JP2003297525A - Manufacturing method of spark plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a spark plug capable of easily deciding on a fitting position for a grounding electrode to a main metal fitting which satisfies a given positioning relationship with a screw-thread starting position, without the use of a specific jig. <P>SOLUTION: A fitting screw part 57 is formed on an outer periphery face of a main metal fitting work 51 before a grounding electrode 54 is fitted. Next, an image of the main metal fitting work is photographed so that the fitting screw part 57 comes within an image field of view VA, then, based on the work image, the grounding electrode mounting position is decided so as to satisfy a given angle relation with the screw-thread starting position. At that decided mounting position, the grounding electrode is mounted on the main metal fitting work 51. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

The present invention relates to a method for manufacturing a spark plug.

[0002]

2. Description of the Related Art In recent years, due to higher performance or lean burn of internal combustion engines, the certainty of igniting an air-fuel mixture has become more and more important. In this case, the mounting position of the spark plug in the combustion chamber is an important factor that influences the ignitability.
For example, when the spark discharge gap is behind the ground electrode or the ground electrode exists in a direction that hinders flame growth with respect to the direction of the swirl generated by the air-fuel mixture sucked into the combustion chamber, the spark plug ignitability is improved. It has been pointed out that it may cause a decrease. Therefore, it has been proposed to adjust the direction of the ground electrode in the combustion chamber, which has been different in the past, to an optimum position in consideration of ignitability. The spark plug is mounted on the internal combustion engine by screwing a mounting screw portion formed on the metal shell into a screw hole on the internal combustion engine side, but the tightening torque of the mounting screw portion is limited. Therefore, in order to make the direction of the ground electrode constant in the mounted state, the position of mounting the ground electrode on the metal shell should be aligned so as to satisfy a certain angular relationship with the screw thread starting position of the mounting screw. I have to go.

In a mass production line of spark plugs, a mounting screw portion of a metal shell is formed by rolling with high working efficiency. However, it is not easy to perform rolling on the metal shell to which the ground electrode is attached in such a manner that the starting position of the screw thread is aligned with the attachment position of the ground electrode. Therefore,
In Japanese Patent Laid-Open No. 11-13613, a nut-shaped jig is screwed onto a metal shell after thread rolling, and a mounting position given to the jig that satisfies a certain positional relationship with a thread start position. A method of mounting the ground electrode with reference to the mark is disclosed.

[0004]

However, in the method disclosed in the above publication, a jig must be screwed to the metal shell each time the ground electrode is mounted, and the ground electrode mounting is completed. Since the jig must be removed later, there is a drawback that the number of steps increases. Further, in order to smoothly carry out mass production, it is necessary to prepare a considerable number of jigs, and when the ground electrode attachment position differs depending on the specifications of the internal combustion engine, it is necessary to prepare jigs with different mark positions. is there. In any case, the cost will increase as much as the jig must be prepared.

An object of the present invention is to provide a method for manufacturing a spark plug which can easily determine a ground electrode mounting position on a metal shell that satisfies a certain positional relationship with a screw thread starting position without using a special jig. To provide.

[0006]

According to the method for manufacturing a spark plug of the present invention, a mounting seat portion in the circumferential direction is formed so as to project at an axially intermediate position on the outer peripheral surface, and the mounting seat portion is connected to the mounting seat portion. It has a tubular metal shell with a mounting screw part formed, and is located at the reference angular position determined in the circumferential direction of the mounting screw part when the mounting screw part is tightened to the limit position specified by the mounting seat part. On the other hand, according to a method for manufacturing a spark plug in which a ground electrode is attached to an end surface of a metal shell at a ground electrode attachment position satisfying a certain angular relationship, in order to solve the above-mentioned problems, a first aspect thereof is a ground electrode attachment Image of the metallic shell work by the camera so that the mounting screw part forming process of forming the mounting screw part on the outer peripheral surface of the previous metallic shell work and the mounting seat and at least part of the mounting screw part appear in the image field of view. (Hereafter, work Image) and grasp the angle phase of the mounting screw part with respect to the camera based on the work image, and based on the grasping result, the angle relation of the ground electrode to the metal shell work is satisfied. And a ground electrode attaching step.

According to the first aspect of the present invention, after the mounting screw portion is formed on the outer peripheral surface of the metal shell work, the mounting seat portion and at least a part of the mounting screw portion appear in the image visual field. An image of the metal shell work (work image) is photographed by the camera, and based on the work image, the screw thread phase for grasping the angular phase of the mounting screw portion with respect to the camera is grasped. Then, based on the grasped result, the ground electrode was attached to the metal shell work so as to satisfy the angular relationship. Therefore, a special jig for determining the ground electrode attachment position as disclosed in Japanese Patent Laid-Open No. 11-13613 is not necessary, and naturally, the number of steps for attaching and detaching the jig is not required, which is efficient. .

