JP2000164322A - Manufacture of spark plug and manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spark plug manufacturing device capable of adjusting a gap interval accurately and efficiently even when there is dispersion in the springback(SB) quantity after a bending process by the depression of a ground electrode between individual processed spark plugs. SOLUTION: A first SB quantity u1 generated on the ground electrode W2 of a processed spark plug by test depression is measured, and a second SB quantity u2' generated by the succeeding adjustment depression is estimated based on this value. The second SB quantity u2' is a value peculiar to each processed spark plug. When the adjustment depression is made at the depression quantity added with it, the effect of the difference in the SB quantity is reduced even if the difference in the SB quantity of the ground electrode occurs between individual processed spark plugs, and a gap interval can be reliably adjusted to a target value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a center electrode disposed in an insulator, a metal shell disposed outside the insulator, and one end coupled to a front end face of the metal shell. A spark plug (generally a parallel electrode) having a ground electrode that forms a spark gap between the other end of the center electrode and the center electrode, with the other end bent laterally and the side facing the center electrode tip Type spark plug)
The present invention relates to a manufacturing method and a manufacturing apparatus.

[0002]

2. Description of the Related Art In the manufacture of a parallel electrode type spark plug as described above, formation of a spark gap and adjustment of a gap are performed by the following methods.
For example, it is performed by a method as disclosed in JP-A-3-64882. That is, after pre-pressing the ground electrode, the pressing of the ground electrode is repeated while monitoring the gap interval with a CCD camera or the like until the gap interval reaches a target value. In this case, the target value of the gap interval is set to be smaller than the ideal gap interval by a certain amount in consideration of the springback (elastic return) generated in the ground electrode when the pressing is released.

[0003]

SUMMARY OF THE INVENTION In the above method,
The pressing (bending) process for adjusting the gap interval is performed on the assumption that the springback generated on the ground electrode is always constant. However, in practice, the amount of springback for each spark plug to be processed is not always constant, and in extreme cases, depending on the material composition and history of the ground electrode,
It is no exaggeration to say that all exhibit different springback amounts. If there is a large variation in the amount of springback, when bending is performed assuming that this is constant, deformation proceeds too much and the gap interval becomes too narrow, or conversely, deformation becomes insufficient. Inconveniences such as an excessively large gap interval are liable to occur, and all of them have a problem of leading to a failure.

Here, for example, when the gap interval is larger than the target value, the correction is relatively easy by adding a bending process. However, when the gap interval becomes smaller than the target value, a troublesome correction process such as bending back is performed. Is required. In order to prevent such a situation, it is conceivable to execute the pressing in as few times as possible while monitoring the gap interval frequently, but this greatly reduces the efficiency of the gap adjusting step. become.

According to the present invention, the gap interval can be adjusted accurately and efficiently even if the amount of springback after bending due to the pressing of the ground electrode varies among individual spark plugs to be processed. An object of the present invention is to provide a spark plug manufacturing method and a manufacturing apparatus that can contribute to improving the manufacturing efficiency and yield of spark plugs.

[0006]

The spark plug manufacturing method according to the present invention provides a method for manufacturing the above-mentioned parallel electrode type spark plug, in which the spark plug to be processed is grounded in order to adjust the gap interval of the spark gap. A test pressing step of applying a test pressing to the electrode in a direction approaching the front end surface of the center electrode using a pressing punch, thereby reducing the gap interval of the spark plug to be processed within a range not to be smaller than the target gap interval gt. And, for the ground electrode after the test pressing step, the adjusting pressing step of performing the adjusting pressing necessary for the spark gap to reach the reaching target gap interval gt using a pressing punch, and at the time of performing the test pressing step, The first step is to measure the springback amount (hereinafter referred to as the first SB amount) u1 generated in the ground electrode in the test pressing step. A second SB amount prediction for predicting a springback amount (hereinafter, referred to as a second SB amount) generated on the ground electrode in the SB amount measuring step and the adjusting pressing step based on the measured first SB amount u1. In the adjustment pressing step, the adjustment pressing is performed on the ground electrode by the adjustment pressing amount s2 set in consideration of the predicted second SB amount (hereinafter, referred to as a predicted second SB amount) u2 '. It is characterized by the following.

Similarly, in the spark plug manufacturing apparatus of the present invention, a test press is applied to the ground electrode of the spark plug to be processed in a direction approaching the front end face of the center electrode by using a pressing punch to thereby produce the spark plug. The test pressing means for reducing the gap interval of the spark plug within a range not to be smaller than the target target gap interval gt, and the ground electrode having undergone the test pressing step, the spark gap is reduced to the target target gap interval gt using a pressing punch. An adjusting pressing means for performing an adjusting pressing necessary to reach the position, and a first SB for measuring a springback amount (hereinafter referred to as a result first SB amount) u1 generated in the ground electrode in the test pressing step when the test pressing step is performed. The amount of the springback (hereinafter referred to as the second SB amount) generated on the ground electrode in the adjustment pressing step was measured. And a second SB amount estimating means for estimating the second SB amount based on the value of the first SB amount u1. The adjusting and pressing means anticipates the predicted second SB amount (hereinafter, referred to as an estimated second SB amount) u2 '. An adjusting pressing amount setting means for setting the adjusting pressing amount s2 in a rectangular shape, and a pressing punch driving means for driving the pressing punch by the adjusting pressing amount s2 to perform the adjusting pressing on the ground electrode. .

