JPS61173153A - Pseudo fracture signal generator - Google Patents

Abstract

PURPOSE:To adjust the sensitivity of an AE sensor to be provided near the tool of a machine tool and work by having a noise generator, differentiation circuit for differentiating a square wave output and multiplier circuit for multiplying the output thereof to obtain pseudo fracture signal. CONSTITUTION:The fracture or the like of the tool of the machine tool is detected by the AE sensor disposed near the part thereof where the tool and the work contact. A pseudo fracture signal generating circuit 1 which is so constituted as to pass the output from a noise generating circuit 4 through a band pass filter 5, to differentiate the output from a square wave oscillator 6 by the differentiation circuit 7 and to apply both outputs to an AE signal converter after multiplying and amplifying the same is provided in this stage. The sensitivity of the AE sensor is adjusted by attaching the converter 3 to the position where the tool contacts with the work and operating the same to generate the signal having the same characteristic as the characteristic of the AE signal in the stage of tool fracture. The sensitivity of the AE sensor is thus maintained a the optimum value regardless of the mounting condition, etc. thereof and the exact operation thereof is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to acoustic emincigon (
(hereinafter referred to as AE) for monitoring.

The present invention relates to a pseudo-breakage signal generating device used for adjusting the sensitivity of an AE sensor of a tool breakage detection device that automatically detects tool breakage.

[Summary of the invention]

The pseudo-breakage signal generating device according to the present invention includes a noise generator, a differentiation circuit for differentiating rectangular wave output, and a multiplication circuit for multiplying the outputs, and a pseudo-breakage signal is obtained by the multiplication output. be. By driving an AE signal converter installed near the contact between the tool of the machine tool and the workpiece using such a pseudo-breakage signal, it becomes possible to accurately set the sensitivity of the AE sensor.

[Prior art and its problems] When cutting an object to be machined (hereinafter referred to as a workpiece) using a tool on a machine tool, the tool may break for some reason or become clogged with chips, resulting in abnormal cutting. . With the recent progress in factory automation, there is a strong demand for automatic detection of tool breakage and abnormal cutting. As a method for detecting tool breakage in machine tools, conventional methods have been to
An apparatus has been proposed that includes a sensor and detects tool breakage based on an AE multiplied signal obtained from the sensor.

However, according to the conventional tool breakage detection device, the AE sensor is mounted near the tool or in contact with the workpiece, but the AE multiplied signal level varies greatly depending on the mounting position. Therefore, in conventional tool breakage detection devices, the sensitivity of the AE sensor is set to a predetermined standard value according to the size of the tool, and the attenuation rate between the tool and AE sensor of each machine tool is corrected by trial and error. Ta. However, since the AE multiplied signal at the time of tool breakage is obtained only at the time of breakage, it is difficult to confirm the mounting position and mounting state of the AE sensor, making it difficult to reliably detect tool breakage. Furthermore, the type of tools,
For example, when the drill diameter is changed or the cutting conditions are changed, the AE signal level changes, making adjustment difficult and making it difficult to use.

[Purpose of the invention]

The present invention has been made in view of the problems of the conventional tool breakage detection device, and uses a relatively simple configuration to adjust the sensitivity of the AE sensor so that the AE multiplied signal has the same characteristics when a tool breaks. It is an object of the present invention to provide an 82-band failure signal generating device that can continuously generate an AE multiplied signal of a predetermined level.

[Structure and effects of the invention]

The present invention is a pseudo-breakage signal generating device for use in adjusting the sensitivity of a tool breakage detection device that has an AE sensor installed near a tool of a machine tool and detects breakage based on an AE multiplied signal when a tool breaks. It has a pseudo-breakage signal oscillator that oscillates a pseudo-breakage signal including an AE multiplied signal frequency obtained at the time of breakage, and an AE signal converter that is provided near the tool of the machine tool and is driven by the output of the pseudo-breakage signal oscillator. It is characterized by this.

According to the present invention having such characteristics, it is possible to generate a pseudo-breakage signal using an analog circuit with a relatively simple configuration, and by driving the AE signal converter based on the signal, the machine tool is set to a predetermined level. It is possible to give a pseudo-breakage signal of Since the pseudo-breakage signal thus given is propagated through the workpiece and the base of the machine tool, it is possible to adjust the sensitivity of the AE sensor to an optimal value even if the AE sensor is installed at any position. Furthermore, it is also possible to use this pseudo-breakage signal to adjust the frequency characteristics, etc. of the signal processing section of the tool breakage detection device connected to the subsequent stage of the AE sensor.

