JP2870607B2 - Engine intake system - 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 system for an engine having a cold start injector in an intake passage.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 63-2977
As shown in Japanese Patent Publication No. 45, a cold start injector is provided in an intake passage, and at the time of a cold start in which fuel is not easily vaporized, extra fuel is injected from the cold start injector in addition to fuel injected from a normal injector. Devices adapted to supply are known. In particular, in the device of this publication, a control valve and a cold start injector are provided in a bypass passage that bypasses a throttle valve and a surge tank, and attempts to promote mixing of air and fuel by using a relatively fast air flow in the bypass passage.

[0003]

However, in this type of intake device, the bypass passage has a reduced passage area in order to accurately adjust the intake air flow rate for controlling idle speed. At the time of starting, while the throttle valve of the main intake passage is set to the minimum opening degree, and a certain amount of intake air flows through this throttle valve,
The shortage is input to the engine through the bypass passage. Accordingly, although the flow velocity in the bypass passage increases to some extent, the flow rate is small, and if a cold start injector is provided in the bypass passage, the amount of air mixed with the fuel when the fuel injected from the injector is relatively large is insufficient. Therefore, there is a limit in promoting fuel atomization and mixing.

It is conceivable to dispose a cold start injector in the main intake passage in which the throttle valve is provided. However, only by doing so, the fuel flow is low due to the low flow velocity in the main intake passage at the time of starting. And mixing are not promoted.

The present invention has been made in view of the above circumstances, and at the time of a cold start, the fuel injected from a cold start injector is sufficiently mixed with a large amount of air to greatly promote the atomization and mixing of the fuel. It is an object of the present invention to provide an intake device for an engine that can improve the startability in a short time.

[0006]

In order to achieve the above object, the present invention comprises a cold start injector for injecting fuel at the time of a cold start, and the cold start injector is provided according to the state of the engine at the time of a cold start. In an intake system for an engine, wherein the time of fuel injection supply from an injector is adjusted, the cold start injector is provided in a main intake passage upstream of an intake passage collecting portion and a throttle valve is disposed, and the throttle valve is provided in the main intake passage. Throttle opening adjusting means for adjusting the opening of the valve, and the throttle opening adjusting means for increasing the opening of the throttle valve as the time is longer according to the time of fuel injection supply from the cold start injector. Control means for controlling the throttle valve.

[0007] In this configuration, it is preferable that the cold start injector is disposed at a position close to an outer peripheral portion of the throttle valve when the throttle valve is at a partially open position.

In addition, a control valve for adjusting an intake air flow rate in the bypass passage is provided in a bypass passage that bypasses the throttle valve, and the control valve is controlled in accordance with an opening degree of the throttle valve at a cold start. It is preferable to include a control valve control unit that performs correction control of the intake air amount.

Further, after the fuel injection from the cold start injector is completed, the throttle valve control is performed so that the throttle valve is returned to the basic opening degree and the intake air flow rate in the bypass passage is adjusted by idle speed feedback control. It is preferable to configure the control means and the control valve control means. It is preferable that the throttle opening adjusting means is formed of an actuator driven in accordance with an electric signal.

[0010]

According to the above construction, when the fuel injection supply time from the cold start injector is lengthened at the time of a cold start, the flow rate and the flow velocity of the air passing through the throttle valve are increased in a state where the fuel injection supply time is increased. As a result, fuel is injected and sufficiently mixed with air.

When the cold start injector is arranged near the outer peripheral portion of the throttle valve when the throttle valve is at the partially open position, the flow velocity of air at the fuel injection position is increased.

When the control valve of the bypass passage is controlled according to the opening of the throttle valve,
The intake air amount to the engine is properly adjusted even when the throttle valve is opened at the time of cold operation.

After the end of the fuel injection supply from the cold start injector, the throttle valve is returned to the basic opening, and the intake flow rate in the bypass passage is adjusted by the idle speed feedback control.
Transition to the idle operation state smoothly.

[0014]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows the structure of the entire apparatus. In this figure, an intake passage 3 for supplying intake air to a combustion chamber 2 of each cylinder and an exhaust passage 4 for discharging exhaust gas from the combustion chamber 2 of each cylinder are connected to the engine 1.

