JP2009270542A - Engine and spark plug for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine and a spark plug for the engine capable of making flame propagate in a combustion chamber as uniformly as possible and of burning air-fuel mixture in the combustion chamber as uniformly as possible. <P>SOLUTION: The spark plug 10 with an ignition chamber 14 formed in a plug cover 13 covering the ignition point 11 is installed on a cylinder head 6. A plurality of nozzle holes 15 providing communication between the ignition chamber 14 and the combustion chamber 3 facing a piston 2 are provided on the plug cover 13. The spark plug 10 is disposed in such a manner that the plug cover 13 is projected out to the combustion chamber 3 from a cylinder head 6 side in an axial direction of the combustion chamber 3. The plurality of nozzle holes 15 are composed to maintain an area ratio of total area of the plurality of nozzle holes 15 to the area of the projection surface 13a in a range from 0.05 to 0.2 under a dispersed condition keeping intervals on a projection surface 13a so as to form flame of a shape corresponding to an outer shape of a projection surface 13a of the plug cover 13 projecting to a combustion chamber 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  According to the present invention, an ignition plug having an ignition chamber formed in a plug cover covering an ignition point is mounted on a cylinder head, and a plurality of injection holes communicating the ignition chamber and a combustion chamber facing a piston are formed in the plug cover. The present invention relates to an engine provided and an engine spark plug mounted on a cylinder head of the engine.

  In the engine as described above, an air-fuel mixture such as a lean air-fuel mixture sucked into the combustion chamber is compressed by ascending the piston, and the compressed air-fuel mixture flows into the ignition chamber through the nozzle holes. The air-fuel mixture flowing into the ignition chamber is ignited by a spark plug and burned, and a flame formed by the combustion is ejected into the combustion chamber through the nozzle hole. As described above, in the conventional engine, the air-fuel mixture sucked into the combustion chamber is obtained by performing the inflow of the air-fuel mixture from the combustion chamber to the ignition chamber and the ejection of flame from the ignition chamber to the combustion chamber through the plurality of nozzle holes. It is made to burn (for example, refer patent documents 1 and 2). In the engines described in Patent Documents 1 and 2, each of the plurality of nozzle holes is configured to eject a separate flame jet into the combustion chamber.

JP 2007-40174 A JP 2007-77902 A

  In the engines described in Patent Documents 1 and 2, since a flame jet is separately ejected from each of the plurality of nozzle holes to the combustion chamber, in the combustion chamber, the region facing the nozzle holes is easy to reach the flame, Flames are difficult to reach in the areas facing each other between the nozzle holes, and there are areas where the flames are easily reachable and areas where the flames are difficult to reach in the combustion chamber. As a result, the propagation of the flame proceeds in the region where the flame easily reaches compared to the region where the flame does not easily reach, and it becomes difficult to uniformly burn the air-fuel mixture in the combustion chamber.

  The present invention has been made paying attention to such a point, and an object of the present invention is to make an engine capable of propagating a flame as uniformly as possible to a combustion chamber and combusting an air-fuel mixture in the combustion chamber as uniformly as possible. It is in providing a spark plug for an engine.

In order to achieve this object, the engine according to the present invention is characterized in that an ignition plug having an ignition chamber formed in a plug cover covering an ignition point is attached to a cylinder head, and the combustion facing the ignition chamber and the piston is performed. An engine provided with a plurality of nozzle holes communicating with the chamber in the plug cover;
The spark plug is disposed so as to project the plug cover from the cylinder head side to the combustion chamber in the axial direction of the combustion chamber, and the plurality of injection holes project the plug cover into the combustion chamber. The area ratio of the total area of the plurality of nozzle holes to the area of the projecting surface in a dispersed state spaced apart from each other on the projecting surface is formed to form a flame corresponding to the outer shape of the projecting surface. It exists in the point comprised so that it may become 05-0.2.

