JP2004241267A - Method and device for manufacturing internal combustion engine spark plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for manufacturing an internal combustion engine spark plug capable of acquiring both images of the tip part of a center electrode and the noble metal chip of an earthed electrode by one time photographing, and capable of acquiring relative position information of both of them with high precision, as to a spark plug having an earthed electrode combined with a projecting noble metal chip at a position facing the tip of a center electrode. <P>SOLUTION: This method for manufacturing the internal combustion engine spark plug is provided with a photographing process to photograph the images whereon the silhouettes of the noble metal chip 121 of the center electrode 110 and the noble metal chip 113 of the earthed electrode 110 are made clear by a camera 251 with the rear back part 114b of the earthed electrode 110 turned into a bright background by irradiating light onto the rear back part 114b of the earthed electrode 110 by a first lighting system 253, and a positional information acquiring process to acquire a deviated dimension P in a first specific direction of the noble metal chip 113 of the earthed electrode 110 in relation to the noble metal chip 121 of the center electrode 120 based on the images. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for manufacturing a spark plug for an internal combustion engine.
[0002]
[Prior art]
In a spark plug for an internal combustion engine, the positional accuracy of the ground electrode with respect to the center electrode is important. However, when manufacturing a spark plug, a variation in the bending process of the ground electrode, a displacement of the noble metal tip fixed to the ground electrode or the center electrode, and the like occur, and the position of the ground electrode with respect to the center electrode is out of a predetermined range. There is. In this case, troubles such as shortening of life due to uneven consumption of the ground electrode or the center electrode and poor ignition are caused.
On the other hand, in recent years, in order to improve the positional accuracy of the ground electrode with respect to the center electrode, an image of the ground electrode and the center electrode is taken by a camera, and positional information of the center electrode and the ground electrode is obtained based on the image. Technology has been proposed. Further, a technique for adjusting the position of the ground electrode with respect to the center electrode within a predetermined range based on the position information has been proposed (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-11-112143 (FIGS. 3, 23, 24)
[0004]
[Problems to be solved by the invention]
By the way, when the images of the ground electrode and the center electrode are taken, depending on the taking direction, one of the two may become the background of the other, or the image may overlap with another part (for example, metal shell). . However, since the ground electrode, the center electrode, and the metal shell of the spark plug are all made of metal and may have the same metallic luster, the imaging target site (for example, the tip of the center electrode) and the background may be used. The boundary with the part to be formed (for example, a ground electrode) may be unclear. For this reason, it becomes difficult to detect the contour line of the imaging target portion, and it may be difficult to obtain accurate position information on the imaging target portion.
[0005]
In recent years, spark plugs for internal combustion engines have been required to have high ignition performance. In order to respond to this demand, for example, a spark plug has been developed in which a convex noble metal tip is fixed to a position of the ground electrode facing the tip of the center electrode. For this type of spark plug, the positional accuracy of the noble metal tip of the ground electrode with respect to the tip of the center electrode is particularly important in order to exhibit high ignition performance. For this reason, the position information of the noble metal tip of the center electrode and the ground electrode must be acquired, and the position of the noble metal tip of the ground electrode with respect to the tip of the center electrode must be adjusted within a predetermined range. There was a possibility that it would be difficult.
[0006]
The present invention has been made in view of such a situation, and relates to a spark plug having a ground electrode to which a convex noble metal tip is fixed at a position facing the tip of the center electrode, in a single photographing operation. It is an object of the present invention to provide a method and an apparatus for manufacturing a spark plug for an internal combustion engine, which can obtain an image of both a precious metal tip and a noble metal tip of a ground electrode, and can obtain relative position information of both with high accuracy. And
[0007]
Means for Solving the Problems, Functions and Effects
The solution is a cylindrical insulator having a shaft hole penetrating in the axial direction, and a center electrode inserted into the shaft hole of the insulator, and a tip portion protruding from a tip surface of the insulator. A central electrode having: a metal shell surrounding the insulator; and a ground electrode having a base end fixed to the metal shell, and a bent ground electrode, wherein the center electrode is formed on an inner surface facing the center electrode. A spark plug for an internal combustion engine including a convex noble metal tip fixed at a position facing a tip of the internal electrode, and a ground electrode forming a spark discharge gap between the tip of the noble metal tip and the tip of the center electrode. Wherein the center electrode is on the near side, the base end of the ground electrode is on the back side, and a camera is obtained such that the center electrode and the base end of the ground electrode overlap each other. With the Of the images taken by the camera, the tip image corresponding to the tip of the center electrode and the noble metal tip image corresponding to the noble metal tip of the ground electrode are illuminated so as to be silhouetted with respect to the background. Performing a photographing step of photographing the upper end of the center electrode and the noble metal tip of the ground electrode, and, based on the image obtained in the photographing step, the tip of the center electrode and the ground electrode. A position information obtaining step of obtaining relative position information with respect to a noble metal tip.
[0008]
In the method for manufacturing a spark plug for an internal combustion engine according to the present invention, a spark plug having a ground electrode to which a convex noble metal tip is fixed at a position facing the tip of the center electrode, wherein the center electrode is on the front side and the base end of the ground electrode The camera is arranged such that an image in which the portion is on the back side and the center electrode and the base end of the ground electrode overlap each other is obtained. In this way, when photographing the front end portion of the center electrode and the noble metal tip of the ground electrode, the back portion of the inner surface of the ground electrode, which is located on the back side of the center electrode, becomes the background. In this case, in the conventional photographing process, for example, the tip of the center electrode and the noble metal tip of the ground electrode are photographed by illuminating the spark plug with a lighting device arranged between the camera and the spark plug. However, since the rear part of the ground electrode has the same metallic luster as the tip part of the center electrode and the noble metal tip of the ground electrode, the back part of the ground electrode and the tip part of the center electrode and the noble metal tip of the ground electrode Sometimes became unclear. In addition, when an image is taken by illuminating the spark plug with an illuminating device arranged at a position facing the camera with the spark plug interposed therebetween, the light is blocked by the ground electrode, so the tip of the center electrode and the noble metal tip of the ground electrode Image could not be obtained. Therefore, in the conventional imaging process, when the camera is arranged such that the center electrode is on the front side, the base end of the ground electrode is on the back side, and an image in which the center electrode and the base end of the ground electrode overlap is obtained. It was difficult to clearly photograph the tip of the center electrode and the noble metal tip of the ground electrode.
