JPH0634578Y2 - Double intake valve engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to intake control in a so-called double intake valve engine having a plurality of intake valves.

[Conventional technology]

In the trend of higher output, various types of double intake valve engines have been developed. As one of such double intake valve engines, there is an improved helical intake port capable of generating swirl in the combustion chamber. As its name suggests, the helical intake port is formed in a spiral shape, and improves combustion by generating swirl in the combustion chamber. However, it is recognized that when the engine has a high load, the intake resistance increases due to the special shape and the charging efficiency decreases. In order to improve this, a second intake port and a second intake valve are provided, an intake control valve is further provided at this second intake port, and this intake control valve is closed when the load is low. By utilizing this, the intake control valve is opened at the time of high load so that air can be introduced into the combustion chamber from both the first helical intake port and the second port.

On the other hand, in order to improve combustion and improve fuel efficiency, it is necessary to increase the maximum value of the combustible air-fuel ratio, that is, the lean limit of combustion. It is known that it is good to thin the thickness (hereinafter referred to as stratification).

Conventionally, many proposals have been made to stratify a dual intake valve engine to improve combustion and improve fuel efficiency. (See JP-B-47-24041, JP-B-52-16521, JP-B-57-52331, JP-A-52-32406, JP-A-56-96118).

The applicant has improved the above-described known double intake valve engine to achieve combustion of a lean mixture by stratification in a low load range and high output in a high load range, achieving low fuel consumption and low emissions. A more practical dual intake valve engine that can obtain high output has been proposed and a patent has been applied (see Japanese Patent Application No. 60-56126).

The dual intake valve engine according to the above-mentioned applicant's patent application,
A first intake port that is always open to generate swirl in the intake air supplied to the combustion chamber, and an intake control valve that opens only in the high load operating range of the engine and a second intake port that supplies straight intake air to the combustion chamber. An intake port and a third intake port provided with a fuel injection valve are provided, and each of the first, second and third intake ports is burned via the first, second and third intake valves. Each of the chambers is opened, and the valve opening timing of the third intake valve is delayed from the valve opening timing of the first intake valve.

[Problems to be solved by the invention]

In the double intake valve engine having the three intake ports of Japanese Patent Application No. 60-56126, in order to achieve sufficient stratification by supplying a sufficient rich air-fuel mixture from the third intake port,
The third intake valve must be opened for as short a time as possible in the latter half of the intake stroke so that the required amount of rich air-fuel mixture can be supplied. However, in the double intake valve engine of Japanese Patent Application No. 60-56126, since the intake negative pressures of the first and second intake ports and the third intake port equipped with the fuel injection valve are equal, a necessary amount of rich air-fuel mixture is obtained. In order to supply the intake air, the opening time of the third intake valve must be set long, and therefore, the rich air-fuel mixture is intensively supplied during the short period of the latter half of the intake stroke to improve the stratification. Is limited. In addition, the closing timing of the third intake valve is set to the bottom dead center (BDC) of the intake stroke in order to delay the supply of the rich mixture.
Even after that, when the engine load is low, the actual supply of the rich mixture from the third intake port is around the bottom dead center of the intake stroke at the same time as the fresh intake of the first and second intake ports. After that, the rich mixture flows back from the combustion chamber to the third intake port, and there is a limit to efficiently concentrate the rich mixture around the spark plug.

The present invention vigorously supplies a rich air-fuel mixture near the bottom dead center of the intake air from the third intake port when the engine has a low load,
This is intended to further improve the stratification.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention has the following structure.
A first intake port that is always open to generate swirl in the intake air supplied to the combustion chamber, and an intake control valve that opens only in the high load operating range of the engine and a second intake port that supplies straight intake air to the combustion chamber. An intake port and a third intake port provided with a fuel injection valve are provided, and the first, second and third intake ports are respectively connected to the first, second and third intake valves. Open to the combustion chamber via
In the dual intake valve engine in which the opening timing of the third intake valve is delayed from the opening timing of the first intake valve,
And the upstream sides of the second intake ports are both communicated with the first intake passage, the upstream sides of the third intake ports are communicated with the second intake passage, and the first intake passage and the second intake passage are respectively connected. It is characterized in that first and second throttle valves are provided, and the first throttle valve is opened according to the engine load after the second throttle valve is fully opened.

[Action]

The present invention provides a first and a second when the engine load is low.
As for the intake port of the, first, the first throttle valve is slightly opened or fully closed to supply air through a bypass passage or the like to secure a minimum required amount of air flow. The second throttle valve is opened. Therefore, the pressure in the third intake port becomes higher than the pressure in the first and second intake ports, and due to this pressure difference, the rich air-fuel mixture is vigorously supplied into the combustion chamber. Therefore, the opening timing of the third intake valve and the fuel injection timing can be set further in the latter half of the intake stroke, lean combustion is performed close to in-cylinder direct injection type stratified combustion, and the lean limit is expanded. Will be things.

