JP2019087333A - Spark plug device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a load applied to a ground electrode and a center electrode and extend the life of a spark plug device. A spark plug device including a rod-shaped center electrode 5 and a dome-shaped plug cover 4 surrounding the center electrode 5 with a gap provided when viewed from the axis direction of the center electrode 5. A flat plate-shaped ground electrode 6 surrounding the center electrode 5 is provided. [Selection diagram] Fig. 2

Description

  The present invention relates to a spark plug device.

  For example, Patent Document 1 discloses a spark plug (ignition plug device) in which a sub combustion chamber (ignition chamber) is formed by a housing and a plug cover fixed in contact with the housing. Such a spark plug is attached to a combustion chamber of an internal combustion engine, and a high voltage is applied to a center electrode provided in the inside of the housing, thereby providing between the center electrode and the ground electrode provided on the plug cover. Generate a flame kernel. The spark plug ignites the mixture of fuel and air filled in the combustion chamber by the flame kernel.

JP, 2015-130302, A

  As in Patent Document 1, in the spark plug device in which the ground electrode is provided in the plug cover, the ground electrode is provided in one place, and a large load is applied to the tip of the ground electrode and the center electrode when generating a spark. , The ground electrode is easily consumed. In a spark plug apparatus having a ground electrode as described above, if the ground electrode is damaged, a spark can not be generated and can not be ignited.

  The present invention has been made in view of the above-mentioned problems, and aims to reduce the load applied to the ground electrode and the center electrode and to prolong the life of the spark plug device.

  In order to achieve the above object, according to the present invention, an ignition plug device comprising a rod-like central electrode and a dome-shaped plug cover surrounding the central electrode is provided as a first means, and an axial center of the central electrode A configuration is adopted in which a flat plate-like ground electrode is provided surrounding the center electrode by providing a gap as viewed from the direction.

  As a second means, in the first means, a configuration is adopted in which a gap is formed between the ground electrode and the plug cover.

  As a third means, in the second means, the plug cover has an opening, and a gap between the plug electrode and the ground electrode corresponds to the opening when viewed from the axial direction of the center electrode. Adopt a configuration that is provided at the position.

  As a fourth means, in the second or third means, the area of the gap between the ground electrode and the plug cover is larger than the area of the gap between the center electrode and the ground electrode Do.

  As a fifth means, in the fourth means, a plurality of gaps between the ground electrode and the plug cover are provided, and the sum of the areas of the gaps between all the ground electrodes and the plug cover is the center electrode and the center electrode. A configuration is adopted that is larger than the area of the gap with the ground electrode.

  As a sixth means, in any of the first to fifth means, the plug cover is formed with a gas inlet for communicating the space opposite to the dome top portion with respect to the ground electrode and the external space. Adopt the configuration.

  As a seventh means, in the sixth means, the ground electrode has an engagement piece, and the plug cover is formed with a slit in which the engagement piece is engaged, and the slit A configuration is adopted in which the part is the gas inlet.

  As an eighth means, in any one of the first to seventh means, the end face of the center electrode is disposed on the same plane as the surface on the plug cover side of the ground electrode.

  As a ninth means according to any one of the first to eighth means, the plug cover is set to a three-dimensional shape in which the inner wall surface has at least one focal point, and the center electrode is viewed from the axial direction. A configuration is adopted in which it is provided at a position overlapping with the focal point.

  The spark plug device according to the present invention includes a dome-shaped plug cover and a flat plate-like ground electrode surrounding a center electrode. When a spark is generated between the center electrode and the ground electrode, energy from the discharge is released between the center electrode and the ground electrode. By reflecting this energy toward the center electrode by the inner wall surface of the plug cover, the energy density can be increased in the vicinity of the center electrode, and the voltage applied to the center electrode can be reduced. Furthermore, by making the ground electrode flat, the discharge area of the ground electrode and the center electrode becomes wider, so that no load is applied to one point at the ground electrode and the center electrode. Thereby, the consumption of the ground electrode and the center electrode can be suppressed, and even when a part of the ground electrode and the center electrode is damaged, the discharge can be performed at another portion. Therefore, the load applied to the ground electrode and the center electrode can be reduced, and the life of the spark plug device can be extended.

It is a fragmentary sectional view of a spark plug device concerning one embodiment of the present invention. It is an expanded sectional view containing the plug cover of the ignition plug device concerning one embodiment of the present invention. It is a front view containing the plug cover of the ignition plug device concerning one embodiment of the present invention. It is a perspective view of a part of spark plug device concerning one embodiment of the present invention. It is sectional drawing in the direction orthogonal to the central axis of the ground electrode with which the ignition plug device concerning one embodiment of the present invention is provided.

