JPS60244858A - Detecting device of broken tool - Google Patents

Abstract

PURPOSE:To perform easily the regulation making the amplifying rate of an amplifier 4 on a proper level by holding the peak value of AE signal by a peak value holing circuit 9 and by constituting so as to display by an indicator 12. CONSTITUTION:The AE signal obtained from an AE sensor 3 is inputted to a peak value holding circuit 9 as it is, when a chip is generated at the time t1, and the peak value is held. In case the peak value thereof is lower than the threshold level Th of a comparator 13, the break signal of a drill 2 is not outputted and the break output is not given to a break indicator 14. Since the peak value is then displayed on the indicator 12 the amplification rate of an amplifier 4 is adjusted so as to be sufficiently lower than the level Th. And when the edge of the drill 2 is broken at the time t3, the peak value of AE signal becomes bigger than the level Th and a stoppage signal is given to an analog switch 8, so even when such higher AE signal as the time t4 is generated afterwards, the circuit 9 is not informed at all.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a tool breakage detection device for detecting breakage of a tool in a machine tool using acoustic emission (hereinafter referred to as AE) generated when the tool breaks.

Conventional technology and its problems Machine tools, such as drilling machines, are often operated automatically, but the drill bit of the drilling machine often breaks, and in such cases, it is necessary to detect the breakage in some way. . As one method for detecting tool breakage of such a machine tool, an AE sensor is conventionally provided near the tool or workpiece of the machine tool, and tool breakage is detected based on the AE flaw signal obtained from the AE sensor.

According to the conventional tool breakage detection device, the signal obtained from the AE sensor is appropriately amplified, and the amplified output is discriminated at a predetermined threshold level to be used as a tool breakage signal. However, in addition to the case of tool breakage, the AE sensor may also obtain a relatively high level AE multiplied signal due to friction between the tool and workpiece or generation of chips, etc., and in order to distinguish between these and detect tool breakage, It is necessary to adjust the detection level appropriately. The detection level is adjusted by adjusting the amplification degree of the AE signal amplifier and the detection threshold level.

In conventional detection devices, the amplified output is monitored using a meter or the like, but in the event of a breakage, the meter only swings rapidly in an instant, making it difficult to judge whether the amplification level is at an appropriate level. Therefore, it has the disadvantage that adjustment is difficult and there are problems with reliability.

Purpose of the Invention The present invention has been made in view of the problems of the conventional tool breakage detection device, and is a tool breakage detection device that can easily adjust the amplification to the optimum degree and improve reliability. The purpose is to provide equipment.

Structure and Effects of the Invention The present invention is a tool breakage detection device for detecting tool breakage in a machine tool from an AE multiplied signal, which comprises an AE sensor provided near the tool of the machine tool, and an amplifier that amplifies the output of the AE sensor. a peak value holding circuit that holds the peak value of the amplified output of the amplifier; a display that displays the peak value held by the peak value holding circuit; The present invention is characterized by comprising a comparison circuit that outputs a tool breakage signal at the time of the operation, and a delay circuit that is driven by the comparison output of the comparison circuit and stops sending the AE multiplied signal to the peak value holding circuit after a predetermined period of time. .

According to the present invention having such features, since the AE multiplication signal peak value is always held by the holding circuit and displayed on the display, the AE multiplication signal peak value is always held by the holding circuit and displayed by the display, so that the AE multiplication signal peak value is always held by the holding circuit and displayed by the display. It can be set sufficiently lower than the signal breakage detection level. Furthermore, since the AE multiplied signal to the peak value holding circuit is prohibited after the tool breaks, the AE multiplied signal peak value at the time of tool breakage is displayed as is on the display.

