JP2644213B2 - Spark ignition engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a spark-ignition engine, and more particularly to an improvement in which a stratified combustion and a premixed combustion are performed according to 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, JP-A-56-151213, a nozzle opening in a cylinder head is formed in a combustion chamber. A nozzle for injecting fuel from the injection port into the combustion chamber during an intake stroke to a compression stroke; an ignition plug disposed near the injection port of the nozzle; A fuel supply means for supplying fuel is provided in the passage, and at low load, fuel is injected only from the nozzle to form a stratified lean mixture in which the vicinity of the nozzle orifice of the combustion chamber becomes rich. While fuel efficiency is reduced by igniting the air-fuel mixture with the ignition plug and stratifying combustion, fuel is also injected from the fuel supply means at high load, and the intake air is entirely used in the intake passage to mix. Form the mind This air-fuel mixture is supplied to a combustion chamber, mixed with a lean air-fuel mixture generated by fuel injected from a nozzle, ignited by an ignition plug and premixed to increase air utilization and improve engine output. What has been known is known.

(Problems to be Solved by the Invention) By the way, in such a spark ignition type engine,
During start-up and warm-up operation when the temperature of the engine is low, fuel is supplied from both the nozzle and the fuel supply means to promote the vaporization of fuel, so that ignitability at start-up and warm-up operation (when cold) It is conceivable to improve the fuel stability.

However, in the above proposal, stratified combustion cannot be performed at the time of startup and warm-up operation (during cold) because fuel is supplied from both the nozzle and the fuel supply means, so that fuel efficiency can be reduced. Can not. Moreover, when the fuel supply from the fuel supply means is stopped and the fuel supply amount from the nozzle is increased to shift to stratified combustion at the completion of warm-up, a response delay of the fuel supply from the nozzle and a sharp increase in the air utilization rate occur. 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 circumstances, and an object of the present invention is to provide a spark-ignition engine in which stratified charge combustion and premixed combustion are selectively used depending on the load as described above. In some cases, premixed combustion is forcibly performed, and during warm-up operation after startup, the ignitability at startup is improved by gradually shifting from premixed combustion to stratified combustion as the warm-up progresses. An object of the present invention is to achieve both a reduction in fuel consumption during operation (during cold) and stability of the engine.

(Means for Solving the Problems) In order to achieve the above object, a solution of the present invention is to form a substantially concave combustion chamber that opens into a cylinder at at least one of a lower end of a cylinder head and an upper end of a piston, A nozzle having an injection port opening into the combustion chamber and injecting fuel from the injection port into the combustion chamber at least during an intake stroke and a compression stroke at a low load is provided. Also,
Fuel supply means for supplying fuel into the intake passage at high load is provided, and an ignition plug is disposed in the combustion chamber. Further, an engine temperature detecting means for detecting the temperature of the engine is provided. When the engine is started, the nozzle and the fuel supply unit are operated. During the warm-up operation after the start, the output of the engine temperature detection unit is received. The configuration is such that control means for reducing the ratio of the amount is provided.

(Operation) According to the above configuration, in the present invention, when the engine is started, the fuel supply means operates, the fuel is satisfactorily vaporized, and the nozzle operates to enrich the mixture, thereby improving ignitability. During the warm-up operation after the start, the ratio of the fuel supply amount by the fuel supply unit to the total fuel supply amount gradually decreases as the engine temperature rises due to the progress of the warm-up, and the ratio of the fuel supply amount by the nozzle gradually increases. From the premixed combustion performed by igniting the air-fuel mixture generated by utilizing the entire intake air in the intake passage by the fuel supply means with an ignition plug, the stratified lean mixing generated by the nozzle A stable and smooth transition to stratified combustion performed by igniting the gas with an ignition plug is achieved, and the gradual transition to stratified combustion reduces fuel consumption during warm-up operation. Further, after completion of warm-up, when the engine is under a low load, the nozzle and the ignition plug operate to perform stratified combustion, while at a high load, the nozzle, the fuel supply unit and the ignition plug operate to generate the stratified combustion. The mixture and the lean mixture generated by the nozzle are ignited by an ignition plug to perform premix combustion.

