JPS6333690A - Detection of object and instrument for same - Google Patents

Abstract

PURPOSE:To recognize the presence of an object in the position of a vibrator by bringing the vibrator wherein a vibration is excited into contact with the object, suppressing the vibration of the vibrator and monitoring changes in a vibrating condition. CONSTITUTION:An oscillator 16 vibrates in accordance with a rectangular wave voltage outputted from an oscillator circuit 56. Thus, a vibration is excited in a vibrator 10 and also in a vibration detector 18. With the movement of a slide 28, a bite 26 is relatively moved with respect to an edge detector 24. When a contact 23 is brought into contact with the bite 26, since the vibration of the vibrator 10 to which the contact 23 is fixedly attached is suppressed, the vibration transmitted to the vibration detector 18 is rapidly reduced. Therefore, an output voltage V outputted from the vibration detector 18 and converted to DC by a waveform shaping circuit 58 is reduced below a threshold voltage. The voltage V is supplied to comparators 60 and 62. The voltage V is compared with the threshold voltage in the comparator 60. Thus, the presence of an object in the position of the vibrator 10 is recognized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a technique for detecting the position of an object with high precision, and in particular to a method of detecting an object by contact and an apparatus suitable for carrying out the method. It is related to.

2. Description of the Related Art A microsinch has been known as an object detector that detects the position of an object through contact. This switch is widely used for automating the operation of industrial machinery.

For example, object detectors are also used in machine tools such as lathes, and the position of the tool cutting edge is automatically corrected based on the detected position of the tool cutting edge. The finishing accuracy of a workpiece depends on whether the relative position of the tool edge to the workpiece is accurately detected and controlled. An earth switch has been known as a detector that can detect the position of a tool cutting edge with high precision. This grounding switch maintains the voltage of the contact at a high level, and when the contact contacts the highly conductive tool cutting edge, the grounding occurs and the voltage goes to low level. It detects the position of the cutting edge with high precision.

However, there are cases where ceramics are used as a substitute for alloy materials in cutting tools, and in that case, the electrical resistance of ceramics is very high, on the order of IMΩ.
A problem arises in that it is not possible to use a grounding switch that utilizes the conductivity of the object. Furthermore, detection using a microswitch cannot be expected to have sufficiently high accuracy.

The present invention has been made to solve this problem by providing a method that can detect the position of an object with high accuracy even if the object has low conductivity, and an apparatus suitable for implementing the method. It is something that

The method for detecting an object according to the first invention vibrates a vibrator and moves the vibrator and the object relative to each other while monitoring the vibration state of the vibrator and detecting the vibration state. The present invention is characterized in that it is determined that an object exists at the position of the vibrator when the value changes by more than a predetermined condition.

Further, the object detection device of the second invention is a device for carrying out the method of the first invention, and includes a main body, a vibrator supported by the main body, and a vibrator fixed to the vibrator. an oscillator that excites vibration, a voltage supply means that supplies an alternating voltage to the oscillator, a vibration detector that converts the vibration of the vibrator into an alternating voltage, and a predetermined output voltage of the vibration detector. Detection signal generation means compares the output voltage with a threshold voltage and generates an object detection signal when the output voltage is less than or equal to the threshold voltage.

When a vibrator whose local vibration is excited comes into contact with an object, the vibration of the vibrator is suppressed and the vibration state changes. Therefore, if the vibration state is monitored, when the vibration state changes beyond a predetermined condition, it means that the vibrator has come into contact with the object, so it is possible to know that there is an object at the position of the vibrator. You can know.

Standing In this way, the object can be detected as long as the vibrator comes into contact with the object, which eliminates the need for the object to be highly conductive, allowing for greater freedom in selecting materials for objects such as tools. can be increased.

Furthermore, the vibration detector sensitively responds to even a slight change in the vibration state of the vibrator and converts the vibration into a corresponding voltage. By utilizing such a phenomenon, highly accurate position detection can be achieved at low manufacturing costs without complicating the device structure.

