JP2010008151A - Inspection device of clamped state and inspection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive inspection device of a clamped state for accurately inspecting clamping even with respect to a relatively small-sized screw and simple to adapt, and an inspection method of the clamped state. <P>SOLUTION: The inspection device of the clamped state is used for measuring a change in the impedance of an ultrasonic wave and a change in resonance frequency to inspect the clamping force of the seat surface of a screw head and the contact surface of a part to be clamped. A reference signal is detected as a change in the impedance of the ultrasonic wave or change in resonance frequency during clamping to enable the total inspection of the screw enhanced in detection probability. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inspection method and an inspection apparatus for inspecting a fastening (contact) state of a subject including a plurality of members, for example, a method and an apparatus for inspecting a fastening state of a screw or a rivet.

  Industrial equipment such as generators and motors, transport equipment such as automobiles and airplanes, home appliances such as televisions, washing machines, and refrigerators exhibit performance by combining multiple parts. The techniques used for fastening to realize this combination are generally screw fastening, rivet fastening, welding fastening, caulking fastening, and the like, but screw fastening that is easily disassembled after fastening is widely used. This screw fastening has been used since the Industrial Revolution and can be fastened easily, but has the disadvantage that forgetting to tighten at the time of fastening and loosening after fastening occurs. This forgotten tightening and loosening can cause fatal troubles in the structure, and cases of transportation aircraft often become social problems. Each manufacturer frequently conducts inspections when manufacturing such devices, and spends time and effort on countermeasures against incomplete fastening.

  The screw fastening inspection is performed immediately after the fastening, and the screw which has failed the inspection is corrected by a re-fastening operation. Screw fastening can be done with a force of several tens to thousands of kilograms with a screw boosting function, and the screw size is changed by the required fastening force. There are a wide variety of sizes, from small sizes with a diameter of 1 mm or less to large screws with a diameter of 100 mm or more. In order to obtain a predetermined tightening force with a screw, the tightening torque must be managed. This tightening torque is determined by the tightening force of the screw and the friction between the screw and the part to be fastened. When this friction becomes large due to a screw shape error, insufficient lubrication, etc., there is a problem that a predetermined fastening force cannot be obtained. As inspection methods after screw fastening, confirmation of a gap by visual recognition, fastening force measurement by measuring deformation of a part to be fastened by a strain gauge and a screw, and the like are common.

  In addition, there is a technique described in Patent Document 1 as a conventional technique for screw fastening inspection. In this method, an ultrasonic vibrator is placed on the head of a bolt, the elongation of the bolt at the time of fastening is measured by ultrasonic waves, and the axial force of the bolt is calculated from the amount of elongation. The elongation of the bolt is obtained by measuring the time during which the ultrasonic wave propagates in the axial direction of the bolt. Specifically, from the correlation between the change in bolt length before and after fastening, that is, the amount of elongation and the output change before and after fastening of a strain gauge attached to measure the tensile load applied to the bolt separately, Axial force is calculated.

  Moreover, there exists the technique described in patent document 2 as another prior art of another screw fastening test | inspection. In the technique of Patent Document 2, an ultrasonic transmitter and an ultrasonic receiver are arranged to face each other through a nut on a side surface of a nut screwed to a bolt, and the ultrasonic wave generated from the ultrasonic transmitter is The axial force of the bolt is calculated based on the intensity of the reception echo obtained by receiving with the ultrasonic receiver.

  Furthermore, there are techniques described in Patent Document 3 and Patent Document 4 as conventional techniques for another screw fastening inspection. The technique of Patent Document 3 is to confirm the seating of the screw by measuring the reflectance of the ultrasonic wave at the boundary between the screw and the object to be fastened. Moreover, the technique of patent document 4 measures the attenuation amount of the bolt in the fastening state by ultrasonic pulse count, calculates the axial force using the correlation between the attenuation amount and the axial force of the bolt, This is to confirm the fastening state.

JP 7-253368 A JP-A-8-170933 Japanese Patent Laid-Open No. 1-142426 JP-A-2-88127

  However, in the inspections described in Patent Documents 1 to 3, the smaller the screw, the higher the resolution required for the generated ultrasonic wave. Therefore, an ultrasonic transducer having a high ultrasonic frequency and a wide band is required, and it is difficult to apply to a screw having a screw diameter of 6 mm or less.

  For example, in Patent Document 2, it is necessary to attach an ultrasonic transmitter or an ultrasonic receiver to the side of the head of a nut or bolt, and to a screw that does not have a side area such as a small screw or a countersunk screw. Is not applicable. Further, the technique of Patent Document 4 has a problem that since the ultrasonic pulse becomes long, the resolution is poor and it is difficult to apply to a small screw.

