JPH06288331A - Combustion control device of engine - Google Patents

Abstract

PURPOSE:To form a columnar flame elongating in radial direction of a combustion chamber certainly by taking the vortex of intake air into consideration at an initial combustion. CONSTITUTION:Two intake air ports 2, 3 are opened along the ridgeline a of alpha combustion chamber 1 made up in a pent roof form. Three ignition gaps 31-33 are arranged in a series along the ridgeline alpha. Mutual flame formed by being ignited at each of ignition gaps 31-33 are united in the ridgeline alpha direction at the initial combustion and a long and narrow and approxinately colummer pillar of flame F is formed. Ignition timing of the ignition gap in a position where the rate of flow of vortex of an intake air is large within the combustion chamber 1 is made later than then that of the ignition gap of a position where the rate of flow is small. For example, if the vortex is a swirl flow, the ignition timings of the ignition gaps 31, 33 on peripheral side of the combustion chamber is made later than that of the ignition gap 32 on the center side of the combustion chamber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine combustion control device.

[0002]

2. Description of the Related Art In a spark ignition type engine in which ignition is performed by a spark plug, that is, an ignition gap, it is desired to complete combustion early in order to improve fuel efficiency. For this reason,
As disclosed in Japanese Utility Model Laid-Open No. 60-43128, it has been proposed that the combustion chamber is of a pentorf type, and three ignition gaps are arranged in series along the ridgeline thereof. This is intended to shorten the period until the combustion is completed by increasing the number of ignition gaps, but as the number of ignition gaps increases, the heat generation amount per unit time rapidly increases. , NOx is proposed to increase.

[0003]

In order to complete the combustion within a predetermined period while reducing the generation of NOx, the applicant has made the combustion rate per unit time within the combustion period as uniform as possible. We have developed a product that can reduce the peak value of the calorific value per unit time. Explaining this point in detail, three or more ignition gaps are arranged in the diametrical direction of the combustion chamber, and the flames generated by the ignition of the ignition gaps match each other in the arrangement direction of the plurality of ignition gaps. A columnar flame having a substantially columnar shape elongated in the diametrical direction was formed, and thereafter, a columnar flame was developed to grow in a direction orthogonal to the arrangement direction of a plurality of ignition gaps. By thus forming the columnar flame at the initial stage of combustion, it is possible to suppress an increase in the initial combustion ratio and a rapid increase in the subsequent combustion ratio.

As a result of various experiments on the formation of the above-mentioned columnar flame, it was found that the columnar flame could not always be formed well in the early stage of combustion. After pursuing such a cause,
It was found that this is because the vortex flow of the intake air generated in the combustion chamber causes a difference in the growth rate of the flame ignited in each ignition gap. That is, the flow velocity of the vortex flow generated in the combustion chamber is not uniform in all the combustion chambers, and a portion where the flow velocity is high and a portion where the flow velocity is low are partially formed.

For example, in swirl flow, the flow velocity at the center of the combustion chamber is smaller than the flow velocity at the peripheral portion. In the case of two tumble flows in which the vortex flows are substantially parallel to each other, the flow velocity on the central side of the combustion chamber is large and the flow velocity on the peripheral side is small in the direction orthogonal to the tumble flow.

The present invention has been made in consideration of the above circumstances, and takes into consideration the vortex flow of the intake air generated in the combustion chamber,
An object of the present invention is to provide a combustion control device for an engine, which is capable of reliably forming a substantially columnar flame that is elongated in the diameter direction of the combustion chamber in the initial stage of combustion.

[0007]

In order to achieve the above object, the present invention has the following configuration. That is, in an engine configured to generate an intake air vortex in a combustion chamber, three or more ignition gaps are arranged in series in the diameter direction of the combustion chamber for one cylinder and pass through each ignition gap. Depending on the magnitude of the flow velocity of the vortex, the ignition timing of the ignition gap arranged at the position where the flow velocity is high is set to be later than the ignition timing of the ignition gap arranged at the position where the flow velocity is small. The flames generated by the ignition of each of the ignition gaps are aligned with each other in the arrangement direction of the plurality of ignition gaps to form a substantially columnar columnar flame extending elongated in the diameter direction of the combustion chamber.

The vortex flow is set so as to be formed as two tumble flows that are spaced from each other in the combustion chamber diametrical direction, and the plurality of ignition gaps are arranged in series in a direction orthogonal to the tumble flow. Of the plurality of ignition gaps, the ignition timing of the ignition gap on the center side of the combustion chamber may be later than the ignition timing of the ignition gap on the peripheral side of the combustion chamber.

