JPH07269349A - Combustion controller for engine - Google Patents

Abstract

PURPOSE:To reduce the amount of HC and NOx by effecting self-ignition in an auxiliary chamber after ignition of air-fuel mixture by an ignition plug and forming a projection which reduces the volume of a combustion chamber in the vicinity of the ignition plug when a piston is at the top dead center on a top face of the piston and the like. CONSTITUTION:Auxiliary chambers 11, 12 are formed in an outer peripheral fringe section of a pent roof type combustion chamber 1 having two inclined faces 1a, 1b and on a ridge line alpha, and two jet holes 11a, 11b; 12a, 12b which face reversely each other and are directed in the direction of tangent are formed in each auxiliary chamber 11, 12. Self-ignition is effected in the auxiliary chambers 11, 12 after air-fuel mixture is ignited by an ignition plug 10, and flame which is jetted from each jet hole grows along the peripheral direction of the combustion chamber. Also, a projection 52 in the shape of column having smaller diameter than that of a piston 51 is formed on a top face of the piston 51 to partition the combustion chamber 1 into an inner combustion chamber IA and an outer combustion chamber 1B. The ignition plug 10 is positioned in the inner combustion chamber 1A, and the auxiliary chambers 11, 12 are positioned in the outer combustion chamber 1B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to HC and N in exhaust gas.
The present invention relates to a combustion control device for an engine capable of significantly reducing Ox.

[0002]

2. Description of the Related Art In an engine, particularly a spark ignition type engine generally used as an automobile engine, harmful components in exhaust gas pose a problem. Of these harmful components, HC is
It tends to occur on the outer peripheral edge of the combustion chamber where the wall surface is easily cooled.

Japanese Utility Model Laid-Open No. 55-6484 discloses a single spark plug (ignition gap) and a spark plug without a spark plug.
The two sub-chambers are provided centrally in the center of the combustion chamber and spaced apart in the diametrical direction of the combustion chamber, and the injection holes that connect the sub-chamber and the combustion chamber are easily cooled in the outer peripheral edge of the combustion chamber. Those directed to the quench zone are disclosed. According to this method, after ignition by the spark plug, self-ignition is performed in the sub chamber, and the self-ignited flame is ejected from the injection hole toward the quench zone. Another technique utilizing self-ignition in the sub chamber is disclosed in Japanese Patent Laid-Open No. 62-233416.

[0004]

However, in the technique disclosed in Japanese Utility Model Laid-Open No. 55-6484, the flame ejected from the injection hole of the auxiliary chamber is directed from the substantial center of the combustion chamber to the outer peripheral edge of the combustion chamber. As described above, since only a specific part of the outer peripheral edge of the combustion chamber is directed, it is not enough to significantly reduce HC.

Further, the one disclosed in JP-A-62-233416 is for promoting late combustion by utilizing a jet flow from a sub chamber in a diesel engine, and actively reduces HC. Is not intended. In particular, the flame ejected from the sub chamber is directed toward the center of the combustion chamber, and it can be said that HC reduction that tends to occur at the outer peripheral edge of the combustion chamber is not intended at all.

Further, it is also desired to reduce NOx in the exhaust gas, but the preferable combustion mode for reducing HC is high temperature combustion, while the preferable combustion mode for reducing NOx is low temperature combustion. Combustion mode. Therefore, it is difficult to perform combustion that sufficiently reduces both HC and NOx, and in reality, HC and NOx are reduced by performing a post-treatment with a catalyst (three-way catalyst) provided in the exhaust path. ing.

An object of the present invention is to provide an engine combustion control device capable of sufficiently reducing both HC and NOx.

