JP2004291217A - Nut runner with axial force meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nut runner with axial force meter which instantly measures the axial force of a bolt or instantly checks if the axial force is good or bad, dispenses with the necessity of preprocessing of the bolt, and is easy to use and good in durability. <P>SOLUTION: A movable body 2 is connected to a base body 1 to be linearly driven, and a torque generating body 4 is attached to a holder frame 3 provided on the movable body. A cylindrical socket body 8 with an end having an engagement hole 10 to engage a bolt head and the other end being opened is rotatably attached to have an axis core not aligned with a drive shaft 7 of the torque generating body, and the drive shaft and the socket body are connected by a rotation transmission mechanism 9. A probe 100 having an oscillation generating body for vertically oscillating the bolt head with electromagnetic force and an oscillation detecting body for detecting the vertical oscillation and converting it to a signal for outputting, wherein at least the oscillation detecting body is arranged inside the socket body, and the probe is attached to a movable member 11 to linearly move to the movable body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a nut runner with an axial force meter, and more particularly, to a nut runner with an axial force meter.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a nut runner having a structure in which a torque meter is incorporated in a shaft that transmits a rotational force to a socket and a tightening force of a bolt can be confirmed has been provided. However, the torque value measured by the torque meter varies greatly due to the frictional force between the bolt and the member to be tightened when the bolt is tightened, and the tightening force of the member to be tightened, ie, the bolt It does not directly represent the axial force.
[0003]
Therefore, Patent Literature 1 discloses a bolt fastening machine capable of measuring an axial force of a fastening bolt. In other words, the tool unit of the nut runner provided with the nut runner control device is provided with a shaft portion for transmitting rotation, and this shaft portion is provided with a socket having an engagement hole that fits into the head of the fastening bolt. Installed. A measurement sensor having a piezoelectric element is incorporated in the back side of the engagement hole, and the piezoelectric element is electrically connected to an external ultrasonic transmission / reception device and a measurement system unit. The piezoelectric element simultaneously emits both longitudinal and transverse ultrasonic waves, and can accurately measure the axial force of the bolt by measuring and analyzing the reciprocating propagation time from the head of the fastening bolt to the screw portion.
[0004]
However, in the bolt fastening machine described in Patent Document 1, a piezoelectric element provided on a shaft portion of a socket coaxially and integrally rotated with a shaft portion is directly in contact with a head portion of the bolt or indirectly through a glycerin-based viscous fluid. Vibration generated in the piezoelectric domain for generating longitudinal and transverse waves of the piezoelectric element is transmitted to the bolt and the reflected wave is also received by the piezoelectric element, so ultrasonic waves are introduced from outside the conventional bolt. As with the axial dynamometer, the pretreatment such as polishing the bolt head and interposing a viscous fluid takes time and effort, and the sensor consisting of the piezoelectric element rotates constantly with the socket. In addition, since the sensor is subject to vibration, there is a problem in the durability of the sensor, and since the cable between the sensor and the control device is connected via a slip ring provided on the shaft portion, Durability problems and the slip ring itself of the slip ring has a problem becomes a source of noise.
[0005]
Incidentally, the sensor system of the present applicant has already provided a bolt tightening force inspection device capable of directly measuring the axial force of a bolt as disclosed in Patent Documents 2 and 3. In other words, Patent Document 2 discloses a configuration in which a ring-shaped magnet having a through hole in the axial center, and having a magnetic pole opposite to each other in the axial direction and an excitation coil are coaxially arranged on the radially outer periphery of the through hole. A vibration generating body, a vibration transmitting rod protruding through the through hole when the bolt head comes into contact with the vibration generating body, and having one end abutting on the bolt head, and a vibration connected to the other end of the vibration transmitting rod. And a vibration detection body having a detector, and an excitation circuit that supplies a pulse current of which frequency fluctuates stepwise to the excitation coil, and the vibration detector detects longitudinal vibration of the vibration transmission rod. A bolt tightening force inspection device including a control device including an A / D converter that converts an output oscillation signal into a digital signal, and a calculation unit that calculates a resonance frequency based on the output signal of the A / D converter Is provided. Since this bolt tightening force inspection device electromagnetically generates vibrations directly on the bolt, there is an advantage that pretreatment is unnecessary and handling is simpler than a conventional system in which ultrasonic waves are introduced from the outside. Further, since the vibration generator and the vibration detector are separated from each other, there is a feature that they are strong against vibration noise.