The swirl flow is set so as to be formed as a swirl flow, and the ignition timing of the ignition gap on the peripheral edge side of the combustion chamber among the plurality of ignition gaps is the ignition gap on the central side side of the combustion chamber. It can be configured to be later than the ignition timing of.

[0010]

According to the present invention, the ignition timings of the plurality of ignition gaps are optimally set in accordance with the magnitude of the flow velocity of the vortex flow of the intake air generated in the combustion chamber, and the radial direction of the combustion chamber is reliably ensured at the initial stage of combustion. It is possible to form a substantially columnar flame that extends. As a result, it is possible to complete the combustion within a desired short period while suppressing the increase of the combustion ratio in the early stage of combustion to reduce NOx.

According to claim 2 or the structure as described in claim 3, the effect obtained in claim 1 is obtained corresponding to a general tumble flow or swirl flow as a vortex flow of intake air. be able to.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes a pentorf-type combustion chamber, and a pair of inclined surfaces formed on the inner surface of the cylinder head are indicated by reference numerals 1A and 1B, and their ridge lines, that is, a pair of inclined surfaces 1A and 1B intersect each other. The line to do is indicated by the symbol α. With respect to the combustion chamber 1, two intake ports 2 and 3 are opened at a portion of one inclined surface 1A, and the other inclined surface 1 is formed.
In the portion B, two exhaust ports 4 and 5 are opened. The two intake ports 2 and 3 are arranged along the ridge line α, and similarly, the two exhaust ports 4 and 5 are also arranged along the ridge line α.

An intake passage 12 or 13 is connected to the intake ports 2 and 3, and an exhaust passage 14 or 15 is connected to the exhaust ports 4 and 5. Two intake passages 12 and 13
At least in the vicinity of the combustion chamber 1, they are configured to be independent of each other over a predetermined length.
As for 25 and 25, the portions in the vicinity of the combustion chamber 1 are independent from each other for a predetermined length.

In the combustion chamber 1, along the ridge line α, the combustion chamber 1
3 ignition gaps (ignition plugs) 3 in diametrical series
1 to 33 are arranged. The number and arrangement position of the ignition gaps are set in order to form the following columnar flame at the initial stage of combustion. That is, it is assumed that the flame propagation speed in the combustion chamber 1 does not differ from each other at each ignition gap position.

When the ignition gaps 31 to 33 are simultaneously ignited, the flames spreading around the respective ignition gaps 31 to 33 first coincide with each other in the ridge line α direction, and spread over the entire length in the diametrical direction of the combustion chamber. A columnar flame F having an elongated columnar shape is formed. After the columnar flame F is formed, the flame extends in the direction orthogonal to the ridge line α, and the combustion is completed. In such a combustion state, the combustion ratio at the initial stage of combustion is suppressed, and the flame spread area is reduced by forming the columnar flame F, and the flame area is prevented from expanding rapidly thereafter. It

In FIG. 2, the combustion state in the case of forming the above-mentioned columnar flame F is shown by a solid line, and the combustion state in the conventional case in which only one ignition gap is provided in the center of the combustion chamber 1 is indicated by a chain line. It is indicated by. As shown in this FIG.
By forming the columnar flame F, the calorific value per unit time is made as uniform as possible, that is, the peak value of the calorific value is suppressed to a small value and NOx is reduced, and the combustion period is extended. It does not happen (it is also advantageous for improving fuel efficiency).

In order to reliably form the columnar flame F shown in FIG. 1, the ignition timings of the ignition gaps 31 to 33 are set in consideration of the flow velocity of the vortex flow of the intake air in the combustion chamber 1. In other words, the ignition timing of the ignition gap where the flow velocity of the passing vortex flow is high (the flame transfer velocity increases) is delayed compared to the ignition timing of the ignition gap where the flow velocity of the passing vortex flow is low (the flame transfer velocity decreases). It By setting the ignition timing in consideration of such a flow velocity of the vortex, the columnar flame F can be reliably formed, and the above-described effect of uniform combustion can be surely obtained. By the way, when the ignition timings of the ignition gaps 31 to 33 are equalized without considering the flow velocity of the vortex, the columnar flame F is not formed, or the columnar flame F has a large collapsed shape that is not columnar. The combustion rate is increased, and the combustion period is extended. This is also unfavorable for increasing the lean burn limit.