The above method / apparatus measures the amount of springback (hereinafter abbreviated as SB) of the ground electrode when a predetermined test pressure is applied to the ground electrode of the spark plug to be processed, ie, the first SB amount. It is characterized in that the condition of the adjustment pressing for adjusting to the final gap interval is determined according to the measurement result. That is, the first SB amount u1 generated on the ground electrode due to the test pressing is measured, and the second SB amount u2 'at the time of the subsequent adjustment pressing is predicted from the value. This second S
The B amount u2 'is a value specific to each spark plug to be processed, and the SB amount of the ground electrode is different between the individual spark plugs by performing the adjustment pressing by the pressing amount in consideration of this. However, the influence can be reduced and the gap interval can be reliably adjusted to the target value. Therefore, the deformation of the ground electrode progresses too much, so that the gap interval becomes too narrow, or conversely, the deformation becomes insufficient and the gap interval becomes too wide, so that it is difficult to cause a problem, and thus the production yield of the spark plug is greatly improved. Can be.
In this case, it is sufficiently possible to adjust the gap interval to the final target value with only one test press and one adjustment press, and the efficiency of the gap adjustment step can be improved.

Hereinafter, various requirements which can be added to the method and the apparatus of the present invention, and the functions and effects thereof will be further described. In order to avoid repetition of the description, the method requirements will be mainly described, and the corresponding device requirements will be described in parentheses.

First, in the first SB amount measurement step, the result first SB amount u1 is the gap interval g1 'measured in the state of being pressed by the pressing punch (or information reflecting this).
And the gap interval g measured with the pressure released.
1 (or information reflecting this) can be measured as a difference g1-g1 '(first SB amount measuring means: for example, an image photographing apparatus for photographing an image of a spark gap portion of a spark plug to be processed (for example, CCD camera, etc.) and a gap interval calculator for calculating the gap interval g1 'or g1 from the image). Based on the measured values of the gap interval g1 'in the pressed state and the gap interval g1 in the released state, the first S
The B amount u1 can be accurately calculated. And
The gap interval after the end of the preliminary pressing is g1, and the gap reduction amount necessary to reach the final target value gt of the gap interval is g1-gt, which is the predicted second SB predicted from u1. Taking into account the amount u2 ', the final adjusted pressing amount s2 can be calculated as s2 = (g1-gt) + u2' (adjusting pressing amount calculating step, adjusting pressing amount calculating means).

When the first SB amount is measured, it is sufficient that the difference g1'-g1 of the gap intervals can be grasped, and it may not be necessary to particularly know the values of the individual gap intervals g1 'and g1. . For example, if the position of the center electrode in the gap forming direction can be fixed, the first SB is defined as the difference k1'-k1 between the relative position k1 'of the ground electrode before pressing and the position k1 after pressing. The quantity may be determined. Note that g1 ′ and g1 correspond to k1 ′ and k1, respectively, which determine a reference position on the tip end surface of the center electrode and are measured as distances from the reference position to the opposing surface on the ground electrode side. You can also see.

As a result, in order to accurately predict the second SB amount u2 from the first SB amount u1, it is ideal to apply a test pressing with a constant pressing amount to the ground electrode in the test pressing step. However, for this purpose, a step of measuring the position of the ground electrode before the test pressing is newly required. On the other hand, as long as the amount of bending applied to the ground electrode does not vary extremely, even if the amount of bending caused to the ground electrode by plastic deformation slightly changes, the amount of elastic return (ie, the amount of SB) due to the release of the pressure does not change so much. Rather, it is often almost constant.

In view of the above, with respect to the spark plug to be processed held at a predetermined processing position, a pressing punch provided so as to be able to approach / separate from the ground electrode in the axial direction of the center electrode is fixed in advance to the processing position. By approaching to the ground electrode until the determined test pressing end position,
A test press can be applied to the ground electrode (in the apparatus, it is the above-described press punch driving means that performs this function). In this method / apparatus, the step of measuring the position of the ground electrode before the test pressing is not particularly required, and the pressing is performed by a fixed fixed stroke, so that the preliminary pressing step can be simplified. When the position of the ground electrode before pressing varies, the amount of pre-press applied is not necessarily constant, but the final pressing is performed by measuring the gap interval after pre-press and performing the adjusting press. The influence on the gap interval accuracy can be reduced.

A common pressing punch can be used for the test pressing and the adjustment pressing. As a result, the manufacturing apparatus can be simplified and downsized. In this case, the steps are as follows. First, with the pressing punch held at the test pressing end position, the gap interval g
1 ′ is measured, and then the pressing is released by retracting the pressing punch, the gap interval g1 is measured in that state, and the first SB amount u1 is obtained as g1−g1 ′, and the adjustment pressing is performed using the same. The quantity s2 is calculated as (g1-gt) + u2 '. Next, the pressing punch is moved to the adjustment pressing end position determined according to the calculated adjustment pressing amount s2 to perform the adjustment pressing.

In the apparatus configuration for realizing the above method, the test pressing means and the adjusting pressing means are provided with a common pressing punch and an optional pressing punch capable of approaching / separating from the ground electrode of the spark plug to be processed. And a driving mechanism including a driving means configured to be able to hold the position described above, and the following requirements may be added to this. Test pressing drive control means: The pressing mechanism moves the pressing punch to the test pressing end position to perform preliminary pressing, and then holds the pressing punch at the test pressing end position. g1 'measuring means: Measures the gap interval g1' while the pressing punch is held at the test pressing end position. Retraction drive control means: After the measurement of g1 ', the pressing punch is retracted to release the pressing. g1 measuring means: Measure gap gap g1 in that state Adjusting pressing amount calculating means: Resulting first SB amount u1 to g1-g
1 ′, and using it, the adjustment pressing amount s2 is calculated as (g1−
gt) + u2 '. Adjustment pressing drive control means: Next, the pressing punch is moved to the adjustment pressing end position determined according to the adjustment pressing amount s2 to perform the adjustment pressing. According to this device configuration, the pre-pressing and the adjusting pressing can be continuously performed in a state where the spark plug to be processed is held at the same processing position by the common pressing punch.
Not only is the device compact and simple, but also because there is no movement of the spark plug to be processed between the preliminary pressing and the adjusting pressing, the gap interval measurement or SB amount measurement,
Eventually, the final gap adjustment can be performed with higher accuracy.