  The screw fastening inspection requires a total inspection and in situ inspection (in-situ inspection), and does not require a structure for inspection on the screw. Otherwise, it cannot be a highly reliable inspection device for mass production.

  In particular, for example, in the method of measuring the extension of the screw shaft by ultrasonic waves shown in Patent Document 1, for a screw having a screw diameter of 6 mm or less, high resolution is required for ultrasonic waves, and from the screw thread. Difficult to apply due to scattered measurement signal. In addition, it is necessary to process the end face where the ultrasonic waves are reflected with high accuracy, which is not suitable for 100% inspection, and the cost for the inspection is high. Therefore, the tightening torque that is used to determine the conditions of the screw tightening torque and its axial force and that generates a predetermined axial force off-line from the production line is determined using this measuring instrument, and this determined tightening torque is determined on the production line. The tightening work is being done with. In this case, there also arises a problem that a predetermined tightening force cannot be obtained due to a change in friction that is a cause inherent to the screw.

  The present invention has been made in view of such a situation, and can be accurately inspected with a relatively small screw (fastening means), and can be applied easily and inexpensively. A method is provided.

  In order to solve the above-described problems, a contact state inspection method and an inspection apparatus according to the present invention evaluate a fastening (contact) state of a plurality of members in a subject including a plurality of members (fastening means and a member to be fastened). As the information, the correlation between the change in mechanical impedance and the contact state is used. For example, if the object contains a screw and a fastened object and you want to detect the tightened state of the screw, the correlation between the contact state of the screw head and the fastened object seated with the mechanical impedance viewed from the screw head Ask from.

  In order to obtain the mechanical impedance, the contact state inspection method and inspection apparatus of the present invention include, for example, a hitting unit that hits a subject including a plurality of members, a detection unit that detects the hitting force and speed of the hitting unit, and a detection And a processing unit that calculates information on the contact state of the plurality of members based on the detection results of the units. Alternatively, based on the detection result of the detection unit, the detection unit that detects the excitation force and speed of the excitation unit, the excitation unit that vibrates the subject including the plurality of members at one frequency or a plurality of frequencies. And a processing unit that calculates information on the contact state. Mechanical impedance is used for information on the contact state of a plurality of members, and the mechanical impedance is obtained from the ratio of the detected striking force or excitation force and speed.

  In addition, the contact state inspection method and inspection apparatus of the present invention includes an electrostrictive type, a magnetostrictive type, and an electrostatic type ultrasonic application that ultrasonically vibrate a subject including a plurality of members at one frequency or a plurality of frequencies. A vibration unit; a detection unit that detects a voltage and a current at an electrical end of the ultrasonic vibration unit; and a processing unit that calculates contact state information of the plurality of members based on a detection result of the detection unit. In this case, as the information on the contact state of the plurality of members, at least one of the electrical impedance at the electrical end of the ultrasonic wave generator or the frequency characteristics of the electrical admittance and the resonance frequency is used. In addition, it is desirable that the ultrasonic vibration unit includes a bolted Langevin type vibrator.

  The frequency of the ultrasonic wave has a resonance frequency of 200 kHz or less, and a cushion material made of, for example, a rubber material is provided between the subject and the ultrasonic vibration unit. The thickness of the cushion material is configured to be 1/10 or less of the wavelength of the cushion material at the ultrasonic frequency. Furthermore, a pressurizing unit that presses the ultrasonic wave generation unit against the subject side with a static pressing force is provided. The pressing force is applied to the ultrasonic vibration unit via a flange provided at a position substantially corresponding to a vibration node of the ultrasonic vibration unit, and the contact pressure between the ultrasonic wave generation unit and the subject is 0.1 MPa. Pressurization is performed to achieve the above.

  Further, the contact state inspection method and inspection apparatus of the present invention includes a screw inspection device including an ultrasonic vibration unit, and a screw fastening determination device that measures an electrical impedance or an electrical admittance and determines a screw fastening state, The screw fastening device is individually arranged, and the screw fastening inspection is performed by the cooperative operation.

  Further features of the present invention will become apparent from the best mode for carrying out the present invention and the accompanying drawings.

  According to the fastening state inspection apparatus and method of the present invention, it is possible to accurately perform a fastening inspection even with a relatively small screw, and further, it is possible to inspect with a simple configuration, thereby realizing an inexpensive fastening state inspection. can do.

  The present invention relates to an inspection method and an inspection apparatus for examining a contact state of a plurality of members in a subject including a plurality of members.

