a target fuel pressure during idle stop different from that during operation of the internal combustion engine 101 based on the establishment of the idle stop start condition, the fuel pressure is controlled according to the engine rotational speed NE at that time during the stop transition period. be able to.

Here, technical ideas other than the claims that can be grasped from the above embodiment will be described together with effects.
(A) A control device for an internal combustion engine that includes a variable valve mechanism that varies a valve timing and / or a maximum valve lift amount of an intake valve, and in which a fuel injection valve is disposed upstream of the intake valve. ,
Automatic stop means for stopping the internal combustion engine under a predetermined stop condition and restarting under a predetermined start condition;
Fuel injection starting means for performing the first fuel injection at the time of restart for the cylinder stopped during the intake stroke in the automatic stop;
Valve lift amount control means for controlling the variable valve mechanism after the predetermined stop condition is satisfied so as to increase the valve lift amount of the intake valve in a stopped state during the intake stroke;
A control apparatus for an internal combustion engine, comprising:

In the above configuration, by controlling the variable valve mechanism after the predetermined stop condition is satisfied, the valve lift amount of the intake valve in the stop state during the intake stroke is increased. The fuel is easily introduced into the cylinder, and the combustibility is improved.
(B) a control device for an internal combustion engine in which the fuel injection valve is disposed upstream of the intake valve;
Automatic stop means for stopping the internal combustion engine under a predetermined stop condition and restarting under a predetermined start condition;
Temperature detecting means for detecting or estimating the temperature of the intake valve;
A fuel pressure control means during stop that variably controls the fuel pressure during the automatic stop according to the temperature of the intake valve;
A control apparatus for an internal combustion engine, comprising:

In the above configuration, the fuel pressure during stoppage is controlled to an appropriate value corresponding to the difference in vaporization performance due to the temperature of the intake valve, and the combustibility by the first injection at the restart can be improved.
(C) Fuel pressure holding means for holding the fuel pressure during the automatic stop until completion of the first fuel injection at the time of restart under the predetermined starting condition is provided. The internal combustion engine control device described.

According to the above configuration, the first fuel injection at the time of restart can be performed at the optimum pressure, and the fuel pressure required value in the second and subsequent injections can be controlled thereafter.
(D) an internal combustion fuel pressure control means for variably controlling the fuel pressure after completion of the first fuel injection at the time of restart according to the temperature of the intake valve; Engine control device.

According to the above configuration, the fuel pressure after startup can be appropriately controlled in accordance with the difference in vaporization performance due to the temperature of the intake valve.
(E) automatic stop means for automatically stopping the internal combustion engine by stopping fuel injection from the fuel injection valve provided in the intake passage when an automatic stop request is generated while the vehicle is stopped;
In the control device for an internal combustion engine comprising automatic start means for starting automatic fuel injection from the fuel injection valve after an automatic start request is generated during the automatic stop,
Stop fuel pressure control means for controlling the fuel pressure so as to be the first predetermined fuel pressure during the automatic stop;
Fuel injection start means for starting fuel injection from the fuel injection valve in a state where the first predetermined fuel pressure is controlled before the engine rotation starts based on the automatic start request;
Fuel pressure control means at the time of automatic start for controlling the fuel pressure so that the fuel pressure becomes a second predetermined fuel pressure lower than the first predetermined fuel pressure after the start of engine rotation based on the automatic start request;
A control device for an internal combustion engine, comprising:

  According to the above configuration, the first fuel injection can be performed at a high fuel pressure suitable for a state in which the intake air flow velocity before the engine rotation starts is low, and when the intake air flow velocity after the rotation starts increases, the fuel pressure is reduced. By reducing the amount, excessive fuel injection can be suppressed, and startability and operation continuity can be improved.

  DESCRIPTION OF SYMBOLS 101 ... Internal combustion engine, 102 ... Intake pipe, 105 ... Intake valve, 106 ... Fuel injection valve, 113 ... Variable valve lift mechanism (variable valve mechanism), 114 ... Variable valve timing mechanism, 201 ... Engine control apparatus, 143 ... Fuel Pump, 144 ... Fuel pressure sensor

Claims (3)

An internal combustion engine that is stopped under a predetermined stop condition and restarted under a predetermined start condition, wherein a variable valve mechanism that varies at least one of a valve timing and a maximum valve lift amount of the intake valve, and an upstream side of the intake valve In an internal combustion engine comprising a fuel injection valve provided in a side intake pipe, and an electric fuel pump that pumps fuel to the fuel injection valve ,
Controlling the electric fuel pump so that the fuel pressure supplied to the fuel injection valve is higher during operation of the internal combustion engine than during operation of the internal combustion engine;
In the stop transition period from the start of the stop process of the internal combustion engine to the stop of the rotation of the internal combustion engine, the engine is configured such that the fuel pressure increases as the engine speed decreases in a range lower than the fuel pressure during the stop. Controlling the electric fuel pump according to the rotational speed;
When the internal combustion engine is restarted under the predetermined start condition, the first fuel injection is performed on the cylinder that has been stopped during the intake stroke,
A control apparatus for an internal combustion engine , which controls the variable valve mechanism after the predetermined stop condition is satisfied so as to increase a valve lift amount of the intake valve in a stop state during the intake stroke . An internal combustion engine that is stopped under a predetermined stop condition and restarted under a predetermined start condition, wherein a fuel injection valve is provided in an intake pipe upstream of the intake valve, and fuel is pumped to the fuel injection valve by an electric fuel pump. In an internal combustion engine
Controlling the electric fuel pump so that the fuel pressure supplied to the fuel injection valve is higher during operation of the internal combustion engine than during operation of the internal combustion engine;
In the stop transition period from the start of the stop process of the internal combustion engine to the stop of the rotation of the internal combustion engine, the engine is configured such that the fuel pressure increases as the engine speed decreases in a range lower than the fuel pressure during the stop. A control device for an internal combustion engine , which controls the electric fuel pump according to a rotational speed . The control apparatus for an internal combustion engine according to claim 1 or 2, wherein the fuel pressure during the stop of the internal combustion engine is increased as the temperature of the intake valve is lower .

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