JP7530806B2 - Fastening inspection device - Google Patents

Description

The present invention relates to a technology for fastening fastening members and inspecting the axial force of the fastened fastening members.

Fasteners such as bolts and nuts are used to assemble and fasten many mechanical structures, including automobiles. If the tightening force of a fastener is lower than the target tightening force, the fastener is more likely to loosen and its fatigue strength decreases. Therefore, it is important for safety that the fastener is precisely tightened with the target tightening force.

As a technique for ensuring safety, a method is known in which the tightening force is detected and monitored during the tightening process in which a fastener is tightened, and the axial force is inspected to confirm whether the desired tightening force is obtained after tightening.

Patent No. 6381840

However, if detection during tightening and inspection is performed using a single sensor mounted on the tightening device, the independence of the inspection cannot be guaranteed. In addition, if the axial force is inspected after tightening using an inspection device separate from the tightening device, the inspection process becomes cumbersome.

The present invention aims to satisfy the requirement for inspection independence while minimizing the complexity of the inspection process.

In order to solve the above problems, the fastening and inspection device according to the present invention is (1) a fastening and inspection device equipped with a mechanism capable of performing a fastening process for fastening a fastening member to a fastened object and an inspection process for inspecting the axial force of the fastening member fastened to the fastened object, and is characterized by having multiple independent sensors capable of detecting the fastening force of the fastening member during the fastening process and the inspection process.

(2) The tightening/inspection device described in (1) above is characterized in that the number of the multiple sensors is two, the device has a controller that receives output signals output from each of the sensors, and a notification unit that notifies the tightening/inspection device of a malfunction, and the controller notifies the malfunction via the notification unit when the output difference between the sensors during the tightening process increases to a predetermined value or more.

(3) The fastening and inspection device described in (2) above further includes a memory unit, one of the two sensors is a first sensor used to monitor the fastening force during the fastening process, and the other is a second sensor used to monitor the axial force during the inspection process, and the memory unit stores in advance the relationship between the sensor output during the fastening process and the rotation angle of a motor that generates power for performing the fastening process as relationship information, and when the sensor output difference during the fastening process increases to a predetermined value or more, if the relationship between the output of the first sensor and the rotation angle deviates from the relationship information, the controller determines that the first sensor is faulty, and if the relationship between the output of the first sensor and the rotation angle does not deviate from the relationship information, the fastening and inspection device described in (2) above.

(4) The tightening and inspection device described in (2) above, characterized in that one of the two sensors is a first sensor used to monitor the tightening force during the tightening process, and the other is a second sensor used to monitor the axial force during the inspection process, and the controller determines that the first sensor is faulty if the time required for the tightening process does not satisfy a predetermined tightening time when the output difference between the sensors during the tightening process increases to a predetermined value or more, and determines that the second sensor is faulty if the predetermined tightening time is satisfied.

(5) The tightening/inspection device described in (1) above is characterized in that the number of the multiple sensors is two, the device has a controller that receives output signals output from each of the sensors, and an alarm unit that notifies the tightening/inspection device of a malfunction, and the controller notifies the malfunction via the alarm unit when the output difference between the sensors increases to a predetermined value or more during the inspection process.

(6) The tightening and inspection device described in (5) above further includes a memory unit, one of the two sensors is a first sensor used to monitor the tightening force during the tightening process, and the other is a second sensor used to monitor the axial force during the inspection process, and the memory unit stores in advance the relationship between the sensor output during the inspection process and the rotation angle of a motor that generates power for performing the inspection process as relationship information, and when the sensor output difference during the inspection process increases to a predetermined value or more, if the relationship between the output of the second sensor and the rotation angle deviates from the relationship information, the controller determines that the second sensor is faulty, and if the relationship between the output of the second sensor and the rotation angle does not deviate from the relationship information, the tightening and inspection device described in (5) above.

(7) The tightening and inspection device described in (2) above, characterized in that one of the two sensors is a first sensor used to monitor the tightening force during the tightening process, and the other is a second sensor used to monitor the axial force during the inspection process, and the controller determines that the second sensor is faulty if the time required for the inspection process does not satisfy a predetermined tightening time when the output difference between the sensors during the inspection process increases to a predetermined value or more, and determines that the first sensor is faulty if the time required for the inspection process satisfies the predetermined tightening time.

(8) The number of the multiple sensors is three or more, and the device has a controller that receives output signals output from each of the sensors, and a notification unit that notifies of a sensor failure, and the controller notifies of a failure via the notification unit when an output difference between one sensor and the remaining sensors during the fastening process and/or the inspection process is equal to or greater than a predetermined value.

