JP2000074764A - Socket, torque wrench and gauge for measuring axial tension of bolt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a socket, a torque wrench and a gauge for measuring the axial tension of a tightening bolt accurately and instantaneously. SOLUTION: A receiving hole 7 matching with the head 3a of a tightening bolt 3 is made in the socket body 5 and an ultrasonic sensor 8 being connected with external ultrasonic transmitter/receiver and a measuring system unit is set in the rear of the receiving hole 7. The ultrasonic sensor 8 comprises a piezoelectric element 9 and a damper 10. The piezoelectric element 9 can transmit both longitudinal and transverse ultrasonic waves simultaneously and axial tension of the tightening bolt 3 can be measured precisely by measuring the reciprocal propagation time from the head part 3a to the threaded part 3b of the tightening bolt 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a socket for measuring bolt axial force, a torque wrench, and a bolt axial force meter, and more particularly, to a receiving hole provided in a socket body, which receives both longitudinal and transverse ultrasonic waves. A measurement sensor capable of transmitting and receiving is incorporated, and by measuring and analyzing the reciprocating propagation time of both ultrasonic waves from the head of the fastening bolt to the tip of the screw, the axial stress of the fastening bolt can be precisely determined. It is one that can be measured. Applications of the bolt axial force meter include members subjected to thermal stress and stress fluctuation, for example, automobiles,
Engine and transmission parts for aircraft, ships, etc.
Generator turbine section, bridge section, plant fastening section, gear screw fastening section, etc.

[0002]

2. Description of the Related Art Conventionally, as a bolt axial force meter of this kind,
Ultrasonic pulse eco-position measurement, ultrasonic natural vibration measurement, and the like are known, and in practice, a torque meter is simply used.

An axial force measuring method based on the propagation time ratio of longitudinal waves and transverse waves propagating in the axial direction of a bolt is disclosed in Japanese Patent Laid-Open No. Sho 62-3 / 1987.
No. 8331 discloses it.

[0004] Further, the present inventors have disclosed in Japanese Patent Application Laid-Open No. 9-28.
As disclosed in Japanese Patent Publication No. 8022, there is proposed an apparatus that measures a propagation time and an attenuation rate obtained from a shear wave ultrasonic pulse waveform and determines an applied axial stress.

[0005]

However, in the ultrasonic pulse echo position measurement method, since longitudinal wave ultrasonic waves are used, multiplexing is performed by longitudinal wave → transverse wave → longitudinal wave conversion from the thread portion of the fastening bolt. There is a problem in that the reference peak is difficult to read because of the occurrence of eco-friendly, and there are many misreadings. In addition, it is troublesome to precisely measure the bolt length before fastening or to use a bolt having a fixed bolt length.

On the other hand, the ultrasonic natural vibration measuring method has a disadvantage that the resonance frequencies before and after bolt fastening must be measured. Further, in the case of using a torque meter, the variation after fastening reaches as much as 50%, and there is a limit in precision measurement. In the axial force measurement method disclosed in Japanese Patent Application Laid-Open No. 62-38331, ultrasonic transducers for transmitting and receiving longitudinal waves and transverse waves are vertically adhered or placed in parallel, so that only the thickness of the transducer is propagated. There are disadvantages that a time error occurs and that the same material is not propagated.

Further, the method for measuring the propagation time and the attenuation rate disclosed in Japanese Patent Application Laid-Open No. 9-288022 discloses a method for discriminating an elastic-plastic boundary and preventing multiple echoes caused by longitudinal wave → transverse wave → longitudinal wave conversion. Although effective, it was necessary to precisely measure the bolt length before fastening.

In view of the above, according to the present invention, as the measurement sensor, a piezoelectric element polarized in two types, a piezoelectric domain for generating a longitudinal wave and a piezoelectric domain for generating a longitudinal wave, is applied and transmitted simultaneously. The transmission time of the two ultrasonic waves is measured and analyzed to measure the axial stress value applied to the fastening bolt. Therefore, the bolt can be fastened easily and with appropriate strength without measuring the bolt length in the previous process.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has a socket body rotatable by a torque wrench or a spanner, a stationary member disposed at an outer peripheral portion thereof, and one end provided at one end thereof. A receiving hole that fits into the head of the tightening bolt is formed, and a socket for measuring the axial force of the bolt, in which an ultrasonic sensor having a piezoelectric element is incorporated, is provided behind the receiving hole. It is like that.

That is, in the ultrasonic sensor, a substrate-like piezoelectric element provided in the sensor main body is arranged so as to be in close contact with the head of the bolt, and can simultaneously transmit longitudinal and transverse ultrasonic waves. An externally connected coaxial cable provided on the stationary member is electrically connected to a coaxial cable extending from the piezoelectric element via a slip ring. In this case, the simultaneous transmission of the piezoelectric element is obtained by being polarized into two types, a piezoelectric domain for generating a longitudinal wave and a piezoelectric domain for generating a shear wave.

When the spanner or the torque wrench is manually applied to the socket for measuring the axial force of the bolt of the present invention, the socket body has a locking portion which fits into the tightening opening of the spanner or the torque wrench. May be formed. Further, in the case of a drive type application, an engagement means adapted to a rotation transmitting shaft of a torque wrench may be provided at one end of the socket body. And in the latter case, a torque wrench provided with a socket for measuring a bolt axial force is configured.

Further, in the bolt axial force meter of the present invention, the ultrasonic transmitting / receiving apparatus and the measuring system unit disposed outside are electrically connected to the piezoelectric element of the socket for measuring the bolt axial force. Along with this, longitudinal waves and shear waves transmitted simultaneously from the ultrasonic transmitting and receiving device propagate from the head of the tightening bolt to the tip of the screw portion, and the returned received wave is returned by the measurement system unit. By analyzing, an axial stress value applied to the fastening bolt can be measured. In this case, the measurement system unit includes a waveform analysis unit, a waveform memory, a built-in waveform monitor, a display, a printer, and a personal computer. It is also possible to calculate and thereby calculate the axial stress.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a bolt axial force measuring socket, a torque wrench and a bolt axial force meter according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view conceptually showing a socket for measuring a bolt axial force according to the present invention.
The workpiece 2 arranged above is fixed by a tightening bolt 3 having a head portion 3a and a screw portion 3b.
The tightening bolt 3 is fixed by a spanner (not shown) and a measuring socket 4. The screw portion 3 b is inserted through the mounting hole 2 a of the workpiece 2 and screwed into the screw hole 1 a of the block 1.

As shown in FIG. 2, the socket 4 for measuring the axial force of the bolt has a locking portion 6 which is manually used on the outer portion of the socket body 5, and is provided with a spanner (not shown). Or, it is adapted to fit the tightening opening of the torque wrench. In one end of the socket body 5, a receiving hole 7 that fits the head portion 3a of the tightening bolt 3 is provided.
The ultrasonic sensor 8 shown in FIG. 3 is disposed behind the receiving hole 7.

The ultrasonic sensor 8 has a substrate-shaped piezoelectric element 9 in its main body and a damper 1 made of, for example, a polymer for controlling the attenuation of the ultrasonic wave and fixing the piezoelectric element 9.
0 etc. are incorporated. The piezoelectric element 9 is configured to simultaneously transmit longitudinal and transverse ultrasonic waves, and has, for example, (Ti, Zr) Pb having a perovskite crystal structure.
0 ₃ or TiPb0 oxide and polyvinylidene chloride such as ₃ (PVDF) polymers such as - consists. And
Simultaneous transmission is achieved, for example, by the piezoelectric element 9 uniformly polarizing two types of piezoelectric domains, one for generating longitudinal waves and the other for generating transverse waves. Here, the domain refers to a set of particles, and usually has a size of 10 to 100 μm. Further, a coaxial cable 12 is connected to the piezoelectric element 9 via a lead wire 11 and a slip ring 1.
3 towards.

A stationary member 14 is disposed on the outer peripheral portion of the socket body 5. One end of a coaxial cable 15 provided on the stationary member 14 is connected to the slip ring 1.
3 and the other end is electrically connected to the externally arranged ultrasonic transmission / reception device 31 and the measurement system unit 32 shown in FIG. The slip ring 13 generally means a conductive rotating ring that continuously and electrically connects the rotating conductor and the fixed conductor in combination with a fixed brush. In order to prevent as much as possible, it is preferable to use mercury. The stationary member 14 is
The stationary state is maintained by interposing appropriate bearings 16 and 17 between the socket body 5 and the socket body 5. In this case, if the stationary member 14 is lightweight, the stationary member 14 may co-rotate, so that consideration must be given to giving a weight.

Further, it is preferable that the piezoelectric element 9 is in direct contact with the head portion 3a of the tightening bolt 3, and is applied with a constant pressure of, for example, 0.01 kg / mm ³ or less. Note that indirect adhesion of the piezoelectric element 9 requires the interposition of a couplant (not shown).
A glycerin-based viscous fluid, honey, and anhydrous mechanical oil are selected and applied, for example, in a spray state.

Each of the longitudinal ultrasonic wave and the transverse ultrasonic wave has a frequency within a range of 0.5 to 30 MHz, preferably 1 to 10 MHz.
It is set within the range of Hz. If the frequency is less than 0.5 MHz, the waveform becomes a broadband, making precise measurement impossible.
If the frequency exceeds 0 MHz, the piezoelectric element 8 becomes thin and may be damaged, or the longitudinal wave and the transverse wave cannot be simultaneously propagated. The wavelet wave number is preferably within 5 waves in order to prevent a phase change accompanying the elastic deformation of the tightening bolt 3.

Further, the main body portion 1 of the ultrasonic sensor-8
Numeral 8 is constituted by, for example, a permanent magnet made of SUS304, and as a result, the fastening bolt 3 is attracted to ensure accurate measurement at all times from the uniformity of the pressure contact. When an electromagnet is applied, the N pole and the S pole may be provided concentrically via an iron core (not shown).

FIG. 4 is a sectional view conceptually showing another embodiment of the socket for measuring the axial force of the bolt according to the present invention. The major difference from FIG. 1 is that the socket 1 for measuring the axial force of the bolt is a torque wrench 20 having a drive source (not shown) and a ratchet mechanism 19.
To be attached to and detached from. Then, the socket body 5 has an engaging means 2 which fits the shaft section 21 for rotation transmission.
2 are configured. As the engagement means 22, for example, an engagement hole 22a and a pin b22b are applied.

The torque wrench 20 is not limited to the driving type shown in the figure, but may be a manual type applicable to FIG. In the case where the torque display is provided, the relationship with the bolt axial force becomes clear, and appropriate tightening is enabled.

As the rotating mechanism of the drive type torque wrench 20, a structure in which a pair of bevel gears 24 and 25 are attached to a support shaft 23 is shown, for example. In addition, the stationary member 14 has a bearing 26 on the coaxial cable 15 side, in which weight is taken into consideration and a bearing 26 which is positioned vertically between the stationary member 14 and the socket body 5 so as not to rotate together.
And a bearing 27 located in the middle. Therefore, in such a configuration, the torque wrench 20 including the socket 1 for measuring the axial force of the bolt in a detachable manner is configured.

On the other hand, FIG. 5 is an explanatory view conceptually showing the bolt axial force meter of the present invention. In the socket 1 for measuring the bolt axial force, an ultrasonic transmitting / receiving device 31 and a measuring system unit 32 are provided. It is electrically connected. In this case, the measurement system unit 32 includes a waveform analysis unit 33, a waveform monitor-built-in waveform monitor 34, a display 35, a printer 36, and a personal computer 37.

The clamping bolt 3 is provided with a longitudinal wave from the piezoelectric element 9 by using the coaxial cables 12 and 15 connected to, for example, a BNC connector and RS232C (both not shown). Ultrasonic waves and transverse ultrasonic waves are transmitted simultaneously. From the waveform obtained by the waveform monitor 34 of the measurement system unit 32, the fastening bolt 3
The reciprocating propagation time of both longitudinal and transverse ultrasonic waves from the head 3a to the screw portion 3b of the head 3a is precisely measured, and based on this, the axial stress value applied to the tightening bolt 3 from the personal computer 37 is instantaneously calculated. Is calculated. This calculation processing time is usually 0.2 seconds or less, and accurate bolt axial force can be measured in a short time. Therefore, by accurate management of the bolt axial force, for example, when fastening engine parts,
The number of bolt holes can be reduced, and the cost of the entire product is reduced. It can also be used for periodic maintenance and inspection of suspended steel wires at bridges, plant fastening parts and general-purpose mechanical structural parts.

FIGS. 6A to 6C are time charts of the ultrasonic pulse by the ultrasonic sensor 8 applied in FIG. Here, in FIG.
8, FIG. 6 (b) shows a window gate output signal 39,
FIG. 6C shows the output signal 40 of the zero-cross detector.

FIG. 7 (a) shows the relationship between the elongation of the tightening bolt 4 before and after the application of the tensile axial force. In particular, the initial length L 0 before the application of the axial force is △ after the application of the axial force.
1 shows a state in which the length after loading has become L as a result. On the other hand, FIG. 7B shows the propagation times t _lO and t _so of the longitudinal wave and the transverse wave when the axial force is not applied to the tightening bolt 4, and FIG. Propagation times t _l and t _s of longitudinal and transverse ultrasonic waves when an axial force is applied are shown, respectively.

On the other hand, for the axial force F of each bolt, the following equation is given from the rate of change of sound velocity of longitudinal ultrasonic waves and transverse ultrasonic waves. Here, V ₁₀ and V _so are the initial sound speeds of the unloaded longitudinal and transverse waves of the individual bolt materials, and V _l and V _s are the sound velocities of the longitudinal and transverse ultrasonic waves when the axial force is applied, al , As
This is a coefficient relating to the change in sound speed. V _l = V _lO −al · F (1) V _s = V _so −as · F (2)

From the equations (1) and (2), the length L under the axial force F is given by the following equation: L = (V ₁₀ −al · F) _{t 1} = (V _so −as · F) · ts (3) And the axial force F does not use the initial length L 0, and t · and ts
Simultaneous measurement of, F = a _{(V lO · tl-V so} · ts) / (as · ts-al · tl) (4). Therefore, if V _lO , V _so , al, and as are measured in advance, an accurate axial force F can be calculated by simultaneous measurement of tl and ts.

More specifically, the axial force F is calculated by the subroutine method as a function of tl and ts. The ratio ts / ts between tl and ts is represented by a two-dimensional graph.
FIG. 8 shows the axial force F of the bolt using tl.

As a result, in FIG. 8, the characteristic diagram of the bolt axial force is a two-dimensional graph, and the ratio ts / tl of tl and ts is shown.
Is shown. The straight line in this characteristic diagram becomes a calibration curve if it is input into the personal computer 37 in advance, and a true axial force at a predetermined load can be detected.

[0032]

As described above, according to the present invention, the piezoelectric element 9 in the form of a substrate is in close contact with the bolt head 3a behind the receiving hole 7 of the bolt head 3a provided in the socket body 5. And the piezoelectric element 9 is configured to be able to simultaneously transmit longitudinal and transverse ultrasonic waves. Therefore, there is an advantage that the simultaneous transmission of both the longitudinal wave and the transverse wave makes it possible to measure and analyze the reciprocating propagation time from the bolt head 3a to the screw portion 4b, and to accurately measure the axial force of the bolt. Further, the bolt axial dynamometer of the present invention has an advantage that the axial stress value of the tightening bolt 3 can be calculated periodically and quickly by the personal computer 37 of the measuring system unit 32. Further, the bolt axial force meter of the present invention has an advantage that a more accurate axial force value can be measured by deriving a sound speed change formula of an axial force function from propagation times of longitudinal ultrasonic waves and transverse ultrasonic waves.

[Brief description of the drawings]

FIG. 1 is a conceptual sectional view showing one embodiment of a socket for measuring a bolt axial force according to the present invention.

FIG. 2 is a partial plan view of FIG. 1;

FIG. 3 is a conceptual sectional view showing an ultrasonic sensor.

FIG. 4 is a conceptual sectional view showing another embodiment of the bolt axial force measuring socket of the present invention.

FIG. 5 is a conceptual explanatory view showing an embodiment of the bolt axial force meter of the present invention.

FIG. 6 is a time chart of an ultrasonic pulse by the ultrasonic sensor applied in FIG. 5, (a) is a time chart showing a received signal, and (b) is an output signal of a wind gate. A time chart, (c) is a time chart showing an output signal of the zero cross detector.

FIGS. 7A and 7B are explanatory diagrams showing the relationship between the elongation of the tightening bolt before and after the application of the tensile axial force and the propagation time of the longitudinal and transverse ultrasonic waves, wherein FIG. _-A front view in a state in which the length after the load has become L after being extended, and (b) shows the propagation times t _lO and t _so of the longitudinal wave and the transverse wave when no axial force is applied to the fastening bolt, respectively. In the time chart shown in FIG. 3C, the propagation time t in both longitudinal and transverse ultrasonic waves when an axial force is applied to the fastening bolt.
l, tea showed the t _s, respectively - door.

FIG. 8 is a characteristic diagram of a bolt axial force.

[Explanation of symbols]

 1 Block 2 Workpiece 3 Tightening bolt 4 Socket for measurement 5 Socket body 6 Locking portion 7 Receiving hole 8 Ultrasonic sensor 9 Piezoelectric element 10 Damper 11 Lead wire 12, 15 Coaxial cable 13 Slip ring 14 Stationary member 16, 17 Bearing 18 Sensor body 19 Ratchet mechanism 20 Torque wrench 21 Shaft part 22 Engaging means 23 Support shaft 24, 25 Bevel gear 26, 27 Bearing 31 Ultrasonic transceiver 32 Measurement system unit 33 Waveform analysis unit 34 Monitor 35 Display 36 Printer 37 Personal computer 38 Received signal 39 Wind-gate output signal 40 Zero-cross detector output signal

Claims (7)

[Claims] 1. A socket body 5 is rotatable by a spanner or a torque wrench.
4, one end of which is provided with a head 3a of the tightening bolt 3.
A receiving hole 7 conforming to the above is formed, and a socket for measuring a bolt axial force into which an ultrasonic sensor 8 is incorporated is provided at the back side of the receiving hole 7, wherein the ultrasonic sensor 8 Is configured such that a substrate-shaped piezoelectric element 9 provided in the sensor main body 5 is disposed so as to be in close contact with the bolt head 3a, and is capable of transmitting longitudinal and transverse ultrasonic waves simultaneously. An externally connected coaxial cable 15 provided on the stationary member 14 is electrically connected to the coaxial cable 12 extending from the piezoelectric element 9 via a slip ring 13. Measuring socket. 2. A bolt axial force measuring socket, wherein the piezoelectric element 9 is composed of two types of piezoelectric domains for generating longitudinal waves and piezoelectric domains for generating transverse waves. 3. The bolt axial force according to claim 1, wherein the socket main body is provided with a manual locking portion 6 for a wrench or a torque wrench or an engagement means 22 for transmitting rotation. Measurement socket. 4. One end of the socket body 5 is provided with an engagement means 22 which is adapted to a shaft portion 21 for transmitting rotation of a torque wrench so that a socket for measuring a bolt axial force is provided. Torque wrench characterized by doing. 5. An ultrasonic transmission / reception device 31 and a measurement system unit 32 disposed outside are electrically connected to the piezoelectric element 9 of the socket 1 for measuring the axial force of the bolt, respectively. Along with this, longitudinal waves and transverse waves transmitted simultaneously from the ultrasonic transmission / reception device 31 propagate from the head 3a of the tightening bolt 3 to the tip of the screw portion 3b, and return the received wave to the measurement system unit. 32. A bolt axial force meter characterized by being able to analyze by 32 and measure an axial stress value applied to the tightening bolt 3. 6. The bolt axial force according to claim 5, wherein the measurement system unit comprises a waveform analysis unit, a waveform monitor having a built-in waveform memory, a display, a printer, and a personal computer. Total. 7. The bolt axial force meter according to claim 5, wherein the measurement system unit 32 derives a sound velocity change formula of an axial force function from the propagation times of the two ultrasonic waves, and thereby calculates the axial stress. .