JP5304630B2 - Fastening torque inspection method and fastening torque inspection system for fastening members - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect inspection tightening torque with a high degree of accuracy when detecting inspection tightening torque of a fastener member, even in the case that the rigidity of a fastener member to be fastened is low and the torque is detected in a low torque range, in a method for inspecting tightening torque of a fastener member. <P>SOLUTION: The method for inspecting the tightening torque includes: a step for retightening a bolt with an automatic tightening mechanism, while detecting a tightening torque T and a tightening angle &theta; in the retightening operation; a step for acquiring a tightening angle differential value characteristic from the detected T and &theta;, which represents dT/d&theta;; and a step for acquiring an inspection tightening torque Tm based on the tightening torque that corresponds to the case that the acquired tightening angle differential value characteristic has a characteristic, in which dT<SP>2</SP>/d<SP>2</SP>&theta; is negative, and dT/d&theta; is a prescribed differential value that is 0 or approximate 0. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a tightening torque inspection method and a tightening torque inspection system that detect a tightening torque and a tightening angle when tightening a tightening member, and acquire an inspection tightening torque from the detected tightening torque and tightening angle.

  Conventionally, as a method of inspecting the torque value of a bolt, which is a fastening member in a tightened state, the tightened bolt is further tightened with a torque wrench, and the torque value when the bolt starts moving again (restarts) A retightening torque method that is read by a torque wrench is known.

  Further, in Patent Document 1, for an additional tightening inspection which is considered to obtain an accurate bolt fastening torque by correcting an error caused by a torque wrench rotating before the inspection bolt rotates. A torque wrench is described. This additional tightening inspection torque wrench has a means for detecting torque at the time of bolt tightening, a means for detecting the rotation angle of the torque wrench, and the torque and rotation angle detected by the detection means as input information. Based on the input information obtained in the stable region after rotation and the torsion characteristic gradient line set as a reference in advance, a torque gradient line in the rotation state of the bolt is virtually assumed and obtained before the bolt rotates. The obtained torque gradient line in the bolt stationary state is assumed, and the torque value at the intersection of the two torque gradient lines is set as the measured torque value.

  Further, the screw fastening torque measuring method described in Patent Document 2 starts the tightening of the fastening screw with a torque wrench, and the tightening torque is stable while the torque wrench reaches the desired rotation angle from the additional tightening start point. Then, the rising torque gradient characteristic is detected, and the tightening torque at the start of tightening tightening of the fastening screw is calculated based on the torque gradient characteristic.

  Further, Patent Document 3 describes a nutrunner inspection method that has been considered to maintain work efficiency in the tightening process and to ensure the reliability of the inspection result. In this inspection method, the bolt is tightened to the set torque with the first nut runner, and then tightened with the second nut runner, and the set torque with the first nut runner is compared with the tightening torque with the second nut runner. It is said that a nut runner abnormality is detected when the torque difference is equal to or greater than the allowable torque.

  Further, the bolt fastening method described in Patent Document 4 obtains a state of a torque characteristic line indicating a change in tightening torque accompanying a change in the tightening angle during bolt tightening by the nut runner, and the torque characteristic line is linear. When the determination is made, the bolt is tightened from the theoretical seating point obtained based on the torque gradient until the first set angle set in advance is reached to obtain the target tightening axial force. Further, in Patent Document 4, a torque characteristic line that is a tightening torque and a tightening angle line based on the detection data of the tightening torque and the tightening angle is obtained, a theoretical seating point is obtained based on the data, and a tightening with reference to the theoretical seating point is performed. The angle is related to the tightening torque, and the tightening is stopped when the initial tightening angle is reached with reference to the theoretical seating point. Further, when the torque characteristic line is in a straight line state, the tightening is resumed by an angle that is insufficient to perform the tightening by the seating point angle method.

  In Patent Document 5, the bolt is tightened to a snag torque with a nut runner, then tightened at a specified tightening angle, then the bolt is loosened, and then tightened and tightened again. The starting torque is measured, and the phase calculation unit calculates the phase between the tightening angle and the reference torque.

JP 2002-120162 A JP 2000-778 JP-A-8-90362 JP 2009-83025 A Japanese Patent No. 4075852

  In the case of the torque wrench and the screw fastening torque measuring method described in Patent Documents 1 and 2 above, the tightening torque is calculated using the torque wrench. It is difficult to accurately measure the tightening torque due to “side factors” and “operator factors”. Examples of the “work factor” include deformation of the work, play of the work, and dimensional variations. Further, “factors on the tightening means side” include, for example, deformation of the tightening means, shading of the socket, dimensional variation of the socket, and the like. In addition, as “worker factors”, there are variations in the tightening speed by the worker at the time of additional tightening inspection, torque fluctuations due to variations in the pressing force of the torque wrench at the time of additional tightening, and the like.

  In particular, in the case of the torque wrench and the screw fastening torque measuring method described in Patent Documents 1 and 2, when the tightening torque is in a low torque region such as 4 Nm or less, The ratio of the torque fluctuation due to the work variation of the operator to the total torque fluctuation including the torque fluctuation due to other factors increases. For this reason, it becomes more difficult to detect the tightening torque with accuracy in the low torque region. For example, “Torque wrench CTB for tightening inspection” (trade name) manufactured by Tohnichi Seisakusho Co., Ltd. has a measurement range of inspection torque of 4 Nm or more, and is measured at a substantially lower torque range of less than 4 Nm. That is excluded. When the torque wrench is used in this way, since the workers individually inspect, variation due to individual differences among the workers occurs, and it is difficult to detect the tightening torque with high accuracy.