  In the following, a screw is used as a fastening member (means), and the fastening state between the screw and the object to be fastened is taken as an example, and the drawings of the principle of the present invention and the best mode for carrying out the present invention are shown. It explains using. The fastening means includes not only screws but also the rivets, welding, caulking, etc. described above, and the present invention is naturally applicable to inspection of these fastening states.

<First Embodiment>
FIG. 1 is a diagram showing a schematic configuration of a fastening state inspection device according to a first embodiment of the present invention. The object to be inspected in FIG. 1 is an object to be fastened (surface portion) 120 that directly contacts the seating surface of the screw 100 and an object to be fastened (inside) 121 in which a female screw 122 is provided. It is what.

  The screw head 110 of the screw 100 has a striking means 130 for applying a striking force (physical action) Fs to the screw head 110 and a vibration speed v of the screw head generated when the screw head 110 is hit by the striking means 130. Measuring means 131 for outputting the data.

  The measured vibration velocity v is sent to the signal processing unit 132. In the signal processing unit 132, the mechanical impedance (Fs / v) viewed from the screw head 110 is calculated. Here, the striking force Fs is quantitatively obtained by, for example, dropping a weight having a known mass onto the screw head 110 from a known height, and is set in the signal processing unit 132 in advance. In the signal processing unit 132, a mechanical impedance threshold value for determining whether or not the contact state is good is also set in advance. By comparing this threshold value with the measured mechanical impedance (Fs / v), the screw The fastening state between 100 and the objects to be fastened 120 and 121 is determined.

  Next, the relationship between the fastening state of the screw 100 and the mechanical impedance will be described with reference to FIG. FIG. 2 is a vibration mode diagram showing a state of vibration of the subject that occurs when the screw head 110 of the screw 100 is hit by the hitting means 130. 2A shows a vibration mode that occurs when the screw 100 is struck in a state of floating from the object to be fastened, and FIG. 2B shows a vibration mode that occurs when the screw 100 is struck in a completely fastened state. FIG.

  As shown in FIG. 2 (a), in the screw floating state, the screw head 110 is in the form of the vibration mode 111 by striking, and the vibration speed and vibration frequency are mainly in a state where the screw head 110 is not restrained. Sometimes close.

  On the other hand, as shown in FIG. 2B, when the screw 100 is completely fastened, the screw 100 and the fastened objects 120 and 121 are regarded as an integral structure. The appearance is like the vibration mode 112. In the case of FIG. 2B, when the screw head 110 is constrained, the seat surface of the screw head 110 is constrained, and accordingly the vibration frequency and vibration speed are the same as the state of FIG. Will be different. That is, even if the screw head 110 is struck under the same striking conditions, the vibration frequency and vibration speed differ depending on the contact state (restraint state) of the seat surface of the screw head 110. In general, the better the fastening state, the lower the vibration speed. I can say that. Therefore, it is possible to inspect the fastening state of the screw 100 by looking at the change in the frequency characteristic of the mechanical impedance (Fs / v) calculated by the ratio of the striking force Fs and the vibration speed v.

  For measurement of the vibration velocity v, an eddy current type or light quantity type non-contact displacement meter or a laser Doppler vibrometer may be used. As an alternative to the striking means 130, the screw head 110 is mechanically vibrated. Excitation means for applying a physical force to the object to be inspected may be used. When using the vibration means, it is necessary to measure the vibration force generated in the screw head 110. However, a strain gauge or the like is attached to the subject, or the vibration force is calculated from the torque of the motor. The mechanical impedance may be calculated by the signal processing unit 130 from these outputs.

<Second Embodiment>
Next, a method and apparatus (second embodiment) for inspecting a contact state from an electrical impedance of an ultrasonic vibration system using an ultrasonic vibration (giving a physical action) system instead of mechanical impedance will be described. Will be described.

  FIG. 3 is a diagram showing a schematic configuration of a fastening state inspection apparatus according to the second embodiment of the present invention. This apparatus includes an ultrasonic probe 200, a housing 220, and an impedance determination unit 135. The ultrasonic probe 200 and the impedance determination unit 135 are electrically connected by signal lines 133 and 134. The ultrasonic probe 200 includes an electroacoustic transducer 202 such as a piezoelectric element, and is a so-called Langevin type vibrator in which the electroacoustic transducer 202 is sandwiched between a metal front block 203 and a metal backing block 201. . A cushion material 230 made of a rubber material or the like is provided at the machine output end of the front block 203 so as to be sandwiched between the screw head 110.

