JPH08246878A - Cylinder injection type spark ignition engine - Google Patents

Abstract

PURPOSE: To always realize excellent stratified combustion, and reduce fuel consumption by igniting an engine by using a first spark plug in the vicinity of a combustion chamber side surface when a fuel injection quantity is less than a prescribed value, and by using a second spark plug separate to the swirl downstream side when the fuel injection quantity is not less than a prescribed quantity. CONSTITUTION: A recess-shaped combustion chamber 7 eccentric to the opening part side of a straight port 3a is formed on a top surface of a piston 1, and a first spark plug 8a positioned in an almost cylinder center upper part in the last stage of a compression stroke, is arranged in a position in the vicinity of a side surface of this combustion chamber 7. A second spark plug 8b is arranged in a position separate to the more swirl downstream side than a position of the first spark plug 8a in the vivinity of a side surface of the combustion chamber 7. The spark plugs are switched to/from each other so that the first spark plug 8a is used when a fuel injection quantity is less than a first prescribed value and the second spark plug 8b is used when the fuel injection quantity is not less than the first prescribed value and is less than a second prescribed value, and a stratified combustion realizable operation area is expanded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder injection type spark ignition engine.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 6-175577 discloses a concave combustion chamber formed on the top surface of a piston, an ignition plug that enters near the side surface of the combustion chamber at the end of the compression stroke, and fog inside the combustion chamber in the latter half of the compression stroke. A fuel injection valve for injecting fuel in the form of a cylinder, and moving a mass of air-fuel mixture formed by the fuel injected into the combustion chamber along the side surface of the combustion chamber by using a swirl, and using an ignition plug. There is described a cylinder injection type spark ignition engine for realizing stratified charge combustion that enables ignition at a lean air-fuel ratio as a whole by reliably igniting and propagating this flame to the entire combustion chamber.

In this direct injection type spark ignition engine, when the fuel injection amount is relatively small, in order to maintain the ignitability of the air-fuel mixture, ignition is performed before a mass of air-fuel mixture moving near the side surface of the combustion chamber diffuses. Is executed, and when the fuel injection amount becomes relatively large as the engine load or the engine speed increases, a lump of air-fuel mixture is added to prevent ignitability from being excessively rich. The fuel injection timing and the ignition timing are controlled so that the ignition is executed when the fuel is diffused to some extent, that is, the longer the elapsed time from the end of injection to the ignition is, the longer the fuel injection amount increases. ing.

[0004]

In the cylinder injection type spark ignition engine described above, in order to reliably ignite the air-fuel mixture when the fuel injection amount is small, the range in which the air-fuel mixture reaches within a short elapsed time at this time. The spark plug must be placed on. However, when the spark plug is arranged at such a position, that is, at a position relatively close to the swirl downstream side from the position near the side surface of the combustion chamber where the air-fuel mixture is formed by the fuel injected from the fuel injection valve, the fuel injection amount When there is a relatively large amount of air, especially when a long elapsed time is required, a lump of air-fuel mixture may have already passed through this spark plug, and at this time the air-fuel mixture cannot be reliably ignited, so stratification Combustion is not possible.

Therefore, the object of the present invention is to expand the operating range of stratified charge combustion as compared with the conventional one, and to realize good stratified charge combustion even when the fuel injection amount is relatively large when the engine is under medium load. An object is to provide a cylinder injection type spark ignition engine.

[0006]

A cylinder injection type spark ignition engine according to the present invention comprises a concave combustion chamber formed on a top surface of a piston, a swirl generating means for generating swirl in the combustion chamber, and A first spark plug that enters the first position near the side surface of the combustion chamber at the end of the compression stroke, and a first spark plug that enters the first position near the side surface of the combustion chamber that is separated from the first position on the swirl downstream side at the end of the compression stroke. 2 spark plugs, a fuel injection valve that injects fuel toward the swirl upstream side of the first position near the side surface of the combustion chamber in the latter half of the compression stroke, and the combustion formed by the fuel injected from the fuel injection valve When the fuel injection amount is less than the first predetermined value, the first spark plug is used to ignite the air-fuel mixture that moves along the side surface of the chamber using a swirl. And a switching means for switching the used spark plug so that the second spark plug is used to ignite when the fuel injection amount is equal to or more than the first predetermined value and less than the second predetermined value. To do.

