JPS6039523A - Detecting method of looseness in fastening part - Google Patents

Abstract

PURPOSE:To detect easily and exactly a looseness by interposing a washer member between a bolt, etc. and a member to be clamped, and taking it out as electric information to the outside, in case when the bolt, etc. are loosened. CONSTITUTION:A clearance bolt inserting hole 5 is provided on the center part of a seat plate 1 divided into two pieces of seat plates 1a, 1b, and a dielectric ceramics element 4 is formed projectingly on four places in a groove 41. Also, a ring 7 consisting of a ring-like insulating material, and the same ring-like piezoelectric element 6a are provided so as to be recessed along the clearance hole 5 and its upper face, respectively. The dielectric ceramics element 4 and the piezoelectric element 6a are connected to an external measuring instrument, etc. through the groove 41. That which is formed in this way is clamped by a bolt, and in case when it is loosened, the pressure is varied, and a polarization and a mechanical distortion are generated in the piezoelectric element 6a. When a value of an induction flux density is detected by an operation, its varied portion can be detected exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides that when fixing a fixing member such as a bolt to a member to be fastened, the bolt or the like is used as a detection medium or a washer is interposed,
The present invention relates to a method for detecting loosening of a fastening portion, using the washer member as a detection medium and detecting a loosening signal from the washer member to detect loosening.

Originally, when configuring various devices in industrial products, it was done by joining together two or more parts and combining many parts, and in particular, it was possible to connect and remove with simple tools, and it was possible to do it many times. Since it has many features such as being able to be used repeatedly, bolts are generally used as fixing members. Since the fastening part uses screws, it is bound to loosen.

If these tightenings loosen excessively, as some devices involve high-speed rotation and high pressure, this loosening will gradually expand, causing
Eventually, the fastened parts become separated, causing serious inconveniences such as failure or destruction of the device, serious personal injury, and great economic loss.

For this reason, conventional methods to deal with these problems include using special washers such as lock nuts, spring washers, chrysanthemum-shaped washers, etc., and tightening screws with adhesives such as screw locks on the threaded parts. However, it is not satisfactory due to changes over time and usage conditions.

In view of these, various methods of detecting looseness of the catch are being used.

In other words, there are visual methods in which cracks in paint applied to bolts or nuts are visually observed, and auditory methods in which an expert can hear the changes in the nature of the sound when they hit a fastening part with a hammer. Since these methods are done manually, there are individual differences, and it is impossible to use the above methods especially when the bolt is in a closed container or in a narrow place.

Therefore, attempts have been made to analyze signals from resistance wire strain gauges attached to bolts and select signals that correspond to minute elongations of the bolts, but these methods also yield inaccurate results. It has not yet been put into practical use because it requires a large amount of labor and equipment costs.

Therefore, in order to overcome the above-mentioned problems of the conventional art, the present invention forms a loosening detection mechanism that has a function of accurately detecting loosening of bolts, etc., and if this mechanism becomes loose, an electrical or By taking it out as mechanical information, etc.
Anyone can easily and reliably detect loosening even at a distance from bolts, etc., regardless of skill level, and the process of loosening can be recorded and detected even in locations where bolts, etc. cannot be seen directly, saving manpower. The purpose of this invention is to provide a method for detecting loosening of fasteners that can reduce costs and equipment costs and serve as a safety measure.

That is, the gist of the present invention resides in a method for detecting loosening of a fastened portion, which detects loosening of a fastened member by fastening a fastened member such as a bolt and detecting the loosening of the fastened member. .

Hereinafter, in order to further clarify the gist of the present invention described above,
An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram for explaining the detection principle. In the figure, 1 is a washer member, 2 is a nut, and 3 is a bolt shaft. When the bolt 8 is tightened in this state, as shown in FIGS. As shown in b), stress acts on both end faces of the washer member 1, respectively.

At this time, dr xdz which is a minute element of washer member 1
A stress 6o acts on X rdφ, and the compressive strain εO is expressed by the following relational expression.

However, E=modulus of elasticity (Young's modulus) of the washer member PO: compressive force when the bolt is initially tightened 8: contact area between the bolt head and the washer member C: proportionality constant.

In the above relational expression, when the bolt loosens, Fo decreases by ΔP, strain εO decreases by ΔP Δε−·C·min, and the washer member recovers elastically.