  Further, the front block 203 is provided with a flange 204 serving as a connecting portion with the housing 220. The ultrasonic probe 200 has a natural vibration mode of half-wave resonance having a vibration amplitude distribution 205 in the axial direction as shown in FIG. The flange 204 is provided at a position corresponding to a node of the vibration mode so as not to affect the vibration mode of the ultrasonic probe 200.

  The cushion material 230 is provided for preventing contact between the ultrasonic probe 200 and the screw head 110 so that a gap is formed between them and the ultrasonic waves are reflected. A pressing force 300 is applied from the upper surface of the housing 220, and the output end of the ultrasonic probe 200 is pressed against the screw head 110 via the flange 204 that does not affect the vibration mode of the ultrasonic probe. The cushion material 230 absorbs the surface roughness and flatness of the screw head 110 by the deformation of the cushion material 230 by the pressing force 300, and allows the ultrasonic wave to efficiently propagate from the ultrasonic probe 200 to the subject including the screw 100. .

  On the other hand, when the thickness of the cushion material 230 becomes equal to the wavelength of the cushion material 230 at the resonance frequency of the half wavelength of the ultrasonic probe 200, the sensitivity decreases due to the attenuation of the ultrasonic waves in the cushion material 230 and the like. To do. For this reason, the thickness of the cushioning material 230 is set to be 1/10 or less of the wavelength of the cushioning material 230 at the resonance frequency of the half wavelength of the ultrasonic probe 200, and the thickness is desirably acoustically transparent. .

  For this reason, when the half-wave resonance frequency of the ultrasonic probe 200 is increased, it is necessary to reduce the thickness of the cushion material 230 accordingly, which makes processing difficult. In addition, when the frequency is high, a high-order vibration mode of the screw head 110 itself is excited, resulting in complicated vibration, which makes it difficult to evaluate the contact state. The ultrasonic probe 200 is composed of a piezoelectric element or metal, and the longitudinal wave velocity is about 5000 m / s. Considering the relationship with the thickness of the cushion material 230 and the suppression of higher-order vibration modes of the screw head 110, the ultrasonic probe 200 desirably has a resonance frequency of at least 200 kHz or less.

  In addition, a sufficient pressing force 300 is necessary for the cushion material 230 to be sufficiently deformed to absorb the surface roughness and flatness of the screw head 110 and to propagate the ultrasonic waves efficiently. If the Young's modulus and thickness of the cushion material 230 are E and t, respectively, and the required deformation amount is Δt, the stress σ required for the cushion material 230 is σ = E × (Δt / t), and the screw head If the area of 110 is S, a pressing force 300 of (σ × S) is required. In general, a rubber material has an elastic modulus E of about 3 to 8 MPa, and if the thickness t of the rubber material is 0.5 mm, a stress of about 30 to 80 kPa is applied to the rubber material if a deformation of about 5 μm is required. Required. Therefore, it is desirable to press at least the contact stress between the cushion material 230 and the screw head 110 to be 0.1 MPa or more.

  Next, the inspection principle of the screw fastening state using the ultrasonic vibration system will be described. FIG. 5 is a diagram showing an electrical equivalent circuit in a state where the ultrasonic probe 200 is attached to the screw head 110. The ultrasonic probe 200 is shown by an equivalent circuit 400 surrounded by a broken line in FIG. 5, and has a mechanical end AA ′ and an electric end BB ′, and a mechanical impedance equivalent circuit 402 of the capacitor 401 and the ultrasonic probe 200 itself. It consists of.

  The mechanical impedance equivalent circuit 410 of the subject viewed from the screw head 110 is connected to the machine end AA ′, and the mechanical impedance 410 of the subject changes depending on the fastening state of the screw 100. Therefore, the fastening state of the screw 100 can be known by measuring the electrical impedance Z as viewed from the electrical end BB '. For example, if the fastening state is improved, the ultrasonic attenuation at the subject is also increased, so that the pure resistance included in the mechanical impedance 401 is increased and the electrical impedance Z is increased. In addition, when the fastening state is improved, the ultrasonic wave propagates not only to the screw 100 but also to the fastened objects 120 and 121, and the number of elements that are reflected or scattered at the fastened object boundary increases. The resonance frequency of the vibration system composed of the subject changes. Therefore, if the correlation between the fastening state of the screw 100 and the electrical impedance or the resonance frequency is examined in advance, the screw fastening state can be inspected as compared with it. It should be noted that the evaluation may be performed using the electrical admittance expressed by the reciprocal of the electrical impedance, or the information on the reverberation frequency and the form of the frequency characteristics of the impedance and the admittance may be used as information for the determination.

The measurement of the electrical impedance Z is performed by the impedance determination unit. As means for measuring the electrical impedance, there are a bridge method and an IV method as shown in FIGS. 6 (a) and 6 (b). In the bridge method of FIG. 6A, the impedance Z ₁ , Z ₂ , Z ₃ and the electrical impedance Z to be obtained are combined with a bridge circuit, and the impedance Z ₁ , Z ₂ , When Z ₃ is adjusted, the electrical impedance Z is determined by calculating Z = Z ₁ Z ₃ / Z ₂ . The impedance frequency characteristic around the resonance frequency of the ultrasonic probe 200 is measured by sweeping the frequency with the oscillator 450.

Furthermore, I-V method of FIG. 6 (b), by detecting the electrical equivalent circuit flows voltage V ₁ and current I shown in FIG. 5, a method for determining the electrical impedance Z. The voltage is measured with a voltmeter 430, and the current I is measured with a voltmeter 440 using a low resistance R. From the voltage V ₁ obtained by the voltmeter 430, the voltage V ₂ obtained by the voltmeter 440 and the low resistance R, the electrical impedance Z can be obtained as Z = V ₁ / I = RV ₁ / V ₂ . There are other methods for obtaining the electrical impedance, such as an automatic balanced bridge method and a resonance method, any of which may be used.

  Note that in a conventional bolt axial force meter using ultrasonic waves, the amount of bolt elongation at the time of fastening is mainly calculated from the reciprocating propagation time of ultrasonic pulses propagating through the bolt. However, for a small bolt or the like, there has been a problem that the screw thread of the bolt or the like scatters an ultrasonic pulse or requires an ultrasonic pulse control with a very high resolution, which is not practical. On the other hand, in the contact state inspection method and inspection device of the present invention, focusing on the screw seating, the contact state between the screw head seating surface and the object to be fastened is measured as an impedance change. Application is possible, and the apparatus can also be configured at low cost.

<Third Embodiment>
Next, a contact state inspection apparatus using an ultrasonic vibration (giving a physical action) system according to a third embodiment of the present invention will be described below with reference to the drawings. FIG. 7 is a diagram illustrating a schematic configuration of an inspection apparatus in a fastening state according to the third embodiment.

  In FIG. 7, the ultrasonic vibration system includes an ultrasonic probe 210 including a backing block 211, an electroacoustic transducer 212 and a front block 213, and a metal solid transmission rod 214. Further, the solid transmission rod 214 is provided with a flange 215 and connected to the housing 221. A cushion material 230 is provided at the output end of the solid transmission rod 214. Other configurations are the same as those of the second embodiment shown in FIG.

  The solid transmission rod 214 is configured such that the thickness on the cushion material 230 side is narrower than the thickness on the ultrasonic probe 210 side with the flange 215 as a boundary. Such a configuration has an effect that, as shown in FIG. 7, there is a spot facing 124 on the fastened object 123 and there is no need to newly change the design of the ultrasonic probe when the screw head 110 has a small size. However, another effect is that the mechanical impedance can be converted.

  FIG. 8 shows a vibration mode of this ultrasonic vibration system, which has a vibration amplitude distribution 216 that causes resonance of one wavelength by the ultrasonic probe 210, the solid transmission rod 214, and the cushion material 230. When the thickness of the output end side of the solid transmission rod 214 is reduced, the vibration amplitude is increased, and the transmission force at the output end of the solid transmission rod 214 is reduced from the input end of the solid transmission rod 214 on the ultrasonic probe 210 side. If there is no loss, the power represented by the product of the transmission force and the vibration speed does not change at both ends, but the mechanical impedance represented by the ratio of the transmission force and the vibration speed is more ultrasonic at the output end on the cushion material 230 side. It becomes smaller than the input end on the probe 210 side. By such a change in mechanical impedance, the mechanical impedance can be converted so that the measurement sensitivity of the ultrasonic probe 210 is optimized.

  Since the ultrasonic vibration system including the ultrasonic probes 200 and 210 or the ultrasonic probe 210 and the solid transmission rod 214 includes at least a plurality of members, for example, the electroacoustic transducer 202, the backing block 201, and the front surface The adhesion state with the block 203 and the adhesion state between the ultrasonic probe 210 and the solid transmission rod 214 greatly affect the accuracy and performance of the inspection. That is, in the case where the above-mentioned adhesion state is made with a conductive adhesive, only the presence of voids on the adhesion surface causes deterioration in performance. In order to improve such performance deterioration and maintain high performance, it is desirable that the ultrasonic vibration system in the present embodiment is screwed.