Therefore, the peak value at the time of breakage is determined by the indication on the display.
It becomes possible to adjust the amplification factor as appropriate so that the signal amplifier remains within a range in which it does not become saturated. Therefore, setting the amplification factor is extremely easy and easy to use, and since the amplification factor can be easily set to an appropriate level, the reliability of the tool breakage signal can be improved and applied to automated machine tools, etc. This is particularly useful when

DESCRIPTION OF EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of a tool breakage detection device according to the present invention. In this figure, a workpiece 1 is fixed on the base of a drilling machine, and a drill 2 is rotated from above the workpiece 1 and pushed down at a predetermined speed to form an opening in the workpiece 1. At this time, for example, the AE sensor 3 is fixed on a base on which the work 1 is placed. The AE sensor 3 is, for example, I
It detects a wide band AE multiplied signal from about KHz to IMHz, and its output is given to an amplifier 4. The amplifier 4 is an amplifier whose amplification factor can be arbitrarily set by adjusting a variable resistor 5, and provides its amplified output to a bandpass filter 6 and an amplifier 7 for driving a display. The AE multiplied signal frequency component obtained from this amplifier 4 is a signal having a peak value below 100 KHz and a frequency component up to a high frequency, as shown by curve A in FIG. As shown by curve B in the figure, the signal has a peak value around 200 KHz. Therefore, the bandpass filter 6 is designed to match the AE multiplied signal frequency generated when the drill 2 breaks, for example, 100 to 3.
The filter is used to pass a signal of 00 KHz, and its output is given to the analog switch 8. The analog switch 8 passes or stops the analog signal according to a signal applied from the outside, and its output is applied to the peak value holding circuit 9.

The peak value holding circuit 9 includes, for example, a buffer amplifier, a switching FET, and a voltage holding capacitor, and holds the maximum value of the applied analog signal. At the output end of the peak value holding circuit 9, a switch 10 is provided to short-circuit the output of the capacitor, and an amplifier 11 having a high input impedance is further provided. The peak value signal obtained from the amplifier 11 is applied to a display 12 for display, and is also applied to a comparator 13. A reference voltage is applied to the other input terminal of the comparator 13, and when the peak value of the amplifier 11 and the reference value are compared, and the peak value exceeds the reference voltage, a breakage detection signal of the drill 2 is sent to the breakage indicator 14. Gives a breakage signal. Also comparator 13
The breakage detection signal is given to the delay circuit 15. The delay circuit 15 delays the breakage detection signal by the AE multiplied signal width when the drill 2 breaks, for example, a delay time of 2 to 3 ms, and supplies it to the analog switch 8.1. After that, band pass filter 6
The AE multiplied signal given from the AE signal is to be stopped. Further, the output of the amplifier B7 is given to a display 16 to display a signal during cutting. The displays 12 and 16 are shown in FIGS. 4 and 5, for example.
As shown in the figure, a bar graph display consisting of a light emitting diode or the like and displaying the signal level as a bar graph is used.

Next, regarding the operation of this embodiment, the third
Figures 4 and 5 showing the display status of the display 12.16
This will be explained with reference to the figures. Time t.

When this drilling machine is operated, the drill 2 comes into contact with the workpiece 1 and opens the workpiece 1 at a predetermined position. At this time, an AE multiplied signal is generated, but as shown in FIG. 3, its level is not high and it hardly passes through the band pass filter 6. Also A
It is amplified by the E times signal amplifiers 4 and 7 and displayed on the display 16.
However, for example, the display 16 only blinks slightly near the lowest level.

If friction, chips, etc. occur during cutting of workpiece 1, the AE multiplied signal frequency obtained at that time will be 200 to 300.
Since it has a peak value near KHz, it passes through the AE ratio output bandpass filter 6 which is amplified by the amplifier 4.

For example, if chips are generated at time t1, the analog switch 8 is closed, so the AE multiplied signal obtained from the AE sensor 3 is directly applied to the peak value holding circuit 9, and its peak value is held. The peak value output is then displayed on the display 12 via the amplifier 11. FIG. 4 is an example of a display showing the operating state at this time, and its peak output is given to the comparator 13. However, as shown in FIG. 3, since the threshold level Th of the comparator 13 is higher than the peak value of chips obtained here, the breakage signal of the drill 2 is not output, and therefore the breakage signal is output to the breakage indicator 14. is not given. Therefore, the cutting process on the workpiece 1 continues as it is.

