JP7365932B2 - Method of manufacturing spark plugs for internal combustion engines - Google Patents

Description

The present invention relates to a method of manufacturing a spark plug for an internal combustion engine.

The spark plug described in Patent Document 1 has a subchamber at its tip. Further, an opening is provided on the tip side of the sub-chamber to communicate the sub-chamber and the main combustion chamber. Then, a discharge gap is formed between the inner peripheral end of the opening and the center electrode.

JP2016-95986A

However, in such a spark plug, the size of the discharge gap is determined by the positional relationship between the inner peripheral end of the opening and the tip of the center electrode. Therefore, in manufacturing such a spark plug, a method that can control the size of the discharge gap with high precision is desired.

The present invention has been made in view of this problem, and it is an object of the present invention to provide a method of manufacturing a spark plug for an internal combustion engine that can control the size of the discharge gap with high precision.

One aspect of the present invention is a method of manufacturing a spark plug (1) for an internal combustion engine, comprising:
The above spark plug is
a cylindrical insulator (3);
a center electrode (4) held inside the insulator and protruding toward the tip side of the insulator;
a cylindrical housing (2) that holds the insulator on the inner circumferential side;
a cover part (5) provided at the tip of the housing so as to cover the center electrode,
The cover part is formed with a through hole (51) that communicates the auxiliary chamber (50) formed inside the cover part to the outside,
A ground electrode (6) forming a discharge gap (G) with the center electrode is provided at the inner peripheral end (511) of the through hole,
In manufacturing the above spark plug,
A method of manufacturing a spark plug for an internal combustion engine includes forming the discharge gap to a predetermined size in a state in which the housing, the insulator, the center electrode, and the cover are integrated.

In the method for manufacturing a spark plug for an internal combustion engine, a discharge gap is formed to a predetermined size in a state where the housing, the insulator, the center electrode, and the cover are integrated. Therefore, the size of the discharge gap can be controlled with high precision.

As described above, according to the above aspect, it is possible to provide a method for manufacturing a spark plug for an internal combustion engine, in which the size of the discharge gap can be managed with high precision.
Note that the numerals in parentheses described in the claims and means for solving the problem indicate correspondence with specific means described in the embodiments described later, and do not limit the technical scope of the present invention. It's not a thing.

1 is a cross-sectional view of a portion of a spark plug in Embodiment 1. FIG. II view of FIG. 1. FIG. 2 is an explanatory diagram of the spark plug manufacturing method in Embodiment 1, and is a cross-sectional explanatory diagram showing a state immediately before cutting. FIG. 3 is an enlarged cross-sectional explanatory diagram of the temporary hole and the tip of the center electrode in Embodiment 1. V view of FIG. 4. FIG. 3 is an enlarged cross-sectional explanatory diagram showing a state in which the drill is aligned with the center electrode in Embodiment 1. A sectional view taken along the line VII-VII in FIG. 6. FIG. 2 is an explanatory diagram of the spark plug manufacturing method in Embodiment 1, and is a cross-sectional explanatory diagram showing a state during cutting. FIG. 2 is an enlarged cross-sectional explanatory diagram showing a state during cutting in Embodiment 1. FIG. FIG. 2 is an enlarged cross-sectional explanatory diagram showing a state after cutting in Embodiment 1. FIG. XI view of FIG. 10. 1 is a cross-sectional view of a portion of a spark plug depicting a plurality of nozzle holes in Embodiment 1. FIG. FIG. 7 is an enlarged cross-sectional explanatory diagram showing a state in which the drill is aligned with the center electrode in Embodiment 2. A sectional view taken along the line XIV-XIV in FIG. 13. FIG. 7 is an enlarged cross-sectional explanatory diagram showing a state after cutting in Embodiment 2. XVI view of FIG. 15. FIG. 7 is an explanatory diagram of a method for manufacturing a spark plug using electric discharge machining in Embodiment 3. FIG. 7 is an explanatory diagram of a method for manufacturing a spark plug using laser processing in Embodiment 3. FIG. 7 is an explanatory diagram of a spark plug manufacturing method in Embodiment 4, and is a cross-sectional explanatory diagram showing a state immediately before cutting. FIG. 7 is an explanatory diagram of a spark plug manufacturing method in Embodiment 4, and is a cross-sectional explanatory diagram showing a state during cutting. FIG. 4 is a cross-sectional view of a portion of a spark plug in Embodiment 4. FIG. 7 is an explanatory diagram of a spark plug manufacturing method in Embodiment 5, and is a cross-sectional explanatory diagram showing a state during cutting. FIG. 7 is an explanatory diagram of a spark plug manufacturing method in Embodiment 5, and is a cross-sectional explanatory diagram showing a state immediately after cutting. FIG. 7 is an explanatory diagram of a spark plug manufacturing method in Embodiment 5, and is a cross-sectional explanatory diagram showing a state immediately before joining a noble metal tip. 5 is a cross-sectional view of a portion of a spark plug in Embodiment 5. FIG. FIG. 6 is a cross-sectional view of a portion of the assembly in Embodiment 6. XXVII view of FIG. 26. FIG. 7 is a cross-sectional explanatory diagram of position measurement of the tip of the center electrode 4 in Embodiment 6. FIG. 7 is an explanatory cross-sectional view showing a state immediately before joining electrode members in Embodiment 6; FIG. 6 is a cross-sectional view of a portion of a spark plug in Embodiment 6. XXXI view of FIG. 30. FIG. 7 is a cross-sectional view of a portion of the assembly in Embodiment 7. FIG. 7 is a cross-sectional view of a portion of a spark plug in Embodiment 7. FIG. 7 is an explanatory diagram showing an example of a state in which the assembly is viewed from the distal end side in Embodiment 7. FIG. 7 is an explanatory diagram showing another example of the assembly as viewed from the distal end side in Embodiment 7; FIG. 35 is an explanatory diagram showing a state in which an electrode member is joined to the assembly in the state shown in FIG. 34; FIG. 36 is an explanatory diagram showing a state in which an electrode member is joined to the assembly in the state shown in FIG. 35; FIG. 8 is a cross-sectional view of a portion of a spark plug in Embodiment 8. XXXIX view of FIG. 38. FIG. 8 is a cross-sectional view of a portion of the spark plug in another state in Embodiment 8. FIG. 9 is a cross-sectional view of a portion of a spark plug provided with an electrode member having a long axial length in Embodiment 8.

