JPS5997015A - Sound inspector for rotary body - Google Patents

Abstract

PURPOSE:To enable discrimination of abnormal sounds by a method wherein sounds generated from an object to be inspected is detected, converted into an effective value with a switch of the band-pass frequency according to a clock signal and after an A/D conversion, the frequency is inputted to be compared with a reference level by an arithmetic dicision section. CONSTITUTION:Sounds of an object to be inspected is detected with a microphone 11 and the center frequency is determined by a clock frequency fCLK passing through a preamplifier 12, an LPF13 and a switched capacitor filter 14. An output of the filter 14 is converted into a digital value via an effective value computing sectin 16 an and A/D convertor section 17 and inputted into a CPU arithmetic decision section 18. In the meanwhile, revolutions of a section to be inspected are detected with a rotation sensor 19 and inputted into the CPU18 from a rotation measuring section 20. The CPU18 computes a band-pass frequency of BP1-BP5 from the revolutions fO and input a band-pass effective value into a filter 14 so as to switch it sequentially. Thus, sound pressures of the BP1-BP5 are measured to be compared with the limit to the accepted product and an abnormal sound is identified when they exceed the predetermined limit.

Description

[Detailed description of the invention] The present invention relates to a sound testing device for a rotating body.

Conventionally, sound tests for rotating bodies such as rotors and speed reducers have mostly been based on human sensory tests. This is because humans have excellent hearing ability (hearing ability, tone discrimination ability, sound source detection ability, etc.) for minute sounds.
This is due to the fact that automating these processes with machines would be expensive and unprofitable.

However, sound testing can be broadly divided into two types. - is the "noise level", which is inspected according to product standards. Also,
The other one is "abnormal noise", which indicates an internal defect in the product, such as a hit.
There is a device that detects the characteristics of sounds caused by cracks, foreign objects, rattles, etc., identifies abnormalities, and inspects for internal defects.

The present invention is particularly aimed at the inspection of the latter type of "abnormal sounds," but a conventional example of automation is a multi-stage filter system as shown in FIG.

That is, the sound of the object to be inspected is usually detected using a microphone l (although a vibration acceleration sensor may also be used), amplified by a gurian f2, and then transferred to an n-stage pantone 4-filter (BPFI, BPF2...
......-BPFn). here,
An example of the sound pressure-frequency characteristic of the microphone output is shown in FIG. 2, and the bandpass filter has its pass frequency band set at n locations where the characteristics of the sound of the object to be inspected are likely to appear. The band/gas filter output is the effective value calculation unit RMSI
= Converted to an effective value by RMSn, and compared with CMPI~C
MPn is compared with a pass/fail judgment reference level. and,
The determination unit 3 is configured to determine the content of the defect based on the pass/fail results of n frequency bands.

However, in automatic multi-product mixed inspection, it is necessary to set the test frequency band and pass/fail judgment standard level for each product.
With the above configuration, it is difficult to vary the frequency band. For this reason, the number of band and arm filters must be increased, resulting in an increase in cost.

The present invention has been proposed in view of the above points, and aims to provide a high-speed, high-precision sound inspection device that can easily switch between different types of sound in order to identify abnormal sounds by analyzing the same wave number of sound. This is the purpose.

That is, in order to make the present invention easier to switch over in multi-product inspection, which is a drawback of the conventional method, we conducted an experiment to investigate the characteristics of the sound of the motor that is the object to be inspected, and found the following. did.

A small three-pole commutator motor was used as the motor, and the sound pressure-frequency characteristics of each type were measured, and the results were as shown in Figure 3.

In FIG. 3, f is the rotational frequency of the motor, and in the non-defective pattern, peaks are at 1, 3, 6, and 12 times f. In addition, it was found that in the case of abnormal sound defects, characteristics tend to appear in the valley portions of each peak, as shown by the φ broken line.

Therefore, if the pantone frequency ranges between the valleys of each peak are BPI, BF2, .

Here, the rotational frequency f differs depending on each product, but f is determined to be 0.
If 0, BPI, B
F2,......The band frequency of BF2 can be determined.

FIG. 4 thus shows an embodiment of the invention.

In the figure, 11 is a sound sensor that detects the sound of the object to be inspected such as a microphone, 12 is a gliander that amplifies the output from the microphone 11, and 13 is a low frequency of the amplified output. A low-pass filter that only passes
14 is the clock frequency fCL from the clock oscillator 15
A switched capacitor filter whose band is controlled by K; 16 is an effective value calculation unit that converts the filter output into an effective value; 17 is an AD conversion unit that converts the output from the calculation unit 16 into a digital signal; 18 is an AD conversion unit 19 is a rotation sensor that detects the rotation of the object to be inspected; 20 is a rotational speed measuring section; the output ff'1 is added to the CPU calculation and determination section 18;

In summary, the present invention provides means for detecting the sound of an object to be inspected (
sound sensor 11, gliander 12), means for analyzing sound frequency (low gas filter 13, switched capacitor filter 14, effective value calculation section 16, AD conversion section 17)
, a clock oscillation section 15, and a CPU calculation/judgment section 18), and means for measuring the rotation frequency f of the object to be inspected (rotation sensor 9, rotation speed measuring section 20).

