JP3089992B2 - Intake control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an intake control device for an internal combustion engine.

[0002]

2. Description of the Related Art There is known an internal combustion engine in which an intake flow control valve is disposed in an intake passage so as to close the intake flow control valve when the engine is started (for example, Japanese Patent Application Laid-Open No. 63-143349).
Reference). In this internal combustion engine, at the time of engine start, that is, for example, after the starter motor is started until the engine speed becomes higher than a predetermined set speed.
The intake air flow control valve is controlled to close to increase the airtightness of the intake passage,
As a result, a large negative pressure is formed in the intake passage downstream of the intake flow control valve, so that the fuel injected from the fuel injection valve is atomized as well as possible. When the injected fuel is finely atomized, a good combustion action is ensured, so that the amount of unburned HC discharged into the exhaust passage is reduced. Also, in this case, the intake air amount is reduced, and accordingly, the fuel injection amount is reduced. When the fuel injection amount itself decreases, the amount of unburned HC discharged into the exhaust passage also decreases.

[0003]

By the way, in the above-mentioned internal combustion engine, the opening degree of the intake air flow control valve at the time of engine start is maintained constant, and the intake air amount at the time of engine start is maintained at a predetermined target air amount. I am trying to be. This target air amount is an optimum air amount for reducing unburned HC at the time of engine start. However, if the engine speed at the time of engine startup, that is, the cranking speed fluctuates according to the temperature or the degree of deterioration of the engine oil, the battery voltage, or the like, the intake air amount is reduced even if the opening of the intake flow control valve is kept constant. Therefore, there is a problem that the amount of unburned HC discharged into the exhaust passage cannot be reduced, that is, the actual intake air amount deviates from the target air amount.

[0004]

According to a first aspect of the present invention, an intake flow control valve is disposed in an intake passage downstream of a throttle valve , and the intake flow control valve is closed when the engine is started. In an internal combustion engine that is controlled by a valve, an intake air amount at the time of engine start is obtained, and an intake air control valve is controlled based on the intake air amount so that the intake air amount becomes a predetermined target air amount at engine start. An intake flow control valve opening control means for controlling the opening is provided.

According to a second aspect of the present invention, an intake air flow control valve is arranged in an intake passage downstream of a throttle valve and downstream of a surge tank , and the intake air flow control valve is provided when the engine is started. A control valve is controlled to be closed, a bypass control valve is provided in a bypass passage that bypasses the intake flow control valve and connects the intake passage upstream of the intake flow control valve and the downstream intake passage with each other, and the bypass passage is provided. In an internal combustion engine that controls the amount of air supplied into the intake passage downstream of the intake flow control valve via the intake flow control valve, the amount of intake air at the time of engine start is obtained, and the amount of intake air at the time of engine start is determined based on the amount of intake air. There is provided a bypass control valve opening control means for controlling the opening of the bypass control valve so as to attain a predetermined target air amount.

According to a third aspect of the present invention, an intake flow control valve is disposed in an intake passage so as to close the intake flow control valve when the engine is started. The fuel injection valve is arranged in the downstream intake passage, and the air injection port of the bypass passage connecting the intake passage upstream of the intake flow control valve and the downstream intake passage bypassing the intake flow control valve is connected to the fuel of the fuel injection valve. An opening is formed around the injection port so that the air ejected from the air injection port of the bypass passage collides with the injection fuel injected from the fuel injection port of the fuel injection valve, and a bypass control valve is provided in the bypass passage and the bypass control valve is provided. In an internal combustion engine that controls the amount of air supplied into an intake passage downstream of an intake flow control valve, the amount of intake air at the time of engine start is determined, and the amount of intake air at the time of engine start is determined based on the amount of intake air. Opening degree control means for controlling the opening degree of the intake air flow control valve and the opening degree of the bypass control valve so as to reach a predetermined target air amount, the opening degree control means opening the bypass control valve The intake air amount is controlled by controlling the opening of the intake flow control valve while maintaining the state, and the intake air amount is controlled by controlling the opening of the bypass control valve when the intake flow control valve is closed doing.

