JP5703947B2 - Bolt tightening method and apparatus - Google Patents

Description

  The present invention belongs to a technical field related to a bolt tightening method and apparatus for bolt tightening management.

  Generally, when assembling a machine part, it is required to secure long-term durability reliability of the part by tightening a bolt. Therefore, bolt tightening is managed. As this management method, a bolt tightening torque is controlled so that the bolt tightening torque becomes a preset torque (referred to as a torque method in this specification), or the bolt tightening torque is set in advance. A method of performing bolt tightening management (referred to as an angle method in this specification) such that the bolt tightening angle from the time when the set snag torque is reached becomes a preset set angle, bolt tightening During tightening, after the bolt tightening torque reaches a preset snag torque, a torque gradient that is a tightening torque increment relative to the tightening angle increment is calculated, and the bolt tightening angle and tightening torque are calculated. On the two-dimensional orthogonal graph with two axes, the intersection of the slope of the torque gradient and the line where the torque value is 0 is defined as the theoretical seating point, and the bolt tightening angle from the theoretical seating point is set in advance. At the set angle. (In this specification, the torque that tension method) technique for bolt fastening management as such are known. Various techniques based on these techniques have also been proposed (see, for example, Patent Documents 1 to 3).

JP 2006-272512 A JP 2009-083025 A JP 2009-083026 A

  However, in the bolt tightening management method such as the torque method described above, the tightening angle and tightening torque at the end of bolt tightening depend on the friction coefficient of the screw surface and seating surface when tightening the bolt. Therefore, there is a case where the tightening angle or the tightening torque exceeds the angle management range or the torque management range managed as a normal tightening state. Moreover, although the amount of dispersion | variation is improved by the methods like the said patent documents 1-3, it is a complicated method and there exists room for improvement in order to enable it to manage by a simple method.

  The present invention has been made in view of such points, and the object of the present invention is to be able to suppress variations in both the tightening angle and the tightening torque at the end of bolt tightening, while being simple. Is to make it.

  In order to achieve the above object, according to the present invention, during the bolt tightening, the bolt tightening angle from the time when the bolt tightening torque reaches a preset snag torque, and the tightening angle. For the bolt tightening method in which the bolt tightening torque is terminated when the bolt tightening torque satisfies the predetermined relationship, the predetermined relationship is the tightening angle from the snag torque. On the two-dimensional orthogonal graph with the tightening torque as two axes, the tightening torque is expressed as a specific line that decreases as the tightening angle from the snag torque increases, and the specific line is the two-dimensional orthogonal In the graph, the tightening torque is larger as the tightening torque is larger than the tightening torque reference line where the tightening torque is constant as the predetermined torque and the tightening angle from the snag torque is larger. A tightening angle smaller than the tightening torque reference line, and a tightening torque smaller than the tightening reference line. The predetermined torque is a line passing through the second region where the tightening angle is large, and the predetermined torque is a value when the bolt tightening management is performed so that the bolt tightening torque becomes a preset torque. The tightening reference line is a tightening torque increment with respect to a tightening angle increment after the tightening torque of the bolt reaches a preset snag torque during tightening of the bolt. Calculate the torque gradient, and on the two-dimensional orthogonal graph with the bolt tightening angle and tightening torque as two axes, the intersection of the slope of the torque gradient and the line where the tightening torque is zero is the theoretical seating point. The bolt tightening angle from the theoretical seating point is set in advance. At the end of bolt tightening, plotted on a two-dimensional orthogonal graph with the tightening angle from the snag torque and the tightening torque as two axes The line was determined in advance as a regression line of a plurality of data points composed of the tightening angle from the snag torque and the tightening torque.

