JPH0914095A - Assist air controller of internal combustion engine - Google Patents

Abstract

PURPOSE: To decrease the discharging amount of unburnt HC by stopping supply of assist air from an assist air supplying port until fuel infection is started from a fuel injection valve in cranking of an internal combustion engine, and starting supply of assist air when fuel injection is started. CONSTITUTION: In cranking of an engine, supply of assist air from a supplying port 8 for assist air is stopped until fuel injection is started from a fuel injection valve 7, and supply of air from a bypass air supplying port 14a is also stopped. When the fuel injection valve 7 starts fuel injection, the assist air supplying port 8 starts supply of assist air, and the bypass air supplying port 14a starts supply of air. Therefore, fuel having the amount proportional to the intake air amount is injected by the fuel injection valve 7, and the amount of injection fuel can be decreased. Since assist air to be supplied from the assist air supplying port 8 promotes atomization of injection fuel, the discharge of unburnt HC is drastically decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assist air control system for an internal combustion engine.

[0002]

2. Description of the Related Art A throttle valve is arranged in an engine intake passage, an intake flow control valve is arranged in an engine intake passage downstream of a throttle valve, and a fuel injection valve is arranged in an engine intake passage downstream of this intake flow control valve. In addition, an assist air supply port for ejecting air toward the fuel injected from the fuel injection valve into the intake passage is arranged on the side of the nozzle port of the fuel injection valve, and the assist air supply port is assisted. There is known an internal combustion engine connected to an engine intake passage upstream of a throttle valve via an air supply control valve (see Japanese Patent Laid-Open No. 6-229353).

In this internal combustion engine, at the time of engine cranking, the intake flow control valve is fully closed and the assist air supply control valve is fully opened. That is, in this internal combustion engine, the intake flow control valve is fully closed during engine cranking to generate a large negative pressure in the intake passage downstream of the intake flow control valve, and the assist air supply control valve is fully opened to assist air flow. Supply a large amount of air from the supply port,
As a result, the fuel injection is satisfactorily atomized.

[0004]

By the way, most of unburned HC discharged from the engine during engine operation from when the engine is started to when the engine is stopped is discharged when the engine is started. In order to reduce the emission amount of unburned HC during operation, it is necessary to reduce the emission amount of unburned HC when the engine is started. In this case, the amount of unburned HC discharged at the time of engine startup is mainly proportional to the amount of fuel supplied at the time of engine cranking, and the amount of fuel supplied at the time of engine cranking is supplied to the engine cylinder during engine cranking. It is proportional to the amount of intake air. Therefore, if the intake air amount supplied to the engine cylinder during engine cranking can be reduced, the fuel supply amount can be reduced accordingly, and thus the emission amount of unburned HC can be reduced. Become.

By the way, when the intake flow control valve is closed at the time of engine cranking as in the above-mentioned internal combustion engine, the amount of intake air supplied into the engine cylinder is reduced, and thus the amount of unburned HC discharged is reduced. It can be reduced. However, in the above-mentioned internal combustion engine, since the assist air supply control valve is held in the fully open state during the engine cranking, the intake air amount supplied to the engine cylinder is still large, and therefore the unburned HC emission amount is large. Is not sufficiently reduced.

[0006]

According to the first aspect of the invention, in order to solve the above problems, a throttle valve is arranged in the engine intake passage, and a fuel injection valve is arranged in the engine intake passage downstream of the throttle valve. In an internal combustion engine in which an assist air supply port for ejecting air toward the fuel injected into the intake passage from the fuel injection valve is arranged on the side of the nozzle port of the fuel injection valve, fuel is injected during engine cranking. Assist air supply that stops the supply of assist air from the assist air supply port until fuel injection from the injection valve is started, and starts supply of assist air from the assist air supply port when fuel injection is started It has a control means.

