JP5319823B2 - Engine and spark plug for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To blow off flames uniformly into a combustion chamber while an air/fuel mixture in the combustion chamber can be sufficiently supplied to an ignition point, while enabling stable spark ignition of the air/fuel mixture. <P>SOLUTION: An ignition plug 10 is disposed in the axial direction of the combustion chamber so that a plug cover 13 may project from a cylinder head side into the combustion chamber 3. A plurality of communication holes 15 comprise a leading-end-side communication hole 16 provided on the leading end side of the plug cover 13 projecting into the combustion chamber 3 in the axial direction, and a base-end-side communication hole 17 provided closer to the base end side of the plug cover 13 than the leading-end-side communication hole 16. The base-end-side communication hole 17 is configured so that resistance to a fluid flowing from the combustion chamber 3 to an ignition chamber 14 may be smaller than that of the fluid flowing from the ignition chamber 14 to the combustion chamber 3. The air/fuel mixture M flowing to the ignition chamber 14 from the combustion chamber 3 flows obliquely upward in the base-end-side communication hole 17. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  In the present invention, an ignition plug having an ignition chamber formed in a plug cover that covers an ignition point is mounted on a cylinder head, and a plurality of communication holes that connect 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 as the piston rises, and the compressed air-fuel mixture flows into the ignition chamber through the communication hole. 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 to the combustion chamber through the communication hole. As described above, in the conventional engine, the lean 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 the flame from the ignition chamber to the combustion chamber through the plurality of communication holes. Etc. (see, for example, Patent Documents 1 and 2).

In the engines described in Patent Documents 1 and 2, 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. It is formed in the bottomed cylinder shape used as a bottom part. The plurality of communication holes are provided at the tip of the plug cover protruding into the combustion chamber.
In the engine described in Patent Document 2, the communication hole arranged on the intake port side among the plurality of communication holes has a cross-sectional area near the combustion chamber larger than a cross-sectional area near the ignition chamber. In contrast, the communication hole arranged on the exhaust port side is configured such that the cross-sectional area near the combustion chamber is smaller than the cross-sectional area near the ignition chamber.

JP 2007-77902 A JP 2006-177248 A

  In the engines described in Patent Documents 1 and 2, since a plurality of communication holes are provided at the tip of the plug cover that is the bottom of the ignition chamber, ignition in the communication hole that is the inflow point of the air-fuel mixture into the ignition chamber The chamber side end is located away from the ignition point in the axial direction of the combustion chamber. In order to supply a sufficient air-fuel mixture into the ignition chamber, it is necessary to increase the volume of the ignition chamber to some extent. Therefore, the distance from the ignition chamber side end portion to the ignition point in the communication hole is increased. Therefore, there is a problem that the air-fuel mixture in the combustion chamber cannot be sufficiently supplied to the ignition point, and burnt gas remains at the ignition point, making it difficult to stably perform spark ignition of the air-fuel mixture.

  In the engine described in Patent Document 2, the communication hole disposed on the intake port side is configured so that the cross-sectional area of the portion close to the combustion chamber is larger than the cross-sectional area of the portion close to the ignition chamber, and is disposed on the exhaust port side. The cross-sectional area of the portion close to the combustion chamber is smaller than the cross-sectional area of the portion close to the ignition chamber, and the air-fuel mixture in the combustion chamber is ignited by the communication hole arranged on the intake port side. In addition to facilitating the flow into the chamber, the communication holes arranged on the exhaust port side facilitate the discharge of the burned gas from the ignition chamber into the combustion chamber. Thereby, in the thing of patent document 2, compared with the thing of patent document 1, it becomes easy to supply the air-fuel | gaseous mixture of a combustion chamber with respect to an ignition point, and burned gas will remain in an ignition point. It is conceivable that this can be suppressed. However, in Patent Document 2, when the flame is ejected from the ignition chamber to the combustion chamber, the flame is hardly ejected from the communication hole disposed on the intake port side, and the communication disposed mainly on the exhaust port side. There is a risk that a flame may be ejected from the hole. As a result, the ejection of the flame to the combustion chamber becomes uneven, causing a problem that the spray state of the flame to the combustion chamber cannot be made uniform.

