JPS61244822A - Spark-ignition engine - Google Patents

Abstract

PURPOSE:To improve fuel consumption of an engine and its output, by providing a fuel injection nozzle and a spark plug in a combustion chamber while a separate spark plug in a squash area, 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 the 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 provides an injector 15 to be arranged in an intake passage 8 and actuated when the engine performs premixed combustion. The engine, hollowly providing toward the combustion chamber 12 in the upper end part of a piston 4 a guide channel 17 for forming a squash area 16 extended in a diametric direction of the piston 4, arranges the second spark plug 18, acting when the engine is in premixed combustion, in the cylinder head 3 in almost the central part of a cylinder bore corresponding to said squash area 16.

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. It is known that the engine output is improved by increasing the air utilization rate 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, during stratified combustion, the center of the cylinder bore will contain the part of the lean air-fuel mixture. Since lean parts are distributed, ignitability will be impaired.
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The present invention has been made in view of the above, and an object of the present invention is to provide a spark ignition engine that uses stratified combustion and premix combustion depending on the load as described above. By additionally installing a dedicated spark plug in an appropriate position, ignitability during stratified combustion and combustion stability during premixed combustion are ensured, while improving fuel efficiency through stratified combustion and improving engine efficiency through premixed combustion. The goal is to achieve both improvements in output.

However, in this case, since the spark plug dedicated to premix combustion does not operate during stratified combustion, incomplete combustion products such as carbon are likely to accumulate in the ignition area during stratified combustion. For this reason, there is a problem in that mis-sparking occurs during premix combustion, resulting in ignition errors.

Therefore, a further object of the present invention is to prevent mis-sparking of the second ignition plug by scavenging the ignition portion of the second ignition plug using a squish flow.

(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 in 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. Furthermore, a squish area extending toward the combustion chamber is formed in at least one of the lower end of the cylinder head or the upper end of the piston, and a second squish area is formed in the squish area.
Place the spark hydrant. The engine is configured to include a control means for operating the nozzle and the first spark plug and disabling the second spark plug 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 and the first ignition plug, and the second ignition plug is inoperative, so that the nozzle and the first ignition plug are inoperative during the intake stroke and the compression stroke. By injecting the fuel, a stratified lean air-fuel mixture is formed that is rich near the nozzle outlet. 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. During this time, the ignition part of the second ignition plug is scavenged by the squish flow, so incomplete combustion products do not accumulate. On the other hand, the fuel supply means and the second spark plug are operated by the control means at times other than when the angle load is low.
An air-fuel mixture is generated by the fuel supply means using the entire intake air in the intake passage, and this air-fuel mixture is sucked into the cylinder, and the second ignition is arranged in a squish area set approximately at the center of the cylinder bore. Ignition of the plug causes premix combustion of the air-fuel mixture at a high combustion rate. At that time, since incomplete combustion products are not deposited on the second ignition plug,
No mis-sparks and no ignition errors.

(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 an intake boat 6 and an exhaust boat 7 that open into the cylinder 1, respectively, and the downstream end of an intake passage 8 is connected to the intake boat 6, so as to supply intake air to the cylinder 1. There is. Further, the upstream end of an exhaust passage 9 is connected to the exhaust boat 7, so that exhaust gas from the cylinder 1 is discharged. In addition, 10
11 is an intake valve provided on the intake boat 6, and 11 is an exhaust valve provided on the exhaust boat 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 boat 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
The system is designed to generate a stratified lean mixture that is rich near 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 in the intake passage 8, and operates during premix combustion to inject and supply fuel into the intake passage 8, thereby creating an air-fuel mixture in the intake passage 8. It is designed to generate. Further, a guide channel 17 is recessed in the upper end of the piston 4 to form a squish area 16 extending in the diametrical direction of the piston 4 through the center of the piston 4 toward the combustion chamber 12. 16
This creates a squish flow. and,
A second ignition plug 18 that operates during premix combustion is disposed in the cylinder head 3 at a substantially central portion of the cylinder bore corresponding to this squish area 16, and is configured to scavenge the ignition section with a squish flow.

The nozzle area of the nozzle 13 is set smaller than the nozzle area 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 method.