The amount of recovery Δt is approximately between the upper and lower surfaces of the washer member. becomes. However, to is the original thickness of the washer member.

As shown in the above formula, the washer member having a detection function needs to be able to detect Δε or Δt in the formula.

An embodiment of a washer member invented based on the above detection principle will be described.

8 and 4 are schematic diagrams, and 1 in the figure is a washer member, which is divided into two seat plates 1a and Ib, and is provided in the center of these for bolt insertion. Along the hole 5, dielectric ceramic elements 4 are protruded at four locations in a groove 41 provided around the abutment surface of the seat plate 1a, and further abut on the seat plate 1a. A ring 7 made of a ring-shaped insulating material is recessed along the hole 5 in the surface and is insulated from the metal seat plate 1b, and a ring-shaped piezoelectric element 6a is also recessed in the upper surface of the ring 7, which is connected to the dielectric material. Ceramic element 4・
It is formed so that it can come into contact with...

Further, the dielectric ceramic element 4 and the piezoelectric element 6a are connected to an external measuring device (not shown) through the groove 41.

When the thus formed device is fastened with bolts and loosens, polarization P and force Mffiem occur in the piezoelectric element 6a where Δt occurs (pressure change). If vttm is short-circuited, the following relationship generally holds true.

D=P =qTm em = - However, Tm; li Mechanical stress D: Dielectric flux density E: Young's modulus q: Piezoelectric coefficient If the above values are detected, the change can be accurately calculated as a polar ratio.

Further, even if a load cell using a semiconductor pressure sensitive element or a semiconductor strain gauge is used instead of the dielectric ceramic element, the operating principle will be substantially the same as described above.

Next, another embodiment will be described with reference to FIG.

Along the hole 5, groove 4 is placed on the lower surface of the seat plate IC in the same manner as above.
1 is provided around the circumference of the seat plate 1d, and a ring 7 made of an insulating material made of ring clover is recessed in the same manner as described above on the upper surface of the seat plate 1d which comes into contact with the seat plate 1d, and is insulated from the seat plate 1d of the metal plate. Similarly, ring metal plates 6b are provided with their upper surfaces flush with each other, and are in contact with each other to constitute the washer member 1.

The washer member 1 configured in this manner utilizes the change in capacitance that occurs between the seat plate IC and the metal plate 6b, and the warpage is expressed by the following general formula.

0゜=i culm However, CO: Capacitance A: Opposing area d: Distance between opposing areas 0: Dielectric constant If one oscillation circuit is formed with this Co and inductance, it will be easier to oppose each other due to changes in the oscillation frequency. Changes in distance md can be detected.

In the embodiment described above, the quantitative change in elastic recovery of the washer member 1 as the fastened portion of the bolt loosens is measured, but in reality, such a recovery amount is used to check the fastening. In many cases, it is not necessary to know the degree of loosening, and there are cases where it is only necessary to know whether it is tight or loose.

An embodiment in this case will be described with reference to FIG.

FIG. 6 is a sectional view of a main part corresponding to FIG. 5, and the washer member 11 is composed of metal seat plates 11a and 11b, and the seat plate 11a has a □ "seat plate 1a."

A groove 41 is recessed along the hole 5 as shown in Ic, and an electrode 18 is provided in the groove through a bottomed cylindrical body 12 made of an electrically insulating material. A protruding body 14 is integrally protruded toward the seat plate 11. b
A plurality of them are arranged so as to come into contact with any arbitrary part of the .

When the washer member 11 configured in this manner is inserted into a bolt and fastened, the protrusion 14 presses against the seat plate 11b disposed below the protrusion 14 as an electrode. When the bolt is loosened, the washer member 11 recovers elastically and the protruding body 14 is separated from the seat plate 1'1b, which can be easily identified by connecting and wiring to a tester or lamp (not shown).

According to this embodiment, since the electric circuit is turned on and off in accordance with the fastening state of the bolt, the exclusive state of the circuit can be easily detected using a simple tester or lamp display. Moreover, it can be detected at a remote location.