EMBODIMENT OF THE INVENTION Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

In FIG. 1, reference numeral 10 denotes a vibrator, which is generally made of a single thin plate bent into a U-shape. In the vibrator 10, both arms of a U-shape face each other in parallel with an axis of symmetry in between, and the bottom of the U-shape is a flat part 11 orthogonal to the axis of symmetry.
have. Vibration The tip of both arms of the child 10 is fixed to one end of the main body 12, and vibrates under the condition that both ends are fixed.

A mounting surface 13 perpendicular to the axis of symmetry of the vibrator 10 is formed at the other end of the main body 12, and a male threaded portion 14 protrudes from the center of the mounting surface 13. It is attached to a fixed member fixed to. A flat mounting seat and a female threaded hole are formed in the fixing member, and the male threaded portion 14 is screwed into the female threaded hole, and the mounting surface 13 is brought into close contact with the mounting seat. Further, the main body 12 is hollow with a through hole provided along its central axis.

The oscillator 1 is mounted on the inner surfaces of both arms of the vibrator 100, which face each other.
6 and the vibration detecting body 18 are each fixed using an adhesive. The oscillating body 16 and the vibration detecting body 18 are composed of flat piezoelectric elements. As shown in FIG.
The oscillating body 16 and the vibration detecting body 18 are each fixed in a posture such that their bonded surfaces are parallel to the arms of the camera element 10.

The oscillator 16 converts an input alternating voltage such as a rectangular wave or a sine wave into vibration, while the vibration detector 18
It converts the excited vibrations into alternating voltage. The oscillator 16 and the vibration detector 18 input the alternating voltage.
A cable 22 for output is connected, and the cable 22 is pulled out through the through hole of the main body 12 and connected to an external terminal.

The outer surface of the flat part 11 of the vibrator 10, that is, the main body 12
The contactor 23 is fixed to the surface opposite to the side facing the contactor 23 by adhesive bonding, brazing, or the like. In this embodiment, since the contact 23 makes scheduled contact with the cutting edge, it is made of a cemented carbide metal that is resistant to wear even after repeated contact. The contactor 23 has a rectangular parallelepiped shape, and the four side surfaces parallel to the axis of symmetry and the top and bottom surfaces perpendicular to the axis of symmetry are precisely machined by grinding or the like to obtain high parallelism and perpendicularity. ing.

Said vibrator 109 main body 122 oscillator 16. Vibration detector 1
8 and the contact 23 constitute a cutting edge detector 24, and the cutting edge of the cutting tool 26 comes into contact with this cutting edge detector 24. The cutting tool 26 is attached to a slide 28 of the lathe, and as the slide 28 moves, the ± in FIG.
It comes into contact with the contactor 23 from the X direction or one of the two directions.

What comes into contact with the contactor 23 is the tip of the cutting edge, as shown in FIG. 8, and the part where the straight lines a and b touch each other. The machining dimensions of the workpiece are determined by the positions of these parts. Code 3O is the main shaft of the lathe, code 32
is Chuck.

Next, the control circuit 50 that controls the blade edge detector 24 will be explained based on FIG.

- Reference numeral 52 at the upper left in the figure is a voltage supply means, which is composed of a voltage setting circuit 54 and an oscillation circuit 56. The oscillation circuit 56 has an input terminal and an output terminal connected to the voltage setting circuit and the oscillator 16, respectively, and supplies the oscillator 16 with a rectangular wave voltage having a frequency corresponding to the voltage set by the voltage setting circuit 540.

On the other hand, a waveform shaping circuit 58 is connected to the vibration detector 18, and a comparator 60.
62 are connected. The waveform shaping circuit 58 converts the sine wave voltage from the vibration detector 18 into a DC output voltage (2).

The comparator 60 compares the output voltage V with a predetermined threshold voltage, and generates a high-level knife detection signal when the output voltage V is less than the threshold voltage.
generates a low level signal when the voltage is greater than the threshold voltage. Further, the comparator 62 compares the output voltage ■ with a predetermined reference voltage, and generates a high-level count instruction signal when the output voltage V is lower than the reference voltage, and output voltage ■ is lower than the reference voltage. If the value is greater, low level signals are generated and these signals are output to the counter 66.

The counter 66 has one input terminal connected to the comparator 62 and the other input terminal connected to the frequency dividing circuit 68 . The frequency dividing circuit 68 divides the frequency of the rectangular wave voltage of the oscillation circuit 56 and inputs this signal to the counter 66. The counter 66 counts the number of pulses of the rectangular wave signal from the frequency dividing circuit 68 in accordance with the count instruction signal of the comparator 62,
The count contents in binary notation are output from four output terminals.

These output terminals are connected to a resistor R1 whose resistance value decreases in sequence.
, R2, R, , R4 are connected to each other. The other terminals of the resistors R, , R2, R3, and R4 are connected to the inverting input terminal of the operational amplifier 70 along with one terminal of the resistor R0. In other words, resistance R1J R2,
R3 and R4 are the output terminals of the counter 66 and the operational amplifier 7.
0 and an inverting input field are connected in parallel with each other. Further, the other terminal of the resistor R0 is connected to a high level line.

A non-inverting input terminal of the operational amplifier 70 is grounded via a series-connected resistor and a variable resistor Rv. The output terminal of the operational amplifier 70 is connected to the voltage setting circuit 54, and the voltage setting circuit 54 sets a voltage corresponding to the output voltage of the operational amplifier 70. Furthermore, its output terminal is
It is connected to the inverting input terminal of the operational amplifier 70 itself by a feed pack circuit with a resistor Rf.

Next, with reference to FIGS. 3 to 5, the operation of this device when the contactor 23 is not in contact with the cutting tool 26 (non-contact state) will be described.

The oscillator 16 shown in FIG. 3 vibrates in response to the rectangular wave voltage output by the oscillation circuit 56. As a result, the vibrator 10 is excited to take an image, and the vibration detection body 18 is also excited to vibrate. The amplitude of the contactor 23 at this time is extremely small, for example, 0.11X10-'m to 0.12X10-'m.

The vibration detector 18 converts the excited vibration into a sine wave voltage corresponding to the frequency of the vibration, and converts this into a sine wave voltage corresponding to the frequency of the vibration, which is then applied to the waveform shaping circuit 5.
8 converts it into a DC output voltage ■.

As shown in FIG. 4, this output voltage {circle around (2)} peaks at the resonance frequency f0, and rapidly decreases before and after that.

Similarly, FIG. 4 shows that the temperature of the vibration detector 18 is 0°C, 25°C
The resonance frequency characteristics at ℃ and 45℃ are shown, respectively, and r, which represents the resonance frequency at each temperature,
, r, ; and f♂ decrease sequentially as the temperature increases. This is because the physical properties of the adhesive that adheres the oscillator 16 and the vibration detector 18 to the vibrator 10 tend to change depending on the temperature, and as a result, the rigidity of the vibration system changes. Such fluctuations in the resonant frequency may also be caused by external factors such as humidity.

The output voltage V of the waveform shaping circuit 58 is determined by the comparator 60.6.
2 is input. In the comparator 60, the output voltage ■ is compared with the threshold voltage, and the output voltage ■ is
It almost matches the peak voltage shown in Figure 4,
Further, the output voltage (■) during non-contact is higher than the threshold voltage, as shown in FIG. Therefore, the output voltage of the comparator 60 becomes low level, and no blade edge detection signal is output.

On the other hand, the comparator 62 compares the output voltage V with a reference voltage. This comparator 62 monitors the output voltage (2) in order to prevent a malfunction in which the output voltage (V) falls below the threshold voltage and a cutting edge detection signal is generated even in the non-contact mode. If the voltage V is below the reference voltage, as shown by the two-dot chain line in FIG. 5, it is determined that there is a possibility of a malfunction occurring, and the signal of the comparator 62 changes to high level. This output voltage V is input to the counter 66 as a count instruction signal.

The relationship between the reference voltage, the threshold voltage, the normal output voltage Vn of the vibration detector 18 during non-contact, and the normal output voltage Vt of the vibration sensor 18 during contact is as shown in FIG. is higher than the reference voltage, ■Vt is between the threshold voltage and the reference voltage, and the difference between ■Vn and the threshold voltage is larger than the difference between Vt and the reference voltage. Vn
Since the difference between and Vt is always almost constant, by comparing the output voltage (2) with the reference voltage, it is possible to prevent such malfunctions from occurring.

In response to the count instruction signal, the counter 66 starts counting the number of pulses of the rectangular wave signal input by the frequency dividing circuit 68. As a result, current is supplied to the inverting input terminal of the operational amplifier 70 through any combination of resistors R, , R2, R3, and R4 connected to the output terminal of the counter 66, including zero. In that case, the resistance combinations are (none), (R, ), (R2), (R□, R2),
(R3), ..., (R□, R,, R3),
..., (R,.

There are 16 sets of R2, R3, R4), and each time one pulse is supplied from the frequency dividing circuit 68 to the counter 66, a combination one level higher is selected.

The operational amplifier 70 is supplied via the 16 combinations of resistors and the resistor R0 connected in parallel to them, and the operational amplifier 70 outputs a voltage signal corresponding to this input current to the voltage supply means 52. The range of this voltage signal is the frequency of the rectangular wave voltage supplied from the oscillation circuit 56 to the oscillator 16, while the temperature of the blade edge detector 24 is in the range of 0°C to 45°C. 16 and imaging detection object 1
This is a range in which the resonant frequencies of the system consisting of 8 can be matched.

In this way, the count content of the counter 66 is increased until the output voltage V becomes larger than the reference voltage and the signal of the comparator 62 becomes low level, and the count content is increased until the signal of the comparator 62 changes to high level again. will be retained until

Next, the operation of this device when the contactor 23 contacts the cutting tool 26 (at the time of contact) will be described.

As the slide 28 moves, the cutting tool 26 moves to the blade edge detector 2.
4, the contact 23 is moved relative to the bite 26
, the vibration of the vibrator 10 to which the contactor 23 is fixed is suppressed, so that the vibration transmitted to the vibration detection body 18 is rapidly reduced. Therefore, the output voltage (2) output from the vibration detector 18 and converted into direct current by the waveform shaping circuit 58 becomes less than the threshold voltage, as shown in FIG.

This output voltage ■ is supplied to the comparators 60 and 62 as in the non-contact case.

In the comparator 60, the output voltage ■ is compared with the threshold voltage, and in this case, since it is below the threshold voltage, the comparator 60 outputs a high level blade edge detection signal. Based on this detection signal, the servo motor that drives the slide 28 is stopped, and the origin of the blade edge position is automatically set. Since the position of the slide 28 is constantly detected by the slide position detection device, the slide position itself when the blade edge position detection signal is issued is set as the origin of the blade edge position, or is used as a reference point for setting the origin. It is possible.

The operations after the comparator 62 are the same as in the case of non-contact, so the explanation will be omitted here.

In this embodiment, the vibrator 10 is generally formed of a single thin plate bent into a U-shape, and both arms of the U-shape are attached to the main body 12. In other words,
The contactor 23 is allowed to vibrate only within a plane perpendicular to the surface of the thin plate. Therefore, the contactor 23 is prevented from vibrating in directions other than within this plane, thereby preventing the accuracy of position detection of the cutting tool 26 in the ±X direction and the -Z direction shown in FIG. 2 from decreasing. Moreover, since the amplitude of the contactor 23 is particularly large in the ±X directions, the sensitivity in those ±X directions, which are involved in machining accuracy of the workpiece, is good.

In addition, since the vibrator 10 is composed of a thin plate with a symmetrical shape, even if it is deformed due to thermal expansion, the contactor 10
3 only moves on the axis of symmetry. Therefore, no error occurs in the detection of the cutting edge in the ±X directions shown in FIG.

Although one embodiment of the present invention has been described above based on the drawings,
The present invention can also be implemented in other embodiments.

