JP2007285205A - Cylinder injection type spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress collision of an injected fuel with a cylinder bore during the stratified charge combustion and to realize excellent stratified charge combustion by increasing the combustion speed in a cylinder injection type spark ignition internal combustion engine for performing the stratified charge combustion by igniting and burning a flammable mixed gas so that the ignition gap of an ignition plug is located in a lump of the flammable mixed gas formed in a part inside a cylinder at the ignition timing. <P>SOLUTION: A fuel injection valve 1 can change the spreading angle of an injected fuel into at least two large and small values, and changes the spreading angle of the injected fuel during the fuel injection for the stratified charge combustion so that a part of the injected fuel of a large spreading angle and a weak piercing force is directed toward an ignition gap of an ignition plug 2 while the injected fuel of a small spreading angle and a strong piercing force is not directed toward the ignition gap of the ignition plug. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a direct injection spark ignition internal combustion engine.

  In the latter half of the compression stroke, fuel is injected by the fuel injection valve so that a part of the injected fuel goes to the ignition gap of the ignition plug, and the ignition plug is inserted into a lump of combustible mixture formed in a part of the cylinder at the ignition timing. Stratified combustion is known in which a combustible mixture is ignited and burned so that an ignition gap is located. In an in-cylinder spark ignition internal combustion engine that performs such stratified combustion, since the spark plug becomes hot and pre-ignition is likely to occur, it is difficult to project the spark plug greatly into the cylinder.

  In general, since both the spark plug and the fuel injection valve are arranged at the upper part of the cylinder, in order to direct a part of the injected fuel to the ignition gap of the spark plug as described above, Unless the spread angle is increased to reduce the penetration of the fuel spray, the fuel that has passed through the spark gap of the spark plug flies almost along the cylinder upper wall and has a relatively short distance to the cylinder bore. It easily collides with the cylinder bore. The fuel adhering to the cylinder bore at the time of this collision is discharged as unburned fuel without being burned, and exhaust emission is deteriorated.

  As a result, a fuel injection valve that makes the spread angle of the injected fuel variable is provided, and in the intake stroke injection for forming a homogeneous mixture in the cylinder, the spread angle of the injected fuel is reduced, and the compression stroke injection at the time of stratified combustion Has proposed a direct injection spark ignition internal combustion engine in which the spread angle of the injected fuel is increased. (For example, refer to Patent Document 1).

JP-A-8-177684 JP 2005-54733 A

  In stratified combustion, if turbulence is present in the combustible mixture formed in a part of the cylinder, good combustion with a high combustion rate can be achieved. However, in the above-described in-cylinder spark-ignition internal combustion engine, the penetration force of the injected fuel at the time of stratified combustion is weakened, so that the turbulent mixture cannot be generated by the injected fuel.

  Accordingly, an object of the present invention is to dispose an ignition plug and a fuel injection valve in the vicinity of the upper center of the cylinder, inject the fuel by the fuel injection valve so that a part of the injected fuel goes to the ignition gap of the ignition plug, and In-cylinder injection spark ignition internal combustion engine that performs stratified combustion by igniting and burning a combustible mixture such that an ignition gap of a spark plug is positioned in a lump of combustible mixture formed in a part of the cylinder Is to suppress the collision of the injected fuel to the cylinder bore during stratified combustion, and to increase the combustion speed to achieve good stratified combustion.

  In the cylinder injection type spark ignition internal combustion engine according to claim 1 of the present invention, the spark plug and the fuel injection valve are arranged in the vicinity of the upper center of the cylinder so that a part of the injected fuel goes to the ignition gap of the spark plug. Then, fuel is injected by the fuel injection valve, and the combustible mixture is ignited and burned so that the ignition gap of the spark plug is positioned in a lump of combustible mixture formed in a part of the cylinder at the ignition timing. In the in-cylinder spark ignition internal combustion engine that performs stratified combustion by this, the fuel injection valve can switch the spread angle of the injected fuel into at least two stages of large and small, and during stratified combustion, the injected fuel is injected during fuel injection. The spread angle is switched, and a part of the injected fuel with a large spread angle and a weak penetrating force is directed to the ignition gap of the spark plug, and the spread angle is small and penetrated. Strong injection fuels is characterized in that it is adapted not directed to the spark gap of the spark plug.

  According to a second aspect of the present invention, the direct injection spark ignition internal combustion engine according to the first aspect is the direct injection spark ignition internal combustion engine according to the first aspect, wherein the fuel injection valve performs a compression stroke to an expansion stroke during stratified combustion. The fuel is injected between the two.

