JPS61250354A - Spark-ignition engine - Google Patents

Abstract

PURPOSE:To reduce fuel consumption in an engine and improve its stability, by forcedly performing premix combustion when the engine is started and gradually transferring the combustion to stratified combustion in accordance with the engine advancing its warming operation, in the case of the engine which properly applies its combustion to be divided into the stratified combustion and the premix combustion in accordance with a load. CONSTITUTION:An engine, forming an almost hollowed combustion chamber 12 in the side of an exhaust port 7 in the bottom surface of a cylinder head 3, arranges in said combustion chamber 12 a fuel injection nozzle 13 and the first spark plug 14 positioned in the vicinity of its jet part. While the engine both provides an injector 15, operated in premix combustion, immediately in the upstream of a branch part of a main intake passage 8 into branch intake passages 8a, 8b connected with two intake ports 5, 6 and arranges the second spark plug 16, operated in premix combustion, in the cylinder head 3 in almost the central part of a cylinder bore. And the engine, when it is started, actuates the injection nozzle 13 and the injector 15, thereafter the engine, when it is in warming operation, decreases the proportion of a supply quantity of fuel by the injector 15 as temperature of the engine increases.

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.

(Problems to be Solved by the Invention) Incidentally, in such a spark ignition engine, fuel is supplied from both the nozzle and the fuel supply means during startup and warm-up when the engine temperature is low to promote fuel vaporization. By doing so, it is possible to improve the ignition performance during startup and the combustion stability during warm-up.

However, in the above-mentioned proposal, stratified combustion cannot be performed during startup and warm-up, so fuel consumption cannot be reduced. Moreover, if the fuel supply from the fuel supply means is stopped and the amount of fuel supplied from the nozzle is increased in order to shift to stratified combustion at the end of warm-up, there will be a delay in the response of the fuel supply from the nozzle and a sudden decrease in the air utilization rate. Due to the decrease, it is not possible to smoothly shift to stratified combustion, and the operating state of the engine becomes unstable.

The present invention has been made in view of the above, and its purpose is to start the engine in a spark ignition engine that uses stratified combustion and premixed combustion depending on the load as described above. Sometimes forced premix combustion is performed, and as the engine warms up after startup, it gradually shifts from premix combustion to stratified combustion as the engine warms up. This improves ignition performance during startup, and improves ignition performance during warm-up. The aim is to achieve both reduction in fuel consumption and engine stability.

(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 is provided in the combustion chamber to inject fuel between the intake stroke and the compression stroke. Further, a fuel supply means for supplying fuel into the intake passage is provided, and an ignition plug is arranged in the combustion chamber. Furthermore, engine temperature detection means for detecting the temperature of the engine is provided. When the engine is started, the nozzle and fuel supply means are operated, and when the engine is warmed up after startup, the output of the engine temperature detection means is received, and as the engine temperature rises, the amount of fuel supplied by the fuel supply means relative to the total fuel supply amount is The structure is such that a control means is provided to reduce the ratio of .

(Function) With the above configuration, in the present invention, when the engine is started, the fuel supply means operates to vaporize the fuel well, and the nozzle operates to enrich the air-fuel mixture, thereby improving ignition performance. During warm-up after startup, as the engine temperature rises as the engine warms up, the ratio of the fuel supply amount of the fuel supply means to the total fuel supply amount gradually decreases, and the ratio of the fuel supply amount of the nozzle gradually decreases. By increasing the amount of air, the mixture is generated by the fuel supply means using the entire intake air in the intake passage, and the mixture is ignited by the ignition plug, resulting in premixed combustion. This results in a stable transition to stratified combustion, which is achieved by igniting the engine with a spark plug, and this stratified combustion reduces fuel consumption during warm-up. Also, when the engine is under low load, the nozzle and spark plug operate to perform stratified combustion, while when the engine is under high load, the nozzle, fuel supply means, and spark plug operate, and the air-fuel mixture generated by the fuel supply means and the nozzle are activated. The lean mixture generated by this is ignited by a spark plug, resulting in premixed combustion.

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

1 and 2 show a first embodiment of the present invention; 1 is a cylinder formed by a cylinder block 2 and a cylinder head 3; a piston 4 is slidably fitted into the cylinder 1; It is inserted. The above cylinder head 3
are formed with first and second intake ports 5, 6 and an exhaust boat 7 that open into the cylinder 1, respectively, and the first and second intake ports 5, 6 are connected to the main intake passage 8 in a bifurcated manner. The first and second intake passages 3a are branched.

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 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 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 lean air-fuel 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 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.

In addition, the first ignition plug 14 has a fired type with a low heat value, while the second ignition pillar 16 has a cold type with a high heat value, so that it can stably produce sparks 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 connected to each other by a bypass passage 8C. 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 8C to increase the flow velocity to generate a swirl inside 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.