[0008]

In order to achieve the above object, the present invention has the following configuration. That is, in the spark ignition type engine configured to ignite the air-fuel mixture supplied to the combustion chamber by the spark plug arranged in the combustion chamber, the auxiliary chamber is formed at the outer peripheral edge of the combustion chamber,
The sub-chamber is communicated with the combustion chamber through a nozzle hole oriented substantially tangentially to the combustion chamber, and the spark plug is not disposed in the sub-chamber, but only in a substantially central portion of the combustion chamber. The ignition plug is arranged so that after the mixture is ignited by the ignition plug, self-ignition is performed in the sub chamber, and the ignition is performed when the piston is at the top dead center on at least one of the upper surface of the piston and the inner surface of the cylinder head. The structure is such that a protrusion is formed to reduce the volume of the combustion chamber near the plug. Preferred embodiments of the present invention based on the above configuration are as described in claims 2 and below in the claims.

[0009]

According to the present invention described in claim 1,
Since the flame ejected from the sub chamber through the injection holes grows along the circumferential direction of the combustion chamber, it is possible to greatly reduce HC that is likely to occur at the outer peripheral edge of the combustion chamber. Further, since no ignition plug is provided in the sub chamber, self-ignition in the sub chamber utilizing ignition of one ignition plug provided substantially in the center of the combustion chamber is used, so that an ignition plug is provided for each sub chamber. The configuration is simpler than in the case.

Further, in the combustion field, a large disturbing action is caused by the flame generated by the ignition of the spark plug and the flame from the sub-chamber, and a radical reaction caused by this causes a radical reaction to cause HC by gas phase quench
Is sufficiently oxidized and NOx is reduced, so that not only HC is more effectively reduced but also NOx is reduced. In addition to this, the combustion ratio immediately after the ignition timing where NOx is likely to occur, that is, at the beginning of combustion is suppressed by the presence of the protrusions, so that NOx is greatly reduced as a whole.

Further, the combustion at the outer peripheral edge of the combustion chamber is
Since it is sufficiently performed in a relatively early stage using the sub chamber, abnormal combustion occurrence in the end gas zone, which causes knocking, that is, knocking is prevented (knocking limit improvement), which is also preferable for improving engine output. Will be things.

In addition to the above, the increase in the volume of the combustion chamber due to the provision of the auxiliary chamber is also compensated by the presence of the protrusions, which is also preferable for ensuring a sufficient compression ratio.

With the structure as described in claim 2, the protrusion can be formed more easily than in the case where the protrusion is formed on the inner surface of the cylinder head having a complicated shape.
The shape of the protrusion itself becomes simple, which is advantageous in manufacturing a piston having a protrusion.

With the structure as described in claim 3, the protrusion can be formed more easily than in the case where the protrusion is formed on the inner surface of the cylinder head having a complicated shape.
This is preferable for reducing the volume of the combustion chamber in the vicinity of the spark plug, corresponding to the Pentorf type combustion chamber.

By adopting the structure described in claim 4 or 5, it is possible to sufficiently exert the effect corresponding to claim 1.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Description of FIGS . 1 to 3 FIGS . 1 to 3 show a first embodiment of the present invention. Reference numeral 1 is a combustion chamber of a reciprocating engine of a spark ignition type, and as is known, a cylinder head SH. Is formed in. The combustion chamber 1 is of a pentorf type having two inclined surfaces 1a and 1b, and a ridge line where the inclined surfaces 1a and 1b intersect is indicated by a symbol α. The ridge line α extends parallel to the crank shaft (not shown).

On one of the inclined surfaces 1a, two intake ports 2 and 3 are opened at intervals in the ridge line α direction. Further, on the other inclined surface 1b, two exhaust ports 4 and 5 are opened at intervals in the ridge line α direction. Each intake port
The ports 2 and 3 are opened to one side surface of the cylinder head SH (upper side in FIG. 1), and the exhaust ports 4 and 5 are opened to the other side surface of the cylinder head SH to be one side surface of the cylinder head SH. Intake air is introduced from the cylinder head SH
It is of a so-called cross flow type in which air is exhausted from the other side surface. Of course, although not shown, each intake port
The ports 2 and 3 and the exhaust ports 4 and 5 are opened and closed at a known timing by an umbrella valve type intake valve or exhaust valve in synchronization with the rotation of the crankshaft.