  Further, in the case of the nut runner inspection method described in Patent Document 3, it is possible to eliminate the influence of the above-described operator factors. However, as described in, for example, FIG. 4 of Patent Document 3, the ratio ΔT / Δθ between the minute change amount Δθ of the tightening angle and the minute change amount ΔT of the torque value is greater than a predetermined value when tightening the bolt. Is also increased, the bolt is rotated in the tightening direction by the minute tightening angle Δθb from that point, and the torque value at that time is detected as the tightening torque value. In this case, in actuality, since there is rattling or deformation in the work or the tightening means, ΔT / Δθ increases and does not rise suddenly during tightening. For this reason, it is difficult to accurately obtain the additional tightening torque value that is the inspection tightening torque. Further, since the additional tightening torque value is excessively tightened by the minute tightening angle Δθb at the time of additional tightening, the inspection tightening torque is output to be higher by the torque corresponding to the minute tightening angle Δθb. That is, Patent Document 3 assumes an ideal state in which the deformation and backlash of the workpiece and the fastening means can be ignored. For this reason, it is not realistic and it is difficult to measure the tightening torque with high accuracy. In particular, it becomes more difficult to measure the tightening torque with high accuracy when the rigidity of a fastened member such as a workpiece is low.

  Under such circumstances, the present inventor can detect the inspection tightening torque with high accuracy even when detecting the inspection tightening torque of the tightened fastening member even if the workpiece has low rigidity and is detected in a low torque region. Therefore, a method and an apparatus for detecting the inspection tightening torque using the first-order differential value according to the tightening torque and the twice differential value due to the tightening torque are considered. Further, neither Patent Document 4 nor Patent Document 5 discloses such a detection method, a detection device, and a configuration suggesting them.

  The present invention relates to a method for detecting a tightening torque of a fastening member and a system for detecting a tightening torque when detecting a tightening torque of a fastening member and detecting a tightened member such as a work piece in a low torque region with low rigidity. However, the purpose is to make it possible to detect the inspection tightening torque with high accuracy.

  The tightening member tightening torque inspection method according to the present invention is a method of inspecting a tightening member inspection tightening torque, and further tightening the tightening member with an automatic tightening mechanism and detecting a tightening torque and a tightening angle at the time of additional tightening. A first obtaining step for obtaining a tightening angle differential value characteristic obtained by differentiating the tightening torque from the tightening torque detected from the tightening torque and the tightening angle detected by the control unit, and the control unit, In the acquired tightening angle differential value characteristic, the second-order differential value due to the tightening torque tightening angle is negative, and the first-order differential value due to the tightening torque tightening angle is 0 or a predetermined set differential value near zero. Based on the corresponding tightening torque or the corresponding tightening angle, which is the acquired value of A tightening torque inspection method of the fastening member, characterized in that it comprises a second acquisition step of acquiring 査 tightening torque.

  According to the tightening torque inspection method for a fastening member according to the present invention, when detecting the inspection tightening torque of the fastening member, the rigidity of the fastened member to be tightened by the fastening member is low and even when detecting in a low torque region. Inspection tightening torque can be detected accurately. That is, the fastening member is further tightened by the automatic tightening mechanism, and the inspection tightening torque is acquired from the detected values of the tightening torque and the tightening angle at the time of the additional tightening. Can be eliminated. In addition, the inspection tightening is based on the acquired value when the first-order differential value according to the tightening angle of the tightening torque becomes 0 or a predetermined set differential value near zero and the second-order differential value according to the tightening angle of the tightening torque is negative. Since the torque is detected, the ratio ΔT / Δθ between the minute change amount Δθ of the tightening angle and the minute change amount ΔT of the torque value is different from the nut runner inspection method described in Patent Document 3 above. The torque at the above time is not obtained, and the inspection tightening torque can be obtained with high accuracy in accordance with the actual state.

  In the tightening torque inspection method according to the present invention, preferably, the second acquisition step is a tightening angle differential value characteristic acquired by the control unit, and a second-order differential value due to the tightening angle of the tightening torque is negative, and The corresponding tightening torque is acquired as the inspection tightening torque when the first-order differential value according to the tightening angle of the tightening torque is 0 or a predetermined set differential value near zero.

  In the tightening torque inspection method according to the present invention, preferably, the second acquisition step is a tightening angle differential value characteristic acquired by the control unit, and a second-order differential value due to the tightening angle of the tightening torque is negative, and The virtual tightening angle acquisition step for acquiring the corresponding virtual tightening angle when the first-order differential value based on the tightening angle of the tightening torque is 0 or a predetermined set differential value near 0, and the virtual tightening angle by the control unit From the first angle obtained when the fluctuation range of the first-order differential value is within the predetermined range from the increase of the predetermined first angle set in advance to the predetermined second angle larger than the first angle. Tightening corresponding to the intersection of the slope line of the tightening torque up to two angles and the characteristic line representing the relationship between the tightening torque and the tightening angle Paste torque, and a test tightening torque obtaining step obtaining a test tightening torque.

  According to said structure, a test | inspection fastening torque can be calculated | required more accurately with respect to the fastening member in a stationary state using a more stable dynamic friction coefficient.

