JP7300967B2 - spark plug - Google Patents

Description

The present invention relates to spark plugs.

Conventionally, as a spark plug, a pre-chamber having an injection hole communicating with the main combustion chamber is provided, and an air-fuel mixture is caused to flow into the pre-chamber through the injection hole, and the flame generated in the pre-chamber is passed through the injection hole into the main combustion chamber. There is something to squirt out. For example, Patent Document 1 discloses a configuration in which a large injection hole with a large diameter and a small injection hole with a small diameter are provided as injection holes, and the opening angle between the large injection holes is smaller than the opening angle between the small injection holes. It is In such a configuration, the flames ejected from the large injection holes are diffused outward along the bottom surface of the main combustion chamber from the central portion of the main combustion chamber, and the flames ejected from the small injection holes are diffused to the outer peripheral side of the main combustion chamber. This is intended to completely burn the air-fuel mixture in the main combustion chamber.

Japanese Patent Application Laid-Open No. 2001-227344

However, in the configuration disclosed in Patent Document 1, the ignition energy of the flame ejected from the small nozzle hole is small, so there is a possibility that the ignitability of the air-fuel mixture in the main combustion chamber may deteriorate. Therefore, there is room for improvement in improving ignitability in the main combustion chamber.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and an object of the present invention is to provide a spark plug capable of improving ignitability.

In one aspect of the present invention, a sub-chamber (2) located on the tip side in the axial direction of the plug, a sub-chamber forming portion (30) forming the sub-chamber (2), and a tip portion (11) in the sub-chamber. a center electrode (10) located at
A plurality of injection holes (35) are formed in the sub-chamber forming portion for communicating the sub-chamber with the main combustion chamber (3),
At least two injection holes (351, 352) out of the plurality of injection holes have their respective center lines (L1, L2) at twisted positions, and at the closest position where the distance between the center lines is minimum. is in the spark plug (1), located in the main combustion chamber.

In the spark plug, the center lines of the at least two injection holes provided in the pre-chamber forming portion are twisted relative to each other, so that the flames ejected from the injection holes do not collide with each other. there is Furthermore, the closest position between the centerlines of the two injection holes is located inside the main combustion chamber. As a result, flame turbulence increases due to the Coanda effect in which the flames ejected from the two injection holes approach each other in the main combustion chamber and attract each other. As a result, propagation of flame in the main combustion chamber can be accelerated and ignitability can be improved.

As described above, according to the above aspect, it is possible to provide a spark plug capable of improving ignitability.

It should be noted that the symbols in parentheses described in the claims and the means for solving the problems indicate the corresponding relationship with the specific means described in the embodiments described later, and limit the technical scope of the present invention. not a thing

2 is a side view of the spark plug in Embodiment 1. FIG. The bottom view of the spark plug in Embodiment 1. FIG. FIG. 3 is a side partially enlarged perspective view of the spark plug viewed from the X1 direction in FIG. 2 ; The bottom view of the spark plug in the modification 1. FIG. The bottom view of the spark plug in Embodiment 2. FIG. FIG. 6 is a side partially enlarged perspective view of the spark plug viewed from the X1 direction in FIG. 5 ; (a) A diagram showing the evaluation result of the side view of the spark plug of Test Example 1, (b) The evaluation result of the bottom view of the spark plug of Test Example 1, (c) The side view of the spark plug of Test Example 2 (d) Evaluation results of the bottom view of the spark plug of Test Example 2. FIG. The bottom view of the spark plug in Embodiment 3. FIG. FIG. 8 is a side partially enlarged perspective view of the spark plug viewed from the X1 direction in FIG. 7 ; The bottom view of the spark plug in Embodiment 4. FIG. FIG. 11 is a side partially enlarged see-through view of the spark plug viewed from the X1 direction in FIG. 10; The bottom view of the spark plug in Embodiment 5. FIG. FIG. 13 is a side partially enlarged perspective view of the spark plug viewed from the X1 direction in FIG. 12;

(Embodiment 1)
An embodiment of a spark plug will be described with reference to FIGS. 1 to 3. FIG.
As shown in FIG. 3, the spark plug 1 of the present embodiment includes a pre-chamber 2 located on the tip end side Y1 in the axial direction of the plug, a pre-chamber forming portion 30 forming the pre-chamber 2, and a tip portion within the pre-chamber 2. and a center electrode 10 on which 11 is located.
A plurality of injection holes 35 for communicating the sub chamber 2 with the main combustion chamber 3 are formed in the sub chamber forming portion 30 .
Center lines L1 and L2 of at least two injection holes 351 and 352 of the plurality of injection holes 35 intersect each other within the main combustion chamber 3 .

