JPH03156111A - Inlet system for multiple-valve engine - Google Patents

Abstract

PURPOSE:To improve inlet flow rate to reduce the amount of fuel deposited on the wall by forming the inclination of the umbrella of an inlet valve in an inlet port with a fuel injector, greater than the inclination of the umbrellas of inlet valves in other inlet ports. CONSTITUTION:An inlet passage 14 provided with a fuel injection valve 21 is made to open near the center of an engine combustion chamber 5. The inclination theta2 of a slope F extended from the steam 9b to the umbrella 9a peripheral edge of an inlet valve 9 provided on the opening is formed greater than the inclination theta1 of inlet valves 7, 8 in inlet passages 12, 13. In this way, inlet air in the inlet passage 14 during the opening of the inlet valve 9 is specially faster in flow rate and flows into the combustion chamber 5 while effectively scratching off liquid drop fuel deposited on the umbrella 9a peripheral edge, therefore to reduce a large amount of injection fuel deposited on the wall.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to the structure of an intake system for a multi-valve engine having several intake valves per cylinder.

(Prior Art) Recently, the intake air filling efficiency has been improved by adopting a multi-valve structure, and some of the plurality of intake ports corresponding to the plurality of intake valves have been equipped with seals.

BACKGROUND ART Various engine intake systems have been proposed in which a filter valve is provided and the substantial intake passage area is changed depending on the engine load condition.

As one of them, for example, Utility Model No. 61-20492
There is one shown in Publication No. 2. The engine intake system disclosed in the publication includes three sets of intake ports: a pair of side ports and a center port provided between the pair of side ports. A set of intake valves is provided. For example, a shutter valve is installed on one side of the pair of side ports, making it possible to control the amount of intake air according to the load condition, while the other side port is formed in a helical shape as a swirl generation port. A fuel injector is also installed at the center port. The center boat in which the fuel injector is provided opens at the center of the top of the combustion chamber, and an intake valve is installed in the opening.

In general, the leaner the air-fuel ratio A/F of the air-fuel mixture supplied to the 7th ring of the engine, the more the fuel consumption rate can be improved. Therefore, in order to improve at least the fuel efficiency rate, It is desirable to make the air-fuel ratio A/F of the air-fuel mixture supplied into the 7th ring of the engine as lean as possible. However, when such a lean mixture is used, there is a problem that not only does the ignitability deteriorate, but even if there is a green flame, the flame propagation is slow and good combustion conditions cannot be obtained.

Therefore, in order to solve this problem, for example, the intake passage is installed in the combustion chamber in a tangential (or helical) manner to the inner wall surface, and the fuel injection valves Q and J are arranged in the same intake passage. 2. Description of the Related Art Engines have long been known in which fuel injection from a fuel injection valve is stopped slightly before the intake valve closes.

In an engine with this type of structure, only air is supplied into the combustion chamber during the first half of the intake stroke during partial load operation, and injected fuel is supplied into the combustion chamber during the second half of the intake stroke, so a rich mixture is present at the top of the combustion chamber. At the same time, a lean air-fuel mixture layer is formed below the combustion chamber, and the air-fuel mixture in the combustion chamber is stratified. As a result, a rich air-fuel mixture gathers around the spark plug, improving ignition performance, and the air flowing in at high velocity from the tangentially opened intake passage creates a swirl inside the combustion chamber. Since the ignition flame is generated, the ignition flame can be rapidly propagated into the combustion chamber, resulting in good combustion conditions.

By the way, when the air-fuel mixture in the combustion chamber is stratified in this way, if the air-fuel ratio of the stratified air-fuel mixture is kept constant, combustibility can be improved by increasing the degree of stratification. For example, the air-fuel ratio of the entire stratified mixture is 25, and the air-fuel ratio of the rich mixture is 20. Comparing the case where the air-fuel ratio of a lean mixture is 30 and the case where the air-fuel ratio of a rich mixture is 15 and the air-fuel ratio of a lean mixture is 35, the latter case is better than the former case. Better flammability can be obtained. In other words, the air-fuel ratio of the rich mixture is 2.
Even in the case of 0, it is possible to ignite with the spark plug, but the flame caused by the combustion of the rich mixture is still weak, and as a result, it takes time to burn the lean mixture. It is difficult to obtain good combustion conditions.