For example, a master image obtained by photographing a standard metal shell product having a mounting screw portion formed at a camera angle whose positional relationship with a ground electrode mounting position is known is prepared.
In the attaching position specifying step, in the thread phase grasping step, the work image is photographed while the camera and the metal shell work are relatively rotated, and the pattern matching processing is performed between the master image and the image in the pattern matching processing. The angle phase between the matching camera and the metal shell work can be found, and the ground electrode attachment position can be determined based on the angle phase. When the image of the metal shell is taken so that the ground electrode attachment position faces the specific direction with respect to the camera angle, a significant difference occurs between the image of the metal electrode attachment position deviated from the specific direction. Therefore,
If the pattern matching process is performed between the metalwork work and the camera while rotating the metalwork and the master image where the ground electrode attachment position is known, the current ground electrode attachment position of the metalwork workpiece will be the ground electrode attachment in the master image. It is possible to easily determine whether or not there is a match with the position. Then, by finding the direction of the metallic shell work in which the images of the both agree with each other, the ground electrode attachment position can be easily determined.

In this case, as the work image and the master image, a metal shell work or a standard metal shell product obtained by photographing the outer peripheral surface on which the mounting screw portion is formed from the front direction can be used. Then, on the seating surface of the mounting seat portion of the metal shell work, a reference diameter position is set at a position that is separated from the axis of the metal shell work by a certain length in the radial direction, and the master image is a standard metal shell product. It is possible to use a photographed image in which the reference diameter position is adjusted to the target position in the image field. Then, on the work image, the metal shell work is translated in the image field of view so that the reference diameter position is aligned with the target position, and then the pattern matching process is performed while rotating the metal shell work around the axis. Thus, the ground electrode attachment position can be determined based on the rotation angle phase of the metal shell work in which the master image and the work image match. Since the reference diameter position appearing on the image does not change even if the work rotates, this can be used to align the work image with the master image in the axial direction. After that, pattern matching to the master image can be performed only by rotating the metal shell work around the axis, and the ground electrode mounting position can be easily and accurately determined based on the rotation angle phase of the metal shell work at that time. can do.

A second aspect of the method for manufacturing a spark plug of the present invention is that a mounting seat portion in the circumferential direction is formed so as to project at an intermediate position in the axial direction of the outer peripheral surface, and the mounting screw is continued to the mounting seat portion. Having a tubular metallic shell in which the portion is formed, and with the mounting screw portion tightened to the limit position specified by the mounting seat portion, with respect to the reference angular position determined in the circumferential direction of the mounting screw portion, In order to solve the above problems in the method of manufacturing a spark plug that attaches the ground electrode to the end surface of the metal shell at the ground electrode mounting position that satisfies a certain angle relationship, in order to solve the above problems, it is mounted on the outer peripheral surface of the metal shell workpiece before mounting the ground electrode. The mounting screw part forming step of forming the screw part and the metal shell work in which the mounting screw part is formed are held so that movement in the direction intersecting the axis is restricted and rotation about the axis is possible, while mounting Is it the seat of the seat? When a sensor that detects the thread of the mounting screw is placed at a specific angular position around the axis at a position that is a predetermined distance away from the mounting screw, and the metal shell work is rotated around the axis in that state. Based on the detection state of the sensor, the screw thread phase grasping process that grasps the angle phase of the mounting screw part with respect to the sensor, and based on the grasping result, attach the ground electrode to the metal shell work so as to satisfy the angle relationship. And an electrode mounting step.

In the second aspect of the present invention, the screw thread of the mounting screw portion is detected at a specific angular position around the axis at a position separated from the seat surface of the mounting seat portion by a certain length toward the mounting screw portion. Place the sensor to be used. After forming the mounting screw portion on the outer peripheral surface of the metal shell work, the metal shell work is rotated around the axis, and the angular phase of the mounting screw portion with respect to the sensor is grasped based on the detection state of the sensor. Then, based on the grasped result, the ground electrode is attached to the metal shell work so as to satisfy the angular relationship. As a result, there is no need for a special jig for determining the ground electrode attachment position as disclosed in Japanese Patent Laid-Open No. 11-13613, and of course, the number of steps for attaching and detaching the jig is not required, which is efficient. is there.

