JP2000323259A - Manufacture of spark plug and spark plug manufacturing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently conduct the eccentric adjustment and gap distance adjustment of an electric for forming a spark gap as a sequence of processes. SOLUTION: In this equipment 1, a spark plug to be worked W is conveyed, gap distance adjustment and eccentric adjustment are successively conducted, and change in the bending work direction to a ground electrode in these adjustments is performed on the basis of rotation on the center axial line of the center electrode of the spark plug to be worked W with a rotating work holder 304. The eccentric adjustment and gap distance adjustment of an electrode for forming a spark gap are efficiently conducted as a sequence of processes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a spark plug manufacturing method and a spark plug manufacturing apparatus.

[0002]

2. Description of the Related Art In a spark plug used in an internal combustion engine, in order to ensure sufficient ignition performance and spark erosion resistance of an electrode, it is necessary to adjust a gap interval between a ground electrode and a center electrode. is important. Further, if the center axis of the ground electrode and the center axis of the center electrode are eccentric, troubles such as a shortened life due to uneven consumption of the electrode and a misfire occur. For example, among spark plugs generally used, a so-called multi-pole plug has a structure in which a plurality of ground electrodes are arranged around a center electrode. In such a multipolar plug, the arc-shaped tip surface of each ground electrode faces the outer peripheral surface of the center electrode having a circular cross section, and a spark gap is formed therebetween. For example, JP-A-8-15356
No. 6 discloses the following device configuration for adjusting the gap interval or the amount of eccentricity of such a multipolar plug. That is, an image of the spark gap is taken from the tip side of the center electrode by a CCD camera or the like, and the spark gap interval and the amount of eccentricity are measured from the image. And when the spark gap interval is larger than the target value,
Adjustment bending is performed on the ground electrode using a hammering device so that this reaches the target value. Further, when the electrode is eccentric, hammering is applied to the ground electrode in the lateral direction and the ground electrode is bent to eliminate the eccentric state.

[0003]

In the apparatus disclosed in the above publication, hammering for adjusting the gap interval and hammering for adjusting the eccentricity are individually performed by dedicated hammering devices. Therefore, necessary ones are appropriately selected according to the state of formation of the spark gap. However, in actual production of spark plugs, it is often impossible to obtain a desired spark gap formation state unless both eccentricity adjustment and gap interval adjustment are performed. It can be said that there is no structural device for efficiently performing the eccentricity adjustment and the gap interval adjustment as a series of steps.

On the other hand, since the eccentricity adjustment and the gap interval adjustment have a great influence on each other, when both adjustments are performed for one spark gap, the order of execution and the other adjustment by performing one adjustment are performed. It is necessary to consider the influence on the adjustment and the like, but this publication does not mention this point at all.

A first object of the present invention is to provide a method and an apparatus for manufacturing a spark plug in which the eccentricity adjustment and the gap interval adjustment of an electrode forming a spark gap can be efficiently performed as a series of steps. . Further, the second problem is that, when the eccentricity adjustment and the gap interval adjustment are performed as a series of steps, the mutual influence of the two adjustments can be reduced, and the gap interval adjustment can be executed with high accuracy while effectively eliminating the eccentricity. An object of the present invention is to provide a spark plug manufacturing method and apparatus.

[0006]

Means for Solving the Problems and Actions / Effects In order to solve the above first problem, a first method of manufacturing a spark plug according to the present invention is as follows: a base end is connected to a metal shell; The tip of the ground electrode bent to the side can rotate the spark plug to be processed around the center axis of the center electrode, where the spark plug to be processed, in which a spark gap is formed opposite the tip of the center electrode, is formed. The following steps are performed for the spark plug to be processed while being transported along a predetermined transport path at
That is, the spark gap and its peripheral part are photographed by a camera, and from the photographed image, an eccentricity measuring step of measuring the eccentricity of the center electrode tip in the width direction with respect to the center electrode tip, and the eccentricity is measured with respect to the ground electrode. An eccentricity adjustment processing step of performing a bending process in a direction to reduce by using an eccentricity adjustment processing tool,
A spark gap and a peripheral portion thereof are photographed by a camera, and a spark gap measuring step of measuring a spark gap interval from the photographed image, and a spark gap interval with respect to a ground electrode based on a value of the measured spark gap interval. The gap adjustment process is performed by using a gap adjustment tool to perform the bending process that adjusts to the reducing direction, and the direction of the bending force during the eccentricity adjustment process and the direction of the bending process during the gap interval adjustment process And the positional relationship between the eccentricity adjusting tool and the ground electrode in the eccentricity adjusting processing step, and the gap interval adjusting processing step, based on the rotation of the center electrode of the spark plug to be processed around the central axis of the spark plug. Wherein the positional relationship between the gap adjusting tool and the ground electrode is individually adjusted.

[0007] A first aspect of the spark plug manufacturing apparatus of the present invention is that the distal end of the ground electrode whose base end is connected to the metal shell and whose distal end is bent sideways faces the distal end of the center electrode. And a rotation holding unit for removably holding the spark plug to be processed, in which a spark gap is formed between them, and rotating the spark plug around the center axis of the center electrode in this state, and holding the spark plug to be processed. Transport means for transporting the rotated holding section along a predetermined transport path, and further, along the transport path, shoots a spark gap and a peripheral portion thereof with a camera. Eccentricity measuring means for measuring the amount of eccentricity in the width direction of the tip of the ground electrode with respect to the portion, and eccentricity adjusting means for performing bending in the direction in which the amount of eccentricity is reduced to the ground electrode using an eccentricity adjusting tool. A spark gap and a peripheral portion thereof are photographed by a camera, and from the photographed image, a spark gap measuring means for measuring a spark gap interval, and a spark gap interval with respect to a ground electrode based on a value of the measured spark gap interval. A gap interval adjusting means for performing a bending process for adjusting in a reducing direction using a gap adjusting tool is arranged, and a direction of a bending force at an eccentricity adjusting process and a direction of a bending process at a gap interval adjusting process. And the positional relationship between the eccentricity adjusting tool and the ground electrode in the eccentricity adjusting processing step, and the gap interval adjusting processing step, based on the rotation of the center electrode of the spark plug to be processed around the central axis of the spark plug. Wherein the positional relationship between the gap adjusting tool and the ground electrode is individually adjusted.

According to the above-described method or apparatus, while adjusting the gap interval and the eccentricity while carrying the spark plug to be processed, the bending direction of the ground electrode is changed during the adjustment. Is performed based on the rotation of the center electrode of the spark plug to be processed around the central axis of the spark plug to be processed, so that the eccentricity adjustment and the gap interval adjustment of the electrode forming the spark gap can be efficiently performed as a series of steps.