[Description of Embodiments] (Configuration of a pseudo-breakage signal generating device) FIG. 1 is a block diagram showing the overall structure of an embodiment of the pseudo-breakage signal generating device according to the present invention. As shown in this figure, the pseudo-breakage signal generator includes a drive circuit I that generates the pseudo-breakage signal, a level setter 2 that sets the level of the drive circuit, and an AE signal converter 3 that transmits the pseudo-breakage signal to the machine tool. There is. In FIG. 1, a noise generating circuit 4 of a drive circuit 1 is a generating circuit that generates white noise having a uniform spectrum up to a frequency exceeding 300KIIz, and its output is given to a bandpass filter 5. The bandpass filter 5 transmits only noise having components around a frequency of 300 Kh to the next stage. Further, the rectangular wave oscillator 6 is an oscillator that oscillates a rectangular wave with a constant period, and its output is given to the differentiating circuit 7. The outputs of the bandpass filter 5 and the differentiating circuit 7 are given to a multiplier 8. The multiplier 8 multiplies these outputs to make the differential signal the envelope line f! (It generates a U-breakage signal, and its output is given to the amplifier 9. The amplifier 9 amplifies the pseudo-breakage signal with an amplification factor based on the level setting of the level setter 2, and its output is a power The signal is supplied to an amplifier 10. The power amplifier 10 amplifies the power of this signal, and the output is applied to an AE composed of a piezoelectric element.
This signal is applied to the signal converter 3.

(Configuration of tool breakage detection device) Next, FIG. 2 is a block diagram showing the overall structure of a tool breakage detection device to which this pseudo breakage signal generating device is applied. In this figure, before cutting the work 11, the AE signal converter 3 of the above-mentioned pseudo-breakage signal generator is installed in advance at the position where the blade of the drill 12 contacts the upper part of the work 11. Then, an AE multiplied signal is detected near the tool where the workpiece 11 is placed, for example, on the base 13 as shown in FIG.
An E sensor 14 is provided. The AE sensor 14 is a broadband AE sensor that detects a pseudo-breakage signal from the AE multiplied signal AE signal converter 3 from a tool such as the drill 12, and its output is given to an analog switch 15. The analog switch 15 connects and disconnects analog signals using an external output, and its output is applied to an amplifier 16. The amplifier 16 is an amplifier whose amplification factor can be arbitrarily set by adjusting the variable resistor 17, and its output is sent to two band pass filters 18, 19 and a cutting level indicator 20.
It is given to The band pass filter 18 is a filter with a center frequency of 300 KHz, and the band pass filter 19 is a filter with a center frequency of 50 Kl (z), and transmits only signals near the respective center frequencies to the next stage detector 21.22. detects the input signal and obtains an output according to the amplitude, and the output of the detector 21 is given to a differentiating circuit 23, and the outputs of the detectors 21 and 22 are given to a comparator 24. Differentiating circuit 23 transmits only the steep changes in the input signal to the next level level judge 25 and the broken/abnormal level indicator 26.The level judge 25 compares the input signal with a predetermined reference level, and the input signal If the output is large, the output is transmitted to the breakage detection circuit 27 and the abnormal cutting detection circuit 28.The comparator 24 also compares the outputs of the detectors 21 and 22, and transmits the output to the breakage detection circuit 27 only when the output of the detector 21 is large. The breakage detection circuit 27 is a logic circuit that takes the AND of these inputs to detect tool breakage, and outputs the breakage detection signal to the outside via the output circuit 29.The abnormal cutting detection circuit 28 Detects abnormal cutting based on the output of the level determiner 25, and transmits the output to the outside via the output circuit 30.

(Operation of pseudo-breakage signal generator) Next, the operation of the pseudo-breakage signal generator of this embodiment will be described. First, the AE signal converter 3 is fixed on the upper part of the workpiece 11 as shown in FIG. 2, and a pseudo-breakage signal level is set by the level setting device 2 according to the type of tool used, for example, the drill diameter.

Now, when the drive circuit 1 is operated, white noise having uniform frequency components is generated from the noise generation circuit 4 as shown in FIG. A rectangular wave having a predetermined cycle and a duty of 50% is generated. When this rectangular wave signal is differentiated by the differentiating circuit 7, a differentiated signal that changes sharply at the rising and falling edges of the signal is obtained, as shown in FIG. 3(C). The output of the noise generation circuit 4 is given to the multiplier 8 via the bandpass filter 5, and at the same time, the differential output is given to the multiplier 8, so that the multiplication by the multiplier 8 generates a predetermined cycle as shown in FIG. 3(d). A burst-like signal that rises sharply and then decays is obtained. This signal is amplified by an amplification factor set in the level setter 2 depending on the type of tool used, for example, the drill diameter, by the amplifier 9, and is transmitted to the AE signal converter 3 via the power amplifier 10. In this way, the electrical signal is converted into mechanical vibration, which is transmitted to the AE sensor 14 via the workpiece 11 and the base 13 as an ultrasonic pseudo-breakage signal.

