JPH04295178A - Suction control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent accumulation of fuel in an air assist passage. CONSTITUTION:A fuel injection valve 14 is arranged in an air assist chamber 13 and injection fuel is injected toward a suction port 6 togetherwith air fed in the air assist chamber 13 through an air assist passage 16. An air amount fed through a suction duct 11 on the upper stream of a throttle valve 26 to the air assist chamber 13 is controlled by means of an air assist control valve 30 located in a bypass control valve 17. The air assist control valve 30 is held in a normal partially opening state and fully opened during deceleration running.

Description

[Detailed description of the invention]

0001

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

0002

[Prior Art] A fuel injection valve is provided for injecting fuel into an intake passage downstream of a throttle valve, and an air assist passage is branched from the intake passage upstream of the throttle valve to perform air assist control in the air assist passage. An internal combustion engine is known in which a valve is disposed, air is jetted from an air assist passage toward fuel injected from a fuel injection valve, and the engine idling speed is controlled by an air assist control valve. Japanese Patent Publication No. 58-85338
(see publication).

0003

However, in such an internal combustion engine, when the engine is operated at full load, the pressures upstream and downstream of the throttle valve are almost equal, so the air assist passage is connected from upstream of the throttle valve to downstream of the throttle valve. Not only does air not flow inside the throttle valve, but air assist is applied from the downstream side of the throttle valve to the upstream side of the throttle valve when the pressure downstream of the throttle valve becomes higher than the pressure upstream of the throttle valve due to the intake pulsation that occurs downstream of the throttle valve. Air flows backwards in the passage. However, when the air flows backward in this way, the fuel also flows backward together with the air, so that the fuel that flows backward accumulates in the air assist passage. Even if fuel accumulates in the air assist passage in this way, if the engine load becomes low, the air will flow through the air assist passage again from upstream of the throttle valve to downstream of the throttle valve, so the accumulated fuel will be discharged into the intake passage. Ru. However, in the above-mentioned internal combustion engine, the amount of air flowing in the air assist passage and the flow velocity of the air are not large enough at this time, so all the fuel accumulated in the air assist passage cannot be discharged into the intake passage. A problem arises in that the air assist passage is corroded by the fuel remaining in the air assist passage.

0004

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention includes a fuel injection valve for injecting fuel into the intake passage downstream of the throttle valve. In an internal combustion engine in which an air assist passage is branched from a passage, an air assist control valve is disposed within the air assist passage, and air is jetted from the air assist passage toward fuel injected from a fuel injection valve. During idling operation after the completion of warm-up, the air assist control valve is held in a partially open state, and during deceleration operation after completion of warm-up, the opening degree of the air assist control valve is made to be larger than the opening degree in the above-mentioned partially open state. There is.

[0005]

[Operation] During deceleration operation, the pressure difference between the upstream and downstream sides of the throttle valve increases, so the flow velocity of air flowing through the air assist passage becomes maximum. Furthermore, during deceleration operation, the opening degree of the air assist control valve is increased, so that a large amount of air ends up flowing through the air assist passage at a high speed.

[0006]

[Embodiment] Referring to FIG. 1, 1 is an engine body, 2 is a piston, 3 is a cylinder head, 4 is a combustion chamber, 5 is an intake valve,
Reference numeral 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 an air cleaner (not shown) via a common intake duct 11 and 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 within this air assist chamber 13. The air assist chamber 13 communicates on the one hand with the branch pipe 9 via a fuel air outlet 15 and on the other hand via an air assist channel 16 with a bypass control valve 17 . 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 explained with reference to FIG.

Referring to FIG. 2, a valve shaft 18 that cannot rotate but is slidable in the axial direction is disposed within the bypass control valve 17, and a rotor 20 of a step motor 19 is mounted on this valve shaft 18. 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, and these high pressure chamber 22 and low pressure chamber 23 are connected to each other via a valve port 24 formed on the partition 21. It is forced to communicate. Hyperbaric chamber 22
is connected on the one hand to the intake duct 11 upstream of the throttle valve 26 as shown in FIG. 1 via the air supply passage 25;
On the other hand, it is communicated into surge tank 10 via valve port 28 . 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 arranged in the high pressure chamber 22, and an air assist control valve 30 for controlling the opening area of the valve port 24 is arranged in the low pressure chamber 23. . Next, the opening degrees of these control valves 29 and 30 will be explained with reference to FIG. 3.

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. In addition, in FIG. 3, solid line A indicates the air assist control valve 30.
The solid line B shows the opening degree 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.
The opening degree of is 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 degree of the control valve 29 is maintained at zero, while the opening degree of the air assist control valve 30 increases as the step position ST increases. On the other hand, the step position ST is S in FIG.
When Tm is reached, the air assist valve 30 reaches its maximum opening,
Thereafter, even if the step position ST becomes larger, the air assist valve 30 is maintained at the maximum opening degree. On the other hand, the opening degree of the control valve 29 is such that the step position ST is S.
Once Tm is exceeded, the step position ST increases as the step position ST becomes larger until it reaches the maximum step position MAX.