According to the present invention, in a dual-purpose fastening inspection device that is mechanically capable of both tightening and axial force inspection, by implementing at least two different sensors, it is possible to suppress the complexity of the inspection process while satisfying the independence of the inspection.

FIG. 2 is a cross-sectional view of the fastening inspection device (first embodiment). FIG. 2 is a cross-sectional view of a fastened body and a bolt (first embodiment). FIG. 2 is a perspective view of a bolt (first embodiment). FIG. 13 is a perspective view of a bolt (modified example). FIG. 11 is a cross-sectional view of a fastened body and a bolt (modified example). 10A to 10C are explanatory views of the operation of the fastening inspection device of the first embodiment during fastening (first half). 13A to 13C are explanatory views of the operation of the fastening inspection device of the first embodiment during fastening (second half). 1 is a graph showing the relationship between the rotation angle of a bolt and the axial force and tensile force. 11A to 11C are explanatory diagrams of the operation of the fastening inspection device during inspection (first embodiment). FIG. 4 is a cross-sectional view of a fastening inspection device (second embodiment). 1A to 1C are diagrams illustrating a temporary fastening process. 4D and 4E show a temporary fastening process, and 4F shows a process of applying a tensile force. 5(g) to 5(j) are diagrams showing the seating process of the nut when a tensile force P is applied. 13(k) shows the seating process, (l) shows the final tightening process, and (m) and (o) show the removal process of the fastening inspection device. FIG. 1 is a diagram showing the relationship between the tensile force and the tightening force of a bolt and nut tightening body when the nut is rotated in the screwing direction together with the drive socket from a seated state. FIG. 11 is a diagram showing the relationship between the tensile force and the tightening force when only the nut is loosened from a state in which the tightening force has reached a target tightening force. 13A to 13C are explanatory views of the operation of the fastening inspection device during inspection (second embodiment);

Figure 1 is a cross-sectional view showing the fastening inspection dual purpose device 100. The fastening inspection dual purpose device 100 includes a first motor 10, a second motor 30, and a case 50. The first motor 10 and the second motor 30 are independent of each other, and are driven and controlled by a controller 5. That is, the controller 5 can, for example, read a program in a memory and control the first motor 10 and the second motor 30 independently. The controller 5 can, for example, be a CPU (central processing unit).

The case 50 includes a body 51 and a base 52, the upper end of which is formed in a concave shape and is fixed to the lower surface of the body 51. The body 51 houses the first reducer 11 and the second reducer 31. The first reducer 11 includes an output shaft 11a. The output shaft 11a is formed in a tubular shape, and a power transmission part 12 is inserted and fixed to the tubular part of the output shaft 11a. This power transmission part 12 rotates together with the output shaft 11a. The lower end of the power transmission part 12 protrudes downward from the output shaft 11a, and this protruding part extends toward the inside of the tube of the tubular bit holder 13 that extends in the vertical direction and is fixed thereto. Therefore, the rotational output obtained by the output shaft 11a is transmitted to the bit holder 13 via the power transmission part 12, and the output shaft 11a and the bit holder 13 can be rotated together.

The output shaft 11a and the bit holder 13 are arranged approximately coaxially and are supported rotatably by the bearing 14. A magnet 13a is provided inside the bit holder 13, and a bit 13b for rotating a bolt is attracted to the magnet 13a. The bit 13b extends downward and protrudes from the lower end of the bit holder 13. In the above-mentioned configuration, the bit holder 13 is rotated to rotate the bit 13b around an axis extending in the vertical direction.

The magnet 13a and bit 13b are housed within the tube of the bit holder 13 so that they can slide up and down, and a spring 13c is interposed between the magnet 13a and the power transmission component 12. The spring 13c is arranged along the inner wall of the bit holder 13. When the magnet 13a slides in a direction approaching the power transmission component 12, the spring 13c is charged in the contracting direction. With the above-mentioned configuration, the bit 13b can be moved up and down to follow the bolt 70 described later.

The bit 13b is worn out due to the load applied when the bolt is rotated. In this embodiment, the bit 13b is attached to the magnet 13a and fixed in place, so that the bit 13b can be easily replaced when worn out.

The first motor 10 is provided with a rotation angle sensor RS1, which detects the rotation angle of the bolt 70 at a predetermined cycle. The detected rotation angle is transmitted to the controller 5. The second motor 30 is provided with a rotation angle sensor RS2, which detects the rotation angle of the tension rod 15 (described below) at a predetermined cycle. The detected rotation angle is transmitted to the controller 5.

The rotational force of the second motor 30 is transmitted to the tension rod 15 via the second reduction gear 31, the pinion gear 32, and the idle gear 33. That is, the drive gear 151 and the idle gear 33 formed on the outer circumferential surface of the tension rod 15 are engaged with each other, and by operating the second motor 30, the tension rod 15 can be rotated around an axis extending in the vertical direction.

