JP4919878B2 - Intake control device for internal combustion engine - Google Patents

Description

  The present invention relates to an intake control device for an internal combustion engine having a variable valve mechanism that can continuously change the effective opening of an intake valve, and more particularly to a technique for ensuring intake negative pressure as required.

  Conventionally, in a general internal combustion engine (gasoline engine), the intake air amount is controlled by a throttle valve. However, in Patent Document 1, in order to reduce the throttle loss due to the throttle valve and improve fuel efficiency, A device that controls the intake air amount by variably controlling the operating angle (and the lift amount) is disclosed.

In Patent Document 1, throttle control of the throttle valve is also used in the small intake amount region. However, when the closing speed of the throttle valve is high, the operating angle and lift amount of the intake valve are controlled to be smaller in order to secure engine brake. is doing.
JP-A-9-25836

  As in Patent Document 1, in the case where the intake air amount is controlled by the effective opening determined by the operating angle and the lift amount of the intake valve, if the effective opening of the intake valve is reduced in a region where the target air amount is small, The intake negative pressure is reduced, and it becomes difficult to satisfy the negative pressure source for the vacuum booster that reduces the brake pedal force, the intake negative pressure for sucking the purge gas and blow-by gas into the intake system.

  If the throttle amount of the throttle valve is increased, the intake negative pressure can be secured, but the throttle loss increases and the fuel consumption is lowered.

  The present invention has been made paying attention to such a conventional problem, and an object of the present invention is to achieve both good fuel efficiency and necessary intake negative pressure while performing intake air amount control by an intake valve.

For this reason, the present invention
In an intake control device for an internal combustion engine, comprising: a variable valve mechanism that can continuously change the effective opening of the intake valve; and a control unit that controls the effective opening of the intake valve by the variable valve mechanism.
Means for determining a target cylinder air amount corresponding to the required torque based on the engine operating state, and setting a target effective opening of the intake valve according to the target cylinder air amount ;
Means for setting a lower limit value of an effective opening necessary for securing a predetermined intake negative pressure on the upstream side of the intake valve based on the engine rotational speed;
With
When the accelerator is released, the target effective opening is compared with the lower limit value, and the larger one is selected, so that the target effective opening is limited to the lower limit value or more and not lower than the lower limit value. It is characterized by.

  By limiting the target effective opening degree of the intake valve to a lower limit value or more as necessary, it is possible to ensure good fuel efficiency while ensuring the necessary intake negative pressure.

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

  FIG. 1 is a configuration diagram of an engine (internal combustion engine).

  The combustion chamber 52 defined by the piston 51 of each cylinder of the engine 1 is provided with an intake valve 54 and an exhaust valve 55 so as to surround the spark plug 53. The intake air passes through the intake passage 56 and is sucked into the combustion chamber 52 from the intake valve 54, and a manifold portion (intake manifold) 57 is disposed in the intake passage 56. Exhaust gas in the combustion chamber 52 is discharged from the exhaust valve 55 through the exhaust passage 58.

  The intake valve 54 is controlled by a variable valve mechanism 100 having variable valve operating characteristics. The variable valve mechanism continuously changes the first variable valve mechanism 10 that continuously changes the operating angle and lift amount of the intake valve 54 and the center phase of the operating angle of the intake valve 54, as will be described later. And a second variable valve mechanism 20. As for the exhaust valve 55, the valve characteristic is fixed in the present embodiment, but the valve characteristic may be variable by a variable valve mechanism similar to the intake valve.

  In the intake passage 56, an electric throttle valve 59 is provided upstream of the manifold portion 57. The intake passage 56 is also provided with an electromagnetic fuel injection valve 60 at the intake port portion of each cylinder.

  Here, the operation of the ignition plug 53, the first variable valve mechanism 10, the second variable valve mechanism 20, the electric throttle valve 59 and the fuel injection valve 60 is controlled by a control unit (ECU) 61.

  The ECU 61 detects a crank angle sensor 62 capable of detecting the engine rotational speed Ne together with the crank angle position θ and an accelerator opening (accelerator pedal depression amount) APO by outputting a crank angle signal in synchronization with the engine rotation. An accelerator pedal sensor 63, a hot-wire air flow meter 64 that measures the flow rate of air flowing into the manifold portion 57 upstream of the throttle valve 59 in the intake passage 56, and an intake air temperature sensor 65 that detects the temperature (intake air temperature) in the manifold portion 57. Etc. are input.

  The fuel injection timing and the fuel injection amount of the fuel injection valve 60 are controlled based on engine operating conditions, and the fuel injection amount is set to a desired air-fuel ratio with respect to a cylinder intake air amount controlled as described later. Control.

  The ignition timing by the spark plug 53 is controlled to MBT (optimum ignition timing on torque) or a knock limit based on engine operating conditions.