Next, if the actually measured first SB amount u1 and the resulting second SB amount u2 are always substantially equal, the predicted second SB amount u2 'is the simplest method. There is a method in which the SB amount u1 is used as it is as u2 '. On the other hand, the value of the result first SB amount u1 and the result second SB amount u2 are not necessarily equal, but if the value of u2 / u1 is always constant, the value is used as the correction constant C and the predicted second SB amount u1 is used as the correction constant C. The SB amount u2 'can be calculated by u2' = u1 · C and used.

However, the value of u2 / u1 may vary depending on the spark plug to be processed (for example, the material of the ground electrode used and the variation between processing lots). In this case, the following method / apparatus is possible. That is, when adjusting the gap interval between a series of a plurality of spark plugs to be processed, the manufacturing method (apparatus) of the present invention described above is applied to the present processing target spark plug by adjusting the amount of springback (hereinafter referred to as “the amount of springback”) generated at the ground electrode during the adjustment pressing. A second SB amount measuring step (result second SB amount measuring means) for measuring u2, and the next processing target based on the value of the measured second SB amount u2. An adjusting pressing amount correcting step (an adjusting pressing amount correcting step) for correcting the adjusting pressing amount of the spark plug is included. As a result, for example, the adjustment pressing amount of the next spark plug to be processed can be more accurately determined in consideration of the value of the second SB amount u2. In the measurement of the result second SB amount u2, the finally adjusted gap interval g2 can be measured, but the measured value is, for example, the final gap size conforms to the specified size condition. It can be used to determine whether or not there is.

In this case, the predicted second SB amount u 2 ′ in the current spark plug is calculated by calculating the resulting second SB amount in one or more processed spark plugs that have been processed prior to the current spark plug. It is determined on the basis of the actual value of u2 (second SB amount predicting means). If the second SB amount u2 is smaller than the predicted second SB amount u2 ', the adjustment pressing amount of the next spark plug to be processed is determined. If u2 is larger than u2 ', the opposite correction can be performed (adjustment pressing amount correcting means).

According to this, the predicted value of the second SB amount in the adjustment pressing process for the current spark plug to be processed is determined based on the actual value of the second SB amount u2 obtained in the preceding one or more spark plugs to be processed. (Predicted second SB amount u2 '), and the SB actually generated in the adjustment pressing process is smaller than the predicted value.
If the amount (result second SB amount u2) is small, a correction is made to reduce the adjustment pressing amount of the next spark plug to be processed, and if it is opposite, a correction is made to increase it. That is, when the actual value of the second SB amount u2 shows a tendency to increase as a result of the already processed spark plug, correction to increase the pressing amount in the subsequent pressing step is performed to reduce the deformation amount. If the actual value shows a tendency to decrease, on the other hand, correction is performed to reduce the pressing amount in the subsequent pressing step, so that excessive deformation hardly occurs. As a result, the accuracy of gap interval adjustment can be further improved, and the risk that the gap interval becomes smaller than the target gap interval gt can be further reduced.

The predicted second SB amount u2 'is the first SB amount u1 actually measured by the preliminary pressing of the current spark plug.
Can be calculated as a value multiplied by a certain correction variable X. For example, as a simple method, the actual value of the value of u2 / u1 of the spark plug processed immediately before (for example, the average value of the values of u2 / u1 of some spark plugs) is used as X, U2 'of spark plug, u2'
= U1.X can also be calculated.

On the other hand, in the preceding spark plug to be processed, a temporary abnormal value may be generated in the second SB amount u2 as a result of a sudden factor. Is alleviated, and the more accurate prediction of the second SB amount becomes possible. That is, when N (N ≧ 2) spark plugs preceding the spark plug to be currently processed are arranged in chronological order of the processing, the correction factor A of each of the spark plugs to be processed is corresponded. A = u2 '/ (u2 + u2') using the predicted second SB amount u2 'to be calculated and the result second SB amount u2, and the A obtained for the N plugs to be processed.
A correction coefficient calculating step (correction coefficient calculation means) for calculating a correction coefficient α as an average value of the values of the spark plugs, and a second prediction for the current spark plug to be processed using the correction coefficient α and the resulting first SB amount u1. The SB amount u2 ′ is calculated as follows: u2 = u1 · α / (1−
α) to determine the predicted second SB amount (predicted second SB
B amount determining means).

The value of A includes only the parameters (u2 ', u2) related to the second SB amount, which is A = (u2' / u1) / (u2 / u1 + u2 '/ u1). With this in mind, it can be seen that the correction coefficient α has the following meaning.
That is, the correction factor A approaches 1/2 when the difference between the result value (u2 / u1) of the second SB amount / first SB amount and the predicted value (u2 '/ u1) becomes small, and the result value becomes the predicted value. The distance approaches 1 when the distance increases, and approaches 0 when the distance decreases. Therefore, the correction coefficient α, which is the average value, is also calculated based on the past results of the spark plug to be processed.
As the number of spark plugs to be processed in which the difference between the result value and the predicted value is small increases, the number approaches 1/2 (pattern 1), and the number of the spark plugs to be processed separated to the side where the result value becomes larger than the predicted value. When the number increases, it approaches 1 (pattern 2), and conversely, when the number of spark plugs separated on the smaller side increases, it approaches 0 (pattern 3).

In this case, the value of α / (1−α) approaches 1 in pattern 1. That is, the predicted value (u2 '/ u1) approaches the result value (u2 / u1). In other words,
The effect of the correction decreases as the difference between the result value and the predicted value decreases. On the other hand, in pattern 2, the value of α / (1−α) increases in inverse proportion to the difference between the predicted value and the result value. As a result, when the adjustment pressing amount s2 is calculated as, for example, (g1-gt) + u2 ', the adjustment pressing amount s2 becomes large, and the problem that the gap interval becomes too wide can be suppressed. In pattern 3, the value of α / (1−α) approaches 0 as the difference between the result value and the predicted value increases. That is, it is possible to suppress the problem that the adjustment pressing amount s2 becomes small and the gap interval becomes too narrow.