[0006]
[Patent Document 1] JP-A-2000-141241
[Patent Document 2] Japanese Patent No. 3172722
[Patent Document 3] WO 02/095346 A1
[0007]
[Problems to be solved by the invention]
In view of the above situation, the present invention seeks to solve the problem by instantaneously measuring the axial force of a tightened bolt, or instantly inspecting the quality of the axial force, and pre-processing the bolt. Therefore, it is an object of the present invention to provide a nut runner with an axial force meter that is easy to handle and does not need to be subjected to heat treatment.
[0008]
[Means for Solving the Problems]
The present invention, in order to solve the above-mentioned problem, connects a movable body to a base body such that the movable body can be linearly driven, and a holding frame provided on the movable body includes a torque generator having at least a servomotor and a speed reducer. At the same time, a cylindrical socket body having an engagement hole for engaging with a bolt head at one end and an open end at the other end is rotatably attached by displacing a drive shaft of the torque generator from an axis thereof, The drive shaft and the socket body are connected by a rotation transmission mechanism, and a vibration generator that vertically vibrates the bolt head by electromagnetic force and a vibration detector that detects this vertical vibration, converts it into a signal, and outputs the signal. A probe is arranged so that at least the vibration detecting body is located inside the socket body, and the probe is mounted on a movable member that can be linearly driven with respect to the movable body, and is engaged with an engagement hole of the socket body. Combination By contacting the probe to the bolt head and constituting the axial force meter nut runner, characterized by measuring the axial force.
[0009]
Here, the rotation transmission mechanism is formed by meshing a first gear fixed to the drive shaft with a second gear provided on an outer periphery of the socket body, and the probe is provided inside the socket body. Are arranged in a non-contact state, a disk having the engaging hole at the center is detachably attached to one end of the socket body, and the reduction gear is attached to the torque generator. It is preferable that a torque sensor be disposed between the drive shaft and the drive shaft.
[0010]
The vibration generator has a through hole through which a vibration transmission rod can be inserted at the axis, and an annular magnet magnetized so as to have mutually opposite magnetic poles in the axial direction on the radially outer periphery of the through hole. One or a plurality of axes are arranged in the axial direction, and the excitation coil is arranged coaxially on the outer peripheral side or the inner peripheral side of the annular magnet, and the vibration detecting body is provided with a vibration detector in a cylindrical sleeve in the axial direction. The vibration transmission rod is arranged so as to be slidable and elastically biased in the distal direction, and the vibration transmission rod is connected to the vibration detector so that vibration can be transmitted. At least both ends of the sleeve are provided in a cylindrical casing. And a probe having the vibration detection body attached to the tip and exposing the tip of the vibration transmission rod from the through hole.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. 1 to 9 show a nut runner with an axial force meter according to the present invention, and FIGS. 10 to 12 show a bolt axial force meter, wherein reference numeral 1 denotes a base body, 2 denotes a movable body, and 3 denotes a holding frame. 4 is a torque generator, 5 is a servo motor, 6 is a speed reducer, 7 is a drive shaft, 8 is a socket body, 9 is a rotation transmission mechanism, 10 is an engagement hole, 11 is a movable member, 100 is a probe, 101 is A vibration generator, 102 is a vibration detector, 103 is a control device, and 104 is a vibration transmission rod.
[0012]
In the nut runner with an axial force meter according to the present invention, the movable body 2 is connected to the base body 1 so as to be linearly driven, and at least the servo motor 5 and the speed reducer 6 are mounted on the holding frame 3 provided on the movable body 2. A torque generating body 4 is mounted, and an engagement hole 10 for engaging with a bolt head is provided at one end and a cylindrical socket body 8 having the other end opened is connected to the drive shaft 7 of the torque generating body 4. The drive shaft 7 and the socket body 8 are connected to each other by a rotation transmitting mechanism 9 so as to be rotatably mounted with a shaft center shifted, and a vibration generator 101 for longitudinally vibrating the bolt head by electromagnetic force and the longitudinal vibration A probe 100 having a vibration detecting body 102 for detecting, converting into a signal and outputting the signal is arranged so that at least the vibration detecting body 102 is located inside the socket body 8 and the probe 100 is connected to the movable body 2. It is obtained as attached to the linear drive a movable member 11, to measure the axial force is brought into contact with the probe 100 on the bolt head engaged with the engaging hole 10 of the socket body 8 against. Here, displacing the axis of the drive shaft 7 from the axis of the socket body 8 is a concept including not only parallel displacement but also displacement at a right angle or any angle.