In the second invention, in the first invention,
An intake flow control valve is installed in the engine intake passage between the throttle valve and the fuel injection valve, which is kept closed during engine cranking and is opened when the engine speed exceeds a predetermined speed. ing. In the third invention, in order to solve the above-mentioned problems, a throttle valve is arranged in the engine intake passage, a fuel injection valve is arranged in the engine intake passage downstream of the throttle valve, and a lateral side of the nozzle port of the fuel injection valve is arranged. In an internal combustion engine in which an assist air supply port for ejecting air toward the fuel injected from the fuel injection valve into the intake passage is arranged, the engine intake air upstream of the assist air supply port and downstream of the throttle valve Equipped with an air supply port for supplying air into the passage, stopping the supply of assist air from the assist air supply port and the supply of air from the air supply port until fuel injection is started during engine cranking. Then, when fuel injection is started, the supply of assist air from the assist air supply port is started and the supply of air from the air supply port is stopped or It is provided with a supply control means for supplying a small amount of air than the assist air from the supply port.

[0008]

In the first aspect of the invention, the intake air supplied to the engine cylinder is stopped because the supply of the assist air from the assist air supply port is stopped until the fuel injection from the fuel injection valve is started during engine cranking. When the amount decreases and fuel injection is started, assist air is supplied from the assist air supply port, so that the injected fuel is atomized.

In the second aspect of the present invention, during engine cranking, the intake flow control valve is held in the closed position until the engine speed exceeds a predetermined speed. In the third aspect of the invention, during engine cranking, the supply of assist air from the assist air supply port and the supply of air from the air supply port are stopped until fuel injection from the fuel injection valve is started. When the amount of intake air supplied to the engine is reduced and fuel injection is started, assist air is supplied from the assist air supply port, so that the injected fuel is atomized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, 1 is an engine body, 2 is a piston, 3 is an intake valve, and 4 is an intake port. The intake port 4 of each cylinder is connected to a surge tank 6 via a corresponding intake branch pipe 5, and a fuel injection valve 7 for injecting fuel into the corresponding intake port 4 is attached to each intake branch pipe 5. To be An assist air supply port 8 is arranged beside the nozzle port of the fuel injection valve 7, and atomization of the fuel is promoted by the assist air ejected from the assist air supply port 8 toward the injected fuel. An intake flow control valve 9 is arranged in the intake branch pipe 5 upstream of the nozzle port of the fuel injection valve 7 and the assist air supply port 8. On the other hand, the surge tank 6 is connected to an air cleaner (not shown) via an intake duct 10, and a throttle valve 11 is arranged in the intake duct 10.

A bypass passage 12 is branched from the intake duct 10 upstream of the throttle valve 11.
2 is connected via the idling speed control valve 13 to the bypass passage 14 on the one hand and to the assist air passage 15 which communicates with the assist air supply port 8 on the other hand. As shown in FIG. 1, the bypass passage 14 has a bypass air supply port 14a that opens into the intake duct 10 downstream of the throttle valve 11.
Linked to The idling speed control valve 13 controls the area of communication between the bypass passage 12 and the assist air passage 15, that is, the opening area A of the assist air passage 15
6a and a rotary valve 16 including a second valve body 16b for controlling an area of communication between the bypass passage 12 and the bypass passage 14, that is, an opening area S of the bypass passage 14. A permanent magnet 17 is attached to the end of the valve shaft of the rotary valve 16, and electromagnetic coils 18 are arranged on both sides of the permanent magnet 17.

A pulse current is supplied to these electromagnetic coils 18, and the ratio of the pulse current generation time to the pulse current generation period, that is, the duty ratio of the pulse current is controlled. FIG. 2 shows the duty ratio DUTY of the pulse current,
The relationship between the opening area A of the assist air passage 15 and the opening area S of the bypass passage 14 is shown. In FIG. 2, the broken line indicates the opening area A of the assist air passage 15, and the solid line indicates the sum of the opening area A of the assist air passage 15 and the opening area S of the bypass passage 14. Therefore, from FIG. 2, when the duty ratio DUTY is smaller than DUTYO, only the opening area A of the assist air passage 15 increases with the increase of the duty ratio DUTY, and when the duty ratio DUTY becomes larger than DUTYO, the opening area A of the assist air passage 15 becomes constant. It can be seen that the opening area S of the bypass passage 14 is maintained and increases as the duty ratio DUTY increases.