In order to solve the above-mentioned second problem, a second aspect of the spark plug manufacturing method (apparatus) of the present invention is that the base end is connected to the metal shell and the tip is bent back to the side. Each of the following steps (means) is defined as a spark plug to be processed, in which the arc-shaped tip surface of the grounded electrode faces the tip side surface of the cylindrical center electrode and a spark gap is formed therebetween. That is, an eccentricity measuring step (eccentricity measuring means) for photographing the spark gap from the center electrode tip side with a camera and measuring the amount of eccentricity of the center electrode tip portion in the width direction with respect to the center electrode tip portion from the captured image. The eccentricity adjustment processing step (eccentricity adjustment processing means) in which the eccentricity is reduced by using the eccentricity adjustment processing tool, and the spark gap with respect to the spark plug to be processed after the eccentricity is reduced. So A spark gap measuring step (spark gap measuring means) of photographing a peripheral portion by a camera and measuring a minimum distance between an outer peripheral edge line of the center electrode and a leading edge line of the ground electrode as a spark gap interval based on the photographed image; A gap adjusting processing step (a gap adjusting processing) in which a bending process for adjusting the spark gap interval with respect to the ground electrode is performed using a gap adjusting tool based on the measured spark gap interval value. Means).

The arrangement of the ground electrode and the center electrode of the spark plug to be processed as described above is, for example, one generally employed in a multipolar spark plug. The spark gap interval is often managed as the minimum value of the distance between edges facing each other across the gap between the ground electrode and the center electrode. In this case, the opposing edge of each electrode is determined from the captured image of the spark gap and its peripheral portion, and the interelectrode opposing distance measured in the axial cross-section radial direction of the center electrode is set as the gap interval, and the gap interval is managed by the minimum value. Has been done. For example, when the minimum value of the gap interval is less than the set target value, a bending process for adjusting the gap interval is performed so as to reach the target value.

However, if eccentricity occurs between the ground electrode and the center electrode, the position on the edge line giving the minimum gap interval may differ depending on the degree of the eccentricity. For example, FIG. 27A shows a case where no eccentricity occurs between the ground electrode W2 and the center electrode W1, and the outer peripheral surface edge E of the center electrode W1 and the edge E2 of the arc-shaped tip surface of the ground electrode W2. Has a substantially concentric positional relationship. Further, the minimum value g of the gap interval measured in the radial direction of the center O of the center electrode W1 is generated at the position of the point u on the edge line E2. However, when the eccentricity occurs as shown in FIG. 3B, the concentric positional relationship between the outer peripheral edge E of the center electrode W1 and the edge E2 of the arc-shaped distal end surface of the ground electrode W2 breaks, resulting in a minimum gap interval. (Hereinafter, referred to as a minimum gap interval position) is moved on the edge line E2 in a direction opposite to the above-described eccentric direction to obtain a point u ′.
In addition, the minimum value g ′ of the gap interval is completely different from the value g in (a).

On the premise of this, for example, considering the case where the gap interval adjustment for the spark gap is performed first, and then the eccentricity adjustment is performed, the gap interval is set within the desired value range by the preceding gap interval adjustment. Even if it can be accommodated, if eccentricity adjustment is performed after that, both the value and position of the minimum gap interval will change, causing a gap interval defect or causing problems such as an increase in man-hours due to readjustment Become. However, according to the second aspect of the spark plug manufacturing method (apparatus) of the present invention described above, after the eccentricity adjustment with respect to the spark gap is first performed, thereby eliminating the eccentric state affecting the value and position of the minimum gap interval, Since the gap interval adjustment is performed, defective gap interval is extremely unlikely to occur, and readjustment and the like are not required. That is, when the eccentricity adjustment and the gap interval adjustment are performed as a series of steps, the influence of mutual interference between the two adjustments can be reduced, and the gap interval adjustment can be performed with high accuracy while effectively eliminating eccentricity. .

In the method and apparatus according to the present invention, the eccentricity adjusting tool can be shared with the gap adjusting tool. Thereby, the eccentricity adjusting processing means and the gap interval adjusting processing means can be shared, and the apparatus can be simplified. In this case, the camera (photographing means) used for the eccentricity measuring means and the spark gap measuring means can be shared, whereby the device configuration can be further simplified and made compact.

[0014]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 is a plan view conceptually showing one embodiment of a spark plug manufacturing apparatus (hereinafter, simply referred to as a manufacturing apparatus) of the present invention. The manufacturing apparatus 1
Is a spark plug to be processed (hereinafter, also referred to as a workpiece) W
And a traverser 300 as a transporting means for intermittently transporting along a transport route C (which is linear in the present embodiment). A process execution unit such as a part value measurement device (reference position measurement device) 13, a bending device 14, an eccentricity measurement device, and a photographing / analysis unit 15 as a spark gap measurement device is arranged.

The traverser 300 has a moving table 302 that moves on rails 303 laid along the transport path C, and a rotating work holder 304 (rotation holding unit) attached to the moving table 302. The table mechanism 11 is mainly configured. The moving table 302 is attached to an intermediate position of a timing belt (which may be a chain) 301 wound around timing pulleys (which may be sprockets) 306, 306, and drives the timing belt 301 by a drive motor 24 which can rotate in both forward and reverse directions. The reciprocating drive reciprocates along the transport path C, and the inspection and bending processes are sequentially performed while stopping at each process execution unit.

As shown in FIG. 6, the workpiece W is composed of a cylindrical metal shell W3, an insulator W4 fitted inside the metal shell W3, a center electrode W1 inserted in the axial direction of the insulator W4,
One end is connected to the metal shell W3 by welding or the like, and the other end is bent back to the center electrode W1 side, and a tip end surface thereof is provided with a ground electrode W2 and the like facing the side surface of the center electrode W1. A plurality (four in this embodiment) of ground electrodes W2 are arranged around the central axis of the center electrode W1, and the whole is configured as a multipolar spark plug.

FIG. 2 is a sectional view showing the structure of the moving table mechanism 11. On the upper surface side of the rotary work holder 304, a work mounting hole 311 formed in the vertical direction at the center position is opened, and the work W whose rear end is fitted into the cylindrical sub-holder 23 is inserted therein. The sub-holder 23 is detachably mounted together with the sub-holder 23 with the ground electrode W2 side up. On the other hand, a rotating shaft 310 extends downward from the center of the lower surface of the rotating work holder 304 on the extension of the center axis of the work mounting hole 311 (that is, the center axis of the work W). The bearing 31 is inserted through the hole.
It is rotatably supported via 3,314. The rotating shaft 310 can be held at any position by the motor 315,
It is driven to rotate in both forward and reverse directions.

Next, as shown in FIG. 3, a plurality of (three in this embodiment) work chucks 316 surround the mounted work W on the upper surface of the rotary work holder 304.
Is attached. As shown in FIG. 2, each work chuck 316 is provided with a work mounting hole 3 with respect to a guide 316 c provided on the upper surface of the rotary work holder 304.
The slide member 316a is attached to the work W so as to be able to advance and retreat in the radial direction around the center 11, and a chuck plate 316b fixed to the upper surface of the slide member 316a using bolts 316d. As shown in FIG. 3, the chuck plate 316b is formed with a slope on both sides so that the width becomes narrower toward the front end, and the front end position has a shape corresponding to the surface to be held on the work W side. A work holding surface 316e (in this case, an arc shape corresponding to the outer peripheral surface of the screw portion of the metal shell W1) is formed.