On the other hand, when the air-fuel ratio of the rich mixture is around 15, the flame due to combustion of the rich mixture is strong, and therefore, in this case, even if the lean mixture is leaner, the same lean mixture is combusted. The time required for combustion is shortened, and a sufficiently good combustion condition can be obtained. Additionally, fuel efficiency is improved. In order to obtain such a good combustion state, it is necessary to increase the degree of stratification of the air-fuel mixture in the combustion chamber as much as possible.

However, in the above-mentioned well-known engine, the fuel injector is installed in the intake boat itself for forming the swirl flow, so the injected fuel flows into the combustion chamber at a high velocity together with the intake air flow. It tends to spread throughout the combustion chamber, and therefore, although the air-fuel mixture is stratified to some extent, the problem remains that the degree of stratification is not sufficient.

In order to solve this remaining problem, for example, the first intake valve is provided with two intake valves, a first intake valve and a second intake valve, and the first intake valve is connected to the inside of the combustion chamber via the first intake valve. The intake passage is formed in a helical shape, and an intake control valve that opens during high-load operation is provided in the second intake passage connected to the combustion chamber via the intake valve of the other cylinder 2. A fuel injection valve in which a fuel injection valve is disposed within the second intake passage has already been proposed. Furthermore, in order to improve the intake air filling efficiency particularly during high-load operation, a device further equipped with a third intake valve has been proposed in this regard. In the structure of these internal combustion engines, the intake control valve is kept closed during partial load operation, so when the second intake valve opens during the intake stroke, the air in the second intake passage downstream of the intake control valve opens. The pressure of the air-fuel mixture in the combustion chamber immediately decreases to The fuel injected into the second intake passage flows into the combustion chamber at a slow speed.Therefore, the injected fuel within the combustion chamber does not spread much within the combustion chamber, and as a result, the degree of stratification also decreases. It can be made higher.

However, in order to further increase the degree of stratification in these engines, if the second intake valve is opened in the latter half of the intake stroke, the fuel injected into the second intake passage will be injected slowly. Because all the injected fuel cannot flow into the combustion chamber because the fuel only flows into the combustion chamber at a certain speed, the injected fuel that could not flow into the combustion chamber suddenly enters the combustion chamber at the moment when the second intake valve opens in the next intake stroke. will begin to flow into the country.

However, at the moment when the second intake valve opens, the injected fuel that could not enter in the previous intake stroke flows into the combustion chamber, and this injected fuel collects in the center of the combustion chamber. The problem arises that good stratification cannot be obtained. On the other hand, if the opening timing of the second intake valve is advanced in order to supply all the injected fuel into the combustion chamber during the intake stroke, the injected fuel in the second intake passage will be supplied into the combustion chamber from the early stage of the intake stroke. As a result, it becomes difficult to obtain good stratification. That is, when trying to achieve stratification by closing the intake control valve provided in the second intake passage, no matter how the opening timing of the second intake valve is set, it will not work properly. It will not be possible to obtain stratification.

In order to solve these problems, the second intake passage is kept open at all times and the timing of completion of fuel injection is appropriately controlled to increase the degree of stratification and thereby ensure good combustion. It is possible to do so.

However, if such a configuration is adopted, since the second intake valve for supplying a rich air-fuel mixture is disposed around the top of the combustion chamber, the rich mixture flowing from the second intake valve is A new problem arises in that the original swirl is not only weakened by the mixture flow, but also the rich mixture is diffused toward the outer circumference by the swirl, making it impossible to sufficiently increase the degree of stratification. It's coming.

The prior art mentioned above (Utility Model Application Publication No. 61-204922
The invention described in the above-mentioned publication was invented under the above technical background, and in the configuration of the invention, the third intake valve on the fuel supply boat side is arranged at the center of the top of the combustion chamber. This makes it possible to prevent the air-fuel mixture supplied from the third intake valve from diffusing in the outer circumferential direction, thereby increasing the degree of stratification. The valve is opened between the center of the intake stroke and the beginning of the compression stroke, and fuel flows in the vertical direction at a relatively low flow rate, so the swirling flow is not weakened too much depending on the supplied air-fuel mixture, so it is powerful. A swirling flow can be maintained until the end of the compression stroke. As a result, it is possible to obtain a good combustion state even when using a lean mixture with an average air-fuel ratio of 25 to 30.