[0013]
More specifically, the base body 1 is a long member in the shape of a plate or a channel, and is attached to a movable portion (not shown) such as a fixed portion C or a robot arm as shown in FIG. The base body 1 is provided with a guide rail 12 along its longitudinal direction, and a liner 13 attached to the movable body 2 is connected so as to be guided by the guide rail 12 and move linearly. . Further, a fixing plate 14 is attached to one end (the upper end in the drawing) of the base body 1 at a right angle to the guide rail 12, and an air cylinder 15 is attached to the fixing plate 14. The end of the movable body 2 is connected with a connecting tool 17. Therefore, by supplying pressurized air to the air cylinder 15, the movable body 2 can be linearly driven with respect to the base body 1. Instead of the air cylinder 15, it is possible to use other linear drive means such as a rack and a pinion, a sprocket and a chain, a pulley and a timing belt, as well as a hydraulic cylinder.
[0014]
As shown in FIGS. 1 and 4, the torque generator 4 is mounted on a holding frame 3 provided at an end (a lower end in the drawing) of the movable body 2, and the socket body 8 is rotatable. Installed. The holding frame 3 has upper and lower plates 18 and 19 and an intermediate plate 20 attached to the end of the movable body 2 with an upper and lower space, and a connecting plate between the ends of the upper and lower plates 18 and 19. 21 and cover plates 22 and 22 attached to both sides to completely close the periphery to form a box. The main body of the torque generator 4 is fixed to the upper plate 18 of the holding frame 3, and the drive shaft 7 extends inside the holding frame 3 via the shock buffer 23. The lower plate 19 and the intermediate plate 20 are rotatably supported by bearings 24, 24. The socket body 8 is rotatably supported on the lower plate 19 and the intermediate plate 20 by bearings 25 and 25 in the same manner as the drive shaft 7. Further, an opening 26 through which the probe 100 can pass is formed in the upper plate 18 extending the center axis of the socket body 8.
[0015]
Further, a movable member capable of linearly driving the probe 100 with respect to the movable body 2 while arranging the probe 100 in a non-contact state so that at least the vibration detecting body 102 is positioned inside the socket body 8. 11 is attached. To this end, a linear guide rail 27 is attached to the movable body 2, a runner 28 attached to the movable member 11 is connected so as to be able to move linearly along the guide rail 27, and further attached to the upper part of the movable body 2. The piston 30 of the air cylinder 29 is connected to the end of the movable member 11 by a shock absorbing connector 31. As described above, the air cylinder 29 can be replaced by another linear driving means.
[0016]
Here, as shown in FIGS. 1, 3, and 4, the shock absorbing connector 31 has flange portions 33, 33 protruding from upper and lower ends of a shaft body 32 and attached to an upper end of the movable member 11. A hole of the support plate 34 is vertically movably mounted on the shaft 32 between the flange portions 33, 33, and a compression coil spring 35 is interposed on the shaft 32 between the support plate 34 and the upper flange portion 33. ing. The lower end of the movable member 11 reaches the inside of the holding frame 3 through the opening 26, and the upper part of the probe 100 is held by a mounting part 36 provided at the lower end. In this case, even when the air cylinder 29 is driven, the probe 100 is driven downward by a pressing force whose upper limit is regulated by the elastic force of the compression coil spring 35 to contact the bolt head B. I have. The cable 128 connected to the upper end of the probe 100 is drawn out of the support frame 3 through the opening 26 of the upper plate 18.
[0017]
Next, as shown in FIGS. 4 and 6, the rotation transmission mechanism 9 engages with a first gear 37 fixed to the drive shaft 7 and a second gear 38 provided on the outer periphery of the socket body 8. Things. In the present embodiment, the second gear 38 is formed by mounting a plurality of roller pins 39,... At equal intervals in an axial direction in an annular groove formed on the outer periphery of the socket body 8. Reference numeral 37 denotes a recess formed on the entire periphery for receiving the roller pin 39. As the rotation transmitting mechanism 9, a normal spur gear, a bevel gear, a sprocket, a chain, and other rotation transmitting means can be employed.
[0018]
A disk 40 having the engaging hole 10 at the center is detachably attached to one end of the socket body 8. In this way, even if the bolts B have different sizes, the disk 40 having the corresponding engaging holes 10 can be replaced.
[0019]
Further, if a torque sensor 41 is arranged between the speed reducer 6 and the drive shaft 7 on the main body of the torque generator 4, the tightening torque is measured simultaneously with the measurement of the axial force of the bolt B by the probe 100. Thus, the tightened state of the bolt B can be monitored with higher reliability.