[0009]
On the other hand, in the photographing process of the present invention, of the images photographed by the camera, the tip image corresponding to the tip of the center electrode and the noble metal tip image corresponding to the noble metal tip of the ground electrode are silhouetted with respect to the background. Illumination is performed so that the tip of the center electrode and the noble metal tip of the ground electrode are photographed. Specifically, for example, between the tip of the center electrode and the noble metal tip of the ground electrode and the back of the ground electrode A method of arranging a minute illumination device (for example, optical fiber illumination) in the space and irradiating light to the tip of the center electrode and the noble metal tip of the ground electrode. Alternatively, on the contrary, light may be applied to the rear portion of the inner surface of the ground electrode, which is located on the back side of the center electrode. In this method, the reflected light at the rear part of the ground electrode is blocked by the tip part of the center electrode and the noble metal tip of the ground electrode. An image in which the silhouette of the noble metal tip is clarified can be obtained.
[0010]
Thus, in the photographing process of the present invention, the camera is arranged such that the center electrode is on the front side, the base end of the ground electrode is on the back side, and an image in which the center electrode and the base end of the ground electrode overlap is obtained. Then, even when the tip of the center electrode and the noble metal tip of the ground electrode are photographed, an image in which the outline of both silhouettes is clarified by contrast with a bright background can be obtained by one photographing.
[0011]
Further, the method for manufacturing a spark plug for an internal combustion engine of the present invention has a position information obtaining step of obtaining relative position information between the tip of the center electrode and the noble metal tip of the ground electrode based on the image. As described above, in the image obtained in the photographing step, the contours of the tip of the center electrode and the noble metal tip of the ground electrode are clear, and therefore, in the position information obtaining step of the present invention, the center information is obtained with high accuracy. It is possible to obtain relative position information between the tip of the electrode and the noble metal tip of the ground electrode. Therefore, by using the relative position information, it is necessary to appropriately perform the selection of the spark plug for the internal combustion engine (selection of the acceptable and defective products) and the adjustment processing of the position of the noble metal tip of the ground electrode with respect to the tip of the center electrode. Can be.
[0012]
Further, in the method for manufacturing a spark plug for an internal combustion engine described above, the photographing step may include illuminating a rear portion of the inner surface of the ground electrode, which is located on the back side with respect to the center electrode, with a lighting device. It is preferable to use a method for manufacturing a spark plug for an internal combustion engine, which is photographed in the above.
[0013]
As one of the lighting methods in which the tip image and the noble metal chip image are silhouetted with respect to the background, a minute lighting device (for example, in the space between the noble metal tip of the center electrode and the noble metal tip of the ground electrode and the ground electrode) , An optical fiber illumination) and irradiating light to the tip of the center electrode and the noble metal tip of the ground electrode. However, since the space between the tip of the center electrode and the noble metal tip of the ground electrode and the back of the ground electrode is narrow, it may be difficult to arrange the lighting device in this space.
On the other hand, in the photographing step of the present invention, the rear part of the ground electrode is illuminated by the illumination device. Specifically, for example, an optical fiber illumination is disposed outside the space between the tip of the center electrode and the noble metal tip of the ground electrode and the ground electrode, and the optical fiber illumination causes the optical fiber illumination to be inclined with respect to the rear part of the ground electrode. There is a method of irradiating light.
[0014]
In this lighting method, the reflected light at the rear part of the ground electrode is blocked by the tip part of the center electrode and the noble metal tip of the ground electrode. An image in which the silhouette of the noble metal tip is clarified can be obtained. This illumination method can be easily performed with a simple illumination device because it is not necessary to arrange the illumination device in a narrow space between the front end portion of the center electrode and the noble metal tip of the ground electrode and the back portion of the ground electrode. . Further, since the rear portion of the ground electrode is used as a screen that creates a bright background, it is not necessary to separately provide a screen used as a bright background, and the apparatus can be easily implemented with a simple device.
[0015]
Further, in any one of the above-described methods for manufacturing a spark plug for an internal combustion engine, the relative position information includes a ground electrode specific position extracted from the noble metal tip image and a center electrode specific position extracted from the tip image. Is a distance in a specific direction between the position information acquisition step, based on the coordinate value of the ground electrode specific position on the image and the coordinate value of the center electrode specific position on the image. It is preferable to use a method for manufacturing a spark plug for an internal combustion engine that calculates the distance in the specific direction.
[0016]
In the position information acquisition step of the present invention, the distance in the specific direction is calculated based on the coordinate value of the ground electrode specific position on the image and the coordinate value of the center electrode specific position on the image. By the way, as described above, the image obtained in the photographing step is an image in which the outline of the silhouette of the tip of the center electrode and the noble metal tip of the ground electrode is clarified. For this reason, the coordinate value of the ground electrode specific position on the image and the coordinate value of the center electrode specific position on the image can be acquired with high accuracy. Therefore, in the position information obtaining step of the present invention, the distance in the specific direction is calculated based on such highly accurate coordinate values, so that the distance in the specific direction can be obtained with high accuracy.
[0017]
The specific direction may be selected in accordance with the subsequent spark plug processing step or sorting step. For example, a direction perpendicular to the central axis of the metal shell on the image (hereinafter, also referred to as a first specific direction) may be used. Can be In this case, for example, if the center position of the tip of the center electrode is selected as the center electrode specific position and the center position of the noble metal tip of the ground electrode is selected as the ground electrode specific position, the center electrode specific position and the ground electrode specific position Can be obtained as the distance in the first specific direction. Further, as the specific direction, a direction along the central axis of the metal shell on the image (hereinafter, also referred to as a second specific direction) may be used. Also in this case, when the center electrode specific position and the ground electrode specific position are selected in the same manner as described above, the gap size can be obtained as the distance between the center electrode specific position and the ground electrode specific position in the second specific direction. it can.
