JP2002313525A - Method and device for manufacturing spark plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method and a manufacturing device of a spark plug capable of accurately calculating a gap space regardless of tilting of a work (a spark plug) with respect to a photographing means at measuring the gap space, thereby producing the spark plug at high accuracy. SOLUTION: Plural outline measuring points for positioning respective outlines are determined in a ground electrode side spark gap forming part (a tip edge E2 ) facing a spark gap of a ground electrode W2 side and in a center electrode side spark gap forming part (a tip edge E1 ) of a center electrode W1 side. One of the outline measuring points is determined as a reference point in one of the spark gap forming parts. An outline measuring point having the shortest distance from the reference point is found out in the other spark gap forming part. The gap space is determined based on the shortest distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in the production of a so-called parallel electrode type spark plug, in forming a spark gap and adjusting the gap, after a preliminary press is applied to the ground electrode, the gap interval is set to a target while monitoring the gap interval with a CCD camera or the like. A method of repeatedly pressing the ground electrode until the value reaches a value is used.

[0003]

When the gap is monitored by a CCD camera or the like when the gap is adjusted, the installation direction of the spark plug (specifically, the axis of the center electrode is adjusted in accordance with the coordinate system on the captured image). Direction) is set. That is, if a measurement method is used in which any one of the coordinate directions (for example, the Y direction) in the coordinate system of the image coincides with the direction of the center electrode, the edge between the center electrode and the ground electrode in the coincident coordinate direction. The gap interval is calculated by the measurement.

However, as shown in FIG. 20, when the workpiece W is photographed in such a manner that the axis of the center electrode is inclined with respect to the direction (Y direction in the drawing) which is the reference of the gap measurement, specifically, For example, in the case where the axis is inclined left and right with respect to the direction of photographing by the photographing means, the direction in which the gap interval is to be measured is inclined with respect to the reference direction. Therefore, there is a possibility of causing a dimensional error between the measured value g "according to the actual value g _r and the image due to the inclination. Further, as shown in FIG. 8, the direction of photographing by photographing means Even when the workpiece is photographed with the axis tilted back and forth, a dimensional error may similarly occur.

[0005] The problem to be solved by the present invention is that in measuring the gap interval, an accurate gap interval can be calculated irrespective of the inclination of the work (spark plug) with respect to the photographing means, and the spark plug is calculated using the calculated gap interval value. To provide a spark plug manufacturing method and a manufacturing apparatus capable of manufacturing a spark plug with high precision.

[0006]

In order to solve the above problems, the present invention provides a center electrode disposed in an insulator, a metal shell disposed on the outer periphery of the insulator, One end is coupled to the distal end surface of the metal shell, while the other end is bent sideways so that the side surface faces the distal end surface of the center electrode, so that a spark is formed between the central electrode and the distal end surface. In order to manufacture a spark plug including a ground electrode forming a gap, a photographing step or photographing means for photographing the spark gap by photographing means and a reference point are determined at one place based on image information obtained by the photographing. A ground electrode side spark gap forming portion facing the spark gap on the ground electrode side determined by a plurality of measurement lines passing through the reference point; and a center facing the spark gap on the center electrode side. A gap interval calculating step or a gap interval calculating means for determining the gap interval based on a distance from a pole-side spark gap forming unit; and a post-processing step or a post-processing for performing a predetermined post-processing based on the calculated gap interval. A method and an apparatus for manufacturing a spark plug, characterized by including means.

When the gap interval is determined as in the above method, for example, as shown in FIG. 20, when the spark plug is photographed in an inclined form on the photographed image, that is, when the spark plug is Even when the axis of the center electrode is inclined left and right on the image plane,
The gap interval can be accurately measured. That is, no error occurs due to the inclination in the photographed image plane.

A center electrode disposed in the insulator;
A metal shell disposed on the outer periphery of the insulator, one end of which is coupled to the front end surface of the metal shell, while the other end is bent sideways so that the side surface faces the front end surface of the center electrode. Thus, in order to manufacture a spark plug including a ground electrode that forms a spark gap with the center electrode tip surface, a photographing step or photographing means for photographing the spark gap by photographing means, and the photographing step is performed. One of a ground electrode side spark gap forming portion facing the spark gap on the ground electrode side and a center electrode spark gap forming portion facing the spark gap on the center electrode side based on the image information. A reference point on the outline is determined at one place, and a measurement point on the outline at which the distance from the reference point is the shortest in the other spark gap forming section is found. Including a gap interval calculating step or gap interval calculating means for determining the gap interval based on the shortest distance, and a post-processing step or post-processing means for performing a predetermined post-processing based on the calculated gap interval. A characteristic spark plug manufacturing method and apparatus may be used.

If the gap interval is determined as in the above method, the shortest distance between the gaps can be obtained with high accuracy. That is, no error occurs due to the inclination in the photographed image plane, which contributes to high-precision gap adjustment.

On the photographed image, an apparent dimension of a gap interval (hereinafter, also referred to as an apparent gap dimension).
And an apparent dimension on a photographed image of a predetermined measurement reference portion in a part of the spark plug (hereinafter, also referred to as a measurement reference portion apparent size) and a known standard size of the measurement reference portion (hereinafter, referred to as The apparent gap size may be corrected based on the measurement reference portion standard size) to calculate the gap interval. Specifically, for example, the dimensional error of the apparent gap dimension that occurs based on the fact that the spark plug is photographed in the form of being inclined in the direction of photographing by the photographing means is changed to the measurement standard part apparent dimension and the measurement standard part standard dimension. A correction method based on the correction can be used.

