JP2021007082A - Method for manufacturing spark plug - Google Patents

Abstract

To provide a method for manufacturing a spark plug, capable of detecting the position of a ground electrode that is connected to a main metal fitting with shafts of various lengths.SOLUTION: A method for manufacturing a spark plug includes: a tightening step in which a male screw of a main metal fitting is tightened to a female screw of a gauge that includes the female screw and a gauge end face perpendicular to the central axis of the female screw, and thereby the gauge end face is brought into contact with a flange and a ground electrode is projected from the gauge; an arrangement step in which the gauge that is in contact with the flange is arranged in a detection device, and the gauge end face is brought into contact with the reference face of the detection device; and a detection step in which the position of the ground electrode in the gauge is detected using the detection device with the gauge arranged therein. The detection device includes: a sensor which detects the position of the ground electrode in a non-contact manner from a direction perpendicular to the central axis; and a moving device that moves the sensor along the direction of extension of the central axis.SELECTED DRAWING: Figure 6

Description

The present invention relates to a method for manufacturing a spark plug in which a ground electrode is connected to a main metal fitting.

The main metal fitting that insulates and holds the center electrode of the spark plug has a screw formed on the shaft portion provided with the flange portion. The spark plug is attached to the engine by tightening the screw of the main metal fitting into the screw hole of the engine. When the main metal fitting of the spark plug is screwed into the engine, the main metal fitting moves in the axial direction while rotating around the shaft until it is regulated by the collar. The position of the ground electrode in the circumferential direction of the main metal fitting is determined when the flange portion regulates the axial movement of the male screw.

A spark plug attached to the engine creates a flame nucleus in the spark gap between the ground electrode and the center electrode connected to the main metal fitting. In order to grow the flame nucleus, the spark plug is preferably attached to the engine so that the ground electrode is placed at a position that does not interfere with the airflow in the combustion chamber that occurs in the compression stroke that is the pre-ignition stage.

The circumferential position of the ground electrode of the spark plug to which the main metal fitting is attached to the engine is the circumferential distance between the position where the male thread starts to be cut with respect to the ground electrode and the ground electrode, and the position of the male screw from the flange. It depends on the axial distance to the thread. Patent Document 1 discloses a technique of tightening a screw of a main metal fitting to a gauge on which a female screw is formed and detecting the position of the ground electrode using a detection device in order to confirm the position of the ground electrode with respect to the male screw. Has been done.

Japanese Unexamined Patent Publication No. 2010-218828

However, since there are main metal fittings having shaft portions having different lengths, in the technique disclosed in Patent Document 1, a technique for detecting the position of the ground electrode connected to the main metal fittings having shaft portions having various lengths is required. Has been done.

The present invention has been made in order to meet this demand, and an object of the present invention is to provide a method for manufacturing a spark plug capable of detecting the position of a ground electrode connected to a main metal fitting having a shaft portion having various lengths. ..

In order to achieve this object, the present invention includes a cylindrical shaft portion extending along the axis from the front end side to the rear end side, and a flange portion extending radially outward from the rear end of the shaft portion. , The main metal fitting with a screw formed on the outer peripheral surface of the shaft, the center electrode that is insulated and held in the center of the tip side of the shaft, and its own base end is connected to the shaft, and its tip is A method for manufacturing a spark plug including a ground electrode facing the center electrode via a spark gap, which is a preparatory step for preparing a main metal fitting to which the ground electrode is connected, and a female screw and a female screw. Tighten the screw of the main metal fitting to the female screw of the gauge having the gauge end face perpendicular to the central axis, bring the collar part into contact with the gauge end face, and make the ground electrode protrude from the gauge, and the collar part becomes the gauge. It is provided with an arrangement step of arranging the contacted gauge on the detection device and bringing the gauge end surface into contact with the reference surface of the detection device, and a detection step of detecting the position of the ground electrode on the gauge using the detection device on which the gauge is arranged. The detection device includes a sensor that non-contactly detects the position of the ground electrode from a direction perpendicular to the central axis, and a moving device that moves the sensor along the extending direction of the central axis.