  The tightening torque inspection system according to the present invention is a tightening torque inspection system used in the tightening member tightening torque inspection method according to the present invention, and includes an automatic tightening mechanism for tightening the tightening member and a tightening by the automatic tightening mechanism. A control unit including torque detecting means for detecting tightening torque at the time of additional tightening of the member, angle detection means for detecting the tightening angle at the time of additional tightening of the fastening member by the automatic tightening mechanism, and a first acquisition means and a second acquisition means The first acquisition means acquires a tightening angle differential value characteristic obtained by differentiating the tightening torque with the tightening angle from the detected tightening torque and tightening angle, and the second acquisition means is acquired The second-order differential value due to the tightening angle of the tightening torque is negative and the tightening angle differential value characteristics are Acquiring the inspection tightening torque based on the corresponding tightening torque or the corresponding tightening angle, which is an acquired value when the first-order differential value based on the tightening angle of the tightening torque is 0 or a predetermined set differential value near zero. A tightening torque inspection system characterized by

  In the tightening torque inspection system according to the present invention, preferably, the second acquisition unit is a tightening angle differential value characteristic acquired by the first acquisition unit, and a second-order differential value due to the tightening angle of the tightening torque is negative, And the corresponding tightening torque when the first-order differential value by the tightening angle of the tightening torque becomes a predetermined set differential value of 0 or near 0 is acquired as the inspection tightening torque.

  In the tightening torque inspection system according to the present invention, preferably, the second acquisition unit is a tightening angle differential value characteristic acquired by the first acquisition unit, and a second-order differential value due to the tightening angle of the tightening torque is negative, In addition, when the first-order differential value based on the tightening angle of the tightening torque is 0 or a predetermined set differential value near zero, virtual tightening angle acquisition means for acquiring the corresponding virtual tightening angle, and preset from the virtual tightening angle From the first angle to the second angle obtained when the fluctuation range of the first-order differential value is within the predetermined width after increasing the predetermined first angle until reaching the predetermined second angle larger than the first angle. The tightening torque corresponding to the intersection of the slope line of the tightening torque and the characteristic line representing the relationship between the tightening torque and the tightening angle And a test tightening torque obtaining means for obtaining as the test tightening torque.

  According to the fastening torque inspection method and the fastening torque inspection system according to the present invention, when detecting the inspection fastening torque of the fastening member, the rigidity of the fastening member such as a workpiece is low and is detected in a low torque region. Even when doing so, the inspection tightening torque can be detected with high accuracy.

It is a lineblock diagram showing the bolting torque inspection system of a 1st embodiment concerning the present invention. It is the schematic which shows the nut runner which comprises the clamping torque test | inspection system of FIG. It is a block diagram which shows the fastening torque calculation apparatus which comprises the fastening torque test | inspection system of FIG. It is a flowchart which shows the fastening torque test | inspection method of 1st Embodiment. The figure for demonstrating the method of calculating a test | inspection tightening torque using the characteristic line a of the torque angle characteristic showing the tightening torque and the tightening angle, and the characteristic line b of the tightening angle differential value characteristic according to the first embodiment. is there. It is a block diagram which shows the fastening torque calculation apparatus which comprises the fastening torque test | inspection system of 2nd Embodiment which concerns on this invention. It is a flowchart corresponding to the step of S16 of FIG. 4 which shows the fastening torque test | inspection method of 2nd Embodiment. It is a figure for demonstrating the method of calculating a test | inspection fastening torque using the characteristic line a of the torque angle characteristic showing fastening torque and a fastening angle, and the characteristic line b of a fastening angle differential value characteristic by 2nd Embodiment. is there.

[First Embodiment]
Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. 1 to 5 show a first embodiment according to the present invention. As shown in FIG. 1, the tightening torque inspection system according to the present embodiment inspects a tightening torque by tightening an inspection tightening torque on a bolt or nut (not shown) that is a fastening member fastening a work (not shown) that is a member to be fastened. Use it in the way you want. Such a tightening torque inspection system includes an automatic tightening mechanism 10 and a tightening torque calculation device 12 serving as a control unit. In addition, the “tightening method” means that a fastening member such as a workpiece is fastened by a fastening member, and a bolt or nut that is in a stationary state is further tightened to further tighten and the fastening member is rotated again. This is a method of obtaining the torque value at the time as the inspection tightening torque.

  The automatic tightening mechanism 10 includes a nut runner 14 that tightens and tightens a bolt (the same applies to a nut), and a nut runner controller 16 that controls the operating state of the nut runner 14. The tightening torque calculation device 12 is constituted by a personal computer, for example, a tightening data collection system, and includes a tightening torque angle data storage unit 18, a tightening torque calculation algorithm storage unit 20, a calculation unit 22, and an input (not shown). Output device. For this reason, the tightening torque calculation device 12 includes a storage unit such as a memory or a hard disk drive (HDD) and a calculation unit 22 for configuring the tightening torque angle data storage unit 18 and the tightening torque calculation algorithm storage unit 20. CPU for performing.

  As shown in FIG. 2, the nut runner 14 includes a socket 24 that can be engaged with a bolt head (not shown), a torque sensor 28 that is a torque detection means that detects a tightening torque of the bolt, and a drive that rotationally drives the socket 24. The motor 30 and the angle sensor 32 which is an angle detection means which detects the fastening angle which is a rotation angle of the volt | bolt or the socket 24 are included. That is, the torque sensor 28 detects the tightening torque when the bolt is tightened by the automatic tightening mechanism 10. Further, the angle sensor 32 detects a tightening angle when the bolt is tightened by the automatic tightening mechanism 10. The angle sensor 32 is configured by an encoder or the like. Such a nut runner 14 is installed in an automatic fastening facility (not shown). The support portion that supports the nutrunner 14 can also be moved up and down or moved horizontally.