According to this method, even if the spark plug is photographed in such a manner that the spark plug is inclined in the photographing direction, a value very close to the actual dimension can be obtained by correction, and the gap interval can be reduced. It can be set with high accuracy. By using this method together with the method of calculating the gap interval based on the measurement points and the reference points on the outline as described above, it is possible to cope with both the inclination in the photographing direction and the inclination to the left and right with respect to the photographing direction. It becomes.

[0012]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. FIGS. 1A and 1B are a plan view and a side view conceptually showing an embodiment of a spark plug manufacturing apparatus (hereinafter, simply referred to as a manufacturing apparatus) of the present invention. The manufacturing apparatus 1 includes a linear conveyor as a transport mechanism for intermittently transporting a to-be-processed spark plug (hereinafter, also referred to as a workpiece) W along a transport path C (which is linear in this embodiment). 300, and the respective steps for forming the spark gap of the work W, that is, the work carrying mechanism 11 as the spark plug carrying mechanism to be processed, and the ground electrode of the work W are positioned at predetermined positions along the transport path C. A ground electrode alignment mechanism 12, a tip surface position measuring device 13 for measuring the tip surface position of the center electrode, a temporary bending device 14 for temporarily bending the ground electrode, a main bending device 15 for performing the main bending, and a work W after the processing is completed. The work discharge mechanism 16 for discharging the waste and the rejected goods discharge mechanism 17
They are arranged in this order from the upstream side in the transport direction. The linear conveyor 300 includes a carrier 302 on which a work W is detachably mounted on a chain 301 as a traveling member.
Are attached at predetermined intervals. Chain 3
01 is intermittently driven by the conveyor drive motor 24, whereby each carrier 302, ie, the work W, is intermittently transported along the transport path C.

[0013] the workpiece W, as shown in FIG. 2, a cylindrical metal shell W _3, the insulator W ₄ front end portion and the rear end portion is fitted into the metallic shell W ₃ so as to _protrude, insulation Body W
₄ , a central electrode W ₁ inserted in the axial direction, and a metal shell W
₃ at one end is provided with a ground electrode W ₂ such that the other end extends in the axial direction of the center electrode W ₁ together are joined by welding or the like. The ground electrode W _2, the tip end of the following steps are bent toward the tip face of the center electrode W _1, a parallel electrode type spark plug spark gap is formed. Carrier 3
A cylindrical holder 23 having an open upper end is integrally attached to the upper surface of the cover 02. The work W is removably inserted into the holder 23 from the rear end side, the hexagonal portion W ₆ of the metal shell W ₃ is supported by the opening peripheral portion of the holder 23, and the ground electrode W ₂ side faces upward. It is conveyed together with the carrier 302 in a state where it stands up.

The work carrying mechanism 11, the work discharging mechanism 16 and the rejected goods discharging mechanism 17 of FIG. 1 are set, for example, as shown in FIG. 2 on the side of the linear conveyor 300 (FIG. 1) in the transport direction C. It is configured as a transfer mechanism for transferring the work W between a work supply unit or a work discharge unit (provided at a position J in the drawing) and the holder 23 positioned in the carry-in or discharge mechanism. The transfer mechanism 35 includes a chuck hand mechanism 36 held up and down by an air cylinder 37, and an advance / retreat drive mechanism 39 that drives the chuck hand mechanism 36 to advance / retreat in the radial direction of the circumferential path C by an air cylinder 38 or the like. It consists of.

Next, the ground electrode alignment mechanism 12, based on the ground electrode W _1, the spark plug is rotated by an actuator such as a motor, it is intended to position the predetermined aligned position. The tip face position measuring unit 13 is for measuring the front end surface position of the center electrode W ₁ prior to the temporary bending to be described later, provided with a position detecting sensor 115 as shown in FIG. 3 (a) . The work W is mounted on the linear conveyor 300 and the holder 2 is fixed in height.
To 3, it is mounted in a state where the ground electrode W ₂ erected so that the upper side. Then, the position detection sensor 115 (for example, composed of a laser displacement sensor or the like) is held at a fixed height by a frame for measuring the height position of the distal end surface, so that the center electrode is applied to the loaded work W. the distal end surface position of the W ₂ is measured from above.

Further, the provisional bending apparatus 14, as shown in FIG. 3 (b) and (c), based on the front end surface position of the center electrode W ₁ of the workpiece W detected by the position detection sensor 115, and the distal end surface The temporary bending spacer 42 is positioned and arranged in a state where a substantially constant gap d is formed between the temporary bending spacers 4.
The front end side of the ground electrode W ₂ to 2, the center electrode W ₁ with bending punch 43 performs a temporary bending by pressing from the opposite side. Bending punch 43, for example by punching drive unit such as an air cylinder, not shown, toward and away driving for temporary bending with respect to the ground electrode W _2. Positioning the temporary bending form that caused the predetermined gap d without abutting the spacer 42 to the front end surface of the center electrode W _1, provisional bend against the said spacer 42 to the ground electrode W ₂ by the punch 43 bent in that state By performing the process, defects such as chipping and scratches on the electrode are extremely unlikely to occur,
A high yield can be achieved.

FIG. 4 shows an example of the bending apparatus 15. The work W placed on the holder 23 is carried into the device 15 by the linear conveyor 300 and positioned at a predetermined processing position. Then, at a position corresponding to the processing position of the workpiece W, the gap photographing / analysis unit 3 is provided on one side of the transport path of the linear conveyor 300, and the bending mechanism 5 serving as a main body of the gap adjusting means is provided on the opposite side of the linear conveyor 300. Each is arranged.