As shown in FIG. 2, the rotary work holder 30
4, each slide member 316 a is provided with a guide 316.
And a chuck cylinder 317 that moves forward and backward along the axis. Each slide member 316 is attached to the chuck cylinder 3
17, when the workpiece W is advanced toward the mounted workpiece W, as shown in FIG.
The three chuck plates 31
6b is held in a sandwiched state. FIG. 3B shows a state in which the rotating work holder 304 is rotated counterclockwise by 90 ° while holding the work W.

FIG. 4 is a plan view showing the structure of the ground electrode alignment mechanism 12. As shown in FIG. The ground electrode alignment mechanism 12 is provided at a position where the work W is mounted on the moving table mechanism 11, and is used to manually (or may use a mounting robot) of the work W mounted on the rotary work holder 304. This is for aligning and positioning the ground electrode W2 corresponding to the spark gap to be inspected in a direction that is convenient for performing the subsequent inspection and bending processes. In this case, as shown in FIG. 1, the positions where the respective steps except for the reference portion position measurement are performed are arranged along one side of the transfer path C of the work W.
The work W is aligned so that the direction in which the tip surface of the ground electrode W2 faces the side surface of the center electrode W1 (see also FIG. 6) is substantially orthogonal to the transport path C, and the ground electrode W2 faces the arrangement side of the process execution position. It is made to let.

More specifically, the ground electrode aligning mechanism 12 includes a main body 318 movable substantially in parallel with the transport path C along a guide 319.
20 and 320 are at the height positions corresponding to the ground electrode W2 of the work W mounted on the rotary work holder 304,
Each is mounted so as to be pivotable in a substantially horizontal plane. These two alignment arms 320, 320
Pins 321, 32 on both sides in the width direction of
1 and a gripping head 320a, 320a is formed at the tip. On the other hand, the rear ends of the arms 320, 320 are driven forward and backward by a link mechanism and an air cylinder (not shown). Thus, the alignment arms 320, 320 are pivotally driven so that the gripping heads 320a, 320a approach and separate from each other, and sandwich the ground electrode W2 to be aligned between the gripping heads 320a, 320a at a predetermined alignment position. They are arranged and positioned.

FIG. 5 shows an example of the configuration of the reference portion position measuring device 13. The measuring device 13 includes a light projecting unit 201 and a light receiving unit 20 disposed on both sides thereof with the transport path C interposed therebetween.
2 is provided. The light projecting unit 201 traverses the band-shaped laser beam L1 (see also FIG. 6) in a direction whose width is substantially parallel to the central axis of the center electrode W1 at the tip end intermediate position of the ground electrode W2 to be measured. The light receiving unit 2
Reference numeral 02 denotes a line sensor (for example, a one-dimensional CCD sensor) that receives the belt-like laser light L1. The portion of the laser beam L1 that is blocked by the ground electrode W2 does not reach the light receiving unit 202 and becomes a shadow. By reading the tip position of this shadow from the output of the line sensor, the tip position (reference portion position) of the ground electrode W2 is known. be able to.

FIGS. 7A and 7B show an example of the configuration of the photographing / analysis unit 15, which is a main part of the eccentricity measuring means and the spark gap measuring means (FIG. 7A is a front view of the main part, and FIG. 7B is a side view). Yes: the electrical configuration of the image analysis unit will be described later).
The imaging / analysis unit 15 has a base 36 fixed on the frame 22 and a column 37 erected substantially perpendicular to the base 36. A camera driving section 39 is attached to the column 37 via slide clamps 41, 41 so as to be slidable up and down. The camera drive unit 39 includes a lifting head 42 in a case 43, a screw shaft 44 screwed to the lifting head 42 and moving the lifting head 42, and a screw shaft 44 via timing pulleys 48 and 49 and a timing belt 47. And a camera elevating motor 46 for driving the camera in both forward and reverse directions.
A camera 40 for photographing the work W positioned at the photographing position and a ring light 38 as an illumination unit for illuminating the tip of the work W are attached to the elevating head 42. The camera 40 and the light 38 are integrated. The imaging device main body 45 is formed.

The camera driving section 39 rotates the screw shaft 44 by the operation of the motor 46, and moves the photographing apparatus main body 45 and thus the camera 40 in the photographing direction of the work W (that is, in the vertical direction). (In this case, the front end surface of the ground electrode W2).

The camera 40 is configured as, for example, a CCD camera having a two-dimensional CCD sensor as an image detection unit, and photographs the work W from the front end side in the center axis direction of the center electrode W1, that is, from above. In this embodiment, FIG.
As shown in FIG. 5, the camera 40 is configured to enlarge the spark gap g of the workpiece W at a predetermined magnification and to form the entire tip edge E2 of the ground electrode W2 facing the spark gap g and the outer peripheral edge of the tip face of the center electrode W1. Of these, a portion E1 facing the spark gap (defined as a portion corresponding to an angle range φ in which both edges of the ground electrode W2 are viewed from the center axis O of the center electrode W1)
Is taken so that only a part including the entirety of the image falls within the visual field 210. Here, the magnification is set so that at least half the circumference of the outer peripheral edge E of the front end surface of the center electrode W1 falls within the visual field 210. On the other hand, in order to further increase the magnification, as shown in FIG. 3B, a portion of the outer peripheral edge E that is less than half the circumference (however, the entire portion facing the spark gap E1 enters) is within the visual field 210. It may be in the form. On the other hand, if the magnification can be sufficiently secured, the outer edge E
May fit within the field of view.

Next, FIG. 8 shows an example of the configuration of the bending device 14. The bending device 14 has a main body case 51 attached to a front end surface of, for example, a cantilever type frame 50a attached to a base 50 of the device. A movable base 53 is housed in the body case 51 so as to be able to move up and down, and a pressing punch 54 is attached to the movable base 53 so as to protrude from a lower end surface of the body case 51. By rotating a screw shaft (for example, a ball screw) 55 screwed to the movable base 53 in both forward and reverse directions by a pressing punch driving motor 56, the pressing punch 54 moves the bent portion of the ground electrode W 2 of the work W with respect to the bent portion. Thus, it can approach / separate from diagonally above and can hold an arbitrary height position corresponding to the stop position of the screw shaft drive. The rotation transmitting force of the pressing punch drive motor 56 is transmitted to the screw shaft 55 via the timing pulley 56a, the timing belt 57, and the timing pulley 55a.

As shown in FIG. 8, a bending metal fitting 58 which is in contact with the ground electrode W2 is attached to the tip of the pressing punch 54, and a pressure detecting portion between the movable base 53 and the pressing punch 54 is provided. A load cell 155 is provided. The direction in which the pressing punch 54 (FIG. 8) approaches and separates from the ground electrode W2, that is, the adjusting pressing stroke direction OP is determined by setting a plane perpendicular to the center axis of the center electrode W1 to a reference plane (parallel to a projection plane described later: An angle B with H (which is set substantially horizontal) is set to about 45 °.

