JP3199901B2 - Engine combustion chamber structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber structure of an engine.

[0002]

2. Description of the Related Art In recent engines, a tumble flow (longitudinal vortex) of intake air has been put into practical use in a combustion chamber in order to improve fuel efficiency particularly by performing lean combustion. This tumble flow becomes a swirl flow in a plane parallel to the cylinder axis. However, two intake ports are used, and the intake air from each intake port is used as a tumble flow. The formation of two different tumble flows is also performed.

Further, as disclosed in Japanese Utility Model Laid-Open No. 60-43128, a combustion chamber is of a pentle-shaped type, in which three ignition gaps are arranged in series along the ridge. Proposed. This attempts to shorten the period until the completion of combustion by increasing the number of ignition gaps. However, according to the above-mentioned publication, the heat generation amount per unit time increases rapidly as the number of ignition gaps increases, that is, the peak value of the heat generation amount increases, and NOx increases. Has been proposed. In particular, when performing lean combustion, NOx reduction is a major problem, and this is a problem in this respect.

[0004]

In order to complete the combustion within a predetermined period while reducing the generation of NOx, the present applicant has made the combustion ratio per unit time within the predetermined combustion period as uniform as possible. In other words, a device capable of reducing the peak value of the calorific value per unit time was developed. To explain this point in detail, a plurality of ignition gaps are arranged in the diameter direction of the combustion chamber, and the flames generated by the ignition of each ignition gap coincide with each other in the arrangement direction of the plurality of ignition gaps at the initial stage of combustion. A structure was developed in which a substantially columnar flame extending elongated in the diameter direction of the chamber was formed, and thereafter, the columnar flame was grown in a direction orthogonal to the arrangement direction of the plurality of ignition gaps. Thus, by forming a columnar flame in the early stage of combustion, the increase in the initial combustion ratio is suppressed, and the subsequent increase in the combustion ratio is suppressed.

In the case of forming a columnar flame as described above, if a tumble flow of intake air is also formed in the combustion chamber in order to further improve the lean limit, the tumble flow adversely affects the formation of the columnar flame. Sometimes. In pursuit of such a cause, the growth direction of the flame generated from each ignition gap (the direction in which the flame easily grows) is determined by the intake flow rate of the tumble flow, and the flame growth direction required for the formation of the columnar flame. It turned out to be different.

The present invention has been made in view of the above circumstances. Even when a tumble flow of intake air is formed in a combustion chamber, a columnar flame elongated in the diameter direction of the combustion chamber at the initial stage of combustion is prevented. It is an object of the present invention to provide a combustion chamber structure of an engine that can be reliably formed.

[0007]

To achieve the above object, the present invention has the following configuration as a first configuration. That is, in an engine in which a tumble flow of intake air is formed in a combustion chamber as described in claim 1 of the claims, a series is formed in series in a diameter direction of the combustion chamber and in a direction orthogonal to the tumble flow. A plurality of ignition gaps are provided, so that the flames ignited in each ignition gap are aligned with each other at the initial stage of combustion to form a substantially columnar flame extending elongated in the diameter direction of the combustion chamber. With one side of the ignition gap line composed of ignition gaps interposed therebetween,
One intake port is located and an exhaust port is located on the other, and the turning direction of the tumble flow passes through the piston top surface, the exhaust port, and the ignition gap sequentially from the intake port. The ignition gap row is offset from the center of the combustion chamber toward the exhaust port,
The mounting hole of the ignition plug having the ignition gap has an opening position with respect to the combustion chamber that is smaller than that of the ignition gap.
The ignition gap, which is set to be located on the side of the ignition plug and is inclined so as to approach the exhaust port as it approaches the combustion chamber, and which is formed at the tip of the spark plug by a predetermined amount, It is configured such that it protrudes into the combustion chamber.

In order to achieve the above object, the present invention has the following configuration as a second configuration. That is, in an engine in which a tumble flow of intake air is formed in a combustion chamber as described in claim 2 of the claims, the engine is arranged in series with each other in a diameter direction of the combustion chamber and in a direction orthogonal to the tumble flow. A plurality of ignition gaps are provided, so that the flames ignited in each ignition gap are aligned with each other at the initial stage of combustion to form a substantially columnar flame extending elongated in the diameter direction of the combustion chamber. Two intake ports spaced in the direction of the ignition gap row are located on one side and an exhaust port is located on the other side with the ignition gap row composed of the ignition gap therebetween. The direction is set so as to sequentially pass through the ignition gap, the exhaust port, and the top surface of the piston from the intake port, and the ignition gap row extends from the center of the combustion chamber. The mounting hole of the ignition plug, which is offset to the air port side and has the ignition gap, is set so that the opening position with respect to the combustion chamber is located closer to the exhaust port side than the ignition gap, and is formed in the combustion chamber. As you approach, intake port
And the ignition gap formed at the front end of the spark plug projects into the combustion chamber by a predetermined amount.

