JPS61252851A - Spark ignition type engine - Google Patents

Abstract

PURPOSE:To reduce fuel consumption and improve the engine output by installing a control means for operating a fuel injection nozzle, first spark plug, fuel feeding means, and the second spark plug. CONSTITUTION:A fuel injection nozzle 13 is arranged in the combustion chamber 12 of a cylinder head 3. On engine start, the nozzle 13, first spark plug 14, injector 15 and the second spark plug 16 are operated. In case of the engine with low load, the nozzle 13 and the first spark plug 14 are operated and a swirl control valve 17 is closed, and in case of high load, the nozzle 13, first spark plug 14, injector 15 and the second spark plug 16 are operated, and a control means 21 for setting the swirl control valve at a prescribed opening- degree is installed. Thus, fuel consumption can be reduced, and the output of the engine can be improved.

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 also injected from the fuel supply means to form a mixture using the entire intake air in the intake passage, and this mixture is supplied to the combustion chamber and the nozzle. mixes with the lean mixture produced by the injected fuel from the
Engines are known that increase air utilization and improve engine output by igniting with a spark plug and causing premixed 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.

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.

In addition, in a spark ignition engine that has both a nozzle and a fuel supply means, when the engine is started, fuel is supplied from both the nozzle and the fuel supply means to promote the vaporization of the fuel. It is thought to improve sex.

However, while the fuel injected from the nozzle diffuses near the injection port of the nozzle, the fuel from the fuel supply means is drawn into the cylinder from the intake passage along with the intake air, so the mixture generated by each fuel is mixed into the cylinder. Since the spark plugs are placed in different positions within the engine, good ignitability cannot be obtained even if the spark plugs are operated selectively.

Therefore, a further object of the present invention is to reliably ignite the air-fuel mixture by operating both spark plugs at the time of starting.

(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. The engine is further provided with a control means for operating the nozzle, the first spark plug, the fuel supply means, and the second spark plug when the engine is started.

(Function) With the above configuration, in the present invention, when the engine is started, the nozzle and the fuel supply means operate, and the air-fuel mixture generated by the injected fuel from the nozzle stays in the combustion chamber, and the air-fuel mixture from the fuel supply means is activated. The air-fuel mixture generated by the fuel remains in the cylinder. The air-fuel mixture remaining in the combustion chamber is successfully ignited by the operation of the first spark plug located near the nozzle nozzle, and the mixture is ignited inside the cylinder by the operation of the second spark plug located approximately in the center of the cylinder bore. The stagnant air-fuel mixture will be ignited well. Also, after starting, when the engine is under low load, the nozzle and the first spark plug operate, and fuel is injected from the nozzle between the intake stroke and the compression stroke, so that the area near the nozzle nozzle becomes rich. A stratified lean WI mixture is formed. and,
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, and stratified combustion is performed.

On the other hand, when the load is high, the nozzle, the first ignition plug, the fuel supply means, and the second ignition plug operate, and the fuel supply means generates an air-fuel mixture using the entire intake air in the intake passage. is sucked into the cylinder and mixed with the lean air-fuel mixture generated by the fuel injected from the nozzle, and a high combustion rate is achieved by ignition of the second spark plug and first spark plug located approximately in the center of the cylinder bore. Premix combustion of the air-fuel mixture is performed.

(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 boat 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 boat 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 boat 7.

A substantially concave combustion chamber 12 opening 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 a fuel injection nozzle 13 is disposed within the combustion chamber 12.
Between the intake stroke and the compression stroke, fuel is injected to generate a stratified rarefied mixture in the cylinder 1 so that the vicinity of the injection port of the nozzle 13 is rich.

Further, in the combustion chamber 12, a first spark plug 14 is arranged near the spout portion of the nozzle 13.

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 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. The 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 is connected to an actuator 18 in the main intake passage 8 upstream of the injector 15.
The main intake passage 8 upstream of the swirl control valve 17 and the first intake passage 8a immediately upstream of the first intake boat 5 are communicated with each other by a bypass passage 19. When the engine is under low load, the swirl control valve 17 is closed and the intake air is passed only through the bypass passage 19 to increase the flow velocity to generate a swirl in the cylinder 1, and when the engine is under high load, the swirl control valve 17 is set to a predetermined opening degree. The intake air is supplied to the cylinder 1 at a flow rate corresponding to the engine speed and load.