(Embodiment 1)
An embodiment of a method for manufacturing a spark plug for an internal combustion engine will be described with reference to FIGS. 1 to 11.
The spark plug 1 manufactured by the manufacturing method of this embodiment includes a cylindrical insulator 3, a center electrode 4, a cylindrical housing 2, and a cover portion 5, as shown in FIGS. 1 and 2. The center electrode 4 is held inside the insulator 3 and protrudes toward the tip side of the insulator 3. The housing 2 holds the insulator 3 on the inner circumferential side. The cover part 5 is provided at the tip of the housing 2 so as to cover the center electrode 4.

The cover part 5 is formed with a through hole 51 that allows a subchamber 50 formed inside the cover part 5 to communicate with the outside. A ground electrode 6 that forms a discharge gap G between it and the center electrode 4 is provided at the inner circumferential end 511 of the through hole 51 . Note that in this embodiment, the ground electrode 6 is constituted by the inner peripheral end portion 511 of the through hole 51 in the cover portion 5.

In manufacturing the spark plug 1, as shown in FIGS. 3 and 8, a discharge gap G is formed to a predetermined size in a state where the housing 2, the insulator 3, the center electrode 4, and the cover part 5 are integrated. do. After the housing 2, the insulator 3, the center electrode 4, and the cover part 5 are integrated, a discharge gap G is formed.

As shown in FIG. 1, in this embodiment, the center electrode 4 protrudes from the tip of the insulator 3 toward the tip in the plug axial direction Z. The protruding length L1 of the center electrode 4 from the insulator 3 can be, for example, about 1 to 3 times the radius r1 of the subchamber 50. More preferably, the protrusion length L1 can be about 1.5 to 2 times the radius r1 of the subchamber 50. Note that the radius r1 can be defined by the radius of the cross section of the sub chamber 50 that has the largest radius among the cross sections of the sub chamber 50 perpendicular to the plug axial direction Z. Further, the center electrode 4 includes an electrode base material 401 and an extending member 402 joined to the tip of the electrode base material 401. The extending member 402 has a cylindrical shape. The length of the extension member 402 can be, for example, 80% or more of the protrusion length of the center electrode 4 described above.

Note that the center electrode 4 can also be configured without the extending member 402. That is, the center electrode 4 can also be configured by extending the electrode base material 401 of a single member toward the tip side.
In this specification, the plug axial direction Z is also appropriately referred to as the Z direction. Further, in the Z direction, the side where the spark plug 1 is inserted into the main combustion chamber is called the tip side, and the opposite side is called the base side.

Further, in this embodiment, the cover portion 5 is manufactured as a separate component from the housing 2. A cover part 5 is fixed to the tip of the housing 2. The cover portion 5 and the housing 2 are joined by, for example, welding. Note that the cover part 5 and the housing 2 can also be manufactured as an integral part.

The cover portion 5 includes a cylindrical side circumferential portion 501 that stands upright in the axial direction Z, and a bottom wall portion 502 that is disposed on the tip side of the side circumferential portion 501. A through hole 51 is formed approximately in the center of the bottom wall portion 502. In addition to the through-holes 51, the cover portion 5 can also be provided with nozzle holes 53 (see FIG. 12). A subchamber 50 is formed inside the cover part 5.

