JP2897570B2 - Intake control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake control system for an internal combustion engine, and more particularly to an intake control system for an internal combustion engine having an intake throttle valve and an intake control valve and performing a Miller cycle operation.

[0002]

2. Description of the Related Art An intake control valve, which is controlled to open and close, is provided in an intake passage for supplying intake air to a combustion chamber of an internal combustion engine via an intake valve. 2. Description of the Related Art An intake control device that performs a Miller cycle operation of an internal combustion engine by opening a valve and closing the valve during the opening period of the intake valve is known.

[0003] That is, during the Miller cycle operation, the amount of intake air supplied to the cylinder is not adjusted by the intake throttle valve.
The pumping loss can be reduced by controlling and adjusting the opening timing and period of the intake control valve that is controlled to open and close. However, when the Miller cycle operation is performed during high load and high rotation, there is a problem that the intake control valve is closed during the intake stroke, resulting in a shortage of intake air and insufficient output. I do.

In order to solve the above problem, there has been proposed an intake control device in which a mirror cycle operation is performed during low-load low-speed rotation, while an Otto-cycle operation is performed during high-load high-speed rotation to secure output (Japanese Patent Application Laid-Open No. H10-260,009). Sho 61-10691
8 gazette).

[0005]

However, in the intake control device according to the above proposal, when the state of the engine suddenly shifts from a low-load low-rotation state to a high-load high-rotation state, the intake air amount sharply increases and a torque shock occurs. Can not be avoided. The present invention has been made in view of the above problems,
It is an object of the present invention to provide an intake control device that does not generate torque shock even when the operation mode is changed between the Miller cycle operation state and the Otto cycle operation state.

[0006]

SUMMARY OF THE INVENTION An intake control system for an internal combustion engine according to the present invention is provided in an intake passage of the internal combustion engine to adjust the amount of intake air supplied to the internal combustion engine by controlling its opening degree. A throttle valve and intake timing control for adjusting the amount of intake air supplied to the internal combustion engine by controlling an intake air supply period which is provided in the intake passage downstream of the intake throttle valve and communicates the combustion chamber with the intake passage. First control means for opening the intake throttle valve to an opening degree at which no throttle loss occurs and adjusting the intake air amount by controlling the intake supply period of the intake timing control means in accordance with the operating state of the internal combustion engine; A second control unit that adjusts the intake air amount by controlling an opening of an intake throttle valve in accordance with an operation state of the internal combustion engine; a control state by the first control unit; and a control state by the second control unit. When switching When the amount of change in the intake supply period per unit time is equal to or greater than a predetermined value, the intake supply period of the intake timing control unit is longer than the intake supply period controlled by the first control unit and the second control is performed. A transient control means for controlling the intake air supply period shorter than the intake air supply period controlled by the means.

[0007]

In the intake control apparatus for an internal combustion engine according to the present invention, the Miller cycle operation is performed in the control state by the first control means, and the Otto cycle operation is performed in the control state by the second control means. When the change amount of the intake supply period per unit time at the time of switching between the control state by the first control means and the control state by the second control means is equal to or more than a predetermined value, the intake supply period of the intake control means Is controlled to be longer than the intake supply period during the Miller cycle operation and shorter than the intake supply period during the Otto cycle operation, thereby realizing a smooth change in the operating state.

[0008]

1 and 2 show the construction of an embodiment of an intake control device for an internal combustion engine according to the present invention. A combustion chamber 4 formed by a cylinder block 1, a piston 2 and a cylinder head 3 is provided. An air-fuel mixture is supplied from an intake port 6 via a pair of intake valves 5.

The combustion gas generated in the combustion chamber is discharged to an exhaust passage through a pair of exhaust valves 7. The intake port 6 is connected to a surge tank 9 by an intake branch pipe 8, and the surge tank 9 is connected to an air cleaner 11 via an intake pipe 10. The surge tank 9 also serves as a branch of an intake branch pipe connected to another cylinder. An air flow meter 12 is provided in the intake pipe 10 and a step motor 13 is provided downstream thereof.
And an intake throttle valve 14 driven by the pump. An intake control valve 16 that is opened and closed by an electromagnetic actuator 15 is disposed in the intake branch pipe 8.