(Example) Hereinafter, an example of the present invention will be described with reference to 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, and a piston 4 is slidably fitted in the cylinder 1. The cylinder head 3 is formed with first and second intake ports 5, 6 and an exhaust port 7, which open to the cylinder 1, respectively. The first and second intake ports 5 and 6 are connected to the main intake passage 8 from the main intake passage 8.
The downstream ends of the first and second intake passages 8a and 8b, which are branched into a shape, are individually connected to supply intake air to the cylinder 1. In addition, the exhaust port 7
Is connected to the upstream end of an exhaust passage 9.
The exhaust gas from is discharged. In addition, 10,10
Are intake valves provided in the first and second intake ports 5 and 6, 1
Reference numeral 1 denotes an exhaust valve provided at the exhaust port 7.

On the exhaust port 7 side of the lower end of the cylinder head 3, a substantially concave combustion chamber 12 opening to the cylinder 1 is formed. A fuel injection nozzle 13 having an injection port opening into the combustion chamber is provided in the combustion chamber 12 of the cylinder head 3 and injects fuel into the combustion chamber 12 during the intake stroke and the compression stroke of the cylinder 1. Thus, a stratified lean mixture is generated in the cylinder 1 so that the vicinity of the injection port of the nozzle 13 becomes rich. Further, a first spark plug 14 is disposed in the combustion chamber 12 near the injection port of the nozzle 13.

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

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 appropriately injected according to the combustion method.

The first spark plug 14 is of a burnt type having a low heat value, while the second spark plug 16 is of a cold type having a high heat value, and stably generates a spark according to the combustion method. I am trying to do it.

Further, a swirl control valve 17 is provided in the main intake passage 8 upstream of the injector 15 in connection with the actuator 18, and a first swirl control valve 17 upstream of the swirl control valve 17 and a first swirl control valve 17 immediately upstream of the first intake port 5. The intake passage 8a is communicated with the intake passage 8a by a bypass passage 8c. When the engine 18 operates at a low load, the swirl control valve 17 is closed to allow the intake air to flow only through the bypass passage 8c to increase the flow velocity, thereby reducing the flow rate in the cylinder 1. The swirl control valve 17 is set to a predetermined opening at a high load to supply the cylinder 1 with intake air at a flow rate according to the engine speed and the load.

A water temperature sensor 19 is mounted on the side wall of the cylinder block 2 as engine temperature detecting means for detecting the temperature of the engine based on the engine cooling water temperature T.

The nozzle 13, the injector 15, the actuator 18, and the water temperature sensor 19 are connected to the CPU 20, and the first and second spark plugs 14, 16 are respectively connected to the igniter 22.
It is connected to the CPU 20 via a and 22b. Each signal of the engine speed N, the throttle opening P, the ignition switch signal I, and the intake negative pressure B is input to the CPU 20, and when the engine is started, the nozzle 13 and the injector 15 are operated to warm up after the start. During the operation of the engine, the output of the water temperature sensor 19 is received, and as the engine temperature rises, the ratio of the fuel supply amount by the injector 15 to the total fuel supply amount is reduced.
13 and the first spark plug 14 are activated and the swirl control valve 17 is closed.
The control means 21 is configured to operate the first spark plug 14, the injector 15, and the second spark plug 16 and set the swirl control valve 17 to a predetermined opening.

Next, will be described with reference to a flowchart shown in FIG. 3 the operation of the control unit 21, after starting, step S ₁
To determine whether the engine is starting or not, and YES when starting
When the swirl control valve in step S ₂
17 after the determining the total injection amount tau _O as the total fuel supply amount in step S ₃ after fixing to the predetermined opening degree, the proportion clogging injection rate of the fuel supply amount of the injector 15 to the total fuel supply amount in step S ₄ r is determined based on a map as shown in FIG. Then, = injection amount Q _A of the nozzle 13 based on the total injection amount tau _O and injection ratio r in step S ₅ (1-
r) · τ _O and determines the injection amount Q _B = r · r _O of the injector 15, to determine the injection timing T _A of the nozzle 13 and the injector 15, the T _B in step S _6, these decision values Q _A , T _A , Q _B , T _B
Nozzle 13 and the injector 15 at step S ₇ on the basis of the
Activate This allows the injector to
The fuel injected from 15 and well vaporized is sucked into the cylinder 1, and the fuel injected from the nozzle 13 enriches the air-fuel mixture in the cylinder 1, so that the ignitability can be improved. In parallel with the generation of this gas mixture, first at step S ₈ the spark plug 14 and the second
Ignition spark timing of plug 16 was determined, by operating the first spark plug 14 and the second spark plug 16 in step S ₉ to premixed combustion by igniting the air-fuel mixture on the basis of the decision value, the step S ₁ Return to