The distal end portion 41 of the center electrode 4 is located closer to the proximal end than the through hole 51 . Therefore, the entire extension member 402 is disposed within the subchamber 50. The discharge gap G is formed between the outer peripheral corner of the tip 41 of the center electrode 4 and the base end of the inner peripheral end 511 of the through hole 51 in the cover part 5. The size of the discharge gap G can be, for example, 0.2 to 1.2 mm. In this embodiment, the discharge gap G is formed over the entire outer periphery of the tip portion 41 of the center electrode 4. That is, when viewed from the axial direction Z, the tip portion 41 of the center electrode 4 and the through hole 51 are formed substantially concentrically.

Note that a tip concave surface 423 is formed on the tip portion 41 of the center electrode 4 . The tip concave surface 423 is a conical concave surface corresponding to the shape of the front end portion 72 of the drill 7 (see FIGS. 9 and 10). However, by changing the shape of the front end portion 72 of the drill 7 or changing the processing method, the tip portion 41 may be shaped without the tip concave surface 423.

In this embodiment, as shown in FIGS. 3 to 11, the inner peripheral end 511 of the through hole 51 and the tip 41 of the center electrode 4 are processed to form the discharge gap G to a predetermined size. Further, while cutting the inner circumferential end 511 of the through hole 51, the tip 41 of the center electrode 4 is cut using one processing tool 7.

More specifically, the processing tool 7 is a drill. As shown in FIG. 9, the inner peripheral end 511 of the through hole 51 is cut using the side portion 71 of the drill 7. The front end 41 of the center electrode 4 is cut using the front end 72 of the drill 7 .

As shown in FIGS. 3 to 5, a temporary hole 52 is formed in the cover portion 5 before the inner circumferential end 511 of the through hole 51 is processed. Further, in this state, as shown in FIG. 5, the tip portion 41 of the center electrode 4 is accommodated within the temporary hole 52 when viewed from the direction in which the temporary hole 52 opens. From this state, the temporary hole 52 is expanded as shown in FIGS. 6 to 10. Thereby, as shown in FIGS. 10 and 11, the ground electrode 6, which is also the inner peripheral end 511 of the through hole 51, and the tip 41 of the center electrode 4 are formed in a predetermined positional relationship. Therefore, the discharge gap G is formed to a predetermined size.

More specifically, processing of the through hole 51 and the center electrode 4 using the drill 7 can be performed, for example, in the following procedure.
First, as shown in FIG. 3, the housing 2, the insulator 3, the center electrode 4, and the cover part 5 are assembled and integrated. This integrated body will be referred to as an assembly 11 below. Note that, before integration, a temporary hole 52 is formed approximately in the center of the bottom wall portion 502 of the cover portion 5.

As shown in FIGS. 5 and 11, the diameter of the temporary hole 52 is smaller than the diameter of the through hole 51 that will be formed later, and larger than the diameter of the tip 41 of the center electrode 4. As shown in FIGS. 3 and 4, the tip 41 of the center electrode 4 before being cut by the drill 7 is inserted into the temporary hole 52. At this point, the tip 41 of the center electrode 4 is located at the same position in the Z direction as the tip of the temporary hole 52. However, the distal end portion 41 may protrude further toward the distal end than the temporary hole 52. Further, the distal end portion 41 can be arranged closer to the proximal end than the distal end of the temporary hole 52. Further, depending on the size of the discharge gap G to be finally obtained, the distal end portion 41 may be provided closer to the proximal end than the temporary hole 52, that is, within the auxiliary chamber 50.

The temporary hole 52 is formed so that its central axis coincides with the tip 41 of the center electrode 4 as much as possible. However, in reality, due to dimensional tolerances of each component, assembly tolerances, etc., the center electrode 4 and the temporary hole 52 are arranged with their central axes shifted from each other, as shown in FIGS. 4 and 5. Sometimes. That is, for example, due to slight deviations in the joining position of the extension member 402 to the electrode base material 401, the inclination of the extension member 402, the joining position of the cover part 5 to the housing 2, etc., the tip part 41 of the center electrode 4 and the temporary hole may 52 may be sufficiently misaligned.

As described above, before processing the through hole 51 and the tip 41 of the center electrode 4, as shown in FIG. Form it. From this state, as shown in FIGS. 6 to 9, the vicinity of the temporary hole 52 in the cover portion 5 is cut from the tip side using the drill 7, and the tip portion 41 of the center electrode 4 is also cut.

At this time, the center axis of the drill 7 is made to coincide with the center axis of the tip portion 41 of the center electrode 4. As shown in FIGS. 4 to 6, a center recess 42 is formed in the tip 41 of the center electrode 4. As shown in FIGS. The central recess 42 has a conical shape, and the apex 421 of this conical shape is located at the central axis of the tip 41 of the center electrode 4 . Then, the drill 7 is gradually advanced. That is, while the drill 7 is being gradually fed toward the base end of the spark plug 1, the cover portion 5 and the center electrode 4 are simultaneously machined.

The feed amount of the drill 7 is controlled to a predetermined feed amount. The predetermined feed amount is a value that allows a desired discharge gap G to be obtained. This feed amount is set in advance. The amount of feed can be, for example, the forward dimension from the position of the tip of the cover part 5 as a reference.