In addition, in the above, the switched capacitor filter 4
is an element whose cutoff frequency can be controlled by varying the clock, and is used as a bandpass filter in this part.

Next, the present invention will be explained in detail with reference to FIGS. 3 and 4.

The sound of the object to be inspected is detected by the microphone 11 and amplified by the gliander 2. The low-pass filter 3 operates as an anchoring filter for the next switched capacitor filter 4. That is, the S-switched capacitor filter 4 operates as a pantokes filter, and its center frequency is determined by the frequency of the clock fCLK from the clock oscillator 15.

The switched capacitor filter output is the effective value calculation unit 16
The voltage is converted into an effective value voltage in the AD converter 17, and is converted into a digital value in the AD converter 17, and then input to the CPU calculation converter 18.

On the other hand, the rotational speed of the object to be inspected is detected by a rotation sensor 19,
The rotational speed measuring section 20 inputs the signal to the CPU calculation/determination section 18 .

The CPU calculation determination unit 18 calculates the rotation speed from f0 to f shown in FIG.
< , BPI, BF2.・・・・・・・・・BF
2, the frequency fCLK of the clock oscillation section is changed so that the switched filter 14 is sequentially switched, and the bandpass effective value is input.

As described above, BPI and BF2 shown in FIG.

......The sound pressure of BF2 is measured and compared with the non-defective limit, and if it exceeds the non-defective limit, it is determined that the sound is abnormal. The non-defective product limit levels are Ll, L2.・・・・・・・・・
, L5, if any of them exceeds the limit, it is an abnormal sound defect. In the example shown in FIG. 3, BF2 and BF2 are equal.

According to the present invention, there is provided a means for detecting the sound generated by a rotatable object to be inspected, an output from the detecting means is provided, and the band/92 frequency is switched according to the clock signal. A switched capacitor/accumulator filter, an effective value calculation section to which an output from the filter is applied and converts the filter output into an effective value voltage, an AD converter for digitizing the output of the effective value calculation section, and A.D.
An arithmetic and judgment section to which the output from the converter is added, a means for analyzing the frequency of the sound, and a means for measuring the rotational frequency of the object to be inspected; When the output of the measuring means is input, arithmetic processing is performed to control the clock signal, and the effective values of the band and 9 band frequencies are input to determine abnormal sounds; The filter circuit is smaller and cheaper than conventional filters because the external frequency is switched.

(b) Since the measurement bandpass frequency is switched depending on the rotational speed of the object to be inspected, the determination accuracy is improved without being affected by the parallax Φ of the rotational speed of the object to be inspected.

0) Even when testing a wide variety of products, there is almost no need to add any circuits, and the test can be switched instantly.

Furthermore, it is easy to set the determination level for each item.

There are advantages such as

Note that the present invention can also be applied as a device for detecting abnormalities in automated equipment.

[Brief explanation of drawings]

FIG. 1 is a conventional example, FIG. 2 is an explanatory diagram of the operation of the conventional example, FIG. 3 is an explanatory diagram of the operation of the present invention, and FIG. 4 is an embodiment of the present invention. 11...Sound sensor such as a microphone, 12...Grianzo, 13...Low pass filter, 14...
Switched capacitor/cross filter, 15... Clock oscillation unit, 16... Effective value calculation unit, 17... AD conversion unit, 18... CPU calculation determination unit, 19... Rotation sensor, 20...・Rotation speed measuring section.

Claims (1)

[Claims] means for detecting sound generated by a rotatable object to be inspected;
A switched capacitor filter is provided with the output of this detection means, and whose frequency is switched according to the clock signal, and the output of this filter is provided, and the filter output is converted to an actual value voltage. An effective value calculation unit for conversion, and A for digitizing the output of this effective value calculation unit.
comprising a D converter and an arithmetic/judgment unit to which the output from the AD converter is applied, means for analyzing the frequency of the sound, and means for measuring the rotational frequency of the object to be inspected; The rotating body, wherein the arithmetic/determining unit performs arithmetic processing when inputting the output of the rotational frequency measuring means, controls the clock signal, and inputs the effective value of the bandpass frequency to determine abnormal sound. Sound test installed.