At the center of the combustion chamber 1 through which the ridge line α passes, one spark plug (ignition gap) 10 is arranged. Further, sub chambers 11 and 12 are formed in the outer peripheral edge of the combustion chamber 1 at each end of the ridge line α. That is, the two sub chambers 11 and 12 are approximately 18 in the circumferential direction of the combustion chamber.
It is configured to be arranged at 0 degree intervals. Each sub-chamber 11,
The volume of 12 is sufficiently smaller than the volume of the combustion chamber 1. Each of the sub chambers 11 and 12 has two injection holes 11a and 11b or 12a and 12b. The two injection holes 11a and 11b of the sub chamber 11 communicate the sub chamber 11 and the combustion chamber 1, and the injection holes 11a and 11b are opposite to each other in the circumferential direction of the combustion chamber and are in the combustion chamber 1 respectively.
Is oriented in a substantially tangential direction. Similarly, 2 of sub-chamber 12
The two injection holes 12a and 12b connect the sub chamber 12 and the combustion chamber 1, and the injection holes 12a and 12b are opposite to each other in the circumferential direction of the combustion chamber and are oriented substantially in the tangential direction of the combustion chamber 1, respectively. Has been done.

The sub chambers 11, 12 and the injection holes 11a, 1
1b, 12a, and 12b are configured by utilizing sub chamber constituent members 21 and 22, as described later. The sub-chamber components 21 and 22 are formed separately from the cylinder head SH, and like the spark plug 10, they are attached to the cylinder head SH from above the combustion chamber 1 by screwing. . By adopting such a mounting method of the sub chamber constituent members 21 and 22 from above, it is preferable in terms of maintainability.

On the other hand, a projection 52 is formed on the top surface of the piston 51, as shown in FIGS. That is, the protrusion 52 is formed in a columnar shape having a smaller diameter than the piston 51, and is formed to have the same axis as the axis of the piston 51. The top surface of the piston other than the protrusion 52 is a flat surface. The piston 51 having such a protruding portion 52 can be integrally formed at the same time when the piston 51 is cast, or the protruding portion 52 that is previously formed as a separate body can be formed by being integrated with the piston 51. it can.

The size of the protrusion 52 is formed so as to satisfy the following relationship. That is, the piston 5
Consider the case where 1 is at the top dead center position as shown in FIG.
At this time, the maximum outer circumference of the protrusion 52 is defined as an imaginary line E1 extending in the axial direction of the piston 51 (the imaginary line E1 is cylindrical), and the combustion chamber 1 is located inside the imaginary line E1. And the outer combustion chamber 1B, which is outside the imaginary line E1. Of course, the inner combustion chamber 1A is a portion where the spark plug 10 is located, and the outer volume combustion chamber 1B is a ring-shaped portion where the sub chambers 11 and 12 are located. And
The size (height and diameter) of the protrusion 52 is set such that the volume of the inner combustion chamber 1A is sufficiently smaller than the volume of the outer combustion chamber 1B.

In the above structure, the spark plug 1
At 0, the air-fuel mixture supplied into the combustion chamber 1 is ignited. The flame generated by the ignition of the spark plug 10 (hereinafter referred to as the main flame) spreads annularly toward the outer peripheral edge of the combustion chamber with the spark plug 10 as the center, and the inner side of the main flame facing the outer peripheral edge of the combustion chamber. The portion becomes a burned portion K1 as shown in FIG.

The pressure in the combustion chamber 1 rises due to the flame propagation of the main flame, but the pressure in the sub chambers 11 and 12 is
The pressure of the combustion chamber 1 becomes smaller than that of the combustion chamber 1 due to the throttling action of the la, la, b, and a. Due to the pressure difference between the combustion chamber 1 and the sub chambers 11 and 12, a strong flow is generated from the combustion chamber 1 to the sub chambers 11 and 12, and the sub chambers 11 and 12 are generated.
The internal turbulence energy is increased. Further, since the high-temperature air-fuel mixture containing a large amount of radicals in the pre-reaction zone of the main flame (indicated by K2 in FIG. 1) flows into the sub-chambers 11 and 12, the air-fuel mixture inside the sub-chambers 11 and 12 is The temperature rises,
And activate.