The nozzle 13, injector 15 and actuator 18 are connected to the CPtJ 20, and the first... The second spark plugs 14 and 16 are connected to the CPU 20 via igniters 22a and 22b, respectively,
Signals such as engine speed N1 throttle opening P1 cold water IT and intake negative pressure B are input to the CPtJ20, and when the engine is started, the nozzle 13, first spark plug 14, injector 15 and second The spark plug 16 is operated, and when the engine is under low load, the nozzle 13 and the first spark plug 14 are operated and the swirl control valve 17 is closed, while when the engine is under high load, the nozzle 1 is activated.
3. First spark plug 14. The injector 15 and the second fire plug 16 are operated and the swirl control valve 17 is operated.
A control means 21 is configured to set the opening degree to a predetermined opening degree.

Next, the operation of the control means 21 will be explained based on the flowchart shown in FIG.
In Step 1, the engine speed N and throttle opening P are read, in Step S2, the cooling water temperature T and intake negative pressure B are read, and in Step S3, it is determined whether or not the engine is starting. In step S4, the school control valve 17 is fixed at a predetermined opening degree, and in step S5, the injection amount QA and injection time T A of the nozzle 13 at the time of startup, as well as the injection amount QA and injection timing Te of the injector 15 are determined. Then, based on these determined values QA, TA, QB, and TB, the nozzle 13 and the injector 15 are operated in step S6. As a result, the air-fuel mixture generated by the fuel injected from the nozzle 13 remains in the combustion chamber 12, and
The air-fuel mixture generated by the fuel injected from the injector 15 stays in the cylinder 1, and the amount of vaporized fuel in the cylinder 1 increases. On the other hand, in parallel with the generation of this mixture,
In step S7, the ignition timings of the first ignition plug 14 and the second ignition pillar 16 are determined, and based on the determined values, the first ignition plug 14 and the second ignition plug 16 are operated in step S8, and the process returns to step S1.

As a result, the first spark plug 14 ignites the combustion chamber 1.
It is possible to satisfactorily ignite the air-fuel mixture that boils down to the cylinder 1, and also to satisfactorily ignite the air-fuel mixture remaining in the cylinder 1 by igniting the second spark plug 16, thereby improving the ignitability at the time of starting.

Next, after starting, the process proceeds from step S3 to 89, where the cooling water temperature T is compared with the warm-up room completion temperature To, and when T≦To (No), it is determined that the warm-up has not yet been completed, and the swirl is started in step S+e. After the control valve 17 is fixed at a predetermined opening degree, the nozzle 13 is opened during warm-up in step S1.
Injection I OA and injection timing TA and injection of injector 15! ! 11tliQB and injection timing TB are determined. Based on these determined values QA, TA, Qa, and TB, the nozzle 13 and the injector 15 are operated in step S12, and the ignition timings of the first and second spark plugs 14, 16 are determined in step S13, and step SN Activate both ignition pillars 14 and 16 and step $1
Return to and perform warm-up operation. Then, when the warm-up is completed and the cooling water ifMT rises, and it is determined in step S9 that T>To is YES, each of the above input values N is determined in the next step S +s.
, P, T, B, the intake air flow rate A and the injected fuel flow ff1F are calculated, and in the next step S16, this intake air ? The excess air ratio λ is calculated based on the lI amount A and the injected fuel flow rate F.

Next, in step S17, this excess air ratio λ is compared with the reference excess air ratio λO, and if YES (λ≧λ0), it is determined that the load is low, and the swirl control valve 17 is closed in step S+a. This prevents the air-fuel ratio of the air-fuel mixture in the cylinder 1 from becoming over-lean due to a decrease in the intake air flow rate.
The injected fuel is unevenly distributed in the upper part of the cylinder 1.

Thereafter, in step S+s, the injection amount QA and injection timing TA of the nozzle 13 are determined. Then, by operating the nozzle 13 and injecting fuel in step Sa based on these determined values QA and TA, the injected fuel and the swirl create a stratified lean state in which the vicinity of the nozzle injection port becomes rich. A mixture is generated.

Meanwhile, in parallel with the generation of this lean mixture, step 82
1, the ignition timing of the first ignition plug 14 is determined, and based on this determined value, the first ignition plug 14 is operated in step 822 to ignite the lean air-fuel mixture and cause 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 S17, N of A and λ0.