Then, after starting reads the engine speed N and the throttle opening P in step S _10, after having been read the cooling water temperature T and the intake negative pressure B at step S _11, these input values N,
P, T, and calculates the intake air flow A and the injection fuel flow rate F in step S ₁₂ based on B, the cooling water temperature T in the next step S ₁₃
The comparison with the warm-up completion reference temperature T _O, the process proceeds to step S ₂ it is determined that when T ≦ T _O of the NO is during warm-up operation, repeated operation of step S ₂ to S ₁₂ described above. During this period, the warm-up progresses due to the premixed combustion, so that the cooling water temperature T rises, and accordingly, the injection ratio r decreases as shown in FIG. Thus, during the warming up after starting, to increase the injection quantity Q _A of the nozzle 13 is gradually along with the injection amount Q _B of the injector 15 decreases gradually shift to stratified combustion from homogeneous charge combustion Performed smoothly and stably. In addition, since stratified charge combustion is performed in accordance with the degree of progress of warm-up, fuel consumption during warm-up operation can be reduced.

When it is determined as YES in T> T _O at step S ₁₃ in the warm-up is completed, the intake air flow A in the next step S ₁₄
Then, the excess air ratio λ is calculated based on the injection fuel flow rate F.

Then, the excess air ratio lambda is compared with the reference air ratio lambda _O in step S _15, when the YES of lambda ≧ lambda _O closing the swirl control valve 17 in step S ₁₆ it is determined that the time of low load . This prevents the intake air flow rate from decreasing and the air-fuel ratio of the air-fuel mixture in the cylinder 1 from becoming overlean, and also generates swirl in the cylinder 1, and the swirl causes the fuel injected from the nozzle 13 to flow. It will be unevenly distributed in the upper part in the cylinder 1.

Thereafter, in step S _17, the injection amount Q _A of the nozzle 13
And the injection timing T _A are determined. And these determined values
By based on Q _A and T _A actuates the nozzle 13 at step S ₁₈ to inject fuel, the vicinity of the nozzle injection port portion by the the injected fuel and the swirl is stratified like lean as becomes rich Generated. In parallel with the generation of the lean mixture, in step S _19, the first
Determining the ignition timing of the ignition plug 14, by actuating the first ignition plug 14 at step S ₂₀ is combusted stratified ignite the lean mixture on the basis of the decision value. In this case, since the first spark plug 14 is disposed near the nozzle orifice where the rich mixture is unevenly distributed, the lean mixture is reliably ignited. Therefore, at low load, fuel efficiency can be reduced by stratified combustion while improving ignitability.

Further, since the injection port area of the nozzle 13 is set smaller than the injection port area of the injector 15, the atomization of the injected fuel is promoted, and the combustibility of the lean mixture can be improved. In addition, the spray angle of the nozzle 14 is
Since the spray angle is set to be larger than 15, the atomization of the injected fuel is further promoted and the diffusion of the atomized fuel in the cylinder direction is further promoted to further improve the combustibility of the lean mixture. Can be.

Further, since the first spark plug 14 is of a burn type having a low heat value, a flame kernel can be formed stably irrespective of a lean air-fuel mixture, thereby realizing good ignitability. Can be. In this case, the arc time of the first spark plug 14 is set to the second
It is preferable to set the arc time longer than the arc time of the ignition plug 16 because ignitability during stratified combustion is improved. Further, since the first spark plug 14 is disposed in the recessed substantially concave combustion chamber 2, no turbulence is generated around the first spark plug 14 due to the squish flow, which contributes to the improvement of ignitability. it can.

On the other hand, in step S _15, calculated in accordance with the lambda <lambda _O of NO inhalation air flow A to set opening θ of the swirl control valve 17 in step S ₂₁ it is determined that is at a high load at the time of, and then step setting the swirl control valve 17 to the opening θ at S _22. As a result, the air-fuel mixture supplied to the cylinder 1 can be accurately controlled to an appropriate mixing ratio, and at high load, the swirl control valve 17 is fully opened, and the intake air is smoothly sucked into the cylinder 1 without resistance. Since the volumetric efficiency is improved, it is possible to improve the engine output.