[0020]
FIGS. 7 to 9 show a procedure for tightening a bolt B to a member A to be tightened and measuring the axial force by using a nut runner with an axial force meter according to the present invention. First, from the state where the bolt head B and the socket body 8 in FIG. 7 are separated from each other, the air cylinder 15 is driven to lower the movable body 2, and the bolt head B is inserted into the engagement hole 10 of the socket body 8. Accept. In this state, the vibration transmitting rod 104 of the probe 100 is not in contact with the bolt head B. Then, the servo motor 5 is rotated to rotate the drive shaft 7, and the socket body 8 is rotated via the rotation transmission mechanism 9 to tighten the bolt B to the member A to be tightened. In this case, the probe 100 remains stationary. Then, the movable member 11 is moved down by driving the air cylinder 29 to press the vibration transmitting rod 104 of the probe 100 against the bolt head B and press the tip of the probe 100 against the bolt head B. At the tip of the probe 100, a vibration generator 101 is incorporated, and a vibration is generated in the bolt B by an excitation pulse supplied from the controller 103 to the vibration generator 101, and the vibration is transmitted to the vibration transmission rod 104. Vibration is detected by a vibration detector 102 incorporated in the probe 100 via the probe 100, and the detection signal is processed by the control device 103 to calculate a resonance frequency, which is correlated with the axial force of the bolt.
[0021]
Next, a bolt axial force meter including the probe 100 and the control device 103 used in the present embodiment will be described in more detail with reference to FIGS. As shown in FIG. 10, the probe 100 includes a vibration generator 101 that longitudinally vibrates the bolt head B by electromagnetic force, a vibration detector 102 that detects the longitudinal vibration, converts the signal into a signal, and outputs the signal. 103.
[0022]
More specifically, the vibration generating body 101 has a through hole 105 through which a vibration transmission rod 104 can be inserted at an axis thereof, and a magnetic pole which is mutually opposed in the axial direction at a radially outer periphery of the through hole 105. A magnetized annular magnet 106 is arranged in one or more axial directions, and an excitation coil 107 is arranged coaxially around the outer periphery of the annular magnet 106. In the illustrated example, the annular magnet 106 is magnetized with an S pole on the lower surface and an N pole on the upper surface, and the two annular magnets 106 are arranged in contact with each other in the axial direction. A number of annular magnets 106 are arranged in the axial direction. The magnetic poles of the annular magnets 106 may have the S pole and the N pole reversed, but the magnetization directions of the magnetic poles of all the annular magnets 106 need to be set to the same direction. The above-described annular magnet 106 and excitation coil 107 are sealed in a cap-shaped cover 108 by a fixing material 109, and a hole 110 from which the vibration transmission rod 104 protrudes is formed on the lower surface of the cover 108.
[0023]
In addition, the vibration detector 102 has a vibration detector 112 such as an acoustic emission sensor (AE sensor) disposed in a cylindrical sleeve 111 so as to be slidable in the axial direction without resistance. Vibration transmission rods 104 are connected so as to transmit vibration, and ring-shaped flanges 113 and 114 having a diameter larger than the outer diameter of the sleeve 111 are fixed to the upper end and lower end of the sleeve 111. Between the vibration detector 112 and the vibration detector 112, a coil spring 115 is interposed to elastically urge the vibration transmission rod 104 in a protruding direction. Here, the vibration transmission rod 104 penetrates through the hole 116 of the lower flange 114, and in a non-use state shown in FIG. 10, the lower end of the vibration detector 112 or the base of the vibration transmission rod 104 is formed in the flange 114. The connecting portion stops. A lead wire (not shown) of the vibration detector 112 is drawn out from a hole 117 of the upper flange 113.
[0024]
Here, as the vibration transmission rod 104, a nonmagnetic and electrically insulating inorganic solid is preferable so that an eddy current is generated inside and does not vibrate due to an external magnetic field. Non-magnetic and electrically insulating ceramics are preferable in terms of having both of the rigidity, and fine ceramics using high-purity alumina are more preferable. If an inorganic solid represented by ceramics is used, the elasticity of the vibration transmission rod is larger than the elasticity of the bolt B and its resonance point is much higher than the measurement range. There is an advantage that the vibration does not affect the measurement result as noise. Further, in order to prevent generation of noise due to lateral vibration of the vibration transmission rod 104, the diameter of the vibration transmission rod 104 is preferably set to about 3 mm or more, and the tip of the vibration transmission rod 104 is preferably formed to be round. .
[0025]
The vibration detecting body 102 is held in a cylindrical casing 118 constituting the outer shape of the probe 100 via a vibration-proof material that absorbs vibration. That is, the cylindrical vibration isolator 119, 120 is mounted on the outer periphery of the upper and lower ends of the sleeve 111 and inserted into the casing 118, and the annular vibration isolator 121, 122 is brought into contact with the flange 113, 114 from above and below. Is interpolated. Further, the cable mounting member 124 is screwed with the holding member 123 inserted into the upper end of the casing 118, and the annular vibration isolator 121 is pressed against the flange 113 via the holding member 123. On the other hand, at the lower end of the casing 118, the upper part of the connecting member 125 is inserted, and an annular protruding edge 126 formed on the outer periphery of the connecting member 125 is fixed in contact with the lower end of the casing 118. The annular vibration isolator 122 is pressed against the flange 114. In addition, a through hole 127 through which the vibration transmission rod 104 penetrates is provided at the center of the connecting member 125.
