JPH0670368B2 - Spark ignition engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a spark ignition type engine, and to an improvement of a structure in which stratified combustion and premixed combustion are performed depending on a load.

(Prior Art) Conventionally, as a spark ignition type engine aiming at reduction of fuel consumption and improvement of output, as disclosed in, for example, Japanese Patent Laid-Open No. 56-151213, a cylinder head is provided in a combustion chamber from an intake stroke. A nozzle for injecting fuel during the compression stroke is arranged, an ignition plug is arranged in the vicinity of the nozzle of the nozzle, and a fuel supply means for supplying fuel to the intake passage is arranged in the intake passage. When the load is low, fuel is injected only from the nozzle to form a stratified lean mixture that becomes rich in the vicinity of the nozzle injection port of the combustion chamber, and this lean mixture is satisfactorily ignited by the spark plug to perform stratified combustion. While reducing fuel consumption by means of fuel injection, when the load is high, fuel is injected from the fuel supply means and the intake air is totally used in the intake passage to form an air-fuel mixture, which is supplied to the combustion chamber by the spark plug. Ignite and premix That so as to improve the engine output by increasing the air utilization rate by burn is known.

(Problems to be Solved by the Invention) However, in the above-described conventional spark ignition type engine, since the nozzle is arranged offset from the substantially central portion of the cylinder bore while avoiding interference with the intake / exhaust valve, this nozzle is disposed. The spark plug arranged in the vicinity of the injection port is also arranged offset from the center of the cylinder bore. For this reason, the flame propagation time to the circumferential edge of the cylinder cannot be minimized during premixed combustion, and knocking easily occurs, resulting in a reduction in engine output. In the meantime, if the spark plug is placed in the approximate center of the cylinder bore away from the nozzle orifice to increase the combustion speed during premixed combustion, during stratified combustion the approximate center of the cylinder bore is Since the lean part is distributed, the ignitability is impaired.

Further, in the case of performing stratified combustion as described above, it is preferable that the fuel injected from the nozzle is unevenly distributed in the vicinity of the nozzle injection port portion in order to improve the ignitability.
Therefore, for example, by making the intake port a helical port and generating a swirl in the cylinder, it is possible to suppress the fuel injected from the nozzle from flowing to the lower part of the cylinder and make it unevenly distributed in the upper part of the cylinder. To be

However, in an engine provided with a swirl generating means such as a helical port, the volume efficiency decreases due to the resistance of the intake port when the load is high, and therefore the engine output cannot be sufficiently improved even by premixed combustion. The problem arises.

The present invention has been made in view of the above points, and an object thereof is a spark ignition type engine in which stratified combustion and premixed combustion are selectively used according to the load as described above. While arranging dedicated spark plugs at appropriate positions and generating swirls in the cylinder only during stratified combustion, while ensuring ignition performance during stratified combustion and combustion stability during premixed combustion, It is to achieve both improvement of fuel efficiency by stratified combustion and improvement of engine output by 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 in at least one of the lower end of the cylinder head and the upper end of the piston. A nozzle for injecting fuel between the intake stroke and the compression stroke is provided in the combustion chamber, and the first nozzle is provided in the vicinity of the injection port of the nozzle.
Place a spark plug. Further, a fuel supply means for supplying fuel is provided in the intake passage, and the second spark plug is arranged substantially in the center of the cylinder bore. Further, swirl generating means for opening and closing the intake passage to adjust the generation of swirl in the cylinder is provided. When the engine has a low load, the nozzle and the first spark plug are operated and the swirl generating means is closed to generate a swirl in the cylinder. On the other hand, when the engine has a high load, the fuel supply means and the second spark plug are operated. And a control means for opening the swirl generating means so as to suppress the generation of swirl in the cylinder.