The bearings 34 are installed to receive the load applied to the pinion gear 32 and the idle gear 33 when the second motor 30 rotates. The idle gear 33 is rotated by an idle shaft 35 that extends in the vertical direction.

The tension rod 15 has a tension housing 15a for housing the bit holder 13 and the bearing 14. A gap is formed between the bit holder 13 and the tension rod 15 to allow the tension rod 15 to rotate. The tension rod 15 is rotatably supported by a bearing 16 and a thrust bearing 17.

A female threaded portion 15a1 is formed on the inner diameter surface at the lower end of the tension rod 15. This female threaded portion 15a1 screws into the male threaded portion of the bolt formed on the head of the bolt when the bolt is tensioned, as will be described in detail later.

The supporter 18 has a supporter housing portion 18a for housing the tension rod 15. The upper end of the supporter 18 contacts the thrust bearing 17, and the lower end of the supporter 18 extends further downward than the lower end of the tension rod 15. Therefore, when the entire fastening inspection/use device 100 descends toward the fastened object H, the lower end of the supporter 18 abuts against the fastened object H. A gap is formed between the tension rod 15 and the supporter 18 to allow the tension rod 15 to rotate.

The supporter 18 is provided with two sensors 181 and 182 that are independent of each other. The sensors 181 and 182 can be provided in positions aligned in the axial direction. The sensor 181 includes a strain body 181a and a strain gauge 181b. The strain body 181a is formed in a cylindrical shape with a reduced diameter at its middle part in the axial direction. The strain gauge 181b is attached to the middle part of the strain body 181a. The sensor 182 includes a strain body 182a and a strain gauge 182b. The strain body 182a can be configured in the same way as the strain body 181a.

However, a sensor may be constructed by attaching two strain gauges to different positions on the super-strain body 181a (super-strain body 182a). In this case, the sensor 182 (sensor 181) can be omitted.

During tensioning of the bolt, the strain body 181a (strain body 182a) receives an upward force equivalent to the tensile force transmitted from the supporter 18, and is distorted in the compression direction within the elastic deformation range. The strain gauge 181b (strain gauge 182b) changes its resistance value according to the strain of the strain body 181a (strain body 182a), and changes the output voltage output to the controller 5. The controller 5 calculates the tensile force of the threaded portion of the bolt based on the amount of change in the output voltage of the strain gauge 181b (strain gauge 182b).

The controller 5 monitors the outputs of the sensors 181 and 182 when the bolt is tightened and when the axial force is tested, and when the difference in the outputs of these sensors increases, it can be determined that one of the sensors has failed. That is, since the sensors have their own inherent errors, the sensor outputs differ under normal conditions. The difference in the sensor outputs under normal conditions is stored as an error, and when the difference in the sensor outputs detected when the bolt is tightened and when the axial force is tested exceeds the error and becomes greater than a predetermined value, it can be determined that one of the sensors has failed. The predetermined value differs depending on the error, so it is not particularly limited. The process of determining failure may be performed both when the bolt is tightened and when the axial force is tested, or only one of them.

The fastening inspection dual-purpose device 100 can be equipped with an alarm unit 20. If either of the sensors is malfunctioning, the alarm unit 20 can notify the user of the malfunction by outputting a sound or turning on a lamp. However, the alarm means used by the alarm unit 20 is not limited to outputting a sound or turning on a lamp, and other methods that can notify the user of the malfunction (for example, a method of displaying on a display) may be used. The alarm unit 20 can be controlled by the controller 5.

In this way, by monitoring the difference between the outputs of the two different sensors 181 and 182, sensor abnormalities can be detected early. After a sensor abnormality is detected, the use of the fastening inspection device 100 can be stopped, thereby preventing a large number of fastening defects or inspection defects from occurring.

Here, one of sensors 181 and 182 can be used for axial force management during tightening, and the other can be used for axial force management during axial force inspection. In this embodiment, sensor 181 is used as the axial force management sensor during tightening, and sensor 182 is used as the axial force management sensor during inspection. However, sensor 182 can also be used as the axial force management sensor during tightening, and sensor 181 can be used as the axial force management sensor during inspection.

Here, if the above-mentioned failure (increase in the sensor output difference) is detected during bolt tightening, the failed sensor can be identified based on the rotation angle detected by the rotation angle sensor RS1. This point will be specifically described. The relationship between the rotation angle of the bolt 70 and the sensor output until the bolt 70 is normally tightened is checked in advance as relationship information (hereinafter also referred to as normal data) and stored in the memory unit 5a. If the relationship between the sensor output (in this embodiment, the output of sensor 181) and the rotation angle during actual tightening deviates from the normal data, it is determined that the control sensor during tightening (sensor 181 in this embodiment) is faulty, and if the relationship between the sensor output (in this embodiment, the output of sensor 181) and the rotation angle during actual tightening does not deviate from the normal data, it is determined that the control sensor during inspection (sensor 182 in this embodiment) is faulty.

