JPH0634581Y2 - 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 implies, 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).

The applicant has improved the double intake valve engine described above and is capable of achieving both lean fuel mixture combustion by stratification in the low load range and high output in the high load range, achieving low fuel consumption, low emissions, and high emissions. We proposed a more practical dual intake valve engine that can obtain output and applied for a patent (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 opening timing of the third intake valve is delayed from the opening timing of the first intake valve.

However, in the double intake valve engine of the above-mentioned Japanese Patent Application No. 60-56126, which has three intake ports, in order to achieve a sufficient stratification by supplying a sufficient rich air-fuel mixture from the third intake port, It is necessary for the swirl to be sufficiently strong and stable and for the rich mixture to be slowly and slowly supplied into the combustion chamber in order to weaken the penetration force. For that purpose, the third intake valve must have a sufficient opening period and the air flow passing therethrough must be sufficiently slow. However, in the double intake valve engine of the above-mentioned Japanese Patent Application No. 60-56126, since the intake pressures of the first and second intake ports and the third intake port equipped with the fuel injection valve are equal, they pass through the third intake valve. The flow of air becomes relatively fast, so if the third intake valve is opened too early, the swirl flow generated by the first intake port will be destroyed and the mixture of rich air and air will be promoted. The original purpose of achieving stratification by concentrating and supplying air in the short term of the latter half of the intake stroke will not be achieved. Therefore, the opening timing of the third intake valve is restricted, and in the double intake valve engine of Japanese Patent Application No. 60-56126, the third intake valve is actually opened from around the center of the intake stroke. However, there is a limit in efficiently concentrating a rich air-fuel mixture around the spark plug to achieve good stratification.

Therefore, in order to solve the above-mentioned problems, the applicant of the present invention, in a dual intake valve engine having three intake ports as described above, communicates the upstream sides of the first and second intake ports together with the first intake passage. The upstream side of the third intake port is communicated with the second intake passage, and the first and second intake passages are connected to the first intake passage.
And a second throttle valve are provided respectively, and a dual intake valve engine is proposed in which the opening of the first throttle valve is set larger than the opening of the second throttle valve when the engine has a low load (actual application). See Sho 61-104899).

[Problems to be solved by the invention]

In the dual intake valve engine of Japanese Utility Model Application No. 61-104899, the second throttle valve is open to some extent even when the engine load is low, and the third intake port and the third intake valve are used to Since a considerable amount of fresh air is sucked in, the swirl generated by the helical first intake port is weakened and the rich mixture flowing in from the third intake port has a considerable penetration force. Therefore, there is a problem that a strong and stable swirl and a rich mixture having a weak penetration force are not necessarily sufficiently obtained in order to obtain good stratification at a low load as described above.

[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. 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 by opening each of them to the combustion chamber via the upstream side of the first and second intake ports. Both sides are communicated with the first intake passage, the upstream side of the third intake port is communicated with the second intake passage, and first and second throttle valves are provided in the first and second intake passages. And the second intake passage is provided with the second A small flow rate bypass passage for bypassing the throttle valve is provided, and the second throttle valve is configured to start opening when the first throttle valve is fully opened.

[Action]

The present invention performs load control by closing the intake control valve in the second intake port, fully closing the second throttle valve, and opening only the first throttle valve in the low load region of the engine. The intake control valve is opened from the high load range where the first throttle valve is fully opened, and the second throttle valve starts to open. When the load is full, both the first and second throttle valves are fully opened. However, even when the second throttle valve is fully closed in the low load range, a small amount of fresh air flows through the third intake port through the bypass passage, and the fuel injected from the fuel injection valve is injected into the third intake port. The minimum intake required to smoothly flow into the combustion chamber is secured through the intake valve.

In this way, in the low load region of the engine, the pressure in the first intake port becomes higher than the pressure in the third intake port, and a powerful and stable swirl is obtained, and a penetration force from the third intake port is obtained. A weak rich mixture flows in, good stratification is achieved, and the lean limit of combustion is expanded.

〔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. 5 is a second independent of the first intake passage 1
Of the intake passage or the surge tank, the second throttle valve 6 is provided, and the downstream side thereof communicates with the third intake port 7.