A gap photographing / analyzing unit (hereinafter simply referred to as a photographing / analyzing unit) 3 is mainly used in a photographing process, and is connected to a photographing camera 4 supported on a frame 22 and functioning as photographing means. The image analysis unit 110 (FIG. 11) to be performed is configured as a main part. As shown in FIG. 11, the image analysis unit 110 includes an I / O port 111, a CPU 112 connected thereto,
3. It can be constituted by a microprocessor including a RAM 114 and the like. The CPU 112 is a main component of a post-processing unit, a gap interval calculating unit, a gap dimension correcting unit, an apparent gap dimension calculating unit, an electrode edge line determining unit, and a smoothing processing unit by the image analysis program 113a stored in the ROM 113. Things. Returning to FIG.
The photographing camera 4 is, for example, a two-dimensional CCD sensor 4a (FIG. 1).
1) is configured as a CCD camera having an image detecting unit, and the center electrode W ₁ of a workpiece illuminated by the illumination device 200, and the ground electrode W ₂ facing thereto, their center electrode W ₁ and the ground electrode W ₂ and a spark gap g formed between them.

On the other hand, the bending mechanism 5 has a main body case 52 mounted on a front end surface of a cantilever type frame 51 mounted on a base 50 of the apparatus. A movable base 53 is housed in the main body case 52 so as to be able to move up and down, and a pressing punch 54 is attached to the movable base 53 via a rod 58 so as to protrude from a lower end surface of the main body case 52. . Then, a screw shaft (for example, a ball screw) 55 screwed from above into a female screw portion 53a formed on the movable base 53 is rotated in both forward and reverse directions by a pressing punch driving motor 56, so that the pressing punch 54
But it will approach and away from the ground electrode W ₂ of the workpiece W. Further, an arbitrary height position can be held corresponding to the stop position of the screw shaft drive. The rotation transmitting force of the pressing punch drive motor 56 is controlled by the timing pulley 5.
6a, timing belt 57 and timing pulley 55
is transmitted to the screw shaft 55 via a.

As shown in FIG. 3 (c), for example the tip with respect to the ground electrode W ₂ which provisional bend has been in the form of faces obliquely upward, as shown in FIG. 9, it is brought closer to the pressing punch 54 by pressing, the bending process is performed to form the main steps of the gap adjusting step so that the tip portion of the ground electrode W ₂ becomes substantially parallel to the front end surface of the center electrode W _1. Then, the interval of the spark discharge gap is adjusted so as to reach the target gap interval. In addition, as shown in FIG. 4, at the time of performing the main bending process, the work W is configured to be sandwiched and fixed between the pressing members 60 and 61 from both sides in the axial direction. Then, the image information acquired in the photographing process in the final bending process is used.

Next, the photographing step for obtaining image information used in the main bending (gap adjusting step) will be described in more detail. As shown in FIG. 5A, the illumination device 200 includes a workpiece W in which a spark gap is formed such that illumination light passes through the spark gap in a photographing process.
(Spark plug) is arranged opposite to the tip. In the embodiment shown in FIG. 5, a planar light emitting type illumination device is used. Note that the lighting device 200 is provided with a light shielding unit 203 for limiting the illumination range to a predetermined range. Due to the light-shielding portion 203, the illuminating range of the illuminating light traveling toward the photographing camera 4 via the spark plug is limited to a predetermined range (H ₁ ) in the axial direction of the center electrode. The direction in which the photographing camera 4 performs photographing is a direction A2 substantially orthogonal to the axial direction A1 of the center electrode.
Then, the lighting device 20 sandwiches the spark plug tip.
0 by the photographing camera 4 arranged on the side opposite to the center electrode W.
₁ and taking a spark gap formed by the ground electrode W _2. The photographing camera 4 includes a work W as shown in FIG.
Of the spark gap g at a predetermined magnification, and overall the leading edge E ₁ of the center electrode W ₁ facing the spark gap g, as well of the leading edge E ₂ of the front end surface of the ground electrode W _2, faces the spark gap portion, and so that the shooting to include edge E ₃ on the opposite side to the side facing the spark gap of the ground electrode W _2.

Hereinafter, the main processing flow in the spark plug manufacturing method of the present invention using the manufacturing apparatus 1 will be described with reference to the flowchart of FIG. It should be noted that the manufacturing apparatus 1 performs C as shown in FIG.
The main control unit 100 is configured to include the PU 102, the ROM 103, and the RAM 104, and the main control unit 100 is connected to each mechanism and device via the I / O port 101.

The flow will be described below. First, when the ground electrode alignment step (S1) is completed, the carrier 302 is moved to the work mounting position, the work W is mounted on the work holder, and the work W is chucked (S2). Subsequently, in S3, the workpiece W is transported from the linear conveyor 300 to the position of the tip end surface position measuring device 13. The tip surface position measuring device 13 measures the tip position as shown in FIG. Next, in S4, the above-described temporary bending step shown in FIGS. 3B and 3C is performed.

At S5, gap photographing / analysis processing is performed. Here, the work W is moved and positioned at the photographing position of the photographing / analysis unit 3, and the image analysis unit 110 (FIG. 1)
1) captures an image from the photographing camera 4 and analyzes the image to obtain a value of the spark gap g (details will be described later). Next, in step S6, a target value of the spark gap g (for example, stored in the ROM 103 (FIG. 10)) is read out and compared with the measured gap measurement value g, whereby the pressing punch 54 of the bending apparatus 15 (FIG. 4) is read. The stroke for the adjustment pressing is calculated.

In S7, the work W is moved to the final bending device 1 shown in FIG.
5 is moved to the bending position, and the main control unit 100
Receiving an instruction with the value of the adjustment pressing stroke from, by actuating the motor 56, the press was added to the ground electrode W _2, to adjust the gap distance by bending. At this time, the main controller 100 increments the value n of the number of times of bending stored in, for example, the RAM 104 (FIG. 10).