[0018]
Furthermore, in the method for manufacturing a spark plug for an internal combustion engine described above, the ground electrode specific position is a ground electrode center position that is a width direction center position of a tip of the noble metal tip image, and the center electrode specific position is A center electrode center position which is a center position in the width direction of the tip of the tip image, the specific direction is a first specific direction which is a direction orthogonal to a central axis of the metal shell on the image, The distance in the specific direction may be a method of manufacturing a spark plug for an internal combustion engine, wherein the distance of the center position of the ground electrode with respect to the center position of the center electrode in the first specific direction.
[0019]
In the manufacturing method of the present invention, the distance in the specific direction is defined as a deviation of the center position of the ground electrode from the center position of the center electrode in the first specific direction. That is, in the position information obtaining step, the deviation dimension of the ground electrode center position with respect to the center electrode center position in the first specific direction can be obtained. For this reason, based on this deviation size, the manufactured spark plug is sorted into a pass product and a defective product, or the deviation of the ground electrode center position in the first specific direction with respect to the center electrode center position is kept within a predetermined range. Thus, the position of the ground electrode can be adjusted.
[0020]
Further, the method for manufacturing a spark plug for an internal combustion engine according to any one of the above, wherein the ground electrode is deformed based on the relative position information, and the position of the noble metal tip of the ground electrode with respect to the tip of the center electrode. It is preferable to provide a method for manufacturing a spark plug for an internal combustion engine including an adjustment processing step for adjusting the spark plug.
[0021]
The method for manufacturing a spark plug for an internal combustion engine according to the present invention includes an adjustment processing step of adjusting the position of the noble metal tip of the ground electrode with respect to the tip of the center electrode based on the relative position information obtained in the position information obtaining step. I have. As described above, the relative position information between the tip of the center electrode and the noble metal tip of the ground electrode obtained in the position information obtaining step has high accuracy. For this reason, in the adjustment processing step of the present invention, the position of the noble metal tip of the ground electrode with respect to the tip of the center electrode can be adjusted with high accuracy.
[0022]
In the adjusting process, for example, the tip of the ground electrode is deformed in the first specific direction, and the deviation of the center position of the ground electrode in the first specific direction with respect to the center position of the center electrode is adjusted to be within a predetermined range. Deviation adjustment step. Further, the tip of the ground electrode is pressed in the second specific direction, so that the gap dimension of the spark discharge gap formed between the tip of the noble metal tip of the ground electrode and the tip of the center electrode falls within a predetermined range. There is also a gap size adjusting step for adjusting.
[0023]
Another solution is a cylindrical insulator having an axial hole penetrating in the axial direction, and a center electrode inserted into the axial hole of the insulator, the tip protruding from the distal end surface of the insulator. A central electrode having a portion, a metal shell surrounding the periphery of the insulator, and a grounded electrode having a base end portion fixed to the metal shell, and a bent ground electrode, and the center of the inner surface facing the center electrode side. A spark electrode for an internal combustion engine, including a convex noble metal tip fixed at a position facing the tip of the electrode, and a ground electrode forming a spark discharge gap between the tip of the noble metal tip and the tip of the center electrode. An apparatus for manufacturing a plug, wherein the center electrode is on the near side, the base end of the ground electrode is on the back side, and an image is obtained in which the center electrode and the base end of the ground electrode overlap. Cameras placed and above Of the images taken by the camera, the tip image corresponding to the tip of the center electrode and the noble metal tip image corresponding to the noble metal tip of the ground electrode are silhouetted with respect to the background, An illuminating device for illuminating the engine spark plug, and, based on an image taken by the camera, position information obtaining means for obtaining relative position information between the tip of the center electrode and the noble metal tip of the ground electrode, It is a manufacturing apparatus for a spark plug for an internal combustion engine, comprising:
[0024]
The spark plug manufacturing apparatus for an internal combustion engine according to the present invention includes a spark plug having a ground electrode to which a convex noble metal tip is fixed at a position facing the tip of the center electrode, wherein the center electrode is on the front side, and the base end of the ground electrode. The camera has a camera arranged such that the portion is on the back side and an image in which the center electrode and the base end of the ground electrode overlap each other is obtained.
Furthermore, of the images taken by the camera, the illumination of the spark plug so that the tip image corresponding to the tip of the center electrode and the noble metal tip image corresponding to the noble metal tip of the ground electrode form a silhouette with respect to the background. It has a device. In the manufacturing apparatus of the present invention having such a camera and an illuminating device, the outline of the silhouette of the tip of the center electrode and the noble metal tip of the ground electrode is clarified by contrast with a bright background, and the image is formed at a time. Can be obtained by shooting.
[0025]
Further, the apparatus for manufacturing a spark plug for an internal combustion engine of the present invention has position information acquisition means for acquiring relative position information between the tip of the center electrode and the noble metal tip of the ground electrode based on an image taken by a camera. are doing. As described above, in the image captured by the camera of the present invention, the contours of the tip of the center electrode and the noble metal tip of the ground electrode are clear, and therefore, the position information acquisition unit of the present invention can be performed with high accuracy. It is possible to acquire relative position information of both. Furthermore, by using the relative position information, it is possible to appropriately carry out sorting of the spark plug for the internal combustion engine (sorting into a good product and a defective product), and adjustment processing of the position of the noble metal tip of the ground electrode with respect to the tip of the center electrode. You can also.
[0026]
Further, the spark plug manufacturing apparatus for an internal combustion engine as described above, wherein the lighting device illuminates a rear portion of the inner surface of the ground electrode, which is located on the back side with respect to the center electrode. It is good to use the manufacturing apparatus.
[0027]
The lighting device of the present invention illuminates the rear part of the ground electrode. As such a lighting device, for example, there is an optical fiber lighting that is disposed outside the space between the tip of the center electrode and the noble metal tip of the ground electrode and the ground electrode, and is directed toward the back of the ground electrode. . When the rear part of the ground electrode is illuminated by this lighting device, the reflected light at the rear part of the ground electrode is blocked by the tip of the center electrode and the noble metal tip of the ground electrode. As a result, it is possible to obtain an image in which the tip of the center electrode and the silhouette of the noble metal tip of the ground electrode are clarified with the back of the ground electrode as a bright background. This illuminating device does not need to be arranged in a narrow space between the tip of the center electrode and the noble metal tip of the ground electrode and the ground electrode, so that the illuminating device can have a simple structure. Further, since the rear part of the ground electrode is used as a screen for creating a bright background, there is no need to separately install a screen used as a bright background, and an inexpensive manufacturing apparatus is obtained.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment)
An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a side view of a spark plug 100 manufactured in the present embodiment. The spark plug 100 includes a cylindrical insulator 140, a center electrode 120 inserted therein, a metal shell 130 surrounding the insulator 140, and a ground electrode 110 fixed to the metal shell 130. The ground electrode 110 is fixed to the distal end surface 130 c of the metal shell 130 at the base end 111 and bent, and the facing portion 114 c of the inner side surface 114 faces the distal end 120 b of the center electrode 120. Further, a convex noble metal tip 113 is welded to the facing portion 114c of the inner side surface 114, and a spark discharge gap g is formed between the tip 113b of the noble metal tip 113 and the tip 120b of the center electrode 120. In the spark plug 100 of the present embodiment, the tip 120b of the center electrode is constituted by the tip of a noble metal tip 121 welded to the tip of the electrode body 122 made of a Ni alloy.
