JPS61244821A - Spark-ignition engine - Google Patents

Abstract

PURPOSE:To improve fuel consumption of an engine and its output, by providing a fuel injection nozzle and two spark plugs in a predetermined position in a combustion chamber while a fuel supply means in an intake passage, in the case of the engine properly using the operation to be divided into stratified combustion and premixed combustion in accordance with a load. CONSTITUTION:An engine forms an almost hollow-shaped combustion chamber 12, opened to a cylinder 1, in a side of an exhaust port 7 in the bottom end part of a cylinder head 3, and the engine arranges in said chamber 12 both a fuel injection nozzle 13 and the first spark plug 14, operating when the engine is low loaded, in the vicinity of a jet part of said nozzle 13. While the engine, providing an injector 15 to be arranged just in the upstream of the branch part in a main intake passage 8, actuates the injector when the engine performs premixed combustion. Further the engine, arranging the second spark plug 16 in the cylinder head 3 almost in the central part of a cylinder bore, similarly actuates the spark plug when the engine performs the premixed combustion. While the engine, providing a swirl control valve 17 as a swirl generating means in the main intake passage 8 in the upstream of the injector 15, operates said valve 17 by an actuator 18.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a spark ignition engine, and relates to an improvement in which stratified combustion and premix combustion are performed depending on the load.

(Prior Art) Conventionally, as a spark ignition engine aiming at reducing fuel consumption and improving output, as disclosed in Japanese Patent Application Laid-open No. 56-151213, a cylinder head is provided with a combustion chamber from the intake stroke. A nozzle for injecting fuel during the compression stroke is disposed, an ignition plug is disposed near the nozzle of the nozzle, and a fuel supply means for supplying fuel into the intake passage is disposed in the intake passage, When the load is low, fuel is injected only from the nozzle to form a stratified lean mixture that is rich near the nozzle nozzle in the combustion chamber, and this lean mixture is ignited well with a spark plug to cause stratified combustion. At the same time, when the load is high, fuel is injected from the fuel supply means to form an air-fuel mixture in the intake passage, making full use of the intake air, and this air-fuel mixture is supplied to the combustion chamber at the ignition plug. Engines are known that increase air utilization and improve engine output by igniting and premixing combustion.

(Problem to be Solved by the Invention) However, in the conventional spark-ignition engine described above, this problem occurs because the nozzle is arranged offset from the approximate center of the cylinder bore to avoid interference with the intake and exhaust valves. The ignition plug disposed near the nozzle outlet is also disposed offset from the center of the cylinder bore. Therefore, during premix combustion, the flame propagation time to the cylinder peripheral end cannot be minimized, so knocking is likely to occur, resulting in a reduction in engine output. In order to increase the combustion speed during premix combustion by arranging the spark plug in the center of the cylinder bore away from the nozzle nozzle, during stratified combustion, the center of the cylinder bore is filled with rare Sa gas. Since the lean portion is distributed, the ignitability will be impaired.

Further, when carrying out stratified combustion as described above, in order to improve the ignitability, it is preferable that the fuel injected from the nozzle is distributed as unevenly as possible near the nozzle outlet.

Therefore, one idea is to suppress the flow of fuel injected from the nozzle to the lower part of the cylinder and make it unevenly distributed in the lower part of the cylinder by, for example, creating a swirl in the cylinder by making the intake boat a helical port. It will be done.

However, in an engine provided with such a helical port, the volumetric efficiency decreases due to the resistance of the intake boat when the load is high, so a problem arises in that the engine output cannot be sufficiently improved even by premix combustion.

The present invention has been made in view of these points, and its purpose is to provide a spark ignition engine that uses stratified combustion and premix combustion depending on the load as described above. By arranging dedicated spark plugs at appropriate positions and generating swirl within the cylinder only during stratified combustion, the engine ensures ignition performance during stratified combustion and combustion stability during premixed combustion. The aim is to achieve both improved fuel efficiency through stratified combustion and improved engine output through premixed combustion.

(Means for solving the problem) In order to achieve the above object, the solving means of the present invention forms a substantially concave combustion chamber that opens into the cylinder at at least one of the lower end of the cylinder head or the upper end of the piston, A nozzle that injects fuel between the intake stroke and the compression stroke is provided in this combustion chamber, and a first nozzle is provided near the nozzle of this nozzle.
Place the spark hydrant.