It is also possible to identify the faulty sensor from the tightening time rather than the rotation angle. That is, the time it takes for the bolt 70 to be tightened normally (hereinafter also referred to as the normal tightening time) is checked in advance, and if the tightening work is completed before the normal tightening time or the tightening work is not completed even after the normal tightening time has elapsed, it can be determined that the control sensor during tightening (sensor 181 in this embodiment) is faulty. On the other hand, if the tightening work is completed within the normal tightening time, it can be determined that the control sensor during inspection (sensor 182 in this embodiment) is faulty. The normal tightening time is a period that has a range from minimum to maximum. The normal tightening time can be stored in the memory unit 5a.

In addition, if the above-mentioned failure (increase in the sensor output difference) is detected during the inspection, the failed sensor can be identified based on the rotation angle detected by the rotation angle sensor RS2. This point will be specifically described. The relationship between the rotation angle and the sensor output until the axial force inspection of the bolt 70 is completed is checked in advance as relationship information (hereinafter also referred to as normal data) and stored in the memory unit 5a. If the relationship between the sensor output (in this embodiment, the output of sensor 182) and the rotation angle during the actual axial force inspection deviates from the normal data, it is determined that the control sensor during the axial force inspection (sensor 182 in this embodiment) is faulty, and if the relationship between the sensor output (in this embodiment, the output of sensor 182) and the rotation angle during the actual axial force inspection does not deviate from the normal data, it is determined that the control sensor during the tightening (sensor 181 in this embodiment) is faulty. As with the tightening, a method of identifying the failed sensor based on the inspection time may be adopted.

In this way, by providing separate sensors for tightening the bolt and for inspecting the axial force after tightening, the independence of the inspections can be ensured. In other words, if there is only one sensor, the same sensor must be used to measure the axial force during tightening and during inspection, and therefore the independence of the inspections cannot be guaranteed. According to the configuration of this embodiment, the sensors are provided separately, so the independence of the inspections can be guaranteed.

(Variation 1)
In the above embodiment, the number of sensors is two, but it may be three or more. These sensors can be arranged in the axial direction. For example, three different sensors (sensor 181, sensor 182, and sensor 183) may be used to detect the axial force. In this case, the axial force measuring sensor during tightening and the axial force measuring sensor during inspection can be arbitrarily selected from these sensors 181 to 183. Since the axial force measuring sensor during tightening and the axial force measuring sensor during inspection are independent of each other, the independence of the inspection can be guaranteed. In addition, the sensor outputs of these sensors 181 to 183 are monitored, and when the output difference between any one sensor output and the remaining two sensor outputs exceeds the error range and expands to a predetermined value or more, the sensor whose sensor output has deviated can be determined to be faulty. Note that this modified example 1 can also be applied to the second embodiment described later.

When the number of sensors is three or more, each sensor can be composed of an ultra-strain body and a strain gauge. In addition, three or more independent sensors can be realized by attaching three or more strain gauges to one ultra-strain body.

Next, the bolt fastened by the fastening inspection dual-purpose device 100 of this embodiment will be described with reference to Figures 2 and 3. Figure 2 is a cross-sectional view of the bolt and the fastened object, and Figure 3 is a perspective view of the bolt. The bolt 70 is a hexagon socket bolt, and is composed of a bolt shank 71 and a bolt head 72. A male thread is formed on the bolt shank 71. The fastened object H (in other words, the work) is composed of fastened objects H1 and H2 stacked in the vertical direction, and bolt holes H1a and H2a are formed in these fastened objects H1 and H2, respectively.

The bolt 70 is fastened to the fastened body H by inserting the bolt 70 into the bolt holes H1a and H2a and screwing the nut 80 onto the bolt shank 71 that protrudes downward from the end face of the fastened body H (H2). However, the present invention can also be applied to a fastening body consisting of only the bolt 70 without the nut 80. In this case, the bolt 70 can be fastened to the fastened body H by forming a female thread portion on the periphery of the bolt hole H2a that screws into the male thread portion of the bolt shank 71.

A hexagonal insertion hole 72b (corresponding to the engaged part) is formed on the top surface of the bolt head 72. The lower end of the bit 13b (corresponding to the engaging part) is inserted into this insertion hole 72b and rotated to fasten the bolt 70 to the fastened object H. The bolt head male threads 72a are formed continuously and uninterrupted in the circumferential direction on the side of the bolt head 72. With the bolt head male threads 72a screwed into the tension rod female threads 15a1, the tension rod 15 can be rotated to pull the bolt 70.