Further, the first spark plug 14 has a fired type with a low heat value, while the second spark plug 18 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.

Furthermore, a swirl control valve 19 is connected to the actuator 20 in the intake passage 8 upstream of the injector 15.
The actuator 20 is arranged so as to be connected to the actuator 20.
When the load of the engine is low, the swirl control valve 19 is set to a small opening to increase the flow velocity of intake air to generate swirl in the cylinder 1, and when the load is high other than low load, the swirl control valve 19 is set to a small opening. The opening is set to a large degree to supply intake air to the cylinder 1 at a flow rate depending on the engine speed and load.

The nozzle 13, the injector 15, the first . The second spark plug 14.18 and the actuator 20 are CPU
21 and is connected to the first. Second ignition plug 14
．． 18 are C via igniters 22a and 22b, respectively.
The CPLI 21 is connected to the CPLI 21, which receives signals such as engine speed N1, throttle opening P, cooling water temperature T, and intake negative pressure B, and when the engine is under low load, the nozzle 13 and the first ignition The plug 14 is activated, the swirl control valve 17 is closed, and the second spark plug 18 is deactivated, while the first spark plug 14. The injector 15 and second ignition column 18 are operated, and the swirl control valve 19 is set to a predetermined opening degree.

A control means 23 is configured to determine the speed.

Next, the operation of the control means 23 will be explained based on the flowchart shown in FIG.
After reading the engine speed N and throttle opening P in Step 1 and reading the cooling water temperature T and intake negative pressure B in Step S2, the intake air is adjusted in Step S3 based on these input values N, P, T, and B. The flow mA and the injected 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 rate A and the injected fuel flow rate F.

Next, in step S5, this excess air ratio λ is compared with the reference excess air ratio λ0, and when YES (λ≧λO), it is determined that the load is low, and the swirl control valve 19 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 nozzle 13 injects [I
Determine QA and jl'J T A at the time of injection. Then, step S is performed based on these determined values QA and TA.
By operating the nozzle 13 at step 8 to inject fuel, the injected fuel and the swirl generate a stratified lean air-fuel mixture that is rich in the vicinity of the nozzle nozzle. 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 18 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.

Further, at this low load, the second ignition plug 18 does not operate, but since the ignition part of the second ignition plug 18 is scavenged by the squish flow, incomplete combustion products are not deposited and it is kept clean.

On the other hand, in step S5, N of λ×λO.

In this case, it is determined that the load is high other than the low angle load, and the set opening degree θ of the swirl control valve 19 is calculated in accordance with the intake air flow rate A in step Sn, and then the swirl control valve 19 is adjusted in step 812. Set the opening degree to θ. As a result, the air-fuel mixture supplied to the cylinder 1 can be accurately controlled to an appropriate mixture ratio, and at the same time, the swirl control valve 19 is fully opened when the load is high, 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 Q8 and injection timing Te are determined.

Then, in step SI4, the injector 15 is operated to inject fuel based on these determined values Qa and Te, thereby generating an air-fuel mixture using the entire intake air in the intake passage 8. inhaled into the body. Meanwhile, in parallel with the generation of this air-fuel mixture, step S
+s, the ignition timing of the first and second spark plugs 14.18 is determined, and based on this determined value, step S16
The first and second spark plugs 14 and 18 are operated to ignite the air-fuel mixture and cause premix combustion. In this case, since the second ignition plug 18 is located approximately in the center of the cylinder bore,
The flame propagation time to the circumferential end of the cylinder 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 larger than the nozzle area of the nozzle 13, the injection amount can be set to a large amount, ensuring engine output during high loads, and when the injection amount is large. Also, the injection pulse width can be made as short as possible to improve the control accuracy of the injection timing. Moreover, the spray angle of the injector 15 is
Since the spray angle is set smaller than the spray angle of No. 3, it is possible to suppress the injected fuel from adhering to the intake passage 8, and it is possible to avoid wasteful fuel consumption.

Further, since the second ignition plug 18 is of a cold type with a high heat value, it is possible to prevent the second ignition plug 18 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.