  According to a third aspect of the present invention, the direct injection spark ignition internal combustion engine according to the first aspect is the direct injection spark ignition internal combustion engine according to the first aspect, wherein the fuel injection valve has a high lift amount and a low lift amount. When the valve body is opened as the low lift amount, the fuel passes through the nozzle hole while being injected, and the injected fuel has a wide spread angle and the penetrating force is weakened. When the valve body is opened with the high lift amount, the fuel passes through the injection hole without turning and is injected, and the injected fuel has a small spread angle and a strong penetration force.

  According to the in-cylinder injection spark ignition internal combustion engine according to claim 1 of the present invention, the fuel injection valve disposed in the vicinity of the upper center of the cylinder is capable of switching the spread angle of the injected fuel into at least two stages, During stratified combustion, the spread angle of the injected fuel is switched during fuel injection, and a portion of the injected fuel that has a large spread angle and a weak penetration force is directed to the ignition gap of the spark plug disposed near the center of the cylinder upper portion. In addition to suppressing the collision of the fuel that has passed through the ignition gap of the plug with the cylinder bore, the ignition gap of the ignition plug is positioned in a lump of combustible mixture formed in a part of the cylinder by the entire injected fuel at the ignition timing. It is possible to ignite and burn a combustible mixture.

  In addition, the injected fuel with a small spread angle and strong penetration force is prevented from going to the ignition gap of the spark plug, which suppresses the collision of the fuel with the cylinder bore and causes turbulence due to the collision with the intake air in its flight path. In order to become a combustible air-fuel mixture, a part of the lump combustible air-fuel mixture formed in a part of the cylinder at the ignition timing is turbulent, and good stratified combustion with a high combustion speed is realized. Can do.

  According to the direct injection spark ignition internal combustion engine according to claim 2 of the present invention, in the direct injection spark ignition internal combustion engine according to claim 1, the fuel injection valve expands from the compression stroke during stratified combustion. Injected fuel not only in stratified combustion by fuel injection during the stroke, but also in stratified combustion where the ignition timing is greatly retarded by the fuel injection in the expansion stroke to increase the exhaust gas temperature It is possible to suppress the collision with the cylinder bore and increase the combustion speed.

  According to the in-cylinder injection spark ignition internal combustion engine according to claim 3 of the present invention, in the in-cylinder injection spark ignition internal combustion engine according to claim 1, the fuel injection valve has a high lift amount and a low lift amount. It can be controlled in two stages of lift amount, and when the valve body is opened as a low lift amount, the fuel is injected while turning through the nozzle hole, the injected fuel has a wide spread angle and the penetration force is weakened, When the valve body is opened with a high lift amount, the fuel passes through the nozzle hole without being swirled and is injected, and the injected fuel has a small spread angle and a strong penetrating force. Thus, the fuel injection valve spreads the injected fuel. The angle can be switched between two levels.

  FIG. 1 is a bottom view of a cylinder head showing an embodiment of a direct injection spark ignition internal combustion engine according to the present invention, and FIG. 2 is a schematic longitudinal sectional view of the direct injection spark ignition internal combustion engine of FIG. Also shows the fuel injection timing for stratified combustion. In these drawings, reference numeral 1 denotes a fuel injection valve that is disposed substantially at the center of the cylinder and injects fuel directly into the cylinder, and 2 is a spark plug that is disposed in the vicinity of the fuel injection valve 1. 3 is a piston, 4 is a pair of intake valves, and 5 is a pair of exhaust valves.

  This in-cylinder injection spark ignition internal combustion engine injects fuel in the latter half of the compression stroke by the fuel injection valve 1, vaporizes the injected fuel while flying in the cylinder, and directly injects a combustible mixture into a part of the cylinder. The flammable mixture is ignited and burned by the spark plug 2 and stratified combustion is performed to enable combustion at an air-fuel ratio leaner than the stoichiometric air-fuel ratio as a whole in the cylinder. Although it is possible to start fuel injection from the first half of the compression stroke and perform stratified combustion, it is difficult to generate high engine output in stratified combustion. As a result, when the engine load is higher than the set load, the fuel injection valve 1 injects fuel during the intake stroke (preferably, the second half of the intake stroke) to form a homogeneous mixture in the cylinder, and this homogeneous mixture is spark plugged. You may make it implement the homogeneous combustion made to ignite and burn by 2. FIG.

  During homogeneous combustion, if the cavity 3a is formed on the top surface of the piston 3 and the attenuation of the tumble flow that descends the exhaust valve side and rises the intake valve side in the cylinder is suppressed, the injected fuel is injected into the cylinder by the tumble flow. It becomes easy to disperse in the whole and is advantageous for forming a homogeneous gas mixture.