Next, the operation of the above means will be described.
According to the first aspect, at the time of engine start, the opening of the intake air flow control valve is controlled to maintain the intake air amount at the target air amount. According to the second aspect, the opening degree of the bypass control valve is controlled when the engine is started, and the intake air amount is maintained at the target air amount.

According to the third aspect, at the time of engine start, the opening of the intake flow control valve and the opening of the bypass control valve are controlled, and the intake air amount is maintained at the target air amount. In this case, basically, while the bypass control valve is kept open, the opening degree of the intake flow control valve is controlled to control the amount of intake air. Therefore, even when the amount of intake air should be reduced, the amount of air ejected from the air injection port is secured, and the action of atomizing the injected fuel by this air is maintained. If the intake air amount is still larger than the target air amount even when the intake flow control valve is closed, the intake air amount is reduced by reducing the opening of the bypass control valve.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The internal combustion engine of FIG. 1 has, for example, four cylinders, but FIG. 1 shows only one cylinder.
Referring to FIG. 1, 1 is a cylinder block, 2 is a piston that reciprocates in the cylinder block 1, 3 is a cylinder head fixed on the cylinder block 1, and 4 is defined between the top surface of the piston 2 and the cylinder head 3. Combustion chamber, 5
Denotes intake valves arranged in intake ports 6 in the cylinder head 3. Each intake port 5 is connected to a common surge tank 8 via a corresponding intake branch pipe 7, and the surge tank 8 is connected to an air cleaner 10 via an intake duct 9. In each intake branch pipe 7, a fuel injection valve 11 for injecting fuel toward the corresponding intake port 6 is arranged. These fuel injection valves 11 are controlled based on output signals from the electronic control unit 40, respectively. Also, a throttle valve 12 whose opening degree increases as the depression amount of an accelerator pedal (not shown) increases in the intake duct 9. On the other hand, each exhaust port (not shown) is connected to a catalytic converter (not shown) via a common exhaust manifold (not shown).

As shown in FIG. 1, an intake flow control valve 14 driven by an intake flow control valve driving device 13 is arranged in the intake branch pipe 7 located upstream of each fuel injection valve 11. . Although the intake flow control valve driving device 13 may have any configuration, in this embodiment, it is composed of an electromagnetic actuator. The intake flow control valve driving device 13 drives the intake flow control valve 14 by moving a rod 15 connected to the intake flow control valve 14 in the direction of the arrow in FIG. That is, the intake flow control valve driving device 13
When the valve is to be opened, the rod 15 is moved downward in FIG. 1, and when the intake flow control valve 14 is to be closed, the rod 15 is moved upward. The intake flow control valve driving device 13 is controlled based on an output signal from the electronic control unit 40.

Still referring to FIG.
A bypass passage 16 branches off from the upstream intake duct 9, and the bypass passage 16 is connected via a three-way valve 17 to an air passage 18 communicating with the intake duct 9 downstream of the throttle valve 12 on the one hand, and to the intake flow It is connected to an assist air passage 19 communicating with the intake branch pipe 7 downstream of the control valve 14. The three-way valve 17 has a communication area between the bypass passage 16 and the air passage 18, that is, a first valve body 20 a for controlling an opening area A of the air passage 18, and a communication area between the bypass passage 16 and the assist air passage 19, that is, the assist air. Passage 19
And a second valve element 20b for controlling the opening area B of the rotary valve 20. A permanent magnet 21 is attached to an end of the valve shaft of the rotary valve 20, and electromagnetic coils 22 are arranged on both sides of the permanent magnet 21.

A pulse current is supplied to these electromagnetic coils 22, and a ratio of a pulse current generation time to a pulse current generation cycle, that is, a duty ratio of the pulse current is controlled. FIG. 2 shows the duty ratio DUTY of the pulse current,
Opening area A of air passage 18 and assist air passage 19
In relation to the opening area B of FIG. In FIG. 2, the broken line indicates the opening area B of the assist air passage 19, and the solid line indicates the sum of the opening area B of the assist air passage 19 and the opening area A of the air passage 18. Therefore,
2, when the duty ratio DUTY is smaller than DUTY1, only the opening area B of the assist air passage 19 increases as the duty ratio DUTY increases, and when the duty ratio DUTY becomes larger than DUTY1, the opening area B of the assist air passage 19 becomes constant. Air passage 18
It can be understood that the opening area A increases as the duty ratio DUTY increases.

