JPS595842B2 - Relative position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting the relative position of a detector to an object by bringing a vibrating piece into contact with the object, and particularly to a structure of the vibrating piece.

The inventor has previously proposed a device for detecting the relative position of an object using a vibrating element, and the structure thereof will first be explained 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 this motor shaft 4 includes a center setting vibrating piece 5, a tightening jig 6 fixed to the motor shaft 4, and a vibrating piece 7.
It becomes more. The vibrating piece T resonates in the primary resonance mode shown in FIG. 3 or in the secondary resonance mode shown in FIG. 4 depending on its shape, material, and dimensions. If it gets too close to 8b, it will come into contact with only this object, and if it gets too close to another object 8b, it will come into contact with only this object,
When the two objects are in the center, their relative positions are detected by electrical signals generated by contacting both objects equally, and the center of the shaft of the DC motor relative to the groove surface or its center line, and thus the fixed block 1, is detected. It detects the relative position of the welding torch connected to the The contact of this vibrating piece is electrical circuit 9, 1
0 is electrically detected, and the signal allows the detector, and eventually the welding torch, to follow and guide the groove center line 13 of the base material 8. An object of the present invention is to propose a structure of a long vibrating piece that can be used in a narrow gap in a thick plate using the above-mentioned device.

In short, the present invention is characterized in that the vibrating element has a structure with a small moment of inertia about the fulcrum of the vibrating element, the length of the vibrating element is long, and the vibration mode is also favorable.

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 refers to 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. A state in which vibration is caused by applying excitation energy at the same frequency as . In this state, even a very small amount of excitation energy is converted into vibration energy, so the amplitude increases over time and becomes infinite.

However, in actual equipment, there is energy loss due to air resistance during vibration, deformation distortion of the vibrating element, etc.
As shown in FIG. 9, the normal state is reached at a certain maximum amplitude W, and the vibration continues at the amplitude W thereafter. The resonant frequency F of the cantilevered vibrating element is proportional to the square root of the k value shown below.

l = Length of the vibrating piece (see Figure 7 A and B) When a cantilevered vibrating piece resonates, even if the vibration energy received by the vibrating piece is small, its free end can swing a lot, but it will not reach the resonant frequency. If the frequency deviates even slightly, the amplitude will rapidly approach O.

For example, a device with a resonance amplitude of about 20 m1 becomes only about 211 if it deviates from the resonance frequency. Although the time is extremely short, the transient phenomenon from the start of vibration to the steady state of the maximum amplitude W is as shown in FIG. 9. The center of vibration is now the origin 0, and the position of the vibrating piece at a certain time t1 is −X1 (velocity υ
=0). When the period of vibration is T (Sec), since 1/FO=T, the time 1/FO from time t
2×1/FO, that is, the vibrating element after half a cycle is x1+f(x)
= Comes to position X2. Here, f(x) is the amount of increase in the amplitude of the vibrating piece due to excitation energy, which is converted into vibration energy.

As mentioned above, even if the excitation energy is constant, there is air resistance, etc., so f(x) is a decreasing function. Furthermore, the vibrating element after 1/2F is -X8-1 (X2+f(X2)
] position.

Similarly, the amplitude of the vibrating element reaches the maximum amplitude W while increasing the amplitude of 2f(Xn) by receiving the reciprocating excitation energy as vibration energy per cycle. During resonance, the free end of 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 as shown in Figure 10, there is a position that limits the amplitude. (-x1) is a restriction surface (for example, left groove surface 8a)
When there is a vibration, it vibrates in a resonance-like manner while maintaining the amplitude of W while lightly touching it.

This is due to the following reasons. At the moment when the vibrating piece that was vibrating with the amplitude W hits the limiting surface 8a (see Figures 8 and 10), the energy that the vibrating piece had is consumed as energy pushing the limiting surface 8a, thermal energy, etc. Ru. Then, when the vibrating piece separates from the limiting surface 8a, it receives the excitation energy again and comes to the position of X2=X1+f(X1). In other words, the vibrating piece that was resonating with the amplitude W in a steady state is on the limiting surface 8.
From the moment it hits point a, it enters a transient state until it reaches resonance. 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 can be said to be a vibration similar to a resonance state with amplitude W, =X, +X2. 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 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 a contact that only consumes the excitation energy for one round trip, the contact is almost non-contact.

Regarding the vibrating piece itself, as can be seen from equation (2) above, the resonant frequency F increases as the rigidity of the vibrating piece increases, in other words, the harder the vibrating piece becomes, and as the above binary value (length) decreases. . Next, using FIGS. 8 and 10, a method of detecting the center line between opposing surfaces, for example, a groove, will be specifically explained using an example.

When the free end contacts the left groove surface 8a and resonates as shown in FIG. 8, 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, the fact that it is fixed to the right side groove surface 8b can be taken out as an electrical signal. The fixing point is the center plane of the groove (CL
When the free end 70 returns to the surface), the amplitude of the free end 70 becomes as 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 sent to the fixed point. It can be detected that 4 is always within the center plane of the groove.

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

This contact between the vibrating pieces is electrically detected by electrical circuits 9 and 10, and the signals make it possible to follow the groove center line 13 of the base material 8 with the detector, and hence with the welding torch, and guide it to an upright position. Further, since the vibrating piece vibrates at 50 cycles (or 60 cycles), the welding nozzle or the arc can be easily seen through the vibrating state of the vibrating piece. In the above-described device, the inventor had used a simple rectangular elastic material as a vibrating element before filing this application.

However, in this case, if the length is increased, the moment of inertia relative to the fulcrum becomes large, and the length is naturally limited. The structure of the vibrating element according to the present invention will be explained with reference to the drawings.

FIG. 5 shows a tapered vibrating piece 7a whose width becomes narrower toward the tip of the motor shaft 4, which is a fulcrum. In addition to narrowing the width in a straight line as shown in FIG. 5, it may have a curved edge as shown by a broken line 14 in the same figure. Further, FIG. 6 shows the vibrating element 7b in which a plurality of lightening holes 15 are provided in order to reduce the moment of inertia relative to the motor shaft 4. By implementing this invention, the moment of inertia with respect to the motor shaft, which is the fulcrum, can be made small, a long vibrating piece with a preferable vibration mode can be obtained, and the relative position between the fulcrum and the object can be detected with high precision. This has this effect.

[Brief explanation of the drawing]

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 side view of a tapered τ vibrating piece showing one embodiment of the present invention, FIG. 6 is a side view of a vibrating piece having a plurality of lightening holes showing another embodiment, and FIG. 7A is a side view of the cantilever beam, and Figure 7B is the 7th
Figure AO) I-1 sectional view, Figure 8 is a drawing showing the relationship between the amplitude W1 when there is a limiting surface of the vibrating element, and Figures 9 and 10 are for explaining the operating principle of the device according to the present invention. It is a drawing. 1...Fixed block, 2...DC motor, 4...Motor shaft (fulcrum), 7...
Vibration piece, 15... Lightening hole.

Claims (1)

[Claims] 1. A detection device 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 excited at a resonant frequency. , a detection device that detects the relative position of the vibrating piece and the object based on a signal caused by the free end of the vibrating piece coming into contact with one or both of the two objects; A relative position detection device characterized by having a structure that reduces moment. 2. The relative position detection device according to claim 1, characterized in that the vibrating element has a tapered structure whose width narrows from the fulcrum part toward the tip. 3. The relative position detection device according to claim 1, further comprising a vibrating piece having a plurality of punch holes so as to reduce the moment of inertia about the fulcrum.