WO2024014036A1

WO2024014036A1 - Bolt with looseness sensor, method for using same, and looseness detection system

Info

Publication number: WO2024014036A1
Application number: PCT/JP2023/007315
Authority: WO
Inventors: 芳隆秋野
Original assignee: 芳隆秋野
Priority date: 2022-07-11
Filing date: 2023-02-28
Publication date: 2024-01-18
Also published as: JP2024009615A; JP7249702B1

Abstract

Provided is a bolt 10 with a looseness sensor, which can easily be attached to a structure and with which looseness of the bolt can be reliably detected. The bolt includes a male thread portion 12a and a head portion 14, and is provided with a deep hole 16 bored in the direction of a central axis C of a bolt main body 12. A pin 20 is provided in the deep hole 16, one end portion of the pin being fixed to a bottom portion of the deep hole 16, and the remainder excluding the fixed end portion not being restrained by an inner circumferential surface of the deep hole 16. The bolt is provided with a contact sensor 22 which is fixed to the head portion 14 of the bolt main body 12, and which is provided so as to be capable of moving toward and away from the other end portion of the pin 20 by means of an axial force acting on the male thread portion 12a. If the axial force acting in the axial direction on the bolt main body 12 decreases as a result of loosening of the bolt main body 12, causing the male thread portion 12a of the bolt main body 12 to contract, the contact sensor 22 outputs a loosening detection signal indicating that a contacting end portion 24 of the contact sensor 22 has changed from a state of being separated from the other end portion of the pin 20 to a state of contact therewith.

Description

Bolts with looseness sensors, how to use them, and looseness detection systems

The present invention relates to a bolt with a loosening sensor equipped with a sensor for detecting loosening of bolts fastened to various structures, a method of using the same, and a loosening detection system.

Bolts that connect members of infrastructure structures such as tunnels and bridges, as well as other various connected objects, loosen over time and require periodic inspection. In addition, problems such as accidents have occurred due to loosening of bolts. Therefore, various sensor bolts have been proposed to detect the loosening of bolts.

In the sensor bolt disclosed in Patent Document 1, a strain sensor for detecting strain is inserted and fixed into a deep hole drilled in the axial direction from the head of the bolt. Furthermore, it amplifies the output of the strain sensor housed in the bolt head, compares the strain sensor output with a preset value, and sends out an output when the strain sensor output is lower than the set value at least after bolt tightening. It is equipped with an amplifier fixed to the head of the bolt and an indicator that displays the output from the amplifier to indicate that the bolt has loosened.

The bolt with a strain measurement function disclosed in Patent Document 2 has a Wheatstone bridge circuit consisting of a strain sensor and a dummy resistor inside the shaft of the bolt, and a conversion circuit that amplifies the signal from this Wheatstone bridge circuit and converts it into a digital signal. A strain sensor and a dummy resistor that constitute a Wheatstone bridge circuit, including a transmission circuit for transmitting a digital signal to the outside of the bolt, and a power supply circuit that supplies electromagnetic wave energy received from outside the bolt as a power source for the circuit. are formed on the same silicon single crystal member surface.

The bolt axial force measuring device disclosed in Patent Document 3 is a bolt axial force measuring device that measures the axial force of the bolt based on the propagation time of the ultrasonic wave propagating inside the bolt, and is a bolt axial force measuring device that measures the axial force of the bolt based on the propagation time of the ultrasonic wave propagating inside the bolt. and a measurement point detection section that detects a measurement point from within the waveform of the reflected wave. Furthermore, there is a propagation time measurement section that measures the propagation time of the ultrasonic wave within the bolt based on the time difference between different measurement points based on the measurement points detected from within each waveform of the reflected waves obtained multiple times, and a temperature measurement section. a correction coefficient calculation unit that calculates a propagation time correction coefficient that reflects the temperature dependence of the ultrasonic propagation velocity in the bolt, based on the temperature of the bolt at the time of the actual measurement measured by the means; and the actually measured propagation time. and a propagation time correction section that calculates a propagation time after temperature correction based on the calculated correction coefficient.

Japanese Patent Application Publication No. 11-118637 Patent No. 4329477 Japanese Patent Application Publication No. 2010-216804

The sensor bolt disclosed in Patent Document 1 is equipped with a strain sensor in a deep hole in the axial direction of the bolt, as well as an amplifier and an indicator in the bolt head, and has many electronic components attached to the bolt and has a complicated structure. It is. The bolt with a strain measurement function disclosed in Patent Document 2 also has a sensor device made of a silicon single crystal member attached to the bolt, and has a complicated structure and is expensive. The bolt axial force measuring device disclosed in Patent Document 3 measures ultrasonic waves propagating inside the bolt, and the peripheral equipment is complicated, the method of use is troublesome, and the cost is high.