FIG. 9 is a block diagram showing an electrical configuration of the main control section 100 of the spark plug manufacturing apparatus 1 and its periphery. The main control unit 100 includes an I / O port 101 and a CPU 102, a ROM 103, and a RAM 10 connected thereto.
The main control program 103a is stored in the ROM 103. The drive unit 2c of the traverser 300 (FIG. 1) is connected to the I / O port 101. The drive section 2c includes a servo drive unit 2a, a drive motor 24 connected to the servo drive unit 2a, a pulse generator 2b for detecting a rotational angle position of the motor 24, and the like. Further, to the I / O port 101, a moving table mechanism 11, a ground electrode alignment mechanism 12, a reference position measuring device 13, a bending device 14, and a photographing / analysis unit 15 are connected.

FIG. 10 shows the electrical configuration of the photographing / analyzing unit 15. The control unit (hereinafter, also referred to as an image analysis unit) 110 includes an I / O port 111 and a CPU 112, a ROM 113, and a RAM 114 connected thereto.
It consists of a microprocessor consisting of
The ROM 113 stores an image analysis program 113a. The I / O port 111 has a camera 40 (two-dimensional CCD sensor 115) as a photographing unit.
And a sensor controller 116 for converting the sensor output into a two-dimensional digital image input signal).
For example, it is connected to a storage device 115 for storing master image data and the like used for edge line determination and the like. Also,
The RAM 114 has a work area 114 of the CPU 112.
a, photographed image data of the work W by the photographing camera 40,
Further, memories 114b and 114c for storing master image data used for inspection of the work W are formed. The CPU 112 is a main component such as an eccentricity measuring unit, a spark gap interval measuring unit, and an adjustment pressing stroke determining unit, based on the image analysis program 113a.

FIG. 11 is a block diagram showing an example of the electrical configuration of the control unit of the rotary work holder 304 forming the rotation holding unit. The control unit 120 includes an I / O port 121 and a CPU 122, a ROM 123, and a RAM 1 connected thereto.
A microprocessor comprising 24 or the like is configured as a main part. The control program for the rotary work holder 304 is stored in the ROM 123. The I / O port 121 has a rotation drive unit 3 of the rotation work holder 304.
04c is connected. The drive section 304c includes a servo drive unit 304a, a drive motor 315 connected to the servo drive unit 304a, a pulse generator 304b for detecting a rotational angle position of the motor 24, and the like.
The I / O port 101 is connected to a cylinder drive circuit 317a for the three chuck cylinders 317 described above.

FIG. 12 is a block diagram showing an example of the electrical configuration of the bending device 14. As shown in FIG. The control unit 150 includes an I / O port 151, a CPU 152 connected thereto,
The main part is a microprocessor comprising a RAM 53 and a RAM 154. Pressing punch drive motor 56
Is the I / O port 1 via the servo drive unit 156
51 and a pulse generator (PG) 1
59 are connected. Then, the CPU 152 determines that the RO
The RAM 15 is controlled by the control program stored in the M153.
With the work area 4 as a work area, the motor 56 is driven so as to obtain the adjustment pressing stroke instructed by the main control unit 100, and controls the bending of the ground electrode W2. Note that the RAM 104 functions as a work area 104a of the CPU 102. In addition, the above-described load cell 1
55 is connected to the I / O port 151 via the load amplifier 157 and the A / D converter 158.

Hereinafter, the flow of processing of the spark plug manufacturing method of the present invention using the manufacturing apparatus 1 will be described with reference to the flowchart of FIG. First, the moving table 302 shown in FIG. 1 is moved to the work mounting position, and the work W is mounted on the rotary work holder as shown in FIG. In S1, the ground electrode alignment mechanism 12 receives a command from the main control unit 100, activates the alignment arm 320 as shown in FIG. 4, and performs alignment and positioning by sandwiching one of the ground electrodes W2. The aligned and positioned ground electrode W2 is selected as a processing target. In S2, the work table W is chucked by operating the three work chucks 316 by the chuck cylinders in the moving table mechanism 11 while maintaining the state in which the ground electrode W2 is sandwiched by the alignment arm 320. With this chuck, the work W is brought into a state where the ground electrode W2 is aligned. When the chuck is completed, the ground electrode alignment mechanism 12 retracts the alignment arm 320.

Subsequently, in S3, the work W is carried by the traverser 300 to the position of the reference position measuring device 13. As shown in FIG. 5, the reference position measuring device 13 measures the position of the tip of the target ground electrode W2 using the laser beam L1. Next, in S4, the camera driving unit 39 of FIG.
Moves the camera 40 up and down with reference to the measured tip position of the ground electrode W2, and positions the camera 40 at a position where it is focused on the ground electrode W2. In S5, gap shooting / analysis processing is performed. Here, the workpiece W is moved / positioned to the photographing position with respect to the photographing / analysis unit 15 in which the camera 40 has been positioned, and the image analyzing unit 110 (FIG. 10)
Then, as shown in FIG. 13, by analyzing the image, the outer peripheral edge E of the center electrode W1 and the leading edge E2 of the ground electrode W2 are determined. Note that the method of determining the edge line is a technique well known in the field of image processing, and a detailed description thereof will be omitted.

Next, in S6, the amount of eccentricity is calculated based on the analysis result. As the amount of eccentricity, for example, an eccentric amount defined in one of the forms shown in FIGS. First, in FIG. 14, while defining a reference line K passing through the center (axis) O of the center electrode W1 in the above-mentioned photographed image, a radial line is drawn from the center O to see both ends of the leading edge E2 of the ground electrode W2, On both sides of the reference line K, the angles ε1, ε2 formed between the two diameter lines are determined. ε1 = ε2
If so, the eccentricity is zero, and if ε1 ≠ ε2, there is eccentricity. Therefore, the amount of eccentricity can be represented by a set of two angle values ε1 and ε2. As an example, a correction angular displacement Δεa = (ε1−ε2) / 2 of the tip of the ground electrode W2 necessary for setting ε1 ≠ ε2 to ε1 = ε2 (FIG. 15)
Etc.) can be exemplified. Note that the sign (positive or negative) of Δεa is determined by the magnitude relationship between ε1 and ε2, and this sign indicates the direction of rotation about the center O related to angular displacement. Δ
Positive εa indicates clockwise rotation, and negative εa indicates counterclockwise rotation.

