JP2006112358A - Intake control device of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce vibrations at engine startup in an idle-stop vehicle or the like. <P>SOLUTION: The device is equipped with a cutoff valve control means (S440, S730, S 915, S1030) for controlling a cutoff valve (3) to be kept in a state of closure until restart from the time at which an engine is transferred to a stopping state when an engine stop condition is established. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an intake air control device for reducing engine vibration.

  A technique for increasing the engine output by making the lift timing of the intake valve and the exhaust valve of the engine variable according to the engine rotation speed is known.

  However, in such a technique, since the intake valve and the exhaust valve, which are part of the engine body, are directly controlled, the structure of the engine body is complicated.

Therefore, there is a technology that can provide a shut-off valve in the intake passage as a device independent of the engine body, and control the shut-off valve during the intake valve opening period to increase the intake air amount and increase the engine output. It is described in Patent Document 1.
Japanese Patent Laid-Open No. 62-294719

  There is also known an idle stop vehicle that can improve fuel efficiency by temporarily stopping the engine when the vehicle is stopped. In such an idle stop vehicle, when the stopped engine is restarted because the vehicle re-starts, the engine pressure vibrates due to the pressure increase in the cylinder during the compression stroke of the engine.

  When the above conventional technique is applied to an idle stop vehicle, the pressure in the cylinder further increases due to the intake air amount increased by the control of the shut-off valve, so that the vibration at the start of the engine further increases.

  The present invention has been made paying attention to such conventional problems, and an object of the present invention is to provide an engine intake control device capable of reducing vibration at the time of engine start in an idle stop vehicle or the like. .

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention provides a shutoff valve (3) provided in an intake passage (2) for supplying intake air to a combustion chamber (5) of an engine, and capable of shutting off the intake passage (2) by closing the valve. An engine stop condition determining means (S420) for determining a stop condition, and a shutoff valve between the start of the operation for shifting the engine to the stop state and the restart of the engine when the engine stop condition is satisfied. (3) It is provided with the cutoff valve control means (S440, S730, S915, S1030) which controls so that it may hold in a valve closing state, It is characterized by the above-mentioned.

  According to the present invention, since the intake passage is shut off from when the engine shifts to a stopped state until it is restarted, the intake amount of intake air into the combustion chamber is suppressed and the pressure of the intake passage downstream of the shut-off valve is reduced. This state can be maintained until the next start. Therefore, it is possible to reduce the vibration accompanying the engine start by suppressing the pressure increase in the combustion chamber during the compression stroke at the next start.

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

(First embodiment)
FIG. 1 is an overall configuration diagram showing an intake control device for an engine according to the present invention. The engine combustion chamber 5 is defined by a cylinder head 6, a cylinder block 9, and a piston 10. An intake passage 2 that introduces intake air and an exhaust passage 8 that leads exhaust gas are connected to the combustion chamber 5.

  The intake passage 2 introduces intake air into the combustion chamber 5 via the intake valve 1 provided in the cylinder head 6. The exhaust passage 8 leads exhaust from the combustion chamber 5 through an exhaust valve 7 provided in the cylinder head 6. For each cylinder, the intake passage 2 is provided with an injector 18 for injecting fuel, and a shut-off valve 3 that is disposed upstream of the cylinder and can shut off the intake passage 2. A throttle valve 17 for controlling the intake air amount of the cylinder is provided upstream of the intake passage 2 and at a merging portion of each intake passage 2. In order to open and close the shut-off valve 3 and the throttle valve 17, the shut-off valve driving device 26 and the throttle valve driving device 27 are provided.

  A spark plug 12 is provided in the combustion chamber 5 so that the tip faces the combustion chamber 5, and the air-fuel mixture introduced from the intake passage 2 is ignited by the spark plug 12 and burned. The piston 10 is slid downward by the energy generated by the combustion in the combustion chamber 5. The connecting rod 13 connected to the piston 10 and the crank 14 connected to the connecting rod 13 cause the vertical movement of the piston 10 to rotate the crank 14. Converted into movement. An engine starting motor 15 is provided in the vicinity of the crank 14. The engine starting motor 15 compresses the combustion chamber 5 by rotating the crank 14 when starting the engine, and starts the engine. The battery 16 supplies electric power to the engine starting motor 15 when the engine is started.