  The present invention has been made paying attention to such a point, and its purpose is to sufficiently supply the air-fuel mixture in the combustion chamber with respect to the ignition point and stably perform spark ignition of the air-fuel mixture. Another object of the present invention is to provide an engine and an ignition plug for the engine that can uniformly emit a flame to the combustion chamber.

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. In the engine provided with a plurality of communication holes communicating with the chamber in the plug cover,
The spark plug is disposed so that the plug cover protrudes from the cylinder head side to the combustion chamber in the axial direction of the combustion chamber, and the plurality of communication holes are formed in the combustion chamber in the axial direction. A proximal end side communication hole provided on the distal end side of the plug cover protruding to the proximal end side, and a proximal end side communication hole provided closer to the proximal end side of the plug cover than the distal end side communication hole. The side communication hole is configured such that a resistance to a fluid flow from the combustion chamber side to the ignition chamber side is smaller than a resistance to a fluid flow from the ignition chamber side to the combustion chamber side, and the base end In the side communication hole, the inflow direction of the air-fuel mixture from the combustion chamber to the ignition chamber faces diagonally upward, and the base end side communication hole has a diameter of the combustion chamber side end portion of the ignition chamber side end portion. Configured to be larger than the hole diameter In addition, the diameter of the ignition chamber side end portion of the base end side communication hole is configured to be smaller than the diameter of the ignition chamber side end portion of the tip end side communication hole, and the combustion chamber side of the base end side communication hole The hole diameter of the end portion is configured to be larger than the hole diameter of the end portion on the combustion chamber side in the front end side communication hole .

  According to this characteristic configuration, the plurality of communication holes are configured by the base end side communication holes in addition to the front end side communication holes, so that the base end side communication holes are connected from the base end side communication holes to the ignition point. A distance can be shortened and it becomes easy to supply the air-fuel mixture in the combustion chamber to the ignition point. Further, since the air-fuel mixture in the combustion chamber flows into the ignition chamber not only from the base end side communication hole but also from the front end side communication hole, a sufficient amount of air-fuel mixture can flow into the ignition chamber. Therefore, by allowing the air-fuel mixture to flow into the ignition chamber from both the front end side communication hole and the base end side communication hole, the air-fuel mixture in the combustion chamber can be sufficiently supplied to the ignition point. In addition, since the resistance to the fluid flow from the combustion chamber side to the ignition chamber side is smaller than the resistance to the fluid flow from the ignition chamber side to the combustion chamber side, the base end side communication hole allows fluid to flow from the combustion chamber to the ignition chamber. Tends to flow in, and conversely, it becomes difficult to discharge the fluid from the ignition chamber to the combustion chamber. Thereby, the inflow of the air-fuel mixture from the combustion chamber to the ignition chamber can be performed by both the front end side communication hole and the base end side communication hole, and the jet of flame from the ignition chamber to the combustion chamber is mainly performed at the front end side. This can be performed by the communication hole, and the flame can be uniformly ejected to the combustion chamber. As a result, the spark spray state of the air-fuel mixture can be stably performed, and the spray state of the flame to the combustion chamber can be made uniform and desired.

Further , in the base end side communication hole, since the hole diameter at the end portion on the combustion chamber side is larger than the hole diameter at the end portion on the ignition chamber side, the fluid easily flows from the combustion chamber to the ignition chamber, and conversely, from the ignition chamber to the combustion chamber. It becomes difficult to discharge the fluid. Therefore, by simply adjusting the hole diameter at the end of the combustion chamber and the hole diameter at the end of the ignition chamber, the air-fuel mixture flows from the combustion chamber into the ignition chamber. Both of the holes can be used, and the ejection of flame from the ignition chamber to the combustion chamber can be performed mainly by the front end side communication hole.

Further , since the hole diameter of the ignition chamber side end portion in the base end side communication hole is smaller than the hole diameter of the ignition chamber side end portion in the tip end side communication hole, when the flame is ejected from the ignition chamber to the combustion chamber, A flame is more easily ejected from the front end side communication hole than the communication hole. Therefore, the flame is almost not ejected from the ignition chamber to the combustion chamber through the proximal end side communication hole, but can be performed through the distal end side communication hole, and the flame can be ejected uniformly and accurately to the combustion chamber. it can.

  A further characteristic configuration of the engine according to the present invention is that the base end side communication hole is configured in a tapered shape whose hole diameter is maximum at the combustion chamber side end and minimum at the ignition chamber side end. .