Referring to FIG. 1 again, the air injection port 19 a of the assist air passage 19 is connected to the fuel injection port 11 of the fuel injection valve 11.
It is opened around a. As a result, the air ejected from the air injection port 19a collides with the fuel injected from the fuel injection port 11a, and the fuel can be atomized. After the start of the engine is completed, the opening area A of the air passage 18 and the opening area B of the assist air passage 19 are controlled such that the idling speed reaches a predetermined target speed. Further, in this embodiment, the assist air passage 19 constitutes a bypass passage, and the three-way valve 17, especially the second valve body 20b constitutes a bypass control valve.

Still referring to FIG. 1, the electronic control unit 40 comprises a digital computer and is connected to a ROM (read only memory) 42, a RAM (random access memory) 43,
It has a CPU (microprocessor) 44, an input port 45 and an output port 46. The input port 45 has a throttle opening sensor 38 for generating an output voltage proportional to the opening of the throttle valve 12, that is, the throttle opening TA.
Are connected via an AD converter 39. Further, a negative pressure sensor 47 for generating an output voltage proportional to the negative pressure in the surge tank 8 is connected to the input port 45 via an AD converter 48. The CPU 44 calculates the intake air amount after the completion of the engine start based on the output voltage. Therefore, FIG.
In the internal combustion engine, for example, it is not necessary to provide an air flow meter between the throttle valve 15 and the air cleaner 13, so that the engine pumping loss can be reduced. Further, by mounting the negative pressure sensor 47 on the surge tank 11,
, The influence of intake pulsation on the output of the negative pressure sensor 47 can be reduced. A temperature sensor 49 that generates an output voltage proportional to the engine cooling water temperature or the engine oil temperature is connected to the input port 45 via an AD converter 50. Furthermore, the input port 45
Is connected to a crank angle sensor 51 that generates an output pulse every time the crankshaft rotates, for example, 30 degrees.
The CPU 44 determines the engine speed N based on the output pulse.
Is calculated.

Further, an on / off signal of the starter motor switch 52 is input to the input port 45. Starter motor switch 52 and ignition switch 53
Constitutes a key switch 54, and the starter motor switch 52 only when the ignition switch 53 is turned on.
Is turned on. When the ignition switch 53 is turned on, the battery 55
Is supplied with power. On the other hand, the starter motor switch 5
2 is turned on, the starter motor 5
6 and the starter motor 56 is driven. On the other hand, the output port 46 is connected to each of the fuel injection valves 11, the intake flow control valve driving device 13, and the electromagnetic coil 22 via the corresponding driving circuits 57.

In this embodiment, when the engine is started, that is, after the starter motor switch 52 is turned on and the engine is started, the engine speed N is increased to a predetermined set speed N.
1, for example, the intake flow control valve 14 is controlled to be closed until it becomes higher than 400 rpm. As a result, the degree of sealing of the intake passage at the time of starting the engine can be increased, and the amount of intake air at the time of starting the engine can be reduced. When the intake air amount is reduced, the fuel injection amount is reduced accordingly, so that the amount of unburned HC discharged into the exhaust manifold at the time of starting the engine can be reduced. Further, by controlling the closing of the intake flow control valve 14, a large negative pressure can be formed in the intake branch pipe 7 and the intake port 6 downstream of the intake flow control valve 14. Therefore, the fuel injected from the fuel injection valve 11 can be finely atomized by the negative pressure. Further, the fuel adhered to the wall surfaces of the intake branch pipe 7 and the intake port 6 can be satisfactorily separated and atomized by the large negative pressure. As described above, when the injected fuel can be finely atomized, the fuel is removed from the combustion chamber 4.
Unburned HC discharged into the exhaust manifold when the engine is started.
Can be further reduced.