The present invention has been made in view of the above-mentioned background art, and has a simple structure, is easy to attach to a structure, and has a bolt with a loosening sensor that can reliably detect bolt loosening, and a method for using the same. and a looseness detection system.

The present invention provides a bolt body having a male threaded portion and a head, and a deep hole drilled in the central axis direction of the male threaded portion; A pin other than a part of the pin is not restrained by the inner peripheral surface of the deep hole, and a sensor is provided that is fixed to the bolt body and is capable of detecting the pin based on a change in the axial force applied to the male thread part, and when in use, , Due to the loosening of the bolt body, the axial force applied in the direction of the central axis of the bolt body decreases, and the male threaded portion of the bolt body contracts, and the sensor moves from a separated state to a predetermined position with respect to the pin. Alternatively, the sensor is a bolt with a loosening sensor that outputs a loosening detection signal when the contact state is reached.

One end of the pin is fixed to the bottom of the deep hole, and the sensor is fixed to the head of the bolt body, and is capable of detecting the other end of the pin by an axial force applied to the male thread. When the bolt body is loosened, the axial force applied in the axial direction of the bolt body decreases, and the end of the sensor moves from the separated state to a predetermined position with respect to the other end of the pin. The sensor outputs a looseness detection signal when the sensor comes close to or comes into contact with.

The deep hole communicates from the head of the bolt body to the male threaded portion of the bolt body, and a female threaded portion to which the sensor is fixed is formed in the head of the bolt body. Furthermore, the sensor may be fixed to the head portion of the bolt body in a watertight manner through a sealing member in the female threaded portion of the bolt body.

The sensor is preferably a contact sensor that detects the pin by coming into contact with the other end of the pin, but may be a non-contact sensor that provides desired detection accuracy.

The present invention also provides a bolt body having a male threaded portion and a head, and a deep hole drilled in the central axis direction of the male threaded portion; Looseness comprising a pin that is not restrained by the inner circumferential surface of the deep hole except for the part described above, and a sensor that is fixed to the bolt body and is provided to be able to detect the pin based on a change in the axial force applied to the male threaded part. Using a bolt with a sensor,
The bolt body is attached to the object to be fastened together with a female threaded member of the object to be fastened, and the male threaded portion of the bolt main body is rotated relative to the female threaded member, and the male threaded portion of the bolt body is rotated relative to the female threaded member. The bolt body is fastened with a predetermined tightening force, and the sensor detects the pin,
Thereafter, the sensor is moved at a predetermined interval corresponding to an allowable amount of shrinkage in the case where the axial force of the male threaded portion decreases due to loosening of the bolt body attached to the object to be fastened, and the male threaded portion shrinks. fixing the sensor to the head of the bolt body in a non-detecting state while separating from the pin;
In use, when the fastening state of the bolt body becomes loose and the amount of shrinkage of the bolt body reaches the allowable amount of shrinkage, the pin changes from the non-detecting state to the detecting state with respect to the sensor, and the pin moves from the non-detecting state to the detecting state, and This is a method of using a bolt with a looseness sensor that outputs a looseness detection signal.

One end of the pin is fixed to the bottom of the deep hole, and the sensor is fixed to the head of the bolt body, and is capable of detecting the other end of the pin by an axial force applied to the male thread. provided, the deep hole communicates from the head of the bolt body into the male threaded part of the bolt body, and a female threaded part to which the sensor is fixed is formed in the head of the bolt body, When separating the end of the sensor from the other end of the pin, the sensor is rotated by a predetermined angle around the axis of the bolt body to separate the predetermined distance corresponding to the allowable shrinkage amount. It is.

The sensor is a contact sensor that detects the pin by contacting the other end of the pin, and when the bolt body is fastened with a predetermined tightening force to the object to be fastened, the sensor A contact end is in contact with the other end of the pin,
Thereafter, the contact end is separated from the other end of the pin by the predetermined distance corresponding to the allowable shrinkage amount, and the contact sensor is fixed to the head of the bolt body;
In use, when the fastened state of the bolt body becomes loose and the amount of shrinkage of the bolt body reaches the allowable amount of shrinkage, the other end of the pin separates from the contact end of the contact sensor. The state changes from the state to the contact state, and the sensor outputs a loosening detection signal.