Next, in step S8, the work W is moved to the photographing position again, and the gap interval is measured again. And S9
The gap interval measured in step is compared with the target value and determined. If the gap interval has not reached the target value, the process returns to S5 via S10, and thereafter, bending and gap measurement are repeated by the same processing. If the target number is not reached even if the number of bendings n exceeds the upper limit value nmax in S10, the process is terminated as an abnormality, and the process proceeds to S11 to discharge defective products. On the other hand, if the gap interval reaches the target value in S9, it is determined that the gap is normal, the process proceeds to S11, the work is discharged, and the process ends.

Next, the gap photographing / analysis processing will be described. The gap photographing / analysis processing (S5, S
8) is roughly divided into an image recognition process (S100) and a subsequent smoothing process (S11) as shown in FIG.
0), gap measurement processing (S120), and correction processing (S120).
130). Image recognition processing, (in the figure, are collectively referred to as "workpiece image data") captured image data of the center electrode W ₁ or the ground electrode W ₂ takes in, storage device master image data 125a corresponding thereto 125
(FIG. 11) and read from the memory 11 of the RAM 114.
4b and 114c.

The master image, using a standard product of a spark plug part to be inspected, the opposing portions across the gap g of the ground electrode W ₂ of the center electrode W _1, by pre-photographing under predetermined conditions It was created. And the master image, the electrode edge line of the center electrode W ₁ and the ground electrode W ₂ generates edge line information for identifying, based on the images picked up, on the captured image of the points constituting their electrode edge line The coordinates are determined. The generation of such edge line information is described in, for example,
A technique as shown in 0-180310 can be used. Note that the generated edge line information is stored in the image analysis unit 1.
10 are stored in the RAM 114.

Next, the smoothing process (S110: FIG. 13) will be described. First, read the tip edge line E ₂ of the information of the ground electrode W ₂ obtained in the captured image (given as coordinates set of the points of the edge line (pixels)). FIG. 14A shows an example of a captured image, in which some or all of the pixels constituting the edge line are contour line measurement points (center electrode side: a ₀ , a ₁ , a _2. a _m, the ground electrode _{side: b 0,} b _1, a _b 2 ··· b _n). The position coordinate set, as shown in FIG. 14 (b), by plotting a point on the X-Y plane, the ground electrode W ₂
It can represent undulation level profile PF of the tip edge line E ₂ of.

The undulation level profile PF
Is subjected to a smoothing process. Various methods can be considered for the smoothing process. For example, a method of performing a process of calculating a moving average based on the undulation level profile,
A method of performing a function approximation to the undulation level profile by the least square method can be used. That is, in the XY coordinate system, the undulation level profile may be smoothed by moving average on the basis of a plurality of neighboring points on the edge line constituting the undulation level profile, A method of smoothing the undulation level profile in a form that approximates a function by a multiplication method may be used.

The following method may be used. FIG.
As shown in, undulation level section seg ₁ profile PF a plurality of predetermined _lengths, seg _2, · ·, divided into seg _m, performed as a process of averaging the undulation level profile PF on each section seg. For example, in FIG.
_2. Projection BP which seems to be caused by burrs etc. at the time of punching
However, the protrusion BP is adjusted by the averaging process, the protrusion height is reduced, and the influence on the gap interval measurement described later is reduced. The section width is appropriately set in accordance with the size of the projection BP to be generated, for example, in a range that does not become smaller than the width of the projection BP. In this process, the undulation level profile PF is divided into sections each having c data points, and the sum SR of the undulation levels (that is, the value of Y) in the section is calculated for each section. by dividing, calculates the average value Y _m for each section. The data for each Y is replaced by the value of Y _m, corresponding to each section.

Further, as shown in FIG. 16, the undulation level profile PF is divided into a plurality of sections seg ₁ and se of a predetermined length.
g ₂ ,..., seg _n , a change rate F (= ΔY / ΔX) of the undulation level is calculated for each section seg, and a section in which the value of the change rate F does not satisfy a predetermined condition. ,
For example, a range in which the change rate F is defined (for example, the upper limit value Fma
(x, lower limit value Fmin), processing for correcting the undulation level of the edge line in the section may be performed. The correction processing in this case can reduce the influence of the minute projection BP (existing over seg ₃ and seg ₄ in the figure) existing in the section, for example, averaging the undulation level in the section Or a process of changing the value of the undulation level in a direction to reduce the height of the protrusion.

A description will be given below of an example of a process for performing a correction for replacing the undulation level in a section that does not satisfy the condition with the average undulation level of the entire profile PF. In this example, the profile PF is currently focused on the data points
It is divided by the minimum section consisting of the adjacent data points.
First, calculate the average value Y _m of Y, the number of data points of interest currently as i, next to the data points (i.e. i + 1
The second data point), the difference ΔY = Y _{i + 1} −Y _i
Is calculated and divided by the distance ΔX between adjacent data points to calculate a change rate F = ΔY / ΔX. FIG.
As shown in 6, replacing the rate of change F is the upper limit value Fmax, and if it is outside the range between the lower limit value Fmin, the value of Y _i at the value of the average value Y _m (i.e., modify). This is repeated for all i.