Therefore, according to the configuration of the prior art, substantially all of the above-mentioned problems can be solved.

(Problem to be solved by the invention) However, in the configuration of the prior art described above, the second
The shatter valve provided in the intake passage of the engine is closed. As a result, intake air is supplied from the remaining two intake passages, the first and third, but the cross-sectional area of these two intake passages is large, and since the load is light, the absolute amount of intake air is supplied. Since there is a small amount of intake air, the flow rate of intake air supplied from the third intake passage, which is the center port, is originally low.

Therefore, if the fuel injected by the fuel injector is not smoothly supplied into the combustion chamber and tends to adhere to the wall of the third intake passage, the valve umbrella angle of the third intake valve in the same intake passage may become flat. As a result, droplets were attached to the periphery of the port opening in the intake passage.
There is a problem that it becomes a source of C generation. Also, as a result,
Problems such as the difficulty in creating a rich air-fuel mixture near the spark plug remain unsolved.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned unresolved problems, and includes a plurality of intake valves and a plurality of intake ports corresponding to each cylinder. In the intake multi-valve engine, the intake port having the fuel injector is opened near the center of the throat into the seventh ring of the engine, and the intake port is provided with a fuel injector in any one of the plurality of intake ports. This is characterized in that the angle of the sloped surface from the stem portion of the intake valve to the peripheral edge of the umbrella portion is set larger than the angle of the sloped surface of the intake valves of other intake boats.

(Function) In the configuration of the intake device of the multi-valve engine of the above claimed invention,
-1- Similar to the prior art described above, the center port where the fuel injector is installed is opened near the center of the engine combustion chamber, and in addition, the inclination extends from the stem of the intake valve provided in the opening to the periphery of the umbrella part. The angle of inclination of the surface is larger than the angle of inclination of the intake valve of the intake port of the pond.

Therefore, when the intake valve is opened, the intake flow velocity at the center port becomes particularly high, effectively scraping off fuel droplets adhering to the periphery of the umbrella part and flowing into the combustion chamber, causing the injected fuel to adhere to the wall surface. The amount can be greatly reduced. This effectively enriches the air-fuel mixture near the spark plug in the center of the combustion chamber and promotes stratification.

(Effects of the Invention) Therefore, according to the multi-valve engine intake system of the present invention, the intake flow velocity only near the opening of the center port equipped with the fuel injector is effectively increased, and the amount of fuel adhering to the wall surface is reduced. As a result, the amount of HC generated also decreases, which can contribute to improving exhaust emissions.

(Embodiment) FIGS. 1 to 3 show the configuration of an intake system for a multi-valve engine according to an embodiment of the present invention.

First, the structure will be explained with reference to FIGS. 1 to 3. Reference numeral 1 indicates the engine body, 2 indicates the cylinder block,
3 is a piston that reciprocates within the same cylinder block 2;
is a cylinder head fixed on the cylinder block 2, 5 is an engine combustion chamber formed between the piston 3 and the cylinder head 4, and 6 is located approximately at the center of the top of the engine combustion chamber 5. The ignition plugs are shown respectively. On the inner wall surface of the cylinder head 4, there are three intake valves consisting of a first intake valve 7, a second intake valve 8, and a third intake valve 9, and a first exhaust valve 10 and a second intake valve. Two exhaust valves each consisting of an exhaust valve 11 are arranged.

