JPS5921268B2 - Method and device for detecting center between weld groove surfaces - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and a detection device for detecting a center line between groove surfaces by contact between a vibrating element and the groove surfaces.

The inventor has previously proposed a method and device for detecting the groove centerline using a vibrating element.

The present invention is a further improvement of that proposal, and first, the structure of the groove centerline detection device will be briefly explained. In the apparatus for detecting the tracing of the center line between groove surfaces shown in FIGS. 1 and 2, the fixed block 16 is attached to a pedestal (not shown) on which a welding torch (not shown) is attached. A DC motor (referred to as a DC motor) 9 is installed in this fixed block 16.
is attached, and a center setting vibrating piece 13 and a vibrating piece 12 are further attached to a tightening jig 15 fixed to the shaft 11. When the DC motor 9 is connected to the AC power supply 10, it applies vibration to a vibration unit consisting of a vibrating piece 12 and a center setting vibrating piece 13 in accordance with the frequency f. The vibration system has a unique resonance frequency determined by the dimensions and materials of its constituent members, and vibrates the vibrating element in primary and secondary resonance vibration modes or in tertiary and higher resonance vibration modes as shown in FIGS. 3 and 4. In this case, the ends of the vibrating piece 12 and the groove surfaces 18a, 18
b, that is, the end of the vibrating piece is in contact with groove surfaces 18a, 18
The center line 20 between the groove surfaces is detected by electrically detecting by the center detection circuit 8 whether the groove is in contact with both 18a or 18b or only with one of the grooves 18a and 18b. . The purpose of this invention is to propose a vibration mode of a vibrating element based on the results of experiments.

In short, this invention is a proposal that the value of f/f is set to resonance of 0.9 to 1.1 or close to resonance and smaller than 1.1, and that the vibration mode is preferably a secondary mode or higher. It is characterized by:

An embodiment of this invention will be explained with reference to the drawings.

FIG. 6 shows the frequency f of the AC power supply 10 and the resonance frequency F of the primary vibration mode of the vibration system of the detector, with the voltage of the AC power supply 10 kept constant. 5 shows the results of measurement of the relationship between the ratio f/FO and the vibration of the tip of the vibrating element 12 in a free state, that is, 2a shown in FIG. 5.

1, the vibration FO width shown by the solid line was initially maintained, but after once applying the base material groove surface 18a to one side in the same way as in the case shown in FIG.
When the vibration element 8a is moved away from the vibrating element 12, as shown by the broken line in FIG. A hysteresis phenomenon of amplitude returning to the solid line state occurred.

However, in -1, such a biserin FO-s phenomenon was not observed.

Also, the practical amplitude for utilizing f in a state close to resonance is 0.95 degrees F.

l. Obtained when l.

Even if this hysteresis phenomenon occurs, a decrease in the amplitude c on the opposite side occurs as shown in FIG. 5, but this is an indication that the vibration system is not sufficiently stable; In addition, as a result, the detection sensitivity for the deviation between the groove centerline and the vibration centerline was inferior, so setting f1>1 was somewhat undesirable, but FOf It was possible to use it within the range of .1.

Next, as shown in FIG.
When the center line 19 of vibration and the center line 20 between the groove surfaces coincide, the tip of the vibrating piece 12 contacts both groove surfaces 18a and 18b, but the center of vibration If the line 19 and the groove center line 20 are slightly deviated from each other, the above-mentioned amplitude reduction phenomenon occurs at the time of uneven contact, resulting in a state of uneven contact.

Further, when the groove width d is smaller than the amplitude 2a when nothing is restrained from the surroundings as illustrated by the broken line in FIG.
It was found that a similar phenomenon occurs even when the groove width changes.
In FIG. 8, the horizontal axis shows the groove width d, and the vertical axis shows the minimum distance in the direction perpendicular to the groove surface between the center line 19 of vibration and the center line 20 between the groove surfaces when uneven contact occurs. In other words, this is an example of the measurement results obtained by measuring the detection accuracy of the uneven hit state and determining the relationship.The solid line is the result for the next mode shown in Figure 3, and the broken line is for the secondary mode shown in Figure 4. This is the result.

As shown in FIG. 8, this detection accuracy decreases as the degree of restriction imposed on the vibrating element increases (that is, as the groove width d decreases).

The degree of restriction is expressed as the restriction rate (BO-AO)/BO, where the maximum amplitude when the vibrating piece is allowed to freely vibrate is taken as the BO width (groove width) as AO (see Figure 10). .

