JP2010144601A - Combustion chamber structure of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustion chamber structure of an engine capable of providing high heat efficiency. <P>SOLUTION: This combustion chamber structure of an engine includes a plurality of ignition parts 25 provided on the same diameter as a combustion chamber in a combustion chamber and tubular hole parts 11 which are provided near the ignition parts 25, respectively, and respectively have openings 11a formed at the positions to which the flame of the ignited air-fuel mixture propagates and bottoms 11c for closing the opposite ends of the openings 11a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a combustion chamber structure of an engine.

Various structures have been proposed for engine combustion chambers. For example, Patent Document 1 discloses a combustion chamber structure having a sub-combustion chamber.
JP-A-6-42411

  However, in the above-described conventional structure, the combustion in the auxiliary combustion chamber becomes an external combustion engine that burns outside the main combustion chamber. For this reason, there is a problem that energy loss due to cooling is large and thermal efficiency is low.

  The present invention has been made paying attention to such a conventional problem, and an object of the present invention is to provide an engine combustion chamber structure capable of obtaining high thermal efficiency.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention provides a plurality of ignition parts (25) provided in the combustion chamber on the same diameter as the combustion chamber, and a position near the ignition part, where the flame of the ignited mixture propagates. A cylindrical hole portion (11) including the formed opening (11a) and a bottom (11c) closing the opposite end of the opening is provided.

  According to the present invention, when the flame of the ignited air-fuel mixture passes through the opening inside the cylinder, high-speed gas is ejected from the opening to promote diffusion of unburned gas in the combustion chamber. Furthermore, since a plurality of ignition parts are provided in the combustion chamber on the same diameter as the combustion chamber, combustion in the outer peripheral region where unburned gas tends to accumulate in the combustion chamber is promoted. In addition, since the flame is propagated from the plurality of ignition parts, it is easy to generate a gas ejected from the inside of the cylinder, and a synergistic effect of combustion promotion and diffusion of unburned gas is obtained. These increase the combustion speed in the cylinder, shorten the combustion period, and increase the thermal efficiency.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a view showing a first embodiment of a combustion chamber structure of an engine according to the present invention. FIG. 1 (A) is a perspective view of the combustion chamber from above, and FIG. 1 (B) is a side view of the combustion chamber. FIG.

  The engine combustion chamber 10 is exemplified by a so-called pent roof type in the present embodiment. A ceiling spark plug 30 is provided on the pent roof ridgeline. An intake valve 31 is provided on one roof (the right roof in FIG. 1) across the pent roof ridgeline. An exhaust valve 32 is provided on the other roof (the left roof in FIG. 1) across the pent roof ridge line. Those skilled in the art of engine use the expression top dead center / bottom dead center separately from the direction of gravity. In a horizontally opposed engine, etc., the top dead center is not necessarily above the gravity direction and the bottom dead center is not below the gravity direction. If the engine is inverted, the top dead center is below the gravity direction. The bottom dead center is above the gravity direction. In the present specification, according to the custom, the top dead center side is up, the bottom dead center side is down, and the upper part of the combustion chamber is expressed as a roof.

  An ignition unit 25 is provided on the outer periphery of the combustion chamber 10 of the engine. In this embodiment, the outer periphery ignition part 25 is a discharge gap formed in the annular ignition plug 20 shown in FIG. In FIG. 1, the ignition part is illustrated in the form of a normal ignition plug according to the image of the ignition part, but details will be described later with reference to FIG. 2.

  In the present embodiment, four ignition parts 25 are provided. A cylindrical hole portion 11 is formed between one ignition portion 25 and another ignition portion 25.

  The cylindrical hole portion 11 is formed in a biased manner in one ignition portion 25, not in the middle of one ignition portion 25 and another ignition portion 25. The cylindrical hole portion 11 includes an opening 11a formed at a position where the flame of the ignited air-fuel mixture propagates, and a bottom 11c that closes the opposite end of the opening 11a. The direction of the axis A of the cylindrical hole portion 11 is the radial direction of the combustion chamber 10. With this arrangement, the axis A of the cylindrical hole portion 11 intersects with the straight line B connecting the center 11b of the opening 11a and the ignition portion 25 and does not coincide with the straight line B. Further, the hole diameter (diameter) d of the opening 11a in the cylinder interior 11 and the depth L of the cylinder hole 11 are set so that the ratio L / d of the depth L to the diameter d of the cylinder hole 11 is larger than 6. Is done. For example, the hole diameter (diameter) d of the opening 11a in the cylinder interior 11 is 1 mm, and the depth L is 10 mm.

  FIG. 2 is a perspective view showing an annular spark plug.

  The annular spark plug 20 includes an annular body 21, a center electrode 22, a conductive portion 23, and a ground 24.