[0024]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. 1 (a) and 1 (b) are a plan view and a side 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 includes a linear conveyor as a transport mechanism that intermittently transports 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 performing the spark gap formation of the work W, that is, the work loading mechanism 11 as a spark plug loading 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 performing temporary bending of the ground electrode, a main bending device 15 for performing the main bending, and a work W after 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 to intermittently convey each carrier 302, that is, the work W, along the conveyance path C.

As shown in FIG. 2, the workpiece W is made up of a cylindrical metal shell W3, an insulator W4 fitted inside the metal shell W3 such that the front and rear ends project, and an insulator W4.
And a ground electrode W2 having one end connected to the metallic shell W3 by welding or the like and the other end extending in the axial direction of the center electrode W1.
The ground electrode W2 is bent on the front end side toward the front end surface of the center electrode W1 in the following steps, and a spark gap is formed to form a parallel electrode type spark plug. A cylindrical holder 23 having an open upper end is integrally attached to the upper surface of the carrier 302. The work W is removably inserted into the holder 23 from the rear end side, and the hexagonal portion W6 of the metal shell W3 is supported by the opening peripheral portion of the holder 23, so that the ground electrode W2 side faces upward. Is transported together with the carrier 302 in a state of being set up.

The work carry-in mechanism 11, the work discharge mechanism 16 and the rejected goods discharge mechanism 17 shown in FIG. 1 are set, for example, as shown in FIG. 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 for driving the chuck hand mechanism 36 forward / backward in the radial direction of the circumferential path C by an air cylinder 38 or the like. It consists of. The chuck hand mechanism 36 is driven to be opened and closed by an air cylinder (not shown) or the like.
Then, the workpiece W is moved forward and backward by 8 to move to the transfer destination, where it is lowered again to release the holding of the work W and the transfer is completed. Then, in the case of loading the work, the work W is received by the work supply unit, transferred to the holder 23 of the linear conveyor 300, and mounted thereon. On the other hand, in the case of discharging the work, the work W is extracted from the holder 23, transferred to a work discharge section (for example, a work collection box or a shooter) and discharged.

FIG. 3A shows a ground electrode alignment mechanism 4.
3 is conceptually shown. The ground electrode alignment mechanism 4
Is at a predetermined angle (180 ° 180 in the present embodiment) that can be approached to and separated from the tip end of the work (spark plug) W in the axial direction thereof and is rotated around the axis by a motor 151 or the like.
°) Rotating member 15 provided to be intermittently rotatable in units
0, and a groove 152 having a width and a depth corresponding to the ground electrode W1 of the work W is formed on the bottom surface of the rotating member 150. When the work W is carried into the ground electrode alignment mechanism 4, the rotating member 150 falls to the tip of the work W.
At this time, the direction of the groove 152 of the rotating member 150 is positioned so as to correspond to the alignment position. Since the position of the ground electrode W1 is undefined at the time of being brought into the ground electrode alignment mechanism 4, even if the rotating member 150 falls, in many cases, the groove 152 does not fit with the ground electrode W1, and The member 150 has a bottom surface on the ground electrode W1. Next, the motor 151 operates and the rotating member 15
0 rotates around the axis while sliding on the ground electrode W1 on the bottom surface. The ground electrode W1 has a groove 152 during its rotation.
After that, the work W rotates together with the rotating member 150. Then, the rotation member 150 stops rotating just one rotation from the initial position. As a result, the ground electrode W1 is positioned at a predetermined alignment position. The driving unit of the rotating member 150 may be configured by a rotary actuator using air or hydraulic pressure.

Next, the tip surface position measuring device 13 is for measuring the position of the tip surface of the center electrode W1 prior to temporary bending, which will be described later. As shown in FIG. 115 is provided. The work W is mounted on the linear conveyor 300 and the holder 23 is fixed at the height position.
On the other hand, it is mounted with the ground electrode W2 standing upright. The position detection sensor 115 (for example, composed of a laser displacement sensor or the like) is held at a constant height by the frame 40 for measuring the height position of the distal end surface, so that the center of the loaded work W is adjusted. The position of the tip surface of the electrode W2 is measured from above.

Further, as shown in FIGS. 4 (b) and 4 (c), the temporary bending device 14 makes contact with the front end surface of the center electrode W1 of the work W detected by the position detection sensor 115. 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 temporary bending process is performed by pressing the tip side of the ground electrode W2 against the center electrode W1 from the side opposite to the center electrode W1 using a bending punch 43. The bending punch 43 is driven toward and away from the ground electrode W2 for temporary bending by a punch driving unit such as an air cylinder (not shown). The temporary bending spacer 42 is positioned in such a manner that a predetermined gap d is formed without making contact with the tip end surface of the center electrode W1, and in this state, the grounding electrode W2 is pressed against the spacer 42 by the bending punch 43 to perform a temporary bending process. By performing, defects such as chipping and scratches on the electrode are extremely unlikely to occur,
It is possible to achieve a high yield.

FIG. 5 shows an example of the main bending device 15. This bending device 15 serves both as a test pressing unit and an adjusting pressing unit. The work W 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 work W, on one side of the transport path of the linear conveyor 300, a gap functioning as a main part of a first SB amount measuring unit, a g1 'measuring unit, and a result second SB amount measuring unit, etc. The photographing / analysis unit 3 has bending mechanisms 5 disposed on opposite sides of the linear conveyor 300 with respect to the linear conveyor 300.

The gap photographing / analyzing unit (hereinafter simply referred to as photographing analyzing unit) 3 includes a photographing camera 4 supported on a frame 22 and an analyzing unit 40 connected thereto.
(FIG. 8) are configured as main parts. The photographing camera 4 is configured as, for example, a CCD camera having a two-dimensional CCD sensor as an image detecting unit. As shown in FIG. 17, a work center electrode W2, a ground electrode W1 facing the work center electrode W2, and these center electrodes W2 And a spark gap g formed between the ground electrode W1 and the ground electrode W1.