(Operation of tool breakage detection device) If the pseudo breakage signal generator is thus applied to the machine tool, this signal is used to adjust the sensitivity of the AE sensor 14 of the tool breakage detection device. That is, the amplification factor of the amplifier 16 is adjusted by the variable resistor 17 so that the display level of the cutting level indicator 20 becomes a predetermined value when the pseudo-breakage signal is received. In this way, it becomes possible to transmit the AE multiplied signal from the AE sensor 14 to the signal processing section at an appropriate level. When the tool breaks, a breakage signal having a peak around 300 K Ilz is obtained, so it is transmitted to the detector 2 via the bandpass filter 18.
1 detects the level, and comparator 24 detects the level at 50K.
Tool breakage is detected by comparing it with a signal having a frequency component of Hz. Further, when the signal rises rapidly by the differentiating circuit 23, if the level is higher than a predetermined value, an output is obtained from the level determiner 25, and the breakage detection circuit 2
7, tool breakage is detected based on the logical product condition. In this way, this tool breakage detection device improves the reliability of tool breakage by combining both frequency domain breakage detection and time domain breakage detection.

In this embodiment, by passing the output of white noise through a band-pass filter, a signal with a spread on the frequency axis centering around a frequency of 300 KHz is multiplied by a differential signal to generate a pseudo-breakage signal similar to a breakage signal. However, if it is used only to adjust the sensitivity of the AE sensor, it can be made into a pseudo-breakage signal by multiplying the output of an oscillator with a single frequency around 300 KHz and the differential circuit. Also frequency 30
AE using a sine wave burst wave signal around 0 to 11z
It is also possible to adjust the sensitivity of the sensor.

Further, in this embodiment, the pseudo-breakage signal converter 3 is attached to the workpiece 11 and the AE sensor 14 is attached to the base 13, but the AE sensor can also be attached to the tool or tool support.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the circuit section of the pseudo-breakage signal generating device according to the present invention, and FIG. 2 is a block diagram showing an example in which the pseudo-breakage signal generating device of the present invention is applied to a tool breakage detection device. FIG. 3 is a waveform diagram showing waveforms of various parts of the pseudo-breakage signal generating device according to this embodiment. l・--Drive circuit 2--Level setter 3-
...AE signal converter 4-----Noise generation circuit 5.18.19...Band-pass filter 6--Square wave oscillator 7.23-- −
Differentiator circuit 8--・--multiplier 9--------～・
Amplifier 10----Power amplifier 11'
-----------Work 12---------Drill 1
3------Base 14--A E sensor
16---------Amplifier 25-- Level determiner Patent applicant Tateishi Electric Co., Ltd. Agent Patent attorney Yoshiki Okamoto (and one other person) Figure 1 1-...%iH circuit

Claims (5)

[Claims] (1) A pseudo-breakage signal generating device used for adjusting the sensitivity of a tool breakage detection device that has an AE sensor installed near a tool of a machine tool and detects breakage based on an AE signal when a tool breaks, A pseudo-breakage signal oscillator that oscillates a pseudo-breakage signal including the frequency of an AE signal obtained at the time of breakage, and an AE signal converter that is provided near the tool of a machine tool and is driven by the output of the pseudo-breakage signal oscillator. A pseudo-breakage signal generating device comprising: (2) The pseudo-breakage signal oscillator includes: a noise generation circuit that generates noise including the frequency of the AE signal obtained when the tool breaks; and a rectangular wave generation circuit that generates a rectangular wave signal with a predetermined cycle; Claim 1 comprising: a differentiation circuit that differentiates a rectangular wave output signal of a rectangular wave generation circuit; and a multiplication circuit that multiplies the output of the differentiation circuit and the output of the noise generation circuit. The pseudo-breakage signal generating device described in 2. (3) The pseudo-breakage signal generating device according to claim 2, wherein the noise generating circuit generates random noise including the frequency of an AE signal obtained when a tool breaks. (4) The pseudo-breakage signal generating device according to claim 1, wherein the pseudo-breakage signal oscillator is an oscillator that intermittently oscillates the frequency of the AE signal obtained when the tool breaks. (5) The pseudo-breakage signal oscillation unit includes an oscillation circuit that oscillates the frequency of the AE signal obtained when the tool breaks, a rectangular wave generation circuit that generates a rectangular wave signal with a predetermined period, and the rectangular wave generator. Claim 1 comprising: a differentiation circuit that differentiates a rectangular wave output signal of the circuit; and a multiplication circuit that multiplies the output of the differentiation circuit and the output of the oscillation circuit.
The pseudo-breakage signal generating device described in 2.