In addition, since the second ignition plug 18 is kept clean by scavenging air in the squish flow during low loads, mis-sparking does not occur during high-load conditions, and ignition errors can be prevented.

Next, the determination operation of each injection IOA and Qe of the nozzle 13 and injector 15 during engine acceleration will be explained based on the flowchart shown in FIG. P1 is read, and then in step $2, the engine rotation speed N2 and throttle opening P2 are read after a minute time has elapsed, and in step S3, the change in throttle opening ΔP- is read.
Find P2-PI.

Next, in step S4, the swirl cone l-0-le valve angle θ corresponding to the engine speed N2 and throttle opening P2 is determined based on the map, and in step S5, each of the nozzle 13 and injector 15 is determined based on the map. Injection f! The injection ratio x of kQA and QB and the basic injection amount τ0 are determined. 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 proportionality constant) is set in step Sy. 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 0.
Then, in step S9, these X, τ0. 8 of Δτ
Based on the value, each injection amount QA = (1-X) ・7:O
, QB =X Determine the conflict rO+Δτ. in this way,
When the engine accelerates, by injecting fuel from both the nozzle 13 and the injector 15, it is possible to smoothly transition from stratified combustion to premixed 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 19 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 19 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 19 is used not only as a means for generating swirl, but also as a valve for regulating the intake air flow rate, which makes the engine more compact than providing separate valves. It's advantageous.

Note that it is preferable to advance the injection timing TA of the nozzle 13 when the injection fn QA 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. Furthermore, if the injection timing QB of the injector 15 is set to the intake stroke where the intake air flow rate is highest, a homogeneous air-fuel mixture can be obtained.

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 19.

5 and 6 show a second embodiment of the present invention, in which a guide channel 17' is provided for forming a squish area 16' extending toward the combustion chamber 12 through approximately the center of the lower end of the cylinder head 3. A recess is formed and the cylinder head 3
The second ignition plug 18 is arranged in the squish area 16', and the same functions and effects as in the first embodiment are achieved.

Note that the present invention is not limited to the above embodiments, and guide channels may be formed at both the lower end of the cylinder head 3 and the upper end of the piston 4. Further, the squish area may be formed by other means than the guide channel.

Furthermore, it is also applicable to engines in which the combustion chamber is formed at the upper end of the piston 4 or engines in which the combustion chamber 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 engine is under low load, fuel is injected from the nozzle between the intake stroke and the compression stroke, so that the vicinity of the nozzle nozzle becomes rich. A stratified lean mixture is formed, and the first spark plug placed near the nozzle nozzle is ignited to cause stratified combustion of the lean mixture, and the ignition part of the second spark plug is scavenged with a squish flow. While preventing the accumulation of incomplete combustion products, when the load is high other than when the angle load is low, the fuel supply means uses the entire intake air in the intake passage to draw the generated air-fuel mixture into the cylinder. The second ignition plug located in the center is ignited to cause premixed combustion of the air-fuel mixture, so the scale during stratified combustion improves ignition performance by unevenly distributing fuel and optimizing the ignition position, and achieves premixed combustion. Occasionally, a clean second ignition plug can ignite well without causing ignition errors, and optimization of the ignition position improves combustion stability, while reducing fuel consumption through stratified combustion at low loads and volumetric efficiency at high loads. This makes it possible to simultaneously improve engine output through premixed combustion with increased combustion.

[Brief explanation of drawings]

The drawings illustrate and illustrate embodiments of the present invention, and FIGS. 1 to 4 show a first embodiment of the present invention, FIG. 1 is a general schematic diagram, and FIG. 2 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 tAI during acceleration of the CPU. FIG. 5 is a general schematic diagram showing the second embodiment, and FIG. 6 is a schematic plan view of FIG. 5. 1...Cylinder, 3...Cylinder head, 4...
Piston, 8... Intake passage, 12... Combustion chamber, 13
...Nozzle, 14...First spark plug, 15...Injector, 16.16'...Squish area, 1
8... Second ignition plug, 21... CPU, 23... Control means.

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; The formed squish area,
a second spark plug disposed in the squish area, and a control means for operating the nozzle and the first spark plug and disabling the second spark plug when the engine is under low load. spark ignition engine.