The frequency of the AC power supply 10 is 60Hz, and the vibrating piece 12 has a length of 55 mm, a thickness of 0.3 mm, and a width of 9 m in the first mode.
In the second-order mode, a spring plate having a length of 130 mm, a thickness of 0.3 mm, and a width of 9 mm was used.

The natural frequency of the vibration system is 60.5Hz1 in the first mode.
In the case of secondary mode, it was adjusted to 60Hz.

By using such a secondary mode or a higher-order mode, it is possible to detect the center with higher precision than in the case of the primary mode.

In particular, when the groove depth is deep and it is necessary to lengthen the vibrating element 12 to detect the center between the groove surfaces, the above-mentioned limiting rate is reduced in the first mode as shown in FIG. 11 (b'o -AO)/
b′o, whereas in the case of the second-order mode, as shown in FIG.
−AO)/b″o, which is clearly smaller when detecting the center between groove surfaces in the secondary mode than in the primary mode, making it possible to increase the detection accuracy.

Depending on the depth of the groove, it is also possible to perform highly accurate detection by using a third or higher order mode.

In addition, when measuring using the secondary mode, it is necessary to provide a fulcrum 21 that lightly touches the vibration nodes so that the vibration nodes are on the center line of the vibration, as shown in FIG. This was effective in preventing the generation of low-order modes or the change in the center line of vibration in the lateral direction during uneven contact.

Specifically, the fulcrum 21 may be held and fixed in a structure shown in a perspective view in FIG. 13, as an example. Here, the resonant frequency of the vibrating element is determined by the number of vibration modes as well as its shape, vibration method, and fixing method (fixed at one end, fixed at both ends, etc.), so it must be calculated in advance. If the manufactured vibrating piece is vibrated at its resonant frequency, for example, a frequency f such that the ratio f/FO = 0.9 to 1.1 with respect to the second-order mode resonance frequency FO, the vibrating piece will be in the second-order mode. It becomes possible to vibrate. By implementing this invention, it becomes possible to detect the center between the weld groove surfaces with high accuracy as shown by the dotted line in FIG.

[Brief explanation of the drawing]

FIG. 1 is a front view of a device for detecting the tracing of the center line between groove surfaces used in carrying out the present invention, FIG. 2 is a side view thereof, and FIG. Figure 4 is a diagram showing the secondary mode, Figure 5 is a diagram showing the contact between the vibrating piece and the groove surface, and Figure 6 is a diagram showing the relationship between the FO and the vibration piece amplitude.
FIG. 7 is a drawing showing the contact of the vibrating piece 12 with the groove surface when the DC motor shaft center 11 and the center line 20 between the groove surfaces are deviated;
Fig. 8 is a drawing showing the relationship between groove width d and detection accuracy, Fig. 9 is a drawing in which a fulcrum device 21 is provided at the node in the secondary mode, and Fig.
Figure 11 is an explanatory diagram of the influence of the relationship between the maximum amplitude and groove width on the limiting rate when the length of the vibrating piece is different, and Figure 12 is an explanation of the limiting rate in the secondary mode. 13 are perspective views showing an example of a specific structure of the fulcrum device 21. FIG. 10...AC power supply, 11...Rotating shaft of DC motor, 12...Vibration piece, 13...
・Vibrating piece for center setting, 15...Tightening jig, 16
... Fixed block, 18 ... Base material, 1
8a, 18b... Groove surface, 19... Center line of vibration, 20... Center line between groove surfaces, 21.
...Fullin device, 2a...Amplitude of the vibrating piece at resonance, B, c...Distance from the center line of vibration to the groove surface.

Claims (1)

[Claims] 1. In a method of detecting the center between opposing weld groove surfaces using a vibrating piece, the ratio f/ of the frequency f of an external force that excites the vibrating piece and the resonant frequency f_0 of the vibrating piece. The value of f_0 is adjusted to a range of 0.9 to 1.1, and the vibrating piece is made to resonate in multiple modes, and the free end of the vibrating piece is brought into contact with the welding groove surface, so that the relative 1. A method for detecting a center between welding groove surfaces that face each other. 2. A vibration imparting device that causes the vibrating piece to resonate in a plurality of modes and at a frequency f in the range of f/f_0=0.9 to 1.1 with respect to the resonant frequency f_0 of the vibrating piece, and an end of the vibrating piece. By electrically detecting whether the vibrating element is in contact with both of the welding groove surfaces or only with one of the groove surfaces, the center of vibration of the vibrating element is located between the groove surfaces. and a fulcrum device that lightly contacts the vibrating piece at or near the vibration node of the vibrating piece that vibrates in the plurality of modes. Front-to-front center detection device.