However, the smaller the amount of intake air at the time of starting the engine, the better. Intake air amount per unit engine speed Q / N at engine start
Referring to FIG. 3 showing the relationship between the amount of unburned HC and the amount of unburned HC discharged to the exhaust manifold, when Q / N is relatively large, the unburned HC decreases as Q / N decreases for the above-described reason.
The amount is reduced. However, when Q / N is smaller than the range OPT, the unburned HC amount increases as Q / N decreases. This is because when the Q / N is extremely small, the torque generated by the engine is small, so that the torque required to start the engine cannot be obtained. When the fuel injection amount is increased to compensate for this, the fuel becomes excessive. This is because the combustion action in the combustion chamber 4 becomes unstable. Therefore, it can be seen that the Q / N must be maintained within the optimum range OPT in order to keep the unburned HC amount small at the time of starting the engine. In other words, when starting the engine, Q
If / N is kept within the optimum range OPT, the unburned HC amount can be kept small.

If the opening of the intake flow control valve 14 is maintained at a slightly small opening or the opening area of the assist air passage 19 is maintained at an area larger than zero, the Q / N is maintained within the optimum range OPT. Even if the opening degree of the intake air flow control valve 14 or the opening area of the air passage 18 or the assist air passage 19 is kept constant irrespective of the engine operating state, it is possible to secure the amount of air for When the operating state, that is, for example, the engine speed or the throttle opening at the time of starting the engine is different, the Q / N changes accordingly. If Q / N changes and deviates from the optimum range OPT, the unburned HC amount can no longer be maintained at a small amount. Therefore, in this embodiment, the opening degree of the intake flow control valve 14 and the three-way valve 17, that is, the opening degree of the intake flow control valve 14, is determined so that Q / N at the time of engine start is determined so that Q / N is within the optimum range OPT. And the air passage 18
And the opening area of the assist air passage 19 is controlled. Therefore, in this embodiment, the optimal range OPT
The amount of air inside is the target air amount. Next, a method of controlling the intake flow control valve 14 and the three-way valve 17 at the time of starting the engine will be described.

In order to control Q / N at the time of starting the engine, the opening degree of the intake flow control valve 14 and the opening degree of the three-way valve 17, that is, the opening area A of the air passage 18 and the opening area B of the assist air passage 19 are determined. May be controlled as follows. However, as described above, it is preferable that the injected fuel be atomized as much as possible, especially at the time of starting the engine. Therefore, in the internal combustion engine of FIG. 1, the opening area B of the assist air passage 19 is maintained at the maximum area and the opening area A of the air passage 18 is maintained in principle.
Is maintained at zero, the opening degree T of the intake flow control valve 14 is
Q / N is controlled by controlling HETA. That is, when the engine is started, the duty ratio DU for driving the three-way valve 17 can be seen from FIG.
While maintaining TY at DUTY1, the opening THETA of the intake flow control valve 14 is controlled. When the opening area of the assist air passage 19 is maintained at the maximum area, the air jet 1
Since air is always supplied from the nozzle 9a, the effect of atomizing the injected fuel by the air can be secured.
Moreover, in this embodiment, since the opening area of the assist air passage 19 is set to the maximum area, the amount of air supplied from the air injection port 19a is maximized, and the maximum fuel atomization action is ensured. On the other hand, by keeping the opening area A of the air passage 18 at zero when the engine is started, Q / N is reduced as much as possible.

On the other hand, for obtaining the Q / N, for example, a negative pressure sensor for detecting a negative pressure in the intake branch pipe 7 downstream of the intake flow control valve 14 is provided, and the actual value is determined based on the negative pressure detected by the negative pressure sensor. Or an air amount sensor for detecting the intake air amount may be provided to detect the actual Q / N, but this is not practical. However, the intake air amount is determined according to the engine operating state. Therefore, in the internal combustion engine of FIG. 1, an intake air amount or Q / N determined according to the engine operating state is obtained in advance, and the engine operating state is detected at the time of starting the engine, and the Q / N in the engine operating state is within the optimum range OPT. The opening degree of the intake flow control valve 14 is changed as shown in FIG.

More specifically, in the internal combustion engine shown in FIG. 1, a reference engine operating state is predetermined, and the intake air amount Q per unit engine speed in the reference engine operating state is determined.
The opening degree of the intake air flow control valve 14 for maintaining / N in the optimum range OPT is obtained in advance as the reference opening THETAS. Further, when the engine operating state changes from the reference engine operating state, Q in the engine operating state is changed. / N is the optimal range OPT
The amount of correction of the opening degree of the intake flow control valve 14 required to be maintained in advance is determined in advance, the engine operation state at the time of engine start is detected, and the intake flow control is performed by the correction amount corresponding to the engine operation state. The Q / N is maintained within the optimum range OPT by correcting the opening of the valve 14 from the reference opening THETAS.