The metal shell work is rotated around the axis, the rotation of the metal shell work is stopped when the mounting screw portion reaches a specific rotation angle phase, and the metal shell work at the rotation angle phase at the time of stop is stopped. It is possible to arrange a ground electrode welding device at a position corresponding to the ground electrode attachment position, and perform welding of the ground electrode on the spot of the metal shell work that has stopped rotating by the welding device. With this configuration, the ground electrode can be welded extremely quickly after the ground electrode mounting position is determined, which contributes to the improvement of the manufacturing efficiency of the spark plug.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a schematic block diagram showing an example of a spark plug manufacturing apparatus for carrying out the first aspect of the present invention. The metal shell work 51 applied to the manufacturing apparatus 1 is formed in a tubular shape, and a mounting screw portion 57 is formed by rolling on the outer peripheral surface on one end side. Further, a flange-shaped mounting seat 52, a hexagonal portion 55, and a portion to be caulked 49 are formed in this order adjacent to the mounting screw portion 57. Then, so that the mounting screw portion 57 faces upward,
The cup-shaped holder 10 is detachably mounted so that the axis O coincides with it. The holder 10 is a lifting table 20.
On the upper side, by the rotation motor 18, the metal shell work 5
It is driven to rotate around the axis O together with 1. Further, the lifting table 20 drives the metal shell work 51 together with the holder 10 to move up and down. Various types of lifting mechanisms are known, and any one of them may be adopted, but in the present embodiment, it is configured as follows. That is, the screw shafts 21 are respectively screwed into the plurality of female screw portions 22 provided so as to penetrate the lifting table 20. Also,
Worms 23 are engaged with gears 24 concentrically provided on the screw shafts 21, respectively. These worms 23
Is driven to rotate by the lifting motor 17 via the shaft 25, the screw shafts 21 synchronously rotate to lift the lifting table 20.

Further, there is provided a digital camera 27 for photographing the outer peripheral surface of the metal shell work 51 on which the mounting screw portion 57 is formed from the front direction. In addition, the end surface 51 of the metal shell work 51 on the side where the mounting screw portion 57 is formed
a welding device 26 for resistance welding the ground electrode 54 to a.
Are arranged.

The manufacturing apparatus 1 also has a control device 10. The control device 10 is mainly composed of a computer having a CPU 8, a ROM 7, a RAM 6 and an input / output interface 9.
The digital camera 27 and the welding device 26 are connected to each other. Also, the rotation motor 18 and the lifting motor 1
7 is connected to the input / output interface 9 via the servo controllers 14 and 13, respectively. The rotation angle position of each motor 18, 17 is the pulse generator 1
6, 15 are detected. The servo controllers 14 and 13 recognize the current angular position based on the detection pulse signal, and voluntarily perform motor positioning and rotation speed control (the electrical configuration of which is well known, and therefore detailed description thereof is omitted). Further, the control device 10 refers to the detection pulse signal to grasp the rotation angle phase of the metal shell work 51 around the axis O and the position in the direction of the axis O.

The CPU 8 of the control unit 10 is a ROM
By executing the control program 7a stored in 7, the rotation motor 18 and the raising / lowering motor 17 rotate and raise / lower the metal shell work 51, the digital camera 27 captures an image and controls the capturing thereof, and a welding device. It controls 26 operations. Further, by executing the image analysis program 7b, the image analysis process necessary for determining the ground electrode attachment position, including the pattern matching process of the master image data 7c described later and the work image by a well-known method, is managed. . The RAM 6 is the CPU 8
It provides a work area for executing the program.

An embodiment of a spark plug manufacturing method using the manufacturing apparatus 1 will be described below. First, the metallic shell work 51 is attached to the holder 10, and an image is taken by the digital camera 27 so that the mounting screw portion 57 appears in the image visual field VA as shown in FIG. On the seat surface 53 of the mounting seat portion 52 of the metal shell work 51, a reference diameter position SP is set at a position spaced apart from the axis O of the metal shell work 51 by a certain length in the radial direction. The master image is a standard image of the metal shell, which is photographed with the reference diameter position SP aligned with the target position AP in the image field VA. The master image data 7c is stored in the ROM 7 of FIG.
It is prepared as.

The welding device 26 of FIG. 1 has a welding electrode 127 for holding the ground electrode 54 and conducting electricity for resistance welding. The welding electrode 127 holds the ground electrode 54 at an angular position fixedly fixed around the axis O (hereinafter, referred to as a welding execution position) with respect to the end surface 51a of the metal shell work 51, and waits for welding. is doing. The ground electrode attachment position of the metal shell work 51 is aligned with the ground electrode 54 held by the welding electrode 127,
The ground electrode 54 is joined by resistance welding. The ground electrode mounting position has a fixed angle with the reference angle position when the reference angle position is determined in the circumferential direction of the mounting screw part with the mounting screw part tightened up to the limit position defined by the mounting seat 53. Determined to satisfy the relationship. As for the reference angular position, if the spark plug has the same specifications, what kind of standard angle position can be used if it can be grasped as a substantially constant angular position with the spark plug tightened in the screw hole of the internal combustion engine? Good. For example, the reference diameter position SP on the seat surface 53
The angular position of the first full thread can be used such that the height from is a certain value H. The master image is a state where the standard metal shell is mounted on the holder 10 and the ground electrode mounting position thereof is adjusted to a predetermined angular position, that is, the welding execution position of the ground electrode 54 by the welding device 26,
It is obtained by photographing under the same photographing condition as the metal shell work 51.