  That is, in the torque method, the tightening torque at the end of bolt tightening is positioned on the tightening torque reference line on the two-dimensional orthogonal graph and becomes substantially constant. Depending on the size of the friction coefficient, the tightening angle from the snag torque at the end of bolt tightening (hereinafter, the tightening angle from the snag torque is simply referred to as the tightening angle) varies. That is, the tightening angle at the end of bolt tightening is the friction coefficient maximum line on the tightening torque reference line on the two-dimensional orthogonal graph (the tightening angle and the tightening torque when the friction coefficient is the maximum). This is a line showing the relationship, and the larger the tightening angle, the more the tightening torque becomes a straight line) and the friction coefficient minimum line (the relationship between the tightening angle and the tightening torque when the above friction coefficient is the minimum) And a straight line (the inclination is different from the maximum friction coefficient line) in which the tightening torque increases as the tightening angle increases. This variation amount is relatively large and is usually larger than the angle management range managed as a normal tightening state. On the other hand, in the torque tension method, the tightening angle at the end of bolt tightening is located on or near the tightening reference line on the two-dimensional orthogonal graph, and the maximum friction coefficient line and the friction coefficient on or near the tightening reference line. It varies between the minimum line. The tightening reference line is a straight line in which the tightening torque increases as the tightening angle increases, and the acute angle between the tightening reference line and the straight line with a constant tightening angle is relatively small. Therefore, although the variation amount of the tightening angle is small and normally within the angle management range, the variation amount of the tightening torque is larger than the torque management range managed as a normal tightening state.

  On the other hand, in the present invention, the tightening angle and the tightening torque at the end of bolt tightening vary between the friction coefficient maximum line and the friction coefficient minimum line on a specific line on the two-dimensional orthogonal graph. As the tightening angle increases, the tightening torque decreases with the specific line. Therefore, along the axis of the tightening angle between the intersection of the specific line and the friction coefficient maximum line and the intersection of the specific line and the friction coefficient minimum line. The distance is shorter than the intersection between the tightening torque reference line and the friction coefficient maximum line and the distance between the intersection between the tightening torque reference line and the friction coefficient minimum line. The distance along the axis of tightening torque between the intersection of the specific line and the maximum friction coefficient line and the intersection of the specific line and the minimum friction coefficient line is the intersection of the tightening reference line and the maximum friction coefficient line and The distance between the intersections of the tightening reference line and the friction coefficient minimum line is shorter than the distance along the tightening torque axis.

  Therefore, in the present invention, even if the friction coefficient varies, variations in both the tightening angle and the tightening torque at the end of the bolt tightening can be reduced, and the tightening angle and the tightening torque at the end of the bolt tightening can be reduced. Can fall within the angle management range and the torque management range, respectively. Further, during bolt tightening, the motor is stopped when the bolt tightening angle and the bolt tightening torque at the tightening angle satisfy a predetermined relationship (when positioned on a specific line). With this simple method, it is possible to suppress variations in both the tightening angle and the tightening torque at the end of bolt tightening.

  According to an embodiment of the present invention, the specific line passes through an intersection of the tightening torque reference line and the tightening reference line on the two-dimensional orthogonal graph.

  This makes it possible to bring the tightening angle and tightening torque at the end of bolt tightening closer to the ideal position that is the intersection of the tightening torque reference line and the tightening angle reference line, and at the end of bolt tightening. The tightening angle and the tightening torque at are easily within the angle management range and the torque management range, respectively.

According to another embodiment of the present invention, the specific line is a straight line, and the first region between the tightening torque reference line and the tightening reference line is defined on the two-dimensional orthogonal graph. When the sandwiching angle is α1, the acute angle α between the specific line and the tightening reference line is
α1 / 2−α1 / 4 ≦ α ≦ α1 / 2 + α1 / 4
Meet.

  As a result, the tightening angle and the tightening torque at the end of the bolt tightening can be more easily entered within the angle management range and the torque management range, respectively.

