Electric lamp or space discharge component or device manufacturi – Process – With testing or adjusting
Reexamination Certificate
2000-01-03
2001-02-27
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With testing or adjusting
C445S007000
Reexamination Certificate
active
06193575
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority of Japanese Patent Application No. H.11-1392 filed on January 6, the content of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for securing a distance of a spark discharge gap of a spark plug, in particular, by means of image data processing based on a plurality of measurement lines.
2. Description of Related Art
A spark plug has generally a center electrode fitted through an insulator into a housing and a ground electrode fixed to the housing. The center electrode partly exposed out of the insulator faces the ground electrode with a predetermined distance of spark discharge gap therebetween.
To secure the predetermined distance of spark discharge gap, a conventional method or apparatus has steps or means of holding the spark plug, reducing the distance of the spark discharge gap by pressing the ground electrode, taking a picture of the spark discharge gap by a CCD camera as image data and processing the image data.
According to the method or apparatus mentioned above, a measurement is generally conducted along a center axis of the center electrode to detect the distance of the spark discharge gap. That is, as shown in
FIG. 5A
, the measurement is conducted along a measurement line J
5
at a center portion (center axis) of the center electrode, in the spark plug in which the insulator J
4
holding the inside center electrode J
3
is assembled and fitted to the housing J
2
holding the outside ground electrode J
1
.
However, when the insulator J
4
is assembled to the housing J
2
, there is a fear that a center axis (a measurement line J
6
) of the insulator J
4
, that is, the center axis of the center electrode J
3
is shifted from a center axis (the measurement line J
5
) of the housing J
2
, as shown in a dotted line of FIG.
5
A. As the camera for taking the picture of the spark discharge gap is positioned with respect to the housing J
2
as a reference position, the position relationship between the camera and the insulator J
4
may be varied, as the case may be. Therefore, the measurement line for detecting the distance of the spark discharge gap is not always on the center axis of the center electrode and, when the center electrode J
3
is slender, may locate outside the center electrode J
3
.
To cope with the problem mentioned above, there is a way that the position of the measurement line is corrected with respect to the center electrode as the reference position. However, only one of the measurement line is not sufficient to secure an accurate distance of the spark discharge gap.
For example, when the center electrode J
3
has a protruding portion J
7
such as a burr at an edge thereof, as shown in
FIG. 5B
, the spark discharge gap is practically on a line through the protruding portion J
7
, on which a minimum distance of the spark discharge gap is formed. However, as the measurement is made along the center axis (measurement line J
5
in
FIG. 5B
) of the center electrode J
3
, the distance between the center portions of the center electrode J
3
and the ground electrode J
1
is incorrectly recognized as the distance of the spark discharge gap. In another words, there is a possibility that, even if an unusual shaped portion such as the burr mentioned above exists partly on the center electrode J
3
, the unusual shaped portion is overlooked.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above mentioned problems, and an object of the present invention is to provide a method or apparatus for adequately securing a predetermined distance of a spark discharge gap of a spark plug by means of an image data processing.
To achieve the above object, the spark plug is held at first and, then, a picture of a portion around the spark discharge gap is taken to obtain image data, while the ground electrode is pressed to reduce the distance of the spark discharge gap. Next, the image data are processed in a manner that a measurement is made on the image data along each of a plurality of measurement lines nearly parallel to each other connecting the center and ground electrodes so as to cover an entire range of a width length of the center electrode in order to detect the distance of the spark discharge gap. Finally, pressing the ground electrode is stopped when the distance of the spark discharge gap reaches a predetermined value.
As the plurality of the measurement lines covering the entire region of the width length of the center electrode are provided, the length of the spark discharge gap can be adequately secured, even if the center electrode is eccentrically positioned and, further, minimum, maximum and average values of the distance of the spark discharge gap ranging over the entire width length of the center electrode may be controlled.
For example, when the center electrode has a burr, at which the minimum distance of the spark discharge gap is established, it may be recognized by checking a difference value between the minimum distance and the maximum distance that the minimum distance so established is not adequate. As a result, the spark plug having an unusual shape may be detected and eliminated. Therefore, the predetermined distance of the spark discharge gap
13
according to the method or apparatus of the present invention can be more accurately secured, compared with the conventional method or apparatus using only one of the measurement line.
As another aspect of the present invention, the entire width length of the center electrode based on the image data on a reference line passing across the center electrode in a direction of the width thereof is detected. Thus, the width length of the center electrode may be easily detected. Further, it is preferable that the plurality of measurement lines are perpendicular to the reference line to cover the entire range of the width length of the center electrode.
REFERENCES:
patent: 5725405 (1998-03-01), Nakatani
patent: 5741963 (1998-04-01), Nakatani et al.
patent: 8-45645 (1996-02-01), None
patent: 2636814 (1997-04-01), None
Denso Corporation
Pillsbury & Winthrop LLP
Ramsey Kenneth J.
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