According to the method for manufacturing a spark plug according to claim 1, in the detection device that detects the position of the ground electrode in the detection step, the sensor detects the position of the ground electrode from the direction perpendicular to the central axis of the female screw of the gauge. Since the moving device moves the sensor along the extending direction of the central axis and the position of the sensor can be set according to the position of the ground electrode, the position of the ground electrode connected to the main metal fitting having the shaft portion of various lengths. Can be detected.

It is one side sectional view of the spark plug in one Embodiment. It is sectional drawing of an object. (A) is a plan view of the gauge, and (b) is a side view of the gauge as seen from the direction of arrow IIIb in FIG. 3 (a). It is a top view of the detection device in which the gauge to which the object is attached is arranged. It is sectional drawing of the detection apparatus in line VV of FIG. It is a side view of the detection device in which a gauge is arranged. It is a schematic diagram of the position detection of the ground electrode. It is a side view of the detection device in which another gauge is arranged.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a one-sided cross-sectional view of the spark plug 10 with the axis O as a boundary in one embodiment. In FIG. 1, the lower side of the paper surface is referred to as the front end side of the spark plug 10, and the upper side of the paper surface is referred to as the rear end side of the spark plug 10 (the same applies to FIG. 2).

As shown in FIG. 1, the spark plug 10 includes a center electrode 13, a main metal fitting 15, and a ground electrode 24. The insulator 11 that holds the center electrode 13 is a substantially cylindrical member made of alumina or the like, which is excellent in insulating properties and mechanical properties at high temperatures. The insulator 11 has a shaft hole 12 penetrating along the axis O.

The center electrode 13 is a rod-shaped electrode that is inserted into the shaft hole 12 of the insulator 11 and arranged along the axis O. The center electrode 13 is arranged in the shaft hole 12 so that the tip of the center electrode 13 projects from the tip of the insulator 11. In the center electrode 13, a core material having excellent thermal conductivity is embedded in the electrode base material. The electrode base material is formed of an alloy mainly composed of Ni or a metal material composed of Ni, and the core material is formed of copper or an alloy containing copper as a main component. It is possible to omit the core material.

The terminal fitting 14 is a rod-shaped metal member (for example, low carbon steel) to which a high voltage cable (not shown) is connected, and the tip end side is inserted into the shaft hole 12. The terminal fitting 14 is electrically connected to the center electrode 13 in the shaft hole 12. The terminal fitting 14 is attached to the rear end of the insulator 11.

The main metal fitting 15 is a substantially cylindrical member formed of a conductive metal material (for example, low carbon steel or the like). The main metal fitting 15 includes a shaft portion 16 formed in a cylindrical shape, an annular flange portion 17 projecting outward from the rear end of the shaft portion 16 in the radial direction, and a tubular portion 18 connected to the rear end side of the flange portion 17. And have. The tubular portion 18 includes a thin-walled portion 19 having a wall thickness thinner than that of the flange portion 17, and a tool engaging portion 20 adjacent to the rear end side of the thin-walled portion 19.

The shaft portion 16 is a portion that supports the insulator 11 from the tip side. A male screw 21 is formed on the outer peripheral surface of the shaft portion 16. The male screw 21 fits into the screw hole of the engine (not shown) and fixes the main metal fitting 15 to the engine. The flange portion 17 is a portion for regulating the screwing amount of the male screw 21 into the engine and closing the gap between the male screw 21 and the screw hole. In the present embodiment, the gasket 23 is attached to the shaft portion 16 on the tip end surface 22 side of the flange portion 17. The tip surface 22 is a surface perpendicular to the axis O. The gasket 23 sandwiched between the flange portion 17 and the engine seals the gap between the screw hole of the engine and the male screw 21.

The thin-walled portion 19 is a portion for plastically deforming and crimping and fixing when the main metal fitting 15 is assembled to the insulator 11. The tool engaging portion 20 is a portion for engaging a tool such as a wrench when the screw 21 is screwed into a screw hole of an engine (not shown).