[0026]
Here, as the material of the cylindrical vibration-proof materials 119 and 120 and the annular vibration-proof materials 121 and 122, a vibration-proof gel or a vibration-proof rubber is preferably used. In the present embodiment, particularly, the vibration-proof gel is used. And a good anti-vibration effect is obtained. This anti-vibration gel used "Gelnac" (product provided by Nippon Automation Co., Ltd.). As described above, the vibration transmitted from members other than the vibration transmission rod 104 is absorbed by the cylindrical vibration-proof materials 119 and 120 and the annular vibration-proof materials 121 and 122, and is prevented from being transmitted to the vibration detector 112. Therefore, noise is less likely to be mixed in the detection signal indicating the longitudinal vibration of the bolt B, and a highly sensitive detection signal can be obtained.
[0027]
The casing 118 and the cover 108, which are screwed to the lower part of the connecting member 125 with the upper end opening of the cover 108 constituting the vibration generator 101 fitted outside, have the same outer diameter. Is continuous. Here, the outer shape of the probe 100 is 2 cm in diameter and about 12 cm in length. A lead wire (not shown) connected to the excitation coil 107 is drawn out to the cable mounting member 124 through the space between the sleeve 111 and the casing 118.
[0028]
Here, the arrangement of the annular magnet 106 and the excitation coil 107 is arbitrary. In the case of the present embodiment, the annular magnet 106 is disposed radially inward and the excitation coil 107 is disposed radially outward. In such an arrangement, the outer shape of the bolt head B is substantially equal to the outer shape of the excitation coil 107. Applies universally when equal or greater. In particular, as shown in FIG. 12A, when there is a concave portion B1 for fitting a rotary tool in the center of the bolt head B, the excitation coil 107 can be made to approach the outer peripheral portion B2 of the head B. , And the bolt B are efficiently vibrated. Further, as shown in FIG. 12B, when the outer shape of the bolt head B is considerably smaller than the outer shape of the probe 100 and the upper surface of the head B is flat, the excitation coil 107 is moved radially inward. It is desirable to arrange the annular magnet 106 radially outward so that the excitation coil 107 fits within the upper surface of the head B.
[0029]
Next, the control device 103 that supplies a pulse current to the excitation coil 107 and calculates the resonance frequency when the bolt vibrates at the natural frequency will be described in detail with reference to FIG. FIG. 13 is a block diagram illustrating a schematic configuration of the control device 103. In FIG. 13, reference numeral 112 denotes a vibration detector, 104 denotes a vibration transmission rod, 106 denotes an annular magnet, and 107 denotes an excitation coil.
[0030]
The control device 103 includes an excitation circuit 130 that supplies a pulse current to the excitation coil 107, an amplification circuit 131 that amplifies an output signal of the vibration detector 112, and an A / D converter that converts an output signal of the vibration detector 112 into a digital signal. 132, a CPU 133 for controlling them, a RAM 134, a ROM 135 storing programs for executing various processes in accordance with predetermined procedures, a rewritable EEPROM 136 storing data such as physical characteristics of bolts and plate materials, and calibration curves, detection results, etc. 137, input means 138 for inputting condition settings, etc., and an interface circuit 141 via connection to an external device such as a computer 139 or a portable information device (PDA) 140.
[0031]
In the excitation circuit 130, a pulse voltage having a sharp rise or fall as shown in FIG. 14 is applied to the excitation coil 107 under the control of the CPU 133, and a pulse current is supplied. Although a rectangular wave is preferable as the pulse voltage in the present embodiment, the present invention is not limited to this, and another pulse wave may be used. The excitation frequency of such a pulse current can be changed stepwise in units within the range of 1 Hz to 20 Hz under the control of the CPU 133. For example, when the frequency starts from the maximum value of 50 kHz, the frequency is gradually reduced to a desired minimum value in units of 10 Hz. One cycle time in which the excitation frequency is changed stepwise from the maximum value to the minimum value is called one cycle. When such a pulse current is supplied to the excitation coil 107, the vibration detector 112 detects the longitudinal vibration of the volt B and outputs an oscillation signal having a waveform as shown in FIG.