[0007]

In the above-mentioned in-cylinder injection type spark ignition engine, when the fuel injection amount is smaller than the first predetermined value, the first spark plug which enters the first position near the side surface of the combustion chamber is used by the switching means, and the fuel is also used. When the injection amount is greater than or equal to the first predetermined value and less than the second predetermined value, ignition is performed using the second spark plug that enters the second position that is separated from the first position on the side surface of the combustion chamber to the swirl downstream side. Therefore, the lump of air-fuel mixture that is formed by the fuel injected from the fuel injection valve and moves along the side surface of the combustion chamber using the swirl is
When the fuel injection amount is less than the first predetermined value, the first spark plug that comes into contact with it at the position before the diffusion is surely ignited, and when the fuel injection amount is the first predetermined value or more and less than the second predetermined value, to some extent It is reliably ignited by the second spark plug which comes into contact with the diffused position, and good stratified charge combustion can be realized from the time when the fuel injection amount is relatively small to the time when it is relatively large.

[0008]

1 is a longitudinal sectional view showing a first embodiment of a cylinder injection type spark ignition engine according to the present invention, and FIG. 2 is a plan view of a piston thereof. In these figures, 1 is a piston and 2 is a fuel injection valve for directly injecting fuel into the cylinder 10. The straight port 3a communicates with the inside of the cylinder 10 via an intake valve (not shown), and a swirl control valve 20 capable of closing the straight port 3a.
Reference numeral b is a helical port that communicates with the inside of the cylinder 10 via the intake valve 4b. The opening of the swirl control valve 20 is small, and most of the intake air passes through the cylinder port 10b.
When it is supplied into the cylinder 10, a swirl in the direction indicated by the arrow is generated in the cylinder 10. Two exhaust ports (one of which is shown at 5b) are in communication with the cylinder 10 via two exhaust valves (one of which is shown at 6b).

A concave combustion chamber 7 is formed on the top surface of the piston 1 and is eccentric to the opening of the straight port 3a. Near the side surface of the combustion chamber, at the end of the compression stroke, the first ignition is located substantially above the center of the cylinder. The electrode portion of the plug 8a is adapted to be inserted, and the second ignition plug 8b is simultaneously inserted at a position separated from the entry position of the first ignition plug 8a near the side surface of the combustion chamber 7 to the swirl downstream side. It has become.

The fuel injection valve 2 has two intake ports 3a, 3
2b, its injection port is directed toward the swirl upstream side by an angle θ1 with respect to the first spark plug 8a as shown in FIG. 2, and as shown in FIG.
Is directed obliquely downward, so that atomized fuel can be injected toward the side surface on the swirl upstream side of the first ignition plug 8a entry position of the combustion chamber 7 with respect to the piston 1 in the latter half of the compression stroke. Has become.

In the engine operating region I of FIG. 3 in which the engine load or the engine speed is high and the fuel injection amount is equal to or more than the second predetermined value, the swirl control valve 20 is fully opened and a large amount is supplied from both intake ports 3a and 3b. Intake is cylinder 1
While being supplied to the inside of 0, a large amount of fuel is injected from the fuel injection valve 2 in the intake stroke. At the ignition timing at the end of the compression stroke, a uniform air-fuel mixture is formed in the combustion chamber 7,
Also, since the ignition is performed by the second spark plugs 8a and 8b, excellent uniform combustion with a high combustion speed is realized.

On the other hand, when the fuel injection amount is smaller than the second predetermined value in the engine operating regions II and III in FIG. 3, the swirl control valve 20 is partially opened, and most of the intake air is taken from the helical port 3b to the cylinder 10. By supplying the gas into the cylinder 10, a swirl is generated in the cylinder 10, and a swirl that swirls in the same direction in the vicinity of the side surface of the combustion chamber 7 is also generated in the combustion chamber 7 as the piston 1 moves upward in the compression stroke.