The intake passage 3 has a branch passage 6 for each cylinder downstream of a surge tank (intake passage collecting portion) 5, and an intake port at the downstream end of each branch passage 6 opens to the combustion chamber 2 of each cylinder. A common injector 7 is provided near each intake port. A main intake passage 8 common to each cylinder is formed upstream of the surge tank 5. A throttle valve 11 is provided in the main intake passage 8, and an air cleaner 12 is provided upstream of the main intake passage 8.
And an air flow meter 13.

The throttle valve 11 is opened and closed by an electric actuator (throttle opening adjusting means) 14 such as a step motor driven according to an electric signal.
The opening of the throttle valve 11 can be adjusted according to the electric signal. An ISC (idle speed control) passage 15 is connected to the main intake passage 8 as a bypass passage for bypassing the throttle valve 11.
The SC passage 15 is provided with an ISC valve 16 as a control valve for adjusting the intake flow rate in this passage.

The cold start injector 1 is provided in the main intake passage 8 in which the throttle valve 11 is provided.
8 are provided. The cold start injector 18 is for injecting and supplying fuel when the engine is cold started, separately from the usual injector 7.

Reference numeral 20 denotes a control unit (ECU) which outputs a control signal to the service injector 7 and the cold start injector 18 to control fuel injection therefrom, and sends a control signal to the actuator 14 of the throttle valve 11. The output controls the opening of the throttle valve 11, and further controls the ISC valve 16 and the like. The control unit 20 receives an intake air amount detection signal from the air flow meter 13, an engine speed signal from a speed sensor 21 provided in the distributor 10, and a throttle opening detection signal from a throttle opening sensor 22. A water temperature detection signal from a water temperature sensor 23 provided in a water jacket of the engine, an intake temperature detection signal from an intake temperature sensor 24 provided in the intake passage 3, a signal from a starter switch 25, and the like are input.

FIG. 2 is an enlarged view of a portion where the throttle valve 11, the ISC passage 15, the cold start injector 18 and the like are arranged. As shown in this figure, the cold start injector 18 is attached to the passage wall of the main intake passage 8 at a position near the outer peripheral portion of the throttle valve when the throttle valve 11 is at the partially open position. Further, the ISC valve 16 is formed by a duty solenoid valve that adjusts a flow rate of the ISC passage 15 according to a duty signal. In the example shown in this figure, a passage 26 for allowing air to flow when an external load is actuated or the like is provided in addition to the ISC passage 15 as a passage bypassing the throttle valve 11, and this passage 26 is provided in this passage 26. An air valve 27 that opens and closes 26 is provided.

FIG. 3 shows the control unit 20;
The control unit 20 includes CSI (cold start injector) control means 31, T / V (throttle valve) control means 32, and ISC control means 33 as control valve control means. The CSI control means 31 determines the time of cold start of the engine, outputs an operation signal for causing the cold start injector 18 to perform fuel injection at the time of cold start, and in this case, causes the cold start injector 18 to perform fuel injection. The time is set according to the water temperature or the like, and the lower the temperature is, the longer the fuel injection time is.

The T / V control means 32 controls the throttle valve 11 during cold start according to the fuel injection time set by the CSI control means 31 as the time becomes longer.
Control signal to increase the opening of the throttle valve 11
To the actuator 14. The throttle valve 11 is returned to the basic opening (minimum opening) during idling operation after the end of the fuel injection supply from the cold start injector 18, and during normal operation thereafter, the throttle valve 11 is opened according to the accelerator pedal depression amount and the like. Each time, a signal for controlling the throttle valve 11 is output to the actuator 14.

The ISC control means 33 controls the opening of the throttle valve 11 during the cold start in which the fuel is injected from the cold start injector 18 and the throttle valve 11 is opened accordingly. A control signal is output to the ISC valve 16 so as to perform the intake air correction control. If the control at the time of the cold start is completed and the operation is shifted to the idling operation, the ISC passage 15
The idle flow rate is adjusted by feedback control of idle speed, that is, the duty of the control signal for the ISC valve 16 is feedback-corrected according to the difference between the detected speed value and the target idle speed.

FIG. 4 is a flowchart showing an example of control of the throttle valve and the like by the control unit 20. This flowchart shows a routine for calculating the CSI injection time, the throttle opening, the duty of the ISC valve, and the like, which will be described later. Based on the values obtained in this routine, the cold start injector 18,
The processing for driving the actuator 4 and the ISC valve 16 and the like and the processing for controlling the ordinary injector are performed by an interrupt routine (not shown) different from this routine.