Next, FIG. 7 shows another embodiment, in which a washer member 15 made of laminated conductive rubber or carbon fiber cloth is used instead of the electrode of the washer member to connect the fastened member r and the bolt 8. The function of this structure is to simply change the resistance value of the member by utilizing the fact that when the washer member 15 is compressed by fastening, the electrical resistance changes. The fastening state can be detected by measuring changes in the fastening state.

Furthermore, FIGS. 8(a) and 8(b) show another embodiment in which a conductive, ultra-thin plate-like comb-shaped electrode 2o coated with dielectric ceramics 21 is attached to the A, which is interposed between the part and the member to be fastened or the washer, is connected to the Oi source 22, and is equipped with a frequency detector 23, so that the detected frequency changes due to the stress applied to the ceramic. This method is used to detect looseness by utilizing

Next, FIG. 9 shows still another embodiment,
A short evaporated fluid 80 is sealed in the hole provided in the bolt via a semiconductor pressure sensitive element 81, and this fixes the fastened member, and if the bolt becomes loose, the fluid due to the distortion of the bolt itself will be removed. A pressure change of 3o is applied to the semiconductor pressure sensitive element 8.
1 to detect looseness.

Next, FIG. 10 shows an embodiment of detection using a mechanical method, in which a shaft 50 is provided in a fitting hole penetrating a bolt, and a flange portion and a plug fixed to the bolt are provided. A coil spring 51 is interposed between the shafts 52 and 52 to urge the shaft 50 to project downward at all times, and the upper end of the shaft 50 is connected to a pressure gauge (not shown), as shown in FIG. In this method, the bolt is screwed into a threaded hole provided in a fixing member that fixes the member to be fastened, and the fluctuation of the shaft 50 when the bolt loosens is detected using the pressure gauge to detect loosening.

In addition, the structure of the washer member in each of the above embodiments is an example, and the looseness detection method is also an example, and a bolt is shown as an example of a fixing member, and the same purpose is shown. The specific method and structure may be arbitrarily determined within the scope of achieving the above-mentioned objects, functions, and effects of the present invention, and these changes do not change the gist of the present invention in any way. As explained above, the present invention provides a washer member that has a function of detecting loosening of a bolt or the like when fixing the bolt or the like to a member to be fastened. There is no need to insert this between the bolt, etc. and the member to be fastened, and if the bolt, etc. becomes loose, it can be extracted externally as electrical information, so that it can be used even in a remote place by a skilled worker. Anyone can easily and accurately detect loosening, regardless of whether it is present or not, and it can be used to detect bolts and other fixed parts that cannot be seen directly in various fasteners on airplanes, bolts for attaching them to the exterior walls of submarines, and vibrations and temperature changes in machine tools. It is possible to record and detect the loosening process of fasteners, bolts in high-speed, high-rotation objects, etc., which is a safety measure, reduces labor and equipment costs, and is highly reliable in detecting loosening of fasteners. It is said that the above-mentioned problems that occurred in the conventional method of detecting looseness of fasteners are extremely effectively solved, and the practical benefits brought about by the present invention are extremely large. I have no choice but to.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is an explanatory diagram schematically illustrating the detection principle of the present invention, and FIG.
Figure (A) is a cross-sectional view taken along line A-A in Figure 1, Figure 2 (B) is a cross-sectional view taken along line 13-B in Figure 11, Figure 3 is a longitudinal cross-sectional view of the washer member, and Figure 4 is a cross-sectional view taken along line 13-B in Figure 11. 3 is a view taken along line C-C in FIG. 3, FIG. 5 is a sectional view of the main part of FIG. 4, FIG. 6 is a sectional view of the main part showing another embodiment, and FIG. Front view, Figure 8 (a)
is a plan view of another embodiment, FIG. 8(b) is an explanatory diagram of its usage state, and FIG. 9 is a partially cutaway vertical sectional view showing another embodiment.
FIG. 10 is a longitudinal sectional view showing another embodiment. 1.11.15---One washer member, 20---<L-shaped electrode, 30-One fluid, 31-One semiconductor pressure-sensitive element, 50-One axis, 51--Coil spring. Patent applicant Yawata Iron Works Co., Ltd. Figure 1

Claims (1)

[Claims] A method for detecting loosening of a fastening part, which comprises fixing a member to be fastened with a fastening member such as a bolt, and then detecting the loosening when the fastened member becomes loose.