[0009]

According to the present invention, since the tumble flow flows in a direction orthogonal to the ignition gap row composed of a plurality of ignition gaps, it does not affect the growth rate of the flame in the direction of the ignition gap row. That is, depending on the tumble flow, it is possible to prevent a situation in which the flame easily grows in one direction, the other direction, or the inclined direction of the ignition gap row, and the columnar flame can be reliably formed at the beginning of combustion. Further, it is preferable to set a tumble flow as a flow in a direction orthogonal to the ignition gap row while using a general intake two-valve type as a recent engine. further,
After the columnar flame is formed, a flame that grows in a direction orthogonal to the columnar flame, that is, a flame that grows in one direction and a flame that grows in the other direction in the orthogonal direction, is subjected to a tumble flow. Considering the effect of the gas on the flame growth rate, it is preferable to simultaneously reach the periphery of the combustion chamber. In addition to the above, it is possible to position the ignition gap at a desired position while solving the difficulty of mounting the spark plug near the exhaust port (the invention according to claim 1). Further, the ignition gap can be located at a desired position while solving the difficulty of mounting the spark plug near the intake port.
Invention).

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings, including the principle of producing a columnar flame, comparative examples and reference examples. DESCRIPTION OF THE PRIORITY OF GENERATING COLUMN FLAME In FIG. 1, reference numeral 1 denotes a pen-tooth-shaped combustion chamber, and a pair of inclined surfaces formed on the inner surface of a cylinder head are denoted by 1A.
1B, its ridges, ie, a pair of inclined surfaces 1A and 1B
Is indicated by the symbol α. For the combustion chamber 1, two intake ports 2, 3 are opened on one inclined surface 1A, and two exhaust ports 4, 5 are opened on the other inclined surface 1B. Two intake ports
Ports 2 and 3 are arranged along ridge line α, and similarly, two exhaust ports 4 and 5 are also disposed along 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
The two exhaust passages 24 are formed independently of each other at least in the vicinity of the combustion chamber 1 over a predetermined length.
Also, the parts near the combustion chamber 1 are independent of each other over a predetermined length.

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

When the ignition is performed simultaneously in each of the ignition gaps 31 to 33, the flames spreading around the ignition gaps 31 to 33 first coincide with each other in the direction of the ridge line α, and extend over the entire length in the diameter direction of the combustion chamber. A substantially columnar columnar flame F that is elongated is formed. After the formation of the columnar flame F, the flame extends in a direction orthogonal to the ridgeline α, and the combustion is completed. In such a combustion state, the combustion ratio in the initial stage of combustion is suppressed, and particularly, the flame propagation area is reduced by being made into a columnar flame F, and thereafter, the flame area is prevented from rapidly expanding. You.

In FIG. 2, the combustion state when the above-described columnar flame F is formed is shown by a solid line (ideal state).
The state of combustion in the conventional case where only one ignition gap is provided at the center of the combustion chamber 1 is indicated by a dashed line. As shown in FIG. 2, 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 to reduce NOx. In addition, the combustion period is not prolonged (advantageous in improving fuel efficiency).

In order to reliably form the columnar flame F shown in FIG. 1, the arrangement direction of the ignition gaps 31 to 33 is set in consideration of the tumble flow of the intake air in the combustion chamber 1. That is, the intake air supplied from each of the intake passages 12 and 13 is bent in the intake passages 12 and 13 so as to be tumble flows (longitudinal vortices) T1 and T2 swirled in a plane parallel to the cylinder axis. The tumble flows T1 and T2 are flows in a plane parallel to the cylinder axis and extending in the direction of the extension of the intake passages 12 and 13. That is, the tumble flows T1 and T2 are
Direction perpendicular to each intake passage ridge line α (ignition gaps 31 to
33 (a direction orthogonal to the arrangement direction). Therefore, the tumble flow does not substantially affect the flame propagation speed in the arrangement direction of the ignition gaps 31 to 33. Therefore, if the distance between the ignition gaps (the number of ignition gaps) is set so that the columnar flame F can be formed at a desired time, the columnar flame can be surely formed without being affected by the tumble flow. Become.