The spark plug 1 of this embodiment will be described in detail below.
As shown in FIG. 1, a spark plug 1 of this embodiment is attached to a cylinder head 101 of an internal combustion engine so that the tip thereof is exposed to a main combustion chamber 3 of the internal combustion engine. As shown in FIG. 3, the spark plug 1 has a tubular housing 40 whose longitudinal direction is the axial direction Y of the plug. A cylindrical insulator 50 is arranged coaxially with the housing 40 in the housing 40 . A sub-chamber forming portion 30 that forms the sub-chamber 2 is provided on the tip end side Y1 of the housing 40 in the axial direction of the plug. In this embodiment, the pre-chamber forming portion 30 is formed as a separate component from the housing 40, and is attached to the housing 40 on the front end side Y1 in the axial direction of the plug by welding. In this embodiment, the housing 40 and the pre-chamber forming portion 30 are formed separately, but instead of this, they may be integrally formed as one component. Also, the auxiliary chamber forming portion 30 may be formed integrally with the cylinder head 101 .

As shown in FIG. 3 , the center electrode 10 is arranged inside the insulator 50 coaxially with the insulator 50 . A tip portion 11 of the center electrode 10 on the tip side Y1 in the axial direction of the plug is exposed in the auxiliary chamber 2 . Inside the sub chamber 2 , a ground electrode 15 is provided on the inner surface of the sub chamber 2 at the bottom portion 31 of the sub chamber forming portion 30 . In this embodiment, the ground electrode 15 is erected on the central axis 10a of the plug, and the tip 16 of the ground electrode 15 faces the tip 11 of the center electrode 10 with a predetermined distance therebetween. A discharge gap G is formed.

As shown in FIGS. 2 and 3 , a plurality of injection holes 35 are formed in the bottom portion 31 of the sub chamber forming portion 30 . In this embodiment, the injection holes 35 include a first injection hole 351 and a second injection hole 352 . As shown in FIG. 3, the first injection hole 351 is formed to penetrate the bottom portion 31 along the center line L1. Here, the center line L1 of the first injection hole 351 is an imaginary line passing through the center of the opening of the first injection hole 351 on the inner side of the sub chamber 2 and the center of the opening on the main combustion chamber 3 side.

As shown in FIGS. 2 and 3, the second injection hole 352 is formed to penetrate the bottom portion 31 along the center line L2. The second injection hole 352 is provided at a position slightly shifted from being symmetrical with the first injection hole 351 with respect to the plug center axis 10a, and the inclination angle of the center line L2 with respect to the plug center axis 10a is is different from the inclination angle of the center line L1 with respect to . The center line L1 and the center line L2 are located at twisted positions and do not intersect each other in three dimensions. In this embodiment, in the state of FIG. 3 viewed from the X1 direction, the position where the center line L1 and the center line L2 overlap indicates the closest position P1 where the distance between the center line L1 and the center line L2 is the smallest. At the closest position P1 in FIG. 3, the center line L1 is three-dimensionally located closer to the paper surface than the center line L2.

Next, the effects of the spark plug 1 of this embodiment will be described in detail.
In the spark plug, since the center lines L1 and L2 of the at least two injection holes 351 and 352 provided in the auxiliary chamber forming portion 30 are twisted with respect to each other, the injection holes 351 and 352 emit light. Flames are configured so that they do not collide with each other. Furthermore, the closest position P1 between the center lines L1 and L2 of the two injection holes 351 and 352 is located inside the main combustion chamber 3. Therefore, the flames ejected from the two injection holes 351 and 352 are brought closer to each other in the main combustion chamber 3, and the flame disturbance increases due to the Coanda effect. As a result, propagation of flame within the main combustion chamber 3 can be accelerated, and ignitability can be improved.

Note that the spark plug 1 of the present embodiment may have a configuration for injecting fuel into the auxiliary chamber 2 . Further, although the spark plug 1 of the present embodiment is configured to generate air discharge in the discharge gap G, it may be configured to generate creeping discharge in the discharge gap G instead. In either case, the same effect as this embodiment can be obtained.

In the first embodiment, the two injection holes 351 and 352 are relatively spaced apart from each other so as to generally sandwich the center electrode 10 when viewed from the axial direction Y of the plug. 4, the two injection holes 351 and 352 are located relatively close to the center electrode 10 so as to be positioned on substantially the same side when viewed from the axial direction Y of the plug. can be placed In this case as well, the center lines L1 and L2 of the two injection holes 351 and 352 are at twisted positions, and their closest positions are located inside the main combustion chamber 3 (not shown). Also in the modified form 1, it is possible to obtain the same effects as in the present embodiment.

