JPH0364882A - Spark gap forming device for spark plug - Google Patents

Abstract

PURPOSE:To eliminate the generation of undesirable deformation and a cave-in of both electrodes and eliminate the dispersion of the discharge characteristic and a failure by detecting the spark gap optically and while pushing the outer surface of an earth electrode to compress an electrode interval till the predetermined target value. CONSTITUTION:Earth electrode pushing parts 13, 14 of an electrode interval compressing means 1 push the outer surface of an earth electrode of a spark plug 9 to compress an electrode interval. Interval image pickup means 2, 3 pickups the electrode interval, and a spark gap detecting means 4 detects the minimum electrode interval (spark gap) with the video signal, and an electrode push control means 5 drives the earth electrode pushing parts 13, 14 till the spark gap reaches the predetermined target value, and when the spark gap reaches the predetermined target value, the electrode push control means 6 stops the push of the earth electrode pushing parts 13, 14. The spark gap is thereby formed without a contact to the discharge side surface of both the electrodes, and a spark plug 9 in which unnecessary deformation of both the electrodes and dispersion of the spark gap are hard to be generated can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spark gap creation device for a spark plug.

[Prior Art] A conventional spark gap generating device for a spark plug includes a holder 6, a reference plate 7, and a hammer device 8, as shown in FIG. 5, for example. Then, the spark plug 9 is inserted into the recess (not shown) of the holder 6, and a reference plate 7 of a predetermined thickness is inserted between the center electrode 92 of the spark plug 9 and the ground electrode 93.
the top surface 9 of the ground electrode 93 using the hammer device 8.
A spark gap was created between the two electrodes by giving 1 to 2 blows to 3a.

[Problems to be Solved by the Invention] However, the above-described conventional spark gap creation device for a spark plug has the following problems.

First of all, spark plugs in which the center electrode 92 has a platinum contact have been increasingly used in recent years, but since the platinum contact is soft, the platinum contact may sink into the center electrode 92 body due to a hammer blow, or There were cases where the platinum contacts became deformed.

Second, the spark gap created depends on the gap size before striking by the hammer device 8, the thickness of the reference plate 7, and the striking force of the hammer device 8, and in order to reduce the variation in the spark gap, the striking force of the hammer is However, as a result, depression and deformation of the platinum contact and the center electrode 92 itself becomes a problem.

The present invention has been made in view of these problems, and it is an object of the present invention to provide a spark gap creation device for a spark plug that causes less unnecessary deformation of the picture electrode and less variation in the spark gap.

[Means for Solving the Problems] A spark gap generating device for a spark plug according to the present invention includes a holder for holding a spark plug having a center electrode on the inside and a ground electrode on the outside, and a spark plug held in the holder. electrode spacing compression means having a ground electrode pressing part that compresses the gap between the two electrodes by pressing the outer surface of the ground electrode; gap imaging means for capturing a pupil image of the gap between the two electrodes; and the gap pupil image. spark gap detection means for processing a video signal output from the means to detect a spark gap consisting of a minimum gap between the two electrodes; The present invention is characterized by comprising an electrode pressing control means that performs pressing and stops pressing of the ground electrode pressing section when a predetermined target value is reached.

[Operation] In the spark gap creation device for a spark plug of the present invention,
The ground electrode pressing section of the electrode gap compression means extracts the minimum electrode gap (referred to as a spark gap) from the video signal, and the electrode press control means presses the ground electrode until the spark gap reaches a predetermined target value. and when a predetermined target value is reached, the pressing of the ground electrode pressing portion is stopped.

A spark gap is thus created without contacting the discharge side surfaces of both electrodes.

[Embodiment] An embodiment of the spark gap generating device for a spark plug according to the present invention will be described with reference to FIGS. 1 to 3. FIG.

This spark gap creation device for a spark plug includes an electrode gap compression device 1 that holds and presses the spark plug 9 and constitutes an electrode gap compression means in the present invention, and a spark gap creation device that is disposed on the side of the electrode gap compression device 1 and emits light. Interval imaging means according to the present invention consisting of a device 2 and a CCD camera 3; a spark gap detection means 4 that processes a video signal output from the CCD camera 3 to detect a spark gap of the spark plug 9; and an electrode gap compression device. 1
and an electrode pressing control means 5 for controlling.