The present invention also provides a bolt body having a male threaded portion and a head, and a deep hole drilled in the central axis direction of the male threaded portion; Looseness comprising a pin that is not restrained by the inner circumferential surface of the deep hole except for the part mentioned above, and a sensor fixed to the bolt body and provided to be able to detect the pin based on a change in the axial force applied to the male threaded part. A bolt with a sensor is provided, and a bolt with a sensor is provided.
A display indicating that the bolt body is loosened by receiving a loosening detection signal from the sensor when the bolt with the loosening sensor is attached to the object to be fastened together with a female threaded member of the object to be fastened. Equipped with equipment,
In use, when the fastened state of the bolt body becomes loose and the amount of shrinkage of the bolt body reaches a predetermined allowable amount of shrinkage, the sensor changes from a non-detecting state to a detecting state with respect to the pin; This is a loosening detection system in which a sensor outputs a loosening detection signal, and the display device displays the loosening of the bolt body.

The pin has one end fixed to the bottom of the deep hole, and the sensor is a contact sensor that detects the pin by contacting the other end of the pin, and the sensor is fixed to the head of the bolt body. and is provided so that the other end of the pin can be detected by an axial force applied to the male threaded portion,
In use, when the fastening state of the bolt body becomes loose and the amount of shrinkage of the bolt body reaches the allowable amount of shrinkage, the other end of the pin is separated from the contact end of the contact sensor. The contact sensor then outputs a loosening detection signal, and the display device displays the loosening of the bolt body.

According to the bolt with a loosening sensor, its method of use, and the loosening detection system of the present invention, it has a simple configuration, is easy to attach to a structure, and can reliably detect bolt loosening. Furthermore, the detection accuracy of bolt loosening is high, and loosening of bolts can be reliably detected and notified to the outside, and the safety and fastening stability of the structure to be fastened can be easily improved.

FIG. 2 is a sectional view showing a bolt with a loosening sensor according to a first embodiment of the present invention. It is a front view showing the pin of the bolt with the loosening sensor of the first embodiment. It is a front view showing the contact sensor of the bolt with the loosening sensor of the first embodiment. They are a vertical cross-sectional view (a), an AA cross-sectional view (b), and a BB cross-sectional view (c) showing the usage state of the bolt with the loosening sensor of the first embodiment. FIG. 3 is a partially enlarged vertical cross-sectional view showing a state in which the bolt with a loosening sensor of the first embodiment is used. FIG. 3 is a longitudinal cross-sectional view showing a loosening detection state of the bolt with a loosening sensor according to the first embodiment. FIG. 3 is a partially enlarged vertical cross-sectional view showing a loosening detection state of the bolt with a loosening sensor according to the first embodiment. It is a graph showing the relationship between the axial force T, which is the axial tension of the bolt with the loosening sensor of the first embodiment, and the axial elongation amount D of the male threaded portion of the bolt. FIG. 3 is a partially enlarged vertical cross-sectional view showing the movement of the loosening sensor-equipped bolt of the first embodiment; FIG. 7 is a longitudinal cross-sectional view showing another state of use of the bolt with a loosening sensor according to the first embodiment. FIG. 1 is a schematic diagram showing a loosening detection system using a bolt with a loosening sensor according to a first embodiment. It is a sectional view showing a bolt with a loosening sensor of a second embodiment of the present invention. It is a front view which shows the contact sensor of the bolt with a looseness sensor of 2nd embodiment. They are a vertical sectional view (a), a CC sectional view (b), and a DD sectional view (c) showing the usage state of the bolt with a loosening sensor of the second embodiment. FIG. 7 is a partially enlarged vertical cross-sectional view showing the state in which the bolt with the loosening sensor of the second embodiment is used.

Hereinafter, a first embodiment of a bolt with a loosening sensor of the present invention will be described based on FIGS. 1 to 8. As shown in FIG. 1, the bolt 10 with a loosening sensor of this embodiment includes a bolt body 12 consisting of a male threaded portion 12a and a head 14. The male threaded portion 12a has a cylindrical shaft portion formed with a male thread. A deep hole 16 is drilled from the top surface 14a of the head 14 in the direction of the central axis C of the shaft portion of the male screw portion 12a, and a contact sensor 22, which will be described later, is inserted and fixed in the deep hole 16.