As shown in FIG. 1, the tip of an arm 19 attached to the valve shaft of the intake flow control valve 9 is connected to a negative pressure diaphragm type drive device 21 via a rod 20. The negative pressure diaphragm type drive device 21 includes a pair of diaphragms 23 and 24 connected to each other via a rod 22. The negative pressure chamber 25 of the diaphragm 23 is connected to the intake branch pipe 5 through a switching valve 26 that can communicate with the atmosphere and a check valve 27 that can flow only to the inside of the intake branch pipe 5, and the negative pressure of the diaphragm 24 is reduced. The chamber 28 has a switching valve 2 capable of communicating with the atmosphere.
It is connected to the negative pressure tank 30 via 9. Negative pressure tank 3
0 is a check valve 3 that can flow only into the intake duct 10.
1 is connected to the inside of the intake duct 10, so that the inside of the negative pressure tank 30 is maintained at the maximum negative pressure generated in the intake duct 10 downstream of the throttle valve 11.

The respective negative pressure chambers 2 are controlled by the respective switching valves 26 and 29.
When 5, 28 are open to the atmosphere, the intake flow control valve 9 is closed as shown in FIG. In the embodiment shown in FIG. 1, at this time, a slight air flow gap is formed in the peripheral portion of the intake flow control valve 9, so that even if the intake flow control valve 9 is closed, the intake flow control valve 9 is closed. There is some intake air flowing around the. When the negative pressure chamber 25 is connected to the intake branch pipe 5 by the switching action of the switching valve 26, a negative pressure is generated in the negative pressure chamber 25. At this time, the rod 20 pulls the rod 20 downward, and at this time, the intake flow control valve 9
Is half open. On the other hand, when the negative pressure chamber 25 is connected to the negative pressure tank 30 by the switching action of the switching valve 29, the rod 20 is pulled further downward, and at this time, the intake flow control valve 9 is fully opened.

The electronic control unit 40 comprises a digital computer, and a ROM (read only memory) 42, a RAM (random access memory) 43, a CPU (microprocessor) 44, an input port 45 which are mutually connected by a bidirectional bus 41. And an output port 46. A temperature sensor 47 for detecting the engine cooling water temperature is connected to the input port 45 via an AD converter 48, and a rotation speed sensor 49 for detecting the engine speed is connected to the input port 45. . Although not shown in the figure, an air flow meter for detecting the intake air amount or a pressure sensor for detecting the absolute pressure in the surge tank 6 is connected to the input port 45. On the other hand, the output port 46 is connected to the electromagnetic coil 1 via the corresponding drive circuit 50.
8 and switching valves 26 and 29.

FIG. 3 shows control of the duty ratio DUTY and the like at the time of starting the engine. Referring to FIG. 3, when the ignition switch is turned on, the duty ratio DUTY of the pulse current supplied to the electromagnetic coil 18 is set to zero. Therefore, at this time, the supply of the assist air from the assist air supply port 8 is stopped, and the bypass air supply port 1
The supply of air from 4a is stopped. At this time, the negative pressure chambers 25 and 28 of the negative pressure diaphragm device 21 are open to the atmosphere, so that the intake flow control valve 9 is closed.

Next, cranking is started. At this time as well, the duty ratio DUTY is set to zero and the intake flow control valve 9 is held in the closed state. Therefore, when the cranking is started, the supply of the assist air from the assist air supply port 8 is stopped, and the bypass air supply port 8
The supply of air from is also stopped. Further, at this time, the inflow of intake air from the intake branch pipe 5 is suppressed by the intake flow control valve 9. Therefore, if the intake valve 3 of any cylinder is opened at this time, the intake port 4 of that cylinder enters the intake port 4. A large negative pressure is generated. As a result, the amount of intake air supplied into the engine cylinder becomes small. Further, at this time, a negative pressure is also generated in the intake ports 4 of other cylinders due to the influence of the large negative pressure generated in the intake ports 4 due to the opening of the intake valves 3.