Subsequently, at time t2, chips and friction occur, and the peak value exceeds the previous peak value by AE times the signal bandpass filter 6.
When the new peak value is applied to the peak value holding circuit 9 via the analog switch 8, the new peak value is held in the peak value holding circuit and displayed on the display 12. However, at this point the third
As shown in the figure, since the threshold level Th of the comparator 13 is not exceeded, no drill breakage signal is output. So let the drilling machine run for a while,
Even if a fairly high level AE multiplied signal is generated due to chips or friction, the amplification factor of the amplifier 4 must be adjusted so that the peak value shown by the display 12 is sufficiently lower than the threshold level Th, as shown in FIG. Adjust using variable resistor 5. When this amplification factor is changed, it is necessary to release the hold of the peak value holding circuit 9, so the reset button 10 is pressed to discharge the capacitor.

If the blade of drill 2 breaks for some reason at time t3, the AE multiplier has a large peak value as shown in Figure 3 and has a peak frequency around 200 KHz as shown in Figure 2. The signal is obtained from the AE sensor 3.

The signal is applied to the peak value holding circuit 9 via the AE multiplied signal amplifier 4 and bandpass filter 6. Therefore, the peak value is held by the peak value holding circuit 9, and the peak value at that time is displayed on the display 12 as shown in FIG.

At this time, since the threshold level Th of the comparator 13 is exceeded, a breakage signal of the drill 2 is outputted from the output terminal 14, and at the same time, a trigger signal is given to the delay circuit 15. Then, after the delay time of the delay circuit 15, for example, 2 mS, a stop signal is given to the analog switch 8, and after that, the AE multiplied signal is not transmitted to the peak value holding circuit 9. The chuck itself of the drilling machine directly contacts the workpiece 1, and as shown after time t4 in FIG.
Even when an E-fold signal is generated, the signal is not transmitted to the AE-fold signal peak value holding circuit 9.

At this time, as shown in FIG. 5, if the value displayed on the display 12 is less than the full scale, it can be seen that the amplification factor of the display 4 is at an appropriate level because the amplifier 4 is not saturated. However, if the display 12 becomes full scale due to breakage of the drill 2, it is considered that the amplifier 4 is saturated, and therefore, it is necessary to further lower the amplification factor.

As described above, according to the present invention, the AE multiplied signal peak value is held by the peak value holding circuit 9 and displayed on the display 12, so that the amplification factor of the amplifier 4 can be easily adjusted to an appropriate level. . Also, when changing the diameter of the drill bit, or when changing the type of workpiece or cutting conditions, it is necessary to adjust the amplification factor appropriately, but by performing the same operation, the amplification applied to the diameter of the drill can be adjusted. By selecting the ratio, it is possible to always obtain a reliable breakage detection signal.

Although this embodiment uses a bar graph display such as a light emitting diode as a display, an analog display may be used, or a digital display that directly displays numerical values may also be used.

Further, although this embodiment describes a drill breakage detection device for a drilling machine, the present invention can be applied to other machine tools, such as various machine tools such as lathes and milling machines.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the tool breakage detection device according to the present invention, Fig. 2 is a graph showing the AE multiplied signal frequency characteristics, and Fig. 3 is the A obtained when operating the drilling machine.
Graphs showing temporal changes in the E-times signal, FIGS. 4 and 5, show the display 12. when this tool breakage detection device is operated.
16 is a diagram showing a display state of No. 16. FIG. 1.------Work 2---------Drill 3
-----------A E sensor 4. 7. 11--
−−−−One amplifier 5−・−Variable resistor 6・−・−・・
・Band pass filter 8---7' analog switch 9---Peak value holding circuit io------
Resent switch 12, 16----------------------
Display device 13--Comparator 14--Broken indicator 15--Delay circuit Patent applicant Tateishi Electric Co., Ltd. agent Patent attorney Yoshiki Okamoto (and one other person) Figure 1 Figure 2 Figure 3 4 figure ma 6

Claims (2)

[Claims] (1) An AE sensor installed near a tool of a machine tool, an amplifier that amplifies the output of the AE sensor, a peak value holding circuit that holds the peak value of the amplified output of the amplifier, and the peak value holding circuit. an indicator that displays the peak value held; a comparison circuit that outputs a tool breakage signal when the peak value of the peak value holding circuit exceeds a predetermined reference level; and a comparison circuit that is driven by the comparison output of the comparison circuit; A tool breakage detection device comprising: a delay circuit that stops sending an AE flaw signal to the peak value holding circuit after a predetermined period of time. (2) The tool breakage detection device according to claim 1, wherein the indicator is a bar graph indicator.