In FIG. 2, the reference radial position SP is defined on the seat surface 53 of the mounting seat portion 52 (that is, the seat surface 5).
3 is a predetermined position on the axis). The outer peripheral surface of the mounting seat portion 52 is a cylindrical surface centered on the axis of the metal shell, and the seat surface 53 is flat in FIG. Although the axis does not appear on the image visual field VA, the fact that the radial distance from the axis to the reference radial position SP is constant means that the radial distance from the outer peripheral surface of the mounting seat portion 52 is also a constant value ΔD. Means
Therefore, the seat surface 53 and the outer peripheral surface of the mounting seat portion 52 are specified on the image by a known image processing method, and the reference diameter position SP is set on the seat surface 53 at a position where the distance from the outer peripheral surface is ΔD. Can be determined. All of these image processes are shown in FIG.
Image analysis program 7b. Note that, as shown in FIG. 3, the seat surface 53 may be formed in a tapered surface shape. Also in this case, the reference diameter position SP can be determined by the same image processing as above.

Subsequently, as shown in FIG. 2, the metal shell work 51 is translated in the image field VA to align the reference diameter position SP with the target position AP. In the present embodiment, the angle of the digital camera 27 is fixedly set so that the positional relationship between the axis O of the metal shell 51 (that is, the rotation axis of the holder 10 in FIG. 1) and the image visual field VA becomes constant. There is. The horizontal coordinate of the target position AP is made to coincide with the horizontal position of the reference diameter position SP from the beginning. Therefore, if the elevating motor 17 of FIG. 1 is operated to elevate and lower the metal shell work 51, the reference diameter position SP
Moves in the direction of the axis O (vertical direction) within the image visual field VA. Then, when the reference diameter position SP coincides with the target position AP, the elevating and lowering of the metallic shell work 51 is stopped, and the fitting process ends.

Next, in this state, the rotation motor 1 shown in FIG.
The metal shell work 51 is rotated around the axis O by 8. Then, as shown in FIG. 2, the image of the metallic shell work 51 rotates within the image field of view VA. While advancing this rotation by a small angle, pattern matching processing is performed between the work image and the master image that are captured each time. Then, when the sum of the density differences between the pixels is minimized, it is determined that the two images match, and the rotation of the metal shell work 51 is stopped.

In this state, the ground electrode mounting position of the metal shell work 51 is aligned with the ground electrode mounting position of the standard metal shell product when the master image was taken (that is, based on the work image. The angular phase of the mounting screw portion 57 with respect to the camera 27 is known).
Then, the ground electrode attachment position is positioned at the welding execution position described above. That is, the ground electrode attachment position was determined through the rotation of the metal shell work 51 and the pattern matching process with the master image.

Then, in the manufacturing apparatus 1, the welding device 26 continues to attach the ground electrode 54 to the positioned ground electrode attachment position by welding.
The metal shell 51 work piece to which the ground electrode 54 is attached is
As shown in FIG. 13, the insulator 2 with the center electrode 53 assembled therein is inserted therein, and the caulking portion 49 is caulked toward the insulator 2 for fixation. Further, the ground electrode 54 is bent toward the center electrode 53,
The spark plug 100 can be formed by forming the spark discharge gap g.
Is completed.

As shown in FIG. 2, in this embodiment, the master image is formed on one side of the mounting screw portion 57 in the radial direction.
Of the outlines of a plurality of complete threads arranged in the axial direction (threads in the section where the screw outer diameter is constant), the one that is closest to the mounting seat portion 52 (in FIG. 2, the mounting seat portion 5 is the closest).
Full thread close to 2: 5)
7f and the mounting seat 52 are photographed so as to appear in the image visual field VA. Under the leading complete thread 57f, a thread does not appear, or even if it appears, an incomplete thread 57i formed at the thread start end and having a thread height lower than this appears. Become. When the metal shell 51 is rotated around the axis O, the incomplete thread 57
As the height of i changes,
On the image, the position appears to move along the axial direction O. When the work image including the head complete screw thread 57 is used, when the ground electrode mounting position is displaced,
There is an advantage that the difference on the image from the master image is likely to appear clearly, and the ground electrode attachment position using the pattern matching process can be determined with high accuracy.

On the other hand, as shown in FIG. 4, the master image may be taken so that the screw thread starting position 57t near the mounting seat 52 appears in the image visual field VA. In FIG. 4, the axis O of the metal shell work 51 is positioned at a predetermined horizontal position within the image visual field VA, and the seat surface 53 is also positioned at a designated vertical position.
In the image visual field VA, an incomplete thread 57i appears in the image following the thread start position 57t. When the metal shell 51 is rotated around the axis O, the screw thread starting position 57t becomes, together with the image area of the incomplete screw thread 57i,
It moves within the image field of view VA. Since the shape of the image area of the incomplete screw thread area 57i is greatly different from the shape of the image area of the complete screw thread area, when the ground electrode attachment position is deviated, the difference in the image from the master image becomes clear. Easy to appear.