  According to this feature configuration, since the hole diameter of the base end side communication hole is the maximum at the combustion chamber side end and the minimum at the ignition chamber side end, the shape of the base end communication hole is simplified. However, in comparison with the case where the combustion chamber side end portion and the ignition chamber side end portion are cylindrical with the same diameter, the flow of the air-fuel mixture from the combustion chamber to the ignition chamber is facilitated. Therefore, the flow of the burned gas remaining in the ignition chamber can be promoted and actively discharged from the ignition chamber, and the spark ignition of the air-fuel mixture can be stabilized more accurately.

According to a further characteristic configuration of the engine according to the present invention, the ignition point is disposed closer to the cylinder head than the lower end of the cylinder head in the axial direction of the combustion chamber, and the proximal communication hole is The ignition chamber side end is provided so as to be closer to the base end side of the plug cover than the center position from the lower end portion of the cylinder head to the tip end portion of the plug cover in the axial direction.

  According to this characteristic configuration, the ignition chamber side end portion in the base end side communication hole is closer to the base end side of the plug cover than the center position from the lower end portion of the cylinder head to the tip end portion of the plug cover in the axial direction. The ignition chamber side end portion of the base end side communication hole can be positioned closer to the ignition point. Therefore, the air-fuel mixture in the combustion chamber can be accurately supplied to the ignition point, and the air-fuel mixture in the combustion chamber can be reliably supplied to the ignition chamber.

  According to a further characteristic configuration of the engine according to the present invention, the base end side communication hole has an ignition chamber side end portion provided closer to the base end side of the plug cover than the ignition point in the axial direction. It is in.

  According to this characteristic configuration, since the end portion of the ignition chamber side in the base end side communication hole is closer to the base end side of the plug cover than the ignition point in the axial direction, the base end side communication hole in the axial direction of the combustion chamber An ignition point can be located between the ignition chamber side end portion of the spark plug and the ignition chamber side end portion of the front end side communication hole. Therefore, the air-fuel mixture in the combustion chamber can be supplied from both the one side and the other side in the axial direction of the combustion chamber with respect to the ignition point, and sufficient supply of the air-fuel mixture in the combustion chamber to the ignition point is ensured. Yes.

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 communication holes are formed in the plug cover for connecting the combustion chamber facing the piston and the ignition chamber formed in the plug cover when the plug cover is mounted. And
The plurality of communication holes project into the combustion chamber in the axial direction in a state where the plug cover projects from the cylinder head side into the combustion chamber in the axial direction of the combustion chamber. A distal end side communication hole provided on the distal end side of the plug cover, and a proximal end side communication hole provided closer to the proximal end side of the plug cover than the distal end side communication hole, and the proximal end side communication hole The hole is configured such that a resistance to a fluid flow from the combustion chamber side to the ignition chamber side is smaller than a resistance to a fluid flow from the ignition chamber side to the combustion chamber side. In the hole, the inflow direction of the air-fuel mixture from the combustion chamber to the ignition chamber faces obliquely upward, and the base end side communication hole has a hole diameter at the end portion on the combustion chamber side of the ignition chamber side. Configured to be larger than The diameter of the ignition chamber side end of the base end side communication hole is configured to be smaller than the diameter of the ignition chamber side end of the tip end communication hole, and the combustion chamber side end of the base side communication hole This hole diameter is configured to be larger than the hole diameter at the end portion on the combustion chamber side in the front end side communication hole .

  According to this characteristic configuration, as described in the characteristic configuration of the engine according to the present invention, the air-fuel mixture flows from the combustion chamber into the ignition chamber through both the front end side communication hole and the base end side communication hole. The flame can be ejected from the ignition chamber to the combustion chamber mainly through the front end side communication hole. As a result, it has become possible to provide an ignition plug for an engine that can stably perform a spark ignition of an air-fuel mixture and can uniformly eject a flame to a combustion chamber.

  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 previously defining the positions of the ignition chamber, the ignition point, and the communication hole and integrally forming the plug cover on the plug body. As a result, the ignition chamber, the ignition point, and the communication hole can be arranged at appropriate positions simply by attaching the ignition plug to the cylinder head. Therefore, it is possible to easily attach the spark plug to the engine.