Here, when the contact area between the supporter 18 and the fastened object H is S1 and the contact area between the bolt head 72 and the fastened object H is S2, it is desirable that the contact areas S1 and S2 are the same. Since surface pressure acts on the fastened object H from the seating surface of the bolt head 72 and the supporter 18, if the contact areas S1 and S2 are different (i.e., if a surface pressure difference occurs), the amount of deformation of the fastened object H will differ from that during actual bolt tightening. Furthermore, if the surface pressure difference becomes excessively large, the supporter 18 may deform and damage the fastened object H, or the difference in the amount of deformation may reduce the tightening accuracy.

In this embodiment, the insertion hole 72b is formed in a hexagonal shape, but the present invention is not limited to this, and may be other polygonal shapes such as octagonal. The present invention can also be applied to a hexagonal bolt whose bolt head shape is hexagonal. In this case, as shown in FIG. 4(a), the insertion hole 72b' is formed on the top surface of the bolt head 72', and the bolt head male thread portion 72a' is intermittently formed on the curved portion on the side surface of the bolt head 72'. In addition, the bolt head male thread portion 72a (72a') does not necessarily have to be formed over the entire area from the upper end to the lower end of the bolt head 72 (72'), and may be formed only on a part of the upper end to the lower end as long as the screwing length required to rotate the tension rod 15 is secured.

In this embodiment, the bolt 70 is rotated by inserting the bit 13b into the insertion hole 72b formed in the bolt head 72, but the present invention is not limited to this. As shown in FIG. 4(b), a protrusion 72c (corresponding to the engaged portion) may be formed on the bolt head 72 (72') and the bolt 70 may be rotated by inserting the protrusion 72c into a recess (corresponding to the engaging portion) (not shown) formed on the lower end of the bit 13b. In other words, the present invention can be widely applied to bolts in which a bolt head male thread portion is formed on the side of the bolt head and an engaged portion for engaging the engaging portion of the bit is formed on the bolt head. The present invention can also be applied to flanged bolts in which a flange is formed on the bolt head.

Next, the operation of the fastening inspection device 100 during bolt fastening will be described with reference to the operation explanatory diagrams of Figures 5 and 6. Here, in the initial state (see Figure 5(a)), the bolt 70 is temporarily fastened to the fastened object H, and the bolt head 72 is located at a temporary fastening position separated from the upper surface of the fastened object H. Also, the bit 13b is inserted into the insertion hole 72b of the bolt head 72. Note that the following control is performed by the controller 5 unless otherwise specified.

When the first motor 10 is operated, the first reducer 11, output shaft 11a, power transmission component 12, and bid holder 13 rotate, and the bit 13b held by the bid holder 13 rotates in the direction of arrow K1. When the bit 13b rotates, the bolt 70 screws downward. Here, since the fastening inspection/use device 100 is supported on a support portion (not shown) so as to be allowed to descend under its own weight, the entire fastening inspection/use device 100 descends while the bit 13b rotates, and as a result, the female threaded portion 15a1 of the tension rod and the male threaded portion 72a of the bolt head become capable of being screwed together (see FIG. 5(b)).

When the bolt 70 is further rotated and the bolt head 72 seats on the upper surface of the fastened object H, the force acting on the first motor 10 to rotate the first motor 10 increases rapidly, causing a rapid increase in the feedback torque (see FIG. 5(c)). The controller 5 detects that the bolt 70 has seated from the feedback torque of the first motor 10 and stops the first motor 10. The first motor 10 is then rotated in the reverse direction of arrow K2 to return the bolt head 72 to a position slightly spaced from the upper surface of the fastened object H (see FIG. 5(d)).

Next, the first motor 10 is stopped and the second motor 30 is operated. When the second motor 30 is operated, the tension rod 15 rotates in the direction of the arrow K1 while the entire fastening inspection device 100 moves downward, and the female threaded portion 15a1 of the tension rod and the male threaded portion 72a of the bolt head screw together (see FIG. 6(e)). At this time, the bit 13b slides upward inside the bit holder 13 against the elastic force of the spring 13c.

When the tension rod 15 is further rotated and threaded downward, the lower end of the supporter 18 comes into contact with the upper surface of the fastened object H, stopping the downward movement of the fastening inspection device 100. Even if an attempt is made to rotate the tension rod 15 further in the direction of arrow K1, the supporter 18 is in contact with the fastened object H, so the tension rod 15 cannot be threaded downward. At this point, the bolt 70 is prohibited from rotating by the bit 13b inserted into the insertion hole 72b of the bolt head 72, so a load is applied to the bolt 70 in the pull-out direction (i.e., upward) by the tension rod 15.

