JP2009255241A - Device for determining presence/absence of foreign matter on screw clamping seat, and determination method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a precise detection in any position from start to end of screw clamping by extracting the presence of a foreign matter on a screw clamping seat from an inclined waveform of clamping torque. <P>SOLUTION: A device for determining presence/absence of a foreign matter on the screw clamping seat is provided with: a torque detecting part 25 for detecting a rotation torque of a nut runner 2 rotated upon rotation of a motor 21; a rotation angle detecting part 26 for detecting a rotation angle of the motor; and an operation processor 5 which performs operation processing of an inclined waveform of clamping torque with respect to a clamping rotation angle, based on individual detection values detected by the torque detecting part and the rotation angle detecting part, performs operation processing of an approximation curve from the inclined waveform and also a function of the approximation curve, and further performs operation processing of a waveform of second-order differential value of the function of the approximation curve, thereby determining that a foreign matter exists on the screw clamping seat when a turning point exists in the waveform of second-order differential value, and determining that a foreign matter does not exist on the screw clamping seat when the turning point does not exist in the waveform of second-order differential value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a foreign matter presence / absence judging device for a screw tightening seat applicable to an automatic screw fastening machine and a method for judging the foreign matter.

  Conventionally, in the tightening general rules (JIS B1083) for bolts and nuts (hereinafter referred to as “screws”), a torque method, a rotation angle method, a torque gradient method, and the like have been defined as tightening management of the screws. In general, the torque method is often used. In the torque method, a target torque value is set in advance, the tightening torque value output from the torque detection means is compared with the target tightening torque value when tightening is started, and the motor is stopped when they match. It is made to let you. In this torque method, torque is detected by a torque detection mechanism that detects a load current flowing through the motor and converts it into torque, or a torque sensor that detects torque applied to the driver bit.

  A screw tightening device using this torque method can detect screw biting or seizure by monitoring a torque value with respect to an arbitrarily set tightening rotation angle. Specifically, when the male screw is tightened to the female screw, the screw bite occurs when the male screw thread is displaced with respect to the female screw thread, and the screw seizure remains in the bitten state. When the male screw is fastened to the female screw, friction occurs in the screw thread, and the male screw and the female screw are fixed by the frictional heat. When such a screw tightening abnormality occurs, the torque rise relative to the tightening rotation angle will be faster than during normal screw tightening, so it is possible to monitor the torque value against an arbitrarily set tightening rotation angle. Screw biting and seizure can be detected.

  Further, as a screw tightening device using the torque method, between the screw tightening angle position at the torque increase starting point when the first reference torque is reached and the screw tightening angle position in the case of normal screw tightening, When the tightening torque is equal to or greater than the first reference torque, and the angle difference between the position where the tightening torque is equal to or greater than the first reference torque and the screw tightening angular position in the case of normal screw tightening is equal to or greater than a predetermined value. An application of a foreign object biting determination method that determines that a foreign object has been bitten is disclosed (for example, see Patent Document 1).

JP 2001-162548 A

  However, in the screw tightening device using the torque method described in the background art, since the torque value with respect to the arbitrarily set rotation angle is monitored, even if foreign matter exists on the screw tightening seat surface, The position could not be detected at a position outside the arbitrarily set tightening rotation angle range.

  Further, in the foreign matter biting determination method of the screw tightening device disclosed in Patent Document 1, the screw tightening angle position at the torque increase start point when the first reference torque is reached, and the screw tightening angle position in the case of normal screw tightening. Because of the determination based on the abnormality in the tightening torque generated between the screw and the screw, it is detected that there is a foreign object on the screw tightening seat after the screw tightening angle position in the case of normal screw tightening. I couldn't.

  The present invention has been made to solve such a conventional problem, and by extracting from the inclination waveform of the tightening torque that foreign matter is present on the tightening seat surface of the screw, An object of the present invention is to provide a foreign matter presence / absence judging device and a judging method for a tightening seat surface of a screw capable of accurately detecting foreign matter on a tightening seat surface.