FIG. 17 shows an example of an algorithm for calculating the correction angular displacement Δεa. In step S61, the coordinates A1 (x1, y1) and A2 (x1) of the both end points of the leading edge line E2 described above.
2, y2) and the coordinates (x0, y0) of the center O are read. These are all calculated / calculated when the edge lines E and E2 are determined. Then, in S62, a reference line K passing through the center O is generated. FIG. 14 (b)
As shown in FIG. 5, the orientation of the reference line K is determined by the gripping heads 320a and 320a of the ground electrode alignment mechanism 12 (FIG. 4) that the ground electrode W2 is always aligned and positioned in a fixed direction as described above. Utilizing, for example, the ground electrode W
2 (or edges on both sides in the width direction of the front end portion of the ground electrode W2). In S63 of FIG. 17, the angle between K and OA1 is calculated as ε1, and the angle between OA2 and OA2 is calculated as ε2. In S64, Δεa is calculated as (ε1−ε2) / 2.

On the other hand, in FIG. 15, while the reference line K on the center electrode side is similarly defined, the center line OF passes through the center position OF when the leading edge E2 of the ground electrode W2 is assumed to be a part of an arc. A straight line parallel to the reference line K or the center axis ζ of the ground electrode W2 (FIG. 14) is connected to the ground electrode side reference line ζ ′.
And the amount of eccentricity is represented by the distance δ of ζ ′ from K. Note that the sign of the amount of eccentricity δ is determined depending on which side of Ｋ ′ is located on K. In this embodiment, the sign of δ is positive when ζ is above K, and negative when ζ is below K.

FIG. 18 shows an example of an algorithm for calculating the amount of eccentricity δ. In S161, the coordinates of the center OF of the leading edge line E2 are determined. As shown in FIG. 21, the tip end surface of the ground electrode W2 often deviates from a complete arc line due to minute unevenness because it may be formed by punching. The edge line E2 is determined by approximation to determine the center OF. In order to determine the edge line E2 with higher accuracy,
A plurality of sets of three different points on the edge line are determined, and
Determine the center positions and radii of multiple circles passing through the points,
It is desirable to define the final edge line E2 as a circle having the center and the radius as the average center position and the average radius of the plurality of circles, respectively. And FIG.
In S162, the center electrode-side reference line K is determined.
In 63, the direction orthogonal to K is defined as the y direction,
The eccentricity δ is calculated from the coordinates.

Returning to FIG. 16, if the amount of eccentricity is calculated, S
Proceed to 7 to perform eccentricity adjustment processing. As one method of the eccentricity adjusting process, the eccentricity adjusting tool and the spark plug to be processed are relatively rotatably arranged around the center axis of the center electrode, and the bending force in the direction in which the amount of eccentricity is reduced is grounded. Before and / or during the bending process, a predetermined reference angle position between the processing tool and the spark plug to be processed is determined according to the measured eccentricity. A method of performing a rotation operation of relatively rotating the processing tool and the spark plug to be processed by an angle can be exemplified. According to this method, the measured eccentricity is
By reflecting it on the relative rotation angle between the processing tool and the spark plug to be processed in the rotation operation, the eccentricity can be adjusted accurately and easily.

For example, in the method shown in FIG. 22, the eccentricity adjusting tool (58) is connected to the ground electrode (W) as shown in FIG.
On the other hand, in contrast to 2), the spark gap (g) is arranged so as to be able to approach and separate from the side opposite to the side where the spark gap (g) is formed. Determine. Then, as shown in (b), the spark plug W to be processed is moved to the grounding electrode (W) with respect to the eccentricity adjusting tool (58).
2) In a direction opposite to the eccentric direction with respect to the center electrode (W1), a predetermined angle (Δεa) is set in advance from the reference angle position (K).
The eccentricity adjusting tool (58) is brought closer to the ground electrode (W2) and pressed against the ground electrode (W2) in this state to reduce the amount of eccentricity. Specifically, the bending device 14 shown in FIG. 8 is used as a processing means, and the bending bracket 58 functions as an eccentricity adjustment processing. In this case, the relative rotation is performed by rotating the spark plug W to be processed around the central axis O by the rotation of the rotary work holder 304, and the rotation angle is adjusted by the control unit 120 shown in FIG. In accordance with the instruction, the servo drive unit 11a performs the operation by referring to the pulse signal generated by the PG 11b.

The advantage of this method is that the eccentricity can be adjusted simply and accurately by adjusting the bending direction by pressing the ground electrode W1. Here, the relative rotation angle employs Δεa described above, and the rotation direction is ΔΔa.
It is determined according to the sign of εa. As shown in FIG. 22B, this rotation causes the reference line K to move to the center electrode W1.
Is rotated by Δεa around the central axis O of the above, and moves to K ′.
Then, as shown in (c), the ground electrode W2 is relatively slid along the pressing surface of the bending fitting 58 by the pressing of the bending fitting 58, while rotating in the direction in which Δεa is reduced,
Torsional deformation (also referred to herein as bending deformation of the ground electrode in a broad sense). At this time, K ′ is the bending metal 58
If the rotation is made to coincide with the pressing direction, the eccentric state is eliminated. If the pressing operation is performed subsequently, the torsional deformation of the ground electrode W2 stops, and thereafter, the shape of the ground electrode W2 is changed to a bending deformation in a direction to reduce the spark gap g.
Therefore, it is possible to continuously perform the gap interval adjusting process by using this.

Here, the amount of torsional deformation of the ground electrode W2 is
When the pressure is released, a part is lost due to the spring back, and in consideration of this, the relative rotation angle is set to Δεa + γ
(Γ is an extra rotational displacement in consideration of springback). Further, it is also possible to adopt a method in which the relative rotation angle is set to be larger, and the pressing is stopped halfway when the torsional deformation of the ground electrode W2 has progressed to the position where the eccentricity is eliminated.

As described above, it is more advantageous to rotate the spark plug W to be processed in terms of simplifying the structure of the apparatus, but the bending device 14 can be moved around the spark plug W to be processed. In order to obtain a relative rotation state equivalent to that of FIG.
The method of rotating the bending device 14 side with the side of the
A method of rotating both the bending device 14 and the spark plug W to be processed may be employed. As will be described later, the bending device 14 is also used for adjusting the gap interval. However, a separate bending device may be provided for adjusting the eccentricity.

On the other hand, in the method shown in FIG. 23, the eccentricity adjusting tool (16a) is configured as a holding tool for preventing the ground electrode (W2) from moving in the width direction, and the reference angle position (K) is set to the ground electrode (W). W2) is set substantially parallel to the direction of the central axis (ζ). Then, in a state where the ground electrode (W2) of the spark plug (W) to be processed is held by the eccentricity adjusting tool (16a), a predetermined angle (Δεa) from the reference angular position (K) in a direction in which the amount of eccentricity is reduced. Or the spark plug W to be processed by Δεa + γ) in anticipation of springback
And the eccentricity adjusting tool (16a) are relatively rotated. Here, as shown in FIG. 1, an eccentricity correction device 16 having a holding tool 16a that can approach and separate from the ground electrode W2 from the rear side is provided. (The approach and separation mechanism of the holding tool 16a is: For example, a device similar to the bending device 14 in FIG. 8 can be employed. Then, the holding tool 16a is connected to the ground electrode W.
2 and the groove-shaped recess 16b formed on the front end face is fitted to the ground electrode W2 from the rear side. When the spark plug W to be processed is rotated in this state, the ground electrode W2 is prevented from rotating because the ground electrode W2 is fitted and held by the holding tool 16a. It is torsionally deformed. Here, the rotation of the spark plug W to be processed is again performed by rotating the work holder 3.
04 is performed.