Cross section of the main part of the engine Sectional drawing of the principal part of the ignition plug in 1st Embodiment. Sectional drawing of the principal part of the ignition plug in 2nd Embodiment. Sectional view of the base side communication hole in the reference example Sectional drawing of the base end side communication hole in another embodiment Sectional drawing of the principal part of the spark plug in another embodiment Sectional drawing of the principal part of the spark plug in another embodiment

[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 A spark plug for an engine 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 the 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 Q 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 timing at which the piston 2 is positioned immediately before 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. An ignition chamber 14 having an ignition point 11 is formed in the plug cover 13.
Here, the axial center direction of the combustion chamber 3 is a direction along the central axis Q of the combustion chamber 3, for example, the same direction as the vertical movement direction of the piston 2.

  The plug cover 13 is formed with a plurality of communication 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 communication hole 15, and jets the flame formed by the combustion into the combustion chamber 3 through the communication 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 ejection of flame from the ignition chamber 14 to the combustion chamber 3 are performed by the plurality of communication holes 15, so that the combustion chamber 3 is inhaled. The air-fuel mixture M is burned. Therefore, 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 communication hole 15, and fuel and air-fuel mixture are supplied to the ignition chamber 14 from other than the combustion chamber 3. Never happen.

[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 communication hole 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 communication 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 communication hole]
Based on FIG. 2, the structure of the communication hole 15 provided in the plug cover 13 will be described.
The plurality of communication holes 15 are arranged in the axial direction (vertical direction in FIG. 2) more than the front end side communication holes 16 provided on the front end side (lower side in FIG. 2) of the plug cover 13 and the front end side communication holes 16. It is comprised from the base end side communication hole 17 with which the base end side (upper side in FIG. 2) of the plug cover 13 was equipped.

One tip side communication hole 16 is provided at the tip position of the plug cover 13 on the central axis Q of the combustion chamber 3, and a plurality (for example, four) are provided at regular intervals on the circumference centered on the tip position. ) Is provided.
With respect to the arrangement position of the base end side communication hole 17, the distance from the lower end portion 6 a of the cylinder head 6 to the tip end portion of the plug cover 13 in the axial direction is D. It is provided in the base end side of the plug cover 13 rather than the center position P of D / 2 from the lower end part 6a. Thereby, in the axial direction, both the ignition chamber side end portion 17a and the combustion chamber side end portion 17b, that is, the base end side communication hole 17 as a whole are located closer to the base end side of the plug cover 13 than the center position P. Is provided.

Thus, since the base end side communication hole 17 is provided in the base end side of the plug cover 13 rather than the center position P of D / 2 from the lower end part 6a of the cylinder head 6, in the base end side communication hole 17, The distance from the ignition chamber side end 17a to the ignition point 11 can be shortened, and the supply of the air-fuel mixture M to the ignition point 11 can be performed accurately. In addition, since the air-fuel mixture M in the combustion chamber 3 flows into the ignition chamber 14 not only from the base end side communication hole 17 but also from the front end side communication hole 16, a sufficient air-fuel mixture flows into the ignition chamber 14. be able to. Thereby, the air-fuel mixture M in the combustion chamber 3 can be sufficiently supplied to the ignition point 11, and the spark ignition for the air-fuel mixture M can be reliably performed.
The base end side communication hole 17 is configured such that the inflow direction of the air-fuel mixture M from the combustion chamber 3 to the ignition chamber 14 is directed obliquely upward, and the air-fuel mixture M flows toward the ignition point 11. Has been. Thereby, the air-fuel mixture M can be made to flow toward the ignition point 11 through the base end side communication hole 17, and also from this point, the supply of the air-fuel mixture M to the ignition point 11 can be performed accurately.

