JPH10339247A - Intake device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide stratified combustion by controlling fuel injection time. SOLUTION: This intake device for internal combustion engines is provided with a bulkhead 29 dividing an intake passage 20 into a mixture passage 31 and an air passage 32, a fuel injection valve 25 supplying fuel to the mixture passage 31, an air adjusting valve 23 for throttling the intake passage 20 upper stream of the bulkhead 29 according to operation states, a sub-passage 24 for injecting the air taking a circuitous way around the air adjusting valve 23 to the air passage 32, and a control unit 16 for controlling fuel injection time so that the fuel injected from the fuel injection valve 25 in the early time of an intake process during the opening of an intake valve 19 is sent to a cylinder 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As a method for obtaining stable combustion even with a lean air-fuel mixture, stratification of an air-fuel mixture in which intake swirl is generated in a cylinder to collect fuel near an ignition plug is effective.

As an intake device that generates intake swirl according to operating conditions, for example, there is an intake device disclosed in Japanese Patent Application Laid-Open No. 8-14053.

To explain this, as shown in FIG. 6, an intake passage 2 for introducing intake air into a cylinder 1 has a first intake passage 2A having an opening 2a near the center of the cylinder 1.
And a second intake passage 2B having an opening 2b near the outer periphery of the cylinder 1 through a partition 2C.

The two openings 2 a and 2 b are opened and closed by a single intake valve 4. The intake valve 4 opens and closes at a predetermined timing synchronized with the rotation of the engine.

[0006] A fuel injection nozzle 8 of a carburetor 7 is provided in the first intake path 2A. With the opening of the intake valve 4, the air-fuel mixture is introduced from the first intake passage 2A near the center of the cylinder 1, and the air is introduced from the second intake passage 2B near the outer periphery of the cylinder 1. As a result, in the cylinder 1, an intake swirl is generated in which the two-layered intake air swirls around the center of the cylinder 1 in a fixed swirling direction as indicated by an arrow in the figure, and the mixture of the fuel mixture that collects fuel near the ignition plug 6 is generated. Stratification is achieved.

A first throttle valve 9 is provided in the first intake passage 2A, and a second throttle valve 10 is provided in the second intake passage 2B.
When the load is low, the first throttle valve 9 is closed and the second throttle valve 1 is closed.
0, the intake flow rate passing through the second intake path 2B becomes
The intake swirl is strengthened by increasing the flow rate of the intake air passing through the intake passage 2A.

[0008]

However, in such a conventional intake device for an internal combustion engine, the air taken into the cylinder 1 as the intake valve 4 is opened passes through the carburetor 7. Accordingly, the fuel is sucked from the fuel injection nozzle 8 into the air-fuel mixture passage 31, so that the transport of the fuel to the cylinder 1 is delayed, and it is difficult to collect the fuel near the ignition plug 6. For this reason, there has been a problem that stable stratified combustion is not performed, leading to misfire and deterioration of exhaust emission due to cycle fluctuation.

The present invention has been made in view of the above problems, and has as its object to realize stratified combustion by controlling the fuel injection timing in an intake device for an internal combustion engine.

[0010]

According to a first aspect of the present invention, there is provided an intake system for an internal combustion engine, comprising: a spark plug facing a cylinder; an intake valve for opening and closing an opening of the intake passage to the cylinder in synchronization with engine rotation; Depending on the operating condition, a partition that divides the middle of the passage into a mixture passage that introduces intake air toward the center of the cylinder and an air passage that introduces intake air near the outer periphery of the cylinder, a fuel injection valve that supplies fuel to the mixture passage, An air regulating valve that squeezes the upstream side from the partition of the intake passage, a sub-passage that injects air bypassing the air regulating valve into the air passage, and fuel injected by the fuel injection valve at the beginning of the intake stroke when the intake valve opens. Fuel injection timing control means for controlling the fuel injection timing to be transported to the cylinder.

According to a second aspect of the present invention, there is provided an intake system for an internal combustion engine.
According to the first aspect of the invention, the fuel injection timing control means determines the basic fuel injection timing based on the engine speed and the engine load.

According to a third aspect of the present invention, there is provided an intake device for an internal combustion engine.
In the invention described in claim 1 or 2, the fuel injection timing control means is configured to advance the fuel injection timing as the opening degree of the air adjustment valve decreases.