The holding tool 16a having the concave portion 16b
Instead, as shown in FIG. 24, the gripping tools 16c, 16 which can be relatively approached / separated in the width direction of the ground electrode W2.
c may be used. In this case, the ground electrode W2 may be gripped by the gripping tools 16c, 16c, and the spark plug W to be processed may be rotated by the rotary work holder 304 in this state. Further, as shown in FIG. 25, the spark plug W to be processed may be fixed, and the gripping tools 16c, 16c may be rotated. In addition, the gripping tools 16c, 16
Instead of rotating c around the spark plug W to be processed, a method of sliding the c in the eccentric reduction direction may be adopted.

As shown in FIG. 26, an eccentricity adjustment bending process may be performed by pressing the ground electrode W2 in the width direction using a bending metal fitting 58 as an eccentricity adjustment processing tool. Here, as shown in (b), the spark plug W to be processed is substantially 90 degrees around the center axis O of the center electrode W1 with reference to the angular position at the time of the gap adjustment processing shown in (a).
And the bending metal 58 presses the ground electrode W2 in the width direction. In this method, if the amount of eccentricity δ shown in FIG. 15 is adopted, the pressing direction of the bending metal fitting 58 matches the direction of the amount of eccentricity δ, so that the calculation of the pressing stroke is easy. The direction of the pressing is determined according to the sign of δ. In this case, the stroke is δ + κ in consideration of the springback of the ground electrode W2 after the pressure is released.
(Κ is an extra pressing stroke in consideration of springback).

Referring back to FIG. 16, when the eccentricity adjustment is completed, the work W is moved to the photographing position again in S8, and it is checked whether the eccentric state has been eliminated. If the eccentric state has not yet been resolved, the process returns to S6, and the following processing is repeated. On the other hand, if the eccentric state has been eliminated, S
Proceeding to 10, the value of the spark gap interval g is determined, and then gap interval adjustment processing is performed. Further, by reading out a target value of the spark gap interval g (for example, stored in the ROM 103 (FIG. 9)) and comparing it with the measured gap measurement value g, the bending punch 54 of the bending device 14 (FIG. 8) is adjusted. Calculate the stroke for pressing. In S11,
The workpiece W is moved and positioned to the bending position of the bending device 14, and the bending device 14 of FIG. 8 receives a command from the main control unit 100 and the value of the adjustment pressing stroke, and uses the motor 56 (FIG. ) Is actuated to apply pressure to the ground electrode W2 to adjust the gap interval by bending. At this time, the main control unit 100
4 (FIG. 9) is incremented.

When the pressing is completed, the process proceeds to S12 and the work W
Is moved to the photographing position again to measure the gap interval. Then, the gap interval measured in S13 is compared / determined with the target value. If the gap interval has not reached the target value in S24, the process returns to S10 via S14, and thereafter, gap adjustment bending and gap measurement are performed by the same processing. Repeat. If the number of bendings n does not reach the target value even if it exceeds the upper limit value nmax in S14, the process is terminated as abnormal and the process proceeds to S15 to discharge the workpiece. On the other hand, if the gap interval reaches the target value in S13, it is determined that the gap interval is normal, and S1
6 and S17, and as shown in FIG. 3B, the rotating work holder 304 is set at a predetermined angle (90 ° in the present embodiment).
By rotating, the next ground electrode W2 is moved and positioned at the processing position. Then, returning to S3, the above steps are repeated. Thereby, each ground electrode W2 of the multipolar plug is
The eccentricity adjustment, the inspection of the gap interval, and the adjustment processing are sequentially performed. Then, if all the processes for the ground electrode W2 are completed in S15, the process proceeds to S32, where the work is discharged, and the process ends.

Next, an example of the gap measuring process is shown in FIG.
This will be described with reference to the flowchart of FIG. First, at L1 in FIG. 19, information on the front edge line E2 of the ground electrode W2 (given as a set of position coordinates of each point on the edge line).
And information on the outer peripheral edge line E of the center electrode W1 (center coordinates O
And given as radius r0). Then
As shown in FIG. 29, at L2, the scan angle position θ
To the reference angle position θ0 (the reference line is, for example, O and the ground electrode W2
Line connecting one end point of the leading edge line E2 of
In step 3, a reference line L passing through the center O at the angular position θ (= θ0) is generated. Then, the coordinates of the intersection P with the edge line E2 of the ground electrode W1 are obtained at L4, and the distance R = OP from the center coordinates O to P is calculated at L5. The set of values of R and θ is stored in the RAM 114 of the control unit 110 (FIG. 10). Next, at L6, the angular position is increased by a fixed minute angle Δθ, a new reference line L is generated at L7, the process returns to L4 via L8, and the intersection with E2 is obtained to calculate R in the same manner. The value is stored in the RAM 114 in association with the θ value at that time. This process is repeated until no intersection of L and E2 occurs.

As a result, as shown in FIG. 20, a set of R values (θ,
R) = (θ1, R1), (θ2, R2), ‥‥‥ (θn,
Rn) is stored. The set of these values represents the undulation level profile of the front edge line E2 of the ground electrode W2 by plotting as a point on the θ-R plane (see also FIG. 29).

Next, the adjustment pressing stroke calculation step (S10) and the gap interval adjustment processing step (S11) in FIG. 16 will be described. FIG. 28 is a flowchart showing an example of the adjustment pressing stroke calculation process, and FIG. 30 is an explanatory diagram thereof. First, at C1, the gap interval is set to the minimum value g.
The point that becomes a, that is, the set of (θ, R) of the minimum interval point u is read from the RAM 114 in FIG. Θ in this case is
It is represented by an angle from the reference angle position θ0.

Next, consider a projection plane π orthogonal to the center axis of the center electrode W1, and consider a state in which the tip edge line of the ground electrode W2 is projected on this projection plane π. As shown in FIG. 7, since the shooting direction of the camera 40 coincides with the direction of the center axis of the center electrode W1, the projection plane π is equivalent to the view plane of the camera 40, in other words, the display screen of the shot image. Can be considered. First, at C2 in FIG. 28, the ground electrode W
The center axis 2 of 2 is set on the projection plane π. ζ can be determined as, for example, a line that bisects an angle section from the reference angle position θ0, which is the angular position of one end point of the edge line E2, to θn, which is the angular position of the opposite end point. In addition,
The pressing direction of the pressing punch is set in a direction substantially parallel to the ground electrode center line 接地 on the projection plane π.