  A foreign matter presence / absence determination device for a screw tightening seating surface according to a first aspect of the present invention that achieves the above-described object is a torque detection method for detecting a rotational torque of a screw tightening rotary tool that rotates in response to a motor rotation. A tilt angle waveform of the tightening torque with respect to the tightening rotation angle based on the detected values detected by the torque detection unit, the rotation angle detection unit for detecting the rotation angle of the motor, and the torque detection unit and the rotation angle detection unit. And the approximate curve function together with the approximate curve function, and further calculate the second derivative waveform of the approximate curve function, and if there is an inflection point in the second derivative waveform, Determining means for determining that foreign matter is present on the tightening seat surface, and determining that no foreign matter is present on the tightening seat surface of the screw when there is no inflection point in the waveform of the second-order differential value; It is equipped with. Here, the tightening seat surface of the screw means a contact surface between the screw and the object to be fastened.

  Further, in the foreign matter presence / absence determination device for the screw tightening seat surface according to the first aspect of the second aspect of the present invention, when the determination means determines that there is a foreign object on the screw tightening seat surface. Is provided with an alarm reporting unit for issuing an abnormal alarm.

  Furthermore, the third aspect of the present invention is the foreign matter presence / absence determination device for the screw tightening seat surface according to the first aspect, wherein the determination means is an arithmetic processing unit.

  In addition, the foreign matter presence / absence determination method for the screw tightening seating surface according to the fourth aspect of the present invention that achieves the above-described object is achieved by the arithmetic processing unit and the tightening rotation angle and tightening of the screw when the screw is tightened. Collecting each detection value detected by a detector with a detector; calculating a tilt waveform of the tightening torque with respect to the tightening rotation angle based on the collected detection values of the tightening rotation angle and the tightening torque; and An inflection point exists in the step of calculating the function of the approximate curve together with the approximate curve from the slope waveform, the step of calculating the second derivative value of the function of the approximate curve and creating the waveform, and the waveform of the second derivative value If there is no inflection point in the waveform of the second-order differential value, the foreign matter is present on the screw tightening seat surface. And a step of determining that there is no .

  According to a fifth aspect of the present invention, in the method for determining the presence / absence of a foreign object on a screw fastening seat surface according to the fourth aspect, the approximate curve is a polynomial approximate curve.

  According to such a foreign matter presence / absence determination device and a determination method for a tightening seat surface of a screw, in order to obtain a function of a torque waveform of the tightening torque, the collected detection values of the tightening rotation angle and the tightening torque are collected. Based on the above, an inclination waveform of the tightening torque that is an approximate line with respect to the tightening rotation angle is calculated. By calculating the approximate curve of the inclination waveform, the data fluctuation can be smoothed and the inclination tendency of the tightening torque can be displayed easily. In addition, since the fluctuation of data can be made smoother by using a polynomial approximate curve as the approximate curve, the tendency of the inclination of the tightening torque can be displayed more easily. Furthermore, by calculating the function of the approximate curve, calculating the second derivative of the function of the approximate curve, and creating its waveform, the change of the approximate curve can be expressed more clearly, so the inflection point Can be easily detected.

  In addition, an operator who works with the screw tightening rotary tool is provided with an alarm reporting unit that issues an abnormal alarm when the judging means judges that foreign matter is present on the screw tightening seating surface. Can easily grasp the presence of foreign matter on the tightening seat surface of the screw. Further, by making the determination means an arithmetic processing unit, it can be incorporated into the control system of the screw tightening rotary tool, or can be installed outside as a personal computer.

  According to the foreign matter presence / absence determination device and the determination method for a screw tightening seat surface according to the present invention, the presence of foreign matter on the screw tightening seat surface can be extracted from the inclination waveform of the tightening torque. The foreign matter on the tightening seat surface of the screw can be detected with high accuracy. Further, according to the foreign matter presence / absence determination device and the determination method for a screw tightening seat surface according to the present invention, foreign matter on a screw tightening seat surface can be detected with high accuracy, and therefore cannot be detected by the conventional torque method. It is possible to prevent the defective product from flowing out due to foreign matter existing on the tightening seat surface of the screw.

