Spark plug
阅读说明:本技术 火花塞 (Spark plug ) 是由 后藤大希 伴谦治 后泽达哉 津荷俊介 于 2019-07-01 设计创作,主要内容包括:本发明提供一种火花塞,能够减少热损失并提高发动机效率。将在火花塞(100)配置于内燃机时喷孔(61)的中心轴线(HX)与位于上止点的活塞(65)的上表面(65A)相交的点设为交点(S)。以交点(S)与活塞(65)的上表面(65A)的中心(P)之间的距离(L)与气缸的内孔半径(Rb)满足关系式0.5Rb≤L≤Rb的方式构成喷孔(61)。当这样构成喷孔(61)时,能够抑制因活塞(65)、气缸盖吸收热所致的热损失。由此,本结构的火花塞(100)能够提高发动机效率。(The invention provides a spark plug which can reduce heat loss and improve engine efficiency. A point where the center axis (HX) of the injection hole (61) intersects the upper surface (65A) of the piston (65) positioned at the top dead center when the spark plug (100) is disposed in the internal combustion engine is defined as an intersection point (S). The nozzle hole (61) is configured such that the distance (L) between the intersection point (S) and the center (P) of the upper surface (65A) of the piston (65) and the bore radius (Rb) of the cylinder satisfy the relationship 0.5Rb < L < Rb. When the injection hole (61) is formed in this way, heat loss due to heat absorption by the piston (65) and the cylinder head can be suppressed. Thus, the spark plug (100) of the present configuration can improve engine efficiency.)
1. A spark plug is provided with:
a center electrode;
a ground electrode having an opposing portion that faces a front end portion of the center electrode, a discharge gap being formed between the opposing portion and the front end portion of the center electrode;
a cylindrical insulator for accommodating the center electrode therein in a state in which the distal end portion of the center electrode is exposed from a distal end of the cylindrical insulator itself;
a main body metal member that accommodates the insulator therein; and
a cover portion that covers the front end portion of the center electrode and the facing portion of the ground electrode from the front side,
the cover part is provided with a spray hole,
a portion of the cover portion on a front end side of the injection hole is thinner than a portion on a rear end side of the injection hole,
the injection hole is configured such that a distance L between an intersection S where a center axis of the injection hole intersects with an upper surface of a piston positioned at a top dead center and a center P of the upper surface of the piston when the spark plug is disposed in an internal combustion engine and a bore radius Rb of a cylinder satisfy the following relational expression (1),
the relation (1) is that L is more than or equal to 0.5Rb and less than or equal to Rb.
2. A spark plug is provided with:
a center electrode;
a ground electrode having an opposing portion that faces a front end portion of the center electrode, a discharge gap being formed between the opposing portion and the front end portion of the center electrode;
a cylindrical insulator for accommodating the center electrode therein in a state in which the distal end portion of the center electrode is exposed from a distal end of the cylindrical insulator itself;
a main body metal member that accommodates the insulator therein; and
a cover portion that covers the front end portion of the center electrode and the facing portion of the ground electrode from the front side,
the cover part is provided with a spray hole,
an angle formed by an axis of the spark plug and a central axis of the injection hole is 75 DEG to 125 DEG,
the injection hole is configured such that a center axis of the injection hole intersects with an inner surface of a cylinder head when the spark plug is disposed in the internal combustion engine.
Technical Field
The present invention relates to a spark plug.
Background
Spark plugs with prechamber spaces have been developed. For example, patent document 1 discloses a spark plug including a prechamber space having a volume smaller than that of a main combustion chamber and disposed in a center portion on a cylinder head side, and an injection hole capable of exchanging gas at a boundary between the prechamber space and the main combustion chamber. In this spark plug, when the pilot chamber space is ignited, a torch-like flame is jetted from the jet hole into the main combustion chamber, and the mixture gas in the main combustion chamber is combusted.
Patent document
Patent document 1: japanese patent laid-open publication No. 2007 and 40174
Disclosure of Invention
Problems to be solved by the invention
However, in the technique disclosed in patent document 1, the injected flame contacts the piston and the cylinder head, and is absorbed by heat, which causes heat loss. As a result, there is a problem of a decrease in engine efficiency.
The present invention has been made in view of the above circumstances, and an object thereof is to reduce heat loss and improve engine efficiency. The present invention can be implemented as follows.
Means for solving the problems
(1) A spark plug is provided with: a center electrode; a ground electrode having an opposing portion that faces a front end portion of the center electrode, a discharge gap being formed between the opposing portion and the front end portion of the center electrode; a cylindrical insulator for accommodating the center electrode therein in a state in which the distal end portion of the center electrode is exposed from a distal end of the cylindrical insulator itself; a main body metal member that accommodates the insulator therein; and a cover portion that covers the tip portion of the center electrode and the facing portion of the ground electrode from the front side, the cover portion including an injection hole, a portion of the cover portion on the front end side of the injection hole being thinner than a portion on the rear end side of the injection hole, the injection hole being configured such that a distance L between an intersection point S where a central axis of the injection hole intersects an upper surface of a piston at a top dead center and a center P of the upper surface of the piston and a bore radius Rb of a cylinder satisfy the following relational expression (1) when the spark plug is disposed in an internal combustion engine,
the relation (1) is that L is more than or equal to 0.5Rb and less than or equal to Rb.