In this flowchart, when started, first, in step S1, detection signals from various sensors are read. Subsequently, in step S2, it is checked whether or not the CSI operating condition is satisfied. This determination satisfies the condition that the engine is cranking from when the starter is turned on until the engine rotation speed reaches the startup end determination rotation speed, and that the engine water temperature and intake air temperature are in a cold state below a predetermined value. It is determined whether or not to perform. Under the CSI operating condition, the following control at the time of cold start (steps S3 to S3)
Perform 8).

As the control at the time of the cold start, first, at step S3, the CSI injection time (time of fuel injection from the cold start injector 18) is determined. Here, the CSI injection time is determined according to the state of the engine,
For example, according to the water temperature, the CSI injection time may be set longer as the temperature is lower, and the CSI injection time may be determined based on a map or the like in which such a relationship is set in advance. Subsequently, in step S4, the required air amount is calculated from a map or the like according to the state of the engine speed, water temperature, and the like at that time. Next, in step S5, the throttle opening is determined according to the CSI injection time. In this case, as shown in FIG.
The throttle opening is set to be larger as the SI injection time becomes longer, and the throttle opening is determined from a map in which such a relationship is set in advance. In step S6 following step S5, the throttle valve passing air amount is calculated based on the relationship between the throttle opening and the throttle valve passing air amount as shown in FIG. Further, step S7
Then, by subtracting the throttle valve passing air amount and the air valve passing air amount obtained according to the air valve operating state from the required air amount, the air is circulated through the ISC valve 16 in the ISC share, that is, the required air amount. Calculate the amount of air to be consumed. Then, in step S8,
The duty of the ISC valve 16 corresponding to the ISC share is calculated, and the process returns.

If the determination in step S2 is NO, for example, after the end of the cold start process, the determination in step S9 is whether or not the start is to be completed, and the determination is Y.
Based on the determination of whether or not the engine is in the idling operation state in step S10 in the case of ES, step S11
To S17. That is, when the engine is in the idling operation state, the throttle valve 11 is returned to the closed state (minimum opening) in step S11, the target idle speed is determined in step S12, and a request corresponding to the target idle speed is determined in step S13. Calculate air volume. Further, in step S14, the ISC share is calculated by subtracting the amount of air leaking from the throttle valve and the amount of air passing through the air valve from the required amount of air.
The basic duty of the ISC valve 16 is calculated from the C share. Subsequently, at step S16, the detected engine speed N
e is compared with the target idle speed Ni, and if they are different, feedback control for correcting the duty in accordance with the difference (Ne-Ni) is performed in step S17.

At the time of starting other than the cold starting, fuel injection from the cold start injector 18 is not performed. In addition, during normal operation other than during idling, control of the throttle opening in accordance with the accelerator depression amount at that time is performed. The processing at these times is the same as in the conventional case, and will not be described.

According to the apparatus of the present embodiment as described above, at the time of cold start of the engine, fuel is injected from the cold start injector 18 in order to compensate for the tendency of the combustibility to deteriorate, and the CSI is changed according to the state of the engine. The injection time is determined. In this case, the cold start injector 18 is provided in the main intake passage 8 and the throttle valve 11 is opened to an opening degree corresponding to the CSI injection time, whereby the cold start injector 18 is opened. Start injector 18
Atomization of the fuel injected from the nozzle and mixing with the air are performed favorably. In other words, when the total injection amount of the cold start injector 18 is increased by increasing the CSI injection time, the throttle valve 11 is opened to an opening corresponding to the injection amount, whereby the intake air passing through the main intake passage 8 is opened. And the flow rate is increased. Therefore, the fuel injected from the cold start injector 18 into the main intake passage 8 is mixed with a sufficiently large amount of air, so that atomization and mixing are promoted.

In particular, since the cold start injector 18 is provided at a position close to the outer peripheral portion of the throttle valve when the throttle valve 11 is at the partially open position, the throttle valve 11 is opened to some extent as described above. In this state, the fuel is injected toward the high-speed airflow passing between the outer periphery and the passage wall, and atomization and mixing are further promoted.

