internal combustion engine

Abstract

To reduce the sizes of a cap and a plug hole for mounting an ignition plug to a cylinder head in an internal combustion engine including the cap in which an auxiliary chamber accommodating a center electrode and a ground electrode is provided.SOLUTION: An internal combustion engine 1 includes: an ignition plug 2 mounted to a cylinder head 6 and having a center electrode 21 and a ground electrode 22; a cap 3 that is interposed between the ignition plug 2 and the cylinder head 6 and has a flange 31 and in which an auxiliary chamber 3s accommodating the center electrode 21 and the ground electrode 22 and communicated with a main chamber 71 of a combustion chamber 7 is provided; and a first seal member 4 disposed between the flange 31 of the cap 3 and the ignition plug 2. A projecting part 31x for receiving a tool to be used when the cap 3 is mounted to the cylinder head 6 and an annular projection 311 abutting on the seal member 4 are provided on an upper surface 31a of the flange 31 of the cap 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a spark ignition internal combustion engine. [Background technology]

[0002] Conventionally, in spark ignition internal combustion engines, it has been considered to use a cap that has an internal sub-chamber that houses the center electrode and ground electrode of the spark plug in order to optimize the propagation speed of combustion (see, for example, Patent Document 1).

[0003] In the configuration described in Patent Document 1, after the air-fuel mixture is ignited in the pre-chamber, the combustion is propagated from the pre-chamber to the combustion chamber through an introduction hole provided in the cap. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-159778 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when installing a spark plug and cap such as that described in Patent Document 1 on a cylinder head, it is necessary to use a jig to install the cap on the cylinder head, which creates the problem of the cap becoming larger due to the need to secure space for installing the jig.

[0006] An object of the present invention is to provide a cap that is provided with an auxiliary chamber for accommodating a center electrode and a ground electrode therein, and that can be made smaller in size in an internal combustion engine having such a cap. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention provides an ignition plug that is attached to a cylinder head and has a center electrode and a ground electrode; a cap that is interposed between the ignition plug and the cylinder head and has a flange, and that houses the center electrode and the ground electrode of the ignition plug and has an auxiliary chamber inside that communicates with the combustion chamber; and a seal member that is disposed between the flange of the cap and the ignition plug, and the cap flange is provided with a recess on the upper surface thereof for receiving a tool used to attach the cap to the cylinder head, and an annular protrusion that abuts against the seal member. The recess is provided on the outer side of the annular protrusion. It constituted an internal combustion engine. [Effects of the Invention]

[0008] According to the present invention, in an ignition plug having a cap with an auxiliary chamber therein for accommodating a center electrode and a ground electrode, it is possible to reduce the size of such a cap. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a main part of an internal combustion engine according to an embodiment of the present invention; [Figure 2] FIG. 3 is a perspective view showing the upper half of the cap according to the embodiment. [Figure 3] FIG. [Figure 4] FIG. 4 is a perspective view showing a manner in which the cap according to the embodiment is attached. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described below with reference to FIGS.

[0011] The internal combustion engine 1 according to this embodiment is a port-injection, spark-ignition, four-stroke engine that injects fuel such as gasoline or hydrogen into an intake port (not shown) and introduces an air-fuel mixture into the combustion chamber, and as shown in Fig. 1, it is equipped with at least an ignition plug 2, a cap 3 that is interposed between the spark plug 2 and a cylinder head 6 and has a flange 31 at its upper portion, or more precisely, at its upper end portion, a first seal member 4 that is disposed between the spark plug 2 and an upper surface 31a of the flange 31 of the cap 3, and a second seal member 5 that is disposed between a lower surface 31b of the cap flange 31 and an upper surface 6a of the cylinder head 6. Reference numeral 6w denotes a water jacket.

[0012] The spark plug 2 is a conventional one that is attached to the cylinder head 6 and includes a center electrode 21 and a ground electrode 22. Although the entire spark plug 2 is shown as a single unit in FIG. 1, insulation is provided between the center electrode 21 and the ground electrode 22.

[0013] As described above, the cap 3 is interposed between the spark plug 2 and the cylinder head 6, can be assembled to the cylinder head 6 independently of the spark plug 2, and has a flange 31 on its upper part. When the cap 3 is attached to the cylinder head 6, the first seal member 4 is interposed between the upper surface 31a of the flange 31 and the spark plug 2, and the second seal member 5 is interposed between the lower surface 31b of the flange 31 and the upper surface 6a of the cylinder head 6. The first and second seal members 4, 5 are both gaskets made of a material with a lower hardness than the cap 3. However, other sealing materials may be used instead of gaskets.

[0014] 1, the outer surface 3a of the cap 3 is provided with a male thread 3a1, and the inner surface 3b is provided with a female thread 3b1 for mounting the spark plug 2. The male thread 3a1 and the female thread 3b1 are offset in the axial direction, i.e., the up-down direction. The cap 3 is mounted in the plug mounting hole 6h of the cylinder head 6 by threading the male thread 3a1 into the female thread 6h1 formed in the plug mounting hole 6h of the cylinder head 6, and the spark plug 2 is mounted in the spark plug receiving hole 3h formed inside the cap 3 by threading the male thread 2a1 formed on the outer surface 2a of the spark plug 2 into the female thread 3b1 on the inner surface 3b of the cap 3.

[0015] Furthermore, the cap 3 has an auxiliary chamber 3s therein that houses the center electrode 21 and ground electrode 22 of the spark plug 2. The auxiliary chamber 3s is connected to the main chamber 71 of the combustion chamber 7 through the hole 3s1. In other words, as shown in FIG. 1 and as described above, the cap 3 can be attached to the plug mounting hole 6h of the cylinder head 6 with the spark plug 2 attached to the spark plug receiving hole 3h formed inside the cap 3. With the spark plug 2 attached, the auxiliary chamber 3s is formed at the bottom of the cap 3, housing the center electrode 21 and ground electrode 22 and communicating with the main chamber 71 of the combustion chamber 7. In this embodiment, an air-fuel mixture is introduced into the auxiliary chamber 3s and ignited by a spark. The ignited air-fuel mixture is then introduced into the main chamber 71 through the hole 3s1, where combustion propagates.