Through the above process, the sub-chamber interior 11,
Twelve mixtures are self-ignited. The combustion in the sub-chambers 11 and 12 which is self-ignited is in a high turbulence, high temperature, and highly activated state, so it is very fast, and the pressure increase rate is higher than the pressure increase rate in the combustion chamber 1. Become. Therefore, sub-chamber 1
From 1 and 12, injection holes 11a, 11b, 12a and 12b
Through, a flame is ejected into the combustion chamber 1 to generate a flame (a flame ejected from the sub chambers 11 and 12 is hereinafter referred to as a sub flame and is indicated by reference numeral K3 in FIG. 1).

The auxiliary flames ejected from the auxiliary chambers 11 and 12 are
Since it grows vigorously along the outer peripheral edge of the combustion chamber, HC that tends to occur at the outer peripheral edge of the combustion chamber is greatly reduced. In particular,
The self-ignition in the sub chambers 11 and 12 can be carried out at an early stage such that the combustion rate in the main flame is about 10% or less. Therefore, before the main flame grows sufficiently, the sub flames are matched with each other in the circumferential direction of the combustion chamber (reduction of the flame area of the sub flame) to form an annular flame. After this, an annular secondary flame grows toward the center of the combustion chamber,
It is combined with the main flame that grows toward the outer peripheral edge of the combustion chamber.

A major disturbing action occurs in the combustion chamber 1 due to the main flame and the sub flame, but at this time, oxidation and reduction reactions utilizing radicals in each flame, for example, the following reactions are promoted. That is, NOx and HC due to gas phase quench in the main flame react with OH radicals as follows. HC + OH radical = H ₂ O + CO ₂ NOx + OH radical = H ₂ O + N ₂

In this way, not only HC is further reduced significantly, but NOx is also reduced.
Further, since the auxiliary flame sufficiently burns the outer peripheral edge of the combustion chamber at a timing relatively early in combustion, abnormal combustion, that is, knocking, in the outer peripheral edge of the combustion chamber is prevented. Moreover, since the combustion in the latter stage of combustion can be ended early, the ignition timing can be retarded by this amount, which is more advantageous in terms of preventing knocking.

Further, since the piston 51 is near the top dead center and the volume of the inner combustion chamber 1A is small at the beginning of combustion immediately after ignition by the spark plug 10,
The combustion rate at the initial stage of combustion becomes sufficiently small (the maximum heat generation rate is suppressed), and the NOx production itself that tends to occur at the initial stage of combustion is greatly reduced.

The sub chambers 11 and 12 (the injection holes 11a to 12)
b) is set at almost the same height position as (the ignition gap of) the spark plug 10 and is on a straight line connecting the sub chambers 11 and 12 and the spark plug 10 when the piston 51 is at the top dead center. The sub-chambers 11 and 1 should be arranged so that the protrusions 51 do not exist.
It is set so that the self-ignition timing in 2 will be sufficiently early.

Description of FIG . 4 FIG . 4 shows another embodiment of the present invention. The same components as those of the above embodiment are designated by the same reference numerals and the description thereof will be omitted. In the present embodiment, in consideration of the fact that the combustion chamber 1 is formed in a pentorf type shape, the protrusion 53 formed on the top surface of the piston 51 is also a pentorf type. That is, the protrusion 53 is formed on the one inclined surface 1 of the combustion chamber 1.
It has a first inclined surface 53a that faces a, and a second inclined surface 53b that faces the other inclined surface 1b of the combustion chamber 1.

In FIG. 4, T1 shows the shape in which the upper piston shape is projected in the direction of the ridge line α, and T2 shows the shape in which the upper piston shape is projected in the direction orthogonal to the ridge line α. As described above, by forming the protrusion 53 into a pentorf type matching the shape of the combustion chamber 1, the volume of the inner combustion chamber 1A when the piston 51 is at the top dead center is sufficiently reduced to reduce NOx. Is preferable for sufficiently performing the above.