Then, at C4, the θ value of the minimum gap interval point u is converted into a value of an angle θu between the ground electrode center axis ζ and a straight line J connecting the center electrode center axis O and u,
At C5, the projection length x of the adjustment pressing stroke on the projection plane π (hereinafter referred to as x (θu) to indicate that it is a function of θu) so that the target gap value ga is obtained in the direction of the straight line J. Write), the following calculation formula (calculated by or which substantially calculation algorithm equivalent results): x (θu) = Rcosθu- (R 2 cos 2 θu- {R 2 - (r0 + ga) 2 ｝ ² ) ^1/2 ‥‥ where r0 is the radius of the edge line E of the center electrode W1,
R is the distance from O to point u. This calculation formula is shown in FIG.
As shown in FIG. 9, the equations (1) and (2) in the figure are geometrically transformed based on the assumption that the edge line E2 is translated by x (θu) along ζ and moves to E2 ′ by pressing. And solving for x. In addition,
φ is the angular displacement of point u when E2 moves to E2 '.

It should be noted that when the value of x (θu) achieved by pressing is small, φ is also small, and it can be considered that u substantially holds the angular position θu even after pressing. In this case, as shown in FIG. 30, if the gap interval at the point u before pressing is g and the gap interval after pressing, that is, the target gap interval is ga, the target displacement amount λ (in the radial direction) of the point u. Can be represented by g-ga. Using this, x (θu) can be more easily calculated as x (θu) = λ / cos θu ‥‥.

Next, the process proceeds to C5 in FIG. 28, where the adjustment pressing stroke σ of the pressing punch 34 is calculated using x (θu). First, the adjustment pressing stroke σ ′ without considering springback in the adjustment pressing stroke direction of the ground electrode W2 can be obtained as follows, for example.
That is, as shown in FIG. 8, the adjustment pressing stroke direction OP of the pressing punch 54 is set obliquely so as to form a predetermined angle B (approximately 45 °) with respect to the reference plane H (that is, the projection plane π). Then, x (θu) is the bending metal fitting 58
Σ ′ is calculated geometrically as σ ′ = x · sinB し て, assuming that it corresponds to the amount of movement of the tip end surface along the reference plane H (in this case, the amount of movement in the horizontal direction). be able to. Then, by adding the expected springback amount ν to σ ′, the final adjustment pressing stroke σ is calculated as σ = σ ′ + ν ‥‥.

The bending for correcting the gap interval in the multipolar plug is performed by pressing the ground electrode using the bending punch approaching or separating in the gap reducing direction as described above. In this case, if the current gap interval is g and the target gap interval is ga, the gap interval must be reduced by Δg = g−ga by pressing. However, conventionally, the adjustment pressing of the bending process is performed according to the value of Δg. The stroke was determined uniformly. However, in the multi-pole plug, the gap interval is a value measured in the radial direction of the center electrode, and the gap interval minimum point u only needs to match the direction of the adjustment pressing stroke in the circumferential direction of the center electrode. In this case, even if the adjustment pressing stroke is constant, the desired gap reduction amount Δg is not always obtained at the gap interval minimum point u, and there is a problem that a gap interval defect easily occurs.

However, in the above-described method, the adjustment pressing stroke of the bending process is not uniformly determined according to the gap reduction amount as in the related art, but is set so as to increase as the value of θu increases. In adjusting the gap interval of the multi-pole plug, even if the minimum gap interval position does not coincide with the direction of the adjustment pressing stroke in the circumferential direction of the center electrode, a sufficient gap reduction amount can always be achieved, and as a result, the gap interval defect can be reduced. It can be made hard to occur.

When the eccentricity occurs between the ground electrode W2 and the center electrode W1, the position of the minimum gap interval point u changes as described with reference to FIG. Is adjusted in accordance with the value of θu, the effect is directly affected, and the gap interval accuracy is reduced. However, in this embodiment, the eccentricity adjustment is performed prior to the gap interval adjustment, so that such a problem is extremely unlikely to occur.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a spark plug manufacturing apparatus according to the present invention.

FIG. 2 is a side sectional view of the moving table mechanism.

FIG. 3 is a plan view illustrating the operation of the rotating work holder.

FIG. 4 is a plan view showing a ground electrode alignment mechanism together with its operation.

FIG. 5 is a plan view and a side view of the reference portion value measuring device.

FIG. 6 is an explanatory diagram showing a main part of a workpiece W and a projection position of a laser beam to the main part.

FIG. 7 is a front view and a side view of a main part of the imaging / analysis unit.

FIG. 8 is a side view of the bending device.

FIG. 9 is a block diagram showing an electrical configuration of a main control unit of the manufacturing apparatus of FIG. 1;

FIG. 10 is a block diagram illustrating an electrical configuration of an image analysis unit of the imaging / analysis unit.

FIG. 11 is a block diagram showing an electrical configuration of the rotary work holder.

FIG. 12 is a block diagram showing an example of an electrical configuration of the bending device.

FIG. 13 is a schematic view showing an example of a camera field of view.

FIG. 14 is an explanatory diagram illustrating the concept of eccentricity.

FIG. 15 is an explanatory diagram showing another concept of eccentricity.

FIG. 16 is a flowchart showing a flow of processing of the manufacturing apparatus of FIG. 1;

FIG. 17 is a flowchart showing an algorithm for calculating the amount of eccentricity based on the concept of FIG. 14;

FIG. 18 is a flowchart showing an algorithm for calculating the amount of eccentricity based on the concept of FIG.

FIG. 19 is a flowchart showing the flow of a gap measurement process.

FIG. 20 is a diagram conceptually illustrating data of a ground electrode edge line.

FIG. 21 is a diagram schematically showing a method for determining the center of the edge line of the tip of the ground electrode.

FIG. 22 is an explanatory view showing a first example of an eccentricity adjustment step.

FIG. 23 is an explanatory view showing a second example.

FIG. 24 is an explanatory view showing a third example.

FIG. 25 is an explanatory view showing a fourth example.

FIG. 26 is an explanatory view showing a fifth example.

FIG. 27 is a view for explaining the position where the gap interval is minimum and the effect of eccentricity on its size.

FIG. 28 is a flowchart showing the flow of an adjustment pressing stroke calculation process.

FIG. 29 is an explanatory diagram showing the principle of geometric calculation of x (θu).

