JPH07134118A - Method and apparatus for sorting sound - Google Patents

Abstract

PURPOSE:To inspect the quality of sintered bodies having microcracks in the insides at high precision by dropping the sintered bodies of metal oxides to a resonance stand, detecting the resonance sound, converting the resonance sound into acoustic waveforms, and computing the sound level and the damping degree of the acoustic waveforms. CONSTITUTION:A sintered body 7 is transported to a supply conveyer 1, its posture is adjusted by a rotary apparatus 2, and the sintered body 7 is pinched by a hand 5, elevated, and dropped from the height 20mm above a resonance stand 6. The resonance sound of the resonance stand 6 and the the sintered body 7 which is generated at the time of dropping the sintered body 7 is detected by a microphone attached to a detector 15 and amplified 16 and then the signal intensity and the damping degree are compared with the standard values and the quality of the sintered body is judged 17. The tested sintered body 7 is taken out by a scraper and if the quality is inferior, an inferior product discharging shutter 8 is opened and if the quality is good, the sintered body 7 is stored in a case 13 through a discharging conveyer 9 and a guide plate 12. The shape of the test specimen is made to be an arc segment shape and if the arc angle is 80 deg. or larger, the quality determination is carried out more easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic selection method and an acoustic selection device for determining the quality of a sintered body by acoustic selection.

[0002]

2. Description of the Related Art Sintered bodies produced by the powder metallurgy method are subject to subtle differences in molding, firing or processing conditions.
Poor quality such as cracks may occur after sintering. This crack is a crack of the product obtained by processing the sintered body,
It becomes a factor that causes chipping. For example, since ferrite magnets are used in in-vehicle motors and the like, demands for reliability regarding strength are strict, and strict quality control is performed to prevent cracks and chips.

Cracks and cracks in ferrite magnets are caused by microcracks in the ferrite magnet. Penetrant flaw detection tests such as the dye penetrant flaw detection method and the fluorescent penetrant flaw detection method have been used to confirm the presence or absence of the microcracks. In the penetrant flaw detection test, a ferrite magnet is immersed in a penetrant containing a red dye or a fluorescent substance, the red dye and the fluorescent substance are permeated into the defective portion, and then the red dye and the fluorescent substance in the defective portion are developed with an adsorbing fine powder. Is a method of visually observing the generated instruction pattern and determining the presence or absence of cracks.

In the penetration flaw detection test, the presence or absence of microcracks on the surface of the magnet can be confirmed, but the presence or absence of microcracks existing inside the magnet cannot be confirmed. Therefore, defects may occur due to the microcracks existing inside the magnet. Also, according to these methods,
After the inspection, the magnet surface is contaminated with chemicals, resulting in defective adhesion in the next step, so that complete cleaning is required.

In order to solve the above problems, there is a method of detecting cracks and the like in a sintered body with a hitting sound.
No. 2758. This is because the surface of the sintered body is hit with a hitting tool, the generated hitting sound is detected by a sensor, the sensor output is amplified and converted, the attenuation degree of the acoustic waveform is obtained, and compared with the reference attenuation degree. This is a method of determining the presence or absence of defects.

[0006]

However, Japanese Patent Application Laid-Open No. 3-9
In the method disclosed in No. 2758, since the sintered body is fixed on the conveyor and is hit with an impact tool from above, the impact force is regulated and absorbed by the conveyor surface, and an appropriate impact sound cannot be obtained. It is difficult to determine the presence or absence. Therefore, it is an object of the present invention to provide a sound selection method capable of obtaining a proper sound without fixing a sintered body and determining whether the sound is good or bad by the sound. Another object of the present invention is to provide an acoustic selection device capable of discriminating its quality from the resonance sound of a sintered body by a simple operation.

[0007]

A first aspect of the present invention is an acoustic selection method in which a sintered body of a metal oxide is dropped on a resonance table, and the quality of the sintered body is determined from the resonance sound obtained. Second
In the invention, the drop means for dropping the inspection object on the resonance table, the detection means for detecting the resonance sound of the inspection object and the resonance table, and the conversion means for converting the output signal of the detection means into an acoustic waveform, It is an acoustic sorting device that has a computing unit that finds the sound intensity and the degree of attenuation of an acoustic waveform, and compares these measured values with a reference value, and a sorting unit that sorts non-defective and defective products of the inspection object.

The present invention is particularly suitable for determining the quality of a ferrite magnet. When the ferrite magnet is dropped to generate a resonance sound, it is desirable to drop it from a height of 50 mm or less. If the ferrite magnet is dropped from a height exceeding 50 mm, the ferrite magnet may crack.

Further, the shape of the ferrite magnet is preferably an arc segment shape as shown in FIG. 2. When the arc angle θ is 80 ° or more, a larger resonance sound can be obtained and the quality can be easily determined. It can be carried out. Further, when a fall impact is applied to the back portion 7a of the arc segment-shaped ferrite magnet, a large resonance sound is obtained. Therefore, it is desirable to impact the back of the arc segment shaped ferrite magnet with an arc angle of 80 ° or more. In addition, even a hollow cylindrical ferrite magnet is likely to generate a large resonance sound, and acoustic selection can be easily performed.

Further, when a ferrite magnet in the shape of an arc segment is dropped on the resonance table, it is desirable to drop it so that its back part hits because it is easily broken by a drop impact if it hits at a point.