[0032]
In the time chart of FIG. 16, in the n-th or (n + 1) -th measurement cycle, the CPU 133 controls the timing of the excitation signal output from the excitation circuit 130 by the signal output time τ according to the waveform of FIG. In addition, the signal input timing for taking in the output signal of the vibration detector 112 is changed to the terminal time t in the signal output time τ according to the waveform of FIG. ₁ Is controlled by That is, during the time τ, the volt is excited by the pulse current having a constant frequency, but after the oscillation of the volt is stabilized, the terminal time t ₁ During this period, the output signal of the vibration detector 112 is taken in.
[0033]
In each measurement cycle, a pulse signal of a constant frequency as shown in FIG. 14 is supplied to the excitation coil 107 during the signal output time τ according to the waveform of FIG. Are supplied to the excitation coil 107 repeatedly, and the excitation frequency is reduced step by step. In this manner, the excitation frequency is stepwise reduced from the maximum value to the minimum value, as shown in FIG. The vibration detector 112 detects the vibration of the volt B in accordance with each excitation frequency and outputs an oscillation signal. This oscillation signal has the termination time t shown in FIG. ₁ During the period, the signal is converted into a digital signal by the A / D converter and then taken into the CPU. Such an oscillation signal has a waveform as shown in FIG. 17A, and forms a peak when the excitation frequency matches the resonance frequency. As described above, since the signal output time τ is set and the pulse current is supplied to the excitation coil 107 at the excitation frequency that changes stepwise, the oscillation signal corresponding to the excitation frequency is extremely changed during the signal output time τ. It is possible to detect and identify accurately.
[0034]
At the end of each measurement cycle, the CPU 133 sets the signal processing time t in accordance with the control signal of FIG. ₂ During this period, the digitally converted oscillation signal (digital input signal) is processed to calculate the resonance frequency. Specifically, the value of the digital input signal is processed by the CPU 133 and temporarily stored in the storage table together with the corresponding excitation frequency and cycle. Next, the resonance frequency calculating means is called out of the program stored in the ROM 135, and referring to the storage table, the waveform shown in the envelope waveform 143 of the waveform of FIG. The data is obtained, the peak value is found, and the oscillation frequency corresponding to this peak value is set as the resonance frequency. Such processing is performed for each measurement cycle. Note that the number of measurement cycles may be one or more. The average value of the resonance frequency may be calculated from a plurality of measurement periods.
[0035]
Next, the bolt tightening force evaluation means is called out of the program stored in the ROM 135, and using this means, the calibration curve table stored in the EEPROM 136 is referred to and the bolt axial force (bolt tightening force) corresponding to the resonance frequency is referred to. ) Is calculated. After the bolt axial force is calculated, the value of the bolt axial force may be displayed on the display means 137, or displayed on a display lamp (not shown) according to the magnitude of the bolt axial force, or the speaker ( (Not shown), a tone sound corresponding to the magnitude of the bolt axial force may be output.
[0036]
Also, the vibration detector 112 does not always output a waveform having a clear peak as shown in FIG. 17A, and outputs a waveform having a plurality of peaks as shown in FIG. It may be difficult to identify the peak value corresponding to the resonance frequency. In such a case, a group of peak waveforms having a peak (waveform group) is selected, and a waveform synthesis process is performed on each waveform group to generate synthesized waveforms 144a and 144b as shown in FIG. It is preferable to find the maximum value from the peak values of 144a and 144b and set the oscillation frequency corresponding to the maximum value as the resonance frequency. Note that the composite waveform in FIG. 17D is slightly reduced in size compared to the waveform in FIG. 17C.
[0037]
As the calibration curve table, a table in which "bolt type" and "bolt size", "thickness of the fastened plate", "maximum axial force", "offset value" and the like are input in advance and used is used. Alternatively, the coefficients of the polynomial may be calculated by the least squares method, and an interpolation formula may be obtained and used. In order to execute such a least square method or the like, it is sometimes easier to use the computer 139. In such a case, it is preferable that after calculating the coefficients of the polynomial by the computer 139, the data is transferred to the CPU 133 via the interface circuit 141 shown in FIG. 13 and stored in the EEPROM 136 or the like.
[0038]
In addition, if only the tightening state of the bolt is to be checked, the reference value of the bolt tightening force (reference tightening force) or the resonance frequency (reference resonance frequency) corresponding to the reference tightening force is registered. Set the upper limit and lower limit centered on the reference tightening force or reference resonance frequency.If the measured tightening force or resonance frequency is between the upper limit and lower limit, it is determined to be within the acceptable range, In that case, it can be rejected.