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, and closes the second intake port 4 when the engine speed load is small, and closes the second intake port 4 when the engine speed load is large. It can be opened. This intake control valve 13 is opened and closed by an appropriate actuator (not shown),
When the engine is operated at low speed and low load, the second intake port 4 is closed, and when the engine is operated at high speed and high load, the second intake port 4 is opened. The actuator has, for example, a diaphragm chamber partitioned by a diaphragm into an atmospheric pressure chamber and a variable pressure chamber, and a negative pressure or atmospheric pressure is introduced into the variable pressure chamber in accordance with the operating state of the engine to introduce the intake control valve 13 into the variable pressure chamber. A negative pressure control type actuator that controls opening and closing is used. Then, this actuator is controlled by an electronic control unit (ECU) not shown. The third intake port 7 opens into the combustion chamber 11 via the third intake valve 14. 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, and 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 in the center of the cylinder surrounded by 14 and 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. These throttle opening sensor and throttle actuator are connected to an ECU (not shown), In the low load region, the second throttle valve 6 is fully closed, and only the first throttle valve 2 gradually increases its opening degree as the engine load increases, and in the high load region of the engine, the first throttle valve 2 is closed. The second throttle valve 6 starts to open when is fully opened, and is controlled to be fully opened at full load.

However, when the second throttle valve 6 is fully closed, intake air does not flow into the third intake port 7, and the injected fuel is insufficiently supplied. A bypass passage 20 that bypasses the second throttle valve 6 is provided, and the minimum amount of fuel required for the fuel injected from the fuel injection valve 15 to smoothly flow into the combustion chamber 11 through the third intake valve 14 is provided. Keep fresh air flowing. A flow rate adjusting screw 19 is provided in the bypass passage 20.

The operation timings of the first, second and third intake valves 10, 12 and 14 and the fuel injection valve 15 are shown in FIG.

As shown by the operation curve A, the first and second intake valves 10 and 12 open a little before the top dead center of the intake stroke and close a little after the bottom dead center of the intake stroke. As shown by the operation curve B, the third intake valve 14 opens in the first half of the intake stroke and closes at substantially the same time as the first and second intake valves 10 and 12. In the figure, B'shows the operation curve of the third intake valve in the double intake valve engine of the above-mentioned Japanese Patent Application No. 60-56126, and as is apparent from this, the third intake valve 14 of this embodiment It can be seen that the valve opening time is significantly earlier than the conventional one.

As shown by F in the figure, the valve opening and the fuel injection valve 15 set the injection start time D to the engine speed and load so that the injection end timing E falls within the opening period of the third intake valve 14. The fuel injection end timing is controlled to a predetermined crank angle during the opening period of the third intake valve regardless of the engine speed and load.

FIG. 3 is a diagram showing the relationship between the opening of each of the first and second throttle valves 2 and 6 and the load of the engine. In this embodiment, as shown in FIG. 2 increases as the engine load increases, and when the load G is reached, the valve is fully opened. On the other hand, the second throttle valve 6 is in the fully closed state in the low load range where the engine load is G or less, and the first throttle valve 2 starts to open from the high load range of G or more where it is fully opened and the load of The opening is increased according to the increase so that it is fully opened when the engine is fully loaded.

The operation of this embodiment will be described below.

At low engine load, as shown in FIG.
First, the first and second intake valves 10 and 12 are opened near the top dead center of the intake stroke, and the second intake port 4 is closed by the intake control valve 13. The air is sucked only from the intake valve 10 to generate the swirl S. Then, the third intake valve 14 is opened in the first half of the intake stroke. Fuel is injected from the fuel injection valve 15 to the third intake port 7 by a signal from the ECU so that the injection end timing falls within the opening period of the third intake valve 14.

At this time, since the second throttle 6 is fully closed and only the first throttle valve 2 increases or decreases its opening according to the magnitude of the load, the pressure in the first intake port 3 is equal to the third intake port. Since it is higher than the pressure in 7 and is not affected by the pressure in the third intake port 7, a strong and stable swirl can be obtained. Further, the pressure in the third intake port 7 is low in the third intake port 7 due to the closing of the second throttle valve 6, and the fuel injected from the fuel injection valve 15 has a weak penetration force.
It mixes with a small amount of fresh air flowing through 20 and is guided by this to slowly and smoothly flow into the combustion chamber 11.