The deep hole 16 is formed over about 1/3 of the length from the head 14 of the bolt body 12 to the head 14 side of the male threaded portion 12a of the bolt body 12, and the bottom of the deep hole 16 has an inner diameter. A small diameter portion 16a is formed with a slightly smaller diameter. The small diameter portion 16a is formed to have a short length into which a tip 20a of a pin 20, which will be described later, can be fitted and held and fixed. The deep hole 16 other than the small diameter portion 16a to which the pin 20 is fixed has an inner diameter slightly larger than the small diameter portion 16a, and is formed to a diameter that does not allow the pin 20 to come into contact with the inner peripheral surface of the deep hole 16 and prevent the pin 20 from being restrained. ing.

The deep hole 16 in the head 14 of the bolt body 12 is formed with a female screw portion 16b in which the inner diameter of the deep hole 16 becomes larger and opens at the top surface 14a, and the contact sensor 22 is fixed thereto. There is. The length of the female screw portion 16b in the direction of the central axis C is slightly shorter than the length of the head 14 in the direction of the central axis C. That is, as shown in FIG. 1, the end surface 16c on which the female threaded portion 16b is formed is located closer to the top surface 14a by a slight distance _L1 in the direction of the central axis C than the back surface 14b of the head 14 of the bolt body 12. It is located in

The pin 20 provided in the deep hole 16 of the bolt body 12 is a cylindrical metal rod, as shown in FIG. The corner of the tip 20a of the pin 20 is chamfered, and the base end surface 20b is formed flat. The length P ₀ of the pin 20 is such that when the tip 20a is fixed to the small diameter portion 16a of the deep hole 16, the base end surface 20b slightly protrudes from the end surface 16c of the deep hole 16, and the top surface of the head 14 This is the length located on the 14a side.

As shown in FIG. 3, the contact sensor 22 provided in the deep hole 16 of the bolt body 12 has a cylindrical shape with a male threaded portion 22a that is screwed into the female threaded portion 16b of the head 14 of the bolt body 12. , the tip has a contact end 24 for detecting the state of contact with the pin 20. The contact end 24 electrically detects contact with the opposing member and is provided so as to be slightly protrusive and retractable. The contact sensor 22 is configured so that when the contact end 24 comes into contact with the pin 20, the contacts of the internal circuit electrically open or close, detecting the contact state, and outputting the result from the lead wire 18.

If the mounting screw of the contact sensor 22 loosens over time after installation, the detection accuracy will decrease or detection will become impossible. It is good if a male screw is formed. For example, the thread 23 of the male threaded portion 22a is formed in a wavy manner in the axial direction at a constant period, and the waves of the wavy thread 23 are different from the helical line of a standard screw. It is formed by a periodic wavy curve in which one cycle is a positive and negative cycloid curve. The period of the waves of the thread 23 is, for example, 180° or 120° with respect to 360° around one circumference of the male threaded portion 22a. Threads 23 are formed in a wave shape at regular intervals. The interval between the peaks of the positive and negative waves of one cycle of the thread 23 is wider than the interval of one pitch of the male thread part 22a, and when the thread 23 is screwed into the female thread part 16b, the thread of the male thread part 22a The ridges 23 are formed at intervals that can be elastically deformed and screwed together.

Next, a method of using the bolt 10 with a loosening sensor of this embodiment will be explained. As shown in FIGS. 4 and 5, the bolt 10 with the loosening sensor is fixed by having the tip 20a of the pin 20 press-fitted into the small diameter portion 16a in the deep hole 16 of the bolt body 12. In this state, the

objects

26 and 28 to be fastened are held between the nut 30 and the head 14, and the head 14 integrated with the male threaded portion 12a of the bolt body 12 or the female thread on the side of the

objects

26 and 28 to be fastened is The nut 30, which is a member, is relatively rotated and tightened to be fixed. At this time, the contact sensor 22 may be screwed into the female threaded portion 16b of the deep hole 16, but the contact sensor 22 may be attached after the bolt body 12 is fastened.

The bolt body 12 is tightened with a predetermined tightening torque. At this time, an axial force T, which is a tension, is applied to the male threaded portion 12a of the bolt body 12 in the direction of the central axis C, and the male threaded portion 12a expands in proportion to this axial force T. This relationship is determined by the elastic modulus (Young's modulus) of the male threaded portion 12a, and as shown in FIG. 8, the axial force T (stress) and the elongation D (strain) are in a proportional relationship.

