JP2727780B2 - 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 device for an internal combustion engine.

[0002]

2. Description of the Related Art A fuel injection valve for injecting fuel into an intake passage downstream of a throttle valve is provided, and an air assist passage is branched from the intake passage upstream of the throttle valve to control the air assist in the air assist passage. 2. Description of the Related Art There is known an internal combustion engine in which a valve is disposed, air is ejected from an air assist passage toward fuel injected from a fuel injection valve, and an engine idling speed is controlled by an air assist control valve ( See JP-A-58-85338).

[0003]

However, in such an internal combustion engine, when the engine is at full load, the pressures at the upstream and downstream of the throttle valve are substantially equal, so that the air assist passage extends from upstream of the throttle valve to downstream of the throttle valve. Not only does air not flow inside, but also air assist from the throttle valve downstream to the throttle valve upstream when the pressure downstream of the throttle valve becomes higher than the pressure upstream of the throttle valve due to intake pulsation generated downstream of the throttle valve The air flows backward in the passage. However, when the air flows backward in this way, the fuel flows backward together with the air, and the fuel flowing backward accumulates in the air assist passage. Even if fuel is accumulated in the air assist passage as described above, if the engine load becomes low, air flows again in the air assist passage from the throttle valve upstream to the throttle valve downstream, so that the accumulated fuel is discharged into the intake passage. You. However, in the above-described internal combustion engine, since the amount of air flowing through the air assist passage and the flow velocity of the air at this time are not sufficiently large, all the fuel accumulated in the air assist passage cannot be discharged into the intake passage. There is a problem that the fuel remaining in the air-assist passage corrupts the air-assist passage.

[0004]

According to the present invention, there is provided a fuel injection valve for injecting fuel into an intake passage downstream of a throttle valve. In an internal combustion engine in which an air assist passage is branched from the passage and an air assist control valve is arranged in the air assist passage and air is ejected from the air assist passage toward fuel injected from the fuel injection valve, During idling operation after completion, the air assist control valve is maintained in a partially open state, and during deceleration operation after completion of warm-up, the opening of the air assist control valve is set to be larger than the opening in the above partially open state. I have.

[0005]

During deceleration operation, the pressure difference between the upstream and downstream of the throttle valve increases, so that the flow velocity of the air flowing through the air assist passage becomes maximum. Also, during the deceleration operation, the opening of the air assist control valve is increased, so that a large amount of air flows at a high speed in the air assist passage.

[0006]

Referring to FIG. 1, reference numeral 1 denotes an engine body, 2 denotes a piston, 3 denotes a cylinder head, 4 denotes a combustion chamber, 5 denotes an intake valve,
6 indicates an intake port, 7 indicates an exhaust valve, and 8 indicates an exhaust port. The intake port 6 is connected to a surge tank 10 via a corresponding branch pipe 9, and the surge tank 10 is connected to a common intake duct 11.
And an air cleaner (not shown) via an air flow meter 12. An air assist chamber 13 is formed in each branch pipe 9, and a fuel injection valve 14 is disposed in the air assist chamber 13. The air assist chamber 13 is connected on the one hand to the inside of the branch pipe 9 via a fuel air outlet 15 and on the other hand is connected to a bypass control valve 17 via an air assist passage 16.
In the embodiment shown in FIG. 1, the bypass control valve 17 is mounted on the outer wall surface of the surge tank 10. Next, the structure of the bypass control valve 17 will be described with reference to FIG.

Referring to FIG. 2, a non-rotatable but axially slidable valve shaft 18 is arranged in a bypass control valve 17, and a rotor 20 of a step motor 19 is mounted on the valve shaft 18.
Are screwed together. Therefore, when the rotor 20 is rotated, the valve shaft 18 is moved in the axial direction. On the other hand, the bypass control valve 17 is formed with a high-pressure chamber 22 and a low-pressure chamber 23 separated by a partition 21. The high-pressure chamber 22 and the low-pressure chamber 23 are mutually connected through a valve port 24 formed on the partition 21. I can communicate. The high-pressure chamber 22 is connected on the one hand to the intake duct 11 upstream of the throttle valve 26 via an air supply passage 25 as shown in FIG.
It is made to communicate within 10. On the other hand, the low pressure chamber 23 is connected to the air assist chamber 13 via the air assist passage 16. A control valve 29 for controlling the opening area of the valve port 28 is disposed in the high-pressure chamber 22, and an air-assist control valve 30 for controlling the opening area of the valve port 24 is disposed in the low-pressure chamber 23. .
Next, the opening degrees of the control valves 29 and 30 will be described with reference to FIG.