The ground electrode 24 is a rod-shaped metal member (for example, made of a nickel-based alloy) having a base end portion 25 joined to the shaft portion 16 of the main metal fitting 15 and a tip end portion 26 opposite to the base end portion 25. is there. The tip portion 26 of the ground electrode 24 faces the center electrode 13 via a spark gap G. In the present embodiment, the ground electrode 24 of the main metal fitting 15 is bent.

FIG. 2 is a cross-sectional view including the axis O of the object 30. The object 30 is a member for detecting the position of the ground electrode 24 with respect to the screw 21 of the main metal fitting 15, and the ground electrode 24 is connected to the main metal fitting 15. The ground electrode 24 of the object 30 has a linear shape before bending, and the thin portion 19 of the object 30 has a cylindrical shape before bending.

The spark plug 10 is manufactured by, for example, the following method. First, a work (not shown) is processed to obtain an object 30. In the object 30, the ground electrode 24 (a linear rod before bending) is joined to the tip of the shaft portion 16 of the main metal fitting 15 formed in a tubular shape by cold forging, cutting, or the like. The object 30 has a shaft portion 16 having a screw 21 rolled and plated or the like. The object 30 uses a gauge 40 (see FIGS. 3A and 3B) and uses a detection device 60 (described later) to position the male screw 21 and the ground electrode 24 (α described later). Is measured.

Separately from this, the center electrode 13 is inserted into the shaft hole 12 of the insulator 11 and arranged so that the tip of the center electrode 13 is exposed to the outside from the shaft hole 12. Next, the terminal fitting 14 is inserted into the shaft hole 12 of the insulator 11, and the terminal fitting 14 and the center electrode 13 are electrically connected. Next, the insulator 11 is inserted into the main metal fitting 15 of the object 30, the thin-walled portion 19 is bent, and the main metal fitting 15 is assembled to the insulator 11. Next, the ground electrode 24 is bent so that the tip portion 26 faces the center electrode 13, and the gasket 23 is attached to obtain the spark plug 10.

When the main metal fitting 15 of the obtained spark plug 10 is screwed into the screw hole of the engine (not shown), it is wound around the male screw 21 until the gasket 23 arranged on the flange 17 is in close contact with the engine. Along the main metal fitting 15, the main metal fitting 15 advances in the axial direction while rotating around the axis O. The position of the ground electrode 24 in the circumferential direction of the main metal fitting 15 attached to the engine is determined when the flange portion 17 and the gasket 23 regulate the axial movement of the male screw 21.

In the spark plug 10 attached to the engine (not shown), when a high voltage is applied to the terminal fitting 14, a spark discharge occurs between the tip 26 of the ground electrode 24 and the center electrode 13, causing a flame nucleus. create. In order to grow the flame nucleus and facilitate ignition of the air-fuel mixture, the ground electrode is located at a position in the circumferential direction that does not prevent the airflow in the combustion chamber of the engine generated in the compression stroke, which is the stage before ignition, from flowing through the spark gap G. It is preferable that 24 is arranged.

If there is no variation in the thickness of the gasket 23, the screw 21 of the main metal fitting 15 is tightened to the screw hole of the engine (not shown) with the specified tightening torque (hereinafter referred to as "specified torque"). The position of the ground electrode 24 in the circumferential direction with respect to the center electrode 13 (axis O) is determined by the axial and circumferential positions of the male screw 21 with respect to the tip surface 22 of the flange portion 17. Therefore, in order to improve the accuracy of the position of the ground electrode 24 (the angle around the axis O) with respect to the center electrode 13 of the spark plug 10 attached to the engine at a specified torque, and to guarantee the stability of ignition of the air-fuel mixture. , The position of the ground electrode 24 with respect to the screw 21 of the main metal fitting 15 is measured, and the accuracy of the position is guaranteed.

FIG. 3A is a plan view of the gauge 40 used when measuring the position of the ground electrode 24 with respect to the screw 21 of the main metal fitting 15. FIG. 3B is a side view of the gauge 40 as viewed from the direction of arrow IIIb in FIG. 3A. The gauge 40 includes a cylindrical main body 41 and flanges 42 and 43 protruding outward from both ends in the axial direction of the main body 41 in the radial direction of the main body 41, respectively. The gauge 40 is formed with holes 44 penetrating the main body 41 and the flanges 42 and 43. A female screw 45 is formed on the inner surface of the hole 44. The female screw 45 is a screw standardized based on ISO and JIS, and is composed of, for example, a screw for a spark plug specified in JIS B8031: 2006.