Various modifications of the first aspect of the present invention will be described below. When a work image obtained by photographing the outer peripheral surface of the metal shell work on which the mounting screw portion is formed is photographed from the front direction, the reference position is set on the seat surface 53 of the mounting seat portion 52 on the work image. Based on the distance from the reference position, although it is located in a specific order from the starting point of the thread, among the outlines of the complete threads that are arranged in the axial direction on the radial side of the mounting thread. The angle phase of the mounting screw portion 57 can be grasped. According to this method, a specific complete thread is identified on the image without using the pattern matching processing that requires time for image processing, and the distance from the reference position on the metal shell work to the complete thread is Since the angular phase of the mounting screw portion 57 and thus the ground electrode mounting position can be determined, there is an advantage that the burden of image processing can be reduced. FIG. 5 shows an example thereof. As the reference position, the above-mentioned reference diameter position SP is adopted, and as the complete screw thread, the above-mentioned leading complete screw thread 57f is adopted. However, if the screw thread order counted from this head complete screw thread 57 can be grasped, the head complete screw thread 5
It is also possible to use any of the complete threads from 7 onwards. In this aspect, the ground electrode attachment position is determined by the distance between the apex TP of the head complete screw thread 57f and the reference diameter position SP (the distance is not limited to the axial distance). I have to. Since it is only necessary to know the distance from the reference position on the metal shell work to a certain complete thread, the process of aligning the reference diameter position SP with the target position within the image visual field VA is not necessary.

Further, in FIG. 7, the head complete thread 5
An example is shown in which an edge determination line (or window) EL that crosses 7f in the axial direction is set and the position of the edge E1 (or E2) of the head complete thread 57f appearing on the edge determination line is detected. Reference diameter position SP of the edge position
The ground electrode attachment position can be determined by the distance from.

Further, the work image shows the outer peripheral surface on which the mounting screw portion of the metal shell work is formed so that the incomplete screw portion formed on the thread start position side of the mounting screw portion appears in the image visual field. It is also possible to use the one obtained by photographing from the front direction. And. It is possible to determine the ground electrode attachment position based on the image information of the incomplete screw portion appearing in the work image. A specific example is shown below. In FIG. 7, a plurality of threads arranged in the axial direction are photographed on one side in the radial direction of the mounting screw portion 57. In, the thread outline is not shown below the head complete thread 57f. However, when the metal shell work 51 is rotated around the axis O, as shown in, the incomplete thread 57
The outline of i extends in a direction orthogonal to the axial direction. Then, as shown in, the tip 57e of the incomplete thread 57i is, for example, a predetermined reference line DL defined parallel to the axis O (in the present embodiment, at a position forming a constant distance L1 from the reference diameter position SP). (Set) has been reached, it is determined that the alignment of the ground electrode attachment position has been completed. When the metal shell work 51 is rotated around the axis O, the incomplete thread 57i changes not only the extension height in the direction orthogonal to the axis direction but also the area occupied in the image visual field VA. Therefore, the completion of the alignment of the ground electrode attachment position may be grasped by the area ratio.

(Embodiment 2) An embodiment of the second aspect of the present invention will be described focusing on the differences from the first aspect. FIG. 8 is a schematic block diagram showing an example of a spark plug manufacturing apparatus for carrying out the second aspect of the present invention. The same points as those in FIG. 1 are assigned the same reference numerals and detailed explanations thereof will be omitted. Also in the second aspect, the metal shell work 51 having the mounting screw portion 57 formed therein
By attaching the to the holder 10, the metal shell work 5
1 is held so that the movement in the direction intersecting the axis O is restricted and the rotation around the axis O is possible. And
Instead of image capturing by a camera, a sensor for detecting the screw thread of the mounting screw portion 57 is arranged, and the main body indicated by the detection state of the sensor when the metal shell work 51 is rotated around the axis O in that state. Based on the rotation angle phase of the metal fitting work 51, the ground electrode attachment position is determined by the metal fitting work 51.
It is determined so as to satisfy a certain angular relationship with the screw thread start position of the mounting screw portion 57 around the axis O of.

In FIG. 8, the sensor abuts on the mounting screw portion 57, permits the rotation of the metal shell work 52, and causes a displacement in a specific direction according to a change in the rotation angle phase of the metal shell work 51. The rotation angle detection jig 36 is included. Then, the rotation angle detection jig 36
With the mounting screw portion 57 in contact with the metal shell work 5
The displacement of the rotation angle detection jig 36 when 1 is rotated,
Displacement detection sensor, linear encoder 24 in this embodiment
To detect. Then, based on the detection result, the mounting screw portion 5 is provided around the axis O of the metal shell work 51.
The ground electrode mounting position is determined so as to satisfy a certain angular relationship with the screw thread starting position of 7. In the present embodiment, the rotation angle detection jig 36 has a saw blade-shaped engagement surface 37 that engages with a plurality of adjacent screw threads of the mounting screw portion. By providing the engagement surface 37 that engages with the plurality of threads, rattling of the rotation angle detection jig 36 is reduced, and the displacement generation direction can be stabilized.