Further, a fuel supply means for supplying fuel into the intake passage is provided, and a second spark plug is disposed approximately in the center of the cylinder bore. Further, a swirl generating means for generating a swirl inside the cylinder is provided. Further, a control means is provided for operating the nozzle, the first spark plug, and the swirl generating means when the engine is under low load.

(Function) With the above configuration, in the present invention, when the load of the engine is low, the control means operates the nozzle, the first spark plug, and the swirl generation means, and the swirl generation means generates a swirl in the cylinder. In response to this swirl, fuel is injected from the nozzle between the intake stroke and the compression stroke, resulting in a stratified lean mixture in which the fuel is unevenly distributed in the lower part of the cylinder together with the swirl, and the vicinity of the nozzle outlet is rich. Qi is formed.

Of this stratified lean air-fuel mixture, the lean air-fuel mixture is reliably ignited by ignition of the first spark plug disposed near the nozzle nozzle where the rich air-fuel mixture is unevenly distributed, resulting in stratified combustion. On the other hand, when the angle load is not low, the control means operates the fuel supply means and the second ignition plug and deactivates the swirl generation means, so that the fuel supply means utilizes the entire intake air in the intake passage to generate a mixture. is generated, and this air-fuel mixture is smoothly sucked into the cylinder without resistance due to the inactivation of the swirl generating means, increasing volumetric efficiency, and fast combustion due to the ignition of the second spark plug located approximately in the center of the cylinder bore. Premix combustion of the air-fuel mixture is achieved at this speed.

(Example) Embodiments of the present invention will be described below based on the drawings.

1 and 2 show a first embodiment of the invention. Reference numeral 1 denotes a cylinder formed by a cylinder block 2 and a cylinder head 3, and a piston 4 is slidably inserted into the cylinder 1. The above cylinder head 3
are formed with first and second intake boats 5.6 and an exhaust port 7 that open into the cylinder 1, respectively, and the first and second intake boats 5.6 are connected to the main intake passage 8 in a bifurcated manner. Branched first and second intake passages 8a.

The downstream ends of the cylinders 8b are individually connected to supply intake air to the cylinder 1.

Further, the upstream end of an exhaust passage 9 is connected to the exhaust port 7, so that exhaust gas from the cylinder 1 is discharged. Note that 10.10 is an intake valve provided on the first and second intake boats 5.6, and 11 is an exhaust valve provided on the exhaust port 7.

A substantially concave combustion chamber 12 that opens into the cylinder 1 is formed at the lower end of the cylinder head 3 on the exhaust port 7 side. A fuel injection nozzle 13 is disposed within the combustion chamber 12 of the cylinder head 3, and operates when the engine is under low load to inject fuel into the combustion chamber 12 between the intake stroke and the compression stroke of the cylinder 1. Nozzle 13 inside cylinder 1
It is designed to generate a stratified rare f [aiki that is rich in the vicinity of the nozzle. In addition, the combustion chamber 12
Inside, a first spark plug 14 is arranged near the spout of the nozzle 13, which operates when the engine is under low load.

On the other hand, an injector 15 as a fuel supply means is disposed immediately upstream of the branching part of the main intake passage 8, and operates during premix combustion to inject and supply fuel into the main intake passage 8. An air-fuel mixture is generated within the intake passage 8. In addition, a second spark plug 16 that operates during premix combustion is installed in the cylinder head 3 located approximately in the center of the cylinder bore.
is located.

The nozzle area of the nozzle 13 is set smaller than that of the injector 15, and the spray angle of the nozzle 13 is set larger than the spray angle of the injector 15. Fuel is injected appropriately depending on the combustion method.

Further, the first spark plug 14 has a fired type with a low heat value, while the second spark plug 16 has a cold type with a high heat value, so that it can stably produce a spark depending on the combustion method. I'm trying to make it happen.

Further, a swirl control valve 17 as a swirl generating means is connected to an actuator 18 and arranged in the main intake passage 8 upstream of the injector 15, and the main intake passage 8 upstream of the swirl control valve 17 and the first intake boat 5 It communicates with the first intake passage 8a immediately upstream by a bypass passage 19, and when the engine is under low load by operating the actuator 18, the swirl control valve 17 is closed and the intake air is passed only through the bypass passage 19 to increase the flow velocity. As a result, a swirl is generated in the cylinder 1, and when the load is not low, the swirl control valve 17 is set to a predetermined opening degree to supply intake air to the cylinder 1 at a flow rate corresponding to the engine speed and load. ing.