On the other hand, in FIG. 5, the bending mechanism 5 has a main body case 51 attached to a front end face of a cantilever type frame 51 attached to a base 50 of the apparatus. A movable base 53 is housed in the main body case 5 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 the lower end surface of the main body case 51. . Then, by rotating a screw shaft (for example, a ball screw) 55 screwed into the female screw portion 53a formed on the movable base 53 from above by a pressing punch drive motor 56 in both forward and reverse directions, the pressing punch 54 , And can be held at an arbitrary height 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 bell 57 and the timing pulley 55a.

As shown in FIG. 4C, the pressing punch 54 is moved closer to the ground electrode W2 which is temporarily bent, for example, so that the tip is directed obliquely upward, as shown in FIG. 16C. By pressing this, the main bending process is performed so that the tip of the ground electrode W2 is substantially parallel to the tip of the center electrode W1, and the interval of the spark discharge gap g reaches the target gap interval gt. Is adjusted as follows. The main bending process is performed in two stages of a test pressing process and an adjusting pressing process, the details of which will be described later.

As shown in FIG. 5, the work W is fixed by being sandwiched between the holding members 60 and 61 from both sides in the axial direction when the main bending is performed. In this embodiment, as shown in FIG. 6, the movable holding member 60 is attached to a slider 62, and the slider 62 is driven by a cam 63 via a drive arm 64 in conjunction with a slider 74. The slider 62 slides along the guide 65, and one end of a guide rod 66 that moves integrally with the slider 62 is attached to the rear end face in the advance / retreat direction. The other end of the guide rod 66 extends further rearward through a receiving plate 67 provided at the rear end of the guide 65, and defines a forward limit of the slider 62 at the end. A stopper 69 is provided. The slider 7 is located between the slider 74 and the receiving plate 83.
A spring member 68 for urging the front end 4 in the forward direction is provided.

FIG. 8 is a block diagram showing an example of the electrical configuration of the bending apparatus 15. As shown in FIG. First, the control unit 12 of the bending mechanism 5
0 indicates the I / O port 121 and the CPU 1 connected thereto.
22, a microprocessor 125 including a ROM 123, a RAM 124, and the like.
The control program 123a is stored in M123. The RAM 124 functions as a work area for the CPU 122. The pressing punch drive motor 56 is connected to the I / O port 121 via the servo drive unit 126, and is connected to a pulse generator (PG) 129. Also, the storage device 130 is connected to the I / O port 121.
Is connected. The CPU 122 executes the control program 1
23a, the second SB amount predicting means, the adjustment pressing amount calculating means, the test pressing driving control means, the retreat driving controlling means, the adjusting pressing driving control means, the adjusting pressing amount correcting means, the predicted second SB amount determining means, and the correction coefficient calculation Act as the subject of the means.

As shown in FIG. 10, the storage device 130 stores, for each part number (Y) of the spark plug to be processed, the value of the target gap interval gt to be reached by the adjustment and the SB amount expected at the time of the adjustment pressing described later. A standard SB amount u0, which is a standard value, and a set {A} of correction data (correction factor) for calculating a correction coefficient α described later are stored. The standard SB amount u0 may be fixedly set, or may be updated at any time based on past results and used. On the other hand, as shown in FIG.
04a and a memory for storing various calculated values or measured values to be described later.

Returning to FIG. 8, the imaging / analysis unit 3 has a control unit 40 constituted by a microprocessor comprising an I / O port 41, a CPU 42, a ROM 43, a RAM 44 and the like connected thereto. Stores an analysis program 43a. RAM114
Functions as a work area for the CPU 112. The I / O port 111 is connected to the CCD camera 40 (including a two-dimensional CCD sensor 115 and a sensor controller 116 for converting the sensor output into a two-dimensional digital image input signal).

Hereinafter, an example of the operation sequence of the spark plug manufacturing apparatus 1 will be described. FIG. 11 is a block diagram illustrating an electrical configuration of the main control unit 100 of the spark plug manufacturing apparatus 1 and its periphery. The main control unit 100 controls the I /
O port 101 and CPU 102 connected to it, RO
A main control program 103a is stored in the ROM 103. The microprocessor 103 includes a microprocessor including an M103, a RAM 104, and the like. The drive unit 2c of the linear conveyor 300 (FIG. 1) is connected to the I / O port 101. The drive unit 2c includes a servo drive unit 2a and a conveyor drive motor 2 connected thereto.
4 and a pulse generator 2b for detecting the rotation angle position of the motor 24, and the like. Also, I
The / O port 101 is provided with a part for performing each step of the spark plug manufacturing, that is, a work loading mechanism 11, a ground electrode alignment mechanism 12, a tip surface position measuring device 13, a temporary bending device 14, a main bending device 15, a work discharging mechanism 16, , A rejected product discharging mechanism 17 is connected. The RAM 104 has a CPU
In addition to functioning as a work area 104a of 102, it is used as a storage area for control flags and the like.

Hereinafter, the operation of the manufacturing apparatus 1 will be described. First, FIG. 14 shows a flow of the drive processing program MP1 of the linear conveyor 300 by the main control unit 100 in FIG. In the step M101, a start signal is transmitted to the execution units 11 to 17 of the respective steps in FIG. In response to this, the control programs are started all at once in the respective process execution units (for example, the analysis unit 110 and the control unit 120 in FIGS. 12 and 13). Each of these control programs returns a completion signal to the program MP1 each time the processing ends. On the other hand, the program MP1 receives a process completion flag (FIG.
(Formed in the first RAM 104) (M102 to M113). Then, when all the flags are turned on in M115, the linear conveyor 300 (FIG. 1) is driven by a certain distance necessary for the workpiece W to move to the next process position, and the flags are reset. Hereinafter, returning to M101, the same processing is repeated.