(Operation) With the above configuration, in the present invention, when the engine is under a low load, the nozzle and the first spark plug are operated by the control means and the swirl generating means is closed, and the swirl generating means swirls the cylinder. Is generated,
Fuel is injected into the swirl from the nozzle between the intake stroke and the compression process, so that this fuel is unevenly distributed in the upper part of the cylinder together with the swirl, and the vicinity of the nozzle injection port becomes rich, thus forming a stratified lean mixture. Qi is formed. Then, of the stratified lean mixture, the first mixture is arranged in the vicinity of the nozzle injection port where the rich mixture is unevenly distributed.
The lean air-fuel mixture is surely ignited by ignition of the spark plug, and stratified combustion is performed. On the other hand, when the engine is under high load, the control means operates the fuel supply means and the second spark plug and the swirl generation means opens, and the fuel supply means uses the entire intake air in the intake passage to mix the air-fuel mixture. This air-fuel mixture is smoothly sucked into the cylinder without resistance due to the opening operation of the swirl generating means to enhance the volumetric efficiency, and the second spark plug arranged substantially in the center of the cylinder bore is ignited for faster combustion. Premixed combustion of the air-fuel mixture is performed at a speed.

(Example) Hereinafter, the Example of this invention is described based on drawing.

1 and 2 show a first embodiment of the present invention. Reference numeral 1 denotes a cylinder formed by a cylinder block 2 and a cylinder head 3, and a piston 4 is slidably fitted in the cylinder 1. The cylinder head 3
First and second intake ports 5 and 6 and an exhaust port 7 which open to the cylinder 1 are formed therein. The downstream ends of the first and second intake passages 8a and 8b branched from the main intake passage 8 in a bifurcated manner are individually connected to the first and second intake ports 5 and 6, respectively, and are sucked into the cylinder 1. I am trying to supply air. Further, an upstream end of an exhaust passage 9 is connected to the exhaust port 7 so that exhaust gas from the cylinder 1 is exhausted. 10 and 10 are intake valves provided in the first and second intake ports 5 and 6, and 11
Is an exhaust valve provided in the exhaust port 7.

A substantially concave combustion chamber 12 that opens into the cylinder 1 is formed on the exhaust port 7 side of the lower end of the cylinder head 3.
A fuel injection nozzle is provided in the combustion chamber 12 of the cylinder head 3.
13 is provided and operates when the engine has a low load to inject fuel into the combustion chamber 12 between the intake stroke and the compression stroke of the cylinder 1 to enrich the vicinity of the nozzle of the nozzle 13 in the cylinder 1. It is designed to generate a stratified lean mixture. In the combustion chamber 12, a first spark plug 14 that operates when the engine load is low is arranged near the nozzle of the nozzle 13.

On the other hand, an injector 15 as a fuel supply means is arranged immediately upstream of the branch portion of the main intake passage 8 and operates by premixed combustion to inject and supply fuel into the main intake passage 8. A mixture is generated in the intake passage 8. A second spark plug 16 that operates during premixed combustion is arranged in the cylinder head 3 in the substantially central portion of the cylinder bore.

The nozzle area of the nozzle 13 is set to be smaller than the nozzle area of the injector 15, and the spray angle of the nozzle 13 is set to be larger than the spray angle of the injector 15, from the nozzle portions of the nozzle 13 and the injector 15. The fuel is appropriately injected according to the combustion method.

Further, the first spark plug 14 adopts a burnt type having a low heat value, while the second spark plug 16 adopts a cold type having a high heat value, so that a spark is stably generated depending on the combustion method. I am trying to do it.

Further, a swirl control valve 17 as a swirl generating means is arranged in the main intake passage 8 upstream of the injector 15 so as to be connected to an actuator 18, and the main intake passage 8 upstream of the swirl control valve 17 and the first intake port 5 are provided. A bypass passage 19 communicates with the first intake passage 8a immediately upstream of the swirl control valve when the engine is under a low load due to the operation of the actuator 18.
Swirl is generated in the cylinder 1 by closing 17 and passing the intake air only through the bypass passage 19 to increase the flow velocity.
17 is opened to a predetermined opening to supply the cylinder 1 with intake air at a flow rate according to the engine speed and load.