Also, engine cooling water I is provided on the side wall of the cylinder block 2.
A water temperature sensor 19 is installed as an engine temperature detection means for detecting the temperature of the engine.

The nozzle 13, injector 15, actuator 18, and water temperature sensor 19 are connected to the CPU 20, and the first... The second spark plugs 14 and 16 are connected to the CPU 20 via igniters 228 and 22b, respectively, and the CPU 20 receives signals such as engine speed N1 throttle opening P1 ignition switch signal I and intake negative pressure B. When the engine is started, the nozzle 13 and the injector 15 are operated, and when the engine is warmed up after starting, the output of the water temperature sensor 19 is received, and as the engine temperature rises, the amount of fuel supplied by the injector 15 relative to the total amount of fuel supplied is adjusted. When the engine load is low, the nozzle 13 and the first spark plug 14 are activated, and the swirl control valve 17 is activated.
On the other hand, when the load is high, the nozzle 13. is closed. A control means 21 is configured to operate the first ignition plug 14, the injector 15, and the second ignition column 16, and to 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.
1 determines whether the engine is starting or not, and Y indicates that the engine is starting.
At the time of ES, the swirl control valve 17 is fixed at a predetermined opening degree in step S2, the total injection tf4fiτ0 is determined as the total fuel supply amount in step S3, and the injector 1 is adjusted for the total fuel supply amount in step S4.
The ratio of the fuel supply amount in step 5, that is, the injection ratio r, is determined based on a map as shown in FIG. And Steve S
In step S6, the jet tJJJJEIQe-(1-r)·τ0 of the nozzle 13 and the jet fJJJEIQe −r·τ0 of the injector 15 are determined based on the total injection amount τ0 and the injection ratio r, and in step S6, the nozzle 13 and the injector 1
Determine each injection timing TA and T8 of 5 and set these determined values Q.
The nozzle 13 and the injector 15 are operated at the step S7 based on A, T^, Qe, and Ta. As a result, the fuel injected from the injector 15 and well vaporized is sucked into the cylinder 1, and the air-fuel mixture in the cylinder 1 is enriched by the fuel injected from the nozzle 13, thereby improving ignition performance. be able to. On the other hand, in parallel with the generation of this air-fuel mixture, the ignition timing of the first ignition plug 14 and the second ignition plug 16 is determined in step S8, and based on this determined value, the ignition timing of the first ignition plug 14 and the second ignition plug 16 is determined in step S9. The second ignition column 16 is operated to ignite the air-fuel mixture for premix combustion, and the process returns to step S1.

After starting, the engine speed N is set at step S +o.
and the throttle opening P, and after reading the cooling water fAT and the intake negative pressure B@- in step Sn, the intake airflow MA and The injected fuel flow IF is calculated, and in the next step SL3, the cooling water IT is compared with the warm-up completion reference temperature To, and when T≦To (No), it is determined that it is time to warm up, and the process proceeds to step S2, where the above steps are performed. 82 to SI2 are repeated. During this time, as warm-up progresses due to premix combustion, the cooling water WAT rises, and as a result, the injection ratio r decreases as shown in FIG. As a result, the injection m Q a of the injector 15 gradually decreases and the injection 6'f l Q A of the nozzle 13 gradually increases, making the transition from premix combustion to stratified combustion smooth and stable. will be carried out. Furthermore, since stratified combustion is performed in accordance with the degree of progress of warm-up, fuel consumption during warm-up can be reduced.

When the warm-up is completed and it is determined in step S13 that T>TO (YES), the excess air ratio λ is calculated based on the intake air flow rate A and the injection fuel flow rate Fk in the next step SH.

Next, in step S+s, this excess air ratio λ is compared with the reference excess air ratio λ0, and when λ≧λ0 (YES), it is determined that the load is low, and the swirl control valve 17 is closed in step S16. As a result, the intake air flow rate decreases and the air-fuel ratio of the air-fuel mixture in cylinder 1 becomes A-
Ballin is prevented, and a swirl is generated within the cylinder 1, and this swirl causes the nozzle 13 to
The injected fuel is unevenly distributed in the upper part of the cylinder 1.

Thereafter, in step Sry, 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 Sre based on these determined values QA and TA,
This 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 ignition plug 14 is determined in step S+s, and based on this determined value, the ignition timing of the first ignition plug 14 is determined in step Sa.
is operated to ignite the lean 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 S's, N of λ×λ0.