Further, as the smoothing processing, a method of removing high frequency components by using Fourier analysis on the undulation level profile can be used. Specifically, FIG.
Considering the profile PF as a waveform curve as shown in
This may be subjected to low-pass filtering. Various known methods can be adopted as the low-pass filter processing. For example, as shown in FIG.
The frequency spectrum of the profile PF is obtained by Fourier-transforming the (XY curve) in the XY coordinate system (L301). In FIG. 17, the protrusion BP can be considered as a high-frequency noise component having a certain frequency or higher.
In L302 of FIG. 17, high frequency components equal to or higher than the cutoff frequency appropriately set according to the projection width are cut from the obtained frequency spectrum. Then, by applying an inverse Fourier transform process to this at L303, a filtered profile (solid line) in which high-frequency components are cut from the original profile (broken line) is obtained as shown in FIG. Is reduced. The low-pass filter processing is performed by software as described above. For example, a digital output of XY data is converted to a D / A converter,
The signal may be taken in through an analog low-pass filter circuit using a / D converter or through a digital low-pass filter circuit.

Next, an example of the gap measurement processing (S120: FIG. 13) will be described. Reading the information it has been smoothed by the smoothing process of the tip edge line E ₂ of the ground electrode W _2, and information also smoothed the tip edge line E ₁ of the center electrode W _1. Then, as shown in FIG.
A ground electrode spark gap forming portion facing the spark gap G ₂ side, in the center-electrode spark gap forming portion of the center electrode W ₁ side, a plurality determine the measurement points of the contour line which gives the position of each outline. As shown in FIG. _{14, a} 0, _{a 1} a measuring point of the contour line of the center electrode side, a 2 · · · expressed as _{a m,} the measurement points of the contour line of the ground electrode side _b 0,
It is represented as b ₁ , b ₂ ... b _n . The spark gap forming portion on the ground electrode side according to the present invention refers to the ground electrode W
Means the center electrode W ₁ and the portion opposite to each other across the spark gap G in _2, the leading edge line E ₂ is a portion of the outline. In the case of having a chip as shown in FIG. 6, the chip surface facing the spark gap G corresponds to this. When the side surface of the ground electrode directly opposes the center electrode, the opposing portion on the side surface of the ground electrode corresponds to the center electrode. The center and the electrode-side spark gap forming portion is a portion (specifically, ground-electrode-side spark gap forming portion) and the ground electrode W ₂ across the spark gap G opposite, outer tip edge line E ₁ This is a portion to be a line (a tip surface portion of the center electrode).

The measurement points on the outline are at the edges.
The selection may be made for each predetermined pixel, and
All the pixels may be set as measurement points on the outline. Soshi
In one spark gap formation part,
One is set as a reference point, and the other spark gap
On the outline where the distance to the reference point is the shortest in the forming part
Find the measurement point and determine the gap interval based on the shortest distance
Will be determined. Note that, in FIG.
One of the measurement points on the extreme side is defined as the reference point and is indicated by the dashed line A.
All the measurements at that reference point and the ground electrode side as
Measurement point (b₀, B ₁, B₂... b_n) And distance
And find the shortest distance (dashed line B)
You. Further, a plurality of points a serving as reference points are determined.
For each of the quasi-points,
Find the shortest distance to the measurement point on the outline. In particular,
References all measurement points on the outline of the electrode on the reference point side
Points, and measure all the reference points on the other outline.
The distance from a fixed point can be obtained. And those
The gap interval based on the minimum of the shortest distances
decide. Thereby, the XY plane direction in the image coordinate system
The workpiece is inclined in the
The gap interval can be calculated. That is, parallel to the central axis
In the direction of the plane which is a plane and is orthogonal to the width direction of the ground electrode
Even if the work is tilted, measurement can be performed without causing an error.
Note that, in the present embodiment, further
The apparent dimensions on the image of the gap
The processing for correcting the step size g ') is performed. This apparent gap
The reference point serving as the base point of the step size g 'is P ₇And

Next, the correction processing (S130: FIG. 13)
Will be described. In this correction process, the slope (specifically in the direction of photographing by photographing means (photographing camera 4), a width direction parallel to the plane of the ground electrode W _2,
And the inclination in the direction of a plane parallel to the axial direction of the center electrode). Specifically, using the apparent gap dimension g ′, an apparent dimension (measurement reference section apparent dimension) of a predetermined measurement reference section on a photographed image of a part of the spark plug and a known measurement reference section are measured. The apparent gap size g 'is corrected based on the standard size (measurement reference portion standard size). In this correction, the dimensional error of the apparent gap size based on the image taken in such a manner that the axis of the center electrode is inclined (specifically, in the direction in which the spark plug is photographed by the photographing means (photographing camera 4)) The dimensional error caused by the image taken in an inclined manner is corrected based on the apparent dimensions of the measurement reference portion and the standard dimensions of the measurement reference portion.

It should be noted, employ a ground electrode W ₂ as a metric unit in the present embodiment, as the measurement reference portion standard dimension,
A known standard thickness t of the ground electrode (hereinafter, also referred to as ground electrode thickness standard dimension t) is determined in advance. On the other hand, as an apparent dimension of the measurement reference portion, a thickness dimension t ′ of the ground electrode on the captured image (hereinafter, also referred to as an apparent thickness t ′ of the ground electrode) is obtained. Then, the apparent gap size g 'is corrected based on the ground electrode thickness apparent size t' and the ground electrode thickness standard size t, and the known standard width w predetermined in the ground electrode. In this embodiment, the known diameter d of the center electrode is used as a correction parameter in addition to t, t ', and w, and the apparent gap dimension g' is corrected based on at least the four parameters. I have. In addition, predetermined known dimensions (dimensions t, w,
For example, d) may be obtained by measuring the actual dimensions of each of the reference products in advance using a length measuring means such as a micrometer. Hereinafter, a specific correction expression will be described. As a premise of the correction expression, the following expression can be adopted based on a geometrical relationship as shown in FIG. Note that FIG. 8 shows a state where the axis of the center electrode is inclined by θ in the photographing direction, and g is the gap interval to be obtained. The direction of shooting from the shooting means is indicated by an arrow A.
In the captured image, the points P ₁ and P ₂ are the edges of the ground electrode, and the point P ₃ is the edge of the center electrode (specifically, the base point P ₇ of the apparent gap dimension g ′ (see FIG. 7). ) Is detected as an edge.