According to a fourth aspect of the present invention, there is provided an intake device for an internal combustion engine.
In the invention according to any one of claims 1 to 3,
The fuel injection timing control means is configured to advance the fuel injection timing as the flow velocity of the intake air flowing through the mixture passage decreases.

According to a fifth aspect of the present invention, there is provided an intake device for an internal combustion engine.
In the invention according to any one of claims 1 to 4,
The fuel injection timing control means is configured to start injecting fuel before a timing at which the intake valve opens.

According to a sixth aspect of the present invention, there is provided an intake system for an internal combustion engine.
In the invention according to any one of claims 1 to 5,
The fuel injection timing control means is configured to stop injecting fuel after a timing at which the intake valve opens.

[0016]

In the intake system for an internal combustion engine according to the first aspect, fuel injected from the fuel injection valve is mixed with air passing through the air-fuel mixture passage toward the center of the cylinder while opening the intake valve. be introduced. In an operation state in which the flow rate of the intake air flowing from the air passage toward the outer periphery of the cylinder through the air regulating valve is increased, the cylinder has a two-layer intake structure composed of an air-fuel mixture introduced from the air-fuel mixture passage and an airflow introduced from the air passage. Turns.

Since fuel is transported to the cylinder at the beginning of the intake stroke by controlling the fuel injection timing, the fuel is put on the airflow introduced toward the center of the cylinder through the mixture passage, and the fuel is generated in the cylinder. The fuel is collected in the vicinity of the spark plug by the swirling intake air flow, and the mixture is stratified.

In the intake system for an internal combustion engine according to the second aspect of the present invention, the basic fuel injection timing is determined based on the engine speed and the engine load, so that the fuel injection timing corresponding to the fluctuation of the engine speed or the engine load. Is advanced, and the fuel is always transferred to the cylinder at the beginning of the suction stroke.

In the intake system for an internal combustion engine according to the third aspect, the fuel injection timing is advanced as the opening degree of the air adjustment valve decreases, whereby the air adjustment valve is closed and the mixture passage is opened. The fuel injection timing is advanced in response to the decrease of the flowing intake air velocity, and the fuel is always transported to the cylinder at the beginning of the intake stroke even if the opening of the air regulating valve is increased or decreased.

In the intake system for an internal combustion engine according to the fourth aspect, the fuel injection timing is advanced as the flow velocity of the intake air flowing through the air-fuel mixture passage decreases, so that the degree of opening of the air regulating valve changes. Even if the flow velocity of the intake air flowing through the mixture passage increases or decreases, the fuel is always transported to the cylinder at the beginning of the intake stroke.

In the intake system for an internal combustion engine according to the fifth aspect, the fuel is started to be injected before the intake valve is opened, so that the fuel is completely transferred to the cylinder at the beginning of the intake stroke.

In the intake system for an internal combustion engine according to the present invention, the fuel can be transported to the cylinder at an early stage of the intake stroke by ending the fuel injection after the intake valve opens.

[0023]

According to the intake system for an internal combustion engine according to the first aspect of the invention, the fuel is injected at the timing when the fuel is transported to the cylinder at the beginning of the intake stroke, so that the fuel is collected near the spark plug. Gas stratification is achieved, and stable combustion can be obtained even with a lean mixture. As a result, it is possible to prevent misfire or deterioration of exhaust emission due to cycle fluctuation.

According to the intake system for an internal combustion engine according to the second aspect, the fuel is always transported to the cylinder at the beginning of the intake stroke in response to the fluctuation of the engine speed or the engine load.
The mixture is stratified, and the lean burn region can be expanded.

According to the third aspect of the present invention, the fuel is always transported to the cylinder at the beginning of the intake stroke even if the opening of the air regulating valve is increased or decreased. As a result, the lean burn region can be expanded.

According to the intake system for an internal combustion engine of the fourth aspect, even when the intake flow rate increases or decreases, the fuel is always transported to the cylinder at the beginning of the intake stroke, so that the mixture is stratified. The lean burn area can be expanded.

According to the intake system for an internal combustion engine according to the fifth aspect of the invention, the fuel is started to be injected before the intake valve opens, and the fuel is transported to the cylinder at the beginning of the intake stroke. The gas is stratified, and the lean burn region can be expanded.

According to the intake system for an internal combustion engine according to the sixth aspect, fuel injection is completed after the intake valve is opened, and the fuel is transported to the cylinder at an early stage of the intake stroke to form a stratified mixture. Therefore, the lean burn region can be expanded.