Incidentally, assuming that the direction of the tumble flow is shifted by 90 degrees in FIG.
The growth rate of the flame generated in 3 increases in the direction of flow of the tumble flow, but the growth rate decreases on the opposite side.
It is difficult to form the columnar flame F early over the entire length of the combustion chamber in the diameter direction. When the direction of the tumble flow is inclined at 45 degrees or the like with respect to the ignition gap row, it is difficult to form the columnar flame itself. In addition to the above, the momentum of the tumble flow varies depending on the operating state of the engine, so that it is even more difficult to always reliably form a columnar flame over a wide operating range.

First Embodiment FIGS. 3 and 5 show a first embodiment of the present invention.
In the following description, the ignition gaps 31 to 3 shown in FIG.
The spark plugs corresponding to No. 3 are denoted by reference signs A, such as 31A to 33A. In this embodiment, FIG.
As shown in FIG. 5, the tumble flow T1 (T2) is turned clockwise in FIG. 5, that is, from the intake port 2 (3), through the top surface of the piston 41, through the exhaust ports 4, 5, and through the ignition gaps 31 to 3.
3. For this reason, the inside of the intake passage 12 (13) near the intake port 2 (3) is divided into an upper passage 2A (3A) and a lower passage 2B (3B) by a partition wall 42, and the upper passage 2A (3A). ) Is closed by an on-off valve 43. The on-off valve 4
3 is closed only in the partial load range and is open in the full load range.

The ignition gaps 31 to 33 are offset from the center of the combustion chamber toward the exhaust ports 4 and 5 so that the effective opening areas of the intake ports 2 and 3 can be secured by this amount. is there. A squish area 44 is formed at the periphery of the combustion chamber on the side of the exhaust ports 4 and 5. In the figure, 51 is a cylinder head, 52 is a cylinder block, 53 is a fuel injection valve, and 54 is an intake valve.

In this embodiment, after the columnar flame is formed,
In the direction orthogonal to the columnar flame, the distance between the columnar flame (which may be considered as an ignition gap array) and the peripheral edge of the combustion chamber on the right side of FIG. 3 is large, and the distance between the peripheral side of the combustion chamber on the left side of FIG. 3 is small. Becomes The tumble flow as shown in FIG. 5 tends to push the columnar flame toward the intake ports 2 and 3 and, among the flames that grow in the direction orthogonal to the columnar flame, the intake port The flame growth speed to the ports 2 and 3 is increased, and the flame growth speed to the exhaust ports 4 and 5 is suppressed to a small value.

However, since the ignition gap row is offset toward the exhaust ports 4 and 5, the flame growing in the direction perpendicular to the columnar flame reaches the periphery of the combustion chamber almost at the same time. . In addition, the flame growth toward the squish area 44 is promoted by the reverse squish flow toward the squish area 44 generated by the lowering of the piston 41, and the flame growing in the direction orthogonal to the columnar flame is simultaneously generated. This is more preferable in reaching the periphery of the combustion chamber. Note that it is also possible to adopt only the offset of the ignition gap row to the exhaust port side and not to adopt the formation of the squish area 44.

Here, as shown in FIG. 4 as a comparative example, in order to position the ignition gaps 31 to 33 near the exhaust ports 4 and 5 and to mount the spark plug straight from above, it is necessary to use an exhaust port. -In order to prevent interference with various parts at and around the ports 4, 5 and the like, the design is greatly restricted (the reference numeral 53 in FIG. 4 denotes a fuel injection valve). In particular, the ignition gap 3 on the periphery of the combustion chamber
Such problems are apt to become prominent with respect to Nos. 1 and 33.
For this reason, as shown in the arrows of FIG. 3 and FIG. 5, the mounting holes 31B (33B) of the ignition plugs 31A (33A) for the ignition gaps 31 (33) are moved toward the exhaust ports 4, 5 as the combustion chamber 1 is approached. It is preferable that the tip of the spark plug 31A (33A), that is, the ignition gap 31 (33), protrudes by a predetermined amount into the combustion chamber while being formed so as to be inclined toward the side. In this case, the spark plug mounting hole 31B (3
The opening position of the combustion chamber 1 in FIG.
The position is closer to the intake ports 2 and 3 than the position 1 (33). The center ignition gap 32 can also be mounted in an inclined manner similar to the above-described ignition gaps 31 and 33.