[0039]

(Equation 1)

Further, the above equations are solved simultaneously and solved for g, and the following equation can be adopted as a correction equation.

[0041]

(Equation 2)

In this embodiment, the above parameters
Of the measurement position of the apparent gap dimension g '
Electrode W₁Distance k from the axis O as a parameter
You. Specifically, for example, as shown in FIG.
Ends P of the outline of the spark gap forming part₅, P₆To
Based on these outlines, both ends P₅, P₆
Center point P of₀And the center point P₀And apparently
Reference point P, which is the base point of₇Let k be the distance to
be able to. D 'is the center electrode W₁The axis O of
Axis at a distance k in the radial direction of the axis
O and ground electrode W ₂Parallel to the width direction of the spark plug
Center electrode in that section
Meaning of the distance between both ends on the outline of the side spark gap formation part
And based on the distance k and the known diameter d of the center electrode,
It is a value determined by the formula. Note that the diameter of the center electrode is small.
If the center electrode tip is not flat,
In this case, the diameter d of the center electrode can be regarded as 0.
Therefore, d 'at a position separated by a distance k is regarded as 0, and
You may make it correct. For example, d '=
The correction value can be obtained by substituting 0. And
Based on the apparent gap size g 'being corrected,
Determine the finally obtained correction value g as the gap interval dimension
Then, based on the gap spacing dimension g,
An example of a gap adjusting step is performed to perform spark gap G
It is necessary to adjust the gap. The gap adjustment process is
As shown in FIG.
Ground electrode W of workpiece W positioned in₂For
The drive unit (not shown) such as a screw shaft mechanism
The same bending punch 90 provided detachably provides the same
As shown in (b), provisional bending is performed so that the tip faces diagonally upward.
Ground electrode W₂And the tip is the center electrode W₁Tip face of
The main bending process is performed so as to be substantially parallel to.

This main bending is performed while monitoring the gap interval by the photographing camera 4 in the photographing process as described above, and based on the obtained image information (gap interval dimension g), a spark discharge of a desired size is performed. A gap is formed. The pressing punch 54 is provided with a load cell at the tip, and after the contact with the outer electrode is detected, the pressing punch 54 processes the displacement amount instructed by the image device for performing dimension measurement and the like. Various examples of the method of performing the gap adjustment based on the image information obtained by photographing can be considered variously. For example, an adjustment method of adjusting the gap interval stepwise as shown in JP-A-2000-164322 is considered. Etc. may be used.

Note that the post-processing step is not limited to the gap adjusting step, and a defect management step for managing defects based on the obtained gap interval dimension g may be used.
The defect management step may employ, for example, a defective product removing step of removing the photographing target product as a defective product when the obtained gap interval dimension g does not satisfy the standard as a normal product. In this way, the step of removing the defective product is performed after the edge state is clarified, so that the mistake in discriminating the normal product from the defective product regarding the shape is extremely reduced. Further, a product data generating step of generating product data of a product to be photographed based on the gap interval dimension g may be used. In the product data generation step, for example, when information that the imaging target product is defective is obtained based on the gap interval dimension g, information on the defect in the imaging target product (information on the presence or absence of a defect, It is possible to adopt a method of storing the information in the database in association with the product basic information (data such as the product number, the inspection date, the lot number, etc.) on the product to be photographed. This makes it possible to perform statistical management after accurately distinguishing a normal product from a defective product.

The description of the above embodiment, after to generate edge line information of the center electrode W ₁ and the ground electrode W ₂ on the basis of the photographic image, the gap spacing defining a reference point on the generated edge line It is a method of measuring. By determining the reference point on the edge line in this manner, the shortest distance between gaps can be obtained more directly and with higher accuracy.
However, it is not always necessary to set the reference point on the edge line. Further, the gap interval may be measured without generating edge line information. The method will be described below. Similar to the embodiments described above, photographing the spark gap formed by the center electrode W ₁ and the ground electrode W ₂ by the imaging camera 4 disposed on the opposite side of the lighting device 200 across the spark plug tip. The photographing camera 4 is shown in FIG.
The spark gap g of the workpiece W at a predetermined ratio as shown, the center electrode W ₁ facing the spark gap g and overall leading edge E _1, likewise of the ground electrode W ₂ of the distal end surface of the leading edge E ₂ among them, facing the spark gap portion, and opposite side edges E to the side facing the spark gap of the ground electrode W _2
3 is included. The photographed image photographed by the photographing camera 4 is a grayscale image formed by a combination of output states of a plurality of pixels capable of outputting an intermediate density. Then, the center electrode W ₁ and the ground electrode W ₂ gray tone image face each other across a spark gap to be photographed by the photographing camera 4 is temporarily binarized using a predetermined density threshold, the central black area illustrates the electrode W ₁ and the ground electrode W _2, white area will indicate the space.