The fuel injection by the fuel injection valve 2 at this time is as follows.
As shown in FIG. 4 (A), the fuel injected in the latter half of the compression stroke is mixed with the intake air before reaching the side surface of the combustion chamber 7, and adheres to the side surface of the combustion chamber 7 as liquid fuel. What you do is vaporized by the heat and mixes with the intake air,
A lump of air-fuel mixture is formed on the upstream side of the swirl where the spark plug 8a enters, and moves along the side surface of the combustion chamber 7 by using the swirl.

The air-fuel mixture has a low engine load and a low engine speed, and the fuel injection amount is smaller than the first predetermined value.
In the case of II, the concentration has a good ignitability before the diffusion, and in the engine operating region II where the fuel injection amount is equal to or more than the first predetermined value and less than the second predetermined value, it becomes rich before the diffusion. On the contrary, the ignitability is deteriorated, and the concentration of the ignitability becomes good when the ignitability is diffused to some extent. As a matter of course, the air-fuel mixture which moves along the side surface of the combustion chamber 7 using the swirl as described above has a larger diffusion degree as the elapsed time from the end of the fuel injection is longer and the movement distance is longer, In order to ensure good ignitability, the fuel injection amount and the engine speed are taken into consideration so that the elapsed time from the end of fuel injection to the ignition timing increases as the fuel injection amount increases. The time has come to be decided. There is an optimum ignition timing for each engine operating state, and it is not possible to greatly change the ignition timing. Therefore, the fuel injection timing is mainly determined based on the optimum ignition timing.

In this way, the engine operating regions II, II
Although fuel injection and ignition are executed in I, the direct injection spark ignition engine of the present embodiment uses the first spark plug 8a to ignite the air-fuel mixture before diffusing in the engine operating region III. In the operation area II, the second spark plug 8 is used to ignite the air-fuel mixture diffused to some extent.
b is used.

As a result, the engine operating region II in which ignition must be executed after a relatively short time after the end of fuel injection
In I, the first spark plug 8a located relatively close to the swirl downstream side from the position where the air-fuel mixture is formed in the vicinity of the side surface of the combustion chamber 7 through which the air-fuel mixture passes is used.
As shown in (B), even when the fuel injection amount is small and the ignition is executed in a considerably short time after the end of the fuel injection, there is no problem that the air-fuel mixture has not reached the spark plug at the ignition timing at this time. The air-fuel mixture at this time can be reliably ignited, and the flame propagates to the entire combustion chamber 7 while taking in the air in the combustion chamber 7, thereby enabling the combustion with a lean air-fuel ratio as a whole. Combustion is realized.

On the other hand, in the engine operating region II in which ignition must be executed after a relatively long time from the end of fuel injection, comparison is made from the formation position of the air-fuel mixture near the side surface of the combustion chamber 7 through which the air-fuel mixture passes to the downstream side of the swirl. Since the second spark plug 8b located far away is used, as shown in FIG. 4 (C), even when the fuel injection amount is large and it takes a considerably long time from the end of fuel injection to the ignition, the ignition is performed. At this time, there is no problem that the air-fuel mixture has already passed through the spark plug, and the air-fuel mixture at this time can be reliably ignited, and the flame takes in the air in the combustion chamber 7 while taking in the air. Propagate to the whole and good stratified combustion is realized even at this time.

FIG. 5 shows a second embodiment of the present invention, which is shown in FIG.
It is a top view of a piston corresponding to (A). The difference from the first embodiment is that the shape of the concave combustion chamber 7'formed on the top surface of the piston 1'is enlarged toward the opening side of the helical port 3b and becomes substantially symmetrical with respect to the piston center line. Cage,
This means that the first spark plug 8a and the second spark plug 8b at the same position as in the first embodiment are substantially symmetrical with respect to the piston center line. Similar to the first embodiment, the fuel injection valve 2 is configured to inject mist-like fuel toward the swirl upstream side from the entry position of the first ignition plug 8a on the side surface of the combustion chamber 7'at the end of the compression stroke.