  The detection values of the torque sensor 28 and the angle sensor 32 are input to the tightening torque calculation device 12 (FIG. 1). That is, signals representing the tightening torque and the tightening angle detected by the torque sensor 28 and the angle sensor 32 are transmitted through the nut runner controller 16 through the nut runner controller 16 as shown in FIG. Data is collected in the data storage unit 18 and saved, that is, stored. The tightening torque calculation algorithm storage unit 20 stores a torque calculation program including a first algorithm described later. The first algorithm is used to calculate, that is, acquire, the inspection tightening torque using the data stored in the tightening torque angle data storage unit 18.

  As shown in FIG. 3, the tightening torque calculation device 12 includes a first acquisition unit 34 and a second acquisition unit 36. The functions of the first acquisition unit 34 and the second acquisition unit 36 can be realized by elements including the tightening torque angle data storage unit 18, the tightening torque calculation algorithm storage unit 20, and the calculation unit 22 illustrated in FIG. 1. The first acquisition unit 34 reads the detected tightening torque and tightening angle stored in the tightening torque angle data storage unit 18, and uses the read tightening torque and tightening angle to characterize the tightening torque and tightening angle. A first characteristic line (a in FIG. 5) representing the torque angle characteristic, and a second characteristic line (b in FIG. 5) representing the tightening angle differential value characteristic obtained by differentiating the tightening torque with the tightening angle. Is obtained, that is, calculated.

  Further, the second acquisition means 36 shown in FIG. 3 is a second characteristic line representing the acquired tightening angle differential value characteristic, the second order differential value due to the tightening angle of the tightening torque becomes negative, and the tightening angle of the tightening torque. The inspection tightening torque is calculated based on the corresponding tightening torque, which is an acquired value when the first-order differential value obtained by the above becomes a predetermined set differential value of 0 or near 0, that is, acquired. That is, the second acquisition means 36 has the tightening angle differential value characteristic acquired by the first acquisition means 34, the second-order differential value due to the tightening torque tightening angle becomes negative, and the first-order differential according to the tightening torque tightening angle. The corresponding tightening torque Tm when the value becomes a predetermined set differential value of 0 or near 0 is calculated as the inspection tightening torque Tm. The calculated inspection tightening torque Tm is output to a display or the like that is an output unit of the input / output device, that is, displayed, or this inspection tightening torque Tm is used to determine the quality of the tightening unit. For example, when determining the quality of the tightening portion, the deviation from the reference value Ta is equal to or greater than a predetermined threshold value by comparing the acquired inspection tightening torque Tm with a predetermined reference value Ta. In the case, it is determined as abnormal, and in other cases, it is determined as normal, and a display corresponding to each is displayed on the display of the input / output device. For example, when it is determined that there is an abnormality, a warning sound can be generated or a warning light can be turned on.

  Next, a method for inspecting the inspection tightening torque Tm using such a tightening torque inspection system will be described with reference to the flowchart shown in FIG. In the following description, the same elements as those shown in FIGS. 1 to 3 are denoted by the same reference numerals. First, in step S10 (hereinafter, step will be described simply as S), the nut 24 is used to engage the socket 24 with the bolt head tightening the workpiece and drive the drive motor 30. Then, tighten the bolts. In this case, for example, the workpiece is previously tightened with a bolt with a set target tightening torque (for example, 2 Nm). This additional tightening step is terminated when the bolt is tightened to a preset tightening angle threshold or when the bolt is tightened to a preset tightening torque threshold.

  The nut runner controller 16 and the tightening torque calculation device 12 are linked to each other, and the nut runner 14 is driven by a user operation using an input unit (not shown) provided in the nut runner controller 16 or the tightening torque calculation device 12. The nutrunner controller causes the torque sensor 28 and the angle sensor 32 to detect the tightening torque and the tightening angle when the bolt is tightened in increments of a predetermined tightening angle, and the detected tightening torque and tightening angle are determined as the tightening torque. The torque is output to the tightening torque angle data storage unit 18 of the calculation device 12. Further, the tightening torque calculation device 12 is activated and a predetermined operation is performed using the input unit, whereby a first torque calculation program including a first algorithm is executed. In such a step of S10 in FIG. 4, a bolt is tightened by the automatic tightening mechanism 10 and a “detection step” is performed for detecting a tightening torque and a tightening angle at the time of the additional tightening.

  In S12, the tightening torque calculation device 12 uses all the tightening torque and the tightening angle detected from the start of tightening the bolt to the end of the additional tightening as data, and the tightening torque angle data storage unit 18 of the tightening torque calculating device 12 is used. The “memory step” is stored. 4, after all the tightening torques and the tightening angles are detected, the tightening torque angle data storage unit 18 of the tightening torque calculation device 12 stores them. However, the tightening torque and the tightening angle are detected when the bolt is tightened at a certain increment of each tightening angle, and the detected tightening torque and the tightening angle are stored in the tightening torque angle data storage unit 18. Can be performed simultaneously. That is, the detection step of S10 and the storage step of S12 in FIG. 4 can be combined into a “detection storage step”.