Similar to the first embodiment, the spark plug work 51 adjusts the position in the direction of the axis O to the target position and then rotates about the axis O to set the rotation angle phase indicating the fixed position of the ground electrode. Find out. As shown in
The reference jig 34 that gives the reference position is fixedly arranged in the direction of the axis O, and the metal shell work 51 is raised to raise the reference jig 3
4 by contacting the seat surface 53 of the mounting seat portion 52,
Adjusting to the reference position. Note that, as shown in FIG. 10, the lower edge tip position of the reference jig 34 is aligned with the reference diameter position SP described in the first embodiment. Even in the case of a metal shell work having a tapered seat surface 53t, the work can be always aligned at a constant height by bringing the lower edge tip position into contact with the reference diameter position SP as a target position.

When the alignment is completed, the rotation angle detecting jig 36 is brought into contact with the mounting screw portion 57 by the engaging surface 37, as shown in FIG. Then, the metal shell work 51 is rotated around the axis O. Then, as shown in, the engagement surface 37 (the contact surface with the mounting screw portion 37) is
Sliding in the thrust direction with respect to the thread surface causes displacement in a direction orthogonal to the axis O (that is, in the horizontal direction). As shown in FIG. 8, in the present embodiment, the rotation angle detection jig 36
Is supported from below by the support 30.
Thus, the horizontal displacement is guided. The target displacement of the rotation angle detection jig 36 when the ground electrode mounting position is aligned with the welding position is obtained in advance, and if the displacement detected by the linear encoder 24 reaches the target displacement. The rotation of the metal shell work 51 is stopped, and thereafter, the ground electrode is welded as in the first embodiment. The support 30 has a fixed positional relationship with the reference jig 34 in the direction of the axis O. Therefore, the rotation angle detection jig 36 (sensor) is arranged at a position apart from the seat surface 53 (reference diameter position SP) of the mounting seat portion 52 on the mounting screw portion 57 side by a predetermined length.

When the engagement surface 37 does not necessarily smoothly slide in the thrust direction with respect to the thread surface, the engagement surface 37 and the thread are engaged with each other in the direction of the axis O to detect the rotation angle. The displacement of the jig 36 may not always be accurately measured. Therefore, as shown in FIG. 12, when the rotation angle phase of the metal shell work indicated by the displacement of the rotation angle detection jig 36 reaches the target phase by rotating the metal shell work, the rotation of the metal shell work is performed. , And in that state, the rotation angle detection jig 36 is attached to the mounting screw portion 3 in the direction orthogonal to the axis.
It is separated from 7. Then, if the rotation angle phase of the metal shell work in the stopped state is specified based on the displacement of the rotation angle detection jig 36 when re-contacted as shown in, the influence of the above-mentioned bite Therefore, the displacement of the rotation angle detection jig 36 can be measured more accurately. If this displacement is not the target displacement,
From the difference between the current displacement and the target displacement, the amount of rotation of the metal shell work required to achieve the target displacement may be calculated, and rotation for adjustment may be added.

In this embodiment, the rotation angle detecting jig 36 for the purpose is moved toward and away from the mounting screw portion 37 by the air cylinder 31 (the reference numeral 33 indicates the air cylinder 31 by the control device 10). Is a cylinder controller for driving and controlling). When the metal shell work 51 is rotated to detect the displacement of the rotation angle detection jig 36, the valve 32 is opened and the air cylinder 3 is opened.
The inside of 1 is opened so that the biasing force of the air cylinder 31 does not reach the rotation angle detection jig 36. The rotation angle detection jig may be configured to generate axial displacement by the screwing action of the mounting screw portion when the metal shell work is rotated.

Various modifications of the second aspect of the present invention will be described below. 14 to 16 are examples in which a sensor that detects when the thread start end reaches a specific angular position around the axis is used. In FIG. 14, the optical sensor 4 indicates the arrival of the incomplete thread 57i forming the thread start end on one side in the radial direction of the metal shell work 51.
It is detected by 0, 41. Here, a so-called transmissive optical sensor is used, which detects light traveling from the light projecting unit 40 toward the light receiving unit 41 depending on whether or not the incomplete thread 57i blocks the light. A reflection type optical sensor may be used in which the light receiving section detects the light from the light projecting section reflected by the incomplete thread 57i. Further, FIG. 15 shows an example in which the proximity switch 42 is used to detect the incomplete thread 57i instead of the optical sensor, and FIG. 16 is similarly the limit switch 43 to detect the incomplete thread 57i. It is an example. Each of these sensors is arranged at a position apart from the seat surface 53 (reference diameter position SP) of the mounting seat portion 52 on the mounting screw portion 57 side by a predetermined length as shown in FIG.