Next, as shown in FIG. 19 (a), defined a point a reference point Q ₀ in a predetermined position on a straight line A which crosses the center electrode W _1, a plurality of measurement lines passing through the reference point Q ₀ L ₀ , L ₁ ...
Set L _n radially. The predetermined position is determined in a range of the black area indicates the center electrode W _1. Each of these measurement lines lines L _0, the L ₁ ··· L _n, 19 (b), the plurality of reference points at intervals of one pixel width from the reference point Q ₀ c _0,
c ₁ ... _cm are set. Then, each reference point c ₀ ,
The density value at c ₁ ... _cm is read. next,
A density array as shown in FIG. 19C is created for each measurement line, and binarized using a predetermined density threshold. By multiplying the width of one pixel by the number of reference points determined to be a white area, the space interval of each measurement line is measured. Based on the shortest interval among the space intervals, this reference is used. to determine the temporary gap interval g ₀ with respect to the point Q _0. Similarly, a straight line A
A plurality of values are determined above, and a value that is the shortest distance among a plurality of temporary gap intervals is defined as a gap interval g. In this embodiment, the straight line A is the previously defined locations across the center electrode W _1, may be defined in a space portion to be a spark gap. In this case, the reference point Q ₀ and the center electrode W ₁ and the ground electrode W ₂ is preferably set in a range directly opposite.

The embodiment of the present invention has been described above.
The present invention is not limited to this, and is not limited to the language described in each claim unless departing from the scope described in each claim, and extends to a range that can be easily replaced by those skilled in the art, and It is possible to appropriately add improvements based on the knowledge that those skilled in the art normally have. For example, in the above-described embodiment, the shortest distance is set as the gap interval, but the measured value may show an abnormal value due to various factors. In such a case, a value excluding the abnormal value may be used as the gap distance as the shortest distance. Further, the gap dimension of the entire portion facing the spark gap may be adjusted to be within a predetermined range by referring to the value indicating the maximum among the shortest distances corresponding to the plurality of reference points.

[Brief description of the drawings]

FIG. 1 is a plan view and a side view schematically showing an embodiment of a spark plug manufacturing apparatus according to the present invention.

FIG. 2 is an explanatory diagram of a transfer mechanism.

FIG. 3 is an explanatory view showing the operation concept of a tip surface position measuring device and a temporary bending device.

FIG. 4 is a front view showing an example of the present bending device.

FIG. 5 is a process explanatory view conceptually showing an example of a photographing process.

FIG. 6 is a diagram illustrating an example of a captured image.

FIG. 7 is an explanatory diagram illustrating an example of a method of measuring a gap interval.

FIG. 8 is an explanatory diagram illustrating an example of a correction method.

FIG. 9 is a process explanatory view conceptually showing an example of a gap adjusting process.

FIG. 10 is a block diagram showing an electrical configuration example of a spark plug manufacturing apparatus according to the present invention.

FIG. 11 is a block diagram showing an example of an electrical configuration of an image analysis unit of the photographing / analysis unit.

FIG. 12 is a flowchart showing a main processing flow of the manufacturing apparatus of FIG. 1;

FIG. 13 is a flowchart illustrating an example of the flow of gap shooting / analysis processing.

FIG. 14 shows the profile of the edge shape of the ground electrode as X-
FIG. 4 is an explanatory diagram showing an example represented on a Y plane.

FIG. 15 is a diagram illustrating a concept of an example of a smoothing process;

FIG. 16 is a view showing the concept of another example different from FIG. 15;

FIG. 17 is a flowchart illustrating an example of a process of smoothing an undulating profile using a low-pass filter process.

FIG. 18 is an explanatory diagram illustrating the concept of the smoothing process in FIG. 17;

FIG. 19 is an explanatory diagram illustrating another example of a method of measuring a gap interval.

FIG. 20 is an explanatory view conceptually showing conventional gap measurement.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Spark plug manufacturing device W Work (spark plug) W ₁ Center electrode W ₂ Ground electrode W ₃ Metal shell G Spark gap g Spark gap size g 'Apparent gap size t Ground electrode thickness standard size t' Ground electrode thickness apparent size w Standard width 4 Shooting camera (Shooting means) 5 Bending mechanism (Gap adjusting means) 112 CPU (Post-processing means, Gap interval calculating means, Gap size correcting means, Apparent gap size calculating means, Electrode edge line determining means, Smoothing Processing means)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA02 AA03 AA06 AA22 AA24 AA51 CC00 FF04 JJ03 JJ26 LL26 PP15 QQ16 QQ18 QQ24 QQ31 QQ33 RR08 TT01 TT03 5G059 AA10 CC02

Claims (11)

