JP3301013B2 - Spark ignition combustion method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark ignition type combustion method in which air is sucked into a cylinder, the intake air is compressed by a piston, and fuel is directly injected into a cylinder to ignite and burn.

[0002]

2. Description of the Related Art In a conventional spark ignition engine, fuel is mainly supplied to an intake pipe by a carburetor or an injection valve, mixed with air in advance, and then sucked, ignited, and burned in a cylinder. Since the mixture is adjusted to a concentration within the flammable range, the load is usually adjusted by controlling the intake air amount, that is, by using a throttle valve. Therefore, work is required in the gas exchange process, and fuel efficiency is poor in a frequently used partial load, for example, in an automobile engine. Further, the specific heat ratio of the air-fuel mixture adjusted to the flammable range is small, which is disadvantageous in terms of thermal efficiency. On the other hand, a system has been proposed in which air is sucked, fuel is directly injected into a cylinder to ignite and burn (Japanese Utility Model Laid-Open No. 1-173416). This is a system in which fuel is injected at the end of the compression stroke at low load, fuel is collected and burned in the ignition plug 30, and fuel is injected during the intake stroke at high load, and fuel and air are mixed well and ignited and burned. is there. In this case, since the load can be adjusted only by the fuel injection amount, the work in the gas exchange process becomes unnecessary, and the fuel efficiency is good even at the partial load. Further, since the ratio of air is high, the specific heat ratio is large, and the thermal efficiency is high.

[0003] However, it is difficult for this combustion method to produce a proper air-fuel mixture. That is, to a low load must collect fuel to the vicinity of the spark plug, the fuel is dispersed opposite to the high load, it has to be prevented rich Do mixture is gather the Ri spark plug periphery. When the air-fuel mixture of spark plug circumference Ri is a dark, smoldering of misfire or plug, because the cause of such smoke generated. Also, unlike diesel,
Since combustion proceeds mainly by flame propagation, it is necessary to quickly vaporize and mix the fuel.

[0004]

SUMMARY OF THE INVENTION The present invention solves the problems of the prior art, in which fuel is quickly vaporized and mixed to form a combustible air-fuel mixture around a spark plug, and combustion stability at low load is reduced. It is an object of the present invention to provide a spark-ignition combustion method capable of securing fuel dispersibility and air utilization under a high load while maintaining performance.

[0005]

Means for Solving the Problems] spark ignition combustion method of claim 1, wherein the ignition-flops in a central portion of the inner wall surface of the cylinder head
Place the lug on the inner peripheral surface of the cylinder head
Position the fuel injection valve and place it below the fuel injection valve on the top of the piston.
To form a cavity that extends from
The spark-ignition combustion process of an internal combustion engine, the spark plug
From the bottom of the cavity at the end of the side cavity
Plane extending in the direction and including the fuel injection valve and the cylinder center axis
A wall extending in an arc shape in the lateral direction to the cavity
Form, from the nozzle hole of the fuel injection valve disposed to be inclined with respect to the center axis of the cylinder, so the when projected onto the plane containing the nozzle hole and the cylinder center axis flat, perpendicular to the plane containing the nozzle hole and the cylinder center axis its entirety the sector-shaped fuel spray when projected to a plane including the injection port, the intersection of the spray and the cylinder center axis
Spray toward the bottom of the cavity to spray fuel
Dispersed in the cavity, then dispersed in the cavity
The sprayed fuel is blown above the cavity by the cavity wall,
Around the spark plug by rolling it inwards
And then spray the collected fuel spray around the spark plug.
It is characterized by being ignited by a fire plug .