  The detection signals from the accelerator fully closed switch 19, the clutch switch 20, the vehicle speed sensor 21, the transmission neutral switch 22, the voltage sensor 23, the crank angle sensor 24, and the throttle valve opening sensor 25 are transmitted to the ECU 4. The ECU 4 controls the spark plug 12, the injector 18, the engine starting motor 15, the shut-off valve 3, and the throttle valve 17 based on each detection signal. Here, the accelerator full close switch 19 detects that the operation amount of the accelerator pedal is zero. The clutch switch 20 detects that the clutch is engaged. The vehicle speed sensor 21 detects the vehicle speed. A transmission neutral switch 22 detects that the transmission is neutral. The voltage sensor 23 detects the voltage of the battery 16. The crank angle sensor 24 detects the rotation angle of the crank 14. The throttle valve opening sensor 25 detects the opening of the throttle valve 17.

  The ECU 4 closes the shut-off valve 3 at a predetermined timing to shut off intake air at a predetermined timing when the engine is temporarily stopped, such as when the engine is idling, and suppresses an increase in pressure in the combustion chamber 5 when the engine is started. In order to suppress the vibration at the time of engine start.

  Control performed by the ECU 4 will be described with reference to FIG. FIG. 2 is a flowchart showing the control of the engine intake control device according to the present invention, which is executed for each shut-off valve 3 provided in each cylinder. In addition, this control is repeatedly performed every predetermined time (for example, 10 ms).

  In step S100, an idle stop flag Fis and an engine starting flag Fst are read. Here, the idle stop flag Fis is a flag indicating that the idle stop condition is satisfied, and is set to Fis = 1 when the idle stop condition is satisfied, and Fis = 0 when not satisfied. The engine starting flag Fst is a flag indicating that the engine is starting from the idle stop state, and is set to Fst = 1 or Fst = 2 during engine starting, and Fst = 0 when the engine is not starting. The engine start flag Fst 1 and 2 are set according to the stage of engine start, Fst = 1 at the initial start, and then Fst = 2 when the engine rotation speed becomes equal to or higher than the rotation speed at which fuel supply is started. Is set. The initial values are Fis = 1 and Fst = 0.

  In step S200, it is determined whether or not the idle stop flag Fis is Fis = 0. If Fis = 0, the process proceeds to step S300, and if Fis = 1, the process proceeds to step S500.

  In step S300, it is determined whether the engine starting flag Fst is zero. If Fst = 0, the process proceeds to step S400, and if Fst = 1 or Fst = 2, the process proceeds to step S600.

  In step S400, shut-off valve control during normal operation is performed. Here, the normal operation time is not an idle stop state but a normal operation state during which the engine is not started. A detailed control method will be described later.

  In step S500, shut-off valve control is performed in the idle stop state. A detailed control method will be described later.

  In step S600, it is determined whether the engine starting flag Fst is Fst = 1. If Fst = 1, the process proceeds to step S700, and if Fst = 2, the process proceeds to step S800.

  In step S700, shut-off valve control is performed at an initial stage in engine start from the idle stop state. A detailed control method will be described later.

  In step S800, shut-off valve control is performed at a later stage in engine start from the idle stop state. A detailed control method will be described later.

  Next, the shut-off valve control during normal operation performed in step S400 of FIG. 2 will be described with reference to FIG. FIG. 3 is a flowchart showing control of the shutoff valve 3 during normal operation. This control is performed when the idle stop flag Fis = 0 and the engine starting flag Fst = 0.

  In step S410, the vehicle speed, the accelerator fully closed switch signal, the clutch switch signal, the transmission neutral switch signal, and the battery voltage are read.

  In step S420, it is determined whether an idle stop condition is satisfied. If established, the process proceeds to step S430, and if not established, the process proceeds to step S460. Here, the idle stop condition is that the vehicle speed is a predetermined value or less (for example, 5 km or less), the accelerator is fully closed (the accelerator operation amount is zero), the clutch is engaged, the transmission is neutral, and the battery voltage is a predetermined value or more (for example, 11V or more).