Further, at the time of the cold start, the duty of the ISC valve 16 is adjusted in accordance with the throttle opening to control the correction of the intake air amount so as to obtain the required air amount as a whole. Even if the amount of air passing through the valve 11 is increased, the amount of air supplied to the combustion chamber does not increase more than necessary.

After the control at the time of the cold start is performed, the throttle valve 11 is returned to the basic opening as the engine shifts to the idling operation state, and the detected value of the engine speed and the target idle speed are set. By adjusting the intake air flow rate in the ISC passage 16 by feedback control based on the comparison with the rotation speed, the engine operation state smoothly transitions from the cold start control to the idle operation.

[0032]

As described above, according to the first aspect of the present invention, the cold start injector is provided in the main intake passage upstream of the intake passage collecting portion and provided with the throttle valve. The longer the time, the greater the opening of the throttle valve in accordance with the time of fuel injection supply from the cold start injector, so when a relatively large amount of fuel is supplied from the cold start injector during a cold start. The flow rate of the air passing through the main intake passage is increased, and the atomization and mixing of the fuel are sufficiently promoted by the air, so that the combustibility at the time of operation during cold operation can be greatly improved.

Further, when the cold start injector is disposed at a position close to the outer peripheral portion of the throttle valve when the throttle valve is at the partially open position, the cold start injector is disposed between the throttle valve and the passage wall. The effect of promoting the atomization and mixing of the fuel can be enhanced by utilizing the high-speed airflow passing through the space.

According to a third aspect of the present invention, the control of the control of the bypass passage which bypasses the throttle valve is controlled in accordance with the opening degree of the throttle valve at the time of a cold start to perform the correction control of the intake air amount. Then
The intake air amount of the engine can be appropriately adjusted even during the control at the time of the cold start as described above.

Further, after the control at the time of the cold start as described above is completed, the throttle valve is returned to the basic opening, and the intake flow rate of the bypass passage is controlled by the idle speed feedback control. When the adjustment is performed, the operation state can be smoothly shifted from the control at the time of the cold start to the idle state.

[Brief description of the drawings]

FIG. 1 is a schematic view of an entire intake device according to an embodiment of the present invention.

FIG. 2 is a schematic view of a main part of an intake device.

FIG. 3 is a block diagram of a control unit and an input / output system for the control unit.

FIG. 4 is a flowchart of control.

FIG. 5 is an explanatory diagram showing a relationship between a CSI injection time and a throttle opening.

FIG. 6 is an explanatory diagram showing a relationship between a throttle opening and an amount of air passing through a throttle valve.

[Explanation of symbols]

 Reference Signs List 1 engine 3 intake passage 8 main intake passage 11 throttle valve 14 actuator 15 ISC passage 16 ISC valve 18 cold start injector 20 control unit 31 CSI control means 32 T / V control means 33 ISC control means

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-23527 (JP, A) JP-A-60-132044 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/00-41/40

Claims (5)

(57) [Claims] 1. An engine according to claim 1, further comprising a cold start injector for injecting fuel during a cold start, wherein a time for supplying fuel from said cold start injector is adjusted in accordance with a state of the engine during a cold start. In the intake device, the cold start injector is provided in a main intake passage upstream of an intake passage collecting portion and in which a throttle valve is disposed, and a throttle opening adjusting means for adjusting an opening of the throttle valve; An engine provided with throttle valve control means for controlling the throttle opening adjustment means so as to increase the opening of the throttle valve as the time is longer according to the time of fuel injection supply from the start injector. Intake device. 2. The cold start injector according to claim 1,
2. The intake system for an engine according to claim 1, wherein the throttle valve is disposed at a position close to an outer peripheral portion of the throttle valve when the throttle valve is at a partially open position. And a control valve for controlling an intake flow rate of the passage in a bypass passage for bypassing the throttle valve, and controlling the control valve in accordance with an opening degree of the throttle valve during a cold start. 3. The intake system for an engine according to claim 1, further comprising control valve control means for performing correction control of the intake amount. 4. The throttle valve control so that after the fuel injection supply from the cold start injector is completed, the throttle valve is returned to the basic opening and the intake air flow rate in the bypass passage is adjusted by idle speed feedback control. 4. An air intake system for an engine according to claim 3, wherein said control valve control means and said control means are constituted. 5. The intake device for an engine according to claim 1, wherein the throttle opening adjustment means comprises an actuator driven in accordance with an electric signal.