The base end side communication hole 17 is formed in a taper shape whose hole diameter is maximum at the combustion chamber side end 17b and minimum at the ignition chamber side end 17a. On the other hand, the front end side communication hole 16 is formed in a cylindrical shape having the same hole diameter over the combustion chamber end portion 16b and the ignition chamber end portion 16a. The hole diameter of the ignition chamber side end portion 17 a in the base end side communication hole 17 is configured to be smaller than the hole diameter of the ignition chamber side end portion 16 a of the tip end side communication hole 16. Here, for the base end side communication hole 17, for example, an extension in which the hole diameter S <b> 2 of the ignition chamber side end portion 17 a in the base end side communication hole 17 is 0.4 mm and the inner wall portion of the base end side communication hole 17 is extended. A line (see the dotted line in FIG. 2) intersects the central axis of the base end side communication hole 17, and the intersection angle of the extension line at this time is expanded to a set angle α (for example, 23 °), and the combustion chamber side The end portion 17b has a maximum diameter. Moreover, the hole diameter T (hole diameter of the front end side communication hole 17) of the ignition chamber side end part 16a in the front end side communication hole 16 is 1.6 mm, for example.
Incidentally, in FIG. 2, the direction of the front end side communication hole 16 positioned at the front end position of the plug cover 13 and the direction of the front end side communication hole 16 positioned around the plug cover 13 are formed in a shape that penetrates the plug cover 13 linearly. However, for example, the direction of the front end side communication hole 16 located around the front end position of the plug cover 13 can be formed in a shape that penetrates the plug cover 13 obliquely along the circumferential direction. The direction of the distal end side communication hole 16 can be appropriately changed.

  Thus, in the base end side communication hole 17, since the diameter of the combustion chamber side end portion 17b is larger than that of the ignition chamber side end portion 17a, the base end side communication hole 17 has a combustion chamber 3 side. The resistance to the fluid flow from the ignition chamber 14 to the ignition chamber 14 side is smaller than the resistance to the fluid flow from the ignition chamber 14 side to the combustion chamber 3 side. Thereby, the fluid easily flows from the combustion chamber 3 to the ignition chamber 14, and conversely, the fluid is difficult to discharge from the ignition chamber 14 to the combustion chamber 3. Accordingly, the air-fuel mixture M can be introduced from the combustion chamber 3 into the ignition chamber 14 through both the front end side communication hole 16 and the base end side communication hole 17, and the flame is ejected from the ignition chamber 14 into the combustion chamber 3. Is hardly performed from the base end side communication hole 17 and can be performed by the front end side communication hole 16. As a result, the flame can be uniformly ejected to the combustion chamber 3 while the spark ignition of the air-fuel mixture M can be performed stably. Further, since the hole diameter of the base end side communication hole 17 is maximum at the combustion chamber side end portion 17b and minimum at the ignition chamber side end portion 17a, the air-fuel mixture M flowing from the combustion chamber 3 into the ignition chamber 14 is obtained. The flow rate can be increased. Therefore, the flow of the burned gas remaining in the ignition chamber 14 can be promoted and actively discharged from the ignition chamber 14, and the spark ignition of the air-fuel mixture M can be stabilized more accurately.

[Second Embodiment]
This 2nd Embodiment is another embodiment about the structure of the base end side communication hole 17 in the said 1st Embodiment. Based on FIG. 3, the base end side communication hole 17 in 2nd Embodiment is demonstrated. Since other configurations are the same as those in the first embodiment, description thereof is omitted.

  In the base end side communication hole 17, the ignition chamber side end portion 17 a is provided closer to the base end side of the plug cover 13 than the ignition point 11 in the axial direction. Thereby, in the axial direction of the combustion chamber 3, the ignition point 11 can be positioned between the ignition chamber side end portion 16 a in the front end side communication hole 16 and the ignition chamber side end portion 17 a in the base end side communication hole 17. it can. Therefore, the air-fuel mixture M in the combustion chamber 3 can be supplied to the ignition point 11 from both one side and the other side in the axial direction of the combustion chamber 3. Enough supply can be ensured. As a result, the spark ignition of the air-fuel mixture M in the ignition chamber 14 can be performed stably and accurately.

[Another embodiment]
(1) In the first embodiment, the base end side communication hole 17 is such that the inflow direction of the air-fuel mixture M from the combustion chamber 3 to the ignition chamber 14 faces obliquely upward, and mixing toward the ignition point 11 is performed. For example, as shown in FIG. 4, the base end side communication hole 17 may be configured so that the inflow direction of the air-fuel mixture M is directed in the lateral direction.

As for the shape of the base end side communication hole 17, as shown in the first and second embodiments and FIG. 4, the hole diameter is maximum at the combustion chamber side end 17b and minimum at the ignition chamber side end 17a. Various shapes can be applied without being limited to the tapered shape.
For example, as shown in FIG. 5 (a), the hole diameter of the combustion chamber side end 17b is set to the maximum hole diameter, and the ignition chamber 14 side is more than the center position between the combustion chamber side end 17b and the ignition chamber side end 17a. The minimum hole diameter of the ignition chamber side end portion 17a is larger than the minimum hole diameter and smaller than the hole diameter of the combustion chamber side end portion 17b, and between the combustion chamber side end portion 17b and the portion having the minimum hole diameter, and The base end side communication hole 17 can be formed in a shape in which the portion between the minimum hole diameter and the ignition chamber side end portion 17a is linear.