  The annular body 21 is made of an insulating material such as ceramic.

  The center electrode 22 is an elongated rod-like electrode made of a heat-resistant and conductive material such as platinum (Pt) or iridium (Ir). The tip of the center electrode 22 is located on the inner peripheral surface 21 a of the annular body 21. Although not shown, the center electrode 22 is connected to the ignition coil.

  The conductive portion 23 is formed in a rectangular shape by depositing a heat-resistant and conductive material such as platinum (Pt) or iridium (Ir) on the inner peripheral surface 21 a of the annular body 21. In the present embodiment, four conductive portions 23a to 23d are provided. The four conductive portions 23 a to 23 d are provided in a row at a predetermined interval on the inner peripheral surface 21 a of the annular body 21 with the tip of the center electrode 22 as the head. Of the conductive portions 23 a and 23 d located on both sides of the center electrode 22, one conductive portion 23 a is adjacent to the center electrode 22 to form a discharge gap 25 a. The other conductive portion 23d is sufficiently separated from the center electrode 22 than the one conductive portion 23a. For this reason, even if a voltage is applied to the center electrode 22, no discharge occurs between the center electrode 22 and the conductive portion 23d. The distance between the tip 22a of the center electrode 22 and the upper surface 21b and the lower surface 21c of the annular body 21 is sufficiently larger than the distance between the tip 22a of the center electrode 22 and the conductive portion 23a. Three discharge gaps 25b to 25d are formed between the conductive portions 23 adjacent to each other. The gap amounts of the three discharge gaps 25b to 25d are all equal. Further, the discharge gap 25a is formed so as to be substantially equal to the gap amount.

  In the annular spark plug 20, the energy amount is determined by the sum of the gap amounts of the discharge gaps 25a to 25d, that is, the sum of the gap amounts. Then, the cylindrical hole portion 11 is formed at a predetermined position of the conductive portion 23.

  The ground 24 allows the voltage applied to the center electrode 22 to escape to the cylinder head. The ground 24 is formed so as to be continuous with the conductive portion 23 d spaced from the center electrode 22 among the conductive portions 23 a and 23 d located on both sides of the center electrode 22. Similarly to the conductive portion 23, the ground 24 is formed from the inner peripheral surface 21a to the upper surface 21b of the annular body 21 by vapor-depositing a heat-resistant and conductive material such as platinum (Pt) or iridium (Ir). It is formed. When the portion attached to the upper surface 21b of the annular body 21 contacts the cylinder head, the voltage applied to the center electrode 22 is released to the cylinder head.

  When the annular spark plug 20 having such a structure is used, the ignition coil energy is received and the sparks are ignited in the respective discharge gaps 25a to 25d, so that multipoint ignition can be performed.

  Next, the effect of this embodiment is demonstrated with reference to FIGS. FIG. 3 is a view showing a basic combustion chamber structure for facilitating understanding of the operational effects of the present embodiment.

  In the combustion chamber 10 shown in FIG. 3, one ignition part 25 is provided on the outer periphery. In FIG. 3, the ignition unit 25 is provided at the left end of the combustion chamber 10 having a bore diameter of 80 mm. Further, the combustion chamber 10 is formed with a cylindrical hole portion 11 that opens into the combustion chamber at a position where the flame of the ignited air-fuel mixture propagates and closes at the opposite end. The cylinder hole 11 has a hole diameter (diameter) d of 1 mm and a depth L of 10 mm. The direction of the axis A of the cylindrical hole portion 11 is the radial direction of the combustion chamber 10. With this arrangement, the axis A of the cylindrical hole portion 11 intersects with the straight line B connecting the center 11b of the opening 11a and the ignition portion 25 and does not coincide with the straight line B.

  FIG. 4 is a diagram showing an experimental result by the combustion chamber structure shown in FIG. 3, and shows a flame propagation state for each time. As time passes, the process proceeds from FIG. 4 (A) to FIG. 4 (L).

  In FIG. 4A, when the air-fuel mixture in the combustion chamber is ignited by the ignition unit 25, the flame rapidly advances from the ignition point. Then, in FIG. 4 (F), when the traveling wave of the flame reaches the opening 11a of the cylindrical hole portion 11 and passes through the opening 11a of the cylindrical hole portion 11, the opening 11a of the cylindrical hole portion 11 is understood from FIG. 4 (G). Gas spouts out of. 4H, which is the next moment, it can be seen that the ejection of gas from the cylindrical hole portion 11 is much faster than the progression of the flame starting from the ignition portion 25. This gas promotes the diffusion of the unburned gas in the combustion chamber and increases the contact area of the unburned gas with the flame. Therefore, the combustion speed in the cylinder is increased, and the effect of increasing the thermal efficiency is obtained.