In this way, a stable swirl S is obtained from the first intake port 3 and the flow of fuel supplied from the third intake port is weak, so the rich mixture does not destroy the swirl and the second half of the intake stroke occurs. Then, it flows into the combustion chamber 11 and drifts around the spark plug 16, and a stratified state is obtained. Since this stratified state is stably maintained up to the compression top dead center by the swirl S, a rich air-fuel mixture is drifting in the vicinity of the spark plug 16 at the time of ignition, the air-fuel ratio of the whole is thin, and a large amount of EGP gas is generated. Even when it is introduced into the combustion chamber 11, stable ignition and flame propagation are achieved.

On the other hand, when the engine load is high, as shown in FIG.
The first throttle valve 2 is fully opened by the load G, and the second throttle valve 6 starts to open from here. Then, as the load further increases, its opening degree increases, and it is fully opened at full load. In addition, the intake control valve in the second intake port 4
13 also opens. Therefore, a large amount of air is supplied from the first, second and third intake ports, and a high output is obtained in combination with the increase in fuel injection.

In particular, since the swirl S generated by the first intake port is strong and stable as described above, the structure of the first intake port itself does not need to have a strong helical shape, and therefore the ventilation resistance is small and high. Since it can be used as a port for the flow rate coefficient, and the opening timing of the third intake valve 14 can be made earlier than the conventional one, the charging efficiency at the time of high engine load is improved and the desired high output is obtained. be able to.

If the intake control valve 13 in the second intake port 4 is controlled so as to be fully closed at low engine speed, the above-described operation is effective only at low engine speed and low load. Also, when the engine is running at high speed, the intake control valve 13 is opened to suck a large amount of fresh air to obtain a high output, but in this case the above-mentioned opening control of the throttle valves 2 and 6 is unnecessary. Therefore, the first and second throttle valves 2 and 6 may be switched to open simultaneously.

[Effect of device]

Since the present invention has the above-described structure and operation, 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 good and stable. As a result, a large amount of EGR combustion becomes possible, and low fuel consumption and low emissions can be achieved.

Particularly in the present invention, when the engine load is low, the pressure in the first intake port is not affected by the pressure in the third intake port, so that the swirl obtained in the first intake port becomes stable. At the same time, the fuel supplied from the third intake port becomes a flow having a weak penetration force, so that this swirl is not destroyed and good stratification can be achieved.

Further, when the engine is under high load, the stable swirl is obtained as described above, so that the first intake port does not need to have a strong helical shape, so that the flow rate coefficient can be made high. This, combined with the fact that the opening timing of the third intake valve can be advanced, improves the charging efficiency, and a high output corresponding to a high load can be obtained.

In this way, it is possible to provide a practical dual intake valve engine that can obtain the desired combustion state and high output 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 operation timing and lift of each intake valve, and injection timing of a fuel injection valve, and FIG. 3 is first and second throttles. It is a diagram which shows the relationship between the opening degree of a valve and engine load. 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, 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, 19 …… Screw for adjusting flow rate, 20 …… Bypass passage.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location F02M 23/02 69/00 360 C 7825-3G

Claims (1)

[Scope of utility model registration request] Claim: What is claimed is: 1. A first intake port which is normally open to generate swirl in the intake air supplied to the combustion chamber, and an intake control valve which is opened only in a high load operating range of the engine, and straight intake air is provided in the combustion chamber. A second intake port for supplying and a third intake port provided with a fuel injection valve,
These first, second and third intake ports are respectively opened to the combustion chamber via the first, second and third intake valves, and the opening timing of the third intake valve is set to the first In a double intake valve engine delayed from the opening timing of the intake valve, both the upstream sides of the first and second intake ports are communicated with the first intake passage, and the upstream side of the third intake port is connected to the second intake port. A first throttle valve is provided in the first intake passage, a second throttle valve is provided in the second intake passage, and the second throttle valve is provided in the second intake passage. A double intake valve engine, wherein a small flow rate bypass passage for bypassing the valve is provided, and the second throttle valve is configured to start opening when the first throttle valve is fully opened.