FIG. 3 shows the relationship between the opening degree of each control valve 29, 30 and the step position ST of the step motor 19. 3, a solid line A indicates the opening of the air assist control valve 30, and a solid line B indicates the opening of the control valve 29.
As can be seen from FIG. 3, when the step position ST of the step motor 19 is zero, that is, when the valve shaft 18 is closest to the valve port 28 side in FIG. 2, the opening degrees of both the control valves 29 and 30 become zero. . On the other hand, when the step position ST of the step motor 19 increases, the valve shaft 18 moves in a direction away from the valve port 28. At this time, as shown in FIG. 3, the opening of the control valve 29 is maintained at zero, while the opening of the air assist control valve 30 increases as the step position ST increases. On the other hand, the step position ST air assist valve 30 becomes the ST _m in FIG. 3 becomes maximum opening, air assist valve 30 also becomes large subsequent step position ST is maintained at the maximum opening degree.
On the other hand, the opening degree of the control valve 29 is ST _{m at the} step position ST.
Exceeds the maximum step position MAX.
The value increases as the step position ST increases until.

When the air assist control valve 30 is opened, the air sent into the high pressure chamber 22 via the air supply passage 25 is supplied to the air assist chamber via the low pressure chamber 23 and the air assist passage 16.
It is sent into 13. The air sent into the air assist chamber 13 is injected from the fuel air outlet 15 into the intake port 6 together with the fuel injected from the fuel injection valve 14, thereby promoting atomization of the fuel. On the other hand, control valve 29
When the valve is opened, the air in the high-pressure chamber 22 is supplied to the surge tank 10 via the valve port 28 on the one hand, and is supplied to the air assist chamber 13 on the other hand. In the embodiment shown in FIG. 1, the bypass control valve 17 is provided to control the amount of air for air assist and at the same time to control the engine idling speed.

That is, FIG. 3 further shows a target step position _STo.
And it has been shown relationship between the engine coolant temperature T, before lower warming up of the engine coolant temperature T step position ST is the step motor 19 so that the target step position ST _o is driven and controlled. Target step position ST _o as the engine coolant temperature T As can be seen from Figure 3 decreases increases, the target step position ST _o shown in FIG. 3 is stored in the ROM 52 as a function of engine coolant temperature T. Accordingly, as can be seen from FIG. 3, during the idling operation before the completion of the warm-up in which the engine cooling water temperature T is low, the step position ST of the step motor 19 is set to a region indicated by D in FIG. At this time, a large amount of air is supplied via the bypass control valve 17 because both the control valves 29 and 30 are opened. Next, the engine cooling water temperature T
Target step position ST _o becomes smaller as increases, the step motor 19 at step position ST in the vicinity indicated by C in FIG. 3 becomes the time to warm-up is completed is controlled. On the other hand, even during the idling operation after the completion of the warm-up, the step motor 19 is controlled at the step position ST near C shown in FIG. Therefore, at this time, the opening of the air assist control valve 30 is controlled so that the engine idling speed becomes the target speed. The step position ST of the step motor 19 is controlled based on the output signal of the electronic control unit 50 (FIG. 1).

As shown in FIG. 1, the electronic control unit 50
Is a ROM (Read Only Memory) consisting of a digital computer and interconnected via a bidirectional bus 51
52, RAM (random access memory) 53, CPU (microprocessor) 54, input port 55 and output port
56 is provided. The air flow meter 12 generates an output voltage proportional to the amount of intake air, and this output voltage is input to the input port 55 via the AD converter 57. A throttle switch 58 that is turned on when the throttle valve 26 reaches an idling opening degree is attached to the throttle valve 26, and an output signal of the throttle switch 58 is input to an input port 55.
A water temperature sensor 59 that generates an output voltage proportional to the engine cooling water temperature is attached to the engine body 1, and the output voltage of the water temperature sensor 59 is input to an input port 55 via an AD converter 60. Further, a rotation speed sensor 61 for generating an output pulse representing the engine speed and a vehicle speed sensor 62 for producing an output pulse representing the vehicle speed are connected to the input port 55. On the other hand, the output port 56 is connected to the fuel injection valve 14 via drive circuits 63 and 64, respectively.
And it is connected to the step motor 19 of the bypass control valve 17.