As the engine load increases, the first throttle valve is opened after the second throttle valve is fully opened, and the first throttle valve is fully opened at full load. In this way, when the load is high, the opening degrees of the first and second throttle valves become substantially equal, so the pressures in the first, second and third intake ports also become substantially equal, and the degree of stratification is weakened and increased. The air-fuel mixture with the required output air-fuel ratio is obtained at the time of load, and the output is improved.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, reference numeral 1 denotes a first intake passage or a surge tank, which is provided with a first throttle valve 2, and a downstream side thereof is divided into a first intake port 3 and a second intake port 4. is doing. A second intake passage 5 or a surge tank 5 independent of the first intake passage 1 is provided with a second throttle valve 6 and its downstream side communicates with a third intake port 7. A bypass passage 8 is provided in the first intake passage 1 in the vicinity of the first throttle valve 2, and an adjusting screw 9 is provided in the bypass passage 8 so that the bypass flow rate is appropriately set. .

The first intake port 3 is connected to the combustion chamber 11 via the first intake valve 10.
And is formed in a spiral shape near the first intake valve 10 as is known as a helical port, and the air sucked through this first intake port 3 is indicated by an arrow S in the combustion chamber 11 It creates a swirl inside. The second intake port 4 opens to the combustion chamber 11 via the second intake valve 12 and is straight. An intake control valve 13 is arranged in the second intake port 4 to close the second intake port 4 when the engine speed and load are small, and to close the second intake port 4 when the engine speed and load are large. 4 can be opened. This intake control valve 13
Is opened and closed by an appropriate actuator (not shown), and when the engine is operated at low rotation and low load, this second
The intake port 4 is closed and the second intake port 4 is opened when the engine is operated at high rotation and high load. The actuator has, for example, a diaphragm chamber partitioned by a diaphragm into an atmospheric pressure chamber and a variable pressure chamber. A negative pressure control type actuator that controls opening and closing is used. This actuator is controlled by an electronic control unit (ECU) not shown.
The third intake port 7 is connected to the combustion chamber 11 via the third intake valve 14.
It is open to. The third intake port 7 is located between the ports 3 and 4, and has a relatively small passage cross-sectional area. Therefore, the third intake valve 14 is also smaller than the other intake valves 10 and 12.

A fuel injection valve 15 is arranged in the third intake port 7,
The fuel injection valve 15 is controlled by the ECU.

As shown in FIG. 1, the positional relationship among the first, second and third intake valves 10, 12 and 14 is such that the third intake valve 14 with respect to the center of the combustion chamber 11 in plan view The first and second intake valves 10 and 12 are arranged so as to be located outside a straight line connecting the centers of the intake valves 10 and 12. 16 is a spark plug, and intake valves 10, 12,
It is arranged approximately in the center of the cylinder surrounded by 14 and the two exhaust valves 17, 18.

A throttle opening sensor and a throttle actuator (not shown) are attached to the first and second throttle valves 2 and 6, respectively. The throttle opening sensor and the throttle actuator are connected to an ECU (not shown), and a second throttle A detection signal of the opening degree of the valve 6 is sent to the ECU, and the ECU operates the throttle actuator of the first throttle valve 2 based on this detection signal to control the opening degree of the first throttle valve 2. There is.

The first, second and third intake valves 10, 12, 14 and the fuel injection valve 15
The operation timing of is shown in FIG. As shown in the operation curve B, the opening timing of the third intake valve 14 is later than that of the first and second intake valves 10 and 12 whose operation curve is shown by A, and is delayed from near the center of the intake stroke. The first intake valve 10 and the second intake valve 12 are closed at substantially the same time. That is, the opening timing of the third intake valve of the above-mentioned Japanese Patent Application No. 60-56126, whose operation curve is shown by B'in the figure, was near the center of the intake stroke, but later than this. Open the valve.

Further, the fuel injection valve 15 is set so that the injection end timing is near the bottom dead center of the intake stroke, as shown by F in FIG.

FIG. 3 is a diagram showing the relationship between the opening degrees of the throttle valve 2 and the second throttle valve 6 shown in FIG. 1, and when the engine load is low, the second throttle valve 6 should first be operated according to the increase in load. The valves are sequentially opened, and after the valves are fully opened, the first throttle valve 2 is opened almost in proportion to the engine load. And when the engine is fully loaded, the first and second throttle valves
Both 2 and 6 are fully open.

Further, in the case where the swirl generated in the first intake port 3 is insufficient due to the intake flow rate from the bypass passage 8 when the engine load is low, the second throttle valve 6 is fully opened as shown in FIG. The first throttle valve 2 is slightly opened up to the area of the load G, and the first throttle valve 2 is substantially opened according to the load in the area of the load G or more.

FIG. 5 is a diagram showing the relationship between the fuel injection end timing E and the engine load. As shown in FIG. 5, the injection end timing E is gradually advanced as the load increases at high load, and stratification is performed. Make more detailed control to weaken the degree of.

The operation of this embodiment will be described below.

When the engine load is low, the first throttle valve 2
Is closed so that only the air passing through the bypass passage 8 is supplied to the first intake port 3.