On the other hand, when cranking is started, fuel injection from the fuel injection valve 7 is started. This fuel injection is usually performed before the intake valve 3 of the corresponding cylinder opens.
As shown in FIG. 3, when the injection signal is given to the cylinder to be first injected (the fourth cylinder 4 in the case of FIG. 3) and fuel injection from the first cylinder to be injected is started, the duty ratio is changed. DUTY is set to the target duty ratio DOP, and thus supply of assist air from the assist air supply port 8 and supply of air from the bypass air supply port 14a are started. It should be noted that the target duty ratio DOP is a duty ratio DUT capable of maintaining the engine speed at the lower limit speed at which good combustion can be obtained after the engine is started, that is, the target speed.
The target duty ratio DOP is Y and is stored in advance in the ROM 42 in the form of a function of the engine cooling water temperature, for example.

When the fuel injection is started in this way, assist air is supplied from the assist air supply port 8, so that the assist air promotes atomization of the injected fuel.
On the other hand, as described above, the supply of the assist air from the assist air supply port 8 and the supply of the air from the bypass air supply port 14a are stopped until the fuel injection is started. Therefore, the fuel is supplied into each engine cylinder. The amount of intake air is small. At this time, the amount of fuel corresponding to this small amount of intake air is injected from each fuel injection valve 7 into each cylinder, so the amount of injected fuel is extremely small. In this way, the amount of injected fuel can be made small, and since the assist air supplied from the assist air supply port 8 promotes atomization of the injected fuel, the amount of unburned HC discharged can be greatly reduced. become.

Next, when the engine speed N exceeds a predetermined speed No, for example, 400 rpm, the intake flow control valve 9
Is sent to the negative pressure diaphragm type drive device 21 to connect the negative pressure chamber 25 to the intake branch pipe 5.
Switching action is performed. As a result, the intake flow control valve 9 is opened halfway. After the engine is started, the switching valve 29 is controlled according to the intake air amount, and the intake flow control valve 9 is fully opened when the intake air amount is large, and the intake flow control valve 9 is maintained in the half-open state when the intake air amount is small. It When the intake flow control valve 9 is in the half-opened state, the intake air is guided by the intake flow control valve 9 to flow at a high speed along the upper inner wall surface of the intake branch pipe 5, thereby promoting atomization of the injected fuel. It

FIG. 4 shows an engine start control routine, which is repeatedly executed. Referring to FIG. 4, first, at step 100, the injection amount is calculated. Next, at step 101, it is judged if it is the injection timing. When it is not the injection timing, the routine jumps to step 103. On the other hand, when it is the injection timing, the routine proceeds to step 102, where an injection signal is generated, and then the routine proceeds to step 103. When the injection signal is generated, the fuel injection is started from the fuel injection valve 7 of the corresponding cylinder.

In step 103, the engine speed N is 400.
It is determined whether it has become higher than rpm. N ≦ 40
When it is 0 rpm, the routine proceeds to step 104, where it is judged if the injection signal is generated. When the injection signal is not yet generated, the routine proceeds to step 105, where the duty ratio DUTY is made zero. On the other hand, when the injection signal is generated, the routine proceeds from step 104 to step 106, the target duty ratio DOP is calculated, and then in step 107, the target duty ratio DOP is made the duty ratio DUTY. On the other hand, N>
When it reaches 400 rpm, step 103 to step 10
Proceed to 6.

FIG. 5 shows another embodiment. In this embodiment, the duty ratio DUTY is set to zero until the fuel injection of the cylinder to be fuel-injected first is started, and when the first injection is started, the duty ratio DUTY is set to the start-time duty ratio DOPS. Next, when the engine speed N reaches a predetermined speed No., for example 400 rpm, the duty ratio DUTY is set to the target duty ratio DOP. At the same time, the intake flow control valve 9 is changed from the closed state to the half-opened state. Here, the starting duty ratio DOPS
Is DUTYO shown in FIG. 2 or a value close thereto. This duty ratio DUTYO is a state in which the amount of assist air supplied from the assist air supply port 8 is the maximum and the supply of air from the air supply port 14a is stopped. Therefore, in this embodiment, when the first fuel injection is started, the assist air is supplied from the assist air supply port 8 and the air supply is stopped from the air supply port 14a, or the assist air is supplied from the air supply port 14a. A smaller amount of air will be supplied.