Further, as shown in FIG. 5 (b), the hole diameter of the combustion chamber side end portion 17b is set to the maximum hole diameter, and the ignition chamber 14 side from the center position between the combustion chamber side end portion 17b and the ignition chamber side end portion 17a. A portion for maintaining the minimum hole diameter by a set length as the minimum hole diameter, the hole diameter of the ignition chamber side end portion 17a is larger than the minimum hole diameter and smaller than the hole diameter of the combustion chamber side end portion 17b, and the combustion chamber side The base end side communication hole 17 is formed in a shape in which the end portion 17b and one end portion of the portion maintaining the minimum hole diameter and the other end portion of the portion maintaining the minimum hole diameter and the ignition chamber side end portion 17a are linear. Can be formed.
Further, as shown in FIG. 5 (c), the hole diameter of the combustion chamber side end portion 17b is set to the maximum hole diameter, and the ignition chamber 14 side is more than the center position between the combustion chamber side end portion 17b and the ignition chamber side end portion 17a. The minimum hole diameter of the ignition chamber side end portion 17a is larger than the minimum hole diameter and smaller than the hole diameter of the combustion chamber side end portion 17b, and between the combustion chamber side end portion 17b and the portion having the minimum hole diameter, and The base end side communication hole 17 can be formed in a curved shape between the portion having the minimum hole diameter and the ignition chamber side end portion 17a.

(2) In the above embodiment, the numbers of the distal end side communication holes 16 and the proximal end side communication holes 17 can be appropriately changed.
In addition, regarding the arrangement positions of the distal end side communication hole 16 and the proximal end side communication hole 17, the distal end side communication hole 16 is provided at the same position in the axial direction in the first and second embodiments. The distal end side communication holes 16 can be provided so as to be arranged at intervals in the axial direction, and the proximal end side communication holes 17 can also be provided so as to be arranged at intervals in the axial direction.

(3) In the first and second embodiments, the ignition point 11 is disposed closer to the cylinder head 6 than the lower end 6a of the cylinder head 6 in the axial direction of the combustion chamber 3. The point 11 can also be arranged closer to the combustion chamber 3 than the lower end 6 a of the cylinder head 6 in the axial direction of the combustion chamber 3.

(4) In the first and second embodiments, as shown in FIGS. 2 and 3, the front end side communication hole 16 has the same hole diameter across the combustion chamber end portion 16b and the ignition chamber end portion 16a. For example, as shown in FIG. 6, the tip side communication hole 16 is the same as the base end side communication hole 17, and the diameter of the hole is maximized at the combustion chamber side end 16 b, as shown in FIG. 6. It can be formed in a taper shape that is the smallest at 16a. By forming in this way, compared with the case where the combustion chamber side end portion 16b and the ignition chamber side end portion 16a have the same diameter, the inflow of the air-fuel mixture M from the combustion chamber 3 to the ignition chamber 14 is prevented. It becomes easy. Here, as in the first and second embodiments, the hole diameter of the ignition chamber side end portion 17a in the base end side communication hole 17 is smaller than the hole diameter of the ignition chamber side end portion 16a of the tip end side communication hole 16. In addition, the diameter of the combustion chamber side end portion 17 b in the base end side communication hole 17 is configured to be larger than the diameter of the combustion chamber side end portion 17 b in the distal end side communication hole 16.
Although not shown, contrary to the base end side communication hole 17, the front end side communication hole 16 is formed in a tapered shape whose hole diameter is maximum at the ignition chamber side end portion 16 a and minimum at the combustion chamber side end portion 16 b. You can also By forming in this way, when the flame is ejected from the ignition chamber 14 to the combustion chamber 3, the flame is more easily ejected from the distal end side communication hole 16 than the proximal end side communication hole 17.