  According to this characteristic configuration, since the plurality of injection holes are provided in a dispersed state spaced apart from each other on the protruding surface of the plug cover protruding into the combustion chamber, a flame is injected from each injection hole. At this time, if the area ratio of the total area of the plurality of injection holes to the area of the protruding surface becomes too large, there is a possibility that a problem may occur in the durability of the plug cover. Therefore, it is conceivable to reduce the area ratio of the total area of the plurality of nozzle holes to the area of the protruding surface. However, as the area ratio decreases, each of the flames ejected from each nozzle hole is ejected independently. For example, each flame jet is ejected from each nozzle hole. Therefore, in this characteristic configuration, the area ratio of the total area of the plurality of nozzle holes to the area of the protruding surface is set to 0.05 to 0.2, so that the flames jetted from the respective nozzle holes are mixed together. Thus, a flame having a shape corresponding to the outer shape of the protruding surface of the plug cover can be formed. Thereby, a flame can be propagated corresponding to the external shape of the protruding surface of the plug cover in the combustion chamber. Therefore, it has become possible to realize an engine that can propagate the flame as uniformly as possible to the combustion chamber and burn the air-fuel mixture in the combustion chamber as uniformly as possible.

  According to a further characteristic configuration of the engine according to the present invention, the plurality of nozzle holes are equally spaced on a circumference centered on the center of the protruding surface in a cross-sectional view orthogonal to the central axis of the combustion chamber. It is in the point provided in.

  According to this characteristic configuration, in the cross-sectional view orthogonal to the central axis of the combustion chamber, the plurality of nozzle holes are provided at equal intervals on the circumference centered on the center of the protruding surface. It can suppress that a hole approaches or leaves too much. Thereby, a some nozzle hole can be arrange | positioned in an appropriate position, and the flame of the shape corresponding to the external shape of the protrusion surface of a plug cover can be formed exactly.

  According to a further characteristic configuration of the engine according to the present invention, the plurality of nozzle holes are respectively arranged on a plurality of circumferences having different radii around the center of the protruding surface in a cross-sectional view orthogonal to the central axis of the combustion chamber. It is in the point provided so that it may become at equal intervals.

  According to this characteristic configuration, the plurality of nozzle holes are provided at equal intervals on a plurality of circumferences having different radii around the center of the protruding surface in a cross-sectional view orthogonal to the central axis of the combustion chamber. Therefore, it can suppress that adjacent nozzle holes approach or separate too much. Thereby, a some nozzle hole can be arrange | positioned in an appropriate position, and the flame of the shape corresponding to the external shape of the protrusion surface of a plug cover can be formed exactly.

  A further characteristic configuration of the engine according to the present invention is that the plurality of circumferences are determined so as to be spaced apart in a radial direction.

  According to this characteristic configuration, in the cross-sectional view orthogonal to the central axis of the combustion chamber, the plurality of nozzle holes are respectively arranged on a plurality of circumferences having different radii with a constant interval in the radial direction around the center of the protruding surface. Since it provides so that it may become equal intervals, it can suppress reliably that adjacent nozzle holes approach too much or leave too much. Therefore, a flame having a shape corresponding to the outer shape of the protruding surface of the plug cover can be formed more accurately.

A characteristic configuration of an engine ignition plug according to the present invention includes a plug body having an ignition point, and a plug cover provided on the plug body so as to cover the ignition point. An engine ignition plug in which a plurality of injection holes communicating with a combustion chamber facing a piston and an ignition chamber formed in the plug cover are formed in the plug cover in a state where the plug cover is mounted. And
In the axial direction of the combustion chamber, in the state where the plug cover protrudes from the cylinder head side to the combustion chamber, the plurality of nozzle holes are external shapes of the protruding surfaces of the plug cover protruding into the combustion chamber The area ratio of the total area of the plurality of nozzle holes to the area of the projecting surface is 0.05 to 0.2 in a dispersed state spaced from each other on the projecting surface so as to form a flame having a shape corresponding to It is in the point comprised so that.

  According to this characteristic configuration, as described in the above-mentioned characteristic configuration of the engine according to the present invention, the projecting surface of the plug cover is made to be ejected in a state where flames ejected from each of the plurality of nozzle holes are mixed. It is possible to form a flame having a shape corresponding to the outer shape. As a result, an ignition plug for an engine that can propagate the flame as uniformly as possible to the combustion chamber and burn the mixture in the combustion chamber as uniformly as possible can be realized.