  Incidentally, a catalyst device for purifying exhaust gas is arranged in the engine exhaust system. However, when the temperature of the catalyst device is lower than the catalyst activation temperature, the exhaust gas cannot be purified well. Accordingly, it is preferable to warm up the catalyst device by raising the exhaust gas temperature when starting the engine. In order to raise the exhaust gas temperature, the ignition timing may be retarded. However, in particular, at the time of cold start when the cooling water temperature is equal to or lower than the set temperature, it is necessary to considerably increase the exhaust gas temperature. For this purpose, the ignition timing is significantly retarded, for example, in the latter half of the expansion stroke. There is a need.

  In the above-described homogeneous combustion, it is difficult to ignite and burn the air-fuel mixture at such a greatly retarded ignition timing. Accordingly, at this time, fuel is injected by the fuel injection valve 1 immediately before the ignition timing in the latter half of the expansion stroke, and stratified combustion with excellent ignitability is performed. In this stratified combustion, the air-fuel ratio in the entire cylinder is set to a lean air-fuel ratio or a stoichiometric air-fuel ratio.

  In any stratified combustion, at the ignition timing, the ignition gap of the spark plug 2 must be positioned in the combustible mixture formed in a part of the cylinder. For this purpose, a part of the fuel injected from the fuel injection valve 1 is directed to the ignition gap of the spark plug 2. By the way, it is difficult for the spark plug 2 to protrude greatly into the cylinder in order to suppress pre-ignition. Thereby, a part of the injected fuel toward the ignition gap of the spark plug 2 flies almost along the cylinder upper wall, and the flight distance to the cylinder bore becomes shorter compared to other directions. When the penetration force of the fuel is strengthened, it becomes easy to collide with the cylinder bore after passing through the ignition gap of the spark plug 2.

  When the injected fuel collides with the cylinder bore, the fuel adheres to the cylinder bore, and the attached fuel cannot be combusted and is discharged as unburned fuel. Worsen. Also, engine oil may be diluted. Thereby, if the penetration angle of the injected fuel is reduced by increasing the spread angle of the injected fuel, the collision of the fuel with the cylinder bore can be suppressed. However, even if a combustible air-fuel mixture is formed in the cylinder by the injection fuel having such a low penetration force, there is no turbulence in the combustible air-fuel mixture, and only slow stratified combustion with a low combustion speed can be realized.

  FIG. 3 is a cross-sectional view of the tip portion of the fuel injection valve 1. An internal space 2 of the fuel injection valve 1 communicates with a pressure accumulating chamber (not shown) and is filled with high-pressure fuel. A valve body 3 that is movable in the axial direction of the fuel injection valve 1 is disposed in the internal space 2. The valve body 3 can be opened by switching between the low lift amount L1 and the high lift amount L2. When the sealing corner 3a of the valve body 3 is brought into contact with the frustoconical sheet portion 2a of the internal space 2 to close the valve, it is formed in communication with the internal space 2 on the tip side from the contact position. Fuel injection from the nozzle hole 4 is stopped. In the present embodiment, the four injection holes 4 are formed at equiangular intervals around the axis of the fuel injection valve 1. However, this does not limit the present invention, and the number of nozzle holes can be arbitrarily set such as 5, 6, 8 or the like.

  In the sheet portion 2a of the internal space 2, a notch 4a that communicates with the periphery of each nozzle hole 4 from the upstream side is formed. When the valve body 3 is opened with the low lift amount L1, as shown in FIG. 3, the fuel easily flows into the notch 4a through a slight gap between the valve body 3 and the seat portion 2a. The fuel flowing into the nozzle hole 4 through the notch 4a passes through the nozzle hole 4 while turning, as indicated by the one-dot chain line arrow, and a turning speed component is given to the injected fuel. As a result, the injected fuel has a conical shape with a large spread angle, and the penetration force is weakened.

  On the other hand, when the valve body 3 is opened with a high lift amount L2, the valve body 3 and the seat portion 2a are relatively separated from each other, so that the fuel hardly passes through the notch 4a having a large passage resistance. It flows directly into the nozzle hole 4. As a result, the swirl speed component is not imparted to the injected fuel, and the injected fuel has a conical shape with a small spreading angle, and the penetration force is increased.

  The in-cylinder injection spark ignition internal combustion engine of the present embodiment uses such a fuel injection valve 1 to open the valve body 3 as shown in the time chart of FIG. 4 at the time of fuel injection during stratified combustion. . That is, the valve body 3 is opened with the low lift amount L1 at time t0, the lift amount of the valve body 3 is switched to the high lift amount L2 at time t1, and the valve body 3 is closed at time t2. Thereby, in the valve opening period from time t0 to t2, first, conical fuel having a large spread angle and a weak penetration force is injected. The central axis of one injection hole 4 of the fuel injection valve 1 is directed below the spark plug 2, and the conical upper fuel injected from the injection hole 4 has a large spreading angle. To the ignition gap.