Second Embodiment FIGS. 6 and 7 show a second embodiment of the present invention. In the present embodiment, the partition 42 shown in FIGS.
The turning directions of the tumble flows T1 and T2 are set to be opposite to those shown in FIGS. That is, the intake air from the intake port 2 (3) is directed to flow to the top surface of the piston 41 through the ignition gaps 31 to 33 and the exhaust ports 4 and 5. For this reason, the ignition gap row
Although it is offset toward the intake ports 2 and 3, the meaning of this offset is the same as in the case of FIGS. 3 and 4 described above. Also in the case of this embodiment, as in the case of FIGS. 3 and 5, the ignition plugs 31A and 33A are attached at an angle, and the ignition gaps 31 and 33 are projected into the combustion chamber 1 by a predetermined amount.

Reference Example 1 FIGS. 8 and 9 show Reference Example 1. FIG. That is, the ignition gaps 31, 3 located at each end of the ignition gap row
3 is located at or near the periphery of the combustion chamber 1. At the periphery of the combustion chamber located in a direction perpendicular to the row of ignition gaps, there are squish areas 61 and 62 which are considerably long in the circumferential direction of the combustion chamber and extend over the intake ports 2, 3 or the exhaust ports 4, 5, respectively. Is formed. Further, small squish areas 63 and 64 are formed at the periphery of the combustion chamber at each end of the ignition gap 3133 in the arrangement direction.

When the piston 41 rises, a squish flow S1 is generated from the squish areas 63, 64 toward the ignition gap 31 or 33, and the ignition gap 31,
The flame generated at 33 is quickly grown toward the adjacent ignition gap 32. Thereby, the ignition gaps 31, 3
By increasing the distance to the ignition gap 32 due to the position of 3 near the periphery of the combustion chamber, the generation timing of the columnar flame is prevented from being delayed.

Further, when the piston rises, the squish flow S2 generated in the squish areas 61 and 62 suppresses the growth of the flame in the direction orthogonal to the ignition gap row, thereby reducing the combustion ratio at the beginning of combustion. Above. When the piston 41 descends, the reverse squish flow S4 flowing in the direction opposite to the squish flow S2 promotes the flame growth in the direction orthogonal to the columnar flame after the columnar flame is formed, and the combustion is started. This is preferable in terms of early completion.

Reference Example 2 FIGS. 10 and 11 show Reference Example 2. FIG. That is, the protrusion 71 is formed on the top surface of the piston 41. The protruding portion 71 is formed as a prism having a rectangular cross section which extends in the direction in which the ignition gaps 31 to 33 are arranged, and is formed over the entire diameter of the piston 41. The position at which the projection 71 is formed is a position facing the ignition gap.
To 33 are included. And the inclined surface 1A obtained in relation to the pentle-shaped combustion chamber,
1B, the distance between the top surface of the piston 41 and the upper wall of the combustion chamber 1 in the direction perpendicular to the longitudinal direction of the projection 71 is gradually reduced toward the periphery of the combustion chamber. I have.

Here, the interval between the ignition gaps 31 and 32 and the interval between 32 and 33 are set to the same interval L. The distance between (the top surface of) the projection 71 and the ignition gaps 31 to 33 when the piston 41 is at the top dead center is H
, The dimensions are set so that the relationship of H ≦ L / 2 is satisfied. In other words, the flame reaches the projection 71 in the cylinder axis direction until the adjacent flames match to form a columnar flame.

With the above configuration, in the initial stage of combustion until the formation of the columnar flame, the flame is prevented from proceeding in the cylinder axial direction by the projection 71, and the combustion ratio until the columnar flame is generated is reduced. Things. In particular, by setting the dimensions L and H described above, it is preferable to suppress the combustion in the cylinder axis direction until the columnar flame is generated. Also,
After the columnar flame is formed, the flame (flame area) that grows in the direction orthogonal to the columnar flame gradually increases in the circumferential direction of the combustion chamber, while gradually decreases in the height direction of the combustion chamber. Therefore, it is preferable to maintain the flame area as constant as possible to obtain a uniform combustion ratio.

Reference Example 3 FIGS. 12 and 13 show Reference Example 3. FIG. That is, the projection 81 is formed on the top surface of the piston 41 as in the case of FIGS. The shape of the projection 81 is the same as that of FIGS. 10 and 11 on the top surface 81a, but the side surface 81b in the direction orthogonal to the longitudinal direction (ignition gap row direction) is formed on the outer peripheral edge of the piston. It is set to gradually lower toward. Thereby, compared with the case of FIGS. 10 and 11, the interval between the piston top surface and the upper wall of the combustion chamber is increased by using the inclined surfaces 1A and 1B.
It can be even smoother and progressively smaller. The relationship between the dimensions L and H is set in the same manner as in FIGS.