Next, a processing routine for a cut flag indicating that the supply of fuel should be stopped will be described with reference to FIG. This routine is repeatedly executed in the main routine. Referring to FIG. 4, first, at step 70, it is determined whether or not the cut flag is set. When the cut flag is not set, the routine proceeds to step 71, where it is determined whether or not the throttle switch 58 is on, that is, whether or not the throttle valve 26 is at the idling position. When the throttle valve 26 is at the idling position, the routine proceeds to step 72, where it is determined whether or not the engine speed N is higher than a constant value Nh, for example, 2000 rpm. When N ≧ Nh, the routine proceeds to step 73, where the cut flag is set. When the cut flag is set, the operation of fuel injection from the fuel injection valve 14 is stopped in a routine (not shown). The process proceeds to step 73 when the throttle valve 26 is in the idling position and the engine speed N is high, that is, during deceleration operation. Therefore, the fuel supply is stopped during the deceleration operation.

On the other hand, once the cut flag is set, the routine proceeds from step 70 to step 74 where the throttle switch
It is determined whether or not 58 is ON, that is, whether or not the throttle valve 26 is at the idling position. When the throttle valve 26 is opened, the routine jumps to step 76, where the cut flag is reset, and fuel injection from the fuel injection valve 14 is started. On the other hand, when the throttle valve 26 is maintained at the idling position, the routine proceeds to step 75, where it is determined whether or not the engine speed N has become lower than a fixed value Nl, for example, 14000 rpm. When N ≦ Nl, the routine proceeds to step 76, where the cut flag is reset, and fuel injection is started.

Next, a bypass control valve performed in an embodiment of the present invention with reference to a time chart shown in FIG.
The seventeenth control method will be described. In FIG. 5, the section t ₁
Indicates before the completion of warm-up. At this time, as the engine cooling water temperature T increases, the opening of the control valve 29 gradually decreases, and when the control valve 29 is fully closed, the air assist control valve 30 is gradually closed from the fully open state. In FIG. 5, section t
Reference numeral ₂ denotes an idling operation after the completion of warm-up. At this time, the control valve 29 is fully closed, and the opening degree of the air assist control valve 30 is controlled by the step motor 19 so that the engine speed becomes the target idling speed.
At this time, the air assist control valve 30 is partially open. Interval t ₃ in FIG. 5 shows a high-load operation. Also at this time, the control valve 29 is maintained in a fully closed state, and the air assist control valve 30 is maintained in a partially open state.

A section t _{4 in} FIG. 5 shows an initial stage of the deceleration operation. If the engine speed N at the start of the deceleration operation is higher than Nh, a cut flag is set as shown in FIG. During the deceleration operation, the control valve 29 and the air assist control valve 30 are fully opened while the engine speed N is equal to or higher than a constant speed, for example, 2500 rpm. During the deceleration operation, a larger negative pressure than in the idling operation is applied to the branch pipe 9.
In the air-assist control valve
When 30 is fully opened, a large amount of air is supplied to the air assist passage.
It will flow at a high speed in 16. Thus, all the fuel accumulated in the air assist passage 16 is discharged into the branch pipe 9 through the fuel air outlet 15 by this air flow.

[0016] t ₅ of FIG. 5 shows the second half after the deceleration operation. During the deceleration operation, when the engine speed N becomes lower than 2500 rpm, the control valve 29 is fully closed again, the air assist control valve 30 is closed to a partially opened state before fully opened, and then before the fully opened state. It is held in a partially open state. Next, when the engine speed N becomes lower than Nl, the cut flag is reset and fuel injection is restarted. Next, when the engine is idling, the air assist control valve 30 is adjusted so that the engine speed again reaches the target idling speed.
Is controlled by the step motor 19.