In response to the start signal, the control program in each process execution section is executed in parallel for a plurality of works W held in each process execution position (FIG. 1). Less than,
In order to facilitate understanding, the flow of processing of each program will be described in accordance with the process execution order when focusing on one work W. First, in the process of loading the work W by the work loading mechanism 11, the presence or absence of the work W to be loaded is checked by a sensor (not shown) or the like, and if there is the work W, the work loading mechanism 3 of FIG. Thereby, a new work W is mounted on the work holding unit 23 (FIG. 2). When the operation is completed, a completion signal is transmitted. The loaded work W is carried to the ground electrode alignment mechanism 4 in FIG. 1, and the alignment processing of the ground electrode W2 already described with reference to FIG. 3 is performed. Then, it is further carried to the next position, and the step of measuring the position of the front end surface of the center electrode W1 is executed by the front end surface position measuring device 13. FIG.
As shown in (a), the position of the tip surface is measured by the laser displacement sensor 115, for example, in the form of a height position h as viewed from a predetermined reference position X0. The data of the measured tip surface position is transmitted to the main control unit 100 (FIG. 7).

The measured position of the tip surface is determined by the provisional bending device 14.
(FIG. 1). In response to this, the temporary bending device 14 performs the temporary bending process already described with reference to FIG.
When the temporary bending process is completed, the workpiece W is transferred to the main bending device 15 in FIG. 1, and the main bending process is performed. The flow of the processing by the control unit 120 of the bending apparatus 15 is shown in FIGS.
5 will be described with reference to the flowchart of FIG.

First, at the time of the first actual bending of the spark plug to be processed, the initialization processing shown in FIG. 15 is performed in advance. For example, the initialization signal and the product number Y are input by manual input from an input unit (not shown) or transmission from a higher-level management device.
(M101, M102). And
From the storage device 130 (FIG. 10), a set {A} = A1, A2, ‥‥, AN of the target gap value gt, the standard SB amount u0, and the correction data A corresponding to the product number Y (the number N is preset. Is read out, and the average value thereof is taken to calculate the initial value of the correction coefficient α (M104, M10
5). These gt, u0, {A} and the calculated α are shown in FIG.
Are respectively stored in the corresponding memories in the RAM 124.

Next, in S1 of FIG. 12, a test pressing step is performed. That is, as shown in FIG. 16A, the control unit 120 refers to the rotation speed and the rotation angle position by the pulse signal from the PG 129, and
From the predetermined retreat position h0 set above the ground electrode W2 to the test pressing end position h1 (these are stored in the storage device 130 or the like in FIG. 8 in advance).
The motor 56 is rotationally driven at a predetermined speed via the servo drive unit 126.

When the test pressing end position h1 is reached, the processing of the pressing punch 54 is stopped and held at this position, and then the process proceeds to S2 where a measurement command signal is sent to the photographing / analysis unit 3 (FIG. 8). The gap g1 'in the pressed state is measured. FIG. 17 conceptually shows an example of the gap interval measurement by the analysis unit 40 (FIG. 8) (processing is controlled by the analysis program 43a).
From the images of 1 and the ground electrode W2, the end face of the center electrode W1 is specified, and a straight line passing through a midpoint M of a line segment AB defined by both end positions A and B and orthogonal thereto is set as the center line O. Then, while scanning the measurement straight line L parallel to the center line O in the direction of the line segment AB, the line segment QL connecting the intersection P between L and AB and the intersection Q with the opposite surface of the ground electrode W2 is also detected. Determine the length as the gap interval. In this case, of the gap intervals obtained for each position of the measurement straight line L, for example, the smallest one can be adopted as the measured value of the gap interval. It should be noted that the measured value of g1 'is the value of the control unit 1 shown in FIG.
20 and stored in the corresponding memory of the RAM 124 in FIG. 9 (the same applies to other measured values).

Returning to FIG. 12, when the measurement of g1 'is completed, the process proceeds to S3, and as shown in FIG.
4 is lifted and retracted to a predetermined retracted position, and the pressed state is released. Then, in step S4, the gap g1 in the released state is released.
Is measured. Then, in S5, the result first SB amount u
1 (hereinafter, u1 is also simply referred to as the first SB amount) is calculated as u1 = g1−g1 ′ ‥‥‥ (1).

Subsequently, the process proceeds to S6 in FIG. 12, where the adjustment pressing amount s2 is calculated. FIG. 13 shows the details. First, the correction coefficient α is read from the RAM 124 (FIG. 9) in S61, and then the values of gt, g1, and u1 are read in S62.
Then, in S63, the predicted second SB amount u2 'is calculated and determined by the following equation. u2 ′ = u1 · X ‥‥‥ (2) X = α / (1−α) ‥‥‥ (3) Then, in S64, the stroke for the adjustment pressing, that is, the adjustment pressing end position is calculated by the following equation. The calculation is performed so that the adjustment pressing amount s2 expressed is obtained. s2 = (gt−g1) + u2 ′ ‥‥‥ (4) The adjustment pressing end position is, for example, by considering the first SB amount u1 in relation to the test pressing end position h1 in FIG. , H1 + u1-s2.

Next, the process proceeds to S7 in FIG. 12, and FIG.
As shown in (1), the pressing punch 54 is lowered again to perform the adjustment pressing. The processing at this time is the same as that at the time of the test pressing, except that the pressing end position is set to the calculated adjusted pressing end position. In S8 to S10, the gap intervals g2 'and g2 are measured for the pressed state and the pressed release state shown in FIG. 16D by substantially the same processing as the test pressing, and the second SB is determined in S11. The quantity u2 is calculated as u2 = g2−g2 ′ ‥‥‥ (5).

Next, the routine proceeds to S12, where the correction coefficient is updated. FIG. 14 shows the details. First, S1
At 21 and 122, the predicted second SB amount u2 ′ previously calculated and stored and the actually measured second SB amount u2
Read from AM 124 (FIG. 9). Then, the correction factor for the work is calculated as A = u2 '/ (u2 + u2') ‥‥‥ (5).