However, because the supporter 18 is in contact with the fastened object H, the bolt 70 cannot be moved in the pull-out direction even if the tension rod 15 is rotated. As a result, a tensile force P acts on the nut 80 and the supporter 18 (see FIG. 6(f)). Here, because the upper end of the supporter 18 is in contact with the thrust bearing 17, the supporter 18 is compressed by the thrust bearing 17 and the fastened object H, and this compressive force is detected by the sensor 181 as a tensile force P.

In this case, if the difference in output between sensors 181 and 182 exceeds the error range, controller 5 can determine that one of the sensors is faulty. The faulty sensor can be identified using the rotation angle detected by rotation angle sensor R1 as described above, but the details will not be repeated.

Here, when the target value of the tensile force P is defined as the target tensile force (e.g., 10 kN), in order to prevent the second motor 30 from overshooting, it is desirable to decelerate the second motor 30 as the tensile force P approaches the target tensile force, and to stop the second motor 30 when the target tensile force is reached (corresponding to the second step). This target tensile force is also the target axial force of the bolt 70.

Next, with the tensile force P applied, the first motor 10 is rotated again in the direction of the arrow K1 to seat the bolt head 72 on the fastened object H (corresponding to the third step). Here, it is desirable that the thread pitch of the female threaded portion 15a1 of the tension rod and the male thread formed on the bolt shaft portion 71 are the same. If these thread pitches were different, it would be necessary to simultaneously control the rotation of the bit 13b (i.e., the drive control of the first motor 10) and the rotation of the tension rod 15 (i.e., the drive control of the second motor 30), which would make the control complicated. On the other hand, if the thread pitches are the same, the bolt fastening operation can be completed by simply rotating the bit 13b, eliminating the need for complicated synchronization control.

Here, when the bolt head 72 comes into contact with the fastened object H, the tensile force P starts to decrease, and conversely, the axial force F of the bolt 70 increases (see Figures 6(g) and 7). The differential value of the tensile force P, dP/dθ, is constantly monitored, and when dP/dθ changes from an unstable curve (non-linear region) to a straight line, the rotation of the bit 13 is stopped (corresponding to the fourth step). Note that "dθ" corresponds to the rotation angle of the bolt 70.

Finally, the second motor 30 is rotated in the opposite direction to that used for bolt tightening, causing the tightening inspection device 100 to move away from the workpiece H, and releasing the screwed state of the bolt head 72 and the tension rod 15 (see FIG. 6(h)). At this time, the axial force F generated by the bolt 70 indicates a value close to the target tensile force, so that a highly accurate axial force F can be obtained.

Here, as shown in FIG. 7, in this embodiment, when the axial force reaches a value higher than the target axial force F, the tightening operation of the bolt 70 is stopped, and the screwed state of the bolt head 72 and the tension rod 15 is released. If the tightening operation of the bolt 70 is stopped immediately after the bolt 70 is seated on the fastened body H, and the screwed state of the bolt head 72 and the tension rod 15 is released, the axial force decreases by the elastic deformation of the bolt 70 and the fastened body H. This decrease σ corresponds to the difference between the axial force when dP/dθ changes from a curve to a straight line and the target axial force F. However, in anticipation of the decrease in the axial force after seating, the tensile force P may be set to a value higher by the decrease σ in advance, and the tightening operation of the bolt 70 may be stopped immediately after seating. In this case, when the screwed state of the bolt head 72 and the tension rod 15 is released, the axial force of the bolt 70 decreases toward the target axial force F.

Next, the operation of the fastening inspection/use device 100 during inspection will be described. FIG. 8(a) illustrates the state before the fastening inspection/use device 100 detects the axial force. The fastening inspection/use device 100 is set to a position for detecting the axial force of the bolt 70, and the second motor 30 is operated. By operating the second motor 30, the tension rod 15 rotates in the direction of the arrow K1 as shown in FIG. 8(b), and the entire fastening inspection/use device 100 moves downward, so that the female threaded portion 15a1 of the tension rod and the male threaded portion 72a of the bolt head are screwed together. At this time, the bit 13b slides upward inside the bit holder 13 against the elastic force of the spring 13c.

When the tension rod 15 is further rotated and threaded downward, the lower end of the supporter 18 comes into contact with the upper surface of the fastened object H, stopping the downward movement of the fastening inspection device 100. Even if an attempt is made to rotate the tension rod 15 further in the direction of arrow K1, the supporter 18 is in contact with the fastened object H, so the tension rod 15 cannot be threaded downward. At this point, the bolt 70 is prohibited from rotating by the bit 13b inserted into the insertion hole 72b of the bolt head 72, so a load is applied to the bolt 70 in the pull-out direction (i.e., upward) by the tension rod 15.