The spark plug 9 has a short cylindrical shape, and as shown in FIG.
It consists of a center electrode 92 that protrudes axially outward from the center of one end of the base portion 91, and an L-shaped ground electrode 93 that covers the tip of the center electrode 92.

As shown in FIG. 1, the electrode spacing compression device 1 includes a support plate 11 supported horizontally on a base (not shown), and a holder 12 with an upper end and a bottom, which stands vertically from the upper surface of the support plate 11. , an electric lifting device 13 fixed to a support plate 11, and a head 14 that is driven by the electric lifting device 13 and moves up and down above the holder 12. The electric lifting device 13 and the head 14 constitute a ground electrode pressing section in the present invention.

The support plate 11 is provided with a pair of circumferential guide tubes 11a having guide holes extending vertically through the support plate.

The electric lifting device 13 has a servo motor 15 with a speed reduction device, as shown in FIG. The servo motor 15 is supported by the support plate 11 via a plurality of legs vertically erected from the lower surface of the support plate 11. Further, the servo motor 15 has an output shaft 16 extending in a vertical direction approaching the support plate 11, and the output shaft 16 is provided with a helical groove. A ball screw 17 is screwed onto the output shaft 16, and a drive plate 18 extending in the horizontal direction is fitted and fixed to the ball screw 17. A pair of shafts 19.19 extend from both ends of the drive plate 18 and extend above the support plate 11 through guide tubes 11a, 11a. An elevating plate 20 extending horizontally is fixed to the tip of the shaft 19.19, and a cylindrical head 14 made of hard metal is attached to the lower surface of the central portion of the elevating plate 20, facing the holder 12. has been done.

As shown in FIG. 2, the light projecting device 2 includes a halogen lamp device 21, a light guide 22 made of an optical fiber extending from the halogen lamp device 21, and a milky-white light guide 22 provided close to the tip of the light guide 22. It consists of a light scattering plate 23 made of an acrylic plate, and projects continuous light in a substantially horizontal direction.

As shown in FIG. 2, the CCD camera 3 consists of a TV camera with a built-in CCD area image sensor (not shown), and the optical axis of the CCD camera 3 is approximately the optical axis of the light projected from the light guide 22. is consistent with The silver image screen S of the CCD camera 3, as shown in FIG.
The gap d between the center electrode 92 and the ground electrode 93 is shown in FIG.

The spark gap detection means 4 consists of an image processing device incorporating a general-purpose image processing processor, and processes the video signal output from the CCD camera 3 according to a predetermined algorithm to determine the minimum distance ( That is, the spark gap )[)min is extracted. Since the above algorithm itself is well known, its explanation will be omitted.

The electrode pressing control means 5 is composed of a microcomputer, and drives the electric lifting device 13 until the spark gap Dmin outputted from the spark gap detection means 4 reaches a predetermined target value, and causes the electrode pressing section 14 to press the ground electrode 9. It is a control device that stops driving the electric lifting device 13 and stops pressing the ground electrode 9 by the head 14 when a predetermined target value is reached.

Hereinafter, the operation of this spark plug spark gap creation device will be explained with reference to the flowchart of FIG. 4.

First, the spark plug 9 is inserted into the recess (not shown) of the holder 12 from above by hand or using a handling device. The concave portion of the holder 12 is in contact with two of the hexagonal outer surfaces of the spark plug 9 to maintain the attitude of the spark plug 9.

Pressing the activation button (not shown) starts the routine;
The light projecting device 2 projects light, and the CCD camera 3 uses the picture electrode 92.9.
3. Image the vicinity. In this embodiment, since the transmitted light imaging type is adopted, the picture electrodes 92 and 93 are black, and the picture electrodes 9
The gap d between 2.93 and 2.93 is imaged as white. Then, the spark gap detection means 4 extracts the minimum gap (spark gap) [)min between the picture electrodes 92 and 93, and the extracted [)min is input to the electrode pressing control means 5 (3101).

Next, it is checked whether pmtn is larger than the target gap value Dc set in advance in the electrode pressing control means 5 (310
2>, it is checked whether the absolute value of the difference between Dmin and DC is large (S103). Note that the target gap value DC is the ideal spark gap DO, taking into account springback.
is set a certain amount smaller than .