  In step S430, the fuel supply from the injector 18 is stopped.

  In step S440, the shut-off valve 3 is kept closed. As a result, the intake air is blocked regardless of whether the intake valve 1 is open or closed.

  In step S450, the idle stop flag Fis is set to Fis = 1.

  On the other hand, when it is determined in step S420 that the idle stop condition is not established, the opening / closing control of the shut-off valve 3 is performed in step S460. For example, the opening / closing control of the shut-off valve 3 is performed by synchronizing the shut-off valve 3 with the intake valve 1 so that the shut-off valve 3 opens after the intake valve 1 is opened when the engine speed is a predetermined value or less. Open and close. As a result, the substantial valve overlap period is shortened, and the engine torque in the low engine speed range can be increased.

  Such control is performed during engine operation separately from the shut-off valve control of the present embodiment for the purpose of increasing the output of the engine, and the shut-off valve 3 is in a period until the predetermined condition described above is satisfied. The opening / closing control is performed in association with the intake valve 1 in accordance with the rotational speed of the engine. In the present embodiment, the opening / closing control of the shutoff valve 3 during engine operation may not be performed.

  Next, the shutoff valve control at the time of idling stop performed in step S500 of FIG. 2 will be described with reference to FIG. FIG. 4 is a flowchart showing the control of the shut-off valve 3 at the time of idling stop. This control is performed when the idle stop flag Fis = 1 and the engine starting flag Fst = 0.

  In step S510, a crank angle signal, a clutch switch signal, a transmission neutral switch signal, and a battery voltage are read.

  In step S520, it is determined whether an engine start condition is satisfied. If established, the process proceeds to step S530, and if not established, the process proceeds to step S550. Here, the engine start condition is when the battery voltage is lower than a predetermined value (for example, 10.5 V or lower) and the transmission is neutral, or when the clutch is not engaged (the clutch pedal is operated). This is a case where either one is satisfied.

  In step S530, the engine starting motor 15 is activated to start the engine.

  In step S540, the idle stop flag Fis is set to Fis = 0, and the engine starting flag Fst is set to Fst = 1.

  On the other hand, when it is determined in step S520 that the engine start condition is not established, in step S550, the shut-off valve control corresponding to the crank angle is performed.

  Here, the shut-off valve control based on the crank angle in step S550 will be described with reference to FIG. FIG. 5 is a flowchart showing shut-off valve control based on the crank angle in a four-cycle in-line four-cylinder engine in which the operation period of the intake cam is a crank angle of 240 degrees and the valve opening timing of the intake valve 1 is an intake top dead center. Here, the shut-off valve 3 is driven by a shut-off valve driving device 26 that operates based on a signal from the ECU 4. The shut-off valve drive device 26 is driven to close the shut-off valve 3 upon receiving power supply, and is driven to open the shut-off valve 3 by stopping the power supply.

  In step S551, the crank angle CA is read. Here, the crank angle CA is reset to 0 every two rotations (720 degrees), with the intake top dead center of the first cylinder being 0 degrees.

  In step S552, it is determined whether or not the crank angle CA is within a range of 0 degrees to 240 degrees. When it is within the range, the process proceeds to step S554, and when it is not within the range, the process proceeds to step S553. When the crank angle CA is in the range of 0 degrees to 240 degrees, the intake valve 1 of the first cylinder is being opened. Therefore, in step S552, it is determined whether or not the intake valve 1 of the first cylinder is being opened. It will be judged.

  In step S553, the shutoff valve 3 of the first cylinder is opened.

  In step S554, it is determined whether or not the crank angle CA is within a range of 180 degrees to 420 degrees, that is, whether or not the intake valve 1 of the third cylinder is being opened. If the valve is open, the process proceeds to step S556, and if the valve is closed, the process proceeds to step S555.

  In step S555, the shutoff valve 3 of the third cylinder is opened.

  In step S556, it is determined whether or not the crank angle CA is within a range of 360 to 600 degrees, that is, whether or not the intake valve 1 of the fourth cylinder is being opened. If the valve is open, the process proceeds to step S558, and if the valve is closed, the process proceeds to step S557.

  In step S557, the shutoff valve 3 of the fourth cylinder is opened.