In the gauge 40, first gauge reference portions 46 and 47 are formed on the side surfaces of the flange portions 42 and 43 located on the outer side in the radial direction of the female screw 45, respectively. The first gauge reference portions 46 and 47 are flat surfaces parallel to the central axis C of the female screw 45. The first gauge reference portions 46 and 47 are located on the same plane.

The gauge 40 is a side surface of the flange portions 42, 43 located on the outer side in the radial direction of the female screw 45, and the second gauge reference portions 48, 49 are formed at positions intersecting with the first gauge reference portions 46, 47, respectively. Has been done. The second gauge reference portions 48 and 49 are flat surfaces parallel to the central axis C of the female screw 45. The second gauge reference portions 48 and 49 are located on the same plane. The second gauge reference portions 48 and 49 are planes perpendicular to the first gauge reference portions 46 and 47.

The axial end surface 50 of the flange portion 42 and the axial end surface (gauge end surface) 52 of the flange portion 43 are surfaces perpendicular to the central axis C of the female thread 45. An index 51 is marked on the end face 50. The index 51 is a groove, which extends linearly from the outer edge of the end face 50 toward the central axis C of the female thread 45 to the edge of the female thread 45. The index 51 is parallel to the first gauge reference portions 46 and 47 and perpendicular to the second gauge reference portions 48 and 49. The distances between the first gauge reference portions 46 and 47 and the central axis C and the distances between the second gauge reference portions 48 and 49 and the central axis C are appropriately set.

The axial distance from the end face 50 of the flange portion 42 to the end face 52 of the flange portion 43 is substantially equal to the length of the shaft portion 16 of the object 30 (see FIG. 2). Therefore, when the shaft portion 16 of the main metal fitting 15 is inserted from the flange portion 43 side of the gauge 40 and the screw 21 is screwed into the female screw 45, the tip surface 22 of the flange portion 17 comes into contact with the end surface 52 of the flange portion 43. The shaft portion 16 fits in the hole 44, and the ground electrode 24 protrudes from the hole 44.

The tightening torque when the screw 21 of the main metal fitting 15 is screwed into the female screw 45 of the gauge 40 is equal to or less than the specified torque when the main metal fitting 15 is tightened into the screw hole of the engine (not shown). It is naturally possible to screw the main metal fitting 15 into the gauge 40 by hand or the like, stop screwing immediately when the tip surface 22 of the flange portion 17 comes into contact with the end surface 52 of the gauge 40, and set the tightening torque ≈ 0 Nm. ..

When the main metal fitting 15 is screwed into the gauge 40 with a predetermined tightening torque and the ground electrode 24 is at the position of the index 51, the main metal fitting 15 is screwed into the engine (not shown) with a specified torque. The index 51 is provided so that the ground electrode 24 is arranged at an optimum position that does not obstruct the air flow in the combustion chamber. When the tightening torque to the gauge 40 of the main metal fitting 15 increases, the amount of the ground electrode 24 rotating around the central axis C increases, and when the tightening torque decreases, the ground electrode 24 rotates around the central axis C. The amount will be small. Therefore, the gauge 40 is manufactured according to the tightening torque of the main metal fitting 15.

FIG. 4 is a plan view of the detection device 60 in which the gauge 40 to which the object 30 is attached is arranged. FIG. 5 is a view of a cross section of the detection device 60 on the VV line of FIG. 4 as viewed from the lower side of FIG. In FIG. 5, the light projecting unit 70 is not shown, and the ground electrode 24 protruding from the gauge 40 is shown by a chain double-dashed line. The detection device 60 is a device that detects the position of the ground electrode 24 attached to the gauge 40.