The nozzle 13, the injector 15, the first and second spark plugs 14 and 16 and the actuator 18 are connected to the CPU 20, and the first and second spark plugs 14 and 16 are respectively connected via igniters 22a and 22b. The CPU 20 is connected to the CPU 20, to which signals of engine speed N, throttle opening P, cooling water temperature T and intake negative pressure B are input, and when the engine is under a low load, the nozzle 13 and the first While activating the spark plug 14 and closing the swirl control valve 17,
When the engine is under heavy load, the injector 15 and the second spark plug 16 are operated and the swirl control valve is activated.
A control means 21 is configured to open 17 to a predetermined opening.

Next, the operation of the control means 21 will be described based on the flow chart shown in FIG. 3. After the start, the engine speed N and the throttle opening P are read in step S ₁ ,
After Step S ₂ is loaded the coolant temperature T and the intake negative pressure B, it calculates these input values N, P, T, the intake air flow A and the injection fuel flow rate F in step S ₃ based on B, the following In step S _{4 of} , 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 S ₅ , the excess air ratio λ is compared with the reference excess air ratio λ _{0. If} YES in λ ≧ λ ₀ , it is determined that the load is low, and in step S ₆ , the swirl control valve is operated.
Close 17 As a result, the intake air flow rate is reduced and the air-fuel ratio of the air-fuel mixture in the cylinder 1 is prevented from becoming over lean, and swirl is generated in the cylinder 1, which causes the fuel injected from the nozzle 13 to be injected. It is unevenly distributed in the upper part of the cylinder 1.

Then, in step S ₇ , the injection amount Q _A and the injection timing T _A of the nozzle 13 are determined. Then, based on these determined values Q _A and T _A , in step S ₈ , the nozzle 13 is operated to inject fuel, so that the injected fuel and the swirl enrich the vicinity of the nozzle injection port. A stratified lean mixture is produced. On the other hand, in parallel with the production of this lean air-fuel mixture, in step S ₉ , the first
Determining the ignition timing of the ignition plug 14, by actuating the first ignition plug 14 at step S ₁₀ is combusted stratified ignite the lean mixture on the basis of the decision value. In this case, since the first spark plug 14 is arranged in the vicinity of the nozzle injection port where the rich air-fuel mixture is unevenly distributed, the lean air-fuel mixture is surely ignited. Therefore, it is possible to reduce fuel consumption due to stratified combustion while improving ignitability.

Moreover, 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 air-fuel mixture can be improved. Moreover, since the spray angle of the nozzle 14 is set to be larger than the spray angle of the injector 15, atomization of the injected fuel is further promoted and diffusion of the atomized fuel in the cylinder direction is promoted so that the lean air-fuel mixture is formed. The flammability can be further improved.

Furthermore, since the first spark plug 14 is of a burnt type having a low heat value, it is possible to stably form a flame kernel despite a lean mixture, and to realize good ignitability. You can In this case, setting the arc time of the first spark plug 14 longer than the arc time of the second spark plug 16 is preferable because it improves the ignitability during stratified combustion. Further, since the first spark plug 14 is arranged in the deeply recessed combustion chamber 2, turbulence due to the squish flow is not generated around the first spark plug 14, which contributes to improvement of ignitability. it can.

On the other hand, in step S ₅ , when NO of λ <λo, it is determined that it is not under a low load, and in step S ₁₁ , the set opening θ of the swirl control valve 17 is calculated according to the intake air flow rate A, and then the step Set the swirl control valve 17 to the opening θ with S ₁₂ . As a result, the air-fuel mixture supplied to the cylinder 1 can be accurately controlled to an appropriate air-fuel ratio, and at the time of high load, the swirl control valve 17 is opened so that the intake air is smoothly drawn into the cylinder 1 without resistance. Since the volumetric efficiency is increased, the engine output can be improved.

Then, in step S ₁₃ , the injection amount Q _B and the injection timing T _B of the injector 15 are determined. Then, based on these determined values Q _B , T _B , in step S ₁₄ , the injector 1
By operating 5 to inject the fuel, the entire intake air in the main intake passage 8 is used to generate an air-fuel mixture, and the air-fuel mixture is sucked into the cylinder 1. In parallel with the generation of this gas mixture, in a step S _15, the second spark plug 1
Ignition timing of 6 is determined, and based on this determined value, step S
_{At 16} the second spark plug 16 is operated to ignite the above mixture and premix combustion. In this case, since the second spark plug 16 is arranged substantially in the center of the cylinder bore, the flame propagation time to the circumferential end of the cylinder 1 can be minimized and the combustion speed can be increased. Therefore, it is possible to improve the engine output by premix combustion by improving the air utilization rate while improving the combustion stability.