  In step S558, it is determined whether or not the crank angle CA is in the range of 540 to 720 degrees or in the range of 0 to 60 degrees, that is, whether or not the intake valve 1 of the second cylinder is being opened. To do. If the valve is open, the process ends. If the valve is closed, the process proceeds to step S559.

  In step S559, the shutoff valve 3 of the second cylinder is opened.

  Next, the shutoff valve control in the initial stage after engine start performed in step S700 of FIG. 2 will be described with reference to FIG. FIG. 6 is a flowchart showing the control of the shut-off valve 3 in the initial stage after the engine is started. This control is performed when the idle stop flag Fis = 0 and the engine starting flag Fst = 1.

  In step S710, the engine speed is read. The engine speed is calculated based on the detection value of the crank angle sensor 24.

  In step S720, it is determined whether or not the engine rotation speed is lower than the fuel supply start rotation speed. If the engine rotation speed is lower than the fuel supply start rotation speed, the process proceeds to step S730. If the engine rotation speed is equal to or higher than the fuel supply start rotation speed, the process proceeds to step S740. The fuel supply start rotation speed is a rotation speed (for example, 400 rpm) at which fuel supply is started when the engine is started. When the engine rotation speed is lower than the fuel supply start rotation speed, it is determined that the engine is in an initial stage, and when the engine rotation speed is equal to or higher than the fuel supply start rotation speed, it is determined as a later stage.

  In step S730, the shut-off valve 3 is kept closed. As a result, the intake air is blocked regardless of whether the intake valve 1 is open or closed.

  In step S740, opening / closing control of the shutoff valve 3 is performed. The open / close control method for the shutoff valve 3 is the same as that in step S460 in FIG.

  In step S750, fuel injection of the injector 18 is started.

  In step S760, the engine starting flag Fst is set to Fst = 2.

  Next, the shut-off valve control in the later stage after the engine start performed in step S800 of FIG. 2 will be described with reference to FIG. FIG. 7 is a flowchart showing the control of the shut-off valve 3 in the later stage after the engine is started. This control is performed when the idle stop flag Fis = 0 and the engine starting flag Fst = 2.

  In step S810, the engine speed is read.

  In step S820, it is determined whether or not the engine rotation speed is equal to or higher than the self-supporting determination rotation speed. If the engine rotational speed is equal to or higher than the self-supporting determination rotational speed, the process proceeds to step S830. If the engine rotational speed is lower than the self-supporting determination rotational speed, the process ends. The self-supporting determination rotational speed is a rotational speed (for example, 500 rpm) for determining whether or not the engine is in a state where it can rotate independently by combustion of fuel without depending on the driving force of the engine starting motor 15. is there.

  In step S830, the engine starting motor 15 is stopped.

  In step S840, the idle stop flag Fis is set to Fis = 0, and the engine starting flag Fst is set to Fst = 0.

  Next, the contents of the intake control device for an engine according to the present invention will be described with reference to FIGS. FIG. 8 is a graph showing the relationship between the cylinder volume and the cylinder pressure of the engine when the control of the intake control device for the engine according to the present invention is not performed. FIG. 9 is a diagram showing the relationship between the cylinder volume and the cylinder pressure of the engine when the control of the intake control device for the engine according to the present invention is performed.

  First, the case where the shutoff valve closing control of the intake control device for an engine according to the present invention is not performed will be described with reference to FIG. While discharging the gas in the cylinder in the exhaust stroke, the volume is reduced and the pressure becomes atmospheric pressure (state a to state b). After that, since the air-fuel mixture having the same volume as that exhausted in the intake stroke is sucked, the volume and pressure become the same as the initial state (state a) of the exhaust stroke (state b to state c). In the compression stroke, the intake air is compressed almost adiabatically, so that the pressure rises so as to be almost inversely proportional to the decrease in volume (state c to state d). Thereafter, the process proceeds to the expansion stroke and returns to the state a (state d to state a).

  Thus, in the compression top dead center (state d), the in-cylinder pressure P1 is higher than the atmospheric pressure. Therefore, by entering the compression stroke when starting the engine, the in-cylinder pressure P1 becomes an oscillating force and the vibration of the engine increases.