[0029]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, one intake port 27 is connected to the cylinder 21, and one exhaust port 28 is connected to face the intake port 27. An ignition plug 26 faces the center of the cylinder 21.

The intake port 27 is partitioned by a partition 29 into a mixture passage 31 and an air passage 32. Mixture passage 31
Communicates near the center of the cylinder 21. The air passage 32 communicates near the outer periphery of the cylinder 21 and is connected in a substantially tangential direction of the cylinder 21 on the plan view of FIG.

The intake port 27 is opened and closed by a single intake valve 19. The intake valve 19 opens and closes at a predetermined timing synchronized with the rotation of the engine.

A fuel injection valve 25 is provided in the mixture passage 31. The control unit 16 includes an intake air amount Qa detected by the air flow meter 15 and the crank angle sensor 1.
The engine speed N detected in Step 4, a cooling water temperature Tw detected by a cooling water temperature sensor (not shown), and the like are input to calculate a fuel injection amount according to the operating state, and the fuel injection amount corresponds to the calculated fuel injection amount. Is output to the fuel injection valve 25,
The fuel injection amount is controlled.

The control unit 15 dilutes the air-fuel ratio of the air-fuel mixture supplied to the cylinder 21 from the stoichiometric air-fuel ratio in the lean combustion region where the engine load is equal to or less than a predetermined value. The air-fuel ratio of the air-fuel mixture supplied to the cylinder 21 is controlled to be close to the stoichiometric air-fuel ratio under operating conditions other than the lean burn region that rises above.

As shown by a two-dot chain line in FIG. 1, the fuel spray injected from the fuel injection valve 25 hits the umbrella back portion 19 a of the intake valve 19. For this reason, the injection hole of the fuel injection valve 25 for injecting fuel is formed such that the umbrella back portion 19a of the intake valve 19 is located in the extension direction.

The fuel injected from the fuel injection valve 25 mixes with the intake air passing through the mixture passage 31 while the cylinder 1
It is led to. With the opening of the intake valve 19, the cylinder 21
Is introduced from an air-fuel mixture passage 31 toward the center of the cylinder 21, and air is introduced from an air passage 32 toward the outer periphery of the cylinder 21. As a result, in the cylinder 21, an intake swirl in which a two-layered intake air composed of an air-fuel mixture and an air flow as shown by an arrow C in the figure turns around the center of the cylinder 21 in a fixed swirling direction. Is caused.

A butterfly type throttle valve 22 is provided upstream of the partition wall 29 of the intake passage 20. The throttle valve 22 is interlocked with an accelerator pedal (not shown), and opens as the driver depresses the accelerator pedal to increase the amount of intake air taken into the cylinder 1.

A butterfly type air regulating valve 23 is interposed in the intake passage 20 at a position downstream of the throttle valve 22 and upstream of the partition wall 29.

The air bypassing the air regulating valve 23 is supplied to the partition 29
There is provided a sub-passage 24 for jetting toward the downstream end. The upstream end of the sub passage 24 is connected between the throttle valve 22 and the air regulating valve 23 of the intake passage 20. The outlet 24 a, which is the downstream end of the sub passage 24, opens to the throat 27 a of the intake port 27.

The air regulating valve 23 is driven to open and close via an actuator 35. The diaphragm type actuator 35 is connected to the throttle valve 22 through a solenoid valve 36.
The suction negative pressure generated on the downstream side of the valve is guided to drive the air regulating valve 23 to the closed position, and the air regulating valve 23 is diluted at atmospheric pressure through the solenoid valve 36 so that the air regulating valve 23 is
The degree of opening is reduced.

The control unit 16 holds the air regulating valve 23 in the closed position in an operating region where the engine load is equal to or less than a predetermined value via an actuator 35, and a part of the intake air flows downstream of the partition wall 29 through the auxiliary passage 24. Spout toward the end. Then, the air regulating valve 23 is held at the fully open position in an operation region where the engine load is higher than a predetermined value, so that most of the intake air does not pass through the sub passage 24.

If the fuel is not transported to the cylinder 21 at the beginning of the intake stroke when the intake valve 19 opens, it is difficult to collect the fuel near the spark plug 6 by the intake swirl generated in the cylinder 21.