[0006]

[0007]

[0008]

[0009]

[0010]

According to the spark ignition type combustion method of the present invention having the above structure, when the fuel spray ejected from the injection valve is projected onto a plane including the nozzle and the cylinder center axis, the fuel spray becomes flat.
When projected onto a plane perpendicular to the plane including the injection port and the cylinder central axis and projected onto a plane including the intersection of the injection port, the spray and the cylinder central axis, the fuel can be quickly dispersed in the cavity by being substantially fan-shaped. Since this flat fan-shaped spray easily entrains the surrounding air, when the fuel is injected in the compression stroke, the air heated to a high temperature by the compression is quickly taken in, and vaporization and mixing are quick. Further, the air entrained by the spray deprives the momentum of the spray, so that the flying speed of the spray is reduced and the spray length is shortened. Therefore, even if the injection timing is advanced, the fuel does not wet the cylinder wall, and conversely, even if the injection timing is delayed, the piston surface is not covered with the liquid film. on the other hand,
Spray inside the cavity that has been vaporized and mixed
Ri Atsuma more guided by the spark plug position, can also be efficiently combusted in less <br/> have fuel and thus.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

[0013]

1 to 4 show a first embodiment of the present invention.
In the fuel injection valve, the needle valve 1 is slidably fitted into a valve hole 6 formed in the base end face of the valve body 2.
A coil spring 5 is attached to the base end of the coil spring 5. A conical valve seat 8 is provided at the distal end of the valve hole 6 with which the conical distal end 7 of the needle valve 1 contacts, and a slit-shaped opening from the valve seat 8 to the distal end surface of the valve body 2. An injection hole 4 is provided. A sack portion 3 is provided between the slit-shaped injection hole 4 and the valve seat portion 8, and the needle valve 1 is provided.
To form a cylindrical main body portion and the valve body 2 two annular pressure chambers 12 located Ri near the circumferential boundary between the conical tip 7. The distal end of the fuel supply passage 11 drilled at the base end of the valve body 2 is
It communicates with the outer peripheral surface of the pressure chamber 12. Needle valve 1 and valve body 2
An annular connection passage 13 connected to the pressure chamber 12 is provided therebetween. Needle valve 1 through fuel supply passage 11 and connection passage 13
When the pressure of the fuel acting on the tip 7 of the needle rises, the needle valve 1
Is disengaged from the valve seat portion 8 of the valve hole 6 against the coil spring 5.

For this reason, in the fuel injection valve according to the first embodiment, the pressure chamber 12 communicates with the injection hole 4 through the gap between the tip 7 of the needle valve 1 and the valve seat 8 of the valve hole 6. The valve is configured to open. The fuel is supplied to the slit-shaped injection hole 4 when the valve is opened by the fuel passage 11, the pressure chamber 12, the connection passage 13, and the gap between the distal end portion 7 of the needle valve 1 and the valve seat portion 8 of the valve hole 6. It constitutes a passage. The needle valve 1 can be directly lifted and opened using an electromagnetic force or the like in addition to the fuel pressure. Further, the slit-shaped injection hole 4 has an outer end 10 on the outer peripheral side of the valve body 2 and an inner peripheral side of the valve body 2, that is, an inner end 9 on the side of the sack portion 3, and the outer end 10 and the inner end 9 It is composed of a straight or arcuate passage.

Here, the inner end 9 of the slit-shaped injection hole 4
Is in the range of 0.05 mm or more and 0.24 mm or less. The optimal numerical range is 0.06
mm or more and 0.20 mm or less. As a result, the fuel injected from the slit-shaped injection hole 4 becomes flat and fan-shaped, and as the liquid film moves away from the slit-shaped injection hole 4, its thickness decreases and the contact area with the surrounding air increases. The liquid film is torn off by the surrounding air, and rapidly changes to a fine spray. FIG. 5 shows the relationship between the average particle diameter ds and the width W of the spray thus obtained. As is apparent from FIG. 5, as the width W increases, the average particle diameter ds increases. This is because the greater the width W, the greater the thickness of the injected fuel liquid film. FIG. 5 shows the results obtained from various experiments and the like. As is apparent from FIG.
Is 0.24 mm or more, the average particle diameter ds of the spray increases rapidly. The width W at which the average particle diameter ds of the spray is maintained at a substantially uniform value is 0.06 mm or more and 0.20 m
m or less.