  Next, a case where the shutoff valve closing control of the intake control device for an engine according to the present invention is performed will be described with reference to FIG. The diagram shown in FIG. 9 shows the relationship between the cylinder volume and the cylinder pressure from immediately before the engine is stopped until the complete stop or from the start until the engine start motor 15 is stopped. Has stopped. In the exhaust stroke, the volume decreases and the pressure becomes atmospheric pressure (state a to state b). Thereafter, the shut-off valve 3 is kept closed in the intake stroke, so that fresh air is not sucked into the cylinder and substantially adiabatically expands (state b to state c). Since the intake air is compressed almost adiabatically during the compression stroke, the pressure rises so as to be almost inversely proportional to the decrease in volume, but the pressure in the cylinder is atmospheric at the end of the exhaust stroke, and fresh air is sucked in the subsequent intake stroke. Therefore, even if compressed, the pressure in the cylinder does not exceed atmospheric pressure and reaches the compression top dead center (state c to state d). Thereafter, the process proceeds to the expansion stroke and returns to the state a (state d to state a).

  Thus, in the compression top dead center (state d), the cylinder pressure P2 becomes atmospheric pressure. Therefore, in the compression stroke at the time of starting the engine, the cylinder pressure P2 does not become higher than the atmospheric pressure, so that the vibration generated in the engine can be suppressed by suppressing the excitation force.

  The operation will be described by summarizing the above control. In the engine intake control device according to the present embodiment, the idle stop condition is satisfied during normal operation, and the shutoff valve 3 is held in the closed state when the engine is shifted to the stopped state. As a result, the intake passage is shut off, so that the crank rotates inertially until the engine is completely stopped, and even if the intake valve is opened accordingly, fresh air is not inhaled, and the shut-off valve 3 A negative pressure is formed in the intake passage 2 and the combustion chamber 5 downstream of. Thereafter, even when the engine is completely stopped, the shut-off valve 3 is kept closed.

  Subsequently, even if the engine start condition is satisfied and the engine start motor 15 is started, the shutoff valves 3 in all the cylinders are held in the closed state until the engine rotation speed becomes equal to or higher than the fuel supply start rotation speed. As a result, even if the crank is rotated by the driving force of the engine starting motor 15, a negative pressure is maintained in the intake passage 2 downstream of the combustion chamber 5 and the shutoff valve 3, so that an increase in pressure can be suppressed. .

  Further, in the cylinder in which the intake valve 1 is closed during the idle stop after the engine is completely stopped, the negative pressure in the combustion chamber 5 is maintained regardless of whether the shut-off valve 3 is opened or closed, so that the intake valve 1 is opened. The inside cylinder is determined based on the crank angle, and the shutoff valve 3 of the intake passage 2 connected to the cylinder is opened. Thereby, the electric power supply to the shut-off valve drive device 26 that holds the shut-off valve 3 in the closed state by electric power can be stopped.

  As described above, in this embodiment, when the engine is stopped and the crank 14 is rotating by inertia, the intake air is blocked and the blocked state is maintained until the next start. Therefore, the vibration of the engine can be suppressed by suppressing the pressure increase in the cylinder and suppressing the excitation force in the compression stroke at the next start.

  Further, since the shut-off state is maintained until the engine reaches a predetermined rotational speed at the next start, the increase in the pressure in the cylinder is suppressed in the compression stroke at the next start, and the rotation of the crank 14 caused by the increase in the pressure in the cylinder is suppressed. Reaction force can be suppressed. Therefore, it is possible to shorten the time required for the restart by shortening the time required for the engine speed to reach a predetermined speed.

  Further, the power supply to the shutoff valve 3 is stopped for the cylinders in which the intake valve 1 is closed while the engine is stopped. As a result, the shutoff valve 3 is opened, but the intake valve 1 is closed, so that the shutoff state when the engine is stopped can be maintained. Therefore, power consumption can be suppressed and deterioration of fuel consumption can be prevented without impairing the vibration reduction effect of the engine.

(Second Embodiment)
The present embodiment is the same as the first embodiment except for the control of the shut-off valve 3 during normal operation. In the following embodiments, description of parts that perform similar processing will be omitted as appropriate.