After the

objects

26 and 28 are fastened by the bolt body 12 and the nut 30 with a standard axial force determined by the thickness of the male screw portion 12a of the bolt body 12, etc., the contact sensor 22 is set. The contact sensor 22 is set by tightening the bolt body 12 with a tightening torque that applies a standard axial force to the male threaded portion 12a of the bolt body 12, then screwing the contact sensor 22 into the deep hole 16, and tightening the contact end 24. It is brought into contact with the proximal end surface 20b of the pin 20 inside the bolt body 12. At this time, the screw engagement is stopped at the contact position so that the contact end 24 does not sink into the contact sensor 22 and move, and no pressure is applied to the contact end 24. Note that before tightening the bolt body 12 with the standard axial force of the bolt body 12, the contact sensor 22 is screwed into the deep hole 16, and the contact end 24 is brought into contact with the base end surface 20b of the pin 20 inside the bolt body 12. After that, the bolt body 12 may be fastened with a standard axial force. However, after tightening the bolt body 12 with the standard axial force, the male threaded portion 12a expands by the amount of expansion _D1 , so it is necessary to bring the contact end 24 of the contact sensor 22 into contact with the base end surface 20b of the pin 20 again. There is.

From this state, the contact end 24 of the contact sensor 22 is separated from the base end surface 20b of the pin 20 by a predetermined distance Δd. As shown in FIG. 8, the predetermined interval Δd is determined by the amount of elongation (distortion) D ₀ due to the axial force T ₀ applied to the bolt body 12 when the

objects

26 and 28 are fastened with a predetermined torque. Due to the loosening of the bolt body 12 attached to the

objects

26 and 28 over time, the axial force, which is the tension of the male threaded part 12a, decreases to _T1 , and the male threaded part 12a slightly contracts from the elongation amount _D0 . This value corresponds to the allowable shrinkage amount ΔD when the elongation amount D becomes ₁ . The allowable shrinkage amount ΔD is the shrinkage amount of the male threaded portion 12a of the bolt body 12 due to a decrease in the tightening force, which is allowed by the bolt body 12.

In other words, the predetermined interval Δd is determined by the predetermined axial force at the time of tightening, which decreases due to loosening of the bolt body 12, with respect to a predetermined length _L0 of the male threaded portion 12a in the deep hole 16 shown in FIG. , as shown in FIG. 9, corresponds to the amount of shrinkage of the male threaded portion 12a of the bolt body 12, and is the amount of decrease in elongation of the portion of the male threaded portion 12a that corresponds to the length _L0 , and the length _L0 This is the allowable shrinkage amount for Here, the length _L0 is a portion of the length of the deep hole 16 of the male threaded portion 12a that expands and contracts due to the axial force applied to the male threaded portion 12a, and is press-fitted into the small diameter portion 16a of the deep hole 16. This is the length of the portion that expands and contracts relative to the pin 20. In addition, in the pin 20, as shown in FIG. 5, the tip 20a is fixed to the small diameter portion 16a of the deep hole 16 within the deep hole 16, and the length of the portion not held by the small diameter portion 16a is the length _L0 . This is not related to the expansion and contraction of the bolt body 12. The distance from the back surface 14b of the head 14 of the bolt body 12 to the base end surface 20b of the pin 20 is a portion of the bolt body 12 that does not affect expansion and contraction due to fastening of the bolt body 12.

Therefore, the predetermined interval Δd is the length _L0 of the predetermined portion of the male threaded portion 12a of the bolt body 12 in an unloaded state. is proportional to the allowable shrinkage amount _ΔD when the male thread portion 12a slightly shrinks from the elongation amount _D0 to the elongation amount _D1 as described above, and is proportional to the allowable shrinkage amount ΔD, as shown in FIG. This value is derived from the relationship between stress and strain shown in . Once the predetermined interval Δd is calculated, the tip of the contact end portion 24 of the contact sensor 22 is positioned at a predetermined interval Δd from the base end surface 20b of the pin 20. The position of the tip of the contact end portion 24 is determined by the rotation angle of the contact sensor 22 and the pitch of the male screw portion 22a. Therefore, after determining the predetermined interval Δd, the distance corresponding to the predetermined interval Δd is calculated as the rotation angle of the male screw portion 22a of the contact sensor 22, and the tip position of the contact end portion 24 is positioned.

The parameters that determine the predetermined interval Δd are set based on the thickness of the male threaded portion 12a of the bolt body 12, the value of the length _L0 determined by the deep hole 16 and the pin 20, and the material of the bolt body 12. It is preferable to calculate the predetermined interval Δd by actual measurement in consideration of these parameters, set it as the rotation angle of the contact sensor 22 corresponding to the predetermined interval Δd, and position the contact end portion 24.