  BEST MODE FOR CARRYING OUT THE INVENTION A best mode for carrying out a foreign matter presence / absence judgment device and its judgment method for a screw tightening seat according to the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the device for determining the presence or absence of a foreign matter on a screw tightening seat according to the present invention is applied to a nut runner 2 which is an automatic screw tightening machine, as shown in FIG. A motor 21 that outputs a rotational torque proportional to the value, a speed reducer 22 that is coupled to a rotational shaft (not shown) of the motor 21 and amplifies the output torque of the motor 21, and a tip of the rotational shaft 23 of the speed reducer 22 And a tightening portion 24 that is coaxially connected to the head of the bolt 43. The nut runner 2 includes a torque detector 25 such as a magnetostrictive torque sensor that detects rotational torque applied to the rotary shaft 23 of the speed reducer 22, and a rotational angle of a pulse generator that detects the rotational angle of the rotary shaft of the motor 21. And a detection unit 26.

  Further, the nut runner 2 is electrically connected to the controller 3 in which the motor 21, the torque detection unit 25, and the rotation angle detection unit 26 control the motor 21. The controller 3 feedback-controls the motor 21 based on the detection values detected by the torque detection unit 25 and the rotation angle detection unit 26, thereby monitoring the torque value with respect to the arbitrarily set rotation angle and screwing. Biting and seizure can be prevented. The nut runner 2 can fasten a bolt 43 with a predetermined tightening torque to a nut 42 attached to a fastened body 41 such as an iron plate by a tightening portion 24.

  Further, the foreign matter presence / absence determination device 1 performs an arithmetic processing on the inclination waveform of the tightening torque with respect to the tightening rotation angle based on the detected values detected by the torque detection unit 25 and the rotation angle detection unit 26, and calculates the inclination waveform from the inclination waveform along with the approximate curve. The approximate curve function is processed, and the second derivative waveform of the approximate curve function is calculated. If there is an inflection point in the second derivative waveform, Arithmetic processing device 5 which is a determination means for determining that there is no foreign matter and determining that no foreign matter is present on the tightening seat surface of the screw when there is no inflection point in the waveform of the second-order differential value. Are electrically connected to the controller 3.

  In order to obtain a function of the torque waveform of the tightening torque, the arithmetic processing unit 5 determines the tightening torque that is an approximate line with respect to the tightening rotation angle based on the collected detection values of the tightening rotation angle and the tightening torque. An inclination waveform is calculated. By calculating the approximate curve of the inclination waveform, the data fluctuation can be smoothed and the inclination tendency of the tightening torque can be displayed easily. In addition, since the fluctuation of data can be made smoother by using a polynomial approximate curve as the approximate curve, the tendency of the inclination of the tightening torque can be displayed more easily. Furthermore, by calculating the function of the approximate curve, calculating the second derivative of the function of the approximate curve, and creating its waveform, the change of the approximate curve can be expressed more clearly, so the inflection point Can be easily detected.

  As such an arithmetic processing unit 5, a notebook personal computer is preferable so that it can be easily carried on a production line of an automobile manufacturing plant in which the nutrunner 2 is used. It can also be made. In addition, when the arithmetic processing unit 5 determines that there is a foreign object on the tightening seat surface of the screw, an alarm notification unit (not shown) that issues an abnormality alarm may be provided. By providing this alarm notification unit, an operator working with the nutrunner 2 can easily grasp the presence of foreign matter on the tightening seat surface of the screw. In the case of a notebook personal computer, the alarm issuing unit may be notified by voice or displayed on the screen.