Further, since the injection port area of the injector 15 is set larger than the injection port area of the nozzle 13, the injection amount can be set to a large value, the engine output at high load can be secured, and the injection amount can be increased. Even at this time, the injection pulse width can be shortened as much as possible to improve the control accuracy of the injection timing. Moreover, since the spray angle of the injector 15 is set to be smaller than the spray angle of the nozzle 13, it is possible to prevent the injected fuel from adhering to the intake passages 8a and 8b, and to reduce waste of fuel consumption. .

Further, since the second spark plug 16 is of a cold type having a high heat value, it is possible to prevent melting damage of the second spark plug 16 during premixed combustion with high heat generation. This is particularly advantageous at high loads, which are subject to severe heat loads, and can improve engine reliability.

Next, the operation of determining the injections Q _A and Q _B of the nozzle 13 and the injector 15 during acceleration of the engine will be described based on the flowchart shown in FIG. 4. After the start, in step S ₁ , the engine speed N ₁ And the throttle opening P ₁ are read, then the engine speed N ₂ and the throttle opening P ₂ after a lapse of a short time are read in step S ₂ , and the change ΔP = P ₂ −P ₁ of the throttle opening in step S _3. Ask for.

Next, in step S ₄ , the swirl control valve opening θ corresponding to the engine speed N ₂ and the throttle opening P ₂ is determined based on the map, and in step S ₅ , the nozzle 13 and the injector 15 of the nozzle 15 based on the map are determined. Each injection quantity Q _A , Q
The injection ratio _{X of B} and the basic injection amount τo are determined. Then, the variation [Delta] P of the throttle opening degree as compared with the acceleration criterion value .DELTA.Po in the next step S _6, the additional fuel in step S ₇ it is determined that the time of acceleration when the YES of ΔP> ΔPo Δτ =
While k · ΔP (k is a proportional constant) is set, ΔP ≦ Po
When the N0 is judged not to be the time of acceleration and 0 additional fuel Δτ in step S _8, these _X in the subsequent step S _{9, τo,}
Based on each value of Δτ, each injection amount Q _A = (1− _X ) · τ o,
Determine Q _B = _X · τo + Δτ. In this way, when the engine is accelerated, the fuel can be injected from both the nozzle 13 and the injector 15, so that the transition from the stratified combustion to the premixed combustion can be smoothly performed. 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 fully opened to supply the intake air amount commensurate with the acceleration. Therefore, the acceleration performance can be improved. Further, since the swirl control valve 17 opens during acceleration so that swirl is not generated in the cylinder 1, it is advantageous to inject the additional fuel Δτ from the injector 15 instead of the nozzle 13 in terms of mixing the air-fuel mixture. is there.

Further, in the above embodiment, the swirl control valve
Since 17 is used not only as a swirl generating means but also as a valve for adjusting the intake air flow rate, it is advantageous in achieving compactness of the engine as compared with providing a separate valve.

The injection timing T _A of the nozzle 13 is preferably advanced when the injection amount Q _A is large, from the viewpoint of maintaining good fuelability. In addition, it is preferable to accelerate the fuel even during cold or starting, because atomization of the fuel can be promoted. Furthermore, if the injection timing T _B of the injector 15 is set to the intake stroke that maximizes the intake air flow velocity, a homogeneous air-fuel mixture can be obtained.

Further, as in the present embodiment, the nozzle 13 and the injector 15 are not completely switched, but the fuel injection amount ratio of the nozzle 13 is increased when the load is low and the fuel injection amount ratio of the nozzle 13 is decreased in the high load region. You may Furthermore, depending on the opening of the swirl control valve 17, the nozzle 13
The fuel supply ratio to the injector 15 may be changed. Further, in the high load region, both the first and second spark plugs 14 and 16 may be ignited, so that ignition can be surely performed.