[0029]
FIG. 2 is a side view schematically showing the displacement dimension measuring device 250. As shown in FIG. 2, the displacement dimension measuring device 250 includes a first lighting device 253, a ground electrode chuck 255, a photographing camera 251, and a computer (not shown) connected thereto.
The ground electrode chuck 255 grips the distal end portion 112 of the ground electrode 110, rotates a formed spark plug (hereinafter, also referred to as a work) 101 around a central axis C, and adjusts the direction of the work 101 with respect to the photographing camera 251. (See FIG. 4).
The photographing camera 251 is, for example, a CCD camera. By adjusting the direction of the work 101 by the ground electrode chuck 255 as described above, the center electrode 120 of the work 101 is on the near side, and the base end 111 of the ground electrode 110 is on the near side. It is possible to acquire an image that is on the back side and in which the center electrode 120 and the base end 111 of the ground electrode 110 overlap.
[0030]
The first illumination device 253 is an optical fiber illumination, and illuminates a rear portion 114 b of the inner side surface 114 of the ground electrode 110 located on the back side of the center electrode 120 when the work 101 is viewed from the photographing camera 251. Are fixed to the lower end surface 255b of the ground electrode chuck 255. Further, in order to describe the first lighting device 253 in detail, FIG. 3 is a cross-sectional view taken along line AA of FIG. As shown in FIG. 3, two first lighting devices 253 are provided at positions symmetrical with respect to the center electrode 120, and each of the first lighting devices 253 is directed to the rear portion 114 b of the ground electrode 110 in the camera shooting direction (right in the drawing). Direction) is arranged so as to irradiate light in an oblique direction shifted by about 45 degrees. When the first lighting device 253 illuminates the rear portion 114b of the ground electrode 110, the reflected light from the rear portion 114b of the ground electrode 110 is blocked by the noble metal tip 121 of the center electrode 120 and the noble metal tip 113 of the ground electrode 110. As a result, an image in which the silhouettes of the noble metal tip 121 of the center electrode 120 and the noble metal tip 113 of the ground electrode 110 are clarified can be acquired by the photographing camera 251 with the back part 114b of the ground electrode 110 as a bright background ( (See FIG. 5).
[0031]
In this embodiment, a direction perpendicular to the central axis C of the metal shell 130 is defined as a first specific direction, and a direction along the central axis C of the metal shell 130 is defined as a second specific direction.
Based on such a photographed image, a specific position of the noble metal tip 113 of the ground electrode 110 (hereinafter, also referred to as a ground electrode specific position) and a specific position of the noble metal tip 121 of the center electrode 120 (hereinafter, a center electrode) are calculated by a computer (not shown). (Also referred to as a specific position). Specifically, in the present embodiment, the center position of the tip 113b of the noble metal tip 113 is determined as the ground electrode specifying position I6 (see FIG. 5C), and the center position of the tip 120b of the noble metal tip 121 is specified as the center electrode specifying. The position is determined as J6 (see FIG. 6C). Then, based on the ground electrode specific position I6 and the center electrode specific position J6 determined in this way, the deviation dimension P of the noble metal tip 113 of the ground electrode 110 with respect to the noble metal tip 121 of the center electrode 120 in the first specific direction is determined. It can be calculated (see FIG. 7).
[0032]
FIG. 8 is a side view schematically showing the deviation adjusting device 260. The displacement adjusting device 260 includes a bending member 261 that presses the distal end portion 112 of the ground electrode 110 in a first specific direction, a female screw portion 262 provided integrally therewith, and a male screw portion that is screwed with the female screw portion 262. 263 and a drive motor 264 for rotating the male screw portion 263 around the axis. In the deviation adjusting device 260, the male screw portion 263 is rotated around its axis by the drive motor 264, and the bending member 261 is moved in the first specific direction, so that the groove 261b formed in the bending member 261 is connected to the ground electrode. The front end 112 of the ground electrode 110 is pressed and deformed in the first specific direction while engaging with the front end 112 of the ground electrode 110. In this manner, the deviation of the noble metal tip 113 of the ground electrode 110 from the noble metal tip 121 of the center electrode 120 in the first specific direction can be adjusted. In the displacement adjusting device 260, the drive motor 264 is controlled so that the displacement size P becomes 0.0 mm using a computer (not shown) based on the displacement size P calculated by the displacement size measuring device 250. The drive rotation speed is calculated.
[0033]
Next, a method for manufacturing the spark plug 100 using these devices will be described. FIG. 9 is a flowchart (main routine) showing a flow of steps of a method of manufacturing the spark plug 100. First, in step S1 (work setting step), the work 101 is mounted on the work holder 210 (see FIG. 8) and fixed.
Next, the process proceeds to step S2 (deflection dimension measuring step), where the deviation dimension of the ground electrode 110 with respect to the center electrode 120 of the work 101 is measured. Specifically, the deflection dimension P of the noble metal tip 113 of the ground electrode 110 with respect to the noble metal tip 121 of the center electrode 120 in the first specific direction is measured by the deflection dimension measuring device 250 (see FIG. 2).