Further, since the injection valve of the present invention has a large spray angle, there is an advantage that the spray length can be reduced as compared with the conventional hole nozzle. Since many spark ignition engines have a small cylinder diameter, the distance from the nozzle to the wall is short. The spray length should be appropriately short so as not to wet the wall with fuel. The spray grows with almost the same momentum. In the nozzle according to the first embodiment of the present invention, if the width W is determined, the momentum per unit spray angle is determined. Therefore, even if the spray angle is changed, the spray length does not change, but the spray length per flow rate is By increasing the spray angle, the spray length is reduced. Since the injection period is limited in the engine, the spray length per flow rate is important. FIG. 6 compares the spray length with a hole nozzle having the same flow rate. As the spray angle increases, the spray length decreases. For example, when the spray angle is set to 90 degrees, the spray length is less than half that of a conventional single-hole nozzle. It is 70% compared to a 5-hole nozzle. Here, it is compared with one fan spray, but it can be further shortened by opening a plurality of slits.

In the first embodiment of the present invention, such a fuel injection valve is provided in the internal combustion engine shown in FIGS. The internal combustion engine includes an intake port 27, an intake valve 28, a spark plug 30, an exhaust port (not shown), a cylinder head 25 equipped with an exhaust valve, and a cylinder 24 and a piston 21 reciprocally inserted into the cylinder 24. I have. A plurality of piston rings 29 are provided on the side surface of the piston 21 to prevent gas from flowing from the combustion chamber 31. The fuel injection valve 23 is attached to the cylinder head 25 on the intake valve 28 side so that the nozzle tip 23a is inclined substantially toward the cylinder center axis. The first embodiment has two intake valves, and the fuel injection valve 23 is located between the intake valves 28. Then, the spray flow is ejected so as to be flattened in a plane including the central axis of the cylinder 24 and spread in a fan shape in a plane substantially perpendicular to the central axis of the cylinder 24, but the spray center is directly directed to the ignition plug 30. Not to hit
Squirts slightly downward. The injection direction differs depending on the engine, but generally ranges from 20 degrees to 60 degrees below the cylinder.

On the top surface 21a of the piston 21, a cavity 2 having a nozzle tip 23a and a spark plug 30 at substantially both ends is provided.
2 is formed by opening it into the combustion chamber 31. Cavity 2
Reference numeral 2 denotes a compression top dead center, which is a depth at which the gap 30a of the ignition plug 30 is approximately at the center of the cylinder head 25 and the bottom surface of the cavity 22. The width of the cavity 22 is larger than the width of the spray projected on a plane perpendicular to the cylinder center axis when the spray tip reaches the center of the cylinder. That is, the spray in the space in the combustion chamber at this time is contained in the cavity 22 by the rise of the piston 21. Also,
At least the spark plug 30 of the cavity 22
The side has a concave curvature with respect to the cavity 22. The curvature R is set to (radius of curvature R) ≦ (distance L from the nozzle tip to the cavity wall surface).

The air in the combustion chamber 31 is compressed in the compression stroke from the bottom dead center position where the piston 21 completes the intake to the top dead center. When fuel is ejected from the injection hole of the injection valve 23 in the compression process, the spray particles are flattened when projected onto a plane including the cylinder center axis and the nozzle 23a, as shown in FIG. When projected, they scatter in a fan shape and substantially symmetrically with respect to the spark plug 30. Since the fuel spreads rapidly after leaving the injection hole, the spray particles collide with the wall of the cylinder 24 at high speed,
The wall of No. 2 is not wet with a large amount of liquid spray. Also,
Because of its flat shape, it mixes quickly with the surrounding high-temperature air, so even if sensible heat or latent heat is taken for evaporation, the temperature of the mixture in the spray does not drop so much. The spray becomes a flow that winds upward and inward of the cavity 22 by the wall surface of the cavity 22. Combined with the rise of the piston 21, a combustible air-fuel mixture is formed in the ignition plug 30 before the compression top dead center. The flame ignited by the ignition plug 30 burns by flame propagation.