  The engine ignition plug according to the present invention is further characterized in that the plug cover is formed integrally with the plug body.

  According to this characteristic configuration, the ignition plug can be formed by predetermining the respective positions of the ignition chamber, the ignition point, and the nozzle hole and integrally forming the plug cover on the plug body. Thus, the ignition chamber, the ignition point, and the nozzle hole can be arranged at appropriate positions simply by mounting the ignition plug on the cylinder head. Therefore, it is possible to easily attach the spark plug to the engine.

[Overall engine configuration]
As shown in FIG. 1, the engine 1 includes a piston 2, a cylinder 4 that houses the piston 2 and forms a combustion chamber 3 together with the top surface 2 a of the piston 2, and a spark plug 10 (this Corresponding to the engine spark plug according to the invention. The piston 2 is reciprocated in the cylinder 4, and the intake valve 5 and the exhaust valve (not shown) are opened and closed so that each of the intake stroke, the compression stroke, the combustion / expansion stroke, and the exhaust stroke is performed in the combustion chamber 3. The process is performed sequentially. Thereby, although illustration is abbreviate | omitted, it is comprised so that the reciprocating motion of piston 2 may be output as a rotational motion of a crankshaft by a connecting rod. Such a configuration is the same as that of a normal four-stroke internal combustion engine.

  The engine 1 uses city gas (13A), which is a gaseous fuel, as fuel. In the intake stroke, the intake valve 5 is opened, and an air-fuel mixture (for example, air) is introduced from the intake port 8 into the combustion chamber 3 (for example, , A lean mixture) M. In the compression stroke and the combustion / expansion stroke, the air-fuel mixture M sucked into the combustion chamber 3 is compressed to burn and expand the fuel. In the exhaust stroke, the exhaust valve is opened, and exhaust gas is discharged from the combustion chamber 3 to an exhaust port outside the figure.

  A recess 7 is formed on the top surface 2 a of the piston 2 facing the cylinder head 6. As a result, the combustion chamber 3 is constituted by a space formed by the recess 7 in addition to the space between the top surface 2 a of the piston 2 and the inner surface of the cylinder 4. By forming the combustion chamber 3 in this way, when the piston 2 rises in the compression stroke, a vortex flow from the periphery of the recess 7 toward the center of the recess 7, that is, a so-called squish is generated.

  The intake port 8 provided in the cylinder head 6 is provided with a fuel supply unit 9 that injects the fuel G with respect to the air A that is taken in. The air-fuel mixture M of the air A and fuel G (for example, a lean air-fuel mixture) ). By opening the intake valve 5, an air-fuel mixture M of air A and fuel G (for example, a lean air-fuel mixture) is sucked into the combustion chamber 3. Here, the fuel ejection amount from the fuel supply unit 9 can be changed, and the mixing ratio of the air A and the fuel G can be changed according to the operating state of the engine 1.

The spark plug 10 attached to the cylinder head 6 is provided so that its central axis is coaxial with the central axis W of the combustion chamber 3. The spark plug 10 is composed of a plug body 12 having an ignition point 11 at the tip, and a plug cover 13 provided so as to cover the ignition point 11. The spark plug 10 is mounted so that the plug cover 13 is inserted into the recess 7 formed in the piston 2 at the ignition timing (for example, the position of the piston 2 is just before the top dead center). The plug cover 13 is formed in a bottomed cylindrical shape having a bottom portion 13 a at the tip end side, and is formed integrally with the plug body 12. Incidentally, the bottom portion 13a of the plug cover 13 is formed in an arc shape in the orthogonal direction. An ignition chamber 14 having an ignition point 11 is formed in the plug cover 13. The spark plug 10 is configured so that the ignition point 11 is positioned closer to the combustion chamber 3 than the lower end portion 6a of the cylinder head 6 in the axial direction of the combustion chamber 3 (vertical direction in FIG. 1).
Here, the axial direction of the combustion chamber 3 is a direction along the central axis W of the combustion chamber 3, and is, for example, the same direction as the vertical movement direction of the piston 2. Hereinafter, the axial direction of the combustion chamber 3 is referred to as “axial direction”, and the direction orthogonal to the axial direction of the combustion chamber 3 is referred to as “orthogonal direction”.