As shown in FIG. 4, the detection device 60 emits light toward the gauge 40, the stage 61 that determines the axial position of the gauge 40, the positioning portion 64 that determines the position perpendicular to the central axis C of the gauge 40, and the gauge 40. It includes a light projecting unit 70 for irradiating light and a light receiving unit 71 for receiving light.

A reference surface 63 is formed on the stage 61. A gauge 40 to which the object 30 is attached is placed on the reference surface 63 with a predetermined tightening torque less than the specified torque. Since the collar portion 17 of the object 30 (see FIG. 5) is in contact with the end surface 52 of the gauge 40, the collar portion 17 and the cylinder portion 18 protrude from the hole 44 of the gauge 40. The stage 61 is formed with a notch 62 for accommodating the collar portion 17 and the cylinder portion 18 so that the end surface 52 of the gauge 40 comes into contact with the reference surface 63 without being disturbed by the collar portion 17 and the cylinder portion 18. When the gauge 40 is placed on the stage 61 with the end surface 52 of the gauge 40 in contact with the reference surface 63, the central axis C of the female screw 45 becomes perpendicular to the reference surface 63.

The positioning portion 64 is provided on the reference surface 63 of the stage 61. The positioning portion 64 is provided with a first reference portion 65 to which the first gauge reference portion 47 of the gauge 40 is pressed and a second reference portion 66 to which the second gauge reference portion 49 of the gauge 40 is pressed. There is. The first reference portion 65 and the second reference portion 66 are planes perpendicular to the reference plane 63 of the stage 61, and the first reference portion 65 is perpendicular to the second reference portion 66. The height of the positioning portion 64 is lower than the height of the gauge 40 in the axial direction (see FIG. 5).

The light projecting unit 70 and the light receiving unit 71 are transmissive sensors. The light projecting unit 70 emits light such as laser light. The light projecting unit 70 projects parallel light perpendicular to the second reference unit 66 toward the ground electrode 24 protruding from the gauge 40 through an optical system such as a collimator lens. The light receiving unit 71 includes an image pickup element that detects an image formed by blocking a part of light rays by the ground electrode 24. An arithmetic unit (not shown) is connected to the light projecting unit 70 and the light receiving unit 71. The arithmetic unit detects the position of the ground electrode 24 on the virtual plane (paper surface of FIG. 7) parallel to the reference surface 63 (see FIG. 5) by using the image formed on the light receiving unit 71.

FIG. 6 is a side view of the detection device 60 in which the gauge 40 is arranged on the stage 61. The detection device 60 includes a first moving device 79 that supports the light projecting unit 70, and a second moving device 80 that supports the light receiving unit 71. The first moving device 79 and the second moving device 80 are provided on the base 78 on which the stage 61 is arranged. The first moving device 79 and the second moving device 80 move the light emitting unit 70 and the light receiving unit 71 perpendicular to the reference surface 63 of the stage 61, respectively, and on a virtual plane parallel to the reference surface 63 (paper surface of FIG. 7). Stops the light projecting unit 70 and the light receiving unit 71.

FIG. 7 is a schematic diagram of position detection of the ground electrode 24. The arithmetic unit (not shown) has a reference point 72 on the light receiving portion 71 corresponding to the central axis C of the female screw 45 (see FIG. 4) and a light receiving light on a virtual plane (paper surface of FIG. 7) intersecting with the ground electrode 24. The distance ε between the center 74 of the image 73 of the ground electrode 24 formed on the portion 71 and the center 74 of the image 73 is measured, and the central axis C and the reference point 72 are determined from the equation of α = sin ^-1 (ε / β). The angle α formed by the line segment 76 connecting the central axis C and the line segment 77 connecting the center axis 75 of the ground electrode 24 is obtained. α is the amount of deviation of the ground electrode 24. The distance β between the center of gravity 75 of the ground electrode 24 and the central axis C is a known value and is input to the arithmetic unit in advance.

The reference point 72 is a point indicating the optimum position of the ground electrode 24. The line segment 76 connecting the reference point 72 and the central axis C overlaps with the index 51 of the gauge 40 (see FIG. 3A). When the first gauge reference portion 47 of the gauge 40 comes into contact with the first reference portion 65 of the detection device 60, the central axis C of the gauge 40 comes to a predetermined position. Therefore, the reference point 72 is preset by an arithmetic unit (not shown) according to the position of the central axis C of the gauge 40.