However, because the supporter 18 is in contact with the fastened object H, the bolt 70 cannot be moved in the pull-out direction even if the tension rod 15 is rotated. As a result, a tensile force P acts on the nut 80 and the supporter 18 (see FIG. 8(c)). When the tension rod 15 is rotated further, the tensile force P increases toward the tightening axial force and the head of the bolt 70 stretches. Then, when the tensile force P becomes greater than the tightening axial force, the entire bolt 70 stretches.

The controller 5 constantly monitors the relationship between the tensile force P and the rotation angle (amount of elongation). When the force relationship changes from "tensile force P < tightening axial force" to "tensile force P > tightening axial force", the gradient of the relationship changes, and the tightening axial force can be determined. The rotation angle is calculated by the controller 5 based on the detection result of the rotation angle sensor RS2. Here, since the upper end of the supporter 18 is in contact with the thrust bearing 17, the supporter 18 is compressed by the thrust bearing 17 and the fastened body H, and this compression force is detected by the sensors 181 and 182 as the tensile force P. At this time, if the output difference between the sensors 181 and 182 exceeds the error range and increases to a predetermined value or more, the controller 5 can determine that one of the sensors is broken. Also, as described above, the failed sensor can be identified based on the rotation angle.

Second Embodiment
(Configuration of the fastening inspection device 310)
9 is a cross-sectional view showing the fastening inspection dual purpose device 310. The fastening inspection dual purpose device 310 has a function of automatically and accurately fastening the bolt and nut fastener 301 with a target fastening force, and detects the axial force after fastening. In this respect, it is similar to the fastening inspection dual purpose device of the first embodiment.

The bolt and nut fastener 301 comprises a bolt 311 that is passed through a hole in the fastened object 313, and a nut 312 that screws into the threaded portion of the bolt 311. The nut 312 fastens the fastened object 313 together with the head of the bolt 311. The bolt 311 may be a stud bolt. A female threaded member that abuts against the fastened object 313 is screwed into one end of the stud bolt, and the nut 312 is screwed into the other end. Below, the configuration of the fastening inspection device 310 will be described, and then the fastening process of the bolt and nut fastener 301 by the fastening inspection device 310 will be described.

The case 304 of the fastening inspection device 310 includes a body 341 and a concave base 342 fixed to the underside of the body 341. A drive socket 331 for rotating the nut 312 protrudes from the underside of the case 304.

The drive socket 331 is cylindrical and is held rotatably around its axis, while being fixed in the axial direction. The opening at the lower end of the drive socket 331 is hexagonal or dodecagonal in shape to be able to hold the nut 312. The nut 312 is fitted into the opening of the drive socket 331, and the drive socket 331 is driven by the second motor 332 to rotate the nut 312.

The upper part of the drive socket 331 is located inside the base 342 and forms an expansion section 511 that expands in the radial direction. The expansion section 511 houses a bearing 512 inside. The expansion section 511 is sandwiched between bearings 513 and 514 from above and below. This fixes the drive socket 331 in the axial direction. The bearings 513 and 514 hold the drive socket 331 rotatably around the axis. The upper bearing 513 is prevented from coming off by a retaining ring 515. A gear section 516 to which driving force is transmitted from the second motor 332 is provided on the outer periphery of the expansion section 511.

The second motor 332 is attached to the upper part of the body 341 at a position radially offset from the drive socket 331. The second motor 332 is located to the side of the first motor 322, which will be described later.

The reducer 333 is attached directly below the second motor 332 in the body 341. The reducer 333 reduces the rotation input from the second motor 332 and outputs it from the output shaft 531. The reducer 333 is, for example, a two-stage planetary gear mechanism, with upper and lower internal gears fixed inside the body 341. The output of the second motor 332 is transmitted to the lower stage planetary carrier via the upper stage sun gear of the reducer 333, the pair of upper stage planetary gears, the upper stage planetary carrier, the lower stage sun gear on the output shaft of the upper stage planetary carrier, and the pair of lower stage planetary gears, and is output from the output shaft 531 of the lower stage planetary carrier. The output shaft of the second motor 332, the output shaft of the upper stage planetary carrier, and the output shaft 531 of the lower stage planetary carrier are coaxial.

A pinion gear 334 is provided on the output shaft 531 at a portion disposed within the base 342. An idle gear 335 is rotatably provided within the base 342 between the pinion gear 334 and the gear portion 516 of the drive socket 331. The output of the second motor 332 is transmitted to the gear portion 516 of the drive socket 331 via the reducer 333, the pinion gear 334 of the reducer 333, and the idle gear 335, thereby rotating the drive socket 331. The upper and lower portions of the pinion gear 334 on the output shaft 531 are held by bearings 541 and 542, respectively. The upper bearing 542 is prevented from coming loose by a retaining ring 543.