[0016] 1 and 2, in this embodiment, the outer periphery of the upper surface 31a of the flange 31 is formed with a plurality of recesses 31x for receiving a jig J, which is a tool used to attach the cap 3 to the cylinder head 6. In this embodiment, the recesses 31x are formed at four locations at 90-degree intervals. More specifically, the cap 31 is screwed onto the cylinder head 6 using a jig J as shown in FIG. 3. The jig J has a protrusion J1 at its tip end that can engage with the recesses 31x of the cap 3, and a protrusion J2 at its base end that can engage with a tool such as a box wrench (not shown) and receive an operating force. In addition, the opening edges of the recesses 31x are chamfered 31y.

[0017] In addition, an annular projection 311 that comes into contact with the first seal member 4 is provided in a portion of the upper surface 31a of the flange 31 between the recess 31x and the ignition plug receiving hole 3h, as shown in FIGS.

[0018] As shown in Fig. 4, the cap 3 according to this embodiment is attached to the cylinder head 6 by engaging the protrusion J1 of the jig J with the recess 31x on the upper surface 31a of the flange 31 and threading the male thread 3a1 into the female thread 6h1 of the plug mounting hole 6h. Thereafter, the ignition plug 2 is attached to the cap 3 by threading the male thread 2a1 formed on the outer surface 2a of the spark plug 2 into the female thread 3b1 of the cap 3. Here, with the cap 3 attached to the cylinder head 6 and the spark plug 2 attached to the cap 3, the space between the cylinder head 6 and the cap 3 is sealed by the second seal member 5, as shown in Fig. 1, and thus the combustion chamber 7 is isolated from the space above the cylinder head 6. In addition, the tip of the annular protrusion 311 provided on the upper surface 31a of the flange 31 of the cap 3 is in linear contact with the first seal member 4, and the annular protrusion 311 is pressed against the first seal member 4 by the axial force when the spark plug 2 is screwed into the cap 3, thereby sealing the space between the flange 31 of the cap 3 and the spark plug 2.

[0019] As described above, according to the configuration of this embodiment, a recess 31x for receiving the jig J (protrusion J1) is provided on the upper surface 31a of the flange 31 of the cap 3, so that the diameter of the jig can be kept within the diameter of the cap 3.

[0020] In addition, an annular protrusion 311 that abuts against the first seal member 4 is provided on the upper surface 31a of the flange 31 of the cap 3, so that the axial force when screwing the ignition plug 2 into the cap 3 can be transmitted more effectively to the first seal member 4, thereby making it possible to more effectively seal between the ignition plug 2 and the cap 3.

[0021] Furthermore, since the opening edge of the recess 31x is chamfered 31y, it is possible to prevent burrs from being generated on the opening edge of the recess 31x.

[0022] In addition, a second seal member 5 is disposed between the lower surface 31b of the flange 31 of the cap 3 and the upper surface 6a of the cylinder head 6, and this seal member 5 can sandwich the cylinder head 6 to seal between the combustion chamber 7 side and the opposite side.

[0023] Furthermore, the male thread 3a1 provided on the outer surface 3a of the cap 3 for attachment to the plug mounting hole 6h of the cylinder head 6 and the female thread 3b1 provided on the inner surface 3b for attachment of the ignition plug 2 are positioned offset from each other, so there is no need to make the cap 3 thick in order to simultaneously provide male and female threads on both the inner and outer surfaces of the cap 3 while ensuring the strength of the cap 3, and it is also possible to reduce the diameter of the plug mounting hole 6h and make the cap 3 itself lighter.

[0024] The present invention is not limited to the above-described embodiment.

[0025] For example, the number and shape of recesses provided in the flange of the cap to accommodate a tool used to attach the cap to the cylinder head may be set arbitrarily.

[0026] Any tool may be used to attach the cap to the cylinder head.

[0027] In addition, the seal between the spark plug and the cap and the seal between the cap and the cylinder head may of course employ various configurations other than the low-hardness seal member used in the above-described embodiment. Furthermore, the shape of the tip of the annular protrusion provided on the upper surface of the cap flange that abuts against the seal member is not limited to the triangular shape shown in the illustration, but may be any other shape, such as a semicircular shape.

[0028] The flange formed on the cap is preferably provided at the upper end as in the above-described embodiment, but may be provided at any location as long as a recess can be formed to accommodate the tool used to attach the cap from above.

[0029] In addition, various modifications may be made without departing from the spirit of the present invention. [Explanation of symbols]

[0030] 1...Internal combustion engine 2...Spark plug 21...Center electrode 22...Ground electrode 3...Cap 31...Flange 31a...Top surface of flange 31x…recess 311...Ring-shaped protrusion 3s…Antechamber 4...(first) sealing member 6...Cylinder head 7...Combustion chamber J...Tool (jig)

Claims

[Claim 1] a spark plug attached to the cylinder head and having a center electrode and a ground electrode; a cap interposed between the spark plug and the cylinder head, having a flange, housing a center electrode and a ground electrode of the spark plug, and having an auxiliary chamber therein communicating with the combustion chamber; An internal combustion engine including a seal member disposed between the flange of the cap and the spark plug, a recess for receiving a tool used to attach the cap to the cylinder head and an annular protrusion for contacting the seal member are provided on an upper surface of the flange of the cap; The recess is provided on the outside of the annular protrusion.

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