[0039]
Also, a portable information device 140 is connected to the interface circuit 141, and the data of the inspection result obtained by the control device 103 is sent to a main computer at a center (not shown) via the Internet 142. It is also possible to perform analysis, save history, and the like, send the analysis result and the like back to the control device 103 via the Internet 142, and display the result on the display unit 137. In this case, since the amount of information processed by the control device 103 is significantly reduced, the performance of the CPU 133 and the storage capacity of various memories can be reduced, and the control device 103 can be made compact. In addition, it is of course possible to provide a communication function in the control device 103 itself. Further, except for a battery for supplying power to the excitation coil 107, the probe 100 and the control device 103 can be connected wirelessly. Alternatively, the computer 139 and the control device 103 can be connected by a wireless LAN or Bluetooth technology. In this case, if the computer 139 is connected to the Internet 142, data can be processed by the main computer of the center.
[0040]
The axial dynamometer comprising the probe 100 and the control device 103 can measure the tightening force of each bolt B as a net absolute value, which requires absolute calibration with a bolt having a known tightening force. is necessary. However, when measuring the variation in the tightening force of a plurality of bolts or comparing the tightening force of a bolt that has been properly tightened with the tightening force of another bolt, absolute calibration is unnecessary. For example, if a setting is made such that the value of the obtained natural frequency is converted as “100%” when a bolt that has been properly tightened is measured, the natural frequency of the bolt is measured when another bolt is measured. It is also possible to use such a method that the value is displayed as “110%” or “90%”.
[0041]
The axial dynamometer of the present embodiment has a vibration generator configured by arranging an annular magnet having mutually opposite magnetic poles in the axial direction and an excitation coil coaxially in and out in the radial direction, thereby generating an external magnetic field. Since it is possible to efficiently penetrate the bolt head, and to supply a sharp rising or falling pulse current to the excitation coil to generate a large induced electromotive force at the bolt head, the resonance level of the bolt is increased. And a resonance frequency with high sensitivity can be obtained, so that an accurate bolt axial force can be calculated. In addition, by using a pulse current with a stepwise change in frequency, the duration of a constant frequency during the change of the frequency is controlled to detect the resonance of the bolt within the duration and to determine the exact resonance frequency. Therefore, it is possible to calculate an accurate bolt axial force and improve the measurement accuracy.
[0042]
【The invention's effect】
The nut runner with the axial force meter according to the first aspect of the present invention can tighten a bolt, and can instantaneously measure the axial force of the tightened bolt, or instantly determine whether the axial force is good or bad. Can be inspected. Further, there is no need to perform a pretreatment on the bolt as in the prior art, and the handling is easy. Furthermore, since the torque generator and the socket body are arranged with their axes shifted, and the probe is arranged inside the socket body, the probe does not rotate even when tightening the bolts, and therefore has excellent durability.
[0043]
According to the second aspect, the rotation transmission mechanism is formed by meshing the first gear fixed to the drive shaft with the second gear provided on the outer periphery of the socket body, so that the device becomes compact and torque is generated. Torque can be reliably transmitted from the body to the socket body.
[0044]
According to the third aspect, the probe is arranged in a non-contact state inside the socket body, so that unnecessary vibration and load are not applied to the probe, so that the durability is improved, as well as the other parts. Since the transmission of the generated vibration noise to the probe can be suppressed, the axial force can be measured with high sensitivity and high accuracy.
[0045]
According to the fourth aspect, since a disk having an engagement hole at the center is detachably attached to one end of the socket body, even if the bolts are different in size, a circle having an engagement hole corresponding thereto is provided. You just have to replace it with a board. In addition, when the engagement hole is worn due to long-term use, it can be easily replaced.
[0046]
According to the fifth aspect, the torque generator is provided with the torque sensor between the speed reducer and the drive shaft, so that the tightening torque can be measured simultaneously with the measurement of the bolt axial force by the probe and the control device. It is possible to evaluate the tightening force with higher reliability.
[0047]
According to the sixth aspect, the vibration detector is held on the casing via the vibration isolator, so that the vibration transmitted from members other than the vibration transmission rod is absorbed by the vibration isolator, so that the vibration detector This prevents noise from being mixed into the output signal and improves detection accuracy.
[Brief description of the drawings]
FIG. 1 is a side view showing a nut runner with an axial force meter according to the present invention in a partial cross section.
FIG. 2 is a front view of the same.
FIG. 3 is an abbreviated front view showing a linear drive mechanism of the movable body and the movable member.
FIG. 4 is an enlarged sectional view of a main part of the same.
FIG. 5 is an omitted bottom view.
FIG. 6 is a simplified plan view showing a rotation transmission mechanism.
FIG. 7 is a simplified side view showing a use example of the present invention and showing a state before bolt tightening.
FIG. 8 is a simplified side view showing a state after bolt tightening.
FIG. 9 is an enlarged sectional view of a main part showing a state in which the axial force of the bolt is being measured.