FIG. 30 is also an explanatory view showing the simple method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Spark plug manufacturing device W Work (spark plug to be treated) W1 Center electrode W2 Ground electrode g Spark gap E1, E2 electrode edge line 14 Bending device (eccentricity adjusting processing means, gap interval adjusting processing means) 15 Photographing / analyzing unit (eccentricity) Measuring means, spark gap measuring means) 40 Camera (photographing means) 100 Main control section 110 Image analyzing section (inspection information generating means, smoothing processing means, gap interval calculating means, adjustment pressing stroke determining means) 210 Field of view 300 Traverser (transportation) Means) 304 rotating work holder (rotation holding unit)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichiro Mitsumatsu 14-18 Takatsuji-cho, Mizuho-ku, Nagoya City, Aichi Japan F-term (reference) 5G059 AA10 CC01 EE15

Claims (8)

[Claims] An end of a ground electrode whose base end is connected to a metal shell and whose front end is bent sideways faces a front end of a center electrode to form a spark gap therebetween. The following steps are performed on the spark plug to be processed, while transporting the spark plug along a predetermined transport path in a rotatable state around the axis of the center electrode, that is, the spark gap and its peripheral portion. An eccentricity measuring step of photographing with a camera and measuring the widthwise eccentricity of the tip of the ground electrode with respect to the tip of the center electrode from the captured image, and performing a bending process on the grounding electrode in a direction in which the eccentricity is reduced. An eccentricity adjusting processing step performed by using an eccentricity adjusting processing tool, a spark gap for photographing the spark gap and its peripheral portion with a camera, and measuring an interval of the spark gap from the photographed image. A measuring step, based on the measured value of the spark gap interval, a bending process of adjusting the spark gap interval with respect to the ground electrode in a direction to reduce the spark gap interval, a gap adjusting process of using a gap adjusting tool. So that the direction of the bending force at the time of the eccentricity adjustment process and the direction of the bending process at the time of the gap interval adjustment process are different from each other, so that the rotation of the spark plug to be processed around the axis of the center electrode is performed. The position relationship between the eccentricity adjusting tool and the ground electrode in the eccentricity adjusting process and the positional relationship between the gap adjusting tool and the ground electrode in the gap interval adjusting process are individually adjusted. A method for manufacturing a spark plug. 2. An arc-shaped distal end surface of a ground electrode whose base end is connected to a metal shell and whose distal end is bent sideways is opposed to and between the distal end side surface of a cylindrical center electrode. The spark plug is formed as a spark plug to be processed, and the following processes are performed. That is, the spark gap is photographed by a camera from the center electrode front end side, and from the photographed image, the ground electrode tip portion with respect to the center electrode tip portion. An eccentricity measuring step of measuring the amount of eccentricity in the width direction, and a bending process in which the eccentricity is reduced with respect to the ground electrode using an eccentricity adjusting tool. For the reduced spark plug to be processed, the spark gap and the surrounding area are photographed by a camera,
On the basis of the captured image, a spark gap measuring step of measuring a minimum distance between an outer peripheral edge line of the center electrode and a tip edge line of the ground electrode as an interval of the spark gap, and a value of the measured spark gap interval. And a gap adjusting step of performing a bending process for adjusting the spark gap interval with respect to the ground electrode using a gap adjusting tool. 3. In the eccentricity adjusting step, the eccentricity adjusting tool and the spark plug to be processed are disposed so as to be relatively rotatable around an axis of the center electrode, and the eccentricity adjusting tool has a direction in which the amount of eccentricity is reduced. In order to apply a bending force to the ground electrode, prior to the bending and / or during the bending, from a predetermined reference angular position between the eccentricity adjusting tool and the spark plug to be processed, 3. The spark plug manufacturing method according to claim 1, wherein a rotation operation is performed to relatively rotate the processing tool and the spark plug to be processed around the axis by a predetermined angle determined according to the measured eccentricity. 4. . 4. In the eccentricity adjusting step, the eccentricity adjusting tool is arranged so as to be able to approach and separate from the ground electrode from a side opposite to a side where the spark gap is formed, and the reference angle position is set to the reference angle position. The spark plug to be processed is set to be substantially parallel to the center axis direction of the ground electrode, and the spark plug to be processed is set in advance in the opposite direction to the eccentric direction of the ground electrode with respect to the center electrode with respect to the eccentricity adjusting tool, from the reference angle position. 4. The spark plug manufacturing method according to claim 3, wherein the eccentric amount is reduced by relatively rotating the eccentricity adjusting tool by a predetermined angle in that state, and bringing the eccentricity adjusting tool close to the ground electrode and pressing it. 5. In the eccentricity adjusting step, the eccentricity adjusting tool is configured as a holding tool for preventing movement of the ground electrode in the width direction, and the reference angle position is substantially the same as the central axis direction of the ground electrode. In the state where the spark plug is set in parallel and the ground electrode of the spark plug to be processed is held by the eccentricity adjusting tool, the spark plug to be processed by a predetermined angle from the reference angle position in a direction in which the amount of eccentricity is reduced. The spark plug manufacturing method according to claim 3, wherein the eccentricity adjusting tool and the eccentricity adjusting tool are relatively rotated. 6. A spark gap is formed between the base electrode connected to the metal shell and the tip of the ground electrode whose tip is bent to the side facing the tip of the center electrode. A rotation holding unit that detachably holds the spark plug to be processed, and rotates the spark plug around the center axis of the center electrode in that state; and a rotation holding unit that holds the spark plug to be processed in a predetermined transport path. Transport means for transporting the spark gap and its peripheral portion along the transport route, and taking a picture of the spark gap and its peripheral portion with a camera, and from the captured image, the width direction of the ground electrode tip with respect to the center electrode tip. Eccentricity measuring means for measuring the amount of eccentricity; eccentricity adjusting processing means for performing bending in a direction in which the eccentricity is reduced on the ground electrode using an eccentricity adjusting tool; and the spark gap and its periphery. A spark gap measuring means for photographing a portion with a camera and measuring the spark gap interval from the photographed image; and a direction for reducing the spark gap interval with respect to the ground electrode based on the measured value of the spark gap interval. A gap interval adjusting means for performing the bending process using the gap adjusting tool is arranged, and the direction of the bending force at the time of the eccentricity adjusting process and the direction of the bending process at the time of the gap interval adjusting process are mutually aligned. To be different, based on the rotation of the spark plug to be processed around the central axis of the center electrode, the positional relationship between the eccentricity adjusting tool and the ground electrode in the eccentricity adjusting step,
A spark plug manufacturing apparatus for individually adjusting the positional relationship between the gap adjustment processing tool and the ground electrode in the gap interval adjustment processing step. 7. An arc-shaped distal end surface of a ground electrode whose base end is connected to a metal shell and whose distal end is bent sideways faces the distal end side surface of a columnar center electrode and between them. The spark gap of the spark plug to be processed is taken from the center electrode tip side by a camera, and the width of the ground electrode tip with respect to the center electrode tip is taken from the captured image. Eccentricity measuring means for measuring the amount of eccentricity in the direction, eccentricity adjusting processing means for performing bending processing with respect to the ground electrode in a direction in which the eccentricity is reduced, using an eccentricity adjusting tool, after reducing the eccentricity For the to-be-processed spark plug, the spark gap and its peripheral portion are photographed by a camera,
Spark gap measuring means for measuring the minimum distance between the outer peripheral edge line of the center electrode and the leading edge line of the ground electrode as an interval of the spark gap based on the captured image, and a value of the measured spark gap interval. And a gap adjusting means for performing a bending process for adjusting the spark gap interval with respect to the ground electrode using a gap adjusting tool. 8. The spark plug manufacturing apparatus according to claim 6, wherein the eccentricity adjusting tool is shared with the gap adjusting tool.