In this embodiment, the engine operating state is determined by the engine speed at the time of engine start, that is, the cranking speed N and the throttle opening TA. Although the reference engine operating state may be any engine operating state, in this embodiment, the cranking rotational speed N is the maximum cranking rotational speed NMAX that can be obtained when the engine is started, and the throttle opening T
The state where A is zero is defined as the reference engine operating state. For a given THETA, Q / N decreases as cranking speed N increases, while Q / N decreases as throttle opening TA decreases. If the amount of air supplied from the assist air passage 19 is not considered, Q / N becomes minimum. Therefore, if the Q / N in the reference engine operating state is referred to as the reference Q / N, the Q / N when the engine operating state changes from the reference engine operating state will always be greater than the reference Q / N. As a result, in this embodiment, the intake flow control valve opening correction coefficient KT is set to zero or less.

The intake flow control valve driving device 13 controls the actual opening of the intake flow control valve 14 to be equal to the target opening THETA, but the target opening THETA of the intake flow control valve 14 when the engine is started is determined by the following formula. It is calculated based on the formula. THETA = THETAS + KT As described above, Q / N decreases as cranking speed N increases, and Q / N decreases as throttle opening TA decreases. Therefore, as shown in FIG. 4A, the intake flow control valve opening correction coefficient KT is zero when the cranking rotational speed N is NMAX and the cranking rotational speed N is constant for a constant throttle opening TA. As shown in FIG. 4B, it becomes smaller when the throttle opening degree TA is zero, and becomes smaller as the throttle opening degree TA becomes larger for a given cranking speed N. This KT is stored in advance in the ROM 42 in the form of a map shown in FIG. In this specification, the opening of the intake flow control valve 14 is referred to as THETA
As long as the opening is kept small near S, the intake flow control valve 1
It is assumed that valve closing control is performed on the valve No. 4.

However, when the cranking rotational speed N decreases and becomes equal to or less than NCL, or when the throttle opening TA increases and becomes equal to or greater than TCL, the intake flow control valve opening correction coefficient KT becomes smaller than -THETAS. KT <
−THETAS, the target opening T of the intake flow control valve 14
HETA becomes smaller than zero, and in this case, the intake flow control valve 14 is maintained in the fully closed state. As a result, N <
In the case of NCL or TA> TACL, Q / N cannot be further reduced even though Q / N should be further reduced. Therefore, if N <NCL or TA> TCL
In this case, the opening area B of the assist air passage 19, that is, the duty ratio DUTY, that is, the duty ratio DUTY is made smaller than DUTY1 while keeping the intake flow control valve 14 fully closed.
/ N, thereby keeping Q / N within the optimal range OPT.

That is, in the internal combustion engine shown in FIG.
As shown in the figure, when the cranking speed N is larger than NCL, the cranking speed N is maintained at zero. When the cranking speed N is smaller than NCL, the cranking speed N becomes smaller as the cranking speed N becomes smaller for a certain throttle opening. As shown in FIG. 5B, when the throttle opening TA is smaller than TCL, the throttle opening TA is maintained at zero. When the throttle opening TA is larger than TCL, the throttle opening TA is constant with respect to a constant cranking speed N. A duty ratio correction coefficient KD, which becomes smaller as it becomes larger, is introduced.
UTY is calculated.