[0034]
Here, the subroutine of step S2 is shown in FIG. 10, and the deviation dimension measurement processing will be described in detail. First, in step S21, the ground electrode chuck 255 is lowered from above the work 101 (see FIG. 4A) and stopped at a predetermined position (see FIG. 4B). Next, the process proceeds to step S22, in which the tip portion 112 of the ground electrode 110 is gripped by the ground electrode chuck 255, the work 101 is rotated around the central axis C, and the work 101 with respect to the photographing camera 251 installed at a predetermined position. Is adjusted (see FIG. 4C). As a result, the photographing camera 251 can obtain an image in which the center electrode 120 is on the near side, the base end 111 of the ground electrode 110 is on the back side, and the center electrode 120 and the base end 111 of the ground electrode 110 overlap. Become. At the same time, the first lighting device 253 fixed to the lower end surface 255b of the ground electrode chuck 255 is arranged at a predetermined position (see FIG. 2).
[0035]
Next, the process proceeds to step S23, in which the first lighting device 253 is turned on, and the rear portion 114b of the ground electrode 110 is irradiated with light (see FIG. 3). Next, the process proceeds to step S24, in which an image in which the silhouettes of the noble metal tip 121 of the center electrode 120 and the noble metal tip 113 of the ground electrode 110 are clarified is shot by the shooting camera 251 with the back part 114b of the ground electrode 110 as a bright background ( (See FIG. 2). Next, the process proceeds to step S25, where an image captured by the camera 251 is captured (see FIG. 5A). As described above, in the present embodiment, both the noble metal tip 121 of the center electrode 120 and the noble metal tip 113 of the ground electrode 110 can acquire a clear image in one shot.
[0036]
In the present embodiment, steps S23 to S25 correspond to a photographing process. In this embodiment, in each image, the vertical direction (vertical direction in the figure) is the Y direction, and the horizontal direction (horizontal direction in the figure) is the X direction. In the present embodiment, the X direction matches the first specific direction, and the Y direction matches the second specific direction. Each of the images is a grayscale image in which a gray scale is set for each pixel.
[0037]
Next, the process proceeds to step S26, as shown in FIG. 5 (a), where the acquired image has a certain width in the Y direction and extends in the X direction in a region where the noble metal tip 113 of the ground electrode 110 is expected to be present. A band-shaped determination region I1 is set. Then, the tip position I2 is determined based on the density distribution in the Y direction obtained at each pixel position in the X direction. Next, the process proceeds to step S27, and as shown in FIG. 5B, a search line I3 is set at a position shifted from the tip end position I2 by a predetermined distance (for example, 0.1 mm) in the −Y direction (upward in the figure). I do. Then, a pixel density distribution in the X direction is obtained along the search line I3, and the coordinate values of the left end position I4 and the right end position I5 are determined based on the pixel density distribution. Then, the process proceeds to step S28, where the average value of the X coordinate values of the left end position I4 and the right end position I5 is Xi, the Y coordinate value of the tip end position I2 is Yi, and the coordinate value of the ground electrode center position I6 is (Xi, Yi). (See FIG. 5C). As described above, in the present embodiment, the coordinate value (Xi, Yi) of the ground electrode center position I6 is calculated based on the image in which the silhouette of the noble metal tip 113 of the ground electrode 110 is clarified. The coordinate value of the center position can be obtained.
[0038]
Next, the process proceeds to step S29, and as shown in FIG. 6 (a), the acquired image has a certain width in the Y direction in a region where the noble metal tip 121 constituting the tip 120b of the center electrode 120 is expected. Then, a band-shaped determination region J1 extending in the X direction is set. Then, the tip position J2 is determined based on the density distribution in the Y direction obtained at each pixel position in the X direction. Next, the process proceeds to step S2A, and as shown in FIG. 6B, a search line J3 is set at a position displaced from the tip end position J2 by a predetermined distance (for example, 0.1 mm) in the Y direction (downward in the figure). . Then, a pixel density distribution in the X direction is obtained along the search line J3, and coordinate values of the left end position J4 and the right end position J5 are determined based on the pixel density distribution. Next, the process proceeds to step S2B, where the average value of the X coordinate values at the left end position J4 and the right end position J5 is Xj, the Y coordinate value of the tip position J2 is Yj, and the coordinate value of the center electrode center position J6 is (Xj, Yj). (See FIG. 6C). As described above, in the present embodiment, the coordinate value (Xj, Yj) of the center electrode center position J6 is calculated based on the image in which the silhouette of the noble metal tip 121 of the center electrode 120 is clarified. The coordinate value of the center position can be obtained.
[0039]
Next, the process proceeds to step S2C, and as shown in FIG. 7, a ground electrode center line I8 passing through the ground electrode center position I6 and parallel to the Y axis is set. Then, based on the ground electrode center line I8, it is determined whether the X coordinate value of the center electrode center position J6 is on the left or right of the ground electrode center line I8, and the sign of the deviation dimension is determined. This sign defines the direction of bending of the ground electrode 110 in the subsequent step S4 (deflection adjustment step). Next, the distance between the ground electrode center line I8 and the center electrode center position J6 is calculated as the deviation dimension P of the noble metal tip 113 of the ground electrode 110 with respect to the noble metal tip 121 of the center electrode 120 in the first specific direction. Return to the main routine shown.
As described above, in the present embodiment, the deviation dimension P is calculated based on the highly accurate ground electrode center position I6 (Xi, Yi) and the center electrode center position J6 (Xj, Yj). The order dimension P can be obtained. In the present embodiment, steps S26 to S2C correspond to a position information acquisition step.
[0040]
Next, the process proceeds to step S3, and it is determined whether the deviation dimension P is within a predetermined tolerance range (for example, ± 0.15 (mm)). If it is within the predetermined tolerance range, the process proceeds to step S5 (work removal step), and the work 101 is taken out of the work holder 210. Thus, the spark plug 100 as shown in FIG. 1 is completed.
[0041]
On the other hand, when the deviation dimension P is out of the predetermined tolerance range, the process proceeds to step S4 (deflection adjustment step), and the noble metal of the ground electrode 110 with respect to the noble metal tip 121 of the center electrode 120 with respect to the workpiece 101. The tip 113 is adjusted so that the deflection dimension P of the tip 113 in the first specific direction falls within a predetermined range. More specifically, the direction in which the deviation dimension P is reduced using the deviation adjustment device 260 shown in FIG. 8 (the direction determined in step S2 (the deviation dimension measurement step). Bending is performed on the tip 112 of the ground electrode 110 (to the right). The amount of bending (the amount of movement of the bending member 261) is a value obtained by adding the amount of springback of the ground electrode 110 when the urging by the bending member 261 is released to the deviation dimension P. In this way, the deviation P of the noble metal tip 113 of the ground electrode 110 with respect to the noble metal tip 121 of the center electrode 120 in the first specific direction is adjusted to be 0.0 mm. In the present embodiment, step S4 (deviation adjustment step) corresponds to an adjustment processing step.