In addition, in the use state, if the distance between the fastening objects 26 and 28 is narrow with respect to the length _L0 set by the deep hole 16, as shown in FIG. It is preferable to interpose a spacer such as a washer 32 between the bolts and attach the bolt body 12 to the male threaded portion 12a so that an axial force due to fastening is applied to at least a portion corresponding to the length _L0 .

According to the bolt 10 with a loosening sensor of this embodiment, it has a simple configuration using the contact sensor 22, and can be easily attached to

objects

26, 28 to be fastened, such as structures. The contact sensor 22 detects the loosening of the bolt body 12 due to aging after fixing the fastening objects 26 and 28 with the bolt 10 equipped with a loosening sensor, and detects the shrinkage of the male threaded portion 12a as shown in FIG. The contact between the detection end 24 and the pin 20 allows reliable electrical detection and output of a looseness detection signal. The detection output from the lead wire 18 is an ON/OFF signal indicating whether the contact end 24 has contacted the pin 20 or not, and it is possible to accurately detect whether the loosening of the bolt body 12 has reached the allowable shrinkage amount ΔD. Can be detected. Therefore, loosening of the bolt body 12 can be detected early and management such as retightening can be performed, and the safety and stability of the fastened state of the fastened objects 26 and 28 can be reliably improved.

Next, a loosening detection system 40 using the bolt 10 with a loosening sensor of this embodiment will be explained based on FIG. 11. The bolt 10 with a loosening sensor of this embodiment is used to fasten structures installed in a plurality of factories F1 and F2, and the

objects

26 and 28 to be fastened are fastened and fixed using the bolt 10 with a loosening sensor. . The output of the bolt 10 with a loosening sensor of this embodiment is connected to a parallel wiring 34 connected in parallel to each contact sensor 22, and the parallel wiring 34 indicates that the contact sensor 22 of the bolt 10 with a loosening sensor is turned on. It is connected to a lamp display panel 42. A lamp display panel 42 is provided for each of the devices A and B, and a lamp display panel 44 that lights up when the contact sensor 22 of the bolt 10 with a looseness sensor of either device A or B is turned on. A wireless transmitter 46 for transmitting the display on the

panels

42 and 44 is provided in each factory F1 and F2. The output of the transmitter 46 is output to a display panel 48 and a personal computer 49 located away from the factories F1 and F2, and indicates that the bolt 10 with the loosening sensor is turned on.

According to the loosening detection system 40 using the bolt 10 with a loosening sensor of this embodiment, it is possible to detect loosening with an inexpensive and highly accurate device using the contact sensor 22, and the loosening of the bolt body 10 can be reliably detected and repaired. can do. In addition, the fastening objects 26 and 28 and the bolt 10 with the loosening sensor in the factory can be reliably monitored, making it possible to stably fasten the fastening objects 26 and 28.

Next, a second embodiment of the bolt with a loosening sensor of the present invention will be described based on FIGS. 12 to 15. Here, the same configurations as those in the above embodiment are given the same reference numerals and the description thereof will be omitted. The bolt 50 with a looseness sensor of this embodiment has a waterproof function, and the bolt body 52 has a contact sensor 54 having a watertight structure, which will be described later, fitted onto the top surface 14a of the head 14, as shown in FIG. A cylindrical protrusion 56 is formed. A circular hole 56a is concentrically formed in the protrusion 56, and the circular hole 56a has an inner diameter larger than that of the female threaded portion 16b of the deep hole 16.

As shown in FIG. 13, the contact sensor 54 has a cylindrical shape in which a male threaded portion 22a is formed to be screwed into the female threaded portion 16b of the bolt body 52, as in the above embodiment. It has a contact end 24 for detecting a contact state. The contact end 24 is provided so as to be slightly protrusive and retractable, and when it comes into contact with the pin 20, the contact of the internal circuit is electrically closed, and the contact state is detected and output is possible. Furthermore, the contact sensor 54 also has a male threaded portion 22a formed with a male thread that is a corrugated thread that does not loosen.

A cylindrical portion 54a having an outer shape that can be fitted into a circular hole 56a of a protrusion 56 of the bolt body 52 is formed on the base end side of the male threaded portion 22a of the contact sensor 54, and a sealing member such as an O-ring is attached to the cylindrical portion 54a. Two annular seal grooves 58 into which the seals 60 fit are formed. A seal member 60 fits into the seal groove 58, and the seal member 60 is formed to be able to fit into the circular hole 56a of the protrusion 56 of the bolt body 52 in a watertight manner.