In response to this, the control unit 1
6 inputs the engine speed N detected by the crank angle sensor 14 and the intake air amount Qa detected by the air flow meter 15, calculates the fuel injection timing according to the operating state, and opens the intake valve 19 In the early part of the suction stroke
The fuel injection timing is controlled so that the fuel is transported to the fuel injection unit 1.

As the fuel injection timing control means, the fuel injection timing IT is calculated by the following equation.

IT = ITBAS * (1 + ITHOS) (1) where IT: fuel injection timing (injection end timing) ITBAS: basic fuel injection timing calculated based on engine speed ITHOS: according to opening of air regulating valve 23 The fuel injection timing correction coefficient is calculated as follows.

The fuel injection timing IT is determined by the crank angle sensor 1
It has a value corresponding to the crank angle, based on the cylinder discrimination signal from No. 4.

The ITBAS has a table for each engine speed, and is obtained by a table value to be searched and its interpolation. The engine speed is calculated based on a signal from the crank angle sensor 14.

The fuel injection timing correction coefficient ITHOS is shown in FIG.
Is obtained according to the opening degree of the air adjustment valve 23 based on the map shown in FIG. In the map of FIG. 2, the fuel injection timing correction coefficient ITHOS is set so as to gradually decrease as the opening of the air adjustment valve 23 decreases.
As a result, as the opening of the air regulating valve 23 decreases, the fuel injection timing advances in response to the decrease in the flow velocity of the intake air flowing through the mixture passage 31 with the opening of the intake valve 19. The fuel injected from the fuel injection valve 25 is set to be completely transported to the cylinder 21 at the beginning of the suction stroke.

FIG. 3 shows a characteristic in which the fuel injection timing of the fuel injection valve 25 changes according to the engine load. The timing at which fuel is completely transported to the cylinder 21 is set at the beginning of the suction stroke regardless of the engine load, and the fuel injection timing is set to advance as the engine load decreases. The timing at which the fuel starts to reach the cylinder 21 is also set to advance as the engine load decreases.

The fuel injection timing IT is set to coincide with the timing at which the intake valve 19 opens. That is, fuel starts to be injected from the fuel injection valve 25 before the intake valve 19 is opened, and the fuel injection valve 2 is opened after the intake valve 19 is opened.
The fuel injection from 5 is completed.

The operation will be described next.

After the intake valve 19 is opened, intake air (air-fuel mixture) is sucked into the cylinder 21 from the intake passage 20, and the intake air is compressed by the piston and ignited and burned through the ignition plug 26. Exhaust gas is exhausted from the exhaust port 28 as the exhaust valve is opened, and each of these steps is continuously repeated.

The fuel injected from the fuel injection valve 25 is introduced toward the center of the cylinder 21 while mixing with the air passing through the mixture passage 31 as the intake valve 19 opens.
In the cylinder 21, the mixture passage 3
A two-layered intake air composed of an air-fuel mixture introduced from 1 and an airflow introduced from the air passage 32 as shown by an arrow C in the drawing generates an intake swirl that swirls around the center of the cylinder 21 in a fixed swirling direction. .

In the present invention, the fuel is transported to the cylinder 21 at the beginning of the suction stroke by controlling the fuel injection timing, so that the air flow introduced toward the center of the cylinder 21 through the mixture passage 31 is controlled. The fuel is loaded, and the mixture swirling the intake air generated in the cylinder 21 collects the fuel in the vicinity of the ignition plug 26. The mixture is stratified, and stable combustion can be obtained even with a lean mixture. As a result, it is possible to prevent misfire or deterioration of exhaust emission due to cycle fluctuation.

Further, with the configuration in which the fuel injection timing is advanced as the opening degree of the air adjustment valve 23 decreases, the air flow rate of the intake air flowing through the mixture passage 31 decreases due to the closing of the air adjustment valve 23. Correspondingly, the fuel injection timing is advanced, and even when the opening of the air adjustment valve 23 increases or decreases, the fuel is always transported to the cylinder 21 at the beginning of the suction stroke. Therefore, the mixture is stratified regardless of the engine load, and the lean burn region can be expanded.

Next, the embodiment shown in FIG. 4 will be described. The parts corresponding to those in FIG. 1 are denoted by the same reference numerals.

In this embodiment, a flow rate sensor 18 for detecting the flow rate of intake air is provided in the mixture passage 31.