As described above, according to the present embodiment, it is possible to provide the spark plug 1 with improved ignitability.

(Embodiment 2)
As shown in FIGS. 5 and 6 , the spark plug 1 of Embodiment 2 includes first injection holes 351 and second injection holes 352 as the plurality of injection holes 35 . As shown in FIG. 5, the center line L1 of the first injection hole 351 and the center line L2 of the second injection hole 352 are parallel when viewed from the plug axial direction Y1 in the plug axial direction Y. As shown in FIG. The distance W between the center line L1 and the center line L2 on the paper surface shown in FIG. 5 can be set as appropriate. is bigger than The opening diameters D1 and D2 indicate the diameters of the openings of the injection holes 35 and 352 on the main combustion chamber 3 side. When viewed from a direction parallel to the center line L2, the size of the opening can be set in a direction perpendicular to the center lines L1 and L2. The opening diameters are D1 and D2.

In the state shown in FIG. 6 as viewed from the X1 direction in the radial direction of the plug shown in FIG. 5, the center line L1 and the center line L2 overlap at a position indicated by P1. Therefore, the center line L1 of the first injection hole 351 and the center line L2 of the second injection hole 352 are at twisted positions. In FIG. 6, the position where the center line L1 and the center line L2 overlap indicates the closest position P1. As shown in FIG. 6 , the closest position P1 is located inside the main combustion chamber 3 . Other configurations are the same as those of the first embodiment, and the same reference numerals as those of the first embodiment are used in the second embodiment, and the description thereof is omitted.

(Evaluation test)
Next, an evaluation test was conducted based on a simulation of gas ejection from the spark plug 1 of the second embodiment.
In the evaluation test, the spark plug 1 of the present embodiment was prepared as Test Example 1 in which the distance W between the center line L1 and the center line L2 on the paper surface shown in FIG. 5 was 6 mm. Further, as Test Example 2, a sample with a distance W of 3 m was prepared. In addition, in Test Examples 1 and 2, the opening diameters D1 and D2 are both 2 mm.
In this evaluation test, the behavior of the gas when the pre-chamber was filled with high-pressure gas at 5 MPa and ejected into the atmospheric pressure environment was investigated as a simulated representation of the behavior of the ejected flame.

As shown in FIGS. 7(a) to 7(d), when comparing Test Example 1 and Test Example 2, the distance W shown in FIGS. 7(a) and 7(b) is 6 mm. On the other hand, in Test Example 2 in which the distance W is 3 mm shown in FIGS. It was confirmed that it became easier to concentrate. Therefore, it is inferred that the ejected flame also exhibits the same behavior.

Next, the effects of the spark plug 1 of Embodiment 2 will be described in detail.
The spark plug 1 of the second embodiment also has the same effects as those of the first embodiment. Furthermore, in the second embodiment, the center line L1 of the first injection hole 351 and the center line L2 of the second injection hole 352 are parallel to each other when viewed from the plug axial direction tip side Y1 in the plug axial direction. . This makes it easier to promote flame turbulence in the radially central region of the main combustion chamber 3, thereby making it easier to improve ignitability.

Further, in Embodiment 2, the distance W between the center lines L1 and L2 of the first injection hole 351 and the second injection hole 352 is the distance W at the closest position P1 between the first injection hole 351 and the second injection hole 352. It is larger than either opening diameter D1 or D2 of the hole 352 . As a result, the flames ejected from the first injection hole 351 and the second injection hole 352 can be prevented from colliding with each other in the main combustion chamber 3, and the airflow formed around the ejected flames can be utilized. As a result, the turbulence of the flame can be further promoted, and the ignitability of the air-fuel mixture in the main combustion chamber 3 can be further improved.

(Embodiment 3)
In Embodiments 1 and 2 described above, the first injection hole 351 and the second injection hole 352 are provided as the plurality of injection holes 35, but the invention is not limited to this, and three or more injection holes 35 may be provided. . As shown in FIG. 8, the spark plug 1 of Embodiment 3 includes three injection holes 35, namely, a first injection hole 351, a second injection hole 352, and a third injection hole 353. As shown in FIG. The center line L1 of the first injection hole 351, the center line L2 of the second injection hole 352, and the center line L3 of the third injection hole 353 are at twisted positions. In the state of FIG. 9 viewed from the X1 direction, the closest position P2 is the position where the center line L2 and the center line L3 overlap. As shown in FIG. 8 , the closest position P2 is located inside the main combustion chamber 3 . Although not shown, the closest position between the center lines L1 and L2 and the closest position between the center lines L3 and L1 are also located within the main combustion chamber 3 . Other configurations are the same as those of the first embodiment, and the same reference numerals as those of the first embodiment are used in the third embodiment, and the description thereof is omitted.

