JPS5937441B2 - center position detection device - Google Patents

Description

[Detailed description of the invention] The present invention relates to the structure of a center position detection device.

The inventor proposes a device that uses a vibrating piece to detect the center position between two objects. The structure will be explained below with reference to the drawings. A vibration applying device, such as a DC motor 2, which applies vibration to the vibration system, is fixed to a fixed block 1 which is a part of the detector. An alternating current voltage is applied to the direct current motor 2 from an alternating current power source 3, and the motor shaft 4 reciprocates in accordance with the frequency of the alternating current voltage. The vibration system vibrated by the motor shaft 4 includes a center setting vibrating piece 5, a tightening jig 6 fixed to the motor shaft 4, and a vibrating piece T. Depending on its shape, material, and dimensions, the vibrating piece T vibrates in the primary resonance mode shown in Fig. 3 or in the secondary resonance mode shown in Fig. 4.
) The center of the DC motor shaft with respect to the groove surface or its center line, and thus the o. The center position of block 1 and a welding torch connected thereto, for example, with respect to two objects is detected. The contact of this vibrating piece is electrically detected by the electric circuit 9 | 1 port, and the signal causes the detector and the welding torch to follow the center position of the welding torch and the target object, for example, the groove center line 513 of the base material 8, and to induce displacement. This makes it possible to It is an object of the present invention to propose a device that can detect contact at the end of a vibrating element acoustically even if an insulating film is present, instead of the current flow caused by the contact of the vibrating element as described above.

In short, the present invention is characterized in that it is a detection device in which an acoustic element is attached to the base of a vibrating piece, a shaft or fixing block for fixing the vibrating piece, and the sound is converted into an electric signal and extracted.

5 Let us now consider the operating principle of the device according to the present invention.

The vibrating piece that functions as a sensor in this device is cantilevered and in a resonant state. This resonance state is a state in which the vibrating piece vibrates by applying excitation energy at the same frequency as the natural frequency F of the vibrating piece, when an external force that contributes to vibration is applied to the vibrating piece as excitation energy. Say it. In this state, even a very small amount of excitation energy is converted into vibration energy, so the amplitude increases over 5 hours and reaches infinity.

However, in actual equipment, there is a loss of energy due to deformation and distortion of the air resistance vibrating element during vibration.
It becomes a steady state at a certain maximum amplitude W (FIG. 8), and thereafter vibrates at the amplitude W. Resonance frequency F of a cantilevered vibrating piece. is proportional to the square root of the k value shown below. When a cantilevered vibrating piece resonates, even if the vibration energy received by the vibrating piece is small, its free end swings greatly, but if the frequency deviates even slightly from the resonant frequency, the amplitude rapidly approaches 0. .

For example, something with a resonant amplitude of about 2071!11 becomes only about 21 m if it deviates from the resonant frequency. Although it is an extremely short period of time, looking at the transient phenomenon from the start of vibration to the steady state with the maximum amplitude W, we find that
It looks like Figure 10.

Now, assume that the center of vibration is the origin 0, and that the position of the vibrating piece at a certain time t is -X, (velocity v=0).

When the period of vibration is T (Sec), since 1/FO=T, time 1/2×1/FO from time T, that is, the vibrating piece after half a period is X1+f(x1)=X. come into position. Here, f(x) is the amount of increase in the amplitude of the vibrating element due to excitation energy, which is converted into vibration energy. As mentioned above, even if the added energy 5 is constant, there is air resistance, etc., so ``F. X, +f(xl
)) come to the position. Similarly, the amplitude &ζ of the vibrating element receives the reciprocating excitation energy per cycle as vibration energy and increases the amplitude of 2f (XTl) until it reaches the maximum amplitude w. During resonance, the vibrating piece vibrates at the maximum amplitude w due to the balance between the excitation energy received from the motor etc. and the energy loss due to air resistance, etc., but the free end vibrates at the maximum amplitude w, as shown in Figure 7. When there is a limiting surface (for example, the left side groove surface 8a) at the position (-x1), it makes resonance-like vibration while maintaining the amplitude of W1 while lightly contacting this.

This is due to the following reasons. The vibrating piece that was vibrating with amplitude W is 1! At the moment of contact with the silver surface 8&, the energy of the vibrating piece is consumed as energy for pushing the limiting surface 8a, thermal energy, etc. And the vibrating piece is the limiting surface 8
When moving away from a, it receives excitation energy again, and X,=X1
It comes to the +f(X1) position. That is, as a steady state, the amplitude W
The vibrating piece, which was resonating at , shifts to a transient state from the moment it hits the limiting surface 8a until it resonates. However, after one cycle, it hits the limiting surface 8a again, and the excitation energy for one round trip is again consumed as thermal energy, etc., and the same movement is repeated thereafter. This state has the amplitude W,=
It can be said that the vibration is similar to the resonance state of X1+X. In such resonance-like vibrations, the origin 0 does not exist at the center of the amplitude W1 with mathematical accuracy, but moves by the excitation energy (i.e., X2 - X1), and this appears as a measurement error, but the Since the vibration energy itself is extremely small, this error is so small that it can be ignored in measurement.
Further, since the contact between the surface 8a and the vibrating element is such that only the excitation energy for six one round trip is consumed, the contact is almost non-contact.

