JPS5836456Y2 - Welding electrode for ultrasonic inspection equipment - Google Patents

Description

[Detailed Description of the Invention] This invention relates to modification of an electrode used to detect the presence or absence of nugget formation in resistance welding and the size of nuggets using ultrasonic waves.

Specifically, during spot welding, the change in the amount of ultrasonic waves transmitted through the weld zone is measured to improve the detection ability of the device that detects the formation of nuggets in the weld zone. This provides an electrode that can be detected with a good noise ratio (S/N ratio).

FIG. 1 is a sectional view of a conventional resistance welding electrode equipped with an ultrasonic vibrator.

In FIG. 1, 1 is a cylinder having a tapered part A for fitting into an electrode holder (not shown), and 2 is a chip embedded in a cavity B formed in the cylinder 1. has a first electrode surface P1 on which the ultrasonic vibrator 3 is attached and a second electrode surface P2 that comes into contact with the object R to be welded.

4 is a damper attached to the first electrode surface P so as to surround the vibrator 3, 5 is a lead wire, and 6 is the cylinder body 1.
Heat from the object to be welded that is transmitted to the electrode surface P2 is absorbed by passing cooling water through a water channel provided inside the electrode surface P2.

Reference numeral 7 designates a pipe for sending water for cooling the water channel 6, 8 a reflective electrode that sandwiches the object to be welded R between the chip 2, and 9 an ultrasonic reflecting surface provided within the reflective electrode.

As described above, the integrated welding electrode has an ultrasonic vibrator 3 bonded to a tip 2, a damper 4 attached thereto, and embedded in a cylindrical body 1.

By the way, the detection ability of conventional electrodes for nuggets is about 3 to 4 mm as shown in Figure 2, and in the case of thin steel plates, nuggets are generally small and cannot detect nugget formation, making it difficult to apply to spot welding inspections of thin plates. It was impossible.

The method of detecting nuggets using this inspection device is to detect changes in the amount of ultrasound transmitted due to changes in the physical composition of the workpiece during nugget formation.In the case of small nuggets, the overall ultrasonic Since the amount of change is small compared to the signal, it cannot be detected sufficiently.

This idea focuses the ultrasonic beam on the nugget-generating area to increase the rate of change in ultrasonic transmission, making it possible to detect even small nuggets.

FIG. 3 shows an embodiment of this invention.

In Fig. 3, 3 is a spherical vibrator, and the first electrode surface P2 of the chip 2 is also a part of the spherical surface having the same curvature as the vibrator, and the vibrator 3 is bonded to the chip 2. .

The ultrasonic waves generated from the vibrator 3 are focused on the object to be welded R, then enter the reflective electrode 8, and are reflected by the reflective surface Q provided in the reflective electrode.

Specifically, the shape of the reflecting surface is such that the focus of the vibrator and the focus of the reflecting surface approximately coincide with each other on the subject so that the incident wave returns along the same path again.

FIG. 4 shows a state in which a conventional electrode is in contact with a subject and an ultrasonic beam is incident thereon.

The conventional beam diameter is about 10 mm when a vibrator with a diameter of DIO mm is used.

FIG. 5 shows the form of an ultrasonic beam incident on a subject according to this invention.

The ultrasonic beam is converged by an acoustic lens, and the beam diameter at its focal point is given by the first equation, as is well known.

λF d Snow QJIX-・-・・・-(1) D/2 For example, if a vibrator with a diameter of lQmm is used and the focal length in the chip is approximately the same as the length of the chip, f=5MHz (ultrasonic frequency) υ= 4700 m/sec (Sound speed inside the chip)D
= 10 mm (diameter of vibrator) F: 25 mm (focal length) Therefore, d'': 3.3 mm.

As mentioned above, the diameter on the object to be inspected can be narrowed down to about 3.3 mm, which is the beam diameter of the conventional electrode, which is the minimum detectable nugget diameter of about 1 mm.

As explained above, according to the present invention, it is possible to provide a high-performance electrode that can detect even a nugget diameter of about 1 mm.

FIG. 6 shows the relationship between the ultrasonic signal and the nugget diameter using the electrode of the present invention (FIG. 3).

Although an integrated electrode in which the chip 3 and the vibrator 2 are attached has been described above, it is clear that an electrode in which the chip 3 and the vibrator 2 can be separated has the same effect.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional welding electrode, Figure 2 is a diagram showing the relationship between the ultrasonic signal and the nugget diameter when a conventional welding electrode is used, and Figure 3 is a focal point of an embodiment of this invention. 4 is a diagram showing the ultrasonic beam in the conventional welding electrode, Figure 5 is a diagram showing the ultrasonic beam in the welding electrode of this invention, and Figure 6 is similar to Figure 3. FIG. 3 is a diagram showing the relationship between the ultrasonic signal and the nugget diameter by the shown welding electrode. 1 is a cylinder, 2 is a chip, 3 is an ultrasonic transducer, 4 is a damper, 5 is a lead wire, 6 is a water channel, 7 is a pipe, 8 is a reflective electrode, Pl is a first electrode surface, P2 is a second Q is the reflecting surface, R is the object to be welded, and D is the diameter of the ultrasonic transducer. In addition, the same reference numerals are given to the middle part of the figure or corresponding parts.

Claims (1)

[Scope of utility model registration request] A main electrode incorporating a chip having a first spherical electrode surface to which a spherical ultrasonic vibrator is attached and a second electrode surface in contact with the object to be welded, and an electrode surface facing the main electrode. A welding electrode for an ultrasonic inspection device, comprising a reflecting electrode having a concave reflecting surface inside which reflects an ultrasonic signal.