In the spark plug of the present configuration, a portion of the cover portion on the front end side of the injection hole is thinner than a portion on the rear end side of the injection hole. This can prevent the portion of the cover portion on the tip side of the injection hole from accumulating heat and becoming hot, thereby preventing pre-ignition of the main combustion chamber. In this configuration, the portion of the cover portion on the rear end side of the injection hole is thicker than the portion on the front end side, and therefore the mechanical strength of the cover portion can be ensured.
Further, in the spark plug of the present configuration, the injection hole is configured such that the distance L between the center axis of the injection hole and the center P of the upper surface of the piston, which is located at the top dead center, and the center point S of the upper surface of the piston satisfy the above-described relational expression (1) when the spark plug is disposed in the internal combustion engine. When the injection holes are formed in this manner, heat loss due to heat absorption by the piston and the cylinder head can be suppressed. Thus, the spark plug of the present configuration can improve engine efficiency.
(2) A spark plug is provided with: a center electrode; a ground electrode having an opposing portion that faces a front end portion of the center electrode, a discharge gap being formed between the opposing portion and the front end portion of the center electrode; a cylindrical insulator for accommodating the center electrode therein in a state in which the distal end portion of the center electrode is exposed from a distal end of the cylindrical insulator itself; a main body metal member that accommodates the insulator therein; and a cover portion that covers the tip portion of the center electrode and the facing portion of the ground electrode from the front side, the cover portion including an injection hole, an angle formed by an axis of the spark plug and a central axis of the injection hole being 75 ° or more and 125 ° or less, the injection hole being configured such that the central axis of the injection hole intersects an inner surface of a cylinder head when the spark plug is disposed in an internal combustion engine.
In the spark plug of the present configuration, the injection hole is configured such that a center axis of the injection hole intersects with an inner surface of the cylinder head when the spark plug is disposed in the internal combustion engine. When the injection hole is formed in this manner, heat loss due to heat absorption by the top surfaces of the piston and the cylinder head can be suppressed. Thus, the spark plug of the present configuration can improve engine efficiency.
Drawings
Fig. 1 is a sectional view showing the structure of a spark plug of the first embodiment.
Fig. 2 is a partially enlarged sectional view of the spark plug of the first embodiment.
Fig. 3 is a cross-sectional view showing a state in which the spark plug of the first embodiment is disposed in an internal combustion engine.
Fig. 4 is a sectional view showing the structure of a spark plug in the second embodiment.
Fig. 5 is a partially enlarged sectional view of a spark plug in a second embodiment.
Fig. 6 is a cross-sectional view showing a state in which the spark plug according to the second embodiment is disposed in an internal combustion engine.
Fig. 7 is a cross-sectional view showing a state in which the spark plug in experimental example 2 is disposed in an internal combustion engine.
Fig. 8 is a cross-sectional view showing a state in which the spark plug in experimental example 4 is disposed in an internal combustion engine.
Fig. 9 is a partially enlarged sectional view of a spark plug according to another embodiment.
Detailed Description
< first embodiment >
Hereinafter, a first embodiment of the
Fig. 1 is a sectional view showing a schematic structure of a
In fig. 1, a center axis CX (axis of the spark plug) of the
The
The
The
The
The
As shown in fig. 2, cover 50 has a plurality of nozzle holes 61 formed on the rear end side of its top 51A. For example, 4 to 8 injection holes 61 are formed. The nozzle holes 61 are substantially cylindrical through holes. The plurality of injection holes 61 are located on an imaginary circle centered on the central axis CX of the
A prechamber space 63 (ignition chamber) which is a space covered with
A
For example, in a cross-sectional view (fig. 2) obtained by cutting the
The thickness of the
In the present embodiment, the thickness of
In the present embodiment, as shown in fig. 3, a
The
The relation (1) 0.5Rb < L < Rb ≦ Rb
That is, in fig. 3, the intersection S is located within the range E.
Preferably, the relational expression (2) is satisfied, and more preferably, the relational expression (3) is satisfied.
Relation (2) 0.7Rb ≦ L ≦ Rb
The relation (3) 0.8Rb < L < Rb
Next, the operational effects of the
In
Further, the
That is, when the intersection S is closer to the center P than the range E of fig. 3, the time during which the combustion gas contacts the
Further, when the intersection S is located outside the range E of fig. 3, the cylinder head absorbs heat, and the heat loss increases, resulting in a decrease in engine efficiency.
In the
< second embodiment >
Next, a
The
As shown in fig. 5, a plurality of injection holes 161 are formed at the front end of the
In the present embodiment, as shown in fig. 6, an angle θ (an angle between the injection hole and the central axis CX) formed by the central axis CX of the
The total height H of the
The angle θ is preferably 75 ° or more and 110 ° or less, and more preferably 75 ° or more and 100 ° or less. In both cases of fig. 6 and 8, the angle θ is set to 90 °.
Next, the operational effects of the
In the
That is, if the requirements of the present configuration are not satisfied, the engine efficiency is reduced by either of the following (1) and (2).
(1) The time during which the combustion gas contacts the
(2) The
In the
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