The first intake valve 7 and the second intake valve 8 have approximately the same valve diameter, and the third intake valve 9 has a smaller valve diameter than the first intake valve 7 and the second intake valve 8. It is formed as follows. This third
The intake valve 9 is disposed at the center of the top of the engine combustion chamber 5, and the spark plug 6 is disposed near the third intake valve 9. Inside the cylinder head 4,
Three intake passages consisting of a first intake passage 12, a second intake passage 13, and a third intake passage 14, and the exhaust valve 10.
Exhaust passages 15A and 15B connected to the engine combustion chamber 5 via 11 are formed, respectively. First intake passage 12, second intake passage 13, and third intake passage 14
As shown, they are separated from each other by a pair of thin partition walls 16 and 17 and extend substantially parallel to each other in the cylinder head 4 on the intake upstream side. Further, the third intake passage 14 is formed to have a smaller cross section than the first intake passage 12 and the second intake passage 13 within a range that can ensure an appropriate amount of intake air and fuel supply according to each operating region, It is constructed so that an appropriate intake flow rate can be obtained especially when the load is light. First intake passage 12, second intake passage 13, and third intake passage 1
4 are connected to the same intake branch pipe 18 as shown in FIG. The first intake passage 12 is connected to the engine combustion chamber 5 via the first intake valve 7, and the first intake passage 12 is designed to generate a swirl in the engine combustion chamber 5. It is formed into a helical shape. The second intake passage 13 is connected to the engine combustion chamber 5 via the second intake valve 8, and is formed as a straight port extending substantially straight. An intake control valve 19 is disposed at the inlet of the second intake passage 13, and a valve shaft 20 of the intake control valve 19 is connected to the first intake passage 12, the second intake passage I3, and the third intake passage 14. The inside extends through each award to the outside. Although not shown, the valve shaft 20 is connected to a drive shaft of a negative pressure actuator that operates in accordance with the intake negative pressure of the engine.
Valve closing is controlled. Furthermore, the third intake passage 14 is connected to the engine combustion chamber 5 via the third intake valve 9 described in . This third intake passage 14 is formed as a straight boat that extends straight. A fuel injection valve (fuel injector) 21 is arranged on the -1- wall portion of the third intake passage 14, and fuel is directed from this fuel injection valve 21 toward the back surface of the umbrella portion 9a of the third intake valve 9. It is designed to be sprayed.

As shown in particular detail in FIG. 3, for example, the umbrella portion 9a of the third intake valve 9 has an inclination angle θ of an extension surface F extending from the lower part of the stem 9b, as shown by the imaginary line. It is formed to be considerably larger than the inclination angle θ of the extending surface, and the curvature is also set to be small.

As a result, the intake air supplied from the third intake passage 14 when the third intake valve 9 is opened has a large inclination angle θ of the inclined surface formed by the stem 9b of the umbrella portion 9a as described above. The fuel (droplets) adhering to the periphery of the umbrella portion 9a and the edge of the boat opening are scraped off at a faster speed than before and enters the vicinity of the spark plug 6 in the engine combustion chamber 5.

As a result, stratification is properly promoted, combustibility is improved, and output is improved. At the same time, atomization of droplet fuel is promoted and the amount of HC generated is reduced, resulting in good exhaust emission performance. becomes.

[Brief explanation of the drawing]

FIG. 1 is a horizontal cross-sectional view of an engine cylinder head showing the configuration of an intake system of a multi-valve engine according to an embodiment of the present invention, FIG. 2 is a central longitudinal cross-sectional view of the same, and FIG. It is an enlarged view of the main part. 1 ・ ・ 2 ・ ・ 4 ・ ・ 5 ・ ・ 6 ・ ・ 7 ・ 8 ・ ・ 9 ・ 9a ・ 9b ・ l 2 ・ l 3 ・ l 4 ・ 2 l ・ ・Engine body, cylinder block, cylinder nozzle - Engine combustion chamber - Spark plug - First intake valve - Second intake valve - Third intake valve - Umbrella - Stem - First intake passage - Second intake passage - Third intake passage - Fuel Injection valve-70- Fig. 3

Claims (1)

[Claims] 1. In an intake multi-valve engine comprising a plurality of intake valves per cylinder and a plurality of intake ports corresponding to the intake ports, and a fuel injector is provided in any of the plurality of intake ports, the intake valve has the fuel injector. The port is opened near the center of the cylinder head of the same engine, and the angle of the slope from the stem to the periphery of the umbrella of the intake valve of the intake port is set larger than the angle of the slope of the intake valve of the other intake ports. This is an intake system for a multi-valve engine.