[0042]
Finally, the process proceeds to step S5 (work removal step), and the work 101 is removed from the work holder 210. Thus, the spark plug 100 as shown in FIG. 1 is completed.
[0043]
(Modified form)
Next, a modification of the manufacturing apparatus and the manufacturing method of the spark plug 100 according to the embodiment will be described with reference to the drawings. The manufacturing apparatus of the spark plug 100 according to the present modification is different from the manufacturing apparatus according to the embodiment in the deviation size measuring apparatus, and the other apparatuses are almost the same. Further, the manufacturing method of the spark plug 100 of the present modified embodiment is different from the manufacturing method of the embodiment in the step S2 (deviation dimension measuring step), and the other steps are almost the same. Specifically, a step of measuring the inclination of the work 101 is added, and the method of acquiring the center electrode center position and the coordinate value of the center electrode center position is changed. Therefore, the description will be focused on the parts different from the embodiment, and the description of the same parts will be omitted or simplified.
[0044]
FIG. 11 is a side view schematically showing the displacement dimension measuring device 350 according to the present modification. As shown in FIG. 11, the displacement dimension measuring device 350 further adds a second lighting device 352 and a background screen 354 to the displacement dimension measuring device 250 of the embodiment to measure the inclination of the work 101. In addition, a photographing camera unit 370 is arranged in place of the photographing camera 251. Therefore, the description of the same parts as those of the embodiment will be omitted or simplified.
The second illumination device 352 is a surface-emitting type LED or an LED illumination in which a large number of LEDs are arranged in a plane, and has a through hole 352b for securing a field of view of the photographing camera unit 370. Such a second illumination device 352 is provided so as to irradiate the work 101 with light in the shooting direction (right direction in the drawing) of the shooting camera unit 370 to illuminate the work 101.
[0045]
The imaging camera unit 370 includes a first camera 371, a second camera 372, an objective lens 373, a half mirror 374, a mirror 374b, a first image enlargement unit 375, and a second image enlargement unit 376.
Among them, in the first camera 371, the image is enlarged to the first magnification by the first image enlargement unit 375 via the objective lens 373, the half mirror 374, and the mirror 374 b in the order of the path B <b> 1 shown in FIG. 11. Take an image. When an image is captured by the first camera 371, the first lighting device 253 illuminates the rear portion 114b of the ground electrode 110 as in the embodiment (see FIG. 12B). For this reason, in the first camera 371, the silhouette of the noble metal tip 121 of the center electrode 120 and the silhouette of the noble metal tip 113 of the ground electrode 110 are clear with the back part 114 b of the ground electrode 110 as a bright background, similarly to the camera 251 of the embodiment. A converted image can be obtained (see FIG. 15). In this modification, the coordinate values of the ground electrode center position and the center electrode center position are calculated based on the image captured by the first camera 371 as described above.
[0046]
On the other hand, in the second camera 372, the second magnification is lower than the first magnification in the second image enlarging unit 376 via the objective lens 373 and the half mirror 374 in the order of the path B2 shown in FIG. Take an enlarged image. When an image is captured by the second camera 372, the work 101 is illuminated by the second illumination device 352 (see FIG. 12A). Therefore, the second camera 372 can obtain an image in which the contour of the metal shell 130 is clarified by contrast with the bright background unit 354 (see FIG. 13A). In the present modification, the inclination of the workpiece 101 is measured based on the image captured by the second camera 372 in this manner.
[0047]
Next, a method for manufacturing the spark plug 100 of the present modified example will be described.
FIG. 17 is a flowchart (main routine) illustrating a flow of steps of a method of manufacturing the spark plug 100. As shown in FIG. 17, the manufacturing method according to the present modification is obtained by changing the processing in step S2 of the embodiment to the processing in step T2, and the other parts are the same. Therefore, the description of the same parts as those of the embodiment will be omitted or simplified.
[0048]
First, as in the embodiment, the work 101 is set in step S1 (work setting step). Next, the process proceeds to step T2 (deviation dimension measuring step), where the deviation dimension of the ground electrode 110 with respect to the center electrode 120 of the work 101 is measured.
Here, the subroutine of step T2 is shown in FIG. 18, and the deviation dimension measurement processing will be described in detail. First, in steps T21 and T22, the tip 112 of the ground electrode 110 is gripped and fixed by the ground electrode chuck 255 in the same manner as steps S21 and S22 of the embodiment (see FIG. 4).
[0049]
Next, the process proceeds to step T23, where the second lighting device 352 is turned on, and the work 101 is irradiated with light. Next, proceeding to step T24, the second camera 372 captures an image in which the outline of the metal shell 130 is clarified by contrast with the bright background unit 354 (see FIG. 13A). Next, the process proceeds to step T25, where an image captured by the second camera 372 is captured.
[0050]
Next, the process proceeds to step T26, and the inclination of the work 101 is measured based on the image captured in step T25. Specifically, first, as shown in FIG. 13A, a determination area G5 having a certain width in the Y direction and extending in a band shape in the X direction so as to cross the metal shell 130 is set. Next, in the determination area G5, an X-direction density distribution is obtained for each pixel position in the Y direction, and the left and right end positions G1, G2 of the metal shell 130 are determined based on the density distribution. Next, as shown in FIG. 13B, search lines G3 and G4 extending in the Y direction are set at positions away from the left and right end positions G1 and G2 by a fixed number of pixels toward the center of the image in the X direction. Next, by determining the density distribution on the search lines G3 and G4, the tip surface positions G6 and G7 are determined, and a tip surface reference line L2 connecting the tip surface positions G6 and G7 is set. Then, as shown in FIG. 14, a work center line L1 orthogonal to the tip end surface reference line L2 is set, and an angle θ1 between the work center line L1 and a vertical line K1 extending in the vertical direction (Y-axis direction) is set. It is calculated as the inclination of the work 101.