  Hereinafter, an embodiment of a spark plug device according to the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

FIG. 1 is a partial cross-sectional view of a spark plug device 1 according to the present embodiment. FIG. 2 is an enlarged sectional view including the plug cover 4 of the spark plug device 1 according to the present embodiment.
The spark plug device 1 according to the present embodiment is provided, for example, in a combustion chamber of an internal combustion engine or the like, and as shown in FIGS. 1 and 2, the housing portion 2, the insulator 3, the plug cover 4, and the center electrode 5. , A ground electrode 6 and a terminal 7. In the spark plug device 1, an ignition chamber A is formed inside the plug cover 4. The ignition chamber A is a space centered on the focal point A1, and is disposed inside the combustion chamber of the internal combustion engine.

The housing portion 2 is provided on the outer periphery of the center electrode 5 and is a member for holding the center electrode 5. The housing portion 2 has a housing 2a and a gasket 2b fixed to the outer periphery of the housing 2a. The housing 2a has a diameter of the outer periphery substantially equal to the bolt of M14 or M18 defined in Japanese Industrial Standard, is cylindrical around the central axis L, and the plug cover 4 is attached to one end.
Further, the other end side of the housing 2a is expanded in outer diameter, and as shown in FIG. 2, has a substantially hexagonal shape as viewed from the central axis L direction. The gasket 2 b is a member that seals a gap with the internal combustion engine when the spark plug device 1 is attached to the internal combustion engine.

  As shown in FIG. 1, the insulator 3 is a member disposed between the housing 2 a and the center electrode 5, substantially cylindrical around the central axis L, and formed of ceramic or the like. Such an insulator 3 insulates between the housing 2 a and the center electrode 5 and between the housing 2 a and the terminal 7.

  As shown in FIGS. 1 to 4, the plug cover 4 is a bottomed cylindrical metal member having a hemispherical dome-like bottom, and the open end is fixed to the end of the housing 2 a. Further, the plug cover 4 is formed with an ignition opening 4 a. FIG. 3 is a front view including the plug cover 4 of the spark plug device 1 according to the present embodiment. As shown in FIG. 3, the ignition openings 4 a are formed in three places at intervals of 120 ° around the apex of the central axis L. The ignition opening 4a is an opening for allowing the mixture filled in the combustion chamber of the internal combustion engine to flow into the ignition chamber A. FIG. 4 is a perspective view of part of the spark plug device 1. As shown in FIG. 4, the plug cover 4 has slits at three positions at intervals of 120 degrees and in which the ground electrode 6 is engaged in the direction along the central axis L at the end opposite to the bottom of the hemispherical dome shape. It is formed. When the plug cover 4 is attached to the housing 2a with the ground electrode 6 engaged, as shown in FIG. 1, the plug cover 4 introduces a gas between the ground electrode 6 and the housing 2a at the slit. A mouth 4c is formed. That is, the plug cover 4 has a gas inlet 4c in which the area on the housing 2a side (opposite side of the top) of the slit is located between the ground electrode 6 and the inside of the housing 2a and the combustion chamber (external space). It has become.

  The inner wall surface 4b of the plug cover 4 has a spherical shape around a focal point A1 formed on the central axis L. A substantially spherical ignition chamber A centered on the focal point A1 is formed by the spherical inner wall surface 4b of the plug cover 4, the end face 2a1 of the housing 2a, and the end face 3a of the insulator 3. Further, the inner wall surface 4b is spherically shaped to a position where it contacts the housing 2a beyond the focal point A1. That is, the inner wall surface 4b is formed by the range beyond at least half of the spherical surface centering on the focal point A1.

  The center electrode 5 is a substantially cylindrical (rod-like) metal member provided on the center axis L inside the insulator 3, and the tip 5 a protrudes from the end of the insulator 3. That is, the tip 5 a of the center electrode 5 protrudes toward the ignition chamber A. The tip portion 5a is made of a high melting point metal such as iridium or ruthenium, and is disposed closer to the insulator 3 than the focal point A1. Further, an end of the center electrode 5 opposite to the end 5 a is in contact with the terminal 7. When a voltage is applied to the center electrode 5 through the terminal 7, a discharge phenomenon occurs with the ground electrode 6.

  FIG. 5 is a cross-sectional view in the direction orthogonal to the central axis L of the ground electrode 6. As shown in FIG. 5, the ground electrode 6 is a flat plate-like member having a central opening 6a formed at the center, and engaging pieces extending radially outward from three locations at intervals of 120 degrees around the central axis L Is protruding. The ground electrode 6 is entirely composed of a nickel-based heat-resistant alloy, and a substantially annular refractory metal member composed of iridium, ruthenium or the like is embedded in a portion outside the central opening 6a. The engagement piece of the ground electrode 6 engages with the slit of the plug cover 4. Further, as shown in FIG. 2, the surface on the plug cover 4 side of the ground electrode 6 and the end surface of the tip portion 5 a of the center electrode 5 are disposed on the same plane. The ground electrode 6 is an electrode on the negative electrode side with respect to the center electrode 5. The current flowing to the ground electrode 6 is discharged to the cylinder head of the internal combustion engine through the plug cover 4 and the housing 2a.

