JPS6150758A - Abnormality detecting device of multi-edged rotary tool - Google Patents

Abstract

PURPOSE:To efficiently detect abnormality of a multi-edged rotary tool, by calculating a level of ratio of a detection value in the first and the second frequenty component detecting means and comparing this ratio of the detection value with a predetermined value to be decided. CONSTITUTION:A shunt resistor 2 detects a motor current I, and the motor current I, whose noise is removed by a low-pass filter 10, is converted into a digital value by an A/D converter 3 and input to the first and the second frequency component detecting means 11, 12. Further a device, detecting a rotation frequency component phis by cutting force of each edge and a frequency component phin of a cutting force uniform component through the Fourier conversion or the like to be input to a decision means 13 and calculating ratio phis/phin, outputs an abnormality signal S to an alarm means 9 unless the ratio phis/phin is smaller than a predetermined value F by comparing the ratio phis/phin with the value F to be decided.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an abnormality detection device for detecting an abnormality such as a chipped blade of a multi-blade rotary tool.

[Prior art]

FIG. 1 is a block diagram of a conventional abnormality detection device for a multi-blade rotary tool. In Figure 1, ■ is a drive device consisting of a spindle motor, a servo motor, etc. of a rotary tool consisting of n blades, and 2 is a junt resistor as a means for detecting the load current I supplied to the motor 1. 3 is an A/D converter, 4 is an amplitude value output unit that reads out the amplitude value [w of the motor current I, 5 is an average value output unit that reads out the average value 1r of the motor current I, and 6 is the above amplitude value Tw and the average. A ratio calculation unit that calculates the ratio A (Iw/Ir) with the value 1r; 7 a storage unit that stores the criterion Ao that is a standard for determining the ratio; 8 inputs from the ratio calculation unit 6 and the storage unit 7; 9 is a determination unit 8 which compares and determines and outputs an abnormality signal S when an abnormality is determined.
This is an alarm means that issues an alarm in response to an abnormality signal S from.

The operation of the conventional abnormality detection device for a multi-blade rotary tool will be described below with reference to FIG. Now, in a multi-blade rotary tool that cuts a workpiece (not shown) by the rotation of the motor I, cutting resistance is generated every time the cutting blade hits the workpiece, and the motor current {circle around (2)} flowing through the motor 1 becomes a pulsating current. Here, this motor current I is detected by a shunt resistor 2, converted from an analog signal to a digital signal by an A/D converter 3, and inputted to an amplitude value output section 4 and an average value output section 5. The amplitude value output section 4 counts the input digital signals and outputs an amplitude value 1w. On the other hand, the average value output section 5 counts the digital signals and outputs the average value Ir of the motor current I. Next, the ratio calculation unit 6 calculates the ratio A(rw/I
r) is calculated and input to the comparison/judgment section 8. Comparison/judgment section 8
Then, the input ratio A is compared with the normal ratio Ao (judgment standard) stored in the storage unit 7, and when the ratio A becomes larger than the determination standard Ao, an abnormality signal is issued as an alarm. It outputs to means 9 and generates an alarm. Here, if the cutting edge of the outer cutting blade is damaged (blade spill), the motor 1
The load increases, and the amplitude value Iw of motor current ■ increases. Therefore, the ratio A (1w/Ir) also increases and becomes larger than the determination standard AO, so the comparison and determination section 8 issues an abnormality signal (determination signal) S, and the alarm means 9 detects an abnormality! Alert. Note that the motor may be stopped based on the output of the determination unit 8.

However, in the conventional equipment as described above, if the type of workpiece is changed or the cutting conditions are changed, the above ratio A (Iw/Ir) also changes, and the criterion lAo must be changed accordingly. Must be. That is, first, the normal amplitude value 1w and the average value 1r are measured with a normal tool, and the judgment criterion A is determined.

must be stored in the storage unit 7.

Therefore, when the cutting conditions differ, such an operation must be performed each time, which has the disadvantage of poor work efficiency.