Here, the diameter of the through hole 51 is specified based on the diameter of the drill 7. Therefore, the diameter of the through hole 51 can be known in advance. Further, as described above, since the center axis of the drill 7 is made to coincide with the center axis of the tip portion 41 of the center electrode 4, the resulting through hole 51 is concentric with the center electrode 4. Therefore, once the position of the tip 41 of the center electrode 4 in the axial direction Z is determined, the size of the discharge gap G is determined.

Therefore, the feed amount of the drill 7 is set so that the tip portion 41 of the center electrode 4 is located at a position where a discharge gap G of a desired size is obtained. Then, while feeding the drill 7 according to the set value, the tip portion 41 of the center electrode 4 and the inner peripheral end portion 511 of the through hole 51 are cut. Through the above steps, a desired discharge gap G can be formed.
Note that the tip end portion 41 of the center electrode 4 is formed with a conical tip concave surface 423 corresponding to the shape of the front end portion 72 of the drill 7, as shown in FIGS. 9 and 10.

Next, the effects of this embodiment will be explained.
In the method of manufacturing a spark plug for an internal combustion engine of this embodiment, a discharge gap G is formed to a predetermined size in a state where the housing 2, the insulator 3, the center electrode 4, and the cover portion 5 are integrated. Therefore, the size of the discharge gap G can be controlled with high precision.

Further, by processing the inner circumferential end 511 of the through hole 51 and the tip 41 of the center electrode 4, the discharge gap G is formed to a predetermined size. Therefore, it is easy to finely adjust the size of the discharge gap G.

Further, while cutting the inner circumferential end 511 of the through hole 51, the tip 41 of the center electrode 4 is cut using one processing tool 7. Thereby, the accuracy of the relative position between the inner peripheral end portion 511 and the tip portion 41 can be easily improved. Therefore, it is easier to control the size of the discharge gap G.

The side portion 71 of the drill 7 is used to cut the inner circumferential end 511 of the through hole 51, and the front end 72 of the drill 7 is used to cut the tip portion 41 of the center electrode 4. Thereby, the processing accuracy of the through hole 51 and the tip portion 41 of the center electrode 4 can be easily improved.

In the state before processing, the tip portion 41 of the center electrode 4 is accommodated in the temporary hole 52 when viewed from the opening direction of the temporary hole 52 . Then, the temporary hole 52 is processed to be expanded. Thereby, the through hole 51 and the tip 41 of the center electrode 4 can be easily processed while checking the position of the tip 41 of the center electrode 4.

As described above, according to the present embodiment, it is possible to provide a method for manufacturing a spark plug for an internal combustion engine that can control the size of the discharge gap with high precision.

In order to align the center axis of the tip 41 of the center electrode 4 and the center axis of the drill 7, for example, in the state of the assembly 11, use an optical measuring device such as a camera to align the tip 41 of the center electrode 4 with the center axis of the drill 7. It is possible to measure the position of That is, a camera or the like is used to take an image of the tip 41 of the center electrode 4 from the tip side in the axial direction Z through the temporary hole 52, and measure its position. The position of the drill 7 is adjusted to match the position of the tip 41 of the center electrode 4 obtained by measurement. Thereby, the tip portion 41 of the center electrode 4 and the through hole 51 can be cut with higher precision.

(Embodiment 2)
In this embodiment, a case will be described in which a portion of the temporary hole 52 remains even after the through hole 51 is formed, as shown in FIGS. 13 to 16.
In such a configuration, the difference between the diameter of the tip 41 of the center electrode 4 and the diameter of the temporary hole 52 is large to some extent, the difference between the diameter of the through hole 51 and the diameter of the temporary hole 52 is small to some extent, and the diameter of the assembly 11 is small. This can occur when the central axis of the temporary hole 52 and the central axis of the tip portion 41 of the center electrode 4 are largely deviated from each other.

In this case as well, the method of processing the through hole 51 and the center electrode 4 using the drill 7 can be performed in substantially the same manner as in the first embodiment. That is, as shown in FIG. 13, in the state of the assembly 11, the tip portion 41 of the center electrode 4 is inserted into the through hole 51 of the cover portion 5. At this time, as shown in FIG. 14, the tip portion 41 of the center electrode 4 is largely eccentric with respect to the through hole 51 of the cover portion 5. The center axis of the drill 7 is made to coincide with the center axis of the tip portion 41 of the center electrode 4 in this assembly 11 . However, as shown in FIG. 14, a portion of the temporary hole 52 protrudes outward from the side portion 71 of the drill 7 when viewed from the axial direction Z. This point is different from the first embodiment. Then, while gradually advancing the drill 7 to a predetermined feed amount, the tip 41 of the center electrode 4 is being cut, and the inner peripheral end 511 of the through hole 51 is being cut.