  The shut-off valve control during normal operation will be described with reference to FIG. FIG. 10 is a flowchart showing control of the shut-off valve 3 during normal operation in the second embodiment. This control is performed when the idle stop flag Fis = 0 and the engine starting flag Fst = 0.

  In step S901, the vehicle speed, the accelerator fully closed switch signal, the clutch switch signal, the transmission neutral switch signal, and the battery voltage are read.

  In step S902, it is determined whether or not fuel injection is being performed by the injector 18. If fuel injection is being performed, the process proceeds to step S903, and if not, the process proceeds to step S905.

  In step S903, the fuel injection execution flag F1 is set to F1 = 1. The fuel injection execution flag is a flag indicating that fuel injection has been executed in the current combustion cycle, and indicates that fuel injection has been executed when F1 = 1, and that fuel injection has not been executed when F1 = 0. Indicates. Note that the initial value of the fuel injection execution flag F1 is F1 = 0, and F1 = 1 only once for each combustion cycle.

  In step S904, the intake air cut permission flag F0 is set to F0 = 0. The intake cutoff permission flag F0 is a flag indicating that the intake valve may be closed by closing the cutoff valve 3, and indicates that the cutoff of the cutoff valve 3 is permitted when F0 = 1, and F0 = 0. Indicates that the shut-off valve 3 is prohibited to close.

  On the other hand, if it is determined in step S902 that fuel injection is not being performed, the process proceeds to step S905, where it is determined whether the fuel injection flag is F1 = 1, that is, whether fuel injection has been performed in the current combustion cycle. judge. If F1 = 1, the process proceeds to step S906, and if F1 = 0, the process proceeds to step S911.

  In step S906, it is determined whether the engine is in the intake stroke. If it is an intake stroke, it will progress to step S907, and if it is not an intake stroke, it will progress to step S908.

  In step S907, the intake stroke flag F2 is set to F2 = 1. The intake stroke flag F2 is a flag indicating that the intake stroke has ended in the current combustion cycle. When F2 = 1, the intake stroke has ended. When F2 = 0, the intake stroke has not been completed. It shows that.

  On the other hand, when it is determined in step S906 that the engine is not in the intake stroke, the flow proceeds to step S908, and it is determined whether or not the intake stroke flag F2 is F2 = 1, that is, whether or not the intake stroke is completed in the current combustion cycle. judge. If F2 = 1, the process proceeds to step S909, and if F2 = 0, the process proceeds to step S904.

  In step S909, the fuel injection execution flag F1 is set to F1 = 0.

  In step S910, the intake stroke flag F2 is set to F2 = 0.

  In step S911, the intake air cut permission flag F0 is set to F0 = 1.

  In step S912, it is determined whether an idle stop condition is satisfied. If established, the process proceeds to step S913, and if not established, the process proceeds to step S917. The idle stop condition is the same as step S420 in the first embodiment.

  In step S913, the fuel supply from the injector 18 is stopped.

  In step S914, it is determined whether or not the intake cutoff permission flag F0 is F0 = 1, that is, whether or not the intake valve may be closed by closing the cutoff valve 3. If F0 = 1, the process proceeds to step S915, and if F0 = 0, the process proceeds to step S917.

  In step S915, the shut-off valve 3 is kept closed. As a result, the intake air is blocked regardless of whether the intake valve 1 is open or closed.

  In step S916, the idle stop flag Fis is set to Fis = 1.

  On the other hand, when it is determined in step S912 that the idle stop condition is not satisfied, or when it is determined that F0 = 0 in step S914, opening / closing control of the shutoff valve 3 is performed in step S917. The opening / closing control of the shut-off valve 3 is the same as step S460 of the first embodiment.

  The operation will be described by summarizing the above control. In the intake control device for an engine in the present embodiment, when the idle stop condition is satisfied during normal operation, fuel injection is not executed in the current combustion cycle, or the intake stroke is ended after being executed. The shut-off valve 3 is closed only for the cylinders that are present. Here, if fuel injection is being performed, the intake air is shut off by closing the shut-off valve 3, so that the air-fuel mixture in the combustion chamber 5 becomes excessive. Further, since the injector 18 injects fuel before the intake stroke, the air-fuel mixture in the combustion chamber 5 becomes excessive when the shut-off valve 3 is closed before the intake stroke after fuel injection ends. Therefore, the air-fuel mixture in the combustion chamber 5 becomes excessively rich by closing the shut-off valve 3 while avoiding the fuel injection being executed or the end of the intake stroke after fuel injection when the idle stop condition is satisfied. Can be prevented.