[Claims] 1. A center electrode disposed in an insulator, a metal shell disposed on an outer periphery of the insulator, and one end thereof is coupled to a front end surface of the metal shell, while the other end is laterally arranged. A method for manufacturing a spark plug, comprising: a ground electrode that forms a spark gap between the bent electrode and a side surface thereof facing the tip surface of the center electrode to form a spark gap with the tip surface of the center electrode. A photographing step of photographing a spark gap, a reference point is determined at one place based on image information obtained by the photographing, and the spark on the ground electrode side determined by a plurality of measurement lines passing through the reference point. A gap interval that determines the gap interval based on a distance between a ground electrode-side spark gap forming portion facing the gap and a center electrode-side spark gap forming portion facing the spark gap on the center electrode side. Out process and method for producing a spark plug which comprises a post-processing step of performing a predetermined post on the basis of the calculated gap distance. 2. The spark plug according to claim 1, wherein the gap interval calculating step determines a plurality of the reference points and determines the gap interval based on the distance obtained for each of the reference points. Method. 3. A central electrode disposed in an insulator, a metal shell disposed on an outer periphery of the insulator, and one end is coupled to a front end surface of the metal shell, while the other end is laterally connected. A method for manufacturing a spark plug, comprising: a ground electrode that forms a spark gap between the bent electrode and a side surface thereof facing the tip surface of the center electrode to form a spark gap with the tip surface of the center electrode. A photographing step of photographing a spark gap; a ground electrode side spark gap forming portion facing the spark gap on the ground electrode side based on image information obtained by the photographing; and a center facing the spark gap on the center electrode side. In one of the spark gap forming portions with the electrode side spark gap forming portion, one reference point on the outline is determined,
Further, in the other spark gap forming portion, find the measurement point on the outline where the distance to the reference point is the shortest,
A method for producing a spark plug, comprising: a gap interval calculating step of determining the gap interval based on the shortest distance; and a post-processing step of performing a predetermined post-processing based on the calculated gap interval. 4. The gap interval calculating step determines a plurality of the reference points and obtains, for each of the reference points, the shortest distance from a measurement point on the outline on the side of the other spark gap forming section. The method according to claim 3, wherein the gap interval is determined based on a minimum value among a plurality of shortest distances. 5. The gap interval calculating step includes, based on the shortest distance, an apparent dimension of the gap interval on an image (hereinafter, also referred to as an “apparent gap dimension”).
And an apparent dimension on the photographed image of a predetermined measurement reference portion on a part of the spark plug (hereinafter, also referred to as “measurement reference portion apparent size”), and a known standard size of the measurement reference portion. 2. The apparent gap size is corrected based on the following (hereinafter, also referred to as "measurement reference portion standard size") and calculated as the gap interval.
5. The method for manufacturing a spark plug according to any one of items 4 to 4. 6. A center electrode disposed in an insulator, a metal shell disposed outside the insulator, and one end coupled to a front end surface of the metal shell, while the other end is laterally connected. A method for manufacturing a spark plug, comprising: a ground electrode that forms a spark gap between the bent electrode and a side surface thereof facing the tip surface of the center electrode to form a spark gap with the tip surface of the center electrode. An apparent dimension of the gap interval (hereinafter, also referred to as an apparent gap dimension) is determined based on an image capturing step of capturing a spark gap and image information obtained by the capturing, and is predetermined in a part of the spark plug. Apparent dimension of the measured reference portion on the photographed image (hereinafter, also referred to as “measurement reference portion apparent size”)
A gap interval calculating step of correcting the apparent gap dimension based on a known standard dimension of the measurement reference portion (hereinafter, also referred to as “measurement reference portion standard size”) and calculating the gap interval of the spark gap. And a post-processing step of performing a predetermined post-processing based on the calculated gap interval. 7. The step of calculating the gap interval includes the step of: determining a dimensional error of the apparent gap dimension, which occurs based on the fact that the spark plug is photographed in an inclined manner in a photographing direction by the photographing means, by the measurement reference unit. The method according to claim 5, wherein the correction is performed based on an apparent size and the standard size of the measurement reference portion. 8. The standard reference dimension of the ground electrode (hereinafter referred to as “standard standard thickness of ground electrode”), wherein the standard reference section is the ground electrode.
On the other hand, the apparent dimension of the ground electrode on the photographed image (hereinafter, “apparent dimension of ground electrode thickness”) is defined as the apparent dimension of the measurement reference portion.
And correcting the apparent gap dimension based on the ground electrode thickness apparent dimension and the ground electrode thickness standard dimension, and a known standard width predetermined in the ground electrode. A method for manufacturing a spark plug according to any one of claims 7 to 13. 9. An electrode edge for determining a leading edge line of the ground electrode facing the spark gap and a leading edge line of the center electrode from an image taken in the photographing step. Line determination step, in order to reduce the influence of minute projections such as burrs formed on the tip surface of the ground electrode or the center electrode or both electrodes, the ground electrode or the ground electrode obtained based on the captured image A smoothing process for performing a predetermined smoothing process on the information of the edge lines of the center electrode or both electrodes. Further, the spark gap interval is calculated using the smoothed edge line information. A method for manufacturing a spark plug according to any one of claims 1 to 8. 10. A center electrode disposed in an insulator, a metal shell disposed on an outer periphery of the insulator, and one end is coupled to a front end surface of the metal shell, while the other end is laterally connected. An apparatus for manufacturing a spark plug, comprising: a ground electrode that is bent back so that a side surface thereof faces a tip surface of the center electrode, thereby forming a spark gap between the center electrode and the tip surface thereof. Photographing means for photographing the spark gap; determining a reference point at one position based on image information obtained by the photographing; and further determining the ground electrode side along a plurality of measurement lines passing through the reference point. Between the ground electrode-side spark gap forming portion facing the spark gap and the center electrode-side spark gap forming portion facing the spark gap on the center electrode side. Calculation means and a spark plug manufacturing apparatus characterized by comprising a post-processing means for performing a predetermined post on the basis of the calculated gap distance. 11. A center electrode disposed in an insulator, a metal shell disposed on an outer periphery of the insulator, and one end is coupled to a front end surface of the metal shell, while the other end is laterally connected. An apparatus for manufacturing a spark plug, comprising: a ground electrode that is bent back so that a side surface thereof faces a tip surface of the center electrode, thereby forming a spark gap between the center electrode and the tip surface thereof. A photographing means for photographing the spark gap; a ground electrode-side spark gap forming portion facing the spark gap on the ground electrode side based on image information obtained by the photographing; and a photographing means facing the spark gap on the center electrode side. In one of the spark gap forming portions with the center electrode spark gap forming portion, one reference point on the outline is determined, and further, in the other spark gap forming portion, the distance from the reference point is determined. A gap interval calculation unit that finds a measurement point on the outline that is the shortest and determines the gap interval based on the shortest distance; a post-processing unit that performs a predetermined post-processing based on the calculated gap interval; An apparatus for manufacturing a spark plug, comprising: