JPH08210805A - Contact sensor - Google Patents

Abstract

PURPOSE: To achieve a highly accurate detection regardless of the machining accuracy or contact direction of a sensor itself by vibrating a probe in contact with an object to be sensed. CONSTITUTION: A drive electrode 7 and a detection electrode 8 are laminated to a diaphragm 4 while holding a piezoelectric element 6 between them. A probe 9 is welded onto the diaphragm 4 with stainless wire. When an AC signal is applied to the drive electrode 7, the piezoelectric element 6 vibrates and the vibration is transferred to the probe 9. In this case, an AC signal with a voltage proportional to the level of vibration is generated at the detection electrode 8 due to the piezoelectric effect of the piezoelectric element 6. In this state, when the tip of the probe 9 touches a target, the vibration of the diaphragm 4 can be suppressed. Then, the vibration of the laminated piezoelectric element 6 can also be suppressed, and an AC signal appearing at the detection electrode 8 is also reduced. By processing the level of the AC signal by an electrical circuit, the presence or absence of contact can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact sensor mounted on a coordinate measuring machine or the like for electrically detecting contact with an object to be measured.

[0002]

2. Description of the Related Art Many of the contact sensors that have been generally used conventionally utilize the fact that when the contact of the contact sensor contacts an object to be measured, the contact is tilted or pushed in by an external force. At that time, most of the electrical detection methods are by closing or opening the electrical contacts. As another conventional detecting device, there is a method of detecting with a piezoelectric element which is interlocked with the contactor. A method is also known in which the swing of the iron piece interlocked with the contact is detected by a differential transformer.

[0003]

In the contact sensor, since the contact is detected by displacing the contact element by receiving an external force, it is unavoidable that an error occurs more or less. However, the error is unavoidable in the conventional method. In order to reduce the
There was a problem with the economy. In addition, the error tends to increase when the object is contacted diagonally. The contact sensor according to the present invention enables highly accurate detection regardless of the processing accuracy of the sensor itself or the contact direction.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to vibrating the contactor rather than a passive detection method for detecting displacement of the contactor under external force as in the conventional contact sensor. It has a feature. Mechanically, it is composed of a drive device that applies vibration to the contactor and a detection device that electrically detects the vibration as an AC signal. A solenoid, a motor, a piezoelectric element, or the like may be used as the drive device that applies vibration, and a microphone, a piezoelectric element, a differential transformer, or the like may be used as a device that detects vibration.

[0005]

With the construction of the above means, it is assumed that the driving device constantly oscillates the contact. Further, at this time, it is assumed that the vibration detection device outputs an AC signal that electrically detects vibration. When the contactor comes into contact with the object in this state, the vibration of the contactor is suppressed, and at the same time, the output of the vibration detection device is reduced. By electrically processing this detection output, it is possible to detect the presence or absence of contact as in the conventional case.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described below with reference to the accompanying drawings.
However, the driving device and the detecting device described in the above means are integrated in this embodiment, and one piezoelectric element serves both for driving and detecting. 1 and 2 are cases for protecting the inside, 3 is a pedestal for mounting the diaphragm 4 which is the main part of the sensor, and 5 is a rubber for fixing on the mounting pedestal 3 so as not to disturb the vibration of the diaphragm 4. The mounting base 3 and the fixing member 5, and the fixing member 5 and the diaphragm 4 are bonded to each other. A drive electrode 7 and a detection electrode 8 are attached to the vibration plate 4 with a piezoelectric element 6 interposed therebetween. The contactor 9 is welded onto the vibration plate 4 with a wire made of stainless steel. The vibrating plate 4 also serves as an electrode of the piezoelectric element, 10 is a lead line of the piezoelectric element, 11 is a lead line of the detection electrode, and 12 is a lead line of the drive electrode.

An embodiment of the present invention is constructed as described above, and the principle of contact detection will be described below. Now, when an AC signal is applied to the drive electrode 7, the piezoelectric element 6 vibrates, and the vibration is transmitted to the contactor 9. At that time, due to the piezo effect of the piezoelectric element 6, an AC signal having a voltage proportional to the magnitude of vibration is generated at the detection electrode 8. When the tip of the contactor 9 contacts the object in this state, the vibration of the diaphragm 4 is suppressed. Then, the vibration of the piezoelectric elements bonded together is also suppressed, and the AC signal appearing at the detection electrode 8 also becomes small. The presence or absence of contact is detected by processing the magnitude of this AC detection signal by an electric circuit.

The vibrating frequency is the resonance frequency of the piezoelectric element 6, diaphragm 4 and contact 9. This is because the resonant state has the largest amplitude and the resonant state collapses even with a little resistance, so that higher sensitivity can be achieved.

FIG. 3 shows a block diagram of an electric circuit for driving and detecting by the contact sensor of this embodiment. Thirteen
Is an outlet of a drive signal for vibrating the contact sensor and is connected to 12 in FIG. Reference numeral 14 is an inlet of a detection signal from the contact sensor and is connected to 11 of FIG. Reference numeral 15 denotes a common reference ground line for the drive signal and the detection signal, which is 10 in FIG.
Connected to. After the detection signal is processed by this circuit, 1
It is output as a digital signal indicating the presence or absence of contact with 6.

[0010]

EFFECT OF THE INVENTION By vibrating at a high frequency, highly accurate detection is possible.

Since the contactor need not be rigid, the contactor can be made thin and long.

Since there are no sliding parts, there is no wear and long life,
It is highly reliable.

The accuracy is high even when the object is obliquely contacted.

It is possible to detect even on the side of the contact.

By making the vibration not a single vibration but a product of harmonics or a plurality of vibrations, it is possible to concentrate the sensitivity at the tip of the contactor or increase the lateral sensitivity.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a contact sensor of the present invention.

FIG. 2 is a sectional view taken along the line A-A ′ in FIG.

FIG. 3 is a block diagram of an electric circuit that drives the contact sensor of FIG. 1 and performs signal processing.

[Explanation of symbols]

 1 Lower Case 2 Upper Case 3 Mounting Base 4 Vibration Plate 5 Fixing Member 6 Piezoelectric Element 7 Drive Electrode 8 Detecting Electrode 9 Contactor 10 Common Wire 11 Detecting Wire 12 Drive Wire 13 Drive Output 14 Detecting Input 15 Grounding Wire 16 Output

Claims (1)

[Claims] 1. A contact sensor having a structure having a contact for contacting an object, the contact sensor having a structure in which the contact vibrates by itself.