Next, a control routine of the bypass control valve 17 shown in FIG. 6 will be described with reference to a time chart shown in FIG. This routine is executed by interruption every predetermined time. Referring to FIG. 6, first, at step 80, it is determined based on the output signal of the water temperature sensor 59 whether the engine cooling water temperature T is higher than a fixed value, for example, 60 ° C. T
<When the 60 ° C. target step position ST ₀ based on the relationship shown in FIG. 3 from the engine coolant temperature T proceeds to step 81 is calculated. Then step position ST in step 82 step motor 19 is set to the target step position ST _0, step
Go to 83. In step 83, the step motor 19 is moved so that the step position of the step motor 19 becomes the step position ST.
Is driven.

On the other hand, if it is determined at step 80 that T ≧ 60 ° C., the routine proceeds to step 84, where it is determined whether or not the cut flag is set. When the cut flag is not set, the routine proceeds to step 85, where it is determined whether or not the idling operation is being performed. For example, when the throttle switch 58 is on and the vehicle speed V is 2 km / h or less, it is determined that the vehicle is idling. If it is determined that the vehicle is idling, step
Proceeding to 86, the target idling rotational speed No is calculated.
Next, at step 87, it is determined whether or not the engine speed N is larger than (No + α). Here, α is a small constant value. When N ≧ of (No + alpha) is the step position ST proceeds to step 90 is decremented by 1, then the routine proceeds to step 83 to step position ST after the idling step position ST _a in step 91. On the other hand, if it is determined in step 87 that N <(No + α), the routine proceeds to step 88, where it is determined whether or not N ≦ (No−α). When N ≦ (No−α), the routine proceeds to step 89, where the step position ST is incremented by one, and then proceeds to step 91. Thus, the engine speed N is controlled to be (No−α) <N <(No + α). On the other hand, the idling step position ST _i is the step position ST proceeds to step 92 when it is judged not idling at step 85. Therefore, when the engine is not idling, the step motor 19 is not operated.
It is held in the idling step position ST _i.

On the other hand, when it is determined in step 84 that the cut flag has been set, the routine proceeds to step 93, where it is determined whether or not the engine speed N is higher than a fixed value, for example, 2500 rpm. Step when N ≧ 2500r.pm
Proceeding to 94, the vehicle speed V becomes 10 km / from the output signal of the vehicle speed sensor 62.
It is determined whether or not it is faster than h. When V ≧ 10 km / h, the routine proceeds to step 95, where the step position ST is set to the maximum step position MAX. Therefore, at this time, both the control valve 29 and the air assist control valve 30 are fully opened. On the other hand, when the cut flag is set, N <2500r.
When pm or V <10 km / h, or when the cut flag is reset, the routine proceeds to step 95, where the control valve 29 is controlled.
Is is completely closed, air assist control valve 30 is made to closed until opening degree corresponding to the idling step position ST _i.

[0020]

The fuel accumulated in the air assist passage can be completely discharged into the intake passage by increasing the opening of the air assist control valve during the deceleration operation. You can prevent it from getting corrupted.

[Brief description of the drawings]

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

FIG. 2 is an enlarged side sectional view of a bypass control valve.

FIG. 3 is a diagram showing an opening degree of a pair of control valves provided in a bypass control valve.

FIG. 4 is a flowchart for controlling a cut flag.

FIG. 5 is a time chart.

FIG. 6 is a flowchart for controlling a bypass control valve.

[Explanation of symbols]

 13 ... air assist chamber 14 ... fuel injection valve 15 ... fuel air injection port 16 ... air assist passage 17 ... bypass control valve 26 ... throttle valve 30 ... air assist control valve

Claims (1)

(57) [Claims] A fuel injection valve for injecting fuel toward an intake passage downstream of the throttle valve, wherein an air assist passage is branched from the intake passage upstream of the throttle valve and air assist is provided in the air assist passage; In an internal combustion engine in which a control valve is arranged and air is ejected from the air assist passage toward fuel injected from the fuel injection valve, the air assist control valve is partially opened during idling operation after completion of warm-up. And the opening degree of the air assist control valve is set to be larger than the opening degree in the partially opened state during the deceleration operation after the completion of the warm-up.