  FIG. 2 shows the first variable valve mechanism 10. Each cylinder is provided with a pair of intake valves 54. Above these intake valves 54, a hollow intake drive shaft 3 extends in the cylinder row direction. A swing cam 4 that contacts the valve lifter 54a of the intake valve 54 and opens and closes the intake valve 54 is fitted on the intake drive shaft 3 so as to be relatively rotatable.

  Between the intake drive shaft 3 and the swing cam 4, an electric first variable valve mechanism 10 that continuously changes the operating angle and lift amount of the intake valve 54 is provided. In the present embodiment, the effective opening corresponding to the average opening during the intake valve opening period is determined by the operating angle and lift amount of the intake valve 54. Since the operating angle and the lift amount are simultaneously changed as described above and one is detected and controlled, the other is also controlled at the same time. Therefore, only the operating angle will be described below. As a variable valve mechanism that can change the effective opening degree, either the operating angle or the lift amount may be continuously changed.

  At one end of the intake drive shaft 3, a second variable motion that continuously changes the intake center phase, which is the center phase of the intake operation angle, by changing the phase of the intake drive shaft 3 with respect to a crankshaft (not shown). A valve mechanism 20 is provided.

  As shown in FIGS. 2 and 3, the first variable valve mechanism 10 has a circular drive cam 11 that is fixedly provided eccentrically to the intake drive shaft 3 and is externally fitted to the drive cam 11 so as to be relatively rotatable. A ring-shaped link 12, a control shaft 13 that extends substantially parallel to the intake drive shaft 3 in the cylinder row direction, a circular control cam 14 that is fixedly provided eccentrically to the control shaft 13, and a relative to the control cam 14 A rocker arm 15 that is rotatably fitted and has one end connected to the tip of the ring-shaped link 12, and a rod-shaped link 16 connected to the other end of the rocker arm 15 and the swing cam 4. Yes. The control shaft 13 is driven to rotate within a predetermined control range via the gear train 18 by the electric actuator 17.

  With the above configuration, when the intake drive shaft 3 rotates in conjunction with the crankshaft, the ring-shaped link 12 moves substantially in translation through the drive cam 11 and the rocker arm 15 swings around the axis of the control cam 14. Then, the swing cam 4 swings via the rod-shaped link 16 and the intake valve 2 is driven to open and close.

  Further, by changing the rotation angle of the control shaft 13, the axial center position of the control cam 14 that becomes the swing center of the rocker arm 15 is changed, and the posture of the swing cam 4 is changed. As a result, the intake operation angle and the valve lift amount continuously change while the intake center phase remains substantially constant.

  Although a detailed description of the second variable valve mechanism that changes the operating angle center phase of the intake valve 54 is omitted, a known mechanism such as a hydraulic type, a friction braking type, or an electromagnetic braking type may be used.

  FIG. 4 is a control block diagram of the variable valve mechanism 10 and the electric throttle valve 59 that are made in the ECU 61.

  The target cylinder air amount calculation unit calculates a target cylinder air amount commensurate with the required torque based on the accelerator opening APO detected by the accelerator pedal sensor 63, the engine speed Ne detected by the crank angle sensor 62, and the like. .

  The target operating angle calculation unit calculates a target operating angle of the intake valve 2 according to the target cylinder air amount.

  The cylinder effective volume calculation unit calculates the cylinder effective volume corresponding to the intake stroke of the cylinder based on the operating state of the engine 1 and the operating characteristics of the intake valve 54, particularly the opening timing and closing timing determined by the operating angle and the operating angle center phase. To do.

  The target throttle opening calculation unit sets the target intake pressure required to obtain the target cylinder air amount with the cylinder effective volume in consideration of the detected value of the intake air temperature detected by the intake air temperature sensor 65 as a target. The target throttle opening obtained from the response (normative response) is calculated.

  Here, when the target cylinder air amount (required torque) is small, the target operating angle of the intake valve 54 is calculated to be a small value, and the intake negative pressure upstream of the intake valve 54 decreases as the cylinder intake air amount decreases. For this reason, there is a possibility that the negative pressure source of the vacuum booster that reduces the brake pedal force, the intake negative pressure for sucking the purge gas and the blow-by gas into the intake system may not be obtained sufficiently.

  Therefore, in the present embodiment, the following means is provided to limit the target operating angle of the intake valve 54 with the lower limit value for securing the intake negative pressure when the accelerator is opened, which increases the above possibility.

  The operating angle lower limit value setting unit sets the operating angle lower limit value of the intake valve 54 that can obtain the necessary intake negative pressure for each engine speed when the accelerator opening degree APO is equal to or less than a predetermined value close to zero. To do. For example, data obtained in advance by experiments or the like may be tabulated and searched based on the engine rotational speed. It is desirable to add and set the variation.