In this way, when the fuel injection is started, the duty ratio DUTY is set to the starting duty ratio DOPS.
In this case, the amount of intake air supplied into each engine cylinder during cranking can be further reduced, so that the fuel injection amount can be further reduced, thus further reducing the emission amount of unburned HC. You will be able to FIG. 6 shows an engine start control routine, and this routine is repeatedly executed.

Referring to FIG. 6, first step 20
At 0, the injection amount is calculated. Then step 201
Then, it is determined whether or not it is the injection timing. When it is not the injection timing, the routine jumps to step 203. On the other hand, when it is the injection timing, the routine proceeds to step 202, where an injection signal is generated and then the routine proceeds to step 203.
When the injection signal is generated, fuel injection is started from the fuel injection valve 7 of the corresponding cylinder.

In step 203, the engine speed N is 400.
It is determined whether it has become higher than rpm. N ≦ 40
When it is 0 rpm, the routine proceeds to step 204, where it is judged if the injection signal is generated. When the injection signal is not yet generated, the routine proceeds to step 205, where the duty ratio DUTY is made zero. On the other hand, when the injection signal is generated, the routine proceeds from step 204 to step 206, the starting duty ratio DOPS is calculated, and then in step 207, the starting duty ratio DOPS is made the duty ratio DUTY. On the other hand, when N> 400 rpm, the routine proceeds from step 203 to step 208, where the target duty ratio DOP is calculated. Next, at step 209, the target duty ratio D
OP is set to the duty ratio DUTY.

FIG. 7 shows still another embodiment. In this embodiment, the intake flow control valve 9 shown in FIG. 1 is not provided. Further, in this embodiment, a pressure sensor 33 for detecting the absolute pressure PM in the surge tank 6 is attached to the surge tank 6. In this embodiment, in order to reduce the fuel injection amount at the time of starting the engine, at the time of cranking, the fuel injection is started after the absolute pressure PM in the surge tank 6 becomes equal to or lower than a predetermined set pressure PMo. . Further, in this embodiment, as shown in FIG. 8, the duty ratio DUTY is set to zero until the first fuel injection is performed, and when the first fuel injection is performed, the duty ratio DUTY is set to the target duty ratio DOP.

FIG. 9 shows an engine start control routine, and this routine is repeatedly executed. Referring to FIG. 9, first, at step 300, the injection amount is calculated. Next, at step 301, it is judged if the absolute pressure PM in the surge tank 6 has become lower than a preset set value PMo. When PM ≧ PMo, the routine jumps to step 304. On the other hand, when PM <PMo, the routine proceeds to step 302, where it is judged if it is the injection timing. When it is not the injection timing, the routine jumps to step 304. On the other hand, when it is the injection timing, the routine proceeds to step 303, where an injection signal is generated and then the routine proceeds to step 304. When the injection signal is generated, the fuel injection is started from the fuel injection valve 7 of the corresponding cylinder.

In step 304, the engine speed N is 400.
It is determined whether it has become higher than rpm. N ≦ 40
When it is 0 rpm, the routine proceeds to step 305, where it is judged if the injection signal is generated or not. When the injection signal has not yet been generated, the routine proceeds to step 306, where the duty ratio DUTY is made zero. On the other hand, when the injection signal is generated, the routine proceeds from step 305 to step 307 to calculate the target duty ratio, and then in step 308 the target duty ratio DOP.
Is the duty ratio DUTY. On the other hand, N> 400
When the rpm is reached, the process proceeds from step 304 to step 307.

FIG. 10 shows still another embodiment. In this embodiment, the duty ratio DUTY is set to the starting duty ratio DOPS when the first fuel injection is performed after the absolute pressure PM in the surge tank 6 becomes lower than the predetermined set value PMo, and then the start duty ratio DOPS. When the engine speed N becomes higher than a predetermined speed No, for example, 400 rpm, the duty ratio DUTY becomes the target duty ratio DOP.