  As described above, in the present embodiment, control is performed so that the shutoff valve 3 is not closed when the idle stop condition is established during normal operation and fuel injection is being performed or before the intake stroke after fuel injection is completed. it can. Accordingly, it is possible to avoid deterioration of exhaust gas properties by avoiding that the air-fuel ratio becomes excessive due to the shut-off of intake air and the unburned fuel is discharged.

(Third embodiment)
In this embodiment, the engine shown in the block diagram of the present invention in FIG. 1 is replaced with a direct injection engine in which the injector 18 directly injects fuel into the cylinder. Controls other than the control of the shut-off valve 3 in the initial stage after the engine start are the same as those in the first embodiment.

  Hereinafter, the shut-off valve control in the initial stage after engine startup will be described with reference to FIG. FIG. 11 is a flowchart showing the control of the shut-off valve 3 in the initial stage after engine start in the third embodiment. This control is performed when the idle stop flag Fis = 0 and the engine starting flag Fst = 1.

  In step S1010, the engine speed is read. The engine speed is calculated based on the detection value of the crank angle sensor 24.

  In step S1020, it is determined whether the engine speed is lower than the fuel supply start speed. If the engine rotation speed is lower than the fuel supply start rotation speed, the process proceeds to step S1030. If the engine rotation speed is equal to or higher than the fuel supply start rotation speed, the process proceeds to step S1050.

  In step S1030, the shutoff valve 3 is kept closed. As a result, the intake air is blocked regardless of whether the intake valve 1 is open or closed.

  In step S1040, the cutoff valve closing flag F3 is set to F3 = 1. The shutoff valve closing flag F3 is a flag indicating that the shutoff valve 3 is closed. When F3 = 1, the shutoff valve 3 is closed, and when F3 = 0, the shutoff valve 3 is shut off. It shows that the valve 3 is opened.

  In step S1050, it is determined whether or not the cutoff valve 3 closing flag F3 is F3 = 1, that is, whether or not the cutoff valve 3 is closed. If F3 = 1, the process proceeds to step S1060, and if F3 = 0, the process proceeds to step S1080.

  In step S1060, it is determined whether the engine is in an exhaust stroke. If it is the exhaust stroke, the process proceeds to step S1070, and if it is not the exhaust stroke, the process proceeds to step S1030.

  In step S1070, the cutoff valve closing flag F3 is set to F3 = 0.

  In step S1080, opening / closing control of the shutoff valve 3 is performed. The open / close control method of the shut-off valve 3 is the same as step S460 of the first embodiment.

  In step S1090, since the shut-off valve 3 is not held in the closed state, the fuel injection of the injector 18 is started.

  In step S1100, the engine starting flag Fst is set to Fst = 2.

  The operation will be described by summarizing the above control. In the engine intake control device according to the present embodiment, when the engine is started from the idle stop state, the engine rotational speed reaches the fuel supply start rotational speed, and the shutoff valve 3 is held in the closed state. In a certain cylinder, the shutoff valve 3 is continuously held in the closed state only when the engine has not finished the intake stroke to the expansion stroke. Here, in the direct injection engine, the injector 18 performs fuel injection during the period from the intake stroke to the expansion stroke. Therefore, if the shutoff valve 3 is closed and fuel injection is permitted during this time, the mixture in the combustion chamber 5 becomes excessively rich. Become. Therefore, when the engine rotational speed reaches the fuel supply start rotational speed, in the cylinder in which the shutoff valve 3 is closed, fuel supply is prohibited while the shutoff valve 3 is kept closed until the exhaust stroke is reached. Thereby, it is possible to prevent the air-fuel mixture in the combustion chamber 5 from becoming excessively rich.