  Next, with reference to FIGS. 2, 3A, 3B, 4A, and 4B, a method for determining the presence / absence of foreign matter on the screw tightening seat surface by the arithmetic processing unit 5 will be described. FIG. 2 is a flowchart showing an operation procedure for determining the presence or absence of foreign matter on the screw tightening seat surface. In this flowchart, steps S103 to S111 are executed based on a program stored in a control unit (not shown) of the arithmetic processing unit 5. FIG. 3 is a graph showing a torque waveform, an inclination waveform, and an approximate curve of the inclination waveform. (A) is a diagram when the screw tightening seat surface is normal, and (B) is an abnormal screw tightening seat surface. FIG. 4A and 4B are graphs showing a torque waveform and a second-order differential value waveform, where FIG. 4A is a diagram when the screw tightening seat surface is normal, and FIG. 4B is a diagram when the screw tightening seat surface is abnormal. It is. In FIGS. 3A, 3B, 4A, and 4B, the left vertical axis is the tightening torque (Nm), the horizontal axis is the pulse (angle), and the right vertical axis is the coefficient of the approximate curve function. Further, the left end of the horizontal axis indicates the screw tightening start position, and the right end indicates the screw tightening completion position.

  For example, when the notebook personal computer 5 is electrically connected to the controller 3 for the nut runner 2 and the nut runner 2 is driven, screw tightening is started (step S101), and the controller 3 starts screw tightening. Along with this, the tightening torque value output from the torque detector 25 is compared with the target tightening torque value, and when this matches, the motor 21 is stopped, so that the screw tightening by the nut runner 2 is completed (step S102).

  When the screw tightening by the nutrunner 2 is completed, the controller 3 transmits an electrical signal of each detected value detected by the torque detector 25 and the rotation angle detector 26 to the notebook personal computer 5. Can collect tightening torque data and tightening rotation angle data (step S103).

In order to obtain a function of the torque waveform of the tightening torque, a tilt waveform of the tightening torque that is an approximate line with respect to the tightening rotation angle is calculated based on the collected detected values of the tightening rotation angle and the tightening torque (step) S104). At this time, the torque waveform W1 and the tilt waveform W2 are waveform diagrams as shown in FIGS. Then, an approximate curve is calculated from the slope waveform, and a function of the approximate curve is calculated (steps S105 and S106). Note that since the slope waveform W2 has a large variation in data, the approximate curve is a sixth-order approximate curve.
F = ax ⁶ + bx ⁵ + cx ⁴ + dx ³ + ex ² + fx + g
It becomes. Here, x is a rotation angle. A second-order differential value of the function of this approximate curve is calculated and its waveform is created (step S107). That is, if the function of the approximate curve is first-order differentiated,
F ′ = 6ax ⁵ + 5bx ⁴ + 4cx ³ + 3dx ² + 2ex + f
When this function is second-order differentiated,
F ″ = 30ax ⁴ + 20bx ³ + 12cx ² + 6dx + 2e
It becomes. At this time, the torque waveform W1 and the second-order differential waveform W4 are as shown in FIGS. 4 (A) and 4 (B).

  Then, the control unit of the notebook personal computer 5 confirms the presence or absence of an inflection point from the waveform of the second order differential value (step S108). The presence or absence of an inflection point can be confirmed by substituting a rotation angle other than 0 from the start of tightening of the screw to the end of tightening into x of the function of the second order differential value, and F ″ = 0 becomes the inflection point. Therefore, the foreign matter exists at the position of the rotation angle where F ″ = 0.

  The control unit of the notebook personal computer 5 confirms the presence or absence of an inflection point from the waveform of the second order differential value, and the inflection point IP is added to the waveform of the second order differential value as shown in FIG. If it does not exist, it is determined that no foreign matter is present on the screw tightening seat (step S109), and information indicating that the screw is tightened is notified by a liquid crystal panel or voice (step S110). On the other hand, as shown in FIG. 4B, when the inflection point IP exists in the waveform of the second-order differential value, it is determined that there is a foreign object on the tightening seat surface of the screw (step S109). ) Information indicating that the screw tightening is abnormal is notified by a liquid crystal panel or voice (step S111). Note that the inflection point occurs when a foreign object is present on the tightening seat surface of the screw because the torque changes due to the foreign object being deformed or slipped by tightening.