Further, a fuel injection valve 17 for injecting fuel toward the intake port 6 is attached to the intake branch pipe 8 downstream of the intake control valve 16. Control unit 2 of intake control device
Reference numeral 0 denotes a microcomputer system, for example, which is connected to an accelerator opening sensor 22 for detecting a depression amount of an accelerator pedal 21, a rotation speed sensor 23 for detecting an internal combustion engine speed, and an air flow meter 12, and is connected to an internal combustion engine state quantity. Read.

A command signal for driving a step motor 13 for driving the intake throttle valve 13 and an electromagnetic actuator 15 for driving the intake control valve 16 is output from the control unit. FIG. 3 is a flowchart of a main control routine executed by the control unit. In step 31, it is determined whether a flag MODE indicating an operation mode is “1”.

If an affirmative determination is made in step 31, that is, if the mirror cycle operation is being performed, step 32 is executed.
To execute a mirror cycle control routine. Conversely, if a negative determination is made in step 31, that is, if the Otto cycle operation is being performed, the routine proceeds to step 33, where an Otto cycle control routine is executed. FIG. 4 shows the flag MO
This is a DE setting routine in which interrupt processing is performed at predetermined time intervals.

In step 41, the accelerator depression amount Ac detected by the accelerator opening sensor 22 is read, and in step 42, the accelerator depression amount ΔAc is calculated as the absolute difference between the currently read accelerator depression amount Ac and the previously read accelerator depression amount Acb. Calculate as a value. Step 43
And the accelerator depression amount ΔAc is set to a predetermined threshold value ΔA.
It is determined whether or not it is equal to or greater than co. If a negative determination is made, this routine is terminated without performing any processing.

If an affirmative determination is made in step 43, the routine proceeds to step 44, where it is determined whether the accelerator depression amount Ac read this time is greater than the accelerator depression amount Acb read last time. If an affirmative determination is made in step 44, the process proceeds to step 45, where a first switching routine is executed, and the process proceeds to step 47.

Conversely, if a negative determination is made in step 44, the routine proceeds to step 46, where a second switching routine is executed, and the routine proceeds to step 47. In step 47, the previously read accelerator depression amount Acb is replaced with the currently read accelerator depression amount Ac, and this routine ends. FIG. 5 shows the first
9 is a flowchart of a switching routine, in which control at the time of switching from the Miller cycle operation to the Otto cycle operation is executed.

In step 451, the closing timing θc of the intake control valve during the Miller cycle operation corresponding to the accelerator depression amount Acb before the accelerator pedal depression amount is increased is determined. Note that the closing timing of the intake control valve during the Miller cycle operation can be expressed as a function of the accelerator depression amount. In step 452, a difference Δθ between the intake valve closing timing θICV and θc is calculated.

Next, in step 453, Δθ is a predetermined value θlimi
It is determined whether it is greater than t, and if a negative determination is made, the process directly proceeds to step 457. If an affirmative determination is made in step 453, the routine proceeds to step 454, in which the intake control valve closing period θc
Is increased by a predetermined value α, and at step 455, the valve closing period θ
Output c. If the predetermined value α is a constant value, it is possible to change the operation mode while maintaining the rate of change constant.

Α = Δθ / N Here, if N is selected to be a predetermined number of cycles, it is possible to complete the switching of the operation mode after the predetermined cycle N.

Further, α = 60 · Δθ / (Ne · T) where Ne is the internal combustion engine speed (rpm) T is a predetermined time (second), and if the predetermined time (second) is selected, the operation mode switching is completed after the predetermined time T. It becomes possible.