FIG. 11 shows an engine start control routine, and this routine is repeatedly executed. Referring to FIG. 11, first, at step 400, the injection amount is calculated. Next, at step 401, it is judged if the absolute pressure PM in the surge tank 6 has become lower than a preset set value PMo. When PM ≧ PMo, the process jumps to step 404. On the other hand, PM <PMo
If so, the routine proceeds to step 402, where it is judged if it is the injection timing or not. If it is not the injection timing, step 404
Jump to On the other hand, when it is the injection timing, the routine proceeds to step 403, where an injection signal is generated, and then the routine proceeds to step 404. When the injection signal is generated, the fuel injection is started from the fuel injection valve 7 of the corresponding cylinder.

In step 404, the engine speed N is 400.
It is determined whether it has become higher than rpm. N ≦ 40
When it is 0 rpm, the routine proceeds to step 405, where it is judged if the injection signal is generated or not. When the injection signal has not yet been generated, the routine proceeds to step 406, where the duty ratio DUTY is made zero. On the other hand, when the injection signal is generated, the routine proceeds from step 405 to step 407 to calculate the starting duty ratio DOPS, and then in step 408, the starting duty ratio DOPS is set to the duty ratio DUTY. On the other hand, when N> 400 rpm, the routine proceeds from step 404 to step 409, where the target duty ratio DOP is calculated. Next, at step 410, the target duty ratio D
OP is set to the duty ratio DUTY.

[0033]

The amount of unburned HC discharged at the time of engine start can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing an opening area of an idling speed control valve.

FIG. 3 is a time chart showing a first embodiment of start-up control.

FIG. 4 is a flowchart showing a first embodiment of start-up control.

FIG. 5 is a time chart showing another embodiment of control at the time of starting.

FIG. 6 is a flowchart showing another embodiment of the control at the time of starting.

FIG. 7 is an overall view showing another embodiment of an internal combustion engine.

FIG. 8 is a time chart showing still another embodiment of the control at start-up.

FIG. 9 is a flowchart showing yet another embodiment of control at the time of starting.

FIG. 10 is a time chart showing yet another embodiment of the control at start-up.

FIG. 11 is a flowchart showing yet another embodiment of control at the time of starting.

[Explanation of symbols]

 5 ... Intake branch pipe 6 ... Surge tank 7 ... Fuel injection valve 9 ... Intake flow control valve 11 ... Throttle valve 12, 14 ... Bypass passage 13 ... Idling speed control valve 15 ... Assist air passage

Claims (3)

[Claims] 1. A throttle valve is arranged in the engine intake passage, a fuel injection valve is arranged in the engine intake passage downstream of the throttle valve, and a fuel injection valve is provided in the intake passage at a side of a nozzle port of the fuel injection valve. In an internal combustion engine that has an assist air supply port for ejecting air toward the fuel that is injected toward the fuel injection port, the fuel is injected from the assist air supply port until the fuel injection from the fuel injection valve is started during engine cranking. An assist air control device for an internal combustion engine, comprising an assist air supply control means for stopping the supply of assist air and starting the supply of assist air from an assist air supply port when fuel injection is started. 2. An intake air which is held in a closed position during engine cranking in an engine intake passage between the throttle valve and the fuel injection valve and which is opened when the engine speed exceeds a predetermined speed. The assist air control device according to claim 1, further comprising a flow control valve. 3. A throttle valve is arranged in the engine intake passage, a fuel injection valve is arranged in the engine intake passage downstream of the throttle valve, and a fuel injection valve is provided in the intake passage at a side of a nozzle port of the fuel injection valve. To supply air into the engine intake passage upstream of the assist air supply port and downstream of the throttle valve in an internal combustion engine having an assist air supply port for ejecting air toward the fuel injected toward The air supply port is provided, and the supply of assist air from the assist air supply port and the supply of air from the air supply port are stopped until fuel injection is started during engine cranking, and fuel injection is started. Sometimes the supply of assist air from the assist air supply port is started and the supply of air from the air supply port is stopped, or the assist air is supplied from the air supply port. An assist air control device for an internal combustion engine, which comprises a supply control means for supplying a small amount of air.