The position of the complete screw thread may be detected by a sensor instead of the incomplete screw thread 57i. That is,
As shown in FIG. 17, if the relative position between the sensor and the metal shell work 51 in the direction of the axis O is fixed, when the metal shell work 51 is rotated, the sensor 4 apparently appears.
The detection state of the sensor changes as if the screw thread 57m and the screw valley 57v pass through the position 0 (41) alternately.
For example, it is considered that the rotation angle phase of the metal shell work 57 when the detection state of the screw thread 57m and the detection state of the screw valley 57v are switched is substantially constant. Therefore, based on the timing of this switching, the rotating main body is rotated. Metal fitting work 57
The current rotation angle phase of can be known. In this embodiment, the same optical sensor 40 (41) as in FIG. 14 is used.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing an example of an apparatus for carrying out a spark plug manufacturing method according to a first aspect of the present invention.

FIG. 2 is an explanatory diagram showing a first example of a method for manufacturing a spark plug according to a first aspect using pattern matching with a master image.

FIG. 3 is an explanatory view when the process of FIG. 2 is applied to a metal shell work having a tapered gas sealing surface.

FIG. 4 is an explanatory view showing a second example of the method for manufacturing the spark plug according to the first aspect using the pattern matching with the master image.

FIG. 5 is an explanatory view showing a first example of a method of determining a ground electrode attachment position without using pattern matching in the first aspect of the present invention.

FIG. 6 is an explanatory diagram showing a second example of the same.

FIG. 7 is an explanatory view showing a third example of the same.

FIG. 8 is a block diagram schematically showing an example of an apparatus for performing the spark plug manufacturing method according to the second aspect of the present invention.

FIG. 9 is a process explanatory view showing a first example of a method for manufacturing a spark plug according to a second aspect.

FIG. 10 is an explanatory view when the process of FIG. 9 is applied to a metal shell work having a tapered gas sealing surface.

FIG. 11 is an explanatory view of the process continued from FIG. 9;

12 is an explanatory view of the process following FIG. 11. FIG.

FIG. 13 is a cross-sectional view showing an assembling mode of a spark plug using the metal shell work after attaching the ground electrode.

FIG. 14 is a process explanatory view showing a third example of the method for manufacturing the spark plug according to the second aspect.

FIG. 15 is a process explanatory drawing which similarly shows a fourth example.

FIG. 16 is a process explanatory diagram which similarly shows a fifth example.

FIG. 17 is an explanatory process drawing similarly showing the sixth example.

[Explanation of symbols]

26 Welding equipment 36 Rotation angle detection jig 37 Engaging surface 40,41 Optical sensor 42 Proximity switch 43 Limit switch 51 Metalwork work SP reference diameter position 54 Ground electrode 57 Mounting thread 57t screw thread start position 57f Top complete screw thread 57i incomplete thread VA image field of view O axis

Claims (13)

