JPH0213971Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a device that can detect cutting defects at an early stage when forming screw holes by cutting.

For example, the head plate is attached to the reactor pressure vessel body using stud bolts, and screw holes are formed on the vessel body side for attaching the stud bolts. Screw holes are made by cutting a thread groove into the inner circumferential surface of a pre-formed hole using a tap, but if the biting depth and insertion speed are incorrectly set when inserting the tap, so-called "peeling" may occur during cutting. ”, resulting in poor screw hole formation. "Peeling" here refers to the part that should become chips being peeled off from the cutting surface due to the above-mentioned incorrect settings, increasing the surface roughness of the cutting surface, and causing inaccurate cutting. It means becoming.
Until now, there has been no effective means of detecting this "peeling" during screw hole machining, and methods such as having workers listen for abnormal noises with a listening rod while working have been attempted, but The reality is that there is little hope of discovering ``peeling'' during work because the occurrence is so subtle.

The purpose of this invention is to provide a device that can detect the "peeling" phenomenon at an early stage in view of the above-mentioned problems.

In short, this idea consists of an AE sensor that measures the amplitude and frequency of elastic waves emitted when cutting a screw into the inner peripheral wall of a hole, and a judgment that determines whether "peeling" has occurred based on the amplitude and frequency values from this AE sensor. The present invention is characterized in that it is a screw part defect detection device comprising a display part that displays parts and determination results thereof.

Examples of this invention will be described below.

In Fig. 1, 1 is a base material made of steel etc., 7
is a hole formed in this base material, and a screw 2 is cut and formed on the inner peripheral surface of this hole 7 using a tap (not shown). 3 is the AE sensor placed near this hole 7,
4 is a preamplifier that amplifies the elastic wave signal detected by the sensor 3, and 5 is a determining unit that inputs the signal from the preamplifier 4 and determines whether or not "peeling" has occurred (the method for determining this will be described later). ), 6 is a recorder that records changes in the detected elastic waves.
Further, 7 is an alarm device that issues an alarm when "peeling" occurs. Note that this recorder and alarm are referred to as a display section.

In this device, elastic waves generated by screw hole machining are detected by an AE sensor 3, amplified by a preamplifier 4, and then input to a determining section 5. The determining unit 5 detects the presence or absence of "peeling" based on the input signal. Specifically, when the screw hole forming process is performed normally, if the base material 1 is steel, the friction between the steel material and the tap cutting edge will cause
Elastic waves with a frequency of 500KHz are generated continuously.
Figure 2a shows this frequency spectrum. On the other hand, when "peeling" occurs, elastic waves with a frequency of 50 to 1000 KHz are generated intermittently, and an "abnormal sound" that is clearly different from normal is emitted, indicating that "peeling" has occurred. Detect. FIG. 2b shows a frequency spectrum when "plucking" occurs. In other words, as is clear from both spectra, whether or not an elastic wave with a frequency of 500 KHz or higher is generated is a measure of whether or not "peeling" occurs. If "peeling" occurs, the determining section 5 issues a signal to the alarm 7, and the operator is notified of the occurrence of "peeling" by this alarm.

FIG. 3 shows another detection method. In other words, during normal times when no "peeling" occurs, elastic waves are generated regularly, and the total number of times (total counts) increases almost linearly in proportion to time, as shown in the graph shown in Figure 3a. . On the other hand, when "peeling" occurs, the number of occurrences of elastic waves increases rapidly, and the total count increases rapidly as shown in the graph in FIG. The occurrence of "peeling" is detected by a sudden increase in the number of occurrences of elastic waves.

By implementing this invention, the phenomenon of "peeling", which was previously almost impossible to detect during machining, can be easily detected, thereby increasing the accuracy of screw hole machining.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of the detection device according to this invention, Fig. 2 is a diagram showing the relationship between the amplitude and frequency of elastic waves,
FIG. 3 is a diagram showing the total count number of elastic waves. 1... Base material, 2... Screw, 3... AE sensor,
5... Judgment unit, 6... Counter, 7... Alarm device.

Claims (1)

[Scope of claim for utility model registration] 1. AE sensor that measures the amplitude and frequency of elastic waves emitted when cutting and forming a screw on the inner peripheral wall of a hole;
A thread defect detection device characterized by comprising a determination unit that determines the occurrence of “peeling” based on the amplitude and frequency values from the AE sensor, and a display unit that displays the determination result. 2. The threaded part defect detection device according to claim 1, characterized in that an alarm is circuit-connected to the determination section. 3. The threaded part defect detection device according to claim 1, characterized in that a recorder is circuit-connected to the determination section.