[0009] When the air assist control valve 30 opens, the air sent into the high pressure chamber 22 via the air supply passage 25 is sent into the air assist chamber 13 via the low pressure chamber 23 and the air assist passage 16. Air assist chamber 13
The air sent inside is injected from the fuel air jet port 15 into the intake port 6 together with the fuel injected from the fuel injection valve 14, thus promoting atomization of the fuel. On the other hand, when the control valve 29 is opened, the high pressure chamber 22
The air inside is fed into the surge tank 10 via the valve port 28 on the one hand and into 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 the target step position ST.
The relationship between the engine cooling water temperature T and the engine cooling water temperature T is shown, and the step motor 19 is set so that the step position ST becomes the target step position STo before the warm-up is completed when the engine cooling water temperature T is low.
is driven and controlled. As can be seen from FIG. 3, the target step position STo becomes larger as the engine coolant temperature T decreases, and the target step position STo shown in FIG. 3 is stored in the ROM 52 in advance as a function of the engine coolant temperature T. Therefore, as can be seen from FIG. 3, during idling operation before warm-up is completed when the engine cooling water temperature T is low, the step motor 19
The step position ST is set in the area indicated by D in FIG. At this time, since both control valves 29 and 30 are opened, a large amount of air is supplied via the bypass control valve 17. Next, as the engine cooling water temperature T increases, the target step position STo becomes smaller, and when warm-up is completed, the step motor 19 is controlled at a nearby step position ST shown by C in FIG. On the other hand, even during idling operation after completion of warm-up, the step motor 19 is controlled at a nearby step position ST indicated by C in FIG. Therefore, at this time, the opening degree of the air assist control valve 30 is controlled so that the engine idling rotation speed becomes the target rotation speed. Step position S of step motor 19
T is controlled based on the output signal of electronic control unit 50 (FIG. 1).

As shown in FIG. 1, the electronic control unit 5
0 consists of a digital computer, bidirectional bus 5
A ROM (read only memory) 52, a RAM (random access memory) 53, and a C
It includes a PU (microprocessor) 54, an input port 55, and an output port 56. 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. The throttle valve 26 includes a throttle switch 58 that is turned on when the throttle valve 26 reaches the idling opening.
is attached, and the output signal of this throttle switch 58 is input to the 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.
The output voltage is input to the input port 55 via the AD converter 60. Further, a rotation speed sensor 61 that generates an output pulse representing the engine rotation speed, and a vehicle speed sensor 62 that generates 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 step motor 19 of the fuel injection valve 14 and the bypass control valve 17 via drive circuits 63 and 64, respectively.

Next, a processing routine for a cut flag indicating that fuel supply should be stopped will be explained with reference to FIG. This routine is executed repeatedly within the main routine. Referring to FIG. 4, first, in step 70, it is determined whether a cut flag is set. If the cut flag is not set, the process proceeds to step 71, where it is determined whether the throttle switch 58 is on, that is, whether the throttle valve 26 is in the idling position. When the throttle valve 26 is in the idling position, the process proceeds to step 72 where the engine speed N is set to a constant value Nh, for example 2000r.
．． p. It is determined whether or not it is higher than m. N≧Nh
If so, the process advances to step 73 and a cut flag is set. When the cut flag is set, the fuel injection action from the fuel injection valve 14 is stopped in a routine not shown. Proceed to step 73 with throttle valve 2
6 is in the idling position and the engine speed N is high, that is, during deceleration operation. Therefore, fuel supply is stopped during deceleration operation.

On the other hand, once the cut flag is set, the process proceeds from step 70 to step 74, where it is determined whether the throttle switch 58 is on, that is, whether the throttle valve 26 is in the idling position. When the throttle valve 26 is opened, the process jumps to step 76, the cut flag is reset, and fuel injection from the fuel injection valve 14 is started. On the other hand, if the throttle valve 26 is maintained at the idling position, step 75
The engine speed N is set to a constant value Nl, for example 1400.
0r. p. It is determined whether or not the value has become lower than m. N
When ≦Nl, the process proceeds to step 76, the cut flag is reset, and fuel injection is started.

Next, a method of controlling the bypass control valve 17 carried out in the embodiment of the present invention will be explained with reference to the time chart shown in FIG. In Fig. 5, the interval t
1 indicates before completion of warm-up. At this time, as the engine cooling water temperature T rises, the opening degree of the control valve 29 gradually becomes smaller, 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 t2 indicates idling operation after 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 adjusted by the step motor 19 so that the engine speed becomes the target idling speed.
controlled by At this time, the air assist control valve 30 is in a partially open state. In FIG. 5, section t3 indicates high load operation. At this time as well, the control valve 29 is kept fully closed, and the air assist control valve 30 is kept partially open.