  Further, at the central opening 6a of the ground electrode 6, the tip end 5a of the central electrode 5 is disposed with a gap S1 as viewed from the direction of the central axis L (axial direction). The sum of the areas of the three gaps S2 formed between the ground electrode 6 and the plug cover 4 when viewed from the direction of the central axis L is greater than the sum of the areas of the gaps S1 between the ground electrode 6 and the center electrode 5 It is set large. Further, the gap S2 is provided at a position (corresponding position) overlapping the ignition opening 4a when viewed from the direction along the central axis L.

  The terminal 7 is a terminal which is in contact with the end opposite to the end 5 a of the center electrode 5 and is disposed inside the insulator 3 on the central axis L. The terminal 7 is connected to an ignition coil (not shown) or the like, and supplies a current generated by the ignition coil or the like to the center electrode 5.

The ignition operation of the spark plug device 1 according to this embodiment will be described.
The current generated by the ignition coil or the like flows to the center electrode 5 via the terminal 7. Thereby, a discharge phenomenon occurs between the center electrode 5 and the ground electrode 6 to form a flame kernel. At this time, in the ignition chamber A, shock waves are generated radially around the gap S1 between the center electrode 5 and the ground electrode 6. The shock wave is reflected by the inner wall surface 4b of the plug cover 4, the end face 2a1 of the housing 2a, and the end face 3a of the insulator 3 and collected in the direction of the focal point A1. As a result, in the ignition chamber A, the energy of the shock wave is concentrated around the focal point A1, the mixture is adiabatically compressed, and the temperature rises sharply. The period until the temperature rise is extremely short compared to the discharge period. Therefore, the mixture in the ignition chamber A is more easily ignited by the temperature rise. Therefore, the spark plug device 1 can be ignited even if the ignition energy supplied is small.

  In addition, the air-fuel mixture of the combustion chamber and the like (outside) flows into the ignition chamber A through the ignition opening 4a, and flows in through the gas inlet 4c. The mixture flowing from the ignition opening 4a flows into the space between the housing 2a and the ground electrode 6 through the gap S2, and is returned to the ignition chamber A through the gap S1. Further, the mixture flowing from the gas inlet 4c flows into the ignition chamber A through the gap S1. The flow of the air-fuel mixture in the spark plug device 1 causes the flame kernel generated in the gap S1 to leave the center electrode 5 and the ground electrode 6 at an early stage. Further, the flame kernels grow in the ignition chamber A, and the high temperature and high pressure flame spreads through the ignition opening 4a to the combustion chamber.

  According to the present embodiment, the spark plug device 1 includes the dome-shaped plug cover 4 and the flat ground electrode 6 surrounding the center electrode 5. By means of the plug cover 4, it is possible to return the shock wave generated at the time of discharge between the center electrode 5 and the ground electrode 6 to the periphery of the center electrode 5, and to raise the temperature around the flame kernel. Therefore, ignition can be performed even if the voltage applied to the center electrode 5 is lower than in the prior art. Furthermore, since the ground electrode 6 is flat, no large load is applied to a part of the ground electrode 6, and even if a part of the ground electrode 6 is damaged, the other part of the ground electrode 6 It can be discharged. Therefore, the load applied to the ground electrode 6 and the center electrode 5 can be reduced, and the life of the spark plug device 1 can be extended. Further, by making the tip portion 5a cylindrical, the discharge area of the center electrode 5 can be increased, and the life of the center electrode 5 can be extended.

  Further, according to the present embodiment, the gap S2 is formed between the ground electrode 6 and the plug cover 4. The mixture of the ignition chamber A flowing into the housing 2a from the gap S2 forms a flow of returning from the gap S1 to the ignition chamber A, whereby the flame kernel formed in the vicinity of the tip 5a of the center electrode 5 The heat loss from the flame kernel to the center electrode 5 and the ground electrode 6 is reduced. Therefore, the spark plug device 1 can form a flame stably in the combustion chamber.

  Further, the gap S2 is provided at a position corresponding to the ignition opening 4a when viewed from the direction along the central axis L, so that the mixture flowing into the ignition chamber A from the ignition opening 4a easily flows into the gap S2. Become. As a result, the mixture of the ignition chamber A flowing into the housing 2a from the gap S2 is more likely to flow back to the ignition chamber A than the gap S1, and a flame can be formed more stably in the combustion chamber.