Thereafter, in step S _23, the injection amount Q _A of the nozzle 13
And determining the injection amount Q _B and the injection timing T _B of the injection timing T _A and the injector 15. Then, these determined values Q _A , T _A ,
Q _B, to actuate the nozzle 13 and the injector 15 at step S ₂₄ based on the T _B. As a result, at high load, a fuel-air mixture is generated by using the entire intake air in the main intake passage 8 by fuel injection from the injector 15, and the air-fuel mixture is sucked into the cylinder 1 and It mixes with the lean mixture generated by the injected fuel. In parallel with the generation of this gas mixture, in a step S _25, the ignition timing of the first ignition plug 14 and the second spark plug 16 is determined, the first ignition plug at Step S ₂₆ based on the determination value 14 Then, the second spark plug 16 is operated to ignite the air-fuel mixture to perform premix combustion. In this case, since the second spark plug 16 is disposed substantially at the center of the cylinder bore, the flame propagation time to the peripheral end of the cylinder 1 can be minimized and the combustion speed can be increased. Also,
Since the first spark plug 14 also operates, the combustion speed of the air-fuel mixture in the recessed combustion chamber 12 can be increased. Therefore, it is possible to improve the engine utilization by the premixed combustion by improving the air utilization rate while improving the combustion stability.

Further, since the injection hole area of the injector 15 is set to be larger than the injection hole area of the nozzle 13, the injection amount can be set to be large, the engine output under a high load can be secured, and when the injection amount is large. In addition, the injection pulse width can be made as short as possible to improve the control accuracy of the injection timing. In addition, since the spray angle of the injector 15 is set 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. .

In addition, since the second spark plug 16 is of a cold type having a high heat value, it is possible to prevent the second spark plug 16 from being melted during premixed combustion that generates a large amount of heat. This is particularly advantageous at high loads under severe heat loads, and can increase the reliability of the engine.

Then, the injection amount Q _A of the nozzle 13 and the injector 15 during acceleration of the engine, to be described with reference to the flowchart indicating the determined operation of the Q _B in FIG. 5, after the start, the engine speed at step S ₁ N ₁ and the throttle opening P ₁ are read, and then in step S ₂ , the engine speed N ₂ and the throttle opening P ₂ after a lapse of a minute time are read, and step S ₃
Is used to obtain the change amount of the throttle opening ΔP = P ₂ −P ₁ .

Next, determine the swirl control valve opening θ corresponding to the engine speed N ₂ and the throttle opening P ₂ based on the map in step S _4, the nozzle 13 and the injector 15 based on the map in step S ₅ Each injection amount Q _A , Q
Determining a fuel injection ratio x and the basic injection amount tau _O of _B. Then, the variation [Delta] P of the throttle opening degree as compared with the acceleration criterion value [Delta] P _O at the next step S _6, [Delta] P> added in step S ₇ it is determined that the time of acceleration when the YES of [Delta] P _O fuel .DELTA..tau =
k · ΔP (k is a proportionality constant), while ΔP ≦ _PO
Is judged not to be the time of acceleration when the N0 and 0 additional fuel Δτ in step S _8, these x thereafter step S _9, tau _O, delta
Based on each value of τ, each injection amount Q _A = (1-x) · τ _O , Q _B =
x · τ _O + Δτ is determined. As described above, when the engine is accelerated, the transition from stratified combustion to premixed combustion can be smoothly performed by injecting fuel from both the nozzle 13 and the injector 15. In addition, since the additional fuel Δτ is added from the injector 15 and injected, it is possible to prevent the air-fuel mixture from becoming overlean even when the swirl control valve 17 is almost fully opened in order to supply an intake air amount commensurate with acceleration. And acceleration can be improved. In addition, when the swirl control valve 17 is opened during acceleration, no swirl is generated in the cylinder 1. Therefore, injecting the additional fuel Δτ from the injector 15 instead of the nozzle 13 is advantageous from the viewpoint of mixing the air-fuel mixture. is there.

Further, in the above-described embodiment, the swirl control valve 17 is used not only as a means for generating swirl but also as a valve for adjusting the intake air flow rate. It is advantageous.

It is preferable that the injection timing T _A of the nozzle 13 be advanced when the injection amount Q _A is large, from the viewpoint of maintaining good flammability. Further, it is preferable that the fuel gas is accelerated at the time of cold start or at the time of starting, because the atomization of the fuel can be promoted. Moreover, the injection timing Q _B of the injector 15, it is possible to obtain a homogeneous air-fuel mixture is set to the intake stroke where the intake air flow rate is the highest.