Although the embodiment has been described including the comparative example and the reference example, the number of the plurality of ignition gaps arranged in series can be set to an appropriate number, but cost and maintenance are taken into consideration. Then, it is preferable to set the minimum number necessary to form the columnar flame F. Also, the present invention
The present invention can be applied to a case where there is one intake port and one tumble flow is formed in the combustion chamber.

[Brief description of the drawings]

FIG. 1 is a simplified plan view of a combustion chamber showing the principle of columnar flame generation.

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

FIG. 3 is a view showing a first embodiment of the present invention and corresponding to FIG. 1;

FIG. 4 is a view showing a longitudinal sectional structure of a combustion chamber showing a comparative example with respect to FIG. 5;

FIG. 5 is a view showing a vertical sectional structure of a combustion chamber in FIG. 3;

FIG. 6 is a view showing a second embodiment of the present invention and corresponding to FIG. 1;

FIG. 7 is a view showing a vertical sectional structure of a combustion chamber in FIG. 6;

FIG. 8 shows Reference Example 1, and corresponds to FIG.

FIG. 9 is a view showing a vertical cross-sectional structure of the combustion chamber in FIG. 8;

FIG. 10 is a view showing Reference Example 2 and showing a longitudinal sectional structure of a combustion chamber.

11 is a view of the piston in FIG. 10 as viewed from the top surface side.

FIG. 12 is a view showing Reference Example 3 and showing a longitudinal sectional structure of a combustion chamber.

13 is a view of the piston in FIG. 12 when viewed from the right or left side in FIG.

[Explanation of symbols]

 1: Combustion chamber 2, 3: Intake port 4, 4: Exhaust port 31-33: Ignition gap 44: Squish area 61-64: Squish area 71, 81: Projection 81a: Top surface 81b: Side surface α : Ridge line F: Columnar flame T1, T2: Tumble flow S1, S2: Squish flow S4: Reverse squish flow

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02P 13/00 302 F02P 13/00 302A (72) Inventor Tsutomu Iname 3-1, Fuchi-cho, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation (72) Inventor Yoshihiro Kiriki 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References JP-A-4-365926 (JP, A) JP-A-5-59953 (JP, A JP-A-4-287871 (JP, A) JP-A-60-43128 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02P 15/08 F02B 23/08 F02B 31 / 02 F02P 13/00

Claims (2)

(57) [Claims] 1. An engine in which a tumble flow of intake air is formed in a combustion chamber, wherein a plurality of ignition gaps are arranged in series in a diameter direction of the combustion chamber and in a direction orthogonal to the tumble flow. flame which is ignited by the spark gaps are adapted to form a substantially columnar columnar flame extending elongated in matched combustion chamber diameter directions during initial combustion, across the spark gap sequence composed of the plurality of spark gaps
And one of the two suction gaps spaced in the direction of the ignition gap row.
The exhaust port is located while the exhaust port is located
Is, the turning direction of the tumble flow, the intake port - order from DOO
Next, pass through the piston top surface, exhaust port, and ignition gap.
The direction of the ignition gap is set such that the ignition gap row extends from the center of the combustion chamber to the exhaust port side.
The mounting hole of the spark plug , which is offset and has the ignition gap,
The opening position with respect to the chamber is larger than the ignition gap in the intake port.
To the combustion chamber and close to the combustion chamber.
As it approaches the exhaust port.
The ignition gap formed at the tip of the ignition plug
Is protruded into the combustion chamber by a predetermined amount . 2. A method for forming a tumble flow of intake air in a combustion chamber.
In the direction of the diameter of the combustion chamber and orthogonal to the tumble flow
In, a plurality of ignition gaps are arranged in series with each other
The flame ignited in each ignition gap
Columns that extend in the direction of the diameter of the combustion chamber
To form a columnar flame, and sandwich an ignition gap row composed of the plurality of ignition gaps.
And one of the two suction gaps spaced in the direction of the ignition gap row.
The exhaust port is located while the exhaust port is located
Is, the turning direction of the tumble flow, the intake port - order from DOO
Next, pass through the ignition gap, exhaust port and piston top surface.
The direction of the ignition gap is set such that the ignition gap row extends from the center of the combustion chamber to the intake port side.
The mounting hole of the spark plug , which is offset and has the ignition gap,
The position of the opening with respect to the chamber is higher than that of the ignition gap.
To the combustion chamber and close to the combustion chamber.
As it approaches the intake port.
The ignition gap formed at the tip of the ignition plug
Is protruded into the combustion chamber by a predetermined amount .