  FIG. 5 is a diagram illustrating a phenomenon in which a very high-speed gas is ejected from the cylindrical hole portion 11.

  The present inventors considered the reason why the gas ejection phenomenon occurs as follows. When the ignition unit 25 ignites in a state in which the air-fuel mixture exists in the combustion chamber, the flame proceeds as shown in FIG. The traveling wave of the flame is indicated by W1 to W6. When the flame reaches the opening 11a of the tube hole 11, the air-fuel mixture near the opening burns. The air-fuel mixture expands thermally when burned. Then, as shown in FIG. 5B, the pressure wave due to thermal expansion acts to push the air-fuel mixture (unburned gas) present in the tube hole portion 11 toward the bottom 11 c of the tube hole portion 11. Then, the gas pressure becomes very high at the bottom 11c of the cylindrical hole portion 11. Then, it is considered that a gas ejection phenomenon occurs when a very high-speed gas is ejected from the cylindrical hole portion 11 due to the rebound of the pressure wave.

  Although details are omitted, the present inventors also experimented even when the hole diameter d of the cylindrical hole portion 11 was changed. When the hole diameter d was 1 to 3 mm, the high-speed gas ejection phenomenon could be confirmed, but when the hole diameter d was 5 mm, the gas ejection phenomenon was weak. This is presumably because the pressure confinement phenomenon due to the air-fuel mixture burned in the vicinity of the opening was difficult to occur because the hole diameter d was too large. Further, when the hole diameter d is smaller than 1 mm, the flame hardly progresses into the cylindrical hole portion 11, and in this case, the gas ejection phenomenon is weak. Accordingly, the present inventors have found that it is necessary to set an appropriate hole diameter in order to obtain the gas ejection phenomenon.

  The inventors also experimented by changing the depth L of the tube hole 11. Then, when the ratio L / d of the depth L to the diameter d of the cylindrical hole portion 11 was larger than 6, the high-speed gas ejection phenomenon could be confirmed. On the other hand, when the ratio L / d was smaller than 6, the gas ejection phenomenon was weak. This is considered to be because when the depth L is small, the pressure confined in the cylindrical hole portion 11 is small. Therefore, the present inventors have found that an appropriate depth L is necessary to obtain the gas ejection phenomenon.

  Further, the inventors also experimented even when the position of the cylindrical hole portion 11 was changed. Then, at a position where the axis A of the cylinder hole 11 coincides with a straight line B connecting the center 11b of the opening 11a and the ignition part 21 of the ignition part 25, for example, at a position where the cylinder hole 11 faces the ignition part 25, the gas The eruption phenomenon was weakened. It is considered that the axial line A coincides with the straight line B because the traveling wave from the ignition part 25 and the jet gas from the cylindrical hole part 11 cancel each other out of energy. Therefore, the present inventors have found that it is necessary to place the cylindrical hole portion 11 in an appropriate position in order to obtain the high-speed gas ejection phenomenon.

  In the above description, the case where one outer periphery ignition part 25 and one cylinder hole part 11 are provided in the combustion chamber 10 has been described as an example. Therefore, in the present embodiment, as shown in FIG. 1, the four outer peripheral ignition portions 25 are provided on the outer periphery of the combustion chamber 10 and the four cylindrical hole portions 11 are provided. By doing so, high-speed gas is ejected from the four cylindrical hole portions 11. This gas promotes the diffusion action of the unburned gas in the combustion chamber and expands the contact area of the unburned gas with the flame. As a result, the combustion speed in the cylinder was increased and the thermal efficiency was increased.

  FIG. 6 is a diagram for explaining the operational effect of the arrangement of the ignition part 25 and the cylinder hole part 11 in the present embodiment. As described above, when the ignition unit 25 ignites, the flame proceeds. The traveling wave of the flame is indicated by W1 to W3. When the flame reaches the opening 11a of the tube hole 11, high-speed gas is ejected from the tube hole 11 for the reason described in FIG.

  At this time, if the tube hole portion 11 is formed in the middle of one ignition portion 25 and another ignition portion 25, the traveling wave W1 of the flame from each ignition portion 25 is simultaneously transmitted to the tube hole portion 11. It reaches the opening 11a. If the traveling waves W1 of both flames reach at the same time, it is considered that the thermal expansion of each flame in the opening 11a of the cylindrical hole portion 11 cancels each other and the pressure wave is weakened.