FIG. 10 is a schematic sectional view of a probe.
FIG. 11 is a schematic sectional view showing a relationship between a bolt and a probe in an axial force measurement state.
12A and 12B show the relationship between the shape of the bolt head and the tip structure of the probe. FIG. 12A is an abbreviated perspective view showing the tip structure of the probe when the bolt head has a concave portion at the center, and FIG. It is an abbreviated perspective view showing a tip structure of a probe when a bolt head is a plane.
FIG. 13 is a schematic block diagram showing one embodiment of a control device.
FIG. 14 is a diagram illustrating an example of a pulse voltage output by an excitation circuit.
FIG. 15 is a diagram showing a vibration waveform of a bolt output by a vibration detector.
FIG. 16 is a time chart showing various signals.
FIG. 17 is a schematic diagram showing an oscillation signal and a processing signal thereof.
[Explanation of symbols]
1 base body 2 movable body
3 Holding frame 4 Torque generator
5 Servo motor 6 Reduction gear
7 Drive shaft 8 Socket body
9 Rotation transmission mechanism 10 Engagement hole
11 movable member 12 guide rail
13 Liner 14 Fixing plate
15 Air cylinder 16 Piston
17 Connector 18 Upper plate
19 Lower plate 20 Intermediate plate
21 connecting plate 22 cover plate
23 Impact buffer 24 Bearing
25 Bearing 26 Opening
27 Guide rail 28 Runner
29 air cylinder 30 piston
31 shock absorbing connector 32 shaft
33 Flange part 34 Support plate
36 Mounting part 37 First gear
38 Second gear 39 Roller pin
40 disk 41 torque sensor
100 Probe 101 Vibration generator
102 Vibration detector 103 Control device
104 Vibration transmission rod 105 Through hole
106 Ring magnet 107 Excitation coil
108 Cover 109 Fixing material
110 hole 111 sleeve
112 Vibration detector 113, 114 Flange
116, 117 holes 118 casing
119,120 Cylindrical vibration isolator
121,122 annular vibration isolator
123 Holding member 124 Cable mounting member
125 connecting member 126 protruding edge
127 Through hole 128 Cable
130 Excitation circuit 131 Amplification circuit
132 AD converter 137 Display means
138 Input means 139 Computer
140 Portable information equipment 141 Interface circuit
142 Internet 143 Envelope waveform
144a, 144b Composite waveform
A Tightened member
B bolt
C fixed part

Claims (6)

The movable body is connected to the base body so as to be linearly driven, and a torque generator having at least a servomotor and a speed reducer is mounted on a holding frame provided on the movable body, and one end is engaged with a bolt head. A cylindrical socket body provided with an engaging hole and having the other end opened is rotatably mounted with the drive shaft of the torque generator shifted from the shaft center, and the drive shaft and the socket body are rotated by a rotation transmission mechanism. A probe having a vibration generator which is connected and longitudinally vibrates the bolt head by electromagnetic force and a vibration detector which detects this longitudinal vibration, converts it into a signal and outputs the signal, wherein at least the vibration detector is the socket body The probe is attached to a movable member that can be linearly driven with respect to the movable body, and the probe is brought into contact with a bolt head engaged with an engagement hole of the socket body. Axial force meter nut runner, characterized by measuring the axial force Te. The nut runner with an axial force meter according to claim 1, wherein the rotation transmission mechanism is formed by meshing a first gear fixed to the drive shaft with a second gear provided on an outer periphery of the socket body. The nut runner with an axial force meter according to claim 1 or 2, wherein the probe is arranged in a non-contact state inside the socket body. The nut runner with an axial force meter according to any one of claims 1 to 3, wherein a disk having the engagement hole at the center is detachably attached to one end of the socket body. The nut runner with an axial force meter according to any one of claims 1 to 4, wherein a torque sensor is disposed between the speed reducer and the drive shaft on the torque generator. The vibration generator has a through-hole through which a vibration transmission rod can be inserted into the axis, and an annular magnet magnetized so as to have mutually opposite magnetic poles in the axial direction on the radially outer periphery of the through-hole. A plurality of excitation coils are arranged coaxially on the outer circumference or inner circumference of the annular magnet in a plurality of axial directions, and the vibration detector can slide the vibration detector in a cylindrical sleeve in the axial direction. The vibration transmission rod is connected to the vibration detector so as to be able to transmit vibration, and at least both ends of the sleeve are vibrated in a cylindrical casing. 6. A probe having a vibration-absorbing material that absorbs vibration and a probe that has the vibration detection body attached to the tip and exposes the tip of the vibration transmission rod from a through hole thereof. With described axial force meter Nut runner.

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