[0011]

According to the present invention, since the resonance sound is obtained by dropping the sintered body on the resonance table, the resonance sound can be obtained without fixing the sintered body when the resonance sound is generated. Therefore, an appropriate sound can be obtained without the resonance sound being absorbed by the fixing member. INDUSTRIAL APPLICABILITY The present invention is a method of applying a drop impact to a ferrite magnet and determining the quality based on the resonance sound caused by the impact, so that the surface of the magnet is not contaminated with a chemical or the like and can be determined in a short time. Is. Further, since the discrimination is performed by the resonance sound, it is possible to discriminate even if the microcracks exist inside the magnet.

[0012]

【Example】

(Embodiment 1) FIG. 1 is a sectional view showing an embodiment of an acoustic sorting apparatus for ferrite magnets using the acoustic sorting method of the present invention.

In FIG. 1, reference numeral 1 is a supply conveyor for conveying an arc segment-shaped sintered body 7 as shown in FIG. 2 in the direction of arrow A. Reference numeral 2 denotes a rotating device that moves up and down from above the supply conveyor 1 to change the direction of the sintered body to a measurement posture, and is attached to a column 3 installed on the installation table 10. Reference numeral 4 denotes a dropping device for dropping the sintered body on a stainless steel resonance table 6, which has a hand 5 for gripping the sintered body and is fixed to a cylinder 42. The cylinder 42 is supported on an arm 41 that is movably mounted on the support column 3 and operates left and right (direction of arrow X).
The column 3 has a movable arm 31 and is vertically (arrow Y).
Direction). Due to the mutual operation of the cylinder 42, the arm 42, the support column 3 and the arm 31, the drop device 4 is
Operates vertically and horizontally. Reference numeral 8 denotes a defective product discharge shutter that can be opened and closed, and does not operate when the sintered body is a good product, and is opened when it is a defective product. Reference numeral 9 is a discharge conveyor that conveys non-defective products. 13 is a case for storing non-defective products.

Reference numeral 15 denotes a detection unit, which detects a resonance sound when the sintered body is dropped by a microphone (not shown). The detected resonance sound is amplified by the amplifier 16 to an appropriate voltage value, the strength of the amplified signal is calculated, the attenuation is calculated from the amplitude time and the amplitude area, and compared with each prestored reference value of a good product. Then, the judgment is performed by the judgment device 17 which performs processing for judging the quality of the sintered body. The reference value of a non-defective product can be obtained by comparison with a sensory inspection method, a destructive inspection method, or the like.

In the above construction, the sintered body 7 is conveyed by the supply conveyor 1 and is changed to the measuring posture by the rotating device 2. The hand 5 moves to the column 3 side as shown by the arrow B, descends to sandwich the sintered body, and then ascends as shown by the arrow C to move above the resonance table 6 and then resonates the sintered body. The table 6 is dropped from a height of 20 mm. The resonance sound between the resonance table 6 and the sintered body generated at the time of dropping is detected by a microphone provided in the detector 15, the resonance sound is amplified by the amplifier 16, and the strength and attenuation of the signal are compared with the reference value. Then, the judging device 17 judges pass / fail. The sintered body after the determination is discharged by a scraper (not shown), and at the same time, if the defective discharge shutter 8 is defective, it operates. On the other hand, if the sintered body is a good product, it slides on the defective discharge shutter 8, moves onto the discharge conveyor 9, and is transferred into the case 13 via the guide plate 12.

(Experimental Example 1) FIG. 3 shows the result of measuring the resonance sound of an arc segment-shaped ferrite magnet having an arc angle θ = 145 ° and a thickness of 5.5 mm with an oscilloscope. 3A is a good product and FIG. 3B is a bad product. A good product has large amplitude and lasts for a long time (small attenuation), whereas a bad product has small amplitude and lasts only for a short time. It can be seen that there is no (high attenuation).

(Experimental Example 2) A ferrite magnet having an arc angle θ of 140 ° and an arc segment shape with a thickness of 5.93 mm was selected. When 100 ferrite magnets were prepared and the quality of the ferrite magnets was determined by color check, 3 defects were found. The remaining 97 discriminated as non-defective products were subjected to a pass / fail determination using the ferrite magnet acoustic sorting apparatus of the present invention shown in FIG. 1, and two more defects were found. The reliability of products can be further improved by the acoustic selection method for ferrite magnets of the present invention.

[0018]

According to the acoustic selection method and the acoustic selection device for a ferrite magnet of the present invention, it is possible to accurately determine the quality of a sintered body.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an acoustic discrimination device of the present invention.

FIG. 2 is a perspective view showing an example of a ferrite magnet to which the present invention is applied.

FIG. 3A is a diagram showing a waveform representing a resonance sound of a ferrite magnet without a crack and a resonance table. (B) It is a figure which shows the waveform showing the resonance sound of the ferrite magnet with a crack, and a resonance stand.

[Explanation of symbols]

1 supply conveyor, 2 rotating devices, 3 columns,
4 drop device, 5 hands, 6 resonance table, 8 defective discharge shutter, 9 discharge conveyor 15 detector, 16 amplifier, 17 determination device

Claims (2)

[Claims] 1. An acoustic selection method, wherein a sintered body of a metal oxide is dropped on a resonance table, and the quality of the sintered body is determined from the resonance sound obtained. 2. Drop means for dropping the inspection object on the resonance table, detection means for detecting resonance sound between the inspection object and the resonance table, and conversion means for converting an output signal of the detection means into an acoustic waveform. , Sound intensity and attenuation of acoustic waveform, and a determination means for comparing these measured values with a reference value, and a selection means for selecting a non-defective product and a defective product of the inspected product apparatus.