The nozzle 13, the injector 15, the first . The second spark plug 14,16 and the actuator 18 are CPL
I20 and the first. 2nd ignition plug 1
4.16 are connected to the TCPU 20 via igniters 22a and 22b, respectively, and the CPL 120 receives signals of engine speed N1, throttle angle P1, cooling water IT, and intake negative pressure B. When under load, the nozzle 13 and the first spark plug 14 are activated and the swirl control valve 17 is closed.
A control means 21 is configured to operate the spark plug 16 and set the swirl control valve 17 to a predetermined opening degree.

Next, the operation of the control means 21 will be explained based on the flowchart shown in FIG.
After reading the engine speed N and throttle opening P in step S2, and reading the cooling water temperature T and intake negative pressure B in step S2, based on these input values N, P, T, and B, in step S3. The intake air flow 11A and the injection fuel flow rate F are calculated, and in the next step S4, the excess air ratio λ is calculated based on the intake air flow mA and the injection fuel flow IF.

Next, in step S5, this excess air ratio λ is compared with the reference excess air ratio λ0, and if YES (λ≧λ0), it is determined that the load is low, and the swirl control valve 17 is closed in step S6. This prevents the intake air flow rate from decreasing and the air-fuel ratio of the air-fuel mixture in the cylinder 1 to become over-lean, and also creates a swirl in the cylinder 1, which causes the fuel injected from the nozzle 13 to flow into the cylinder. It will be unevenly distributed in the upper part of 1.

After that, in step S7, the injection amount Q of the nozzle 13 is
A and injection timing TA are determined. Then, based on these determined values QA and TA, nozzle 1 is
3 to inject fuel, the injected fuel and the swirl generate a stratified lean air-fuel mixture that is rich near the nozzle outlet. On the other hand, in parallel with the generation of this lean mixture, the ignition timing of the first spark plug 14 is determined in step S9, and based on this determined value, the first spark plug 14 is operated in step S+o to reduce the lean mixture. The air-fuel mixture is ignited and causes stratified combustion. In this case, since the first spark plug 14 is disposed near the nozzle outlet where the rich air-fuel mixture is unevenly distributed, the lean air-fuel mixture is reliably ignited. Therefore, it is possible to reduce fuel consumption through stratified combustion while maintaining good ignitability.

Further, since the nozzle area of the nozzle 13 is set smaller than the nozzle area of the injector 15, atomization of the injected fuel is promoted and the combustibility of the lean mixture can be improved. Moreover, since the spray angle of the nozzle 14 is set larger than that of the injector 15, the atomization of the injected fuel is further promoted, and the diffusion of the atomized fuel toward the cylinder is promoted, resulting in a lean mixture. Combustibility can be further improved.

Furthermore, since the first ignition plug 14 has a sintered shape with a low heat value, it is possible to stably form a flame kernel even though the mixture is lean, achieving good ignitability. be able to. In this case, setting the arc time of the first spark plug 14 to be longer than the arc time of the second spark plug 16 means that
This is preferable because it improves the ignitability during stratified combustion. In addition, since the first ignition plug 14 is arranged in the recessed, substantially concave combustion chamber 2, turbulence due to squish flow is not generated around the first ignition plug 14, which contributes to improving ignition performance. can.

On the other hand, in step S5, N of λ>λ0.

When this happens, it is determined that the load is not at a low angle, and the process proceeds to step S.
++ calculates the set opening degree θ of the swirl control valve 17 according to the intake air flow rate A, and then in step 312
The swirl control valve 17 is set to the opening degree θ. As a result, the air-fuel mixture supplied to the cylinder 1 can be precisely controlled to the proper mixture ratio, and at the same time, the swirl control valve 17 is fully opened during high loads, and the intake air is drawn into the cylinder 1 smoothly without resistance. Since the volumetric efficiency is increased, it becomes possible to improve the engine output.

After that, in step S13, the injector 15
The injection amount QB and injection timing Te are determined.

Then, in step S)4, the injector 15 is operated to inject fuel based on these determined values Qa and TB, thereby generating an air-fuel mixture using the entire intake air in the main intake passage 8. is sucked into the cylinder 1. Meanwhile, in parallel with the generation of this air-fuel mixture, step S
+s, determining the ignition timing of the second ignition plug 16;
Based on this determined value, the second spark plug 1 is
6 is activated to ignite the air-fuel mixture for premix combustion.