[Claims] 1. A cylindrical metal shell having a mounting seat portion in the circumferential direction projectingly formed at an axially intermediate position on the outer peripheral surface, and a mounting screw portion being formed following the mounting seat portion. The main body at the ground electrode mounting position satisfying a certain angular relationship with respect to the reference angular position defined in the circumferential direction of the mounting screw part in a state where the mounting screw part is tightened to the limit position specified by the seat part. A spark plug manufacturing method for mounting a ground electrode on an end face of a metal fitting, comprising: a mounting screw portion forming step of forming a mounting screw portion on an outer peripheral surface of a metal shell work before mounting the ground electrode; and the mounting seat portion and the mounting screw. An image of the metal shell work (hereinafter referred to as a work image) is photographed by the camera so that at least a part of the part appears in the image field of view,
Based on the work image, a screw thread phase grasping step of grasping an angle phase of the mounting screw portion with respect to the camera, and based on the grasping result, the ground electrode is made to satisfy the angular relationship on the metal shell work. A method of manufacturing a spark plug, comprising the step of attaching a ground electrode. 2. A master image obtained by photographing a standard metal shell product in which the mounting screw portion is formed at a camera angle where a ground electrode mounting position is known is prepared, and in the screw thread phase grasping step, the camera and the While photographing the work image while relatively rotating the metal shell work, performing pattern matching processing with the master image, finding the angle phase between the camera and the metal shell work that match the image in the pattern matching processing, The method of manufacturing a spark plug according to claim 1, wherein the ground electrode attachment position is determined based on the angular phase. 3. The work image and the master image are obtained by photographing the outer peripheral surface of the metal shell work or the standard metal shell product, on which the mounting screw portion is formed, from the front direction, On the seat surface of the mounting seat portion of the metal shell work, a reference diameter position is set at a position that is separated from the axis of the metal shell work by a certain length in the radial direction, and the master image is the standard metal shell product. The reference diameter position is photographed in a form matched with a target position on the image view, and the reference diameter is obtained by translating the metal shell work on the work image in the image view. The method of manufacturing a spark plug according to claim 2, wherein after the position is adjusted to the target position, the pattern matching process is performed while rotating the metal shell work around an axis. 4. The master image is, on one side in the radial direction of the mounting screw portion, the one that is closest to the mounting seat portion among the contour lines of a plurality of complete threads arranged in the axial direction,
The method of manufacturing a spark plug according to claim 3, wherein the mounting seat portion is photographed so as to appear in an image visual field. 5. The method of manufacturing a spark plug according to claim 3, wherein the master image is captured so that a screw thread starting position near the mounting seat portion appears in an image visual field. 6. The work image is obtained by photographing the outer peripheral surface of the metal shell work on which the mounting screw portion is formed from the front direction. In the work image, the seat surface of the mounting seat portion is obtained. The reference position is specified above, and on the radial direction one side of the mounting screw portion, among the outlines of a plurality of complete threads arranged in the axial direction, those located in a specific order when viewed from the screw thread starting position, The method of manufacturing a spark plug according to claim 1, wherein the angular phase of the mounting screw portion is grasped based on a distance from a reference position. 7. The work image is formed of the mounting screw portion of the metal shell work such that an incomplete screw portion formed on the screw thread starting position side near the mounting seat portion appears in the image field of view. The spark plug according to claim 1, wherein the spark plug is obtained by photographing the outer peripheral surface from the front direction, and the angular phase of the mounting screw portion is grasped based on image information of the incomplete screw portion appearing in the work image. Manufacturing method. 8. A cylindrical metal shell having a circumferential mounting seat projectingly formed at an axially intermediate position on the outer peripheral surface, and a mounting screw portion formed so as to follow the mounting seat, and wherein the mounting The main body at the ground electrode mounting position satisfying a certain angular relationship with respect to the reference angular position defined in the circumferential direction of the mounting screw part in a state where the mounting screw part is tightened to the limit position specified by the seat part. A method for manufacturing a spark plug for attaching a ground electrode to an end face of a metal fitting, comprising: a mounting screw portion forming step of forming a mounting screw portion on an outer peripheral surface of a metal shell work before mounting the ground electrode; While holding the metal shell work so that the movement in the direction intersecting with the axis is restrained and capable of rotating around the axis, a position separated from the seat surface of the mounting seat by the predetermined length on the mounting screw side. At the axis circumference At a specific angle position of, a sensor for detecting the thread of the mounting screw portion is arranged in advance, and when the metal shell work is rotated around the axis in that state, based on the detection state of the sensor, A thread phase grasping step of grasping an angular phase of the mounting screw portion with respect to the sensor, and a ground electrode attaching step of attaching the ground electrode to the metal shell work so as to satisfy the angular relationship based on the grasping result; A method for manufacturing a spark plug, comprising: 9. The rotation of the sensor, which is in contact with the mounting screw portion, permits rotation of the metal shell work, and causes displacement in a specific direction in response to a change in a rotation angle phase of the metal shell work. The angle detection jig is provided, and the displacement of the rotation angle detection jig when the metal shell work is rotated while the rotation angle detection jig is in contact with the mounting screw portion is detected. The method for manufacturing a spark plug according to claim 8, wherein the angle phase of the mounting screw portion is grasped based on the above. 10. The manufacturing method of a spark plug according to claim 9, wherein the rotation angle detection jig has saw blade-shaped engagement surfaces that engage with a plurality of thread ridges adjacent to each other of the mounting screw portion. Method. 11. The rotation angle detection jig is such that, when the metal shell work is rotated, a contact surface with the mounting screw portion slides in a thrust direction with respect to a thread ridge surface, whereby the axis line is rotated. The method for manufacturing a spark plug according to claim 9, wherein the spark plug is displaced in a direction orthogonal to the spark plug. 12. When the rotation angle phase of the metal shell work indicated by the displacement of the rotation angle detection jig reaches a target phase by rotating the metal shell work, the rotation of the metal shell work is stopped. , In that state, based on the displacement of the rotation angle detection jig when the rotation angle detection jig is once separated from the mounting screw part and then abutted again in the direction orthogonal to the axis line. The method of manufacturing a spark plug according to claim 11, wherein the rotation angle phase of the metal shell work in the stopped state is specified. 13. The metal shell work is rotated about an axis, and the rotation of the metal shell work is stopped when the mounting screw portion reaches a specific rotation angle phase. A welding device for the ground electrode is arranged at a position of the metal shell work corresponding to the ground electrode attachment position, and the ground electrode is welded on the spot to the metal shell work that has stopped rotating by the welding device. Any one of claims 1 to 12 to perform
A method of manufacturing a spark plug according to item.