DUTY = DUTY1 + KD This KD is stored in advance in the form of a map shown in FIG.
It is stored in M42. At the time of engine start, N>
When N1 is reached and the start of the engine is completed, the intake flow control valve 14 is opened. As a result, the shortage of the intake air after the completion of the engine start is prevented, so that the shortage of the output torque is prevented. After the start of the engine is completed, the intake flow control valve 14 is selectively controlled to either the maximum opening MAX or the intermediate opening MID between the valve closing state and the maximum opening MAX according to the engine operating state. . That is, for example, at the time of low load operation in which the engine load is lower than the set load determined according to the engine speed N, the intake flow control valve 14 is set to the middle opening degree MID, for example, half open, and during the high load operation in which the engine load is higher than the set load The intake flow control valve 14 is set to the maximum opening degree MAX, that is, fully opened. When the intake flow control valve 14 is set at the middle opening degree MID, almost all of the intake air flows through a gap formed between the top end of the intake flow control valve 14 and the inner wall surface of the intake branch pipe 10, and then the fuel injection valve The fuel flows toward the injected fuel injected from 11 and collides with the injected fuel. Therefore, by setting the intake flow control valve 14 to the intermediate opening degree MID, the injected fuel can be satisfactorily atomized by the air flowing through the intake flow control valve 14. On the other hand, at the time of high load operation, a larger amount of intake air can be secured by setting the intake flow control valve 14 to the maximum opening degree MAX.

Next, a routine for executing the above-described method of controlling the intake flow control valve 14 will be described with reference to FIG.
This routine is executed by interruption every predetermined time after the ignition switch 53 is turned on. Referring to FIG. 6, first, in step 60, it is determined whether or not F1 is 1. This F1 is set to zero when the engine start is not completed, and is set to 1 when the engine start is completed, and is set to zero when the ignition switch 53 is turned on. When the process proceeds to step 60 for the first time after the ignition switch 53 is turned on, F1 = 0, and then the process proceeds to step 61. In step 61, it is determined whether or not the cranking rotation speed N is higher than the set rotation speed N1, that is, whether or not the engine start has been completed. If the starter motor switch 52 is still off and the engine has not been started, or if N ≦ N1 after the start of the engine, it is determined that the engine has not been started, and the routine proceeds to step 62. In step 62, the intake flow control valve opening correction coefficient KT is calculated from the map shown in FIG. In the following step 63, the target opening THETA of the intake flow control valve 14 is calculated based on the following equation.

The intake flow control valve driving device 13 controls the intake flow control valve 1 so that the actual opening of the intake flow control valve 14 becomes the target opening THETA.
4 is driven. In the following step 64, the duty ratio correction coefficient KD is calculated from the map shown in FIG. 5, and in the following step 65, the duty ratio DUTY is calculated based on the following equation.

DUTY = DUTY1 + KD A pulse current having a duty ratio DUTY is supplied to the electromagnetic coil 22. Next, the processing cycle ends. On the other hand, when N> N1 in step 61, the process proceeds to step 66, where it is determined that the engine start has been completed, and F1 is set to 1. Next, the routine proceeds to step 67, where the target opening THETA of the intake flow control valve 14 is set to the intermediate opening MID. Next, after proceeding to step 70, the processing cycle ends.

In the processing cycle after F1 = 1, the process proceeds from step 60 to step 68. In step 68, it is determined whether or not the engine is in the high load operation. At the time of engine low load operation, the routine proceeds to step 67, where the intake flow control valve 1
The target opening THETA of No. 4 is set to the intermediate opening MID. Next, the routine proceeds to step 70. On the other hand, at the time of engine high load operation, the routine proceeds to step 69, where the target opening THETA of the intake flow control valve 14 is set to the maximum opening MAX. Next, the routine proceeds to step 70. In step 70, the duty ratio DUTY required to make the amount of air supplied from the assist air passage 19 and the air passage 18 the optimum amount of air is calculated. Next, the processing cycle ends.

In the above-described embodiment, the engine operating state at the time of starting the engine is determined by the cranking speed N and the throttle opening TA. However, since the cranking speed N is determined according to the engine cooling water temperature THW, the cranking speed N is higher when the engine cooling water temperature THW is higher than when the engine cooling water temperature THW is lower. May be determined by the engine cooling water temperature THW and the throttle opening TA. In this case, even if the engine start is not started, that is, the ignition switch 53
Since the engine cooling water temperature THW can be detected even after the starter motor switch 52 is turned on after the switch is turned on, the intake air amount when the engine is started is estimated based on the THW. be able to. Therefore, prior to the start of the engine, the intake air flow control valve 1
4 can be controlled to an opening required to maintain the Q / N at the time of starting the engine within the optimum range OPT, so that the Q / N is surely adjusted to the optimum range when the engine starts. OP
T can be maintained.