In this case, since the second ignition plug 16 is disposed approximately at the center of the cylinder bore, the flame propagation time to the peripheral end of the cylinder 1 can be minimized and the combustion speed can be increased.

Therefore, it is possible to improve engine output through premix combustion by improving air utilization while improving combustion stability.

In addition, since the nozzle area of the injector 15 is set to be larger than the nozzle area of the nozzle 13,
fi can be set to a large value, ensuring engine output at high loads, and even when the injection amount is large, the injection pulse width can be shortened as much as possible to improve injection timing control accuracy. . Moreover, since the spray angle of the injector 15 is set smaller than that of the nozzle 13,
It is possible to suppress the injected fuel from adhering to the intake passages 8a and 8b, and wasteful fuel consumption can be avoided.

Furthermore, since the second ignition plug 16 is of a cold type with a high heat value, it is possible to prevent the second ignition plug 16 from being damaged during premixed combustion, which generates a high amount of heat. This means that
This is especially advantageous when the engine is under a high load under severe thermal load, and can improve the reliability of the engine.

Next, the determination operation of each injection 11QA, QB of the nozzle 13 and injector 15 during acceleration of the engine is performed in a fourth manner.
To explain based on the flowchart shown in the figure, after a start, the engine speed N1 and the throttle opening P+ are read in step S1, and then in step S2, the engine speed N2 and the throttle opening P2 are read after a short period of time has elapsed.
is read, and in step S3, the change in throttle opening △P
−P2 Find P+.

Next, in step S4, the swirl control valve opening degree θ corresponding to the engine speed N2 and throttle opening degree P2 is determined based on the map, and in step Ss, each injection fiiQA of the nozzle 13 and injector 15, Injection ratio X of Qa and basic injection amount τ
Determine 0. Then, in the next step S6, the change ΔP in the throttle opening is compared with the acceleration determination reference value ΔPO,
When ΔP>ΔPO is YES, it is determined that the vehicle is accelerating, and the additional fuel Δτ−k·ΔP (k is a proportional constant) is set in step S7. On the other hand, when ΔP≦po is NO, it is determined that the vehicle is not accelerating. In step S8, the additional fuel Δτ is set to O, and then in step S9, these X, τ0. Considering the multiple values of Δτ, each injection amount QA-(1-X)・τo, QB
-x・τθ+Δτ is determined. In this way, when the engine accelerates, the nozzle 13 and the injector 1
Premixing from stratified combustion by injecting fuel from both sides.

This allows for a smooth transition to joint combustion.

Moreover, since the additional fuel Δτ is added and injected from the injector 15, it is possible to prevent the air-fuel mixture from becoming over-lean even when the swirl control valve 17 is almost fully opened to supply the amount of intake air commensurate with acceleration. It is possible to improve acceleration performance. Furthermore, since the swirl control valve 17 opens during acceleration, no swirl is generated in the cylinder 1, so injecting the additional fuel Δτ from the injector 15 rather than from the nozzle 13 is advantageous from the standpoint of mixing the air-fuel mixture. be.

Furthermore, in the above embodiment, the swirl control valve 17 is used not only as a swirl generating means but also as a valve for regulating the intake air flow rate, which is advantageous in making the engine more compact than using separate valves. be.

Note that it is preferable to advance the injection timing TA of the nozzle 13 when the injection IOA is large in order to maintain good combustibility. Further, it is preferable to similarly accelerate the atomization of the fuel when the temperature is cold or when starting. moreover,
A homogeneous air-fuel mixture can be obtained by setting the injection timing QB of the injector 15 to the intake stroke where the intake air flow rate is highest.

In addition, as in this embodiment, the nozzle 13 and the injector 15
For example, the ratio of the fuel injection amount of the nozzle 13 may be increased in a low load range, and the ratio of the fuel injection amount of the nozzle 13 may be decreased in a high load range, instead of completely switching between the two. Furthermore, the proportion of fuel supplied to the nozzle 13 and the injector 15 may be changed depending on the opening degree of the swirl control valve 17. Also, in the high load range, the first. Second
Both spark plugs 14 and 16 may be lit,
Ignition can be performed reliably.