  In the present embodiment, as shown in FIG. 1, the cylinder interior 11 is not formed in the middle of one igniter 25 and the other igniter 25 but is biased to one igniter 25. . As a result, high-speed gas is ejected from the cylinder interior 11 by the flame propagation from the igniting portion 25 on the biasing side. Furthermore, since the direction of the axis A of the cylinder interior 11 is the radial direction of the combustion chamber 10, the gas ejected from the cylinder interior 11 is ejected toward the center of the combustion chamber 10. Further, in the combustion chamber 10, the center region of the piston crown surface has a slow flame propagation, and a large amount of unburned air-fuel mixture accumulates. High-speed gas ejected from the cylinder interior 11 is ejected toward the unburned region. Therefore, the combustion period in the cylinder can be shortened and the thermal efficiency can be increased.

(Second Embodiment)
FIG. 7 is a view showing a second embodiment of the combustion chamber structure of the engine according to the present invention.

  In 1st Embodiment, although the cylinder hole part 11 was formed in the side wall surface of the combustion chamber 10, you may form in another place. For example, it may be formed near the ceiling spark plug 30 of the cylinder head, that is, between the ceiling spark plug 30 and the intake valve 31 or the exhaust valve 32. If it is in the vicinity of the spark plug 30, the flame traveling wave passes through the cylindrical hole portion 11 early, so that high-speed gas is ejected early. As a result, diffusion in the combustion chamber occurs early, combustion is promoted, and thermal efficiency is increased. Further, it may be formed on the umbrella surface of the intake valve 31 or the exhaust valve 32. Furthermore, you may form in a piston crown surface. In any case, it may be formed at a position where the flame of the combustion chamber propagates. And the axial direction of the cylinder hole part 11 should just be formed in the direction which does not correspond with the propagation direction of a flame. By comprising in this way, high-speed gas will eject from the cylinder hole part 11, combustion in a cylinder can be accelerated | stimulated and thermal efficiency can be made high.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention. For example, the number of the cylindrical hole portions is not limited to the number exemplified above, and may be set as appropriate. As described with reference to FIGS. 3 to 5, even a single effect can be obtained sufficiently. Moreover, although the type which has four ignition parts as an annular spark plug was illustrated above, what is necessary is just to change the number of ignition parts suitably. Furthermore, in the above description, an annular spark plug having a plurality of ignition parts in one annular body is exemplified as the spark plug, but a plurality of ordinary spark plugs such as a ceiling spark plug may be used. Any one having an ignition function may be used. Furthermore, in the above description, an engine having a ceiling spark plug has been described as an example, but a diesel engine may be used.

It is a figure which shows 1st Embodiment of the combustion chamber structure of the engine by this invention. It is a perspective view which shows an annular spark plug. It is a figure which shows a basic combustion chamber structure. It is a figure which shows the experimental result by the combustion chamber structure shown in FIG. It is a figure explaining the phenomenon in which a very high-speed gas ejects from a cylinder hole part. It is a figure explaining the effect of 1st Embodiment of the combustion chamber structure of the engine by this invention. It is a figure which shows 2nd Embodiment of the combustion chamber structure of the engine by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Combustion chamber 11 Cylinder hole part 11a Opening 11b Center 11c Bottom 20 Annular spark plug 25 Ignition part 25a-25d Discharge gap (ignition part)
30 Ceiling spark plug

Claims (8)

A plurality of ignition parts provided on the same diameter as the combustion chamber in the combustion chamber;
Provided in the vicinity of the ignition unit,
An opening formed at the position where the flame of the ignited mixture propagates,
A bottom closing the opposite end of the opening;
A cylindrical hole including
An engine combustion chamber structure comprising: The ignition part is an ignition part of an annular spark plug including an insulating annular body having an inner diameter that is the same as that of the combustion chamber and is annularly formed along the combustion chamber wall surface. Provided on the face,
The combustion chamber structure for an engine according to claim 1. The axis of the cylindrical hole part intersects the traveling direction of the flame propagating from the ignition part.
The combustion chamber structure of the engine according to claim 1 or 2, wherein The axis of the cylindrical hole intersects with a straight line connecting the opening center and the ignition part of the ignition part.
The combustion chamber structure of the engine according to claim 1 or 2, wherein The opening diameter of the cylindrical hole is 1 mm or more and 3 mm or less.
The engine combustion chamber structure according to any one of claims 1 to 4, wherein the engine combustion chamber structure is provided. The cylindrical hole portion has a depth ratio to a diameter larger than 6.
The engine combustion chamber structure according to any one of claims 1 to 5, wherein the engine combustion chamber structure is provided. The tube hole is biased and arranged in any one of the ignition parts adjacent to both sides.
The engine combustion chamber structure according to any one of claims 1 to 6, wherein the engine combustion chamber structure is provided. The cylindrical hole portion is arranged so that the gas ejected from the opening reaches the unburned region before the traveling direction of the flame surface propagating from the ignition portion.
The engine combustion chamber structure according to any one of claims 1 to 7, wherein the structure is a combustion chamber structure of the engine.