In step 456, the closing period θ of the intake control valve
It is determined whether or not c is greater than the intake valve closing timing θICV. If a negative determination is made, the process returns to step 454. That is, when the amount of change in the depression of the accelerator pedal is larger than the predetermined value θlimit, the valve closing timing is delayed by the predetermined value α by a predetermined value α instead of immediately setting the valve closing timing during the Otto cycle operation, thereby preventing the occurrence of torque shock.

If an affirmative determination is made in step 456, the process proceeds to step 457, in which the flag MODE representing the operation mode is set to "0", and the Otto cycle operation is performed thereafter. FIG.
Is a flowchart of a second switching routine, which executes control at the time of switching from Otto cycle operation to Miller cycle operation. At step 461, the closing timing θm of the intake control valve during the Miller cycle operation corresponding to the accelerator depression amount Ac after the accelerator pedal depression amount is reduced is determined.

At step 462, the closing timing θIC of the intake valve
The difference Δθ between V and the current intake valve closing timing θc is calculated. Next, at step 463, it is determined whether or not Δθ is greater than a predetermined value θlimit. If a negative determination is made, the process directly proceeds to step 467. If an affirmative determination is made in step 463, the routine proceeds to step 464, in which the closing period θc of the intake control valve is decreased by α, and in step 465, the closing period θc is output.

At step 466, the closing period θ of the intake control valve
It is determined whether or not c is smaller than the closing timing θm of the intake valve during the Miller cycle operation.
Return to 64. That is, when the amount of change in the depression of the accelerator pedal is greater than the predetermined value θlimit, the valve closing timing is advanced by the predetermined value α instead of immediately setting the valve closing timing during the Miller cycle operation, thereby preventing the occurrence of torque shock.

If an affirmative determination is made in step 466, the process proceeds to step 467, in which the flag MODE indicating the operation mode is set to "1", and the mirror cycle operation is performed thereafter. FIG. 7 is a flowchart of a mirror cycle control routine executed in step 32 of the control routine, and is similar to step 3 in FIG.
In step 21, the accelerator pedal depression amount Ac is read. In step 322, the intake control valve opening φ is determined. In step 323, the intake control valve closing timing θc is determined as a function of the accelerator pedal depression amount Ac.

FIG. 8 is an example of a graph for determining the opening degree φ of the intake control valve and the closing timing θc of the intake control valve. The horizontal axis represents the accelerator pedal depression amount Ac, and the vertical axis represents the intake control valve. The opening degree φ and the closing timing θc of the intake control valve are determined. That is, if the accelerator pedal depression amount Ac is larger than a predetermined value Aco, the intake control valve opening φ is fully opened, the closing timing θc of the intake control valve becomes large in proportion to the accelerator pedal depression amount Ac, and the mirror cycle operation is started. It is possible to increase the intake air amount while continuing.

In step 324, the intake control valve opening φ is output, and in step 325, the intake control valve closing timing θc is output, and this routine is terminated. FIG. 9 is a flowchart of the Otto cycle control routine executed in step 33 of the control routine. In step 331, the accelerator pedal depression amount Ac is read, and in step 332, the intake control valve opening φ is proportional to the accelerator pedal depression amount Ac. And at step 323, the closing timing θc of the intake control valve
Is set to a fixed value θco which is greater than the intake valve closing timing θICV.

Then, at step 334, the intake control valve opening φ is output, and at step 335, the closing timing θc of the intake control valve is output, and this routine is terminated. FIG. 10 is an explanatory view of the operation of the present invention, in which the horizontal axis represents the rotation angle of the internal combustion engine, and the vertical axis represents the valve lift of the intake valve and the intake control valve. That is, the intake valve opens near the top dead center, reaches its maximum opening during the lowering of the piston, and closes near the bottom dead center.

During the Miller cycle operation, the intake control valve opens at a timing W1 before the intake valve opens, and closes at a timing W2 when the intake valve is opening. That is, the intake air corresponding to the area M surrounded by the valve lift curve a of the intake valve and the valve lift curve b of the intake control valve is supplied to the cylinder. In addition, since no throttle is present in the intake passage, no throttle loss occurs.