According to this embodiment, the first spark plug is used.
By switching in the same manner as in the embodiment, as described above, good stratified combustion can be realized until the fuel injection amount becomes relatively large, and the fuel injection amount becomes the second predetermined value or more and uniform combustion is executed. In addition, since the flames ignited by both spark plugs are almost equally propagated in the entire combustion chamber 7 ′, it is possible to considerably increase the overall combustion speed as compared with the first embodiment, and the knocking occurrence limit is Improve,
It is possible to reduce the region where the ignition timing retardation is performed with the output reduction and the exhaust gas temperature rise in order to suppress knocking.

In the two embodiments described above, the fuel injection valve injects the fuel in the form of mist, but this does not limit the present invention, and the fuel may be injected in a columnar shape. The injected fuel collides with the side surface of the combustion chamber and is atomized, and the material adhering to the side surface is vaporized by the heat of the piston, so that a mixture may be formed on the swirl upstream side of the entry position of the first spark plug. It is possible to realize the same stratified combustion as described above.

[0021]

As described above, according to the in-cylinder injection type spark ignition engine of the present invention, a lump of mixture formed by the fuel injected from the fuel injection valve and moving along the side surface of the combustion chamber utilizing the swirl is mixed. The air is reliably ignited by the first spark plug that enters the position before diffusion when the fuel injection amount is less than the first predetermined value, and when the fuel injection amount is greater than or equal to the first predetermined value and less than the second predetermined value. It is reliably ignited by the second spark plug that enters the diffused position to some extent, and good stratified combustion can be realized from the time when the fuel injection amount is relatively small to the time when it is relatively large. The feasible driving range is expanded, and fuel consumption can be reduced accordingly.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of a cylinder injection type spark ignition engine according to the present invention.

2 is a plan view of the piston of FIG. 1. FIG.

FIG. 3 is a map for engine load and engine speed showing three engine operating regions divided based on a fuel injection amount.

FIG. 4 is a plan view of a piston showing a state of fuel injected into a combustion chamber in the first embodiment, (A) immediately after fuel injection, and (B) at ignition when the fuel injection amount is relatively small. , (C) are at ignition when the fuel injection amount is relatively large.

FIG. 5 is a plan view of a piston corresponding to FIG. 4A showing a second embodiment of the cylinder injection type spark ignition engine according to the present invention.

[Explanation of symbols]

 1 ... Piston 2 ... Fuel injection valve 3a ... Straight port 3b ... Helical port 7 ... Combustion chamber 8a ... First spark plug 8b ... Second spark plug 20 ... Swirl control valve

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location F02B 31/00 F02B 31/00 Z F02M 69/00 360 F02M 69/00 360C F02P 15/08 301 F02P 15/08 301C

Claims (1)

[Claims] 1. A concave combustion chamber formed on a top surface of a piston, a swirl generating means for generating a swirl in the combustion chamber, and a first position in the vicinity of a side surface of the combustion chamber that enters a first position at the end of the compression stroke. No. 1 spark plug, a second spark plug that enters a second position in the vicinity of the side surface of the combustion chamber, which is separated from the first position on the swirl downstream side at the end of the compression stroke, and the first position near the side surface of the combustion chamber Fuel injection valve that injects fuel in the latter half of the compression stroke toward the upstream side of the swirl, and the air-fuel mixture that is formed by the fuel injected from the fuel injection valve and that moves using the swirl along the side surface of the combustion chamber. On the other hand, when the fuel injection amount is less than the first predetermined value, ignition is performed using the first spark plug, and the fuel injection amount is not less than the first predetermined value and less than the second predetermined value. In-cylinder injection spark ignition engine, characterized in that it comprises a switching means for switching the used spark plug so that the second spark plug is used to perform ignition.