As a result, as shown in FIGS. 15 and 16, the tip portion 41 of the center electrode 4 is formed within the subchamber 50, and a through hole 51 is formed in the cover portion 5. Here, the through hole 51 has a shape in which a contour 512 obtained by cutting with the drill 7 and a contour 522 of the temporary hole 52 are connected. Therefore, the inner circumferential end 511 of the resulting through hole 51 is not entirely concentric with the tip 41 of the center electrode 4, and is not circular in the first place.

However, in a part of the inner peripheral end 511, that is, in the above-mentioned outline 512, the distance between the tip 41 of the center electrode 4 and the inner peripheral end 511 becomes the shortest, and a predetermined distance is maintained. It will be. That is, a predetermined discharge gap G is formed between the tip portion 41 of the center electrode 4 and a portion of the inner peripheral end portion 511. In other words, a portion of the inner circumferential end 511 having the outline 512 becomes the ground electrode 6 .

The rest is the same as in the first embodiment. Note that among the symbols used in the second embodiment and subsequent embodiments, the same symbols as those used in the previously described embodiments represent the same components as those in the previously described embodiments, unless otherwise specified.

Even when the tip 41 of the center electrode 4 is largely deviated from the temporary hole 52 as in this embodiment, a highly accurate discharge gap G can be formed. That is, even if, for example, the extending member 402 of the center electrode 4 is tilted and the position of the tip portion 41 is deviated from the central axis of the plug, the discharge gap G can be formed with high accuracy.
Other than that, it has the same effects as Embodiment 1.

(Embodiment 3)
In this embodiment, as shown in FIGS. 17 and 18, the tip portion 41 of the center electrode 4 and the through hole 51 of the cover portion 5 are processed by means other than a drill.
That is, the machining of the tip portion 41 of the center electrode 4 and the through hole 51 of the cover portion 5 can also be performed by electric discharge machining, for example, as shown in FIG. In this case, for example, the tip portion 41 of the center electrode 4 and the through hole 51 may be formed by adjusting the position of the discharge electrode 73 with respect to the center electrode 4 and the cover part 5, the discharge energy, the discharge time, etc. I can do it.

Further, the processing of the tip portion 41 of the center electrode 4 and the through hole 51 of the cover portion 5 can also be performed by laser processing, for example, as shown in FIG. 18. In this case, the tip 41 of the center electrode 4 and the through hole 51 are formed by adjusting the position of the laser processing head 74 with respect to the center electrode 4 and the cover part 5, the irradiation energy of the laser beam, the irradiation time, etc. be able to.
The rest is the same as in Embodiment 1, and the same effects are achieved.

(Embodiment 4)
In this embodiment, as shown in FIGS. 19 to 21, the tip portion 41 of the center electrode 4 is oriented to intersect with the Z direction.
That is, for example, as shown in FIG. 21, the center electrode 4 is provided with a bent portion 43 such that the tip portion 41 is inclined with respect to the Z direction. The tip portion 41 of the center electrode 4 faces the corner between the bottom wall portion 502 and the side peripheral portion 501 of the cover portion 5. A through hole 51 is formed at a corner of this cover portion 5.

When manufacturing such a spark plug 1, for example, as shown in FIG. 19, first, an assembly 11 having temporary holes 52 in the corners of the cover portion 5 is prepared. In the assembly 11, the tip portion 41 of the center electrode 4 is inserted into the temporary hole 52.
Next, as shown in FIG. 20, the drill 7 is placed to face the assembly 11 from the direction facing the tip 41 of the center electrode 4. That is, the front end 72 of the drill 7 is directed toward the corner of the cover part 5 from the oblique tip side. From this state, while gradually advancing the drill 7, the corners of the cover portion 5 are cut and the tip portion 41 of the center electrode 4 is cut.

By advancing this drill 7 by a predetermined feed amount, a predetermined discharge gap G is formed as shown in FIG. 21.
The rest is the same as in the first embodiment.

In the case of this embodiment, the discharge gap G can be formed with high precision at a position away from the central axis of the plug.
The rest is the same as in the first embodiment.

(Embodiment 5)
In this embodiment, a noble metal tip 44 is provided at the tip 41 of the center electrode 4, as shown in FIGS. 22 to 25.
That is, after forming the distal end concave surface 423 by processing the distal end portion 41 of the center electrode 4, the noble metal tip 44 having the proximal convex surface 441 that fits into the distal concave surface 423 is bonded.

In this embodiment, as in the first embodiment, first, as shown in FIGS. 22 and 23, the through hole 51 of the cover part 5 is cut on the assembly 11 (see FIG. 3), and the center The tip portion 41 of the electrode 4 is cut. However, in the case of this embodiment, the cutting process of the distal end portion 41 of the center electrode 4 is performed closer to the proximal end side, taking into account the length in the Z direction of the noble metal tip 44 to be joined. That is, as will be described later, in a state where the noble metal tip 44 is arranged at the tip 41, the tip 41 of the center electrode 4 (in this case, the extension member is 402) is cut.