  Next, in S14, the first acquisition unit 34 of the tightening torque calculation device 12 reads the detected tightening torque and tightening angle from the tightening torque angle data storage unit 18, and uses the read tightening torque and tightening angle to generate torque. A first characteristic line (a in FIG. 5) representing the angle characteristic and a second characteristic line (b in FIG. 5) representing the tightening angle differential value characteristic obtained by differentiating the tightening torque with the tightening angle are acquired. A first acquisition step is performed. In FIG. 5, the value of the first characteristic line a is indicated by the left vertical axis. The right vertical axis indicates the value of the second characteristic line b (the same applies to FIG. 8 described later).

  Next, in S16, the second acquisition means 36 of the tightening torque calculation device 12 has the acquired tightening angle differential value characteristic, the second-order differential value due to the tightening angle of the tightening torque becomes negative, and the tightening torque depends on the tightening angle of the tightening torque. A second acquisition step of acquiring the inspection tightening torque is performed based on the corresponding tightening torque, which is an acquired value when the first-order differential value becomes a predetermined set differential value of 0 or near zero. That is, in the second acquisition step, the tightening torque calculation device 12 has the acquired tightening angle differential value characteristic, the second order differential value due to the tightening angle of the tightening torque becomes negative, and the first order differential according to the tightening angle of the tightening torque. The corresponding tightening torque Tm when the value is a predetermined set differential value of 0 or near 0 is acquired as the inspection tightening torque Tm. Thus, after tightening the bolt with the automatic tightening mechanism 10 and storing the data representing all detected tightening torques and detected tightening angles in the tightening torque calculating device 12, the inspection tightening torque Tm is inspected. The first acquisition step (S14) and the second acquisition step (S16) are executed by the first algorithm.

Such a first algorithm is a method for obtaining the “inspection tightening torque Tm” from the “inflection point” or the “inflection point” of the first characteristic line a representing the torque angle characteristic relating to the tightening torque. . This inflection point is the starting point when bolts are tightened. Therefore, in this embodiment, since this inflection point is obtained with high accuracy, the inspection tightening torque can also be obtained with high accuracy. More specifically, referring to FIG. 5, the second acquisition unit 36 has a second characteristic line b where, for example, dT / dθ = 0, which is a first-order differential value according to the tightening angle of the tightening torque. If A is present, whether or not the slope of point A is negative, that is, at point A, d ² T / dθ ² , which is the second-order differential value according to the tightening angle of the tightening torque, becomes negative (d ² It is determined whether or not T / dθ ² <0). In the determination, if it is determined that d ² T / dθ ² is negative, it is determined that the inclination of the second characteristic line b with respect to the tightening angle θ is negative. Then, the tightening torque Tm at the tightening angle θa at the point A is calculated from the first characteristic line a, and the calculated tightening torque Tm is acquired as the inspection tightening torque Tm.

On the other hand, there may be a case where there is no point A where dT / dθ = 0 on the second characteristic line b. For this purpose, in the present embodiment, a predetermined set differential value Q1 near 0 (for example, an arbitrary set value of 0.05 or less) is set in advance by the first algorithm. When the second acquisition unit 36 determines that there is no point A where dT / dθ = 0 in the second characteristic line b, dT / dθ is equal to the set differential value Q1 that is a specified value ( An alternative point A in the case of dT / d = Q1) is obtained, and the alternative point A is assumed to be a point substantially equivalent to the inflection point. Similarly to the above, the second acquisition unit 36 has a negative slope at the alternative point A of the second characteristic line b, that is, the second-order differential value according to the tightening angle of the tightening torque at the alternative point A. , D ² T / dθ ² is negative (d ² T / dθ ² <0), the tightening torque at the tightening angle θa at the alternative point A is calculated from the first characteristic line a. The calculated tightening torque Tm is acquired as the inspection tightening torque Tm. In FIG. 5, the tightening torque Tm at the alternative point A is shown.

  In S18, the tightening torque calculation device 12 compares the inspection tightening torque Tm with a preset reference value Ta, and performs a pass / fail determination step for determining whether the tightening torque of the tightening portion is good. For example, when the deviation between the acquired inspection tightening torque Tm and the reference value Ta is greater than or equal to a preset threshold value, it is determined to be abnormal, otherwise it is determined to be normal, and the display as an output unit, etc. Then, the display corresponding to each is displayed. Note that the pass / fail judgment step of S18 may be omitted.

  According to the present embodiment, when detecting the inspection tightening torque of the bolt, when detecting in a low torque region where the rigidity of the workpiece, which is a member to be tightened by the bolt, is low and, for example, 4 Nm or less. However, the inspection tightening torque can be detected with high accuracy. That is, the bolt is tightened by the automatic tightening mechanism 10 and the inspection tightening torque Tm is acquired from the detected values of the tightening torque and the tightening angle at the time of the additional tightening. Factors can be eliminated. Moreover, since the tightening torque angle data storage unit 18 and the tightening torque calculation algorithm storage unit 20 are further provided in the configuration including the automatic tightening mechanism 10, the tightening torque Tm is inspected after the automatic tightening mechanism 10 automatically tightens the bolt. can do.

  In addition, since the tightening torque calculation device 12 calculates the inspection tightening torque Tm after all the data of the detected values of the tightening torque and the tightening angle are stored in the tightening torque angle data storage unit 18, the same stored data is used. However, the inspection tightening torque can be calculated using another algorithm such as a second algorithm used in the second embodiment described later, which is different from the first algorithm. For this reason, it is possible to calculate the inspection tightening torque Tm using an optimal algorithm according to the type of workpiece. In addition, such an algorithm can be easily changed. In addition, when it is determined that the tightening torque is good or bad and it is determined that there is an abnormality, it is easy to investigate the cause of the occurrence of the problem by analyzing the stored data of the tightening torque and the tightening angle.