[Summary of the invention]

The present invention was made in view of the drawbacks of the conventional devices as described above, and the present invention detects the rotational frequency component of the drive device of a rotary tool consisting of n blades based on the load current or power consumption of the drive device or the output of the torque detection means. A first frequency component detection means detects φS, a second frequency component detection means detects a frequency component Φn of φs×n, calculates the magnitude of Φs/Φn, and compares and determines this value with a predetermined value F. However, the drawbacks of the above-mentioned conventional example are eliminated by comprising a determining means for outputting a determining signal. This will be explained in detail below using examples.

[Embodiments of the invention]

FIG. 2 is a block diagram showing an embodiment of an abnormality detection device for a multi-blade rotary tool according to the present invention.

In the figure, the same components as those in the conventional device of FIG. 10 is a low-pass filter for noise removal; 11 is a first frequency component detection means for detecting the rotational frequency component φS included in the motor current r during rotation of the motor 1; and 12 is a second frequency component for detecting the frequency component Φn of Φ5Xn. The detection means 13 is a determination means that calculates the magnitude of φS/Φn, compares and determines this value with a predetermined value F, and outputs a determination signal S.

The operation of the abnormality detection device for a multi-blade rotary tool according to the present invention configured as above will be described below. Motor current I detected by shunt resistor 2 has noise removed by low-pass filter 10 and is digitized by A/D converter 3. The digitized signal is input to the first frequency component detecting means 11 and the second frequency component detecting means 12, and is subjected to Fourier transform or the like to obtain a rotational frequency component Φs due to the cutting force of the multi-blade and a uniform component of the cutting force Φs.
×n frequency component Φn is detected. The detected frequency components Φs and Φn are input to the determining means 13, and the determining means 13 calculates φS/Φn and compares and determines this value with a predetermined value F. When Φs/Φn≧F, An abnormality signal S is output to the alarm means 9. Here, if the cutting edge of the cutting blade is damaged, the cutting resistance increases as described above, and the motor current
increases. Among these, the frequency component Φs increases more than the frequency component Φn, and the value of Φs/Φn increases.

Therefore, the value of Φs/Φn becomes larger than the predetermined value F.
(Φs/Φn≧F), the determination means 13 outputs an abnormality signal S.

As described above, according to the multi-blade rotary tool abnormality detection device of the present invention, by detecting changes in the frequency components φS and Φn of the cutting force, the predetermined value F is kept constant even if the cutting conditions change. Therefore, the determination of abnormality can be performed without depending on the cutting conditions, and the work efficiency of determination is improved. In the above embodiment, the motor current I detected by the shunt resistor 2 is passed through the low-pass filter 10. A/D converter 3
However, as shown in Fig. 3, each frequency component Φs is converted into an analog quantity using a band pass filter 15° and 16 without being digitized.

A similar result can be obtained by extracting Φn and using the determining means 17 to determine whether Φs/Φn≧F. Further, in the above embodiment, the motor current is analyzed, but the same effect can be obtained by detecting and analyzing the power consumption and torque of the motor 1.

〔Effect of the invention〕

As explained above, according to the abnormality detection device for a multi-blade rotary tool according to the present invention, the first frequency component detects the rotational frequency component φS of the drive device of a rotary tool consisting of zero blades from the load current of the drive device. a detection means, a second frequency component detection means for detecting the frequency component Φ1 of Φs×n, and a determination means for calculating the magnitude of the Φs/Φ angle, comparing and determining this value with a predetermined value F, and outputting a determination signal. Since it is constructed from the above, it is possible to omit the trouble of changing the determination reference value according to the cutting conditions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional abnormality detection device for a multi-blade rotary tool, FIG. 2 is a block diagram as an example of an abnormality detection device for a multi-blade rotary tool according to the present invention, and FIG. FIG. 3 is a block diagram showing another embodiment of the present invention. ■... Drive equipment (motor), 11... First frequency component detection means, 12... Second frequency component detection means, 1
3... Judgment means. In the drawings, the same reference numerals are used for the same or corresponding parts.

Claims (1)

[Claims] a first frequency component detection means for detecting a rotational frequency component Φs of the drive device of the rotary tool consisting of n blades from the load current or power consumption or output of the torque detection means; and a frequency component Φn of Φs×n. and a determining means that calculates the magnitude of Φs/Φn and outputs a determination signal by comparing and determining this value with a predetermined value F. Abnormality detection device for blade rotating tools.