  Furthermore, the ignition chamber flowing from the gap S2 to the housing 2a side is also set by setting the sum of the areas of the three gaps S2 to be larger than the sum of the areas of the gaps S1 between the ground electrode 6 and the center electrode 5. A flow of the mixture of A returning to the ignition chamber A from the gap S1 is more likely to be formed, and a flame can be formed more stably in the combustion chamber.

  Further, according to the present embodiment, the gas inlet 4c is formed in the plug cover 4 so that the air-fuel mixture is also taken in from the gas inlet 4c, and the flame kernel is quickly taken from the center electrode 5 and the ground electrode 6. It can be separated, and is effective in preventing the flame-out phenomenon.

  Further, a slit is formed in the plug cover 4 and the plug cover 4 is fixed to the housing 2 a in a state where the engagement piece of the ground electrode 6 is engaged with the slit. Thus, the plug cover 4 and the ground electrode 6 can be easily fixed and the number of parts can be minimized.

  Further, according to the present embodiment, the end surface of the center electrode 5 is disposed on the same plane as the surface of the ground electrode 6 on the plug cover 4 side. Thereby, when the ignition is repeatedly performed, the spark emitted from the center electrode 5 uniformly flies at one end of the inner peripheral surface of the center opening 6a of the ground electrode 6 without being biased, so the ground electrode 6 Deplete evenly. In addition, consumption of the center electrode 5 and the ground electrode 6 can be suppressed.

  Further, according to the ignition plug device 1 according to the present embodiment, since the inner wall surface 4b of the plug cover 4 is hemispherical, the energy of the shock wave generated inside the ignition chamber A is reflected and concentrated to the focal point A1. . The mixture at the periphery of the focal point A1 is adiabatically compressed, so that the temperature rises and it becomes easy to be ignited. Thereby, the ignition plug device 1 according to the present embodiment can ignite the mixture even if the voltage applied to the center electrode 5 is reduced. Therefore, it is possible to reduce the load on the center electrode 5 and to prolong the life.

In addition, this invention is not limited to the said embodiment, For example, the following modifications are considered.
(1) In the said embodiment, although the engagement piece of the ground electrode 6 shall be engaged with the slit provided in the plug cover 4, this invention is not limited to this. The spark plug device 1 may be separately provided with a cylindrical member having a recess for fixing the ground electrode 6, and the ground electrode 6 may be fixed by the plug cover 4 and the cylindrical member.

(2) In the above embodiment, the end face of the center electrode 5 is disposed on the same plane as the surface of the ground electrode 6 on the plug cover 4 side, but the present invention is not limited to this. The end face of the center electrode 5 may protrude toward the plug cover 4 more than the ground electrode 6.

(3) Further, the positions of the ignition opening 4a and the gap S2 are not limited to three, and they may not be formed at equal intervals.

(4) Also, the plug cover 4 may have an opening at the vertex (the point of intersection with the central axis L). In this case, the position of the center electrode 5 can be confirmed at the time of assembly, and each component can be installed at an accurate position.

DESCRIPTION OF SYMBOLS 1 ...... Ignition plug apparatus 4 ...... Plug cover 5 ...... Center electrode 6 ...... Grounding electrode A ...... Ignition chamber S1 ... Gap S2 ...... Gap L ...... Central axis

Claims (9)

An ignition plug device comprising: a rod-like center electrode; and a dome-shaped plug cover surrounding the center electrode,
An ignition plug device, comprising: a flat ground electrode which surrounds the center electrode by providing a gap when viewed from the axial center direction of the center electrode.   The spark plug device according to claim 1, wherein a gap is formed between the ground electrode and the plug cover. The plug cover has an opening,
The spark plug device according to claim 2, wherein the ground electrode is provided at a position where a gap with the plug cover corresponds to the opening and the axial direction of the center electrode.   The spark plug device according to claim 2 or 3, wherein an area of a gap between the ground electrode and the plug cover is larger than an area of a gap between the center electrode and the ground electrode. A plurality of gaps are provided between the ground electrode and the plug cover,
The spark plug device according to claim 4, wherein a sum of areas of gaps between all the ground electrodes and the plug cover is larger than an area of gaps between the center electrode and the ground electrode.   The said plug cover is formed with the gas introduction port which connects the space and the external space on the opposite side to a dome top part with respect to the said ground electrode, The said inlet port is described in any one of Claims 1-5. Spark plug device. The ground electrode has an engagement piece,
The plug cover is formed with a slit in which the engagement piece is engaged,
The spark plug device according to claim 6, wherein a part of the slit is the gas inlet.   The spark plug device according to any one of claims 1 to 7, wherein the end face of the center electrode is disposed on the same plane as the surface on the plug cover side of the ground electrode. The plug cover is set to a three-dimensional shape in which the inner wall surface has at least one focal point,
The spark plug device according to any one of claims 1 to 8, wherein the center electrode is provided at a position overlapping with the focal point when viewed from the axial direction.

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