As shown in FIG. 2, firstly, the first and second intake valves 10 and
12 opens before the top dead center of the intake stroke. Since the second intake port 4 is closed by the intake control valve 13, the combustion chamber 11
Air is sucked in from the first intake valve 10 to generate a stable swirl S. The second throttle valve 6 operates so as to increase the opening degree as the load increases, as shown in FIGS.

Following the opening of the first and second intake valves 10 and 12, the third intake valve 14 is opened later than near the center of the intake stroke. Third
A signal from the ECU is applied to the intake port 7 of the fuel injection valve 1
Fuel is injected from 5 at an injection timing such that the injection end timing is near the bottom dead center of the intake stroke.

As described above, since the first throttle valve 2 is closed and the second throttle valve 6 is open, the third intake port 7
The pressure inside becomes higher than the pressure inside the first intake port 3,
Due to this pressure difference, the fuel injected into the third intake port 7 vigorously flows into the combustion chamber 11 in a short time. Therefore, the opening timing of the third intake valve 14 and the fuel injection timing can be set later in the latter half of the intake stroke, and fuel can be supplied into the combustion chamber in a short time in the latter half of the intake stroke. As a result, the rich air-fuel mixture drifts around the spark plug 16, and good stratification close to that of a cylinder direct injection type stratified combustion engine is obtained.

In the engine in which the intake air in the first intake port 3 is insufficient to obtain the required swirl,
As shown in the figure, the first throttle valve 2 is slightly opened in advance to the region of the load G at which the second throttle valve 6 is fully opened, and intake air is replenished. After the throttle valve 6 is fully opened, the first throttle valve 2 is controlled so as to be opened almost in proportion to the load.

On the other hand, when the engine is under high load, it is necessary to change the air-fuel ratio from the stoichiometric air-fuel ratio to the output air-fuel ratio to improve the output. At this high load, as shown in FIG. 3 and FIG.
The throttle valve 2 of is opened according to the load, and the first
And the openings of the second throttle valves 2 and 6 are almost equal,
Further, the second intake port 4 is also opened by opening the intake control valve 13, so that the pressures in the first, second and third intake ports 3, 4, 7 become substantially equal, and the first, second , The third intake valve 10,12,
A large amount of fresh air can be sucked into the combustion chamber 11 from 14, the degree of stratification is weakened, and the air-fuel mixture becomes appropriate to obtain high output.

At this time, as shown in FIG. 5, the fuel injection end timing E is gradually advanced as the load increases, and the degree of stratification is controlled more finely according to the load.

[Effect of device]

As described above, in the present invention, in the low load region of the engine, the air-fuel mixture is rich around the spark plug and lean on the piston side, so-called stratification is obtained in a good and stable state. It becomes possible to achieve low fuel consumption and low emissions.

Particularly, in the present invention, at the time of low load of the engine, the pressure in the third intake port for supplying fuel is made larger than the pressure in the first intake port for generating swirl. As a result, the injected fuel flows into the combustion chamber at one time, and therefore the fuel injection timing and the opening timing of the third intake valve can be significantly delayed, so that the rich mixture concentrates in the combustion chamber for a short time. As supplied, better stratification will be achieved.

Further, in the high load region of the engine, good shaft torque and output can be effectively obtained.

In this way, it is possible to provide a practical dual intake valve engine in which the initial combustion state and high output are obtained in the entire operating range from the low load range to the high load range.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of the present invention, FIG. 2 is a diagram showing the operation timing and lift of each intake valve and the injection timing of a fuel injection valve of the above embodiment, and FIG. First in the example
And a diagram showing the relationship between the opening of the second throttle valve and the engine load, and FIG. 4 is a diagram similar to FIG. 3 in which the opening of the first throttle valve at low load is partially changed. 5 is a diagram showing the relationship between the end timing of fuel injection and the engine load in the above embodiment. 1 ... 1st intake passage, 2 ... 1st throttle valve, 3 ... 1st intake port, 4 ... 2nd intake port, 5 ... 2nd intake passage, 6 ... 2nd throttle valve, 7 ... ... third intake port, 8 ... bypass passage, 10 ... first intake valve, 11 ... combustion chamber, 12 ... second intake valve, 13 ... intake control valve, 14 ... third intake valve, 15 …… Fuel injection valve, 16 …… Spark plug.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number of the agency FI technical display area F02D 41/02 310 G 8011-3G F02M 69/00 360 C 7825-3G

Claims (1)

[Scope of utility model registration request] 1. A first intake port that is normally open to generate swirl in the intake air supplied to the combustion chamber, an intake control valve that opens only in a high load region of the engine, and supplies straight intake air to the combustion chamber. A second intake port to
A third intake port provided with a fuel injection valve and respective intake ports are provided, and these first, second, and third intake ports are provided,
In a double intake valve engine in which the opening timing of the third intake valve is delayed from the opening timing of the first intake valve by respectively opening to the combustion chamber through the first, second and third intake valves , The upstream sides of the first and second intake ports are both communicated with the first intake passage, and the upstream side of the third intake port is the second side.
The first and second throttle valves are provided in the first and second intake passages, respectively.
The double intake valve engine according to claim 1, wherein the throttle valve is opened according to the engine load after the second throttle valve is fully opened.