In the above-described embodiment, the air passage 18 and the assist air passage 1
By controlling the opening degree of the intake flow control valve 14 while maintaining the opening area of the nozzle 9 constant, the intake air amount is controlled. However, for example, the opening area of the assist air passage 19 is controlled while maintaining the opening degree of the intake flow control valve 14 and the opening area of the air passage 18 constant, or the opening degree of the intake flow control valve 14 and the air passage 18 and The intake air amount may be controlled by simultaneously controlling the opening area of the assist air passage 19 and the opening area.

[0033]

According to the first aspect, the amount of unburned HC discharged into the exhaust passage at the time of starting the engine can be reduced. According to the second aspect, the amount of unburned HC discharged into the exhaust passage at the time of starting the engine can be reduced.

According to the third aspect of the invention, it is possible to reduce the amount of unburned HC discharged into the exhaust passage while ensuring the effect of atomizing the injected fuel by the air from the air injection port when the engine is started.

[Brief description of the drawings]

FIG. 1 is an overall view of an internal combustion engine.

FIG. 2 is a diagram showing opening areas of an air passage and an assist air passage.

FIG. 3 is a diagram showing a relationship between Q / N and an unburned HC amount.

FIG. 4 is a diagram showing an intake flow control valve opening correction coefficient;

FIG. 5 is a diagram showing a duty ratio correction coefficient.

FIG. 6 is a flowchart for executing opening degree control of an intake flow control valve and a three-way valve.

[Explanation of symbols]

 7 intake branch pipe 11 fuel injection valve 12 throttle valve 14 intake flow control valve 17 three-way valve 19 assist air passage

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02M 69/00 F02M 69/00 310E 310 69/04 G 69/04 F02N 17/00 B F02N 17/00 F02M 69/00 350W ( 56) References JP-A-63-143349 (JP, A) JP-A-6-229353 (JP, A) JP-A-2-291454 (JP, A) JP-A-59-136526 (JP, A) Hei 5-125974 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/00-41/40 F02D 9/02 F02D 13/02

Claims (3)

(57) [Claims] In an internal combustion engine in which an intake flow control valve is disposed in an intake passage downstream of a throttle valve to control closing of the intake flow control valve when the engine is started, an intake air amount at the time of engine start is determined. And an intake flow control valve opening control means for controlling the opening of the intake flow control valve so that the intake air amount becomes a predetermined target air amount at the time of engine start based on the intake air amount. . 2. A throttle valve downstream and below a surge tank.
The intake air flow control valve is disposed in the flow intake air passage so that the intake air flow control valve is closed when the engine is started, and the intake air flow control valve is bypassed and the intake air flow passage upstream of the intake air flow control valve and the downstream intake air are bypassed. In an internal combustion engine in which a bypass control valve is provided in a bypass passage connecting the passages to each other to control the amount of air supplied to the intake passage downstream of the intake flow control valve via the bypass passage, at the time of engine start-up, A bypass control valve opening control means for obtaining an intake air amount and controlling an opening degree of the bypass control valve so that the intake air amount becomes a predetermined target air amount at the time of engine start based on the intake air amount; Intake control device. 3. An intake flow control valve is disposed in an intake passage so as to close and control the intake flow control valve when the engine is started. A fuel injection valve is disposed in an intake passage downstream of the intake flow control valve. An air outlet of the bypass passage connecting the intake passage upstream of the intake flow control valve and the downstream intake passage bypassing the intake flow control valve is opened around the fuel injection hole of the fuel injection valve, and is ejected from the air injection hole of the bypass passage. The injected air is caused to collide with the injected fuel injected from the fuel injection port of the fuel injection valve, a bypass control valve is provided in the bypass passage, and the air is supplied into the intake passage downstream of the intake flow control valve via the bypass passage. In an internal combustion engine in which the amount of air is controlled, the amount of intake air at the time of engine start is determined, and the intake air flow is controlled based on the amount of intake air so that the amount of intake air at the time of engine start is a predetermined target air amount. Opening control means for controlling the opening of the control valve and the opening of the bypass control valve, and the opening control means controls the opening of the intake flow control valve while maintaining the bypass control valve in the open state; An intake control device that controls an intake air amount by controlling the intake air amount, and controls an opening degree of a bypass control valve when the intake air flow control valve is closed.