According to the ignition plug 1 of Embodiment 3, the flames ejected from the first injection hole 351, the second injection hole 352, and the third injection hole 353 do not collide with each other, but they approach each other in the main combustion chamber 3. The flame turbulence increases due to the Coanda effect, in which the flames attract each other. As a result, propagation of flame within the main combustion chamber 3 can be promoted, and ignitability within the main combustion chamber 3 can be improved. In the second embodiment, flames ejected from the three injection holes 351 to 353 increase turbulence, so the ignitability in the main combustion chamber 3 can be further improved.

(Embodiment 4)
In the spark plug 1 of Embodiment 4, as shown in FIG. Prepare. The center line L1 of the first injection hole 351, the center line L2 of the second injection hole 352, the center line L3 of the third injection hole 353, and the center line L4 of the fourth injection hole 354 are at twisted positions.

In the state of FIG. 11 viewed from the X1 direction, the position where the center line L1 and the center line L2 overlap indicates the closest position P1 between them. As shown in FIG. 11 , the closest position P1 is located inside the main combustion chamber 3 . Although not shown, the closest position between the center line L1 and the center line L3, the closest position between the center line L1 and the center line L4, the closest position between the center line L2 and the center line L3, the center line L2 and the center The position closest to the line L4 and the position closest to the center line L3 and the center line L4 are also located within the main combustion chamber 3 . Other configurations are the same as those of the first embodiment, and the same reference numerals as those of the first embodiment are given in the fourth embodiment, and the description thereof is omitted.

Also in Embodiment 4, there exists an effect equivalent to this Embodiment 1. FIG. Furthermore, according to the spark plug 1 of the fourth embodiment, the turbulence of the flames ejected from the four injection holes 351 to 354 increases, so the ignitability in the main combustion chamber 3 can be further improved. .

(Embodiment 5)
In the fifth embodiment, as shown in FIGS. 12 and 13, two injection holes 351 and 352 are formed in the side wall 33 of the pre-chamber forming portion 30. As shown in FIGS. The center line L1 of the first injection hole 351 and the center line L2 of the second injection hole 352 are at twisted positions. In the state of FIG. 12 viewed from the X1 direction, the position where the center line L1 and the center line L2 overlap indicates the closest position P1 between them. As shown in FIG. 12 , the closest position P1 is located inside the main combustion chamber 3 . Other configurations are the same as those of the first embodiment, and the same reference numerals as those of the first embodiment are used in the fifth embodiment, and the description thereof is omitted. Also in the fifth embodiment, the same effects as those of the first embodiment are obtained.

The present invention is not limited to the above embodiments, and can be applied to various embodiments without departing from the scope of the invention.

Reference Signs List 1 Spark plug 2 Pre-chamber 3 Main combustion chamber 10 Center electrode 10a Center axis of plug 11 Tip end 30 Pre-chamber forming part 35, 351 to 354, 361 to 364 Injection hole, G... discharge gap, L1 to L4... center line

Claims (4)

A pre-chamber (2) located on the tip side in the axial direction of the plug, a sub-chamber forming portion (30) forming the sub-chamber (2), and a center electrode (10) having a tip portion (11) located in the sub-chamber. and
A plurality of injection holes (35) are formed in the sub-chamber forming portion for communicating the sub-chamber with the main combustion chamber (3),
At least two injection holes (351, 352) out of the plurality of injection holes have their respective center lines (L1, L2) at twisted positions, and at the closest position where the distance between the center lines is minimum. is located in said main combustion chamber. The plurality of injection holes includes a first injection hole (351), a second injection hole (352), and a third injection hole (353) whose respective center lines (L1, L2, L3) are at twisted positions. ,
the closest position between the center line of the first injection hole and the center line of the second injection hole; the closest position between the center line of the second injection hole and the center line of the third injection hole; 2. The spark plug according to claim 1, wherein the closest positions of the center line of the third injection hole and the center line of the first injection hole are both located within the main combustion chamber. 3. The spark plug according to claim 1, wherein center lines of two injection holes included in the plurality of injection holes are parallel to each other when viewed from the plug axial direction tip side in the plug axial direction. 4. The spark plug according to claim 3, wherein a distance between center lines of said two injection holes is larger than an opening diameter of either of said two injection holes at said closest position of both.

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