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 the 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, and the turbulence can accelerate the initial flame propagation after ignition.

7 and 8 show a third embodiment of the present invention, which is applied to a pent 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 portion of the piston 4. In the present embodiment, since the intake / exhaust valves 10 and 11 are arranged to be inclined, the intake / exhaust ports 5 and 7 can be set to have a large diameter, and the volume can be increased. The efficiency can be improved.

Further, FIGS. 9 and 10 show a fourth embodiment of the present invention in which a hemispherical combustion chamber 12 is formed at the upper end portion of the piston 4 to promote mixing of the air-fuel mixture and to reduce the load. The ignitability can be improved, and the heat dissipation of the combustion chamber 12 can be reduced to maintain the temperature of the combustion chamber 12 high and increase the combustion chamber.

Further, the present invention is not limited to the above-described embodiments, and not only the first spark plug 14 but also the second spark plug 16 can be used in the combustion chamber 12
May be arranged so as to face each other, which is advantageous when both spark plugs are used together when the load is low. Furthermore, the present invention can be applied 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 described above, according to the spark ignition engine of the present invention, when the engine load is low, the swirl formed in the cylinder due to the closing operation of the swirl generating means changes from the intake stroke to the compression stroke. Fuel is injected from the nozzle between the nozzles, and this fuel is unevenly distributed in the upper part of the cylinder along with the swirl to form a stratified lean mixture that makes the vicinity of the nozzle injection port rich, and the first ignition disposed near the nozzle injection port The lean mixture is stratified and burned by igniting the plug, while at the time of high engine load, the mixture created by using the entire intake air in the intake passage by the fuel supply means is smoothly opened by the swirl generation means to open the cylinder. It is sucked into the interior of the cylinder bore and ignited by the second spark plug arranged substantially in the center of the cylinder bore to premix and burn the air-fuel mixture. Enhances ignitability by optimizing the uneven distribution of fuel and ignition position, and enhances combustion stability by optimizing the ignition position during premixed combustion, while reducing fuel consumption by stratified combustion at low load and reducing fuel consumption at high load. It is possible to achieve both improvement of engine output by premixed combustion with improved volumetric efficiency.

[Brief description of drawings]

The drawings illustrate an embodiment of the present invention, FIGS. 1 to 4 show a first embodiment of the present invention, and FIG.
1 is a schematic plan view of FIG. 1, FIG. 3 is a flow chart for explaining the basic operation of the CPU, and FIG. 4 is a flow chart for explaining the operation of determining the fuel injection amount during acceleration of the CPU. FIG. 5 is an overall schematic configuration diagram showing a second embodiment, FIG.
The figure is a schematic plan view of FIG. 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. It is a model top view of a figure. 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 ... First spark plug, 15 ... Injector, 16 ...
Second spark plug, 17 ... Swirl control valve, 20 ...
... CPU, 21 ... control means.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location F02M 63/00 P 7825-3G 69/00 360 B 7825-3G C 7825-3G F02P 15/08 301 C 302 A (72) Inventor Akashi Nagao 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) Reference JP 56-151213 (JP, A) JP 52-3907 (JP) , A) JP-A-60-36721 (JP, A)

Claims (1)

[Claims] 1. A substantially concave combustion chamber formed in at least one of a cylinder head lower end portion and a piston upper end portion so as to open into a cylinder, and fuel is injected into the combustion chamber between an intake stroke and a compression stroke. The nozzle, the first spark plug arranged in the vicinity of the injection port of the nozzle, the fuel supply means for supplying fuel into the intake passage, the second spark plug arranged substantially in the center of the cylinder bore, and the intake passage. And a swirl generating means for opening and closing to adjust the generation of swirl in the cylinder, and closing the swirl generating means so as to operate the nozzle and the first spark plug and generate swirl in the cylinder when the engine is under a low load. On the other hand, when the engine is under heavy load, the fuel supply means and the second spark plug are activated and the generation of swirl in the cylinder is suppressed. Spark-ignition engine, characterized in that the serial swirl generating means provided with control means for opening operation.