Next, the method of detecting the groove center line will be specifically explained using an example using FIGS. 7 and 9 for a welding groove. When the free end contacts the left groove surface 8a and resonates as shown in FIG. 7, the other free end position 70' shown does not come into contact with the right groove surface (another object) 8b.

Therefore, it is possible to detect that only the left side groove surface 8a is in contact and extract it as an electrical signal. Similarly, if the fixed point 4 comes too close to the right groove surface 8b, it can be taken out as an electrical signal that it is too close to the right groove surface. The fixing point is the center plane of the groove (CL (1)
When it returns to , the amplitude of the free end 70 becomes large as w because it resonates, and it contacts both groove surfaces 8a and 8b alternately at the resonant frequency, and this is taken out as an electric signal and the fixed point 4 is It can always be detected that it is within the center plane of the groove.

This is summarized in Table 1. By utilizing the characteristics of such a resonant vibrating piece, this vibrating piece is used as a sensor to determine the relative position of the center of the shaft of the DC motor with respect to the center line of the groove surface, and thus of the stationary block 1 and the welding torch connected to it. This is to detect.

The contact of this vibrating piece is electrically detected by electric circuits 9 and 10, and the signal G allows the detector and eventually the welding torch to follow the groove center line 13 of the base material 8 and guide it to a standing position. It is. Further, since the vibrating piece vibrates at 50 cycles α and 60 cycles, the welding nozzle or the arc can be easily seen through the vibrating state of the vibrating piece. The detector according to the present invention will be explained with reference to the drawings.
The structure of the detector is similar to that shown in FIGS. 1 and 2.

As shown in FIG. 5, instead of the lead wires 9 and 10, an acoustic detection element 14 that detects sound using a piezo effect is attached to the vibrating piece near the base of the vibrating piece 7 or the motor shaft 4, and the end of the vibrating piece is open. Whether only one side or both sides of the tip are in contact is detected as an electric signal from the acoustic detection element 14 by a lead wire 15 and the current waveform. In this case, an oscilloscope can be used effectively. When the vibrating piece contacts only one surface (meaning that the fulcrum, that is, the motor shaft center is offset from the groove center).

) The number of contact sounds per unit time is 1/2 of the number of contact sounds per unit time when the vibrating piece is in contact with both sides, so it is easy to convert electric signals and sounds into electricity. It is possible to interpret this as a signal and detect the difference. This can also be easily displayed on the cathode ray tube of an oscilloscope. Furthermore, if it is not desirable to attach an acoustic element to the vibrating piece, it may be attached to the DC motor shaft 4 or the fixed block 1. However, the farther from the contact point of the vibrating piece, the more careful attention must be paid to attenuating the sound. With the recent miniaturization of acoustic detectors, this invention is capable of effectively capturing the contact sound at the end of the vibrating piece, and although the device requires additional auxiliary equipment, it is easy to destroy. Even if the object has an insulating film that cannot be detected, the sensor uses contact sound as a signal, making it an extremely effective and highly accurate detector as there is no need to use the current generated by contact. This has this effect.

[Brief explanation of drawings]

FIG. 1 is a front view of the detector, FIG. 2 is a side view thereof, FIG. 3 is a drawing showing the first resonance mode vibration of the vibrating element, and FIG. 4 is a drawing showing the second resonance mode vibration of the vibrating element. Fig. 5 is a diagram showing a vibrating piece to which an acoustic element according to the present invention is attached, Fig. 6 is an explanatory diagram of the symbols of the cantilever beams used in equations (1) and (2), and Fig. 7 is a diagram showing the opposite FIGS. 8 and 9 are explanatory diagrams of the present invention for detecting the center between surfaces, and are explanatory diagrams of the principle of operation of the present invention. 1...Fixed block, 2...DC motor, 4...Motor shaft, 7...Vibration piece,
14...Acoustic element.

Claims (1)

[Claims] 1. A detector equipped with a vibrating piece whose maximum resonance amplitude is larger than the distance between opposing objects is placed between two objects, and the vibrating piece is set at the resonant frequency of the vibrating piece. By applying vibration and detecting that the free end of the vibrating piece is in contact with either or both of the two objects, it is possible to determine whether the fulcrum of the vibrating piece is at the center between the two objects. A center position detection device configured to detect whether or not the center position is detected. 2. The detector is provided with an acoustic detection element that detects contact between the free end of the vibrating piece and the object, and a signal from the element causes the fulcrum to be located at the center between the two objects. The center position detecting device according to claim 1, which detects whether or not there is a center position detecting device.