  The select high portion selects the larger one of the target operating angle calculated by the target operating angle calculating portion and the lower limit value set by the operating angle lower limit setting portion as the final target operating angle, and outputs it. To do. That is, the target operating angle is limited to be equal to or greater than the lower limit value.

  When the accelerator operating state is detected based on a signal from the accelerator pedal sensor, the target operating angle switching unit selects a target operating angle that is limited to a lower limit value or more that has passed through the select high unit, and the accelerator opening degree When it is detected that APO is larger than the accelerator release, the target operating angle calculated by the target operating angle calculation unit is selected as it is and is output to the first variable valve mechanism 10.

  In this way, when the accelerator is released, the target operating angle is limited to the lower limit value or more, so that the intake negative pressure required as a negative pressure source for the vacuum booster of the brake can be secured, and the brake pedal force can be reduced. An effect can be secured, and a suction amount can be secured in an intake system for purge gas and blow-by gas.

  In particular, in the present embodiment, the following effects can be obtained by restricting the target operating angle every time the accelerator is released to ensure the intake negative pressure.

  Since the brake operation is performed in conjunction with the accelerator release operation, the necessary intake negative pressure can be secured in real time.

  Every time the brake is operated, negative pressure is supplied from the negative pressure source of the vacuum booster and the negative pressure in the negative pressure source is weakened, but every time the accelerator is released, the intake negative pressure is increased and negative pressure is supplied to the negative pressure source. Therefore, the negative pressure in the negative pressure source can be secured efficiently.

  Except when the accelerator is released, the target operating angle is not limited, and it is set according to the required torque, so that the fuel efficiency can be maintained well.

  Even if the cylinder intake air amount is increased by setting the target operating angle to be equal to or greater than the lower limit value, the fuel injection amount is small even when the accelerator is released or the fuel injection amount is small even when it is not performed. .

  Further, when the target operating angle is set to the lower limit value or more, the throttle valve opening may be decreased by a predetermined amount, and the intake negative pressure can be increased to enhance the engine braking effect.

  In the above embodiment, the target operating angle is limited to the lower limit value or more when the accelerator is released. However, a predetermined operating condition other than the accelerator opening, for example, a low load region where the target cylinder intake air amount is a predetermined value or less. Thus, the target operating angle may be limited.

  Moreover, it can restrict | limit easily by comparing a target operating angle and a lower limit, and selecting the larger one like the said embodiment.

  In the above embodiment, the target operation is performed in the low intake amount region by cooperatively controlling the operation angle (effective opening) of the intake valve by the first variable valve mechanism 10 and the opening of the electric throttle valve 59. Although it was applied to the one where it is difficult to obtain intake negative pressure because the angle is small, it can be applied to other control methods, for example, a method that switches the throttle valve stepwise, and the same effect can be obtained. Of course.

1 is a diagram showing a configuration of an internal combustion engine (engine) according to an embodiment of the present invention. It is a perspective view which shows the variable valve mechanism provided in an engine same as the above. It is a partially expanded side view of a variable valve mechanism same as the above. It is a control block diagram of the 1st variable valve mechanism and electric throttle valve of embodiment same as the above.

Explanation of symbols

1 engine (internal combustion engine)
DESCRIPTION OF SYMBOLS 10 1st variable valve mechanism 20 2nd variable valve mechanism 54 Intake valve 57 Manifold part 59 Electric throttle valve 61 ECU
62 Crank angle sensor 63 Accelerator pedal sensor 64 Air flow meter 65 Intake air temperature sensor

Claims (3)

In an intake control device for an internal combustion engine, comprising: a variable valve mechanism that can continuously change the effective opening of the intake valve; and a control unit that controls the effective opening of the intake valve by the variable valve mechanism.
Means for determining a target cylinder air amount corresponding to the required torque based on the engine operating state, and setting a target effective opening of the intake valve according to the target cylinder air amount ;
Means for setting a lower limit value of an effective opening necessary for securing a predetermined intake negative pressure on the upstream side of the intake valve based on the engine rotational speed;
With
When the accelerator is released, the target effective opening is compared with the lower limit value, and the larger one is selected, so that the target effective opening is limited to the lower limit value or more and not lower than the lower limit value. An air intake control device for an internal combustion engine.   The intake control device for an internal combustion engine according to claim 1, further comprising an intake throttle valve, wherein the effective opening of the intake valve and the opening of the intake throttle valve are controlled in a coordinated manner.   3. The intake control device for an internal combustion engine according to claim 1, wherein the variable valve mechanism is configured to change an effective opening by simultaneously changing an operating angle and a lift amount of the intake valve. .

Images