  FIG. 9 is a diagram showing an ultrasonic vibration system in which each connection portion of a plurality of members constituting the ultrasonic vibration system shown in FIG. 7 is screw-fastened. The ultrasonic probe 500 is a bolted Langevin type vibrator. The two electrodes 521 and 522 and the two layers of piezoelectric elements 511 and 512 that are alternately stacked are sandwiched between the backing block 501 and the front block 502 and fastened by a fastening bolt 531. Further, the ultrasonic probe 500 and the solid transmission rod 217 are also fastened by a connecting bolt 532. In this way, the components of the ultrasonic vibration system are fastened with bolts as much as possible, so that the contact state other than the measurement target can be kept stable, and the inspection performance can be maintained.

<Inspection experiment>
Hereinafter, the experimental result regarding the test | inspection of the screw fastening state using the ultrasonic vibration system of this invention mentioned above is demonstrated. The ultrasonic vibration system used was almost the same as the ultrasonic vibration system shown in FIG. 9, and the thickness of the solid transmission rod was uniform. That is, there is no change in mechanical impedance at the solid transmission rod. A bolt-clamped Langevin type vibrator having a half-wave resonance of about 60 kHz was used for the ultrasonic probe, and a solid transmission rod made of aluminum alloy was fastened to the output end of the ultrasonic probe using a connecting bolt. Viton rubber was used for the cushioning material, and the thickness was 0.3 mm. A flange was provided at the longitudinal center of the solid transmission rod, and a load of 4 kg was applied through the housing. The M2.5 screw was used as the inspection target, and the torque value measured by the torque driver was compared with the electrical impedance measurement result.

  10 to 12 show the experimental results. FIG. 10 is a frequency characteristic diagram of electrical impedance. Using torque as a parameter, FIG. 10A shows the frequency characteristic of the absolute value of the impedance, and FIG. 10B shows the frequency characteristic of the phase. Looking at the frequency characteristics of the absolute value of the impedance (FIG. 10A), the frequency at which the impedance takes the minimum value is the electrical resonance frequency, and the impedance value increases as the torque increases. It can be seen that the frequency also increases.

  FIG. 11 is a diagram in which the impedance value at the resonance frequency and the resonance frequency are plotted against the torque. When the torque is taken logarithmically, both the impedance and the resonance frequency increase linearly. FIG. 10 and FIG. 11 also show experimental results in the case of screw floating where the screw head is not seated, and the presence or absence of seating cannot be evaluated only by the absolute value of the impedance. By using the combination, it can be determined reliably.

  FIG. 12 shows the evaluation result by electric admittance, and in particular, FIG. 12 (a) shows the electric admittance circle, and FIG. 12 (b) shows the maximum conductance value with respect to the torque, that is, the size of the diameter of the admittance circle. As the torque increases, the admittance circle decreases, and it can be seen that the mechanical load impedance as viewed from the screw head increases. Also, from FIG. 12B, it can be seen that as the torque increases, it gradually approaches a constant value. As with impedance, it is difficult to evaluate screw lift using only the conductance value, but by using the change in resonance frequency and torque value together, the presence or absence of seating can be reliably evaluated (the presence or absence of screw lift can be evaluated appropriately). ).

  The above changes in the electrical impedance or electrical admittance or the change in the resonance frequency tend to be observed under the experimental conditions. Depending on the shape and material of the object to be fastened, for example, the resonance frequency decreases, resulting in different results. Can be considered. Therefore, it is desirable to measure the data in a correctly fastened state as a reference in advance and evaluate it by comparing with the data.

<Application example>
Hereinafter, an application example as a screw fastening inspection device will be described. In the present invention, the screw fastening inspection device according to the present invention is disposed in the vicinity of the screw fastening device, and the screw fastening inspection can be performed immediately after the screw fastening operation is completed.

  The screw fastening inspection device is incorporated in the screw fastening device, and the fastening force during the screw fastening is constantly monitored so that the screw fastening inspection can be performed.

  FIG. 13 shows the configuration of a screw fastening inspection device according to the present invention. The fastening of the screw 11 is measured by the ultrasonic probe 10 that generates and receives the ultrasonic wave. The ultrasonic probe 10 transmits ultrasonic waves from the tip of a shaft with the piezoelectric element 12 fixed therein toward the screw head 13. The ultrasonic probe 10 has a shaft structure in which a piezoelectric element 12 is sandwiched therebetween, and a front shaft 14 is disposed between the piezoelectric element 12 and the screw head 13, and a rear shaft 15 is disposed on the opposite side. A soft material 16 is arranged between the screw head 13 and the front shaft 14 to enhance the contact. A mounting flange 17 is machined from the outer periphery of the front shaft 14 and is connected to the fixed shaft 18 here. The fixed shaft 18 is attached to the movable shaft 20 of the air cylinder 19. The movable shaft 20 of the air cylinder 19 has a structure capable of moving up and down by compressed air. The ultrasonic probe 10 includes a driving driver 64 for driving the piezoelectric element 12, a screw for determining screw fastening from a signal obtained from a reflected wave from a contact portion of the seating surface 21 of the screw head 13 and the part to be fastened 22. A fastening determination device 23 is arranged. The ultrasonic probe 10 includes a pressurizing mechanism for facilitating transmission of ultrasonic waves at the contact portion 24 with the screw head 13. This pressurizing mechanism has a structure in which the inspection apparatus can be retracted by this vertical movement by pressurization by air pressure of the air cylinder 19. The screw 11 has a structure in which the part to be fastened 22 is attached to the fastening part 25, and a through hole is formed in the part to be fastened 22 and a tapped hole is processed in the fastening part 25. The fastening part 22 and the fastening part 25 are fastened by the rotation of the screw 11.

  FIG. 14 is a diagram illustrating changes in the impedance line 26 due to screw fastening. The vertical axis represents impedance, and the horizontal axis represents frequency. The impedance line 26 is obtained by measuring the impedance of an ultrasonic wave incident from the ultrasonic probe 10 toward the contact surface 21 of the screw head 13 and the part to be fastened. At this time, the frequency is changed and the change in impedance is compared before and after the fastening to confirm the fastening. It can be seen that the resonance frequency W1 measured by the impedance before fastening is changed to the resonance frequency W2 indicated by the broken line 65 in fastening the screw. The screw fastening can be confirmed by the change in the resonance frequency.

<Summary>
As described above, according to the contact state inspection method and inspection apparatus of the present invention, the contact state of a plurality of members in a subject composed of a plurality of members is calculated based on the information on mechanical impedance. When a fastening state of a screw is inspected, it can be applied to a small screw.

  In addition, instead of pressing the ultrasonic generator containing the ultrasonic transducer against the subject and directly obtaining the mechanical impedance from the force-velocity ratio, the electrical impedance or electrical admittance at the electrical end of the ultrasonic transducer is measured. As a result, the cost and size of the apparatus can be reduced. Since the ultrasonic generator used here has a relatively low resonance frequency, for example, a screw and an object to be fastened are included in the subject. It is.

  In addition, according to the present invention, the change in electrical impedance or electrical admittance due to contact between the screw before and after screw fastening and the object to be fastened is processed as the fastening information, and the fastening force is inspected. It is also possible to perform an inspection process after the screw fastening operation without adding a new structure. For this reason, it is possible to perform a fastening inspection in a short time in situ on the production line, and it is possible to cope with a total inspection.

It is a figure which shows schematic structure of the fastening state test | inspection apparatus (by mechanical impedance measurement) by the 1st Embodiment of this invention. It is a figure which shows the vibration mode of a screw head. It is a figure which shows schematic structure of the fastening state inspection apparatus (thing using an ultrasonic vibration system) by the 2nd Embodiment of this invention. It is a figure which shows the vibration mode of an ultrasonic probe. It is an electrical equivalent circuit diagram of the test | inspection apparatus by 2nd Embodiment. It is a circuit diagram for electrical impedance measurement. It is a figure which shows schematic structure of the fastening state inspection apparatus (thing using an ultrasonic vibration system) by the 3rd Embodiment of this invention. It is a figure which shows the vibration mode of an ultrasonic vibration system. It is a figure which shows the structure of the ultrasonic vibration system by 3rd Embodiment. It is a frequency characteristic figure of the electrical impedance obtained by experiment. It is a characteristic view of the relationship between the torque obtained by experiment, electrical impedance, and resonance frequency. It is a characteristic view of the relationship between the torque and electric admittance obtained by experiment. It is sectional drawing which shows the structure of the screw inspection apparatus which is an example of application of this invention. It is a figure which shows the example of a signal obtained from the screw inspection apparatus which is an example of application of this invention.

Explanation of symbols

10, 200, 210 Ultrasonic probe 11, 100 Screw 12, 202, 212, 511, 512 Piezoelectric element 13, 110 Screw head 14 Front shaft 15 Rear shaft 16 Soft material 17 Mounting flange 18 Fixed shaft 19 Air cylinder 20 Movable shaft 21 Seat surface 22 Fastened part 23 Screw fastening determination device 24 Contact part 25 Fastening part 26 Impedance line 64 Drive driver 65 Broken line 111, 112 Vibration mode 120, 121, 123 Fastened object 122 Female thread 124 Counterbore 130 Impacting means 131 Measuring means 132 Signal processor 133, 134 Signal line 135 Impedance determination unit 201, 211, 501 Backing block 203, 213, 502 Front block 204, 215 Flange 205, 216 Vibration amplitude distribution 214, 217 Solid transmission rod 230 Cushion material 400 Equivalent circuit 01 capacitors 402, 410 mechanical impedance equivalent circuit 420 galvanometer 430, 440 voltmeter 450 oscillator 521 electrode 531 fastening bolt 532 connecting bolt

Claims (19)

An inspection apparatus for inspecting a fastening state of a subject including a fastening means and a member to be fastened,
A physical action adding unit for applying a physical action to the subject;
A detection unit for detecting a physical change of the subject caused by the physical action being applied;
Based on the detection result of the detection unit, a processing unit that calculates information for evaluating the fastening state of the fastening means and the fastened member;
An inspection apparatus comprising: The physical action adding unit is configured by a hitting unit that applies the physical action to the subject by hitting the subject.
The inspection device according to claim 1, wherein the detection unit detects a striking force by the striking unit and a vibration speed of the fastening means generated by the striking. The physical action adding unit is configured by a vibrating unit that vibrates a subject including the above at one frequency or a plurality of frequencies,
The inspection apparatus according to claim 1, wherein the detection unit detects an excitation force of the excitation unit and a vibration speed of the subject generated by the excitation force.   The inspection apparatus according to claim 1, wherein the information for evaluating the fastening state is mechanical impedance. The physical action adding unit is composed of an ultrasonic vibration unit that ultrasonically vibrates the subject including the above at one frequency or a plurality of frequencies,
The inspection apparatus according to claim 1, wherein the detection unit detects a voltage and a current at an electrical end of the ultrasonic vibration unit.   The inspection apparatus according to claim 5, wherein the ultrasonic vibration unit includes an ultrasonic generation unit of any one of an electrostrictive type, a magnetostrictive type, and an electrostatic type.   The inspection apparatus according to claim 5, wherein the ultrasonic vibration unit has a resonance frequency of 200 kHz or less.   6. The inspection according to claim 5, wherein the information for evaluating the fastening state is at least one of an electrical impedance at an electrical end of the ultrasonic excitation unit, a frequency characteristic of electrical admittance, and a resonance frequency. apparatus.   The inspection apparatus according to claim 5, wherein a cushioning material is provided between the subject and the ultrasonic vibration unit, or a liquid or a gel substance is filled.   The inspection apparatus according to claim 9, wherein the cushion material is a rubber material.   The thickness of the cushion material is 1/10 or less with respect to the wavelength of the cushion material at the frequency of ultrasonic vibration generated from the ultrasonic vibration unit. Inspection equipment.   The inspection apparatus according to claim 5, wherein the ultrasonic vibration unit includes a bolted Langevin type ultrasonic transducer.   The inspection apparatus according to claim 5, further comprising a pressurizing unit that presses the ultrasonic vibration unit toward the subject with a static pressing force. The ultrasonic vibration unit includes a flange around a vibration node,
The pressing force by the pressure unit is given to the ultrasonic vibration unit through the flange,
The inspection apparatus according to claim 13, wherein a contact pressure between the ultrasonic vibration unit and the subject given by the pressing force is 0.1 MPa or more. The subject includes a screw;
The inspection apparatus according to claim 1, wherein a fastening state between the screw and the member to be fastened is checked. An inspection method for inspecting a fastening state of a subject including a fastening means and a fastening member,
A physical action adding unit applies a physical action to the subject;
The detection unit detects a physical change of the subject caused by the physical action being applied,
A processing unit calculates information for evaluating a fastening state of the fastening means and the fastened member based on a detection result of the detection unit. The physical action adding unit is configured by a hitting unit that applies the physical action to the subject by hitting the subject.
The inspection method according to claim 16, wherein the detection unit detects a striking force by the striking unit and a vibration speed of the fastening means generated by the striking. The physical action adding unit is configured by a vibrating unit that vibrates a subject including the above at one frequency or a plurality of frequencies,
The inspection method according to claim 16, wherein the detection unit detects an excitation force of the excitation unit and a vibration speed of the subject generated by the excitation. The physical action adding unit is composed of an ultrasonic vibration unit that ultrasonically vibrates the subject including the above at one frequency or a plurality of frequencies,
The inspection method according to claim 16, wherein the detection unit detects a voltage and a current at an electrical end of the ultrasonic vibration unit.

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