  Another aspect of the present invention includes a motor that rotates a tightening member for tightening a bolt, a tightening angle detection unit that detects a tightening angle of the bolt that is tightened by the rotation of the tightening member, and the bolt A tightening torque detecting means for detecting the tightening torque of the motor, and input of detection information by the tightening angle detecting means and the tightening torque detecting means to control the driving and stopping of the motor, During the tightening of the bolt, the bolt tightening angle from when the bolt tightening torque reaches a preset snag torque and the bolt tightening torque at the tightening angle have a predetermined relationship. A bolt tightening device including a controller for stopping the motor when it is satisfied, wherein the predetermined relationship includes the tightening angle from the snag torque and the tightening torque. On a two-dimensional orthogonal graph with two axes as a center, the tightening angle from the snag torque is larger, and the tightening torque is expressed as a smaller specific line. Tightening consisting of a straight line in which the tightening torque is larger than the tightening torque reference line where the tightening torque is constant as a predetermined torque, and the tightening torque increases as the tightening angle from the snag torque increases. A first region in which the tightening angle is smaller than the reference line; and the tightening torque is smaller than the tightening torque reference line and the tightening angle is larger than the tightening reference line. The predetermined torque is a set torque when the bolt tightening management is performed so that the bolt tightening torque becomes a preset torque set in advance. Tightening reference line is During bolt tightening, after the bolt tightening torque reaches a preset snag torque, a torque gradient that is the tightening torque increment relative to the tightening angle increment is calculated, and the bolt tightening angle and tightening torque are calculated. On the two-dimensional orthogonal graph with the attached torque as two axes, the intersection of the inclination line of the torque gradient and the line where the tightening torque is 0 is the theoretical seating point, and the bolt tightening angle from the theoretical seating point Is plotted on a two-dimensional orthogonal graph with the tightening angle from the snag torque and the tightening torque as two axes when the tightening management of the bolt is performed so as to be a preset set angle. It is assumed that this is a line obtained in advance as a regression line of a plurality of sets of data points composed of the tightening angle from the snag torque and the tightening torque at the end of bolt tightening.

  According to the present invention, similar to the above-described bolt tightening method, it is possible to suppress variations in both the tightening angle and the tightening torque at the end of bolt tightening while being simple.

  As described above, according to the present invention, during the bolt tightening, the bolt tightening angle (the tightening angle from the snag torque) and the bolt tightening torque at the tightening angle are determined as follows. Since the motor is stopped when the relationship is satisfied (when it is located on a specific line), it is possible to suppress variations in both the tightening angle and the tightening torque at the end of bolt tightening with a simple method. The long-term durability reliability of the component fastened by the bolt can be ensured.

It is a side view which shows the bolt fastening apparatus which concerns on embodiment of this invention. It is a two-dimensional orthogonal graph with the bolt tightening angle from the snag torque as the horizontal axis and the bolt tightening torque as the vertical axis. FIG. 3 is a graph corresponding to FIG. 2 illustrating a relationship between a management range and a portion between an intersection with a friction coefficient maximum line and a friction coefficient minimum line on a specific line. It is a graph which shows the relationship between the bolt tightening angle and bolt tightening torque for demonstrating the torque tension method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a bolt fastening device 1 according to an embodiment of the present invention. The bolt fastening device 1 includes a socket 2 as a fastening member for fastening a bolt, and a motor (not shown) that rotates the socket 2 via a reduction gear (not shown). . The socket 2 has a concave portion (not shown) that fits on the outer peripheral surface of the bolt head or on the outer peripheral surface of a nut that is screwed into the threaded portion of the bolt at the tip end surface thereof. Tighten the bolt by rotating with.

  The parts to be fastened by the bolts may be any kind, but in particular, mechanical parts that need to ensure long-term durability and reliability (for example, parts for automobile traveling systems (axle parts, etc.)). In this case, the tightening method by the bolt tightening device 1 is effective.

  The motor and the reduction gear are accommodated in the motor part 3a and the gear part 3b of the main body case 3, respectively, and the gear part 3b is located closer to the socket 2 than the motor part 3a.

  On the opposite side of the main body case 3 from the gear portion 3b, a resolver 5 is disposed as a tightening angle detecting means for detecting a tightening angle of a bolt tightened by the rotation of the socket 2. In addition, a torque transducer 6 serving as a tightening torque detecting means for detecting a tightening torque of a bolt tightened by the rotation of the socket 2 is disposed between the reduction gear (the gear portion 3b of the main body case 3) and the socket 2. Has been.