Next, a method of using the bolt 50 with a loosening sensor of this embodiment will be explained. As shown in FIGS. 14 and 15, the bolt 50 with a loosening sensor connects the

objects

26 and 28 to be fastened with the nut 30 and the head with the pin 20 fitted and fixed in the deep hole 16 of the bolt body 52. 14, the head 14 of the bolt body 52 or the nut 30 is relatively rotated and tightened to be fixed. At this time, the contact sensor 54 may be screwed into the female threaded portion 16b of the deep hole 16, but the contact sensor 54 may be attached after the bolt body 52 is fastened.

The bolt body 52 is tightened in the same manner as in the above embodiment. After the

objects

26 and 28 are fastened with a predetermined tightening force using the bolt body 52, the contact sensor 54 is set. The setting of the contact sensor 54 is also similar to the above embodiment, by screwing the contact sensor 54 into the deep hole 16 before or after fastening the bolt body 52 with the standard axial force of the male threaded part 12a of the bolt body 52, and making contact. The end portion 24 is brought into contact with the proximal end surface 20b of the pin 20 within the bolt body 52. At this time, the screw engagement is stopped at the contact position so that the contact end portion 24 does not sink into the contact sensor 54. Thereafter, similarly to the above embodiment, the contact end 24 of the contact sensor 54 is separated from the base end surface 20b of the pin 20 by a predetermined distance Δd corresponding to the allowable shrinkage amount ΔD of the male threaded portion 12a of the bolt body 52. let Regarding the predetermined distance Δd, the distance corresponding to the predetermined distance Δd is calculated as the rotation angle of the male screw portion 22a of the contact sensor 54, and the contact end portion 24 is positioned.

The bolt 50 with a loosening sensor of this embodiment has a watertight structure and a contact sensor 54 is attached to the bolt body 52, so that it can detect loosening of the bolt body 54 in an environment where liquid such as rainwater or oil can enter or in a fastened state underwater. It can be detected reliably.

Note that the bolt with a loosening sensor of the present invention is not limited to the above embodiments, and sensors other than contact sensors can be used. Any sensor can be used as long as it can detect the pin in the bolt body and detect the shrinkage of the male threaded portion. For example, depending on the purpose and the size of the bolt, a proximity sensor that is a non-contact sensor, or another optical or magnetic non-contact sensor can be used. The mounting structure of the sensor may be fixed with screws or may be fixed by fitting.

10, 50 Bolt with loosening

sensor

12, 52 Bolt

main body

12a, 22a Male screw part 14 Head 16 Deep hole 18 Lead wire 20 Pin 20a Tip part 20b

Base end surface

22, 54 Contact sensor 24

Contact end part

26, 28 Fastening object 30 Nut 40 Looseness detection system 58 Seal groove 60 Seal member