As a result, as shown in FIG. 23, the tip portion 41 of the center electrode 4 is processed and a through hole 51 is formed. As described in the first embodiment, by cutting the tip 41 of the center electrode 4 with the drill 7, the tip 41 of the center electrode 4 has a conical shape corresponding to the shape of the front end 72 of the drill 7. A concave tip surface 423 having a shape is formed.

On the other hand, as shown in FIG. 24, a noble metal tip 44 having a proximal convex surface 441 formed in a portion thereof is prepared. The noble metal tip 44 can be made of, for example, platinum alloy, iridium alloy, or the like. The proximal convex surface 441 has substantially the same shape as the distal concave surface 423 of the center electrode 4, as described above. Note that the tip concave surface 423 can be determined in advance from, for example, the shape of the drill 7.

Then, the proximal convex surface 441 of the noble metal tip 44 is fitted into the concave distal end surface 423 of the center electrode 4 obtained by cutting as described above, and is bonded (see FIG. 25). That is, the noble metal tip 44 is bonded to the tip of the extending member 402 of the center electrode 4 . The noble metal tip 44 can be joined to the center electrode 4 by, for example, welding.

In a state in which the noble metal tip 44 is provided at the distal end portion 41, a discharge gap G is formed between the noble metal tip 44 and the inner peripheral end portion 511 of the through hole 51. In the above-described cutting process (see FIG. 22), the feed amount of the drill 7 is controlled so that the discharge gap G has a predetermined size.
The rest is the same as in the first embodiment.

According to this embodiment, even in the spark plug 1 in which the noble metal tip 44 is disposed at the tip 41 of the center electrode 4, the size of the discharge gap G can be managed with high precision. Other than that, it has the same effects as Embodiment 1.

(Embodiment 6)
As shown in FIGS. 26 to 31, this embodiment is a spark plug 1 for an internal combustion engine in which an electrode member 61 is joined to an inner peripheral end 511 of a through hole 51 so that a discharge gap G has a predetermined size. This is the form of the manufacturing method.
The electrode member 61 is joined to a portion of the inner peripheral end portion 511 in the circumferential direction. Then, the size of the discharge gap G is adjusted depending on the joining position in the circumferential direction.

That is, as shown in FIG. 26, before joining the electrode member 61, an assembly 110 is produced in which the housing 2, the insulator 3, the center electrode 4, and the cover part 5 are integrated. A through hole 51 is formed in the bottom wall portion 502 of the cover portion 5 in advance. Furthermore, the distal end portion 41 of the center electrode 4 is disposed closer to the proximal end than the through hole 51 . The tip portion 41 of the center electrode 4 is visible through the through hole 51 from the tip side in the Z direction, as shown in FIG.

As shown in FIG. 28, in this assembly 110, the position of the tip 41 of the center electrode 4 with respect to the through hole 51 is measured from the tip side in the Z direction using an optical measuring means such as a laser measuring device 81. That is, as shown in FIG. 27, the position of the tip 41 of the center electrode 4 with respect to the through hole 51 when projected in the Z direction is measured. Here, the center axes of the tip portion 41 of the center electrode 4 and the through hole 51 may be slightly shifted from each other. Then, when viewed from the Z direction, the distance between the tip 41 of the center electrode 4 and the electrode member 61 changes depending on the joining position of the electrode member 61 in the circumferential direction at the inner peripheral end 511 of the through hole 51. becomes.

Therefore, in consideration of the position of the tip portion 41 of the center electrode 4 with respect to the through hole 51 measured as described above, an appropriate circumferential position as the joining position of the electrode member 61 is calculated. Then, the electrode member 61 is joined to that position in the circumferential direction (see FIGS. 29 to 31).

For joining, for example, as shown in FIG. 29, with the electrode member 61 mounted on the arrangement jig 82, the electrode member 61 is inserted into the through hole 51 together with a part of the arrangement jig 82. At this time, the placement jig 82 is inserted until the front end surface 821 comes into contact with the tip 41 of the center electrode 4 . Here, the front end surface 821 is made flush with the proximal end surface 611 of the electrode member 61 so that the Z direction positional relationship between the front end surface 821 and the proximal end surface 611 is a predetermined positional relationship. Keep it on board.

Then, in a state where the front end surface 821 of the arrangement jig 82 is in contact with the distal end portion 41 of the center electrode 4, the positional relationship in the Z direction between the proximal end surface 611 of the electrode member 61 and the distal end portion 41 of the center electrode 4 is , determined by a specific positional relationship. That is, for example, the base end surface 611 of the electrode member 61 and the distal end portion 41 of the center electrode 4 are arranged at the same position in the Z direction.