[0051]
Next, proceeding to step T27, the second lighting device 352 is turned off, the first lighting device 253 is turned on, and light is applied to the rear portion 114b of the ground electrode 110 as in the embodiment (see FIG. 3). Next, the process proceeds to steps T28 and T29, and the silhouettes of the noble metal tip 121 of the center electrode 120 and the noble metal tip 113 of the ground electrode 110 are set in the same manner as in steps S24 and S25 of the embodiment with the back part 114b of the ground electrode 110 as a bright background. Then, a photographed image H in which is clearly obtained is acquired (see FIG. 15).
In this modification, steps T27 to T29 correspond to a photographing process.
[0052]
Next, the process proceeds to step T2A, and as shown in FIG. 15, first, the model image M2 of the precious metal chip 113 registered in advance is moved in parallel on the photographed image H acquired in step T29. Then, a density difference between corresponding pixels between the model image M2 and the photographed image H is calculated, and the total is calculated. The model image M2 is positioned at a position where the sum of the density differences calculated in this manner is minimized. Next, the coordinate value of the center position M1 of the tip of the positioned model image M2 is obtained, and this is determined as the coordinate value (Xm, Ym) of the center position M6 of the ground electrode. Next, the process proceeds to step T2B, and the coordinate value of the center electrode center position N6 is determined as (Xn, Yn) using a model image (not shown) in the same manner (see FIG. 16).
[0053]
Next, the process proceeds to step T2C, where a ground electrode center line L3 that passes through the ground electrode center position M6 and is inclined by an angle θ1 with respect to the vertical line K1 is set as shown in FIG. Then, based on the ground electrode center line L3, it is determined whether the X coordinate value of the center electrode center position N6 is on the left or right of the ground electrode center line L3, and the sign of the deviation dimension is determined. This sign defines the direction of bending of the ground electrode 110 in the subsequent step S4 (deflection adjustment step). Next, the distance between the ground electrode center line L3 and the center electrode center position N6 is calculated as the deviation dimension P of the noble metal tip 113 of the ground electrode 110 with respect to the noble metal tip 121 of the center electrode 120 in the first specific direction, and FIG. Return to the main routine shown.
[0054]
As described above, in the present modification, the inclination θ1 of the work 101 is measured, and the deviation dimension P is calculated in consideration of the inclination θ1. Therefore, in the present modification, even when the workpiece 101 is inclined with respect to the reference direction (vertical direction), the deviation dimension P can be acquired with high accuracy. In the present embodiment, steps T2A to T2C correspond to a position information acquisition step.
Next, the processes in steps S3 to S5 are performed in the same manner as in the embodiment, and the spark plug 100 as shown in FIG. 1 is completed.
[0055]
In the above, the present invention has been described with reference to the embodiments and the modified embodiments. However, the present invention is not limited to the above embodiments and the like, and it can be said that the present invention can be appropriately modified and applied without departing from the gist thereof. Not even.
For example, in the embodiment and the like, after Steps S2 and T2 (deviation dimension measurement step), the process proceeds to Step S3 to determine whether the deviation dimension P is within a predetermined tolerance range (for example, ± 0.15 (mm)). Has been determined. However, step S4 (deviation adjustment step) may be performed on all the workpieces 101 without determining whether or not the deviation dimension P is within a predetermined tolerance range. In this way, the workpieces 101 can be sent at regular intervals on the production line.
[0056]
In the embodiment, the coordinate values (Xi, Yi) of the ground electrode center position I6 and the coordinate values (Xj, Yj) of the center electrode center position J6 are determined by the processes of steps S26 to S2B. Alternatively, it may be determined by the processing of steps T2A and T2B. On the contrary, in the modified embodiment, the coordinate values (Xm, Ym) of the ground electrode center position M6 and the coordinate values (Xn, Yn) of the center electrode center position N6 are determined by the processes of steps T2A and T2B. As in the embodiment, the determination may be made by the processing of steps S26 to S2B.
[0057]
In the embodiment and the like, step S4 (deviation adjustment step) is provided as an adjustment processing step, but another adjustment processing step may be provided. For example, the tip 112 of the ground electrode 110 is pressed in the second direction, and the gap size of the spark discharge gap g formed between the tip 113b of the noble metal tip 113 of the ground electrode 110 and the tip 120b of the center electrode 120 is determined. A gap size adjustment step of adjusting the size of the gap to fit within the range may be provided. In the gap dimension adjusting step, when a direction orthogonal to the first specific direction and the second specific direction (for example, a direction orthogonal to the plane of FIG. 5) is set as a third specific direction, center electrode center positions J6 and N6. The gap dimension is adjusted while regulating the position of the tip end surface 112c of the ground electrode 110 in the third specific direction so that the positions of the ground electrode center positions I6 and M6 in the third specific direction are within a predetermined range. May be.
[0058]
Also, a cover adjustment step of deforming the ground electrode 110 in the third specific direction and adjusting the position of the ground electrode with respect to the center electrode in the third specific direction to fall within a predetermined range may be provided.
Further, after step S4 (deviation adjustment step), a deviation dimension measurement step may be performed to check whether the deviation dimension P of the work 101 is within a predetermined dimension range. good. Further, when the deviation dimension P of the workpiece 101 measured in the deviation dimension measuring step is out of the predetermined dimension range, the deviation adjusting step may be performed again.
[Brief description of the drawings]
FIG. 1 is a side view of a spark plug 100 according to an embodiment.
FIG. 2 is a side view schematically illustrating a displacement dimension measuring device 250 according to the embodiment.
FIG. 3 is a cross-sectional view taken along line AA of FIG. 2 and is an explanatory diagram illustrating an illumination method using a first illumination device 253.
FIG. 4 is an explanatory diagram illustrating a chuck of a ground electrode 110 in a displacement dimension measuring step according to the embodiment.
FIG. 5 is an explanatory diagram illustrating a method for measuring a ground electrode center position I6 in a displacement dimension measuring step according to the embodiment.
FIG. 6 is an explanatory diagram illustrating a method for measuring a center electrode center position J6 in a displacement dimension measuring step according to the embodiment.
FIG. 7 is an explanatory diagram illustrating a method of measuring a deviation dimension P in a deviation dimension measuring step according to the embodiment.