In the above-described embodiment, the contactor 23 for making scheduled contact with the object is fixed to the vibrator 10, but the contactor 23 does not necessarily have to be a separate part;
The protrusion that functions as a contactor is the vibrator 10.
It may be installed protrudingly.

Further, in the above embodiments, the oscillating body 16 and the vibration detecting body 18 are piezoelectric elements having a bimorph structure. This means that the tool position measurement error is 5X10-”m.
This is because this piezoelectric element is suitable for meeting this high requirement at the lowest possible cost and miniaturizing the blade edge detector. Therefore, depending on the purpose, the piezoelectric element may have a unitary structure, and quartz, tourmaline, Rochelle salt, or barium titanate may be used as the material of the piezoelectric element.

Further, the comparator 62 in the above-mentioned embodiment is the third
Although it is directly connected to the counter 66 as shown in the figure, an AND circuit 72 is added between these comparators 62 and the counter 66 as shown in FIG. The output terminal of the newly connected NOT circuit 74 is connected to the output terminal of the A
They may be connected to the two input terminals of the ND circuit 72, and the output terminal of the AND circuit 72 may be connected to the input terminal of the counter 66. The control circuit 50 is changed in this way, and as shown in FIG. 7, ■ the reference voltage is higher than the threshold voltage, and ■ the reference voltage is
If the threshold voltage is set to be higher than the normal output voltage Vt of the vibration sensor 18 during contact, If the output voltage (2) is below the reference voltage even in the non-contact state, it is determined that there is a possibility of a malfunction occurring, and a high-level count instruction signal is input to the counter 66. In this way, it is possible to prevent malfunctions from occurring when there is no contact.

Furthermore, the comparators 60 and 62 may have a dead zone around the threshold voltage and the reference voltage to prevent chattering and provide a more stable circuit.

In addition, various changes may be made to the present invention without departing from its spirit.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a cutting edge detector that is an embodiment of the present invention, and FIG. 2 is a plan view showing the positional relationship between the cutting edge detector and a cutting tool when the cutting edge detector is in use. . FIG. 3 is a block diagram showing the blade edge detector and its control circuit. FIG. 4 is a graph showing the output voltage generated in response to changes in the resonance frequency of the imaging sensing body used in the above example, and shows the output voltage generated in response to changes in the resonance frequency when the temperature conditions are 0°C, 25°C, and 45°C. It shows that the Figure 5 shows the change in the output voltage of the vibration detector when the cutting edge extractor is not in contact with the cutting edge of the cutting tool (non-contact) and when it is in contact with the cutting edge (in contact). It is something. FIG. 6 is a block diagram showing a modified part of the control circuit in another aspect of the embodiment described above. FIG. 7 shows the reference voltage in the embodiment shown in FIG.
Threshold voltage, normal output voltage Vn of vibration detector during non-contact
It is a graph showing the relationship between the normal output voltage Vt of the vibration detector and the vibration detector at the time of contact. FIG. 8 is an enlarged plan view showing the cutting edge of the cutting tool.

Claims (4)

[Claims] (1) While vibrating the vibrator, the vibrating state of the vibrator is monitored while moving the vibrator and the target object relative to each other, and when the vibration state changes beyond a predetermined condition, the target object is moved to the position of the vibrator. An object detection method characterized by determining that an object exists. (2) a main body, a vibrator supported by the main body, an oscillator fixed to the vibrator and exciting the vibrator to vibration, and voltage supply means for supplying an alternating voltage to the oscillator; A vibration detector is fixed to a vibrator and converts the vibration of the vibrator into an alternating voltage.The output voltage of the vibration detector is compared with a predetermined threshold voltage, and if the output voltage is less than the threshold voltage. and detection signal generating means for generating a target object detection signal. (3) The object detection device according to claim 2, wherein the oscillating body and the vibration detecting body are piezoelectric elements. (4) The voltage supply means compares the output voltage with a predetermined reference voltage, and if the output voltage is less than or equal to the reference voltage,
Claim 2 comprising frequency changing means for changing the frequency of the supply voltage until the output voltage exceeds the reference voltage.
The object detection device according to item 1 or 3.