  As described above, according to the foreign matter presence / absence determination method for the screw tightening seat surface according to the present invention, the torque waveform W1 is calculated and processed as in the above-described program, so that Since it can be easily determined from the noise that a foreign object is present on the screw tightening seat surface, the foreign object on the screw tightening seat surface can be accurately detected.

  The configuration of the nut runner 2 is not limited to the above-described embodiment, and the foreign matter presence / absence determination device and the determination method for the screw tightening seat surface of the present invention can be applied to any existing nut runner.

  Although the present invention has been described with the specific embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and is known so far as long as the effects of the present invention are achieved. It goes without saying that any configuration can be adopted.

  Since the foreign matter presence / absence determination method described above determines that foreign matter is present from the large and small noise that appears in the waveform when tightening the screw, not only the foreign matter present on the screw tightening seat surface, It is also possible to discriminate foreign matter existing on the contact surface between the male screw thread and the female screw thread. That is, it is possible to determine the presence of foreign matter from the large and small noise appearing in the waveform from the position near the screw tightening seat surface to the screw tightening completion position.

It is a whole block diagram which shows the example of preferable embodiment in the foreign material presence determination apparatus of the fastening seating surface of the screw of this invention. It is a flowchart figure which shows the example of preferable embodiment in the foreign material presence / absence determination method of the fastening seating surface of the screw of this invention. It is a graph which shows the approximate curve of the torque waveform, inclination waveform, and inclination waveform which are used with the foreign matter presence / absence determination method of the tightening seat surface of the screw of the present invention. It is a graph which shows the torque waveform and the waveform of a 2nd-order differential value which are used with the foreign substance presence / absence determination method of the tightening seat surface of the screw of the present invention.

Explanation of symbols

1 …… Determining device for foreign matter on screw tightening seat surface 2 …… Nutrunner (rotary tool for tightening screws)
21 …… Motor 25 …… Torque detection unit 26 …… Rotation angle detection unit 5 …… Operation processing device (determination means)

Claims (5)

A torque detector that detects the rotational torque of the screw tightening rotary tool that rotates in response to the rotation of the motor;
A rotation angle detector for detecting a rotation angle of the motor;
Based on the detection values detected by the torque detection unit and the rotation angle detection unit, an inclination waveform of the tightening torque with respect to the tightening rotation angle is calculated, and an approximate curve and a function of the approximate curve are calculated from the inclination waveform. And processing the second derivative waveform of the function of the approximate curve, and if there is an inflection point in the second derivative waveform, there is a foreign object on the tightening seat surface of the screw. Determining means for determining that no foreign matter is present on the tightening seat surface of the screw when there is no inflection point in the waveform of the second-order differential value. A foreign matter presence / absence judgment device on the tightening seat surface of the screw.   2. The screw according to claim 1, further comprising an alarm notification unit that issues an abnormality alarm when the determination means determines that a foreign object is present on the tightening seat surface of the screw. Foreign matter presence / absence judging device for tightening seat surface.   3. The foreign matter presence / absence judging device for a screw tightening seat according to claim 1, wherein the judging means is an arithmetic processing unit. Arithmetic processing unit
Collecting each detected value obtained by detecting the tightening rotation angle and tightening torque of the screw when tightening the screw with a detector;
Calculating an inclination waveform of the tightening torque with respect to the tightening rotation angle based on the collected detection values of the tightening rotation angle and the tightening torque; and
Calculating a function of the approximate curve together with the approximate curve from the slope waveform;
Calculating a second derivative of the function of the approximate curve and creating its waveform;
Determining that foreign matter is present on the tightening seat surface of the screw when an inflection point exists in the waveform of the second-order differential value;
A step of determining that no foreign matter is present on the tightening seat surface of the screw when there is no inflection point in the waveform of the second-order differential value. Foreign matter determination method.   5. The method for determining the presence or absence of foreign matter on a screw tightening seat according to claim 4, wherein the approximate curve is a polynomial approximate curve.

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