The amount of intake air during the Miller cycle operation is determined by determining the closing timing W2 of the intake control valve and the amount of depression A of the accelerator pedal.
It can be adjusted by controlling according to c. On the other hand, during the Otto cycle operation, in order to open the intake control valve longer than the period during which the intake valve is opened, the closing timing of the intake control valve is set to the closing timing of the intake valve, that is, the timing W0 later than the bottom dead center. And

Now, assuming that the accelerator pedal of the vehicle in the idling state is suddenly depressed, the internal combustion engine which has been operated in the Miller cycle is driven by an Otto in order to output a torque corresponding to the depression amount Ac of the accelerator pedal. It will be operated in a cycle. Therefore, it is necessary to change the valve closing timing of the intake control valve from W2 to W0. However, according to the intake control device of the present invention, it is not necessary to change the timing at once, but to sequentially change W2 → W3 → W4 → W0. Thus, the occurrence of torque shock due to the change in the operation mode is prevented.

When the depression of the accelerator pedal is suddenly released, the closing timing of the intake control valve is changed from W0 to W4 to W3 to W2, contrary to the above. In the above embodiment, the intake control valve is installed in the intake branch pipe between the intake throttle valve and the intake valve, but the intake control valve is a so-called variable valve system that changes the opening / closing timing of the intake valve itself. It is clear that the present invention can be applied to an omitted intake control device.

[0032]

According to the intake control system for an internal combustion engine according to the present invention, the change amount of the intake supply period per unit time at the time of switching between the first control means and the second control means is equal to or more than a predetermined value. In this case, the operation mode of the internal combustion engine can be smoothly switched by setting the intake supply period of the intake supply means to be transiently shorter than the intake supply period in the Miller cycle operation and longer than the intake supply period in the Otto cycle operation. And the occurrence of torque shock can be prevented.

[Brief description of the drawings]

FIG. 1 is a configuration diagram (1) of an embodiment.

FIG. 2 is a configuration diagram (2) of an embodiment.

FIG. 3 is a flowchart of a main control routine.

FIG. 4 is a flowchart of a flag setting routine.

FIG. 5 is a flowchart of a first switching routine.

FIG. 6 is a flowchart of a second switching routine.

FIG. 7 is a flowchart of a mirror cycle control routine.

FIG. 8 is a graph for determining an intake throttle valve opening degree and an intake control valve closing timing.

FIG. 9 is a flowchart of an Otto cycle control routine.

FIG. 10 is an explanatory diagram of an operation.

[Explanation of symbols]

 5 intake valve 6 intake port 8 intake branch 9 surge tank 13 step motor 14 intake throttle valve 16 intake control valve 17 fuel injection valve

Claims (1)

(57) [Claims] An intake throttle valve installed in an intake passage of an internal combustion engine for adjusting an amount of intake air supplied to the internal combustion engine by controlling an opening degree thereof, and an intake throttle valve downstream of the intake throttle valve. Intake timing control means for adjusting the amount of intake air supplied to the internal combustion engine by controlling an intake air supply period for communicating the combustion chamber with the intake passage; and opening the intake throttle valve so as not to cause a throttle loss. A first control means for controlling the intake air amount by controlling the intake air supply period of the intake timing control means in accordance with the operation state of the internal combustion engine, and opening the intake air amount in accordance with the operation state of the internal combustion engine. A second control means for adjusting the opening degree of the intake throttle valve by controlling the opening degree of the intake throttle valve. The control state of the first control means and the control of the second control means Status If the amount of change of the intake supply period per unit time at the time of switching is equal to or greater than a predetermined value, the intake supply period of the intake timing control unit is longer than the intake supply period controlled by the first control unit, and An intake control device for an internal combustion engine, comprising: a transient control means for controlling the intake supply period shorter than the intake supply period controlled by the second control means.