  The bolt tightening device 1 further includes a controller 8 for inputting detection information from the resolver 5 and the torque transducer 6. The controller 8 is based on a well-known microcomputer, and includes a central processing unit (CPU) that executes a program, a memory configured by, for example, RAM and ROM, and stores programs and data, and various types. And an input / output (I / O) bus for inputting and outputting signals.

  The controller 8 includes a motor control unit 8a that controls driving and stopping of the motor, and a storage unit 8b that stores and stores a preset specific line L1, a preset value of the snag torque Ts, and the like. ing. Then, the motor control unit 8a of the controller 8 drives the motor by operating an operation switch (not shown) of the operator, and during the bolt tightening by driving the motor, the tightening torque of the bolt is the snag torque. When the bolt tightening angle θ from the point of time Ts and the bolt tightening torque T at the tightening angle θ satisfy a predetermined relationship, the motor is stopped.

  As shown in FIG. 2, the predetermined relationship is that the tightening angle θ from the snag torque Ts and the tightening torque T are two axes (in FIG. 2, the tightening angle θ is a horizontal axis, On a two-dimensional orthogonal graph (with the torque T as the vertical axis), the tightening angle T is represented by a specific line L1 that decreases as the tightening angle θ increases.

  The specific line L1 indicates that the tightening torque T is larger than the tightening torque reference line L2 on the two-dimensional orthogonal graph where the tightening torque T is constant as the predetermined torque T1, and the snag torque Ts. From the first region A in which the tightening angle θ is smaller than the tightening reference line L3 that is a straight line in which the tightening torque T increases as the tightening angle θ from the second position increases, and from the tightening torque reference line L2 Is a line passing through the second region B in which the tightening torque T is small and the tightening angle θ is larger than the tightening reference line L3.

In the present embodiment, the specific line L1 is a straight line passing through the intersection point P1 between the tightening torque reference line L2 and the tightening angle reference line L3 on the two-dimensional orthogonal graph, and the tightening torque reference line L2 When the angle between the first region A and the tightening reference line L3 is α1, the acute angle α between the specific line L1 and the tightening reference line L3 is
α1 / 2−α1 / 4 ≦ α ≦ α1 / 2 + α1 / 4
Meet. In FIG. 2, α = α1 / 2, and the specific line L1 divides the first region A and the second region B into two equal parts.

  The predetermined torque T1 is a set torque when the bolt tightening management is performed so that the bolt tightening torque becomes a preset torque. That is, the predetermined torque T1 is a target torque when the bolt tightening management is performed by the torque method. In this torque method, the tightening torque at the end of bolt tightening is positioned on the tightening torque reference line L2 and becomes substantially constant. However, depending on the friction coefficient of the thread surface and the seat surface during bolt tightening, The tightening angle at the end of bolt tightening (that is, the bolt tightening axial force) is between the maximum friction coefficient line U1 and the minimum friction coefficient line U2 on the tightening torque reference line L2 (the tightening torque reference line L2 and It varies at the intersection point P4 with the friction coefficient maximum line U1 and between the tightening torque reference line L2, the friction coefficient minimum line U2 and the intersection point P5). The amount of variation in the tightening angle is usually larger than the angle management range (see FIG. 3) that is managed as a normal tightening state. Therefore, the tightening angle at the end of bolt tightening is the angle management range. If the angle management range is exceeded, a defective product is produced.

  Here, the friction coefficient maximum line U1 is a line indicating the relationship between the tightening angle from the snag torque and the tightening torque when the friction coefficient is the maximum when the bolt is tightened. The larger the tightening angle, the straighter the tightening torque. The friction coefficient minimum line U2 is a line indicating the relationship between the tightening angle from the snag torque and the tightening torque when the friction coefficient is the minimum when the bolt is tightened. As the attachment angle increases, the tightening torque becomes a straight line. When the tightening angle from the snag torque is taken as the horizontal axis, the inclination of the friction coefficient minimum line U2 becomes smaller than the friction coefficient maximum line U1.