  As described above, in the present embodiment, it is possible to avoid fuel injection while the shutoff valve 3 is closed between the intake stroke and the expansion stroke that may be injected in the direct injection engine. Accordingly, it is possible to avoid deterioration of exhaust gas properties by avoiding that the air-fuel ratio becomes excessive due to the shut-off of intake air and the unburned fuel is discharged.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

1 is an overall configuration diagram of an intake control device for an engine according to the present invention. It is the flowchart which showed control of the intake control apparatus of the engine by this invention. It is the flowchart which showed the cutoff valve control at the time of normal driving | operation. It is the flowchart which showed the cutoff valve control at the time of idle stop. It is the flowchart which showed the cutoff valve control by a crank angle. It is the flowchart which showed the shut-off valve control in the initial stage after engine starting. It is the flowchart which showed the shut-off valve control in the latter stage after engine starting. It is the diagram which showed the relationship between the cylinder volume of an engine and cylinder pressure when not controlling the intake control device of the engine concerning this invention. It is the diagram which showed the relationship between the cylinder volume of an engine and cylinder pressure at the time of performing control of the engine intake control apparatus concerning this invention. It is the flowchart which showed control of the cutoff valve at the time of normal operation in 2nd Embodiment. It is the flowchart which showed control of the cutoff valve in the initial stage after engine starting in 3rd Embodiment.

Explanation of symbols

1 intake valve 2 intake passage 3 shut-off valve 4 engine control unit (ECU)
5 Combustion chamber 6 Cylinder head 7 Exhaust valve 8 Exhaust passage 9 Cylinder block 10 Piston 12 Spark plug 13 Connecting rod 14 Crank 15 Engine starter motor 16 Battery 17 Throttle valve 18 Injector 19 Accelerator fully closed switch 20 Clutch switch 21 Vehicle speed sensor 22 Transmission Neutral switch 23 Voltage sensor 24 Crank angle sensor 25 Throttle valve opening sensor 26 Shut-off valve drive device 27 Throttle valve drive device

Claims (5)

A shut-off valve that is provided in an intake passage for supplying intake air to a combustion chamber of the engine and can close the intake passage by closing the valve;
Engine stop condition determining means for determining the engine stop condition;
When the engine stop condition is satisfied, control is performed so that the shutoff valve is maintained in a closed state from the start of the operation of shifting the engine to the stop state until the engine is restarted. Shut-off valve control means;
An intake control device for an engine, comprising: Engine restart condition determining means for determining the engine restart condition;
The shut-off valve control means controls to keep the shut-off valve closed until the engine speed exceeds a predetermined value when the engine is restarted when the engine is restarted. ,
The engine intake control device according to claim 1. Each intake passage connected to each of the plurality of cylinders of the engine includes a shut-off valve and a fuel injection device,
The shut-off valve control means holds the shut-off valve in a closed state only in a cylinder that is not performing fuel injection and that has completed the intake stroke after execution of the immediately preceding fuel injection when the engine stop condition is satisfied. To control,
The intake control apparatus for an engine according to claim 1 or 2, characterized in that The shut-off valve provided in each intake passage connected to each of a plurality of cylinders of the engine;
A fuel injection device provided for each cylinder to face the cylinder;
Fuel injection start determining means for determining an operation start condition of the fuel injection device when starting the engine;
A fuel injection control means for prohibiting fuel injection in a cylinder in which the shutoff valve is held closed when an operation start condition of the fuel injection device is satisfied;
The shutoff valve control means closes the shutoff valve of the intake passage connected to the cylinder until the exhaust stroke is reached in a cylinder in which intake air is shut off when an operation start condition of the fuel injection device is satisfied Control to hold on,
The intake control apparatus for an engine according to claim 1 or 2, characterized in that The shut-off valve provided in each intake passage connected to each of a plurality of cylinders of the engine;
Electromagnetic driving means for holding the shutoff valve in a closed state by supplying electric power,
The shut-off valve control means is connected to the cylinder for which the intake valve is closed when the engine is in a stopped state until the operation for shifting the engine to the operating state is started. Stopping the supply of electric power to the electromagnetic driving means provided in the intake passage;
The engine intake control device according to any one of claims 1 to 4, wherein the engine intake control device is provided.

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