  The plug cover 13 is formed with a plurality of injection holes 15 that allow the combustion chamber 3 and the ignition chamber 14 to communicate with each other. The spark plug 10 sparks and burns the air-fuel mixture M flowing into the ignition chamber 14 from the combustion chamber 3 through the nozzle hole 15, and causes the flame formed by the combustion to be jetted into the combustion chamber 3 through the nozzle hole 15. It is configured. In this way, the inflow of the air-fuel mixture M from the combustion chamber 3 to the ignition chamber 14 and the injection of flame from the ignition chamber 14 to the combustion chamber 3 are performed by the plurality of nozzle holes 15, so that the air is sucked into the combustion chamber 3. The air-fuel mixture M is burned. As a result, the air-fuel mixture M flowing into the ignition chamber 14 is all the air-fuel mixture M flowing from the combustion chamber 3 through the nozzle hole 15, and fuel or air-fuel mixture is supplied to the ignition chamber 14 from other than the combustion chamber 3. It will never be done.

[Engine operation]
The engine 1 performs an intake stroke in which the air-fuel mixture M is taken into the combustion chamber 3 by the piston 2 descending from the top dead center while the intake valve 5 is opened. Next, the piston 2 ascends while the intake valve 5 is closed, whereby a compression stroke for compressing the air-fuel mixture M in the combustion chamber 3 is performed. In this compression stroke, the volume of the combustion chamber 3 is reduced by the piston 2 rising, so that the air-fuel mixture M in the combustion chamber 3 flows into the ignition chamber 14 through the injection holes 15.
The engine 1 operates the spark plug 10 at the ignition timing (for example, immediately before top dead center), sparks the ignition point 11 to ignite the mixture M in the ignition chamber 14. Then, combustion in the ignition chamber 14 proceeds, and a flame is ejected to the combustion chamber 3 through the nozzle hole 15. Thereby, the air-fuel mixture M in the combustion chamber 3 is combusted and the combustion / expansion stroke is performed. Next, when the piston 2 moves up with the exhaust valve opened, an exhaust stroke is performed in which the exhaust gas in the combustion chamber 3 is exhausted to the exhaust port.
Thus, the engine 1 is configured to repeatedly perform a series of operations for performing each stroke in the order of the intake stroke, the compression stroke, the combustion / expansion stroke, and the exhaust stroke.

[Composition of nozzle hole]
Based on FIG. 2, the structure of the injection hole 15 provided in the plug cover 13 will be described.
A plurality of nozzle holes 15 are provided in a dispersed state spaced from each other on the protruding surface 13 a of the plug cover 13 protruding into the combustion chamber 3. The protruding surface 13 a of the plug cover 13 is formed in an arc shape in a cross-sectional view orthogonal to the central axis W of the combustion chamber 3. The area ratio (S2 / S1) of the total area S2 of the plurality of nozzle holes 15 to the surface area S1 of the protruding surface 13a of the plug cover 13 is configured to be 0.05 to 0.2.

If the area ratio (S2 / S1) of the total area S2 of the plurality of nozzle holes 15 to the surface area S1 of the protruding surface 13a of the plug cover 13 becomes too large, there is a possibility that a problem may occur in the durability of the plug cover 13. Therefore, it is conceivable to reduce the area ratio (S2 / S1). However, as the area ratio decreases, each of the flames ejected from each nozzle hole 15 tends to be ejected independently. Each flame jet is ejected from each nozzle hole 15. Therefore, in the present invention, the area ratio (S2 / S1) is set to 0.05 to 0.2.
Hereinafter, the surface area S1 of the protruding surface 13a of the plug cover 13 is set to the same surface area, and the hole diameter of the injection hole 15 is also set to the same hole diameter, so that the area ratio (S2 / S1) is changed from 0.05 to 0.00. 2 (FIG. 3 (a)) and the area ratio (S2 / S1) smaller than the range of 0.05 to 0.2 (FIG. 3 (b)). The formation state of the flame in the chamber 3 will be described.