Proceeding to S124, the calculated value of A is calculated as shown in FIG.
In the corresponding memory of the RAM 124. here,
This memory is configured as a shift memory, and stores a predetermined number N (for example, about 30) of values of A calculated for the preceding work W in order from the newest one in the time series (see the above description). The initial value of A read in the initialization step (FIG. 15) is to use the data of the last N pieces of A of the same part number Y at the time of the previous processing and use it. Then, the newly calculated value of A is stored in the first area, the previous data is shifted down by the memory shift, and the oldest data is erased. Thus, the contents of the set A {A} are updated, and the correction coefficient α is calculated in S125 as the average value of all the updated A values.

Returning to FIG. 12, in S13, it is determined whether or not the measured value g2 of the gap interval after the adjustment pressing is within the acceptable range. If it is acceptable, the process proceeds to S14, and the work discharging mechanism 16 in FIG. Then, the work W is collected as a passed product. On the other hand, if it is a rejected product, the rejected product discharge mechanism 1
At 7, the work W is collected as a rejected product.

[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 a conceptual diagram showing a ground electrode alignment mechanism together with its operation.

FIG. 4 is an explanatory view showing an operation concept of a tip end surface position measuring device and a preliminary bending device.

FIG. 5 is a front view showing an example of the present bending device.

FIG. 6 is an explanatory view of the operation of the pressing member.

FIG. 7 is a block diagram illustrating an electrical configuration of a main control unit.

FIG. 8 is a block diagram showing an electrical configuration of the present bending device.

FIG. 9 is a memory map showing contents of a RAM of a control unit of the bending apparatus.

FIG. 10 is a memory map showing contents of a storage device of the storage device.

FIG. 11 is a flowchart illustrating a flow of a linear conveyor driving process of a main control unit.

FIG. 12 is a flowchart showing a flow of processing in a main bending step.

FIG. 13 is a flowchart showing the flow of the adjustment pressing amount calculation process.

FIG. 14 is a flowchart showing the flow of a correction coefficient update process.

FIG. 15 is a flowchart illustrating the flow of an initialization process.

FIG. 16 is an explanatory diagram of steps of test pressing and adjustment pressing.

FIG. 17 is an explanatory diagram showing a concept of measuring a gap interval using an image.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Spark plug manufacturing apparatus C Transport route W Work (spark plug to be processed) W1 Center electrode W2 Ground electrode W3 Metal shell g Spark gap 3 Photographing / analysis unit (first SB amount measuring means, g1 ')
Measuring means and result second SB amount measuring means) 5 Bending mechanism 15 Main bending device (test pressing means, adjusting pressing means) 23 Holder 54 Pressing punch 120 Control unit 122 CPU (second SB amount predicting means, adjusting pressing amount calculation) Means, test press drive control means, retraction drive control means, adjustment press drive control means, adjustment press amount correction means, prediction second SB
Amount determining means and correction coefficient calculating means) 300 Linear conveyor (transport mechanism)

Claims (14)