  The tightening reference line L3 is displayed on a two-dimensional orthogonal graph with the tightening angle θ from the snag torque Ts and the tightening torque T as two axes when bolt tightening management is performed by the torque tension method. Plotted lines obtained in advance as regression lines of a plurality of sets of data points including the tightening angle θ from the snag torque Ts and the tightening torque T at the end of bolt tightening. The torque tension method is a tightening management method as described below.

  That is, as shown in FIG. 4, during the bolt tightening, after the bolt tightening torque reaches the preset snag torque Ts, the torque gradient that is the tightening torque increment with respect to the tightening angle increment is set. Calculate the bolt tightening angle (in FIG. 4, it is the tightening angle from the start of bolt tightening by the bolt tightening device 1, but from the snag torque as in the horizontal axis of the two-dimensional orthogonal graph of FIG. On the two-dimensional orthogonal graph with two bolts as the bolt tightening angle and the bolt tightening torque (the horizontal axis in FIG. 4). ) Is a theoretical seating point P, and bolt tightening management is performed so that the bolt tightening angle from the theoretical seating point P becomes a preset set angle θ1. When tightening management is performed by such a torque tension method, the tightening angle and the tightening torque from the snag torque at the end of bolt tightening are the tightening angle θ from the snag torque Ts and the tightening torque T. Is approximately on a straight line on a two-dimensional orthogonal graph (FIG. 2) with two axes. This straight line is obtained as a regression line of the plurality of sets of data points.

  The regression line (that is, the tightening reference line L3) is a straight line having a larger tightening torque as the tightening angle from the snag torque is larger. The tightening reference line L3 and a straight line having a constant tightening angle from the snag torque are constant. Is relatively small (the inclination of the tightening reference line L3 is relatively large in FIG. 2). Depending on the magnitude of the friction coefficient, the tightening angle and the tightening torque from the snag torque at the end of bolt tightening are the friction coefficient maximum line U1 and the friction coefficient minimum line U2 on or near the tightening reference line L3. Between the tightening reference line L3 and the friction coefficient maximum line U1 and between the tightening reference line L3 and the friction coefficient minimum line U2 and the intersection P7. Since the inclination of the tightening reference line L3 is relatively large, the amount of variation in the tightening angle from the snag torque is small and is normally within the angle control range, but the amount of variation in the tightening torque is normal tightening This is larger than the torque management range managed as a condition (see Fig. 3). For this reason, the tightening torque at the end of bolt tightening may exceed the torque management range, thus exceeding the torque management range Becomes defective.

  In the present embodiment, during bolt tightening, when the bolt tightening angle θ from the snag torque Ts and the bolt tightening torque T at the tightening angle θ satisfy a predetermined relationship, that is, When the tightening angle θ and the tightening torque T (coordinates) are positioned on the specific line L1 on a two-dimensional orthogonal graph with the tightening angle θ and the tightening torque T from the snag torque Ts as two axes. Then stop the motor. Thus, the tightening angle θ from the snag torque Ts and the tightening torque T at the end of bolt tightening are between the friction coefficient maximum line U1 and the friction coefficient minimum line U2 on the specific line L1 (specific line). And the intersection point P2 between L1 and the friction coefficient maximum line U1 and the intersection point P3 between the specific line L1 and the friction coefficient minimum line U2. Here, the distance along the axis (horizontal axis) of the tightening angle between the intersection point P2 between the specific line L1 and the friction coefficient maximum line U1 and the intersection point P3 between the specific line L1 and the minimum friction coefficient line U2 is the tightening distance. It is shorter than the distance between the intersection point P4 between the torque reference line L2 and the maximum friction coefficient line U1 and the intersection point P5 between the tightening torque reference line L2 and the minimum friction coefficient line U2, and the tightening reference line L3 and the maximum friction coefficient line. The distance along the horizontal axis between the intersection point P6 with U1 and the intersection point P7 between the tightening torque reference line L3 and the friction coefficient minimum line U2 is substantially the same. In addition, the distance along the axis (vertical axis) of the tightening torque between the intersection point P2 between the specific line L1 and the maximum friction coefficient line U1 and the intersection point P3 between the specific line L1 and the minimum friction coefficient line U2 is a tightening standard. The distance between the intersection point P6 between the line L3 and the maximum friction coefficient line U1 and the intersection point P7 between the tightening torque reference line L3 and the minimum friction coefficient line U2 is shorter than the distance along the vertical axis. As a result, the amount of variation in tightening angle at the end of bolt tightening can be made smaller than the amount of variation in tightening angle when bolt tightening is managed by the torque method, and at the end of bolt tightening. The variation amount of the tightening torque can be made smaller than the variation amount of the tightening torque when the bolt tightening management is performed by the torque tension method.