FIG. 3A shows, for example, a cross-sectional view orthogonal to the central axis W of the combustion chamber 3 when the area ratio (S2 / S1) is 0.08 in the range of 0.05 to 0.2. The result of having experimented how the flame formation state is in the combustion chamber 3 is shown. At this time, one nozzle hole 15 is arranged at the center of the protruding surface 13a of the plug cover 13 in the cross-sectional view orthogonal to the central axis W of the combustion chamber 3, and the center of the protruding surface 13a of the plug cover 13 is the center. A total of nine nozzle holes 15 are provided by arranging four at a predetermined interval in the circumferential direction on two circumferences having different radii. Two circumferences having different radii are provided at regular intervals in the radial direction.
In this case, the flame (white portion in the figure) has a substantially circular shape that spreads uniformly in the circumferential direction around the center of the protruding surface 13 a of the plug cover 13. Thereby, a flame can be propagated uniformly with respect to the combustion chamber 3, and the air-fuel mixture in the combustion chamber 3 can be burned as uniformly as possible.

On the other hand, FIG. 3B shows, for example, orthogonal to the central axis W of the combustion chamber 3 when the area ratio (S2 / S1) is 0.044, which is smaller than the range of 0.05 to 0.2. The cross-sectional view which shows the result of having experimented what the flame formation state is in the combustion chamber 3 is shown. At this time, one nozzle hole 15 is arranged at the center of the protruding surface 13a of the plug cover 13 in the cross-sectional view orthogonal to the central axis W of the combustion chamber 3, and the center of the protruding surface 13a of the plug cover 13 is the center. A total of five nozzle holes 15 are provided by arranging four at regular intervals in the circumferential direction on the circumference. The radius of the circumference in which the four injection holes 15 are arranged is ½ of the radius of the protruding surface 13 a of the plug cover 13 in a cross-sectional view orthogonal to the central axis W of the combustion chamber 3.
In this case, a portion where a flame is formed (white portion in the figure) and a portion where no flame is formed (black portion in the figure) are centered on the center of the protruding surface 13a of the plug cover 13 in the circumferential direction. The shape is intermittent. Therefore, the flame cannot be propagated uniformly to the combustion chamber 3.

  As shown in FIG. 2B, the plurality of nozzle holes 15 are a plurality of circles having different radii around the center of the protruding surface 13 a of the plug cover 13 in a cross-sectional view orthogonal to the central axis W of the combustion chamber 3. Each of the circumferences Q1 to Q3 is provided with a constant interval D. The plurality of circumferences Q1 to Q3 are provided at regular intervals R in the radial direction. That is, from the inside in the radial direction, the radius of the first circumference Q1 is R, the radius of the second circumference Q2 is 2R, and the radius of the third circumference Q3 is 3R. Thus, by determining the arrangement positions of the plurality of nozzle holes 15, it is possible to suppress the adjacent nozzle holes 15 from being too close or too far apart. Thereby, the several injection hole 15 can be arrange | positioned in an appropriate position, and the flame of the shape corresponding to the external shape of the protrusion surface 13a of the plug cover 13 can be formed exactly.

  Further, each of the nozzle holes 15 located on each of the circumferences Q1 to Q3 is mutually in a rotational direction centered on the center of the protruding surface 13 of the plug cover 13 in a cross-sectional view orthogonal to the central axis W of the combustion chamber 3. It is provided to be at different positions. Thereby, a flame can be ejected in a state of being dispersed from each nozzle hole 15 in the rotation direction, and a flame having a shape corresponding to the outer shape of the protruding surface 13a of the plug cover 13 can be accurately formed.