Then, if the absolute value of the difference between ()min and [)C is large, the head 14 is lowered by a predetermined amount ΔD1 that is less than the above-mentioned absolute value (S104); The head 14 is lowered by ΔD2 (S105
), returns to 3101. Note that ΔD1 is ΔD2
Set it to about 3 times as much.

While repeating the routine, if Dmin becomes equal to or less than the target gap value DC, the process proceeds to 3106, where the head 14 is stopped, then raised, and a routine for inspecting the created spark gap Dmin is entered.

That is, it is checked whether the absolute value of the difference between the created spark gap Dmin and the ideal spark gap Do is larger than a predetermined amount (3107), and if it is smaller, the spark gap is determined to be normal and the spark gap is determined as normal (511).
At 0, an indicator (not shown) indicates OK, the head 14 is raised, and the routine is completed. If larger, D
min>D.

(8108), and if Dmin>[)O, the process returns to 3101 and the electrode spacing is compressed again. If [)min is less than or equal to [)0, the compression is too high and a defect is displayed on an indicator (not shown) 5109), the head 14 is raised (S111), and the routine is ended.

The advantages of the spark gap creation device for a spark plug according to this embodiment will be explained below.

(a) In this embodiment, when the absolute value of the difference between [)min and DC is large, the head 14 is lowered by a large amount, and when it is small, the head 14 is lowered by a small amount, so that work efficiency can be improved. There are advantages.

Note that it is naturally possible to determine the descending speed or amount in proportion to the magnitude of the absolute value of the difference between Dmin and DC.

Further, the gap between the head 14 and the ground electrode 93 is detected in the same manner as described above, and the gap between the head 14 and the ground electrode 93 is detected.
It is also possible to carefully press the ground electrode 93 by lowering the head 14 at high speed until it makes contact with the ground electrode 93, and then lowering it at a lower speed after contact. In this way, work efficiency is improved.

(b) In this embodiment, the spark gap can be inspected after the spark gap generation work using the CCD camera 3 used for spark gap generation, and furthermore, if it is found as a result of the inspection that the spark gap is too large, Since the pressing can be performed again, the product yield can be improved.

In the above embodiment, the electrode gap compression device 1 is of the type having one holder 12, but in some cases, a plurality of holders may be provided to press a plurality of spark plugs at the same time.

Alternatively, a spring may be provided between the head 14 and the elevating plate 20 to adjust the pressing force of the head 14 so as not to become excessive.

[Effects of the Invention] As explained above, the spark gap creation device for a spark plug of the present invention compresses the electrode gap to a predetermined target value by pressing the outer surface of the ground electrode while optically detecting the spark gap. Since it is configured as follows, the following effects can be achieved.

(a> Undesired deformation or depression of the picture electrode does not occur, and there are no variations or defects in discharge characteristics.

(b) Since the electrode spacing is detected optically, the minimum electrode spacing, that is, the spark gap, can be easily detected;
The compression of the electrode spacing can be controlled with high precision based on the detected spark gap.

[Brief explanation of drawings]

FIG. 1 is a schematic front view showing an embodiment of the spark gap generating device for a spark plug according to the present invention, FIG. 2 is a partial schematic sectional view of the device shown in FIG. 1, and FIG. FIG. 4 is a flowchart showing the operation of the electrode pressing control means 5 of FIG. 1, and FIG. 5 is a partial front view of a conventional spark gap generating device for a spark plug. 1... Electrode interval compression device (electrode interval compression means) 2...
・Light projector (interval WL imaging means) 3... CCD camera (electrode interval imaging means) 4... Spark gap detection means 5... Electrode pressing control means 9... Spark plug 12... Holder 13 .14...Ground electrode pressing part Fig. 1

Claims (1)

[Claims] (1) A holder that holds a spark plug that has a center electrode on the inside and a ground electrode on the outside, and compressing the gap between the two electrodes by pressing the outer surface of the ground electrode of the spark plug held in the holder. an electrode gap compression means having a ground electrode pressing part; a gap imaging means for imaging the gap between the two electrodes; and a minimum gap between the two electrodes by processing a video signal output from the gap imaging means. a spark gap detection means for detecting a spark gap; pressing the ground electrode pressing part until the detected spark gap reaches a predetermined target value; and pressing the ground electrode pressing part when the detected spark gap reaches the predetermined target value; A spark gap creation device for a spark plug, comprising: electrode pressing control means for stopping pressing.