  Therefore, even if the friction coefficient varies, the amount of variation in both the tightening angle and the tightening torque at the end of bolt tightening is reduced, and the tightening angle and the tightening torque at the end of bolt tightening are each within the angle management range. And within the torque management range.

Here, as shown in FIG. 3, the tightening angle that passes through the minimum value and the maximum value of the angle management range on a two-dimensional orthogonal graph with the tightening angle from the snag torque and the tightening torque as two axes. A square management range S surrounded by two straight lines having a constant tightening torque and two straight lines passing through the minimum value and the maximum value of the torque management range is set. If the angle α is set so that the portion between the intersection point P2 with the friction coefficient maximum line U1 and the intersection point P3 with the friction coefficient minimum line U2 in the specific line L1 is within the management range S, the friction coefficient is Even if there is a variation, the tightening angle and the tightening torque at the end of bolt tightening are within the angle management range and the torque management range, respectively. The angle α is
α1 / 2−α1 / 4 ≦ α ≦ α1 / 2 + α1 / 4
If it is set so as to satisfy, the portion between the intersection point P2 of the specific line L1 with the friction coefficient maximum line U1 and the intersection point P3 with the friction coefficient minimum line U2 is sufficiently within the generally set management range S. .

  Therefore, in this embodiment, when the bolt is tightened, the bolt tightening angle from the snag torque and the bolt tightening torque at the tightening angle satisfy a predetermined relationship (specific line L1). With this simple method of stopping the motor when it is positioned above, variations in both the tightening angle and the tightening torque at the end of bolt tightening can be suppressed.

  The present invention is not limited to the embodiment described above, and can be substituted without departing from the spirit of the claims.

  For example, in the above embodiment, the specific line L1 is a straight line passing through the intersection point P1 between the tightening torque reference line L2 and the tightening angle reference line L3, but the tightening torque reference line L2 and the tightening angle reference line L3 are not necessarily limited. There is no need to pass through the intersection P1.

  Further, the angle α is not necessarily required to satisfy α1 / 2−α1 / 4 ≦ α ≦ α1 / 2 + α1 / 4. Depending on the relationship between the angle management range of the management range S and the torque management range, It may be outside the angular range.

  Furthermore, in the above-described embodiment, the specific line L1 is a straight line. However, as the tightening angle θ from the snag torque Ts increases, the tightening torque T decreases and passes through the first region A and the second region B. It may be set as a curve.

  The above-described embodiments are merely examples, and the scope of the present invention should not be interpreted in a limited manner. The scope of the present invention is defined by the scope of the claims, and all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention is useful for a bolt tightening method and apparatus for performing bolt tightening management, and particularly for tightening a bolt for fastening a machine part that needs to ensure long-term durability and reliability. This is useful when applied to the appendix.

1 Bolt tightening device 2 Socket (Tightening member)
5 Resolver (Tightening angle detection means)
6 Torque transducer (Tightening torque detection means)
8 Controller L1 Specified line L2 Tightening torque reference line L3 Tightening reference line

Claims (4)