The arithmetic unit determines whether α is within the permissible range or α is out of the permissible range for the object 30. The spark plug 10 is manufactured by assembling the insulator 11 to the main metal fitting 15 whose α is determined to be within the permissible range. As a result, the spark plug 10 with little variation in the position of the ground electrode 24 with respect to the male screw 21 can be manufactured.

FIG. 8 is a side view of the detection device 60 in which another gauge 90 is arranged. The axial length of the gauge 90 is shorter than the axial length of the gauge 40 (see FIG. 6). The gauge 90 is the position of the ground electrode 24 connected to the main metal fitting whose shaft portion (male screw) is shorter than the length of the shaft portion 16 (male screw 21) of the main metal fitting 15 screwed into the gauge 40. Is used to detect. Therefore, the height of the end surface 91 from the reference surface 63 when the gauge 90 is arranged on the reference surface 63 of the stage 61 is lower than the height of the end surface 50 of the gauge 40 (see FIG. 6). The ground electrode 24 projects from the end face 91 of the gauge 90.

In the detection device 60, the first moving device 79 and the second moving device 80 move the light emitting unit 70 and the light receiving unit 71 along the extending direction of the central axis C, and the light emitting unit 70 is moved according to the position of the ground electrode 24. The positions of 70 and the light receiving unit 71 are set. Thereby, the position of the ground electrode 24 connected to the main metal fitting having the shaft portion (male screw) of various lengths can be detected.

On the contrary, when the stage 61 is moved without moving the light emitting unit 70 and the light receiving unit 71, the central axis C and the reference surface 63 are kept orthogonal to each other in order to ensure measurement accuracy. A mechanism for moving the stage 61 along C is required. In this case, the structure of the detection device becomes complicated. In order to avoid this, the detection device 60 moves the light projecting unit 70 and the light receiving unit 71 by the first moving device 79 and the second moving device 80, so that a complicated mechanism for moving the stage 61 can be omitted. Further, since the reference point 72 (see FIG. 7), which is the reference point for measurement, is set by the arithmetic unit, the position accuracy of the reference point 72 can be ensured by the electrical processing by the arithmetic unit. Therefore, the measurement accuracy can be ensured.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It can be easily inferred.

In the embodiment, the spark plug 10 in which the gasket 23 is arranged on the tip end surface 22 of the main metal fitting 15 has been described, but the present invention is not necessarily limited to this. When the spark plug 10 is a conical seal type (tapered sheet type), the tip surface 22 can be made a tapered surface and the gasket 23 can be omitted. In this case as well, the gauge 40 and the detection device 60 can be used to detect the position of the ground electrode 24 with respect to the male screw 21.

In the embodiment, the case where the male screw 21 is rolled after connecting the ground electrode 24 to the main metal fitting 15 has been described, but the present invention is not necessarily limited to this. After forming the screw 21 on the main metal fitting 15, it is naturally possible to connect the ground electrode 24 to the main metal fitting 15. Further, it is naturally possible to form the male screw 21 by cutting. After detecting the position of the ground electrode 24 of the object 30 by the detection device 60, the object 30 may be plated or the like. The position of the ground electrode 24 may be detected by the detection device 60 for all the samples or for the sample taken out.

In the embodiment, the case where the distance between the end faces 50 and 52 of the gauge 40 (the height of the gauge 40) is substantially equal to the length of the shaft portion 16 of the main metal fitting 15 has been described, but the present invention is not necessarily limited to this. If a part of the ground electrode 24 protrudes from the end face 50 of the gauge 40, the position of the ground electrode 24 can be detected by using the detection device 60. Therefore, within that range, the height of the gauge 40 is set to the length of the shaft portion 16. Of course, it is possible to make it lower or higher than that.