  Thus, since the penetration force of the fuel toward the ignition gap of the spark plug 2 is weak, it is difficult for the fuel to pass through the ignition gap and collide with the cylinder bore. As shown by dots in FIGS. 1 and 2, the conical fuels having a large spread angle simultaneously injected from the respective injection holes 4 are connected to each other and become a lump of combustible air-fuel mixture around the fuel injection valve 1. Next, the fuel injection valve 1 injects conical fuel having a small divergence angle and a strong penetration force from each injection hole 4. Since this injected fuel does not fly along the cylinder upper wall so as to go to the ignition gap of the spark plug 1, the flight distance to the cylinder bore becomes relatively long, and even if the penetration force is strong, it is difficult to collide with the cylinder bore.

  Each of the injected fuels travels through a lump of combustible air-fuel mixture around the fuel injection valve 1 as shown by the dashed lines in FIGS. 1 and 2, and the penetrating force is lost before it collides with the cylinder bore. Although it becomes a combustible air-fuel mixture, in that case, turbulence is generated by collision with intake air in its flight path.

  Each combustible mixture formed by the injected fuel having a small divergence angle and a strong penetrating force is connected to each other through a lump of combustible mixture around the fuel injection valve 1, and thus, all of the injected fuel in the cylinder A lump of combustible air-fuel mixture is formed in a part, and the ignition gap of the spark plug 2 is located in the combustible air-fuel mixture. Thus, the combustible mixture can be reliably ignited by the spark plug 2 at the ignition timing. Moreover, in a lump of combustible air-fuel mixture, turbulent gas is generated in the combustible air-fuel mixture portion formed by the fuel having a strong penetration force, so that good stratified combustion with a high combustion speed can be realized.

  In the present embodiment, the injected fuel having a large spread angle is injected first. However, the valve body 3 is first opened with a high lift amount, and the lift amount is switched to a low lift amount during fuel injection. Alternatively, the injected fuel having a small spread angle may be injected first.

  Although the fuel injection valve of the present embodiment has a plurality of injection holes, it may have only a single injection hole. In addition, the injected fuel is not limited to a conical shape, and may be widened, for example, may be a flat fan shape injected from a slit-shaped injection hole.

  The lift amount switching time t1 during fuel injection is set, for example, so that the fuel injection amount at the high lift amount and the fuel injection amount at the low lift amount are substantially equal. Alternatively, the lift amount switching time t1 may be set so that the fuel injection amount at the low lift amount is constant and the remaining required amount is the fuel injection amount at the high lift amount.

It is a bottom view of a cylinder head showing an embodiment of a cylinder injection type spark ignition internal combustion engine by the present invention. It is a schematic longitudinal cross-sectional view of the cylinder injection type spark ignition internal combustion engine of FIG. It is sectional drawing of a fuel injection valve front-end | tip. It is a time chart which shows the lift pattern of a valve body.

Explanation of symbols

1 Fuel Injection Valve 2 Spark Plug 3 Piston

Claims (3)

  An ignition plug and a fuel injection valve are arranged near the center of the upper part of the cylinder, and fuel is injected by the fuel injection valve so that a part of the injected fuel goes to the ignition gap of the ignition plug. In a direct injection spark ignition internal combustion engine that performs stratified combustion by igniting and burning the combustible mixture such that an ignition gap of the spark plug is positioned in a lump of combustible mixture formed in The injection valve can switch the spread angle of the injected fuel at least in two stages, large and small, and during stratified combustion, the spread angle of the injected fuel is switched during fuel injection, and a portion of the injected fuel with a large spread angle and a weak penetration force can be obtained. The injected fuel that is directed toward the ignition gap of the spark plug and has a small spread angle and a strong penetration force does not go to the ignition gap of the spark plug. Unisa injection spark ignition internal combustion engine, characterized in that the.   The in-cylinder injection spark ignition internal combustion engine according to claim 1, wherein the fuel injection valve injects fuel during a stratified combustion between a compression stroke and an expansion stroke.   The fuel injection valve can control the valve body in two stages of a high lift amount and a low lift amount. When the valve body is opened as the low lift amount, the fuel passes while turning in the nozzle hole. The injected fuel has a wide spread angle and a low penetrating force. When the valve body is opened as the high lift amount, the fuel passes through the injection hole without turning and is injected. The in-cylinder injection spark ignition internal combustion engine according to claim 1, characterized in that the penetration force is small.

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