When , it is determined that the load is high, and in step Sn, the set opening degree θ of the swirl control valve 17 is calculated according to the intake air flow MA, and then in step S24, 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 825, the jet #l of the nozzle 13 is
IQA, injection timing TA and injector 15
The injection IQs and injection timing TB are determined. and,
Based on these determined values QA, TA, Qe, and T date, the nozzle 13 and injector 15 are operated in step 82B. As a result, an air-fuel mixture is generated by injecting fuel from the injector 15 using the entire intake air in the main intake passage 8, and this air-fuel mixture is sucked into the cylinder 1 and generated by the fuel injected from the nozzle 13. mixed with the lean mixture. On the other hand, in parallel with the generation of this mixture,
In step 827, the ignition timing of the first ignition plug 14 and the second ignition plug 16 is determined, and based on this determined value, the first ignition plug 14 and the second ignition plug 16 are operated in step 82B to ignite the air-fuel mixture. Ignition and premix combustion. In this case, since the second ignition plug 16 is arranged approximately at the center of the cylinder bore, the flame propagation time to the circumferential edge of the cylinder 1 is J
It is possible to increase the combustion speed by converting it to 1wi. Furthermore, since the first spark plug 14 also operates, the combustion speed of the air-fuel mixture in the deep combustion chamber 12 can also 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 large, ensuring engine output under high load, and the injection speed! ) Even when the amount of fuel is large, the injection pulse width can be made as short as possible to improve the control accuracy of the injection timing. Moreover, since the spray angle of the injector 15 is set smaller than the spray angle of the nozzle 13, it is possible to suppress the injected fuel from adhering to the intake passages 8a and 8b, thereby reducing wasteful fuel consumption. .

In addition, 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 eroded during premixed combustion that 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 IOA and Qe 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 P1 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 P is changed to the throttle opening degree.
- Find the PzP electric current.

Next, in step S4, the swirl control valve opening θ corresponding to the engine speed N2 and throttle opening P2 is determined based on the map, and in step Ss, the swirl control valve opening θ of the nozzle 13 and the injector 15 is determined based on the map.
Injection rate X and basic injection amount τ0 of injection lNff1QA and Qe are determined. Then, in the next step S6, the amount of change ΔP in the throttle opening is compared with the acceleration determination reference value ΔPO, and when ΔP>ΔPO (YES), it is determined that acceleration is occurring, and in step S7, additional fuel Δτ=k・ΔP (k is a proportionality constant). On the other hand, when ΔP≦PO (No), it is determined that it is not accelerating, and the additional fuel Δτ is turned off in step S8.
Then, in step S9, these X, τ0. 8 of Δτ
Each injection mQA-(1-x)@τO,Qs based on the value
Determine =x·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 pulp 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 means for generating swirl but also as a pulp for regulating the intake air flow rate, which is effective in making 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 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 Q8 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
Instead of switching completely depending on the load state of the engine, for example, the fuel injection amount ratio of the nozzle 13 may be increased during low load, and the fuel injection amount ratio of the nozzle 13 may be decreased in a high load range. Roughly speaking, the proportion of fuel supplied to the nozzle 13 and the injector 15 may be changed depending on the degree of opening of the swirl control pulp 17.

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 vent 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. This is an application of the present invention.In this embodiment, the intake/exhaust valves 10.11 are arranged at an angle, so the diameter of the intake/exhaust boat 5.7 can be set large. 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-mentioned embodiments, and not only the first ignition plug 14 but also the second ignition column 16 may be arranged to face the combustion chamber 12. 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 starting the engine, the nozzle and the fuel supply means are operated to generate fuel generated by the nozzle and the fuel supply means. The air-fuel mixture is allowed to stay in the combustion chamber and cylinder, respectively, and the first spark plug placed near the nozzle nozzle and the second spark plug placed approximately in the center of the cylinder bore are activated. By using these two points of ignition, the air-fuel mixtures staying at different positions can be ignited reliably and satisfactorily, thereby improving the ignitability.

Furthermore, when the engine is under low load, fuel is injected from the nozzle between the intake stroke and the compression stroke to form a stratified lean mixture that is rich near the nozzle nozzle.
The first spark plug placed near the nozzle nozzle is ignited to stratify and burn the lean air-fuel mixture, while at high loads, the fuel supply means uses the entire intake air in the intake passage to send the generated air-fuel mixture into the cylinder. The air-fuel mixture is sucked in and mixed with the lean air-fuel mixture generated by the fuel injected from the nozzle, and the air-fuel mixture is premixed and combusted by igniting the second spark plug and first spark plug located approximately in the center of the cylinder bore. This will improve ignitability during stratified combustion by unevenly distributing fuel and optimizing the ignition position, prevent abnormal combustion during premix combustion, and improve combustion stability by optimizing the ignition position. It is possible to both reduce fuel consumption through stratified combustion and improve engine output through premixed combustion with increased volumetric efficiency during high loads.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the present invention, and FIGS. 1 to 5 show the first embodiment of the present invention. 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 CPLI. FIG. 5 is a general schematic diagram showing the second embodiment, and 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, and FIG. 9 is an overall schematic configuration diagram showing the fourth embodiment.
FIG. 10 is a schematic plan view of FIG. 9. 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, 20... CPU121... 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, and a second spark plug disposed approximately in the center of the cylinder bore. A spark ignition type engine, characterized in that it is provided with a control means for operating the nozzle, a first spark plug, a fuel supply means, and a second spark plug at the time of starting.