In the present embodiment, the first-order differential value dT / dθ depending on the tightening angle of the tightening torque becomes a predetermined set differential value Q of 0 or near zero, and the twice-differentiated value d ² T depending on the tightening angle of the tightening torque. The inspection tightening torque Tm is detected based on the acquired value when / dθ is negative. Therefore, as in the method for inspecting the nutrunner 14 described in Patent Document 3 above, the ratio ΔT / Δθ between the minute change amount Δθ of the tightening angle and the minute change amount ΔT of the torque value is predetermined when the bolt is tightened. Unlike the case where the bolt is rotated in the tightening direction by a small tightening angle Δθb from that point and the torque value at that time is detected as the tightening torque value, the detection tightening torque detection accuracy is increased. it can. That is, in the case of such a method of Patent Document 3, an ideal state is assumed in which there is no rattling or deformation in the workpiece or the fastening means. It cannot be ignored. For this reason, ΔT / Δθ does not rise suddenly during retightening, and it is difficult to accurately obtain the inspection tightening torque. On the other hand, in the present embodiment, the torque when ΔT / Δθ is equal to or greater than a predetermined value is not obtained, but is substantially the same as the inflection point or the inflection point of the second characteristic line b representing the tightening angle differential value characteristic. Based on the acquired value at the point, that is, the tightening torque, the inspection tightening torque Tm corresponding to the movement start point at the time of additional tightening of the bolt can be obtained with high accuracy in accordance with the actual state.

  In the present embodiment, the present invention is not limited to obtaining the inspection tightening torque Tm when tightening the bolt, but the inspection tightening torque when tightening the nut to the bolt can also be obtained. Further, when the target member is a bolt and the fastening member is a nut with a friction stabilizer, the inspection tightening torque of the nut when the target tightening torque is 2 Nm, for example, can be obtained.

[Second Embodiment]
FIG. 6 is a block diagram showing a tightening torque calculation device constituting the tightening torque inspection system according to the second embodiment of the present invention. FIG. 7 is a flowchart corresponding to step S16 of FIG. 4 showing the tightening torque inspection method of the second embodiment. FIG. 8 illustrates a method for calculating the inspection tightening torque using the characteristic line a of the torque angle characteristic representing the tightening torque and the tightening angle and the characteristic line b of the tightening angle differential value characteristic according to the second embodiment. FIG.

  In the first embodiment, the “inclination point” of the second characteristic line b (see FIG. 5) representing the tightening angle differential value characteristic, or the “tightening torque” at a point substantially equivalent to the inflection point, This was acquired as “inspection tightening torque Tm”. On the other hand, in the present embodiment, the corresponding “tightening angle”, which is an inflection point of the second characteristic line b (FIG. 8) representing the tightening angle differential value characteristic or an acquired value at a point substantially equivalent to the inflection point. ”To obtain“ inspection tightening torque Tm ′ ”. In this case, the “inspection tightening torque Tm ′” is the intersection of the gradient line in the “slope stable region” of the first characteristic line a (FIG. 8) representing the torque angle characteristic and the other part of the first characteristic line a. Ask from.

  Therefore, as shown in FIG. 6, in the tightening torque inspection system used in the present embodiment, the second acquisition means 36 included in the tightening torque calculation device 12 includes a virtual tightening angle acquisition means 38 and an inspection tightening torque acquisition means. 40. The virtual tightening angle acquisition means 38 is the tightening angle differential value characteristic acquired by the first acquisition means 34, the second order differential value due to the tightening angle of the tightening torque becomes negative, and the first order differential value due to the tightening angle of the tightening torque. The corresponding virtual tightening angle is acquired when becomes a predetermined differential value of 0 or near 0.

  Further, the inspection tightening torque acquisition means 40 has a fluctuation range of the first-order differential value from increasing the predetermined first angle preset from the virtual tightening angle to reaching a predetermined second angle larger than the first angle. A gradient line R with respect to the tightening angle of the tightening torque from the first angle to the second angle obtained when it is within the predetermined width, and a first characteristic line a (FIG. 8) representing the relationship between the tightening torque and the tightening angle. The tightening torque corresponding to the intersection is acquired as the inspection tightening torque Tm ′. Further, the tightening torque calculation algorithm storage unit 20 (see FIG. 1) stores a torque calculation program including a second algorithm described later.

  Next, a method for inspecting the inspection tightening torque using such a tightening torque inspection system will be described using the flowchart shown in FIG. 7 with reference to the flowchart shown in FIG. In the following description, the same elements as those shown in FIGS. 1 to 3 and FIG. 6 representing the first embodiment are denoted by the same reference numerals. The flowchart in FIG. 7 corresponds to the step S16 in the flowchart in FIG. 4, and the steps before S20 are the same as the steps from S10 to S14 in FIG. For example, in S14 (FIG. 4), the first acquisition unit 34 of the tightening torque calculation device 12 uses the detected tightening torque and the tightening angle, and the first characteristic line (a in FIG. 8) representing the torque angle characteristic. Then, a first acquisition step of acquiring a second characteristic line (b in FIG. 8) representing the tightening angle differential value characteristic obtained by differentiating the tightening torque with the tightening angle is performed. Then, after the end of the first acquisition step, when the process proceeds to the inspection tightening torque acquisition step of S16 (FIG. 4), the process proceeds to steps S20 and S22 of FIG.