At this time, due to the squish flow between the cavity 22 and the piston top surface 21a, the air-fuel mixture is contained in the cavity 22 and is prevented from scattering outside the combustion chamber.
The flame formed by the spark plug 30
Develop within. Therefore, there is no fear of misfiring or extinguishing. Furthermore, since the spray in the first embodiment of the present invention is a fan-shaped spray, the unevenness in concentration is small, and the flame propagation is not interrupted.
When the load is low and the load is small,
Delay the injection timing, ignite before the fuel spreads,
On the other hand, when the load is high and the injection amount is high, the injection timing is advanced,
It is good to avoid that the rich air-fuel mixture collects too much in the spark plug 30.

In the internal combustion engine of the first embodiment, when the injection timing is delayed, as shown in FIGS. 9 and 10, the spray collides with the cavity 22 relatively quickly, but the spray is flat and the Since the bottom surface of the fan 22 has a fan-like shape, heat is effectively received from the piston 21 and the air, and vaporization and mixing can be performed quickly. Therefore, combustion in which the time from injection to ignition is shortened is possible. Further, if the curvature R of the cavity is set to (radius of curvature R) ≦ (distance L from the tip of the nozzle to the cavity wall), the fuel is collected in the ignition plug 30 along this curvature, so that operation with less fuel is possible. is there. On the other hand, when the injection timing is advanced, the spray of the first embodiment has a short spray length, so the time until collision with the cavity is long. However, since the spray is dispersed in a fan shape and is flat, Effective heat is obtained from the surrounding air, and there is no delay in evaporative mixing. Then, as shown in FIG. 11, the initially injected fuel collides with the cavity 22 and then diffuses in the air, so that a rich mixture is not collected in the ignition plug 30 and stable ignition is possible.

Further, when the load further increases and is close to the full load, it is possible to inject fuel not only in the compression stroke but also in the intake stroke. At this time, the spray length is short,
Since the spray has a low penetration force, even if the piston 21 goes down, it does not wet the wall surface of the cylinder 24 and is dispersed in the cylinder by the flow of the intake air, thereby increasing the air utilization.
In the internal combustion engine according to the first embodiment of the present invention, a stable combustible air-fuel mixture is formed in the ignition plug 30 regardless of the magnitude of the load as described above. Provides excellent performance as an internal combustion engine.

[0023]

[Second Embodiment] A second embodiment of the present invention is as follows.
As shown in FIG. 12, the vertical wall surface of the cavity 22 has an R shape, and the piston top surface 21a has a lip shape protruding from the inner wall of the cavity 22. Other fuel injection valves 23, spray shapes, pistons 21 and the like are the same as in the first embodiment.

In the second embodiment of the present invention having the above-described structure, the spray changes its direction after collision with the wall surface of the cavity 22 as in the first embodiment. Has a round shape (radius of curvature r ₁ ), so that the fuel flows in such a manner as to wind up toward the inside of the cavity 22. For this reason, the fuel is less likely to flow out of the cavity 22, and the flame after ignition is less likely to flow out of the cavity 22 to be cooled and extinguished. Also,
There is an advantage that the combustion period is shortened because strong turbulence is created in combination with the squish flow.

[0025]

[Third Embodiment] A third embodiment of the present invention is as follows.
The cavity 22 is a two-stage, 13, further cavity 22 inside the shallow cavity 22 b as shown in FIG. 14
a is formed. Other fuel injection valves 23, spray shapes, pistons 21 and the like are the same as those in the first embodiment.

When the cavity 22 according to the third embodiment of the present invention is used, the fuel can be more easily ignited when the load is low.
At high load, the fuel can be more diffused and burned. That is, FIG. 15, when delaying the fuel injection timing to a small injection quantity at the time, as shown in FIG. 16, the injected fuel enters the inside of the cavity 22 b, leading to the ignition plug 30 is bent upwardly through the inner wall surface thereof. Therefore, the fuel concentrates on the spark plug 30 without being excessively dispersed,
Ignition and combustion are possible with very little fuel. on the other hand,
When the load is high, the injection timing is advanced. Therefore, the fuel is
7, the outer large cavity 22 as shown in FIG.
b and the inner cavity 22a. The outer cavity 22b is bent upward and inward to reach the spark plug 30 as in the first embodiment.
The fuel a is bent downward and is dispersed in the cavity 22 without reaching the spark plug 30. As a result, a stable combustible air-fuel mixture is formed in the ignition plug 30 irrespective of the magnitude of the load, and excellent performance is provided, for example, as an automotive internal combustion engine having a large load variation.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a fuel injection valve according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a fuel injection valve according to the first embodiment of the present invention.