(5) In the first and second embodiments, the shape of the plug cover 13 can be changed as appropriate. For example, as shown in FIG. 13 can be integrally formed at the tip of the plug body 12 so as to cover the ignition point 11.
In the first and second embodiments and FIG. 7, the spark plug in which the plug cover 13 is formed integrally with the plug body 12 is illustrated, but the plug cover 13 is formed separately from the plug body 12. You can also.

  In the present invention, an ignition plug having an ignition chamber formed in a plug cover that covers an ignition point is mounted on a cylinder head, and a plurality of communication holes that connect the ignition chamber and a combustion chamber facing a piston are formed in the plug cover. It is possible to supply a sufficient amount of the air-fuel mixture in the combustion chamber to the ignition point, and it is possible to uniformly ignite the flame to the combustion chamber while reliably performing spark ignition on the air-fuel mixture. It can be applied to various engines and engine spark plugs.

2 Piston 3 Combustion chamber 6 Cylinder head 10 Spark plug (engine spark plug)
DESCRIPTION OF SYMBOLS 11 Ignition point 12 Plug body 13 Plug cover 14 Ignition chamber 15 Communication hole 16 Front end side communication hole 16a Ignition chamber side end 16b Combustion chamber side end 17 Base end side communication hole 17a Ignition chamber side end 17b Combustion chamber side end M mixture

Claims (6)

An ignition 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 communication holes that connect 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,
In the axial direction, the plurality of communication holes include a front end side communication hole provided on a front end side of the plug cover that protrudes into the combustion chamber, and a base end side of the plug cover from the front end side communication hole. It is composed of provided proximal end side communication holes,
The base end side communication hole is configured such that a resistance to a fluid flow from the combustion chamber side to the ignition chamber side is smaller than a resistance to a fluid flow from the ignition chamber side to the combustion chamber side,
In the base end side communication hole, the inflow direction of the air-fuel mixture from the combustion chamber to the ignition chamber is directed obliquely upward ,
The base end side communication hole is configured such that the hole diameter of the combustion chamber side end portion is larger than the hole diameter of the ignition chamber side end portion,
The hole diameter of the ignition chamber side end portion in the base end side communication hole is configured to be smaller than the hole diameter of the ignition chamber side end portion of the tip side communication hole,
The engine in which the hole diameter of the combustion chamber side end portion in the base end side communication hole is configured to be larger than the hole diameter of the combustion chamber side end portion of the tip end side communication hole . 2. The engine according to claim 1, wherein the base end side communication hole is configured to have a taper shape in which a hole diameter is maximum at a combustion chamber side end and is minimum at an ignition chamber side end. The ignition point is disposed closer to the cylinder head than the lower end of the cylinder head in the axial direction of the combustion chamber,
The base end side communication hole has an end portion on the ignition chamber side that is closer to the base end side of the plug cover than the center position from the lower end portion of the cylinder head to the tip end portion of the plug cover in the axial direction. The engine according to claim 1 or 2 , wherein the engine is provided. The proximal-side communication hole, according to any one of claim 1 to 3, the ignition chamber end portion is provided on the proximal end side of the plug cover than the ignition point in the axial direction engine. A plug body having an ignition point; and a plug cover provided on the plug body so as to cover the ignition point;
In the state where the plug body and the plug cover are mounted on the cylinder head of the engine, a plurality of communication 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,
In the axial direction, the plurality of communication holes include a front end side communication hole provided on a front end side of the plug cover that protrudes into the combustion chamber, and a base end side of the plug cover from the front end side communication hole. It is composed of provided proximal end side communication holes,
The base end side communication hole is configured such that a resistance to a fluid flow from the combustion chamber side to the ignition chamber side is smaller than a resistance to a fluid flow from the ignition chamber side to the combustion chamber side,
In the base end side communication hole, the inflow direction of the air-fuel mixture from the combustion chamber to the ignition chamber is directed obliquely upward ,
The base end side communication hole is configured such that the hole diameter of the combustion chamber side end portion is larger than the hole diameter of the ignition chamber side end portion,
The hole diameter of the ignition chamber side end portion in the base end side communication hole is configured to be smaller than the hole diameter of the ignition chamber side end portion of the tip side communication hole,
An engine ignition plug configured such that a hole diameter at a combustion chamber side end portion in the base end side communication hole is larger than a hole diameter at a combustion chamber side end portion in the distal end side communication hole . The engine spark plug according to claim 5 , wherein the plug cover is formed integrally with the plug body.

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