  In S20 and S22, the second acquisition means 36 has the acquired tightening angle differential value characteristic, the second-order differential value due to the tightening torque tightening angle is negative, and the first-order differential value due to the tightening torque tightening angle is zero. Alternatively, a second acquisition step of acquiring the inspection tightening torque Tm based on the corresponding tightening angle, which is an acquired value when the predetermined set differential value near 0 is obtained, is performed. That is, the second acquisition step includes a virtual tightening angle acquisition step of S20 and an inspection tightening torque acquisition step of S22. In the virtual tightening angle acquisition step of S20, the virtual tightening angle acquisition means 38 has the acquired tightening angle differential value characteristic, the second-order differential value due to the tightening angle of the tightening torque becomes negative, and 1 according to the tightening angle of the tightening torque. The corresponding tightening angle is acquired when the floor differential value is a predetermined set differential value of 0 or near 0.

  Further, in the inspection tightening torque acquisition step of S22, the inspection tightening acquisition means 40 increases the predetermined first angle set in advance from the virtual tightening angle until reaching the predetermined second angle larger than the first angle. A first characteristic representing the relationship between the tightening torque and the tightening angle, and the gradient line R with respect to the tightening angle of the tightening torque from the first angle to the second angle obtained when the fluctuation range of the first-order differential value is within a predetermined range. The tightening torque Tm ′ corresponding to the intersection with the line a (FIG. 8) is acquired as the inspection tightening torque Tm ′. The first acquisition step of acquiring the tightening angle differential value characteristic and the second acquisition step of acquiring the inspection tightening torque Tm ′ are executed by the second algorithm.

As shown in FIG. 8, the second algorithm has a gradient line R in the “slope stable region” (region from angle θb to θb + Δθ2) of the first characteristic line a representing the torque angle characteristic, and the first characteristic. This is a method for obtaining the “inspection tightening torque Tm ′” from the intersection B with the other part of the line a, that is, the region where the tightening angle θ is small. Specifically, as the “virtual tightening angle acquisition step” (S20), the virtual tightening angle acquisition unit 38 is a second characteristic line b, for example, dT / dθ, which is a first-order differential value according to the tightening angle of the tightening torque. If there is a point A where = 0, whether or not the slope of the point A is negative, that is, at the point A, d ² T / dθ ² , which is a second-order differential value according to the tightening angle of the tightening torque, is negative It is determined whether or not (d ² T / dθ ² <0). If it is determined that d ² T / dθ ² is negative, the tightening angle θa at the point A is calculated as “virtual tightening angle θa” from the first characteristic line a, that is, acquired.

On the other hand, when there is no point A where dT / dθ = 0 on the second characteristic line b, as in the first embodiment, a predetermined value near 0 where dT / dθ is a specified value. An alternative point A that is equal to the set differential value Q2 (for example, an arbitrary set value of 0.3 or less) is obtained. Assuming that the alternative point A is a point substantially equivalent to the inflection point, the inclination of the second characteristic line b at the alternative point A is negative, that is, the tightening torque at the alternative point A, as described above. When d ² T / dθ ² , which is a second-order differential value depending on the tightening angle of (b), is determined to be negative (d ² T / dθ ² <0), the first characteristic line a is replaced with the alternative point A. Are obtained as “virtual fastening angles”. In FIG. 5, the tightening torque Tm at the alternative point A is shown.

  Further, as the “inspection tightening torque acquisition step” (S22), the inspection tightening torque acquisition means 40 starts from the first angle θb increased by a predetermined angle Δθ1 preset from the virtual tightening angle θa on the second characteristic line b. Then, it is determined whether or not the fluctuation range of the one-time differential value dT / dθ until the predetermined second angle (θb + Δθ2) larger than the first angle θb is within the predetermined width W. Then, a gradient line R with respect to the tightening angle of the tightening torque at the first characteristic line a from the first angle θb to the second angle (θb + Δθ2) obtained when it is determined that the fluctuation range is within the predetermined width W is obtained. . The gradient line R is a straight line passing through the point of the first angle θb and the point of the second angle (θb + Δθ2) on the first characteristic line a. Then, the tightening torque Tm ′ corresponding to the intersection B of the gradient line R extended to the small tightening angle region side and the first characteristic line a representing the relationship between the tightening torque and the tightening angle is set as the inspection tightening torque Tm ′. Get as. That is, the tightening torque Tm ′ at the intersection B obtained by extrapolating the line segment of the gradient line R from the first angle θb to the second angle (θb + Δθ2) to the small tightening angle region side of the first characteristic line a is obtained. Obtained as inspection tightening torque Tm ′.

  After such an inspection tightening torque acquisition step is completed, the process proceeds to S18 in FIG. 4 and a tightening torque quality determination step is performed. Also in this embodiment, the tightening torque quality determination step can be omitted.