The control unit 16 includes an engine speed N detected by the crank angle sensor 14, an intake air amount Qa detected by the air flow meter 15, a flow rate sensor 18
Calculates the fuel injection timing according to the operation state, and controls the fuel injection timing so that fuel is transported to the cylinder 21 at the beginning of the intake stroke when the intake valve 19 opens. Configuration.

As the fuel injection timing control means, the fuel injection timing IT is calculated by the following equation.

IT = ITBAS * (1 + ITHOS) (2) where IT: fuel injection timing (injection end timing) ITBAS: basic fuel injection timing (constant) ITHOS: calculated according to the intake flow velocity of the mixture passage 31 Fuel injection timing correction coefficient.

The fuel injection timing IT has a map for each of the engine speed N and the basic fuel injection amount Tp (= K × Qa / N, where K is a constant), and is obtained by a searched map value and its interpolation.

The ITBAS has a table for each engine speed N, and is obtained by table values and their interpolation.

The fuel injection timing correction coefficient ITHOS is shown in FIG.
Is obtained in accordance with the intake flow velocity of the mixture passage 31 based on the map shown in FIG. In the map of FIG. 5, the fuel injection timing correction coefficient ITHOS is set so as to gradually decrease as the flow rate of the intake air flowing through the air-fuel mixture passage 31 decreases with the opening of the intake valve 19. Accordingly, the fuel injection timing is advanced in response to the decrease in the flow velocity of the intake air flowing through the mixture passage 31, so that the fuel injected from the fuel injection valve 25 at the beginning of the intake stroke is completely transported to the cylinder 21. Is set to

In this case, the time required for the fuel injected from the fuel injection valve 25 to be transported to the cylinder 21 can be accurately calculated by the structure for directly detecting the intake flow velocity in the mixture passage 31. Even if the flow velocity fluctuates, the fuel injected from the fuel injection valve 25 is controlled so as to be completely transported to the cylinder 21 at a predetermined timing, so that the air-fuel mixture can be stratified and the lean burn region can be expanded. it can.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between an opening degree of an air adjustment valve and a fuel injection timing correction coefficient ITHOS.

FIG. 3 is a characteristic diagram showing a relationship between an engine load and a fuel transport time.

FIG. 4 is a system diagram showing another embodiment.

FIG. 5 is also a flow rate of the air-fuel mixture and a fuel injection timing correction coefficient IT
FIG. 4 is a characteristic diagram showing a relationship between HOS.

FIG. 6 is a schematic plan view showing a conventional example.

[Explanation of symbols]

 Reference Signs List 14 Crank angle sensor 15 Air flow meter 16 Control unit 19 Intake valve 20 Intake passage 21 Cylinder 22 Intake throttle valve 23 Air regulating valve 24 Sub passage 25 Fuel injection valve 26 Spark plug 27 Intake port 28 Exhaust port 31 Mixture passage 32 Air passage

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/34 F02D 41/34 F

Claims (6)

[Claims] A spark plug facing a cylinder; an intake valve for opening and closing an opening of the intake passage to the cylinder in synchronism with engine rotation; and a mixture passage for introducing intake air toward a center of the cylinder in the middle of the intake passage. A partition partitioning into an air passage for introducing intake air near the outer periphery of the cylinder; a fuel injection valve supplying fuel to the mixture passage; an air regulating valve narrowing the upstream side of the intake passage partition in accordance with an operating state; A sub-passage for injecting air bypassing the valve into the air passage, and fuel injection timing control for controlling the fuel injection timing so that the fuel injected by the fuel injection valve is transported to the cylinder at the beginning of the intake stroke when the intake valve opens. And an intake device for an internal combustion engine. 2. An intake system for an internal combustion engine according to claim 1, wherein said fuel injection timing control means determines a basic fuel injection timing based on an engine speed and an engine load. 3. An internal combustion engine according to claim 1, wherein said fuel injection timing control means advances the fuel injection timing as the opening of the air regulating valve decreases. Intake device. 4. The fuel injection timing control means according to claim 1, wherein the fuel injection timing is advanced as the flow rate of intake air flowing through the mixture passage decreases.
An intake device for an internal combustion engine according to any one of the above. 5. The internal combustion engine according to claim 1, wherein said fuel injection timing control means starts injecting fuel before a timing at which an intake valve opens. Intake device. 6. An internal combustion engine according to claim 1, wherein said fuel injection timing control means terminates the injection of fuel after the timing at which the intake valve opens. Intake device.