Description of FIG . 5 FIG . 5 shows a structural example of the sub-chamber constituting members 21 and 22. Since both 21 and 22 are constructed in the same manner, the sub-chamber constituting member 21 will be explained. To do. First, the sub-chamber constituent member 21 basically includes a main member 25 and a fixing member 26.
It is divided. The main body member 25 is in the form of a low cylinder having an opening on the base end side. The tip end side of the main body member 25 has a substantially conical shape, and injection holes 11a and 11b are formed on the side surface near the tip end portion. And the main body member 2
The base end side of 5 is a flange part 25a having a larger diameter than the other parts.

The fixing member 26 has a large-diameter portion 26a, a medium-diameter portion 26b, and a small-diameter portion 26c, which are arranged in this order from the upper side to the lower side. The middle diameter portion 26b is the flange portion 25a of the main body member 25.
The diameter is slightly larger than that of the male thread 2
6d is formed. The large diameter portion 26a has a nut (bolt head) shape. Further, the small diameter portion 26c is
The body member 25 has the same diameter as the inner diameter of the body member 25.
A predetermined depth is inserted therein to secure a predetermined volume of the sub chamber 11 in cooperation with the main body member 25 (the lower surface of the small diameter portion 26c constitutes the upper surface of the sub chamber 11).

The cylinder head SH is provided with a mounting hole 27 which opens to the combustion chamber 1. The mounting hole 27 has a small diameter portion 27a on the side close to the combustion chamber 1 and a large diameter portion 2 on the far side.
7b. The large diameter portion 27b is formed with a female screw portion 27d into which the male screw portion 26d of the fixing member 26 is screwed.

The body member 25 is inserted into the small-diameter portion 27a of the mounting hole 27 exactly, and the flange portion 25a of the body member 25 is inserted into the small-diameter portion 27a and 27b of the mounting hole 27 for a predetermined insertion or more. It is regulated by contacting the step portion 27c between them. However, the step portion 27c and the flange portion 25a
A gasket 28 made of a metal plate such as a copper plate is interposed between the and. In this state, the fixing member 26 is attached to the cylinder head SH while screwing the male screw portion 26d into the female screw portion 27d of the mounting hole 27. Then, the fixing member 26 screwed into the cylinder head SH applies a predetermined pressing force to the main body member 25, and the mounting is completed.

Here, by adjusting the amount of protrusion of the main body member 25 with respect to the combustion chamber 1, it is possible to adjust (control) the timing of self-ignition in the sub chamber 11. In this case, the protrusion amount can be adjusted by changing the length of the main body portion 25, but it is easy to adjust the protrusion amount by changing the thickness of the gasket 28.

Further, depending on the type of engine, etc., the sub chamber 1
When the volume of No. 1 is changed, the sub-chamber volume can be easily changed by changing the length (insertion depth) of the small diameter portion 26c of the fixing member 26 while using the main body member 25 in common. The main body member 25 and the fixing member 26 may be previously integrated by welding or the like before mounting the cylinder head SH.

Although the embodiments have been described above, the present invention is not limited to this, and includes, for example, the following cases. (1) Only one sub chamber may be provided for one combustion chamber, or three or more sub chambers may be provided at substantially equal intervals in the circumferential direction of the combustion chamber. In addition, one injection chamber may have only one injection hole or three or more injection holes. When the number of injection holes is one, the opening direction of the injection holes with respect to the combustion chamber is the direction in which the intake swirl flows, that is, the direction in which the auxiliary swirl promotes the growth of the secondary flame in the combustion chamber circumferential direction. It is preferable to open at

In any case, the number of sub chambers and the number of injection holes are
It is preferable to set the secondary flame to grow so as to cover the entire outer peripheral edge portion of the combustion chamber 1 (ring-shaped secondary flame generation) early after ignition by the spark plug (before the main flame is faced, the secondary flame is generated. Is set to generate an annular flame front). In addition, sub-chamber 1
Since the smaller the volume of 1 and 12 is, the earlier the time of self-ignition, the number of sub-chambers, the arrangement position,
The number of injection holes, etc. can be set.