When the ground electrode 24 is tilted and connected to the main metal fitting 15, the position of the tip of the ground electrode 24 may be deviated from the position where the ground electrode 24 is connected to the main metal fitting 15. Therefore, it is better to measure the position of the ground electrode 24 on the side connected to the main metal fitting 15 (base end portion 25 side) as much as possible. Therefore, it is preferable that the end face of the shaft portion 16 protrudes from the end face 50 of the gauge 40.

In the embodiment, the case where the first gauge reference portion 47 of the gauge 40 and the first reference portion 65 of the detection device 60 are flat surfaces parallel to the central axis C of the female screw 45 has been described, but this is not necessarily the case. It is not something that can be done. The first gauge reference portion 47 and the first reference portion 65 may be inclined surfaces that are inclined with respect to the central axis C, or one of the first gauge reference portion 47 and the first reference portion 65 may be a surface and the other may be a plurality of points. Of course, it is possible. This is because it is sufficient if the gauge 40 can be positioned on the reference surface 63 of the detection device 60. The same applies to the second gauge reference unit 49 and the second reference unit 66.

In the embodiment, the case where the first gauge reference unit 46, 47 and the second gauge reference unit 48, 49 are vertical and the first reference unit 65 and the second reference unit 66 are vertical has been described. , Not necessarily limited to this. Of course, it is possible to make the angle formed by the first gauge reference portions 46 and 47 and the second gauge reference portions 48 and 49 an acute angle or an obtuse angle. Of course, it is also possible to appropriately set the angle formed by the first reference unit 65 and the second reference unit 66 according to the angle formed by the first gauge reference units 46, 47 and the second gauge reference units 48, 49.

In the embodiment, the case where the index 51 of the gauge 40 is a groove has been described, but the present invention is not necessarily limited to this. As for the index 51, the shape, size, and the like can be appropriately set as long as the object 30 is screwed into the gauge 40 and the operator who sets the gauge 40 in the detection device 60 can visually recognize the index 51.

In the embodiment, the case where the tightening torque when the screw 21 of the main fitting 15 is screwed into the female screw 45 of the gauge 40 is equal to or less than the specified torque when the main fitting 15 is tightened into the screw hole of the engine has been described. However, it is not always limited to this. The tightening torque may be the same as the specified torque.

In the embodiment, the case where the second reference unit 66 is provided in the detection device 60 has been described, but the present invention is not necessarily limited to this. If the spread of the beam between the light emitting unit 70 and the light receiving unit 71 is so small that it can be ignored, it is naturally possible to omit the second reference unit 66 that keeps the distance between the light emitting unit 70 and the gauge 40 constant. Is.

In the embodiment, the detection device 60 including the transmission type sensor (light emitting unit 70 and light receiving unit 71) has been described, but the present invention is not necessarily limited to this. Of course, it is possible to replace the light emitting unit 70 and the light receiving unit 71 with a reflection type sensor. In this case, the light receiving unit 71 is arranged at a position where the reflected light of the ground electrode 24 can be received. When the light emitting unit 70 and the light receiving unit 71 are reflection type sensors, a second reference unit 66 for positioning the second gauge reference unit 49 of the gauge 40 is provided, so that a measurement error due to the position of the gauge 40 is provided. Can be less likely to occur.

In the embodiment, the detection device 60 including a set of the light emitting unit 70 and the light receiving unit 71 has been described, but the present invention is not limited to this. In addition to the light projecting unit 70 and the light receiving unit 71, a light projecting unit that emits parallel light orthogonal to the parallel light emitted by the light projecting unit 70 and parallel to the reference surface 63 toward the ground electrode 24, and the light thereof. Of course, it is possible to provide a light receiving unit that receives the light. This makes it possible to measure α> 90 °.

In the embodiment, the detection device 60 in which the light emitting unit 70 and the light receiving unit 71 are non-contact sensors has been described, but the present invention is not necessarily limited to this. Of course, it is possible to adopt other non-contact type sensors. Other non-contact sensors include, for example, those having a transmitting unit for transmitting a sound wave such as an ultrasonic wave and a receiving unit for receiving a sound wave.