FIG. 8 is a side view schematically showing a deviation adjusting device 260 according to the embodiment.
FIG. 9 is a flowchart showing a process flow of a method for manufacturing a spark plug 100 according to the embodiment.
FIG. 10 is a flowchart illustrating a flow of a deviation dimension measuring process according to the embodiment.
FIG. 11 is a side view schematically showing a displacement dimension measuring device 350 according to a modified embodiment.
FIG. 12 is an explanatory diagram illustrating a deviation dimension measuring step according to a modified embodiment.
FIG. 13 is an explanatory diagram illustrating a method of measuring the inclination of the work 101 in a displacement dimension measuring step according to a modified embodiment.
FIG. 14 is an explanatory diagram illustrating a method for measuring the inclination of the workpiece 101 in a displacement dimension measuring step according to a modified embodiment.
FIG. 15 is an explanatory diagram illustrating a method of measuring a ground electrode center position M6 in a displacement dimension measuring step according to a modified embodiment.
FIG. 16 is an explanatory diagram illustrating a method of measuring a deviation dimension P in a deviation dimension measuring step according to a modified embodiment.
FIG. 17 is a flowchart showing a process flow of a method for manufacturing a spark plug 100 according to a modified embodiment.
FIG. 18 is a flowchart illustrating a flow of a deviation dimension measurement process according to a modified embodiment.
[Explanation of symbols]
100 spark plug
101 Work
110 Ground electrode
111 Base end of ground electrode
113 Noble metal tip for ground electrode
113b Tip of precious metal tip
114 Inner surface of ground electrode
114b Back of inner surface
120 center electrode
120b Tip of center electrode
121 Noble metal tip for center electrode
130 Metal fitting
130c Tip of metal shell
140 insulator
251 Camera
253 First lighting device
352 Second lighting device
370 camera unit
371 First camera
372 Second camera
C Central axis of metal shell
g spark discharge gap
P deviation dimension

Claims (7)

A cylindrical insulator having an axial hole penetrating in the axial direction,
A center electrode inserted into the shaft hole of the insulator, the center electrode having a tip protruding from a tip surface of the insulator,
A metal shell surrounding the insulator;
A base end portion is fixed to the metal shell, and is a bent ground electrode, including a convex-shaped noble metal tip fixed at a position facing the tip of the center electrode on the inner side surface facing the center electrode side. A ground electrode that forms a spark discharge gap between the tip of the noble metal tip and the tip of the center electrode;
A method for manufacturing a spark plug for an internal combustion engine having
In a state where the camera is arranged such that the center electrode is on the near side, the base end of the ground electrode is on the back side, and an image in which the center electrode and the base end of the ground electrode overlap each other is obtained, Of the images captured by the camera, the tip image corresponding to the tip of the center electrode and the noble metal tip image corresponding to the noble metal tip of the ground electrode are illuminated so as to be silhouetted with respect to the background. A photographing step of photographing the noble metal tip of the tip portion of the center electrode and the ground electrode,
Based on the image obtained in the photographing step, a position information obtaining step of obtaining relative position information between the tip of the center electrode and the noble metal tip of the ground electrode,
A method for manufacturing a spark plug for an internal combustion engine, comprising: A method for manufacturing a spark plug for an internal combustion engine according to claim 1,
The method of manufacturing a spark plug for an internal combustion engine, wherein the photographing step includes photographing a rear portion of the inner side surface of the ground electrode, which is located on the rear side relative to the center electrode, with a lighting device. A method for manufacturing a spark plug for an internal combustion engine according to claim 1 or claim 2,
The relative position information is a distance in a specific direction between a ground electrode specific position extracted from the noble metal tip image and a center electrode specific position extracted from the tip image,
In the position information obtaining step, an internal combustion engine that calculates a distance in the specific direction based on a coordinate value of the ground electrode specific position on the image and a coordinate value of the center electrode specific position on the image For manufacturing spark plugs for automobiles. It is a manufacturing method of the spark plug for internal combustion engines according to claim 3,
The ground electrode specific position is a ground electrode center position which is a center position in the width direction of the tip of the noble metal tip image,
The center electrode specific position is a center electrode center position which is a center position in the width direction of the tip of the tip image,
The specific direction is a first specific direction that is a direction orthogonal to a central axis of the metal shell on the image,
The method for manufacturing a spark plug for an internal combustion engine, wherein the distance in the specific direction is a deviation of the center position of the ground electrode from the center position of the center electrode in the first specific direction. A method for manufacturing a spark plug for an internal combustion engine according to any one of claims 1 to 4,
A method for manufacturing a spark plug for an internal combustion engine, comprising an adjustment processing step of deforming the ground electrode based on the relative position information and adjusting a position of the noble metal tip of the ground electrode with respect to the tip of the center electrode. A cylindrical insulator having an axial hole penetrating in the axial direction,
A center electrode inserted into the shaft hole of the insulator, the center electrode having a tip protruding from a tip surface of the insulator,
A metal shell surrounding the insulator;
A base end portion is fixed to the metal shell, and is a bent ground electrode, including a convex-shaped noble metal tip fixed at a position facing the tip of the center electrode on the inner side surface facing the center electrode side. A ground electrode that forms a spark discharge gap between the tip of the noble metal tip and the tip of the center electrode;
An apparatus for manufacturing a spark plug for an internal combustion engine having
A camera arranged such that the center electrode is on the near side, the base end of the ground electrode is on the back side, and an image in which the center electrode and the base end of the ground electrode overlap each other is obtained,
Of the images captured by the camera, the tip image corresponding to the tip of the center electrode and the noble metal tip image corresponding to the noble metal tip of the ground electrode are silhouetted with respect to the background, A lighting device for illuminating a spark plug for an internal combustion engine,
Based on an image taken by the camera, position information acquisition means for acquiring relative position information between the tip of the center electrode and the noble metal tip of the ground electrode,
An apparatus for manufacturing a spark plug for an internal combustion engine, comprising: An apparatus for manufacturing a spark plug for an internal combustion engine according to claim 6,
The lighting device may be a device for manufacturing a spark plug for an internal combustion engine that illuminates a rear portion of the inner surface of the ground electrode that is located on the back side of the center electrode with respect to the back side.

Images