JPS59184857A - Quality discriminating device of rotary machine - Google Patents

Abstract

PURPOSE:To decide quantitatively a quality to a noise of a rotary machine even at the time of no-load by A/D-converting the noise of the rotary machine, calculating a kurtosis, comparing it with a threshold level set in advance, and displaying its success or failure. CONSTITUTION:A noise from a motor tool is inputted by a microphone 1, and its input signal is amplified by an amplifier 5 through an attenuator 4 for protecting an apparatus. Also, it is sampled in accordance with a signal of a sampling circuit 14, A/D-converted by an A/D-converter 6, stored in a buffer memory, and thereafter, inputted to an operator 8, and a kurtosis is calculated. The kurtosis from the operator 8 is displayed on an indicator 10. At the same time, a threshold level is set in advance by a threshold level setting digital switch 12, this set value and the value from the operator 8 are compared by a comparator 11, and a character for signifying a success or a failure is displayed on an indicator 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a quality discriminating device for a rotating machine, such as a power tool, which is used for determining the overall quality of noise in a rotating machine such as a power tool.

[Prior art]

Generally, a rotating machine is composed of a plurality of components such as gears, a rotating shaft of a bearing, and a case, and the influence of these components on noise during operation is complex. Therefore, for quality control purposes, comprehensive judgment based on auditory sensation is often performed. -Human ears can distinguish subtle differences in sounds, and harsh sounds can make people feel uncomfortable, and with power tools and other rotating machinery, they can make people feel like they want to buy them, which can be a sales problem. It may happen. By the way, the auditory judgment distinguishes the level of noise generated by power tools during no-load operation, and rejects tools that emit unpleasant noises.

However, the above-mentioned judgment method tends to cause variations in the judgments of inspectors and variations due to individual differences, and is not quantitative.

There is also a method of measuring all the noise with a sound level meter and making a judgment based on the sound pressure level, but this method does not have a good correlation with the judgment based on the auditory sense.

In other words, even if the level is low, there is a harsh sound, and it does not necessarily correspond to the quality determined by the sense of hearing.

Furthermore, recently, a method has been attempted in which the vibration waveform of a nine-roller bearing is measured and the measured values are subjected to statistical processing to diagnose failures. However, this method mainly involves attaching an accelerometer to the bearing and completely processing the vibrator shape, which is time-consuming and requires a lot of effort to determine whether any damage has occurred to the bearing, which was initially in good condition. For products, quality determination is done by inspection at the time of shipment, and data from the first operation is examined for 1 hour, and all noise must be determined with almost no damage to the parts.
It is necessary to perform the above statistical processing in more detail.

[Purpose of the invention]

In view of the above points, it is an object of the present invention to provide an apparatus for determining the quality of a rotating machine that can quantitatively determine the quality of noise emitted from the rotating machine.

[Summary of the invention]

In order to achieve all of the above objects, the present invention provides a microphone that captures noise from rotating machinery, a memory that converts an analog quantity corresponding to the waveform of the noise into a digital lid and stores it, and a computing device that computes cartosis. The apparatus is equipped with a display section for displaying the kartosis, and a threshold setting switch for setting a threshold in advance according to the machine to be discriminated.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the apparatus of the present invention will be explained below with reference to all the drawings.

In Figure 1, 1 is a microphone that inputs the noise emitted from a rotating machine, such as a power tool, 2.4 is an attenuator, and 3.
, 5 is an amplifier, 6 is an A/D converter, 7 is a backup memory, 8 is an arithmetic unit that samples the sound pressure waveform output from the microphone 1 and calculates kartosis, which will be described later.
9 is an oscillator, 10 is a display unit that displays kartosis, 11
1 is a comparator, 12 is a threshold setting digital switch, 13 is a display section that displays all passes, and 14 is a sampling circuit.

Next, the measurement operation of the device of the present invention will be explained.

First, the noise from the power tool is captured by the microphone 1, and the input signal is passed through an attenuator 2 and an amplifier 3 to protect the equipment.
, and is amplified by an amplifier 5 via an attenuator 4 for range switching. Further, the signal from the amplifier 5 is sampled in accordance with the signal from the sampling circuit 14, converted from an analog quantity to a digital quantity by an A/D converter 6, stored in a backup memory, and then inputted to an arithmetic unit 8 for cart system processing. Perform all calculations. This kartosis is determined by the following method.

First, about 100 power tools are randomly selected from the production line, and at the same time as the auditory judgment by the inspector, statistical processing of the sound pressure waveform is performed. And so. FIG. 2 shows the relationship between the noise of power tools by performing statistical processing and the obtained value and the rank rating based on auditory sense. Here, the statistical processing includes the average value, standard deviation, kartosis, sixth moment, etc. of each value obtained by sampling the sound pressure waveform of the noise for 1 sec at a sampling frequency of 50 KH2. Since kartosis had the highest correlation with auditory judgment, its value is shown.

In FIG. 1, the D-rank product, which is a rejected product, did not have a curtsis above a certain value (a), and there was a clear difference between it and the passed product (A-C).

Here, curtosis is calculated by the following formula.

xI; Input signal N; Returning to the sampling 1 fixed number, the kartosis from the calculator 8 is displayed on the display 10. At the same time, a threshold value is set in advance using the threshold setting digital switch 12, and the set value and the value from the calculator 8 are compared by the controller 11, and the display 13 indicates pass or fail. Lights up the characters to be displayed.

The device of the present invention houses the component parts in one case,
It can also be used as a portable device using batteries as a power source.

[Effects of the Invention] The quality can be determined quantitatively even under no load.

[Brief explanation of the drawing]

FIG. 1 shows the configuration of the quality determination device for rotating machinery according to the present invention.
-) ° Ron 2 Figure 2 is a diagram for explaining the relationship between the noise of a rotating machine and kartosis. switch. ■ 1 Figure

Claims (1)

[Claims] a microphone for capturing noise from rotating machinery; a memory for converting analog quantities corresponding to the noise waveform into digital quantities; A quality discriminating device for a rotating machine characterized by comprising a threshold setting switch for setting a threshold according to a machine to be discriminated.