Therefore, once the distance between the tip 41 of the center electrode 4 and the electrode member 61 in the radial direction is determined, the size of the discharge gap G is determined. As the distance between the tip portion 41 and the electrode member 61 in the radial direction (see G1 in FIG. 31), the circumferential position where the electrode member 61 can be joined to the inner peripheral end 511 of the through hole 51 while maintaining an appropriate distance is determined. calculate. At that circumferential position, the electrode member 61 is arranged at the inner circumferential end 511 . Then, at this position, the electrode member 61 is joined to the inner peripheral end portion 511 by welding or the like.
Through the above steps, as shown in FIG. 30, a spark plug 1 in which a discharge gap G of a desired size is provided between the electrode member 61 and the tip portion 41 of the center electrode 4 is obtained.
The rest is the same as in the first embodiment.

In this embodiment, the electrode member 61 can be joined to an appropriate position in the circumferential direction of the inner circumferential end 511 of the through hole 51 . Thereby, the discharge gap G can be finely adjusted with high precision.
Other than that, it has the same effects as Embodiment 1.

In the spark plug 1 obtained by the manufacturing method of this embodiment, the electrode member 61 joined to the inner peripheral end 511 of the through hole 51 constitutes the ground electrode 6. The same applies to the spark plug 1 obtained in Embodiment 7 and Embodiment 8, which will be described later.

(Embodiment 7)
In this embodiment, as shown in FIGS. 32 to 37, the size of the discharge gap G is adjusted by the amount of protrusion of the inner end of the electrode member 61 that protrudes inward from the inner circumferential end 511. Also in this embodiment, as shown in FIG. 33, the electrode member 61 is joined to a part of the inner peripheral end portion 511 in the circumferential direction.

In the manufacturing method of this embodiment, first, as shown in FIG. 32, before joining the electrode member 61, an assembly 110 in which the housing 2, the insulator 3, the center electrode 4, and the cover part 5 are integrated is assembled. Create. In this embodiment, the tip portion 41 of the center electrode 4 is inserted into the through hole 51. Furthermore, a notch groove 54 connected to the through hole 51 is formed in the cover portion 5 . The notch groove 54 is provided on the tip side surface of the bottom wall portion 502 of the cover portion 5. Further, an electrode member 61 can be disposed in this notch groove 54 as shown in FIG. 33.

Then, before joining, the electrode member 61 can be placed in the notch groove 54 in a state where the electrode member 61 can slide in the direction of advancing and retracting with respect to the center of the through hole 51.

In this state, the position of the tip portion 41 of the center electrode 4 with respect to the through hole 51 and the notch groove 54 is measured from the tip side in the Z direction using an optical measuring means such as a laser measuring device or a camera. As a result, for example, as shown in FIG. 34, the tip portion 41 of the center electrode 4 may be displaced to the side far from the notch groove 54 in the through hole 51, or, for example, as shown in FIG. It can be seen that the tip portion 41 of the center electrode 4 is shifted toward the side closer to the groove 54.

Depending on the position of the tip 41 of the center electrode 4 with respect to the through hole 51 and the notch 54, the electrode member 61 is moved forward or backward along the notch 54, and the front end 612 of the electrode member 61 is moved forward or backward along the notch 54. Adjust the position. That is, when the tip portion 41 of the center electrode 4 is shifted to the side far from the notch groove 54 in the through hole 51, the electrode member 61 is placed in an advanced state as shown in FIG. On the other hand, if the tip portion 41 of the center electrode 4 is shifted to the side closer to the notch groove 54 in the through hole 51, the electrode member 61 is placed in a retracted state as shown in FIG. In this way, the distance between the tip 41 of the center electrode 4 and the front end 612 of the electrode member 61 is adjusted to a predetermined distance.

Then, with the electrode member 61 positioned at the predetermined position, the electrode member 61 is joined to the cover part 5 at the notch groove 54 by welding or the like.
Through the above steps, as shown in FIG. 33, a spark plug 1 in which a discharge gap G of a desired size is provided between the electrode member 61 and the tip portion 41 of the center electrode 4 is obtained.
The rest is the same as in the sixth embodiment.

In this embodiment, as described above, the amount of protrusion of the inner end of the electrode member 61 can be adjusted and joined. Thereby, the discharge gap G can be finely adjusted with high precision.
In addition, it has the same effects as the sixth embodiment.

(Embodiment 8)
In this embodiment, as shown in FIGS. 38 to 41, a cylindrical electrode member 61 is joined to an inner peripheral end 511 of a through hole 51 of a cover part 5.
In this embodiment, as shown in FIGS. 38 and 39, the electrode member 61 has a cylindrical shape. Then, the electrode member 61 is joined so as to protrude from the inner circumferential end 511 of the through hole 51 toward the base end side in the Z direction. That is, the electrode member 61 is made to protrude into the subchamber 50 .

Also in this embodiment, as in the sixth embodiment (see FIG. 26), before joining the electrode member 61, an assembly 110 is assembled in which the housing 2, the insulator 3, the center electrode 4, and the cover portion 5 are integrated. Create. In this assembly 110, the position of the tip 41 of the center electrode 4 with respect to the through hole 51 is measured from the tip side in the Z direction using an optical measuring means such as a laser measuring device 81 (see FIG. 28).