FIG. 3 shows an example in which a swirl flow is used as the intake vortex flow. In order to generate the swirl flow, a shutter valve 21 is arranged in one of the two intake passages 12 and 13, and the shutter valve 21 is closed at least in a predetermined operation region, for example, when the load is low. To be Then, when the shutter valve 21 is closed, intake air is supplied to the combustion chamber 1 only through the intake passage 13, but the intake passage 13 is oriented along the tangential direction of the combustion chamber 1 as much as possible. As a result, a swirl flow S clockwise in the figure is formed in the combustion chamber 1. The distribution of the flow velocity in the combustion chamber 1 due to the swirl flow S is as shown in FIG. 3, in which the flow velocity is small at the center of the combustion chamber, the flow velocity is large at the peripheral edge of the combustion chamber, and the center and peripheral edge of the combustion chamber The flow velocity in the part between and becomes the largest.

Therefore, in the case of FIG. 3, the ignition timing of the ignition gap 32 located at the center of the combustion chamber 1 is set earlier than the ignition timing of the ignition gaps 31 and 33 near the peripheral portions (of 31 and 33). Ignition timing is the same). In this case, the ignition timing of the ignition gap 32 remains the basic ignition timing, and the ignition timings of the ignition gaps 31 and 33 at the positions where the flow velocity is high are retarded with respect to the basic ignition timing.

FIG. 4 shows an example in which the vortex flow of the intake air is a tumble flow. That is, the portions of the intake passages 12 and 13 in the vicinity of the combustion chamber 1 are bent so as to be along the cylinder axis as much as possible, or the intake air flows along the upper walls of the intake passages 12 and 13, respectively. Intake passage 12, 13
A deflecting plate is provided in the intake air, and the intake air supplied from the intake passages 12 and 13 is made into tumble flows T1 and T2 which are swirled in the combustion chamber 1 in a plane substantially parallel to the cylinder axis. The two tumble flows T1 and T2 are formed at intervals in the combustion chamber diametrical direction.

The ridge line α is a direction orthogonal to the tumble flows T1 and T2, and therefore, the ignition gaps 31 to 31.
The arrangement direction of 33 is a direction in which the tumble flows T1 and T2 are orthogonal to each other. The intake air flow velocity in the combustion chamber 1 becomes larger in the central portion of the combustion chamber than in the peripheral portion in the ridge α direction. Therefore, the ignition timings of the ignition gaps 31 and 33 having a low flow velocity are advanced (basic ignition timing), and the ignition timing of the ignition gap 32 having a high flow velocity is retarded later than the basic ignition timing.

Although the embodiment has been described above, the number of the plurality of ignition gaps arranged in series can be set to an appropriate number of 3 or more, but the columnar flame F is taken into consideration in consideration of cost and maintenance. Is preferably the minimum number required to form

[Brief description of drawings]

FIG. 1 is a diagram for explaining a columnar flame.

FIG. 2 is a diagram showing a combustion state using a columnar flame in comparison with a conventional state.

FIG. 3 is a view corresponding to FIG. 1 showing a case where the vortex flow is a swirl flow.

FIG. 4 is a view corresponding to FIG. 1 showing a case where the vortex flow is a tumble flow.

[Explanation of symbols]

 1: Combustion chamber 2, 3: Intake port 31-33: Ignition gap S: Swirling flow T1, T2: Tumble flow α: Ridge line F: Columnar flame

Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location F02P 13/00 302 A (72) Inventor Riki Iname, 3-1, Shinchi Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Corporation (72) Inventor Yoshihiro Kiriki 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation

Claims (3)

[Claims] 1. An engine configured to generate an intake air vortex in a combustion chamber, wherein three or more ignition gaps are arranged in series in a diameter direction of the combustion chamber for one cylinder. So that the ignition timing of the ignition gap arranged at the position where the flow velocity is high becomes later than the ignition timing of the ignition gap arranged at the position where the flow velocity is small, depending on the magnitude of the flow velocity of the vortex flow passing through. It is characterized in that the flames generated by the ignition of each of the ignition gaps are aligned with each other in the arrangement direction of the plurality of ignition gaps to form a substantially columnar flame extending elongated in the diameter direction of the combustion chamber. Engine combustion control device. 2. The vortex flow according to claim 1, wherein the vortex flow is set as two tumble flows spaced apart from each other in a combustion chamber diameter direction, and the plurality of ignition gaps are orthogonal to the tumble flow. Of the plurality of ignition gaps, the ignition timing of the ignition gap on the central side of the combustion chamber is delayed from the ignition timing of the ignition gap on the peripheral side of the combustion chamber. 3. The vortex flow is set so as to be formed as a swirl flow, and the ignition timing of the ignition gap on the peripheral edge side of the combustion chamber among the plurality of ignition gaps is the combustion center. It is delayed from the ignition timing of the ignition gap on the part side.