In the embodiment, the case where the reference point 72 corresponding to the central axis C of the gauge 40 is set in advance on the light receiving unit 71 has been described, but the present invention is not necessarily limited to this. An arithmetic unit (not shown) detects the edge of the angle formed by the end face 50 of the gauge 40 (see FIG. 5) and the first gauge reference unit 47 from the light receiving unit 71, and a known value (first gauge) from the edge. Of course, it is possible to set the reference point 72 at a position separated by (the distance between the reference unit 47 and the central axis C).

In the embodiment, as an example of detecting the position of the ground electrode 24 on the gauge 40, the angle α formed by the line segments 76 and 77 obtained from the equation α = sin ^-1 (ε / β) is taken as the deviation amount of the ground electrode 24. Although the case of doing so has been explained, it is not necessarily limited to this. It is possible to appropriately set where the displacement amount of the ground electrode 24 is used. For example, it is naturally possible to adopt the distance ε between the center 74 of the image 73 of the ground electrode 24 and the reference point 72 as the amount of deviation of the ground electrode 24. Further, for example, it is naturally possible to obtain the amount of deviation of the ground electrode 24 based on the distance between the end of the image 73 of the ground electrode 24 and the reference point 72.

In the embodiment, the case where the ground electrode 24 of the spark plug 10 is bent has been described. However, it is not always limited to this. Of course, it is possible to use a linear ground electrode 24 instead of using the bent ground electrode 24. In this case, the tip end side of the shaft portion 16 is extended in the axial direction, the linear ground electrode 24 is joined to the shaft portion 16, and the tip end portion 26 of the ground electrode 24 faces the center electrode 13.

In the embodiment, a case where the ground electrode 24 is arranged so that the tip 26 of the ground electrode 24 and the center electrode 13 face each other on the axis O has been described. However, the positional relationship is not necessarily limited to this, and the positional relationship between the ground electrode 24 and the center electrode 13 can be appropriately set. As another positional relationship between the ground electrode 24 and the center electrode 13, for example, the ground electrode 24 is arranged so that the side surface of the center electrode 13 and the tip portion 26 of the ground electrode 24 face each other.

Although the description is omitted in the embodiment, the tip containing the noble metal is arranged on the center electrode 13 and the ground electrode 24, and is arranged between the chip arranged on the center electrode 13 and the ground electrode 24 or on the ground electrode 24. Of course, it is possible to form a spark gap G between the tip and the center electrode 13. The chip can improve the spark consumption resistance of the center electrode 13 and the ground electrode 24.

10 Spark plug 13 Center electrode 15 Main metal fittings 16 Shaft 17 flange 21 Male screw 24 Ground electrode 25 Base end 26 Tip 40, 90 Gauge 45 Female screw 52 End face (gauge end face)
60 Detection device 63 Reference plane 70 Floodlight (part of sensor)
71 Light receiving part (part of the sensor)
79 First mobile device (mobile device)
80 Second mobile device (mobile device)
C central axis G spark gap O axis

Claims (1)

It is provided with a cylindrical shaft portion extending from the front end side to the rear end side along the axis, and a flange portion extending radially outward from the rear end of the shaft portion, and is screwed on the outer peripheral surface of the shaft portion. With the main metal fittings on which
A center electrode that is insulated and held in the center of the tip side of the shaft portion,
A method for manufacturing a spark plug, comprising: a ground electrode having its own base end connected to the shaft and having its own tip facing the center electrode via a spark gap.
A preparatory step for preparing the main metal fitting to which the ground electrode is connected, and
The male screw of the main metal fitting is tightened to the female screw of the gauge having the female screw and the gauge end face perpendicular to the central axis of the female screw, the flange portion is brought into contact with the gauge end face, and the gauge The tightening process to project the ground electrode and
An arrangement step of arranging the gauge whose collar is in contact with the gauge on the detection device and bringing the gauge end surface into contact with the reference surface of the detection device.
A detection step of detecting the position of the ground electrode on the gauge using the detection device on which the gauge is arranged is provided.
The detection device includes a sensor that non-contactly detects the position of the ground electrode from a direction perpendicular to the central axis, and a moving device that moves the sensor along the extending direction of the central axis. Production method.

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