Claims

a bolt body having a male threaded portion and a head, and a deep hole drilled in the central axis direction of the male threaded portion;
a pin that is partially fixed in the deep hole, and other portions other than the fixed portion are not restrained by the inner circumferential surface of the deep hole;
a sensor fixed to the bolt body and provided to be able to detect the pin based on a change in the axial force applied to the male threaded portion;
In use, due to the loosening of the bolt body, the axial force applied in the direction of the central axis of the bolt body decreases, causing the male threaded portion of the bolt body to contract, causing the sensor to move from the separated state to a predetermined position with respect to the pin. A bolt with a loosening sensor, wherein the sensor outputs a loosening detection signal when the sensor approaches or comes into contact with a position.
The pin has one end fixed to the bottom of the deep hole,
The sensor is fixed to the head of the bolt body and is provided so as to be able to detect the other end of the pin by an axial force applied to the male threaded portion,
In the use state, the axial force applied in the axial direction of the bolt body decreases due to the loosening of the bolt body, and the end of the sensor moves from a separated state to a predetermined position or close to the other end of the pin. The bolt with a loosening sensor according to claim 1, wherein the sensor outputs a loosening detection signal when the bolt comes into contact.
The deep hole communicates from the head of the bolt body to the male threaded portion of the bolt body, and a female threaded portion to which the sensor is fixed is formed in the head of the bolt body. Bolt with loosening sensor described in item 2.
The bolt with a loosening sensor according to claim 3, wherein the sensor is fixed to the head portion of the bolt body in a watertight manner via a sealing member in the female threaded portion of the bolt body.
The bolt with a loosening sensor according to claim 1, 2, 3, or 4, wherein the sensor is a contact sensor that detects the pin by contacting the other end of the pin.
a bolt body having a male threaded portion and a head, and a deep hole drilled in the central axis direction of the male threaded portion;
a pin that is partially fixed in the deep hole, and other portions other than the fixed portion are not restrained by the inner circumferential surface of the deep hole;
Using a bolt with a loosening sensor, the bolt is fixed to the bolt body and is provided with a sensor capable of detecting the pin based on a change in the axial force applied to the male threaded part,
The bolt body is attached to the object to be fastened together with a female threaded member of the object to be fastened, and the male threaded portion of the bolt main body is rotated relative to the female threaded member, and the male threaded portion of the bolt body is rotated relative to the female threaded member. The bolt body is fastened with a predetermined tightening force, and the sensor detects the pin,
Thereafter, the sensor is moved at a predetermined interval corresponding to an allowable amount of shrinkage in the case where the axial force of the male threaded portion decreases due to loosening of the bolt body attached to the object to be fastened, and the male threaded portion shrinks. fixing the sensor to the head of the bolt body in a non-detecting state while separating from the pin;
In use, when the fastening state of the bolt body becomes loose and the amount of shrinkage of the bolt body reaches the allowable amount of shrinkage, the pin changes from the non-detecting state to the detecting state with respect to the sensor, and the pin moves from the non-detecting state to the detecting state, and A method of using a bolt with a loosening sensor, which is characterized by outputting a loosening detection signal.
The pin has one end fixed to the bottom of the deep hole,
The sensor is fixed to the head of the bolt body and is provided so as to be able to detect the other end of the pin by an axial force applied to the male threaded portion,
The deep hole communicates from the head of the bolt body into the male threaded part of the bolt body, and a female threaded part to which the sensor is fixed is formed in the head of the bolt body, and the female threaded part to which the sensor is fixed is formed in the head of the bolt body. 7. When separating the end from the other end of the pin, the sensor is rotated by a predetermined angle around the axis of the bolt body to separate the predetermined distance corresponding to the allowable shrinkage amount. How to use bolts with a looseness sensor.
The sensor is a contact sensor that detects the pin by contacting the other end of the pin,
The contact end of the sensor is in contact with the other end of the pin while the bolt body is fastened to the object to be fastened with a predetermined fastening force,
Thereafter, the contact end is separated from the other end of the pin by the predetermined distance corresponding to the allowable shrinkage amount, and the contact sensor is fixed to the head of the bolt body;
In use, when the fastened state of the bolt body becomes loose and the amount of shrinkage of the bolt body reaches the allowable amount of shrinkage, the other end of the pin separates from the contact end of the contact sensor. The method of using a bolt with a loosening sensor according to claim 6 or 7, wherein the bolt changes from a state to a contact state and outputs a loosening detection signal from the sensor.
A bolt body having a male threaded part and a head, and a deep hole drilled in the direction of the center axis of the male threaded part, and a part fixed in the deep hole, except for the fixed part. A bolt with a loosening sensor is provided, which includes a pin that is not restrained by the inner peripheral surface of the deep hole, and a sensor that is fixed to the bolt body and is provided to be able to detect the pin based on a change in the axial force applied to the male threaded portion. A bolt with a looseness sensor is provided.
A display indicating that the bolt body is loosened by receiving a loosening detection signal from the sensor in a state where the bolt with the loosening sensor is attached to the object to be fastened together with a female threaded member of the object to be fastened. Equipped with equipment,
In use, when the fastened state of the bolt body becomes loose and the amount of shrinkage of the bolt body reaches a predetermined allowable amount of shrinkage, the sensor changes from a non-detecting state to a detecting state with respect to the pin; A looseness detection system, characterized in that a sensor outputs a looseness detection signal, and the display device displays the looseness of the bolt body.
The pin has one end fixed to the bottom of the deep hole,
The sensor is a contact sensor that detects the pin by coming into contact with the other end of the pin, and is fixed to the head of the bolt body, and the other end of the pin is fixed to the head of the bolt body, and the other end of the pin is is provided so that the part can be detected,
In use, when the fastening state of the bolt body becomes loose and the amount of shrinkage of the bolt body reaches the allowable amount of shrinkage, the other end of the pin is separated from the contact end of the contact sensor. 10. The loosening detection system according to claim 9, wherein the bolt body enters a contact state, the contact sensor outputs a loosening detection signal, and the display device displays the loosening of the bolt body.