Further, the nozzle 13 and the injector 15 are not completely switched as in the present embodiment. For example, the fuel injection amount ratio of the nozzle 13 is increased at a low load, and the nozzle 13 is increased at a high load region.
May be reduced. further,
Depending on the opening of the swirl control valve 17, the nozzle
The fuel supply ratio to the injector 13 and the injector 15 may be changed.

FIGS. 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 ignition plug 14 is arranged at the lower end of the flat cylinder head 3. The squish flow generated in the cylinder 1 causes turbulence around the first spark plug 14, and this turbulence can speed up the initial flame propagation after ignition.

FIGS. 8 and 9 show a third embodiment of the present invention. The present invention is applied to a pent roof type engine in which a lower end surface of a cylinder head 3 is formed in a conical shape and a combustion chamber 12 "is formed at an upper end portion of a piston 4. In this embodiment, since the intake and exhaust valves 10 and 11 are disposed at an angle, the diameters of the intake and exhaust ports 5 and 7 can be set large, and the volume can be reduced. Efficiency can be improved.

10 and 11 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 to promote mixing of the air-fuel mixture to reduce the load at low load. The ignitability can be improved, and the heat radiation of the combustion chamber 12 can be reduced to maintain the temperature of the combustion chamber 12 high to enhance the flammability.

Further, the present invention is not limited to the above embodiments. Not only the first spark plug 14 but also the second spark plug 16 is used in the combustion chamber.
It may be arranged so as to face 12 and this is advantageous when both spark plugs are used together at a low load. Further, the present invention is 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 described above, according to the spark ignition engine of the present invention, when the engine is started, the nozzle and the fuel supply means are operated to forcibly perform premix combustion, and the warm-up operation after the start is performed. At times, the ratio of the fuel supply amount of the fuel supply means to the total fuel supply amount was gradually decreased and the ratio of the fuel supply amount of the nozzles was gradually increased with an increase in the engine temperature due to the progress of warm-up. Ignitability can be improved, and the transition from premixed combustion to stratified combustion during the warm-up operation can be smoothly performed to maintain both engine stability and reduce fuel consumption due to stratified combustion. When the engine is under low load, the nozzle and ignition plug are operated to perform stratified combustion,
By operating the nozzle, fuel supply means and spark plug at high load to perform premixed combustion, during stratified combustion, ignitability is increased by uneven distribution of fuel, and during premixed combustion, combustion stability is increased, while low load is applied. It is possible to achieve both a reduction in fuel efficiency due to stratified combustion at the time and an improvement in engine output due to premixed combustion with increased volumetric efficiency at a high load.

[Brief description of the drawings]

The drawings illustrate an embodiment of the present invention, FIGS. 1 to 5 show a first embodiment of the present invention, FIG.
FIG. 3 is a schematic plan view of FIG. 1, FIG. 3 is a flowchart for explaining the basic operation of the CPU, FIG. 4 is a diagram showing the injection ratio between the nozzle and the injector at the time of startup and warm-up operation, FIG. FIG. 5 is a flowchart illustrating an operation of determining a fuel injection amount when the CPU is accelerating. FIG. 6 is an overall schematic configuration diagram showing a second embodiment, and FIG. 7 is a schematic plan view of FIG. FIG. 8 is an overall schematic configuration diagram showing a third embodiment,
9 is a schematic plan view of FIG. 8, FIG. 10 is an overall schematic configuration 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 First spark plug, 15 Injector, 16
2nd spark plug, 19 ... water temperature sensor, 20 ... CPU, 21 ... control means.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akiyoshi Nagao 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Corporation (56) References JP-A-56-151213 (JP, A) JP-A Sho 51-2809 (JP, A) JP-A-60-30439 (JP, A) JP-A-60-182330 (JP, A) JP-A-58-137843 (JP, U)

Claims (1)

(57) [Claims] 1. A combustion chamber having a substantially concave combustion chamber formed in at least one of a lower end portion of a cylinder head and an upper end portion of a piston so as to open into a cylinder, and an injection port opening to the combustion chamber. A nozzle for injecting fuel from the injection port into the combustion chamber from a stroke to a compression stroke, fuel supply means for supplying fuel into the intake passage at a high load, and an ignition plug disposed in the combustion chamber;
An engine temperature detecting means for detecting the temperature of the engine, the nozzle and the fuel supply means are operated when the engine is started, and the output of the engine temperature detecting means is received during a warm-up operation after the start of the engine. A control unit for reducing a ratio of a fuel supply amount by the fuel supply unit to the fuel supply amount.