  Incidentally, in the plurality of injection holes 15, the hole diameter, the inflow direction in which the air-fuel mixture M flows into the ignition chamber 14, and the injection direction in which a flame is injected into the combustion chamber 3 can be appropriately changed. For example, the hole diameter may be different for each of the plurality of circumferences Q1 to Q3. Further, the inflow direction can be configured such that the inflow direction faces the ignition point 11 in each of the plurality of nozzle holes 15.

[Another embodiment]
(1) In the above-described embodiment, it is sufficient that a flame having a shape corresponding to the outer shape of the protruding surface 13 a of the plug cover 13 is formed by the flame ejected from the plurality of nozzle holes 15. The position and number of arrangements can be changed as appropriate.

(2) In the above embodiment, the case where the outer shape of the projecting surface 13a of the plug cover 13 is formed in an arc shape in the axial direction has been described. For example, the outer shape of the projecting surface 13a of the plug cover 13 is changed to the combustion chamber. It can also be formed in a U-shape with the 3 side as the bottom, and the shape of the outer shape of the protruding surface 13a of the plug cover 13 can be appropriately changed. In this case, it is preferable that the flame be uniformly propagated over the entire combustion chamber 3.

  According to the present invention, an ignition plug having an ignition chamber formed in a plug cover covering an ignition point is mounted on a cylinder head, and a plurality of injection holes communicating the ignition chamber and a combustion chamber facing a piston are formed in the plug cover. It is provided, and can be applied to various engines and engine spark plugs that can propagate a flame as uniformly as possible to the combustion chamber and burn the air-fuel mixture in the combustion chamber as uniformly as possible.

Sectional view along the central axis of the engine combustion chamber The figure in the direction along the central axis of the combustion chamber and the figure in the direction orthogonal to the central axis of the combustion chamber with respect to the main part of the spark plug Experimental results showing the state of flame formation

Explanation of symbols

2 Piston 3 Combustion chamber 6 Cylinder head 7 Concave portion 10 Spark plug (engine spark plug)
11 Ignition point 13 Plug cover 14 Ignition chamber 15 Injection hole

Claims (6)

A spark plug in which an ignition chamber is formed in a plug cover that covers the ignition point is mounted on the cylinder head, and a plurality of nozzle holes that communicate the ignition chamber and the combustion chamber facing the piston are provided in the plug cover. An engine,
The spark plug is arranged so that the plug cover protrudes from the cylinder head side to the combustion chamber in the axial direction of the combustion chamber,
The plurality of nozzle holes are arranged in a distributed state spaced apart from each other on the projecting surface so as to form a flame having a shape corresponding to the outer shape of the projecting surface of the plug cover projecting into the combustion chamber. An engine configured such that an area ratio of a total area of the plurality of nozzle holes to an area is 0.05 to 0.2.   2. The engine according to claim 1, wherein the plurality of nozzle holes are provided at equal intervals on a circumference centered on a center of the protruding surface in a cross-sectional view orthogonal to a central axis of the combustion chamber. .   The plurality of nozzle holes are provided at equal intervals on a plurality of circumferences having different radii around the center of the projecting surface in a cross-sectional view orthogonal to the central axis of the combustion chamber. Item 3. The engine according to Item 1 or 2.   The engine according to claim 3, wherein the plurality of circumferences are determined so as to be spaced apart in a radial direction. A plug body having an ignition point; and a plug cover provided on the plug body so as to cover the ignition point;
When the plug body and the plug cover are mounted on the cylinder head of the engine, a plurality of injection holes are formed in the plug cover for communicating the combustion chamber facing the piston and the ignition chamber formed in the plug cover. A spark plug for an engine,
In a state where the plug cover protrudes from the cylinder head side to the combustion chamber in the axial direction of the combustion chamber,
The plurality of nozzle holes are formed on the projecting surface in a dispersed state spaced apart from each other so as to form a flame having a shape corresponding to the outer shape of the projecting surface of the plug cover projecting into the combustion chamber. An engine ignition plug configured such that an area ratio of a total area of the plurality of nozzle holes to an area is 0.05 to 0.2.   The engine spark plug according to claim 5, wherein the plug cover is formed integrally with the plug body.