  According to the present embodiment as described above, it is possible to detect the inspection tightening torque of the bolt or nut with higher accuracy than in the first embodiment. That is, in the first embodiment described above, the inspection tightening torque Tm is detected using the torque generated by the dynamic friction coefficient at the time of tightening the bolt (or nut, hereinafter the same). However, since the bolt is actually in a static state with a torque generated by the static friction coefficient, it cannot be said that there is a possibility that the inspection tightening torque Tm will be slightly higher because the friction coefficient differs from the dynamic friction coefficient. On the other hand, this embodiment also uses the dynamic friction coefficient, but uses the slope of the stable region of the first characteristic line a, and the slope line R having this slope and the bolt are in the stationary state. The inspection tightening torque Tm ′ is obtained from the intersection B of the characteristic line a with the small tightening angle region side. For this reason, unlike the case of the first embodiment, the inspection tightening torque Tm ′ can be obtained with higher accuracy by using a more stable dynamic friction coefficient for a bolt in a stationary state. Since other configurations and operations are the same as those of the first embodiment, overlapping illustrations and descriptions are omitted.

DESCRIPTION OF SYMBOLS 10 Automatic tightening mechanism, 12 Tightening torque calculation apparatus, 14 Nutrunner, 16 Nutrunner controller, 18 Tightening torque angle data storage unit, 20 Tightening torque calculation algorithm storage unit, 22 Arithmetic unit, 24 socket, 28 Torque sensor, 30 Drive motor, 32 Angle sensor, 34 first acquisition means, 36 second acquisition means, 38 virtual tightening angle acquisition means, 40 inspection tightening torque acquisition means.

Claims (6)

A tightening torque inspection method for inspecting the fastening torque of a fastening member,
A detection step for detecting a tightening torque and a tightening angle at the time of additional tightening while tightening the fastening member by an automatic tightening mechanism;
A first acquisition step of acquiring a tightening angle differential value characteristic obtained by differentiating the tightening torque from the detected tightening torque and tightening angle by the control unit;
The second-order differential value according to the tightening angle of the tightening torque becomes negative and the first-order differential value according to the tightening angle of the tightening torque is 0 or a predetermined set differential in the vicinity of 0 in the acquired tightening angle differential value characteristic by the control unit. And a second acquisition step of acquiring an inspection tightening torque based on a corresponding tightening torque or a corresponding tightening angle, which is an acquired value in the case of a value. In the fastening torque inspection method of the fastening member according to claim 1,
The second acquisition step is
The second-order differential value according to the tightening angle of the tightening torque is negative and the first-order differential value according to the tightening angle of the tightening torque is 0 or a predetermined set differential value near zero in the acquired tightening angle differential value characteristic by the control unit. A tightening torque inspection method for a fastening member, wherein a corresponding tightening torque is obtained as an inspection tightening torque. In the fastening torque inspection method of the fastening member according to claim 1,
The second acquisition step is
The second-order differential value according to the tightening angle of the tightening torque is negative and the first-order differential value according to the tightening angle of the tightening torque is 0 or a predetermined set differential value near zero in the acquired tightening angle differential value characteristic by the control unit. A virtual tightening angle acquisition step of acquiring a corresponding virtual tightening angle when
When the fluctuation range of the first-order differential value from the increase in the predetermined first angle preset from the virtual fastening angle by the control unit to the predetermined second angle larger than the first angle is within the predetermined width The tightening torque corresponding to the intersection of the slope line of the tightening torque obtained from the first angle to the second angle with respect to the tightening angle and the characteristic line representing the relationship between the tightening torque and the tightening angle is acquired as the inspection tightening torque. And a tightening torque inspection method for the fastening member. A tightening torque inspection system used for the tightening torque inspection method for a fastening member according to claim 1,
An automatic tightening mechanism for tightening fastening members;
Torque detecting means for detecting a tightening torque at the time of additional tightening of the fastening member by the automatic tightening mechanism;
An angle detection means for detecting a tightening angle at the time of additional tightening of the fastening member by the automatic tightening mechanism;
A control unit including first acquisition means and second acquisition means,
The first acquisition means acquires a tightening angle differential value characteristic obtained by differentiating the tightening torque with the tightening angle from the detected tightening torque and tightening angle,
The second acquisition means has a predetermined tightening angle differential value characteristic, a second-order differential value due to the tightening angle of the tightening torque is negative, and a first-order differential value due to the tightening angle of the tightening torque is 0 or a predetermined value around zero. A tightening torque inspection system that acquires an inspection tightening torque based on a corresponding tightening torque or a corresponding tightening angle, which is an acquired value when a set differential value is obtained. The tightening torque inspection system according to claim 4,
The second acquisition means is
The tightening angle differential value characteristic acquired by the first acquisition means is a predetermined setting in which the second-order differential value according to the tightening torque is negative and the first-order differential value according to the tightening torque is 0 or near zero. A tightening torque inspection system characterized in that a corresponding tightening torque in the case of a differential value is acquired as an inspection tightening torque. The tightening torque inspection system according to claim 4,
The second acquisition means is
The tightening angle differential value characteristic acquired by the first acquisition means is a predetermined setting in which the second-order differential value according to the tightening torque is negative and the first-order differential value according to the tightening torque is 0 or near zero. A virtual fastening angle acquisition means for acquiring a corresponding virtual fastening angle in the case of a differential value;
The first gain obtained when the fluctuation range of the first-order differential value from the increase of the predetermined first predetermined angle from the virtual fastening angle to the predetermined second angle larger than the first angle is within the predetermined width. Acquiring the inspection tightening torque by acquiring the tightening torque corresponding to the intersection of the gradient line of the tightening torque from the first angle to the second angle with the characteristic line representing the relationship between the tightening torque and the tightening angle as the inspection tightening torque And a tightening torque inspection system.

Images