5 and 6 show a second embodiment of the present invention, in which a substantially concave combustion chamber 12' is formed at the upper end of the piston 4, and a first spark plug 14 is arranged at the lower end surface of the flat cylinder head 3. The squish flow generated in the cylinder 1 causes turbulence around the first spark plug 14,
This turbulence can speed up the initial flame propagation after ignition.

7 and 8 show a third embodiment of the present invention, which is a pen-me-roof type engine in which the lower end surface of the cylinder head 3 is formed into a conical shape, and the combustion chamber 12'' is formed in the upper end portion of the piston 4. The present invention is applied to.

In this embodiment, since the intake/exhaust valves 10.11 are arranged at an angle, the diameter of the intake/exhaust boat 5.7 can be set large, and the volumetric efficiency can be improved.

Furthermore, FIG. 9 and FIG. 10 show a fourth embodiment of the present invention, in which a hemispherical combustion chamber 12'' is formed at the upper end of the piston 4, which promotes mixing of the air-fuel mixture and is effective at low loads. In addition to improving ignitability in the combustion chamber 12
By lowering the heat dissipation of the combustion chamber 12'', the temperature of the combustion chamber 12'' can be maintained high and the combustibility can be improved.

Further, the present invention is not limited to the above embodiments, and not only the first ignition plug 14 but also the second ignition plug 16 may be arranged to face the combustion chamber 12, so that both This is advantageous when an ignition pillar is also used. Furthermore, it is also applicable to an engine in which the combustion chamber 12 is formed at both the lower end of the cylinder head 3 and the upper end of the piston 4.

(Effects of the Invention) As explained above, according to the spark ignition engine of the present invention, when the load of the engine is low, the nozzle is used in response to the swirl formed in the cylinder by the swirl generating means between the intake stroke and the compression stroke. Fuel is injected from the cylinder, and this fuel is distributed unevenly in the upper part of the cylinder along with a swirl to form a stratified lean air-fuel mixture that is rich near the nozzle orifice, and ignites the first spark plug located near the nozzle orifice. At the same time, except during low angle loads, the mixture generated by the fuel supply means utilizes the entire intake air in the intake passage, and the swirl generation means is deactivated so that the mixture is smoothly transferred into the cylinder. The second ignition plug located approximately in the center of the cylinder bore is ignited to premix and burn the air-fuel mixture. Therefore, during stratified combustion, ignitability is improved by unevenly distributing fuel and optimizing the ignition position. While increasing combustion stability by optimizing the ignition position during premixed combustion, it also reduces fuel consumption through stratified combustion at low loads and improves engine output through premixed combustion with increased volumetric efficiency at high loads. It is possible to achieve both.

[Brief explanation of drawings]

The drawings illustrate embodiments of the present invention, and FIGS. 1 to 4 show the first embodiment of the present invention, and FIG. 1 is an overall schematic configuration diagram, and FIG.
1 is a schematic plan view of FIG. 1, FIG. 3 is a flowchart explaining the basic operation of the CPU, and FIG. 4 is a flowchart explaining the operation of determining the fuel injection amount during acceleration of the CPU. FIG. 5 is an overall schematic configuration diagram showing the second embodiment;
FIG. 6 is a schematic plan view of FIG. 5. FIG. 7 is an overall schematic configuration diagram showing the third embodiment, FIG. 8 is a schematic plan view of FIG. 7, FIG. 9 is an overall schematic configuration diagram showing the fourth embodiment, and FIG. FIG. 1...Cylinder, 3...Cylinder head, 4...
Piston, 8... Main intake passage, 8a... First intake passage, 8b... Second intake passage, 12.12', 12''
, 12″... combustion chamber, 13... nozzle, 14...
1st spark plug, 15...injector, 16...2nd
Spark plug, 17...Swirl control valve, 20
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Claims (1)

[Claims] (1) A substantially concave combustion chamber formed in at least one of the lower end of the cylinder head or the upper end of the piston so as to open into the cylinder, and a nozzle that injects fuel into the combustion chamber between the intake stroke and the compression stroke. , a first spark plug disposed near the spout of the nozzle, a fuel supply means for supplying fuel into the intake passage, a second spark plug disposed approximately in the center of the cylinder bore, and a swirl within the cylinder. What is claimed is: 1. A spark ignition engine, comprising a swirl generating means for generating swirl, and a control means for operating the nozzle, the first spark plug, and the swirl generating means when the engine is under low load.