Section t4 in FIG. 5 indicates the initial stage of deceleration operation. Engine speed N when deceleration operation starts is Nh
If it is higher than , a cut flag is set as shown in FIG. Also, during deceleration operation, the engine speed N
is a constant rotation speed, for example 2500r. p. m or more, the control valve 29 and the air assist control valve 30 are fully opened. During deceleration operation, a larger negative pressure is generated in the branch pipe 9 than during idling operation, and therefore, when the air assist control valve 30 is fully opened at this time, a large amount of air flows through the air assist passage 16 at a high speed. become. This air flow causes all the fuel accumulated in the air assist passage 16 to be transferred to the branch pipe 9 via the fuel air jet port 15.
It will be discharged inside.

t5 in FIG. 5 indicates the latter half of the deceleration operation. Engine speed N is 2500r during deceleration operation
．． p. When the value becomes lower than m 2 , the control valve 29 is fully closed again, the air assist control valve 30 is closed to the partially open state before fully opening, and then maintained in the partially open state before fully opening. Next, when the engine speed N becomes lower than Nl, the cut flag is reset and fuel injection is restarted. Next, when the engine enters an idling state, 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 again.

Next, the control routine for the bypass control valve 17 shown in FIG. 6 will be explained with reference to the time chart shown in FIG. This routine is executed by interrupts at regular intervals. Referring to Figure 6, first step 8
0, 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 certain value, for example, 60°C. When T<60°C, the process proceeds to step 81, where the target step position ST0 is calculated from the engine cooling water temperature T based on the relationship shown in FIG. Next, in step 82, the step position ST of the step motor 19 is set to the target step position ST0, and the process proceeds to step 83. In step 83, the step position of the step motor 19 is set to step position S.
The step motor 19 is driven so that T is reached.

On the other hand, if it is determined in step 80 that T≧60° C., the process proceeds to step 84, where it is determined whether or not a cut flag is set. If the cut flag is not set, the process proceeds to step 85, where it is determined whether or not the vehicle is idling. For example, the throttle switch 58 is on and the vehicle speed V is 2.
When the speed is less than km/h, it is determined that the vehicle is idling. When it is determined that the operation is idling, the process advances to step 86 and the target idling speed No.
is calculated. Next, in step 87, the engine speed N is (No + α)
It is determined whether or not it is larger than . Here, α is a small constant value. If N≧(No + α), step 9
0, step position ST is decremented by 1, then step 91 sets step position ST to idling step position STa, and then step 8
Proceed to step 3. On the other hand, in step 87, N<(No +
When it is determined that α), the process proceeds to step 88, where it is determined whether N≦(No − α). N≦(
If No - α), the process proceeds to step 89 where the step position ST is incremented by 1, and then the process proceeds to step 91. In this way, the engine speed N becomes (No −
α)<N<(No + α). On the other hand, if it is determined in step 85 that the vehicle is not idling, the process proceeds to step 92, where the idling step position STi is set as the step position ST. Therefore, when the vehicle is not idling, the step motor 19 is held at the idling step position STi.

On the other hand, if it is determined in step 84 that the cut flag has been set, the process proceeds to step 93 where the engine speed N is set to a constant value, for example 2500 r. p. m
It is determined whether or not it is higher than . N≧2500r. p
．． m, the process advances to step 94 and the vehicle speed sensor 62
It is determined from the output signal whether the vehicle speed V is faster than 10 km/h. Step 9 when V≧10km/h
Proceed to step 5 and step position ST is maximum step position MAX
It is said that 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. p
．． m or when V<10 km/h, or when the cut flag is reset, the process proceeds to step 95, where the control valve 29 is fully closed and the air assist control valve 30 is closed.
is closed to the opening degree corresponding to the idling step position STi.

[0020]

[Effects of the Invention] By increasing the opening degree of the air assist control valve during deceleration operation, the fuel accumulated in the air assist passage can be completely discharged into the intake passage. Corrosion can be prevented.

[Brief explanation of drawings]

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

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

FIG. 3 is a diagram showing the opening degrees of a pair of control valves provided in the 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 room 14...Fuel injection valve 15...Fuel air outlet 16...Air assist passage 17...Bypass control valve 26...Throttle valve 30...Air assist control valve

Claims (1)

[Claims] 1. A fuel injection valve is provided for injecting fuel into an intake passage downstream of a throttle valve, and an air assist passage is branched from the intake passage upstream of the throttle valve to inject fuel into the air assist passage. In an internal combustion engine in which a control valve is arranged and air is injected from the air assist passage toward fuel injected from a fuel injection valve, the air assist control valve is in a partially open state during idling operation after completion of warm-up. An air intake control device for an internal combustion engine, wherein the opening degree of the air assist control valve is increased more than the opening degree in the partially open state during deceleration operation after completion of warm-up.