FIG. 3 is a longitudinal sectional view showing a spray state of a fuel injection valve according to the first embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing a spray state of a fuel injection valve according to the first embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the average particle size and the width of the spray of the fuel injection valve in the first embodiment.

FIG. 6 is a diagram showing a relationship between a spray angle and a spray length ratio of a fuel injection valve in the first embodiment.

FIG. 7 is a plan view showing the internal combustion engine according to the first embodiment;
Figure

FIG. 8 is a longitudinal sectional view showing the internal combustion engine according to the first embodiment.

FIG. 9 is a plan view showing a spray state of the internal combustion engine in the first embodiment .

FIG. 10 is a longitudinal sectional view showing a spray state of the internal combustion engine according to the first embodiment.

FIG. 11 is a longitudinal sectional view showing a spray state of the internal combustion engine in the first embodiment.

FIG. 12 is a partial cross-sectional view illustrating an internal combustion engine according to a second embodiment.

FIG. 13 is a plan view showing an internal combustion engine according to a third embodiment.
Front view

FIG. 14 is a longitudinal sectional view showing an internal combustion engine according to a third embodiment.

FIG. 15 is a plan view showing a spray state of an internal combustion engine according to a third embodiment .

FIG. 16 is a longitudinal sectional view showing a spray state of an internal combustion engine according to a third embodiment.

FIG. 17 is a plan view showing a spray state of an internal combustion engine in a third embodiment .

FIG. 18 is a longitudinal sectional view showing a spray state of an internal combustion engine according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Needle valve 2 Valve element 3 Sack part 4 Injection hole 5 Coil spring 6 Valve hole 7 Tip part 8 Valve seat part 9 Inner end 10 Outer end 22, 22a Cavity 23 Fuel injection valve 21 Piston 24 Cylinder 31 Combustion chamber 30 Spark plug

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02M 61/18 360 F02M 61/18 360J (56) References JP-A-3-78562 (JP, A) JP-A-8-144762 (JP, A) JP-A-57-13215 (JP, A) JP-A-5-1544 (JP, A) JP-A-2-122123 (JP, U) JP-A-3-27829 (JP, U) Kaihei 1-173416 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02B 23/10 F02B 17/00 F02M 61/18 F02M 61/14

Claims (1)

(57) [Claims] An ignition plug is provided at a central portion of an inner wall surface of a cylinder head.
Place the lug on the inner peripheral surface of the cylinder head
Position the fuel injection valve and place it below the fuel injection valve on the top of the piston.
To form a cavity that extends from
The spark-ignition combustion process of an internal combustion engine, the spark plug
From the bottom of the cavity at the end of the side cavity
Plane extending in the direction and including the fuel injection valve and the cylinder center axis
A wall extending in an arc shape in the lateral direction to the cavity
Form, from the nozzle hole of the fuel injection valve disposed to be inclined with respect to the center axis of the cylinder, so the when projected onto the plane containing the nozzle hole and the cylinder center axis flat, perpendicular to the plane containing the nozzle hole and the cylinder center axis its entirety the sector-shaped fuel spray when projected to a plane including the injection port, the intersection of the spray and the cylinder center axis
Spray toward the bottom of the cavity to spray fuel
Dispersed in the cavity, then dispersed in the cavity
The sprayed fuel is sprayed over the cavity by the cavity wall.
To the inside of the spark plug
And then the fuel spray collected around the spark plug
Spark ignition combustion method in which a spark plug is ignited by a spark plug .