(2) The shape of the combustion chamber is not limited to the pentorf shape, but may be any suitable shape such as a hemispherical shape or a wedge shape. (3) The sub-chambers 11 and 12 can also be formed by casting sub-chamber constituent members formed separately from the cylinder head during casting of the cylinder head. In addition, sub-chambers 11, 1
2 can also be formed at the same time when the cylinder head SH is cast. (4) The sub chamber constituent members 21 and 22 may be attached to the cylinder head SH from the side of the combustion chamber 1.
In this case, the sub chamber constituent members 21 and 22 can be attached at the time of assembling the cylinder head SH and the cylinder block while being held by a holding member interposed between the cylinder head SH and the cylinder block. . (5) Protrusions corresponding to the protrusions 52 and 53 may be formed on the inner surface of the cylinder head SH. In this case, the protrusions may be formed in an annular shape so as to surround the spark plug 10. A notch is partially formed on the projection on the straight line connecting the spark plug 10 and the sub-chambers 11 and 12, so that the influence of the flame ignited by the spark plug 10 can quickly act on the sub-chambers 11 and 12. The self-ignition timing in the sub chambers 11 and 12 can be set sufficiently early.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, and is a simplified plan view of a cylinder head when viewed from the lower surface side thereof,

FIG. 2 is a sectional view taken along line X2-X2 of FIG.

FIG. 3 is a perspective view showing an example of the shape of a protrusion formed on the top surface of the piston.

FIG. 4 is a view showing another example of the shape of the protrusion formed on the top surface of the piston.

FIG. 5 is a sectional view showing an example of a sub chamber constituent member.

[Explanation of symbols]

 1: Combustion chamber 1a: One inclined surface 1b: The other inclined surface 1A: Inner combustion chamber 1B: Outer combustion chamber 10: Spark plug 11, 12: Sub chambers 11a to 12b: Injection hole 51: Piston 52: Projection portion 53 : Protrusion 53a: inclined surface 53b: inclined surface

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location F02B 23/08 B W Y F02F 3/28 B (72) Inventor Hiroyuki Yamamoto Fuchu Town, Aki District, Hiroshima Prefecture Shinchi 3-1, Mazda Co., Ltd. (72) Inventor, Kaei Nakayama Fuchu-cho, Aki-gun, Hiroshima 3-1-1 Shinchi, Mazda Co., Ltd.

Claims (6)

[Claims] 1. A spark ignition type engine in which an ignition plug arranged in a combustion chamber ignites an air-fuel mixture supplied to the combustion chamber, wherein a sub chamber is formed at an outer peripheral edge of the combustion chamber, The sub chamber is communicated with the combustion chamber through a nozzle hole that is oriented substantially tangentially to the combustion chamber, and the spark plug is not disposed in the sub chamber but is disposed only in a substantially central portion of the combustion chamber. The ignition plug is set to perform self-ignition in the sub chamber after ignition of the air-fuel mixture by the ignition plug, and the ignition plug when the piston is at the top dead center on at least one of the upper surface of the piston and the inner surface of the cylinder head. A combustion control device for an engine, wherein a protrusion for reducing the volume of a combustion chamber in the vicinity is formed. 2. The protrusion according to claim 1, wherein the protrusion is formed in a substantially cylindrical shape on the top surface of the piston. 3. The combustion chamber shape according to claim 1, wherein the combustion chamber shape is formed as a pentorf shape having two inclined surfaces, the protrusion is formed on a piston top surface, and two inclinations of the combustion chamber are formed. Formed as a Pentorf type having two inclined surfaces facing each other. 4. The combustion chamber volume according to claim 1, wherein the volume of the combustion chamber in the portion where the protrusion is located is smaller than the volume of the combustion chamber in the portion where the protrusion is not located when the piston is at the top dead center. Is set to. 5. The sub-chamber according to claim 1, wherein a plurality of the sub-chambers are provided at substantially equal intervals in the circumferential direction of the combustion chamber, and the injection holes are opposite to each other in the circumferential direction of the combustion chamber. At least two are provided. 6. The ignition system according to claim 5, wherein after self-ignition in the sub chamber, the flames ejected from the injection holes are matched with each other to form an annular flame, and then the annular flame and the ignition plug are ignited. Matched with the flame generated by.