During the bolt tightening, the bolt tightening angle from the time when the bolt tightening torque reaches the preset snag torque and the bolt tightening torque at the tightening angle have a predetermined relationship. A bolt tightening method that terminates the bolt tightening when
In the two-dimensional orthogonal graph with the tightening angle from the snag torque and the tightening torque as two axes, the predetermined relationship is such that the tightening torque decreases as the tightening angle from the snag torque increases. Represented by a line,
In the two-dimensional orthogonal graph, the specific line indicates that the tightening torque is larger than a tightening torque reference line in which the tightening torque is constant as a predetermined torque, and the tightening angle from the snag torque is A first region in which the tightening angle is smaller than a tightening reference line formed of a straight line that increases as the tightening torque increases; the tightening torque is smaller than the tightening torque reference line; and A line passing through the second region where the tightening angle is larger than the tightening reference line,
The predetermined torque is the set torque in the case of performing bolt tightening management so that the bolt tightening torque becomes a preset torque set in advance.
The tightening reference line calculates a torque gradient that is a tightening torque increment with respect to a tightening angle increment after the bolt tightening torque reaches a preset snag torque during tightening of the bolt. On the two-dimensional orthogonal graph with the bolt tightening angle and tightening torque as two axes, the intersection of the slope of the torque gradient and the line where the tightening torque is zero is the theoretical seating point, and the theoretical seating When the bolt tightening management is performed so that the bolt tightening angle from the point becomes a preset set angle, the tightening angle from the snag torque and the tightening torque are two axes. Bolt characterized by being a line obtained in advance as a regression line of a plurality of data points comprising the tightening angle from the snag torque and the tightening torque at the end of bolt tightening plotted on a two-dimensional orthogonal graph Tightening Method. In the bolt fastening method according to claim 1,
The bolt tightening method, wherein the specific line passes through an intersection of the tightening torque reference line and the tightening reference line on the two-dimensional orthogonal graph. In the bolt fastening method according to claim 1 or 2,
The specific line is a straight line,
On the two-dimensional orthogonal graph, when the angle sandwiching the first region between the tightening torque reference line and the tightening reference line is α1, the distance between the specific line and the tightening reference line. The acute angle α of
α1 / 2−α1 / 4 ≦ α ≦ α1 / 2 + α1 / 4
A bolt tightening method characterized by satisfying A motor for rotating a tightening member for tightening the bolt, a tightening angle detecting means for detecting a tightening angle of the bolt tightened by the rotation of the tightening member, and a tightening for detecting the tightening torque of the bolt Torque detection means, and detection information by the tightening angle detection means and the tightening torque detection means are inputted and the driving and stopping of the motor are controlled, and the bolt is tightened during the tightening of the bolt by the driving of the motor. When the bolt tightening angle from when the tightening torque reaches a preset snag torque and the bolt tightening torque at the tightening angle satisfy a predetermined relationship, the motor is A bolt tightening device comprising a controller for stopping,
In the two-dimensional orthogonal graph with the tightening angle from the snag torque and the tightening torque as two axes, the predetermined relationship is such that the tightening torque decreases as the tightening angle from the snag torque increases. Represented by a line,
In the two-dimensional orthogonal graph, the specific line indicates that the tightening torque is larger than a tightening torque reference line in which the tightening torque is constant as a predetermined torque, and the tightening angle from the snag torque is A first region in which the tightening angle is smaller than a tightening reference line formed of a straight line that increases as the tightening torque increases; the tightening torque is smaller than the tightening torque reference line; and A line passing through the second region where the tightening angle is larger than the tightening reference line,
The predetermined torque is the set torque in the case of performing bolt tightening management so that the bolt tightening torque becomes a preset torque set in advance.
The tightening reference line calculates a torque gradient that is a tightening torque increment with respect to a tightening angle increment after the bolt tightening torque reaches a preset snag torque during tightening of the bolt. On the two-dimensional orthogonal graph with the bolt tightening angle and tightening torque as two axes, the intersection of the slope of the torque gradient and the line where the tightening torque is zero is the theoretical seating point, and the theoretical seating When the bolt tightening management is performed so that the bolt tightening angle from the point becomes a preset set angle, the tightening angle from the snag torque and the tightening torque are two axes. Bolt characterized by being a line obtained in advance as a regression line of a plurality of data points comprising the tightening angle from the snag torque and the tightening torque at the end of bolt tightening plotted on a two-dimensional orthogonal graph Tightening Apparatus.

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