Then, the amount of protrusion of the electrode member 61 into the auxiliary chamber 50 is calculated in consideration of the measured position of the tip portion 41 of the center electrode 4 with respect to the through hole 51 . Then, the electrode member 61 is joined at a position corresponding to the amount of protrusion. That is, the electrode member 61 is attached to the inner peripheral end 511 at a position such that a discharge gap G of an appropriate size is formed between the base end 614 of the electrode member 61 and the distal end 41 of the center electrode 4. Arrange.

In the case of the manufacturing method of this embodiment, the amount of protrusion of the electrode member 61 into the subchamber is changed depending on the position of the tip portion 41 of the center electrode 4. Therefore, for example, depending on the position of the tip 41 of the center electrode 4, the tip 613 of the electrode member 61 may be at the same position in the Z direction as the tip surface of the cover part 5 as shown in FIG. As shown in FIG. Further, as shown in FIG. 41, it is also possible to intentionally make the length of the electrode member 61 in the Z direction longer so that the electrode member 61 protrudes further toward the distal end side than the distal end surface of the cover portion 5. In this case, the amount of protrusion of the electrode member 61 from the cover portion 5 toward the tip side changes depending on the position of the tip portion 41 of the center electrode 4.
The rest is the same as in the sixth embodiment.

Also in this embodiment, the discharge gap G can be finely adjusted with high precision. In addition, by deliberately making the tip of the center electrode 4 protrude toward the tip, the position of the starting point of the spark discharge can be easily moved toward the tip. As a result, it is possible to obtain a structure that easily improves ignition performance in the main combustion chamber.
In addition, it has the same effects as the sixth embodiment.

The present invention is not limited to the above-mentioned embodiments, but can be applied to various embodiments without departing from the gist thereof.

1 Spark plug for internal combustion engine 2 Housing 3 Insulator 4 Center electrode 41 Tip (of center electrode) 5 Cover portion 51 Through hole 511 Inner peripheral end 6 Ground electrode G Discharge gap

Claims (10)

A method of manufacturing a spark plug (1) for an internal combustion engine, the method comprising:
The above spark plug is
a cylindrical insulator (3);
a center electrode (4) held inside the insulator and protruding toward the tip side of the insulator;
a cylindrical housing (2) that holds the insulator on the inner circumferential side;
a cover part (5) provided at the tip of the housing so as to cover the center electrode,
The cover part is formed with a through hole (51) that communicates the auxiliary chamber (50) formed inside the cover part to the outside,
A ground electrode (6) forming a discharge gap (G) with the center electrode is provided at the inner peripheral end (511) of the through hole,
In manufacturing the above spark plug,
A method of manufacturing a spark plug for an internal combustion engine, comprising forming the discharge gap to a predetermined size in a state in which the housing, the insulator, the center electrode, and the cover are integrated. 2. The method of manufacturing a spark plug for an internal combustion engine according to claim 1, wherein the discharge gap is formed to a predetermined size by machining the inner circumferential end of the through hole and the tip of the center electrode. The method for manufacturing a spark plug for an internal combustion engine according to claim 2, wherein the inner peripheral end of the through hole is cut and the tip of the center electrode is cut using one processing tool (7). . The processing tool is a drill, and the side part (71) of the drill cuts the inner circumferential end of the through hole, and the front end (72) of the drill cuts the tip of the center electrode. The method for manufacturing a spark plug for an internal combustion engine according to claim 3. In the state before processing the inner peripheral end of the through hole, a temporary hole (52) is formed in the cover part, and when viewed from the opening direction of the temporary hole, the tip of the center electrode is The method for manufacturing a spark plug for an internal combustion engine according to any one of claims 2 to 4, wherein the spark plug fits within the temporary hole and is processed to expand the temporary hole. Claims 2 to 3, wherein a tip concave surface (423) is formed by processing the tip of the center electrode, and then a noble metal tip (44) having a proximal convex surface (441) that fits into the concave tip is joined. 5. The method for manufacturing a spark plug for an internal combustion engine according to any one of Item 5. 2. The method of manufacturing a spark plug for an internal combustion engine according to claim 1, wherein an electrode member is joined to the inner peripheral end of the through hole so that the discharge gap has a predetermined size. The spark plug for an internal combustion engine according to claim 7, wherein the electrode member is joined to a part of the inner peripheral end in the circumferential direction, and the size of the discharge gap is adjusted depending on the joining position in the circumferential direction. manufacturing method. The electrode member is joined to a part of the inner circumferential end in the circumferential direction, and the size of the discharge gap is adjusted by the amount of protrusion of the inner end of the electrode member that protrudes inward from the inner circumferential end. The method for manufacturing a spark plug for an internal combustion engine according to claim 7. The internal combustion engine according to claim 7, wherein the electrode member has a cylindrical shape, and the size of the discharge gap is adjusted by the amount of proximal protrusion of the electrode member protruding from the inner peripheral end toward the proximal end. How to manufacture spark plugs for.

Images