[Claims] 1. A center electrode disposed in an insulator, a metal shell disposed outside the insulator, and one end coupled to a distal end surface of the metal shell, while the other end is directed sideways. A method 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 with the center electrode tip surface. In order to adjust the gap distance of the spark plug to be processed, a test punch is applied to the ground electrode of the spark plug to be processed in a direction approaching the front end face of the center electrode using a pressing punch, thereby reducing the gap distance of the spark plug to be processed. A test pressing step of reducing the distance within a range not to be smaller than the attained target gap interval gt; and, with respect to the ground electrode after the test pressing step, the spark gap is reduced by using a pressing punch. An adjusting pressing step of performing an adjusting pressing necessary to reach the attained target gap interval gt; and an amount of springback generated at the ground electrode in the test pressing step during the test pressing step (hereinafter referred to as a result first SB). The first SB amount u1 is measured by measuring a first SB amount u1 that measures u1) and a springback amount (hereinafter, referred to as a second SB amount) generated in the ground electrode in the adjustment pressing step. SB to predict based on the value of
An amount predicting step, and in the adjusting pressing step, the adjusted pressing amount s2 set in consideration of the predicted second SB amount (hereinafter, referred to as a predicted second SB amount) u2 ' A method for manufacturing a spark plug, comprising performing adjustment pressing. 2. The result first SB amount u1 in the first SB amount measuring step is a gap interval g1 ′ measured in a state where the pressing punch is pressed and a gap interval measured in a state where the pressing is released. The method for manufacturing a spark plug according to claim 1, further comprising an adjustment pressing amount calculation step of measuring the adjustment pressing amount s2 as s2 = (g1-gt) + u2 ', which is measured as a difference g1-g1' from g1. 3. In the test pressing step, for the spark plug to be processed held at a predetermined processing position, the pressing punch provided so as to be able to approach / separate from the ground electrode in the axial direction of the center electrode thereof, The spark plug manufacturing method according to claim 1, wherein the test pressing is performed on the ground electrode by approaching the processing electrode to the ground electrode up to a test pressing end position fixedly determined in advance. . 4. A press punch common to the test press and the adjustment press is used, and the gap interval g1 'is measured with the press punch held at the test press end position. Is released by retracting the pressure, the gap interval g1 is measured in that state, the first SB amount u1 is obtained as g1−g1 ′, and the adjusted pressing amount s2 is used as the value (g1−gt). ) + U2 ', and then presses the pressing punch with the calculated adjustment pressing s
4. The spark plug manufacturing method according to claim 3, wherein the adjustment pressing is performed by moving to an adjustment pressing end position determined according to (2). 5. When adjusting the gap interval between a plurality of spark plugs to be processed, a springback amount (hereinafter referred to as a result second SB) generated at the ground electrode at the time of the adjustment pressing for the current spark plug. Amount)
a second SB amount measuring step of measuring u2, and an adjusting pressing amount correcting step of correcting an adjusting pressing amount for the next spark plug to be processed based on the value of the measured second SB amount u2. The method for manufacturing a spark plug according to claim 1. 6. The predicted second SB amount u2 ′ in a current spark plug to be processed is calculated as the result second SB in one or a plurality of processed spark plugs that have been processed prior to the current spark plug. When the determined second SB amount u2 is smaller than the predicted second SB amount u2 ', a correction is made to reduce the adjustment pressing amount of the next spark plug to be processed. 6. The spark plug manufacturing method according to claim 5, wherein the reverse correction is performed when u2 is larger than u2 '. 7. When N (N ≧ 2) spark plugs preceding a spark plug to be currently processed are arranged in chronological order of processing, a correction factor A of each of the spark plugs to be processed is determined. Using the corresponding predicted second SB amount u2 ′ and the result second SB amount u2 respectively, A =
u2 '/ (u2 + u2'), a correction coefficient calculation step of calculating the correction coefficient α as an average value of the values of A obtained for the N plugs to be processed, and the correction coefficient α and the result Using the first SB amount u1,
The predicted second SB for the current spark plug to be processed
7. The spark plug manufacturing method according to claim 6, further comprising: a step of determining a predicted second SB amount to obtain the amount u2 'by u2' = u1.alpha ./ (1-.alpha.). 8. A center electrode disposed in an insulator, a metal shell disposed outside the insulator, and one end coupled to a distal end surface of the metal shell, while the other end is directed sideways. An apparatus for manufacturing a spark plug, comprising: a ground electrode that is bent back so that a side surface thereof faces a front end surface of the center electrode, thereby forming a spark gap between the center electrode and the front end surface thereof. In order to adjust the gap distance of the spark plug to be processed, a test punch is applied to the ground electrode of the spark plug to be processed in a direction approaching the front end face of the center electrode using a pressing punch, thereby reducing the gap distance of the spark plug to be processed. A test pressing means for decreasing the spark gap by using a pressing punch with respect to the ground electrode after the test pressing step has been completed; An adjusting pressing means for performing an adjusting pressing necessary to reach the attained target gap interval gt; and a springback amount generated in the ground electrode in the test pressing step during the test pressing step (hereinafter referred to as a result first SB). A first SB amount measuring means for measuring u1) and a springback amount (hereinafter, referred to as a second SB amount) generated in the ground electrode in the adjusting and pressing step, the first SB amount u1 being measured. SB to predict based on the value of
Adjustment press amount setting means for setting the adjustment press amount s2 in a manner that anticipates the predicted second SB amount (hereinafter, referred to as a predicted second SB amount) u2 '. And a pressing punch driving means for driving the pressing punch with the adjustment pressing amount s2 to perform adjustment pressing on the ground electrode. 9. The result first SB amount u1 is determined by a gap interval g1 ′ measured in a state of being pressed by the pressing punch.
And the gap interval g measured with the pressure released.
9. The method according to claim 8, further comprising: the first SB amount measuring means for obtaining a difference g1-g1 'from 1; and an adjusting pressing amount calculating means for calculating the adjusting pressing amount s2 as s2 = (g1-gt) + u2'. Spark plug manufacturing equipment. 10. The pressing punch driving means, for a spark plug to be processed held at a predetermined processing position, the pressing punch provided so as to be able to approach / separate from the ground electrode in the axial direction of its center electrode. The method according to claim 8, wherein the test pressing is performed on the ground electrode by approaching the processing electrode to the ground electrode up to a test pressing end position fixedly determined in advance. Spark plug manufacturing equipment. 11. The test pressing means and the adjusting pressing means include a common pressing punch and a driving means configured to be able to approach / separate from the ground electrode of the spark plug to be processed and to hold an arbitrary position. A test in which the pressing mechanism is moved to the test pressing end position to perform the preliminary pressing, and thereafter the pressing punch is held at the test pressing end position. Pressing drive control means, g1 'measuring means for measuring the gap interval g1' in a state where the pressing punch is held at the test pressing end position, and after the g1 'measurement, to release the pressing of the pressing punch. Evacuation drive control means for evacuation, g1 measurement means for measuring the gap interval g1 in that state, the result first SB amount u1 is determined as g1-g1 ', The adjusting pressing amount calculating means for calculating the pressing amount s2 as (g1-gt) + u2 '; and moving the pressing punch to an adjusting pressing end position determined according to the calculated adjusting pressing amount s2. The spark plug manufacturing apparatus according to claim 10, further comprising: an adjustment pressing drive control unit that performs adjustment pressing. 12. When adjusting the gap interval of a series of a plurality of spark plugs to be processed, a springback amount (hereinafter referred to as a second SB result) generated in the ground electrode at the time of the adjustment pressing for the current spark plug to be processed. Second SB amount measuring means for measuring u2), and adjusting pressing amount correcting means for correcting the adjusting pressing amount for the next spark plug to be processed based on the measured value of the second SB amount u2. The spark plug manufacturing apparatus according to any one of claims 8 to 11, comprising: 13. The predicted second SB amount u2 ′ in a current spark plug to be processed is provided.
A predicted second SB amount determining means for determining based on the actual value of the result second SB amount u2 in one or more processed spark plugs processed prior to the current processed spark plug, If the result second SB amount u2 is smaller than the predicted second SB amount u2 ', the adjustment pressing amount correction means performs correction to increase the adjusting pressing amount of the next spark plug to be processed, and u2 13. The spark plug manufacturing apparatus according to claim 12, wherein the reverse correction is performed when is larger than u2 '. 14. When N (N ≧ 2) spark plugs preceding a spark plug to be currently processed are arranged in chronological order of processing, a correction factor A of each of the spark plugs to be processed is determined. Using the corresponding predicted second SB amount u2 ′ and the result second SB amount u2, respectively,
= U2 '/ (u2 + u2'), and a correction coefficient calculating means for calculating a correction coefficient α as an average of the values of A obtained for the N plugs to be processed. Using the first SB amount u1,
The predicted second SB for the current spark plug to be processed
14. The spark plug manufacturing apparatus according to claim 13, further comprising: a predicted second SB amount determining means for determining an amount u2 'by u2' = u1.alpha ./ (1-.alpha.).