When , it is determined that the load is high, and in step S21, the set opening degree θ of the swirl control pulp 17 is calculated according to the intake air flow mA, and then in step 822, the swirl control pulp 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 an appropriate mixing ratio, and at the time of high load, the swirl control pulp 17 is fully opened 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 823, the jet D4 of the nozzle 13 is
The amount QA, the injection timing TA, the injection amount Qo- of the injector 15, the injection time, and the period T8 are determined. and,
Based on these determined values QA, TA, QB, and T8, the nozzle 13 and the injector 15 are operated in step S24. 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 air-fuel mixture, the ignition timing of the first ignition plug 14 and the second ignition plug 16 is determined in step Sδ, and based on this determined value, in step 82B, the ignition timing of the first ignition plug 14 and the second ignition plug 16 is determined. The two ignition plugs 16 are operated to ignite the air-fuel mixture and cause premix combustion. In this case, since the second ignition plug 16 is disposed approximately in the center of the cylinder bore, the flame propagation 11i11 to the circumferential end of the cylinder 1
1 can be minimized to increase the combustion rate. Also,
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 premixed combustion by improving air utilization while improving combustion stability.

Furthermore, since the nozzle area of the injector 15 is set larger than the nozzle area of the nozzle 13, the injection tJJ amount can be set to a large amount, ensuring engine output at high loads, and the injection amount can be set to a large amount. In some cases, 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 f3a and 8b, and wasteful fuel consumption can be avoided. ”ru.

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 at high loads under severe thermal loads, and the reliability of the engine can be improved.

Next, the determination operation of each injection IOA and QB 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 S2, the engine 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-P1.

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 S5, each injection tAMkQA of the nozzle 13 and injector 15, Injection ratio of Qe x and basic injection! )1
Determine the quantity τ0. Then, in the next step S6, the change ΔP in the throttle opening degree is compared with the acceleration determination reference value ΔPa, and when ΔP>ΔPo (YES), it is determined that the acceleration is occurring, and in step S7, the additional fuel Δτ−k・ΔP( k is a proportionality constant), and when ΔP≦Pa is No, it is determined that it is not the time of acceleration, and the additional fuel Δτ is set to O in step S8.
Then, in step S9, these X, τ0. Based on each value of Δτ, each injection IQ＾(1−x)−τo and QB ratio x11τ0+Δτ are determined. In this way, by injecting fuel from both the nozzle 13 and the injector 15 when the engine is accelerating, 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 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 valve for regulating the intake air flow rate. Therefore, the engine can be made more compact than when separate valves are provided. It is advantageous above.

Note that it is preferable to advance the injection timing TA of the nozzle 13 when the injection flJ amount QA is large in order to maintain good combustibility. Further, it is preferable to accelerate the cold opening and starting in the same way because this can promote atomization of the fuel. Furthermore, if the injection timing Qe 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 fJ4 of the nozzle 13 may be increased in a low load region, 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.

6 and 7 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.

8 and 9 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 at the upper end 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. 10 and FIG. 11 show a fourth embodiment of the present invention, in which a hemispherical combustion chamber 12'' is formed at the end of the piston 4, promoting mixing of the air-fuel mixture and reducing the load. In addition to improving the ignition performance when the combustion chamber 12
It is possible to reduce the heat dissipation of ``'' and maintain the temperature of the combustion chamber 12 high, thereby increasing combustibility.

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 used together with a major inspection. 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 ratio are operated to forcefully premix combustion, and when the engine is warmed up after starting, As the engine temperature increases due to the progress of warm-up, the ratio of "fuel supply from the fuel supply means to the total fuel supply m" is gradually decreased, and the ratio of the fuel supply amount from the nozzle is gradually increased. In addition to improving ignition performance, it is possible to smoothly transition from premix combustion to stratified combustion at 11 o'clock, thereby achieving both maintenance of engine stability and reduction in fuel consumption due to stratified combustion. In addition, when the engine is under low load, the nozzle and spark plug are activated to perform stratified combustion, while when the engine is under high load, the nozzle, fuel supply means, and spark plug are activated to perform premix combustion. While increasing ignitability through uneven distribution and improving combustion stability during premixed combustion, it 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 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.
The figure is a schematic plan view of Figure 1, Figure 3 is a flowchart explaining the basic operation of the CPU, Figure 4 is a diagram showing the injection ratio of the nozzle and injector during startup and warm-up, and Figure 5 is It is a flowchart figure explaining the determination operation of the fuel injection amount at the time of acceleration of CPU. FIG. 6 is a general schematic diagram showing the second embodiment, and FIG. 7 is a schematic plan view of FIG. 6. FIG. 8 is an overall schematic configuration diagram showing the third embodiment;
9 is a schematic plan view of FIG. 8, FIG. 10 is a general schematic diagram showing the fourth embodiment, and FIG. 11 is a schematic plan view of 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, 19...Water temperature sensor, 20...CPU, 2
1... 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 fuel supply means for supplying fuel into the intake passage, an ignition plug disposed in the combustion chamber, an engine temperature detection means for detecting the temperature of the engine, and the nozzle and the fuel supply means when the engine is started. and a control means that receives the output of the engine temperature detection means during warm-up after starting, and reduces the ratio of the amount of fuel supplied by the fuel supply means to the total amount of fuel supplied as the engine temperature rises. Features a spark ignition engine.