The nut holder 323 is cylindrical with a bottom. The nut holder 323 is fitted inside the drive socket 331 and is held by the drive socket 331 so that it can rotate around its axis. The upper part of the nut holder 323 is held by a bearing 512. The expanding flange 431 at the upper end of the nut holder 323 is supported by the expanding part 511, and the upper surface is pressed against the sensor 324b (described later) via the thrust bearing 432.

The nut holder 323 is provided at a set position in the axial direction with the bottom 433 spaced apart from the lower end of the drive socket 331. In the center of the bottom 433 is a circular hole 434 through which the bolt 311 passes. During the tensioning process in which a tensile force is applied to the threaded portion of the bolt 311, the bottom 433 of the nut holder 323 restricts the movement of the nut 312 upward (toward the tip end of the threaded portion of the bolt 311).

The tension rod 321 is elongated and cylindrical in shape. The tension rod 321 is fitted inside the nut holder 323 and can rotate around its axis. The tension rod 321 is the output shaft of the reducer 325 to which the output of the first motor 322 is input, and is fixed in the axial direction.

The tension rod 321, nut holder 323, and drive socket 331 are arranged coaxially. A screw hole 411 is provided at the center of the lower end surface of the tension rod 321. The threaded portion of the bolt 311 is fitted into the screw hole 411. The tension rod 321 is fitted into the threaded portion of the bolt 311 closer to the tip than the nut 312.

The first motor 322 is disposed on the upper part of the body 341 and is attached in a position coaxial with the tension rod 321.

The reducer 325 reduces the rotation input from the first motor 322 and outputs it from the tension rod 321. The reducer 325 may be, for example, a two-stage planetary gear mechanism similar to the reducer 333. The output shaft of the first motor 322 and the tension rod 321 are on the same axis.

When the tension rod 321 is rotated in one direction while fitted onto the bolt 311, an upward force (force toward the axial tip) is applied to the bolt 311. In this embodiment, this one direction is sometimes called the screwing direction, and the direction opposite to the screwing direction is sometimes called the loosening direction. During tensioning, the tension rod 321 is rotated in the screwing direction while holding down the nut 312 with the nut holder 323. This applies an upward force to the bolt 311, allowing a tensile force to be applied to the threaded portion of the bolt 311.

Sensors 324a and 324b are provided radially outside the tension rod 321 and between the reducer 325 and the nut holder 323, aligned in the axial direction. It goes without saying that these sensors 324a and 324b are provided to detect the tensile force applied to the threaded portion of the bolt 311. The sensor 324a is arranged on the reducer 325 side, and the sensor 324b is arranged on the nut holder 323 side. The sensor 324a includes a strain body 442a and a strain gauge 443a. The sensor 324b includes a strain body 442b and a strain gauge 443b. The configuration of the strain bodies 442a and 442b is the same as that of the strain body 181a in the first embodiment, so a detailed description will be omitted. The configuration of the strain gauges 443a and 443b is the same as that of the strain gauge 181b in the first embodiment, so a detailed description will be omitted. However, a sensor may be constructed by attaching two strain gauges to different positions on the strain body 442a (sensor 442b). In this case, the sensor 324b (sensor 324a) can be omitted.

During tension processing, the strain body 442a (strain body 442b) receives an upward force from the nut holder 323 that is equivalent to the tensile force, and is distorted in the compression direction within the elastic deformation range. The strain gauge 443a (strain gauge 443b) changes its resistance value according to the distortion of the strain body 442a (strain body 442b), and changes the output voltage to the controller 309. The controller 309 calculates the tensile force of the threaded portion of the bolt 311 based on the amount of change in the output voltage of the strain gauge 443. The thrust bearings 441, 432 provided above and below the sensors 324a, 324b suppress the transmission of unnecessary disturbances other than the upward force from the nut holder 323 to the sensors.

The controller 309 controls the first motor 322 and the second motor 332 independently, and performs the fastening process of the bolt-nut fastener 301 described below. The controller 309 performs the fastening process by, for example, a central processing unit (CPU) reading and executing a program in a memory. The controller 309 detects the rotational positions of the first motor 322 and the second motor 332, and the feedback torque, which is the output torque of the second motor 332.

The first motor 322 is provided with a rotation angle sensor RS1, which detects the rotation angle of the tension rod 321 at a predetermined cycle. The detected rotation angle is transmitted to the controller 309. The second motor 332 is provided with a rotation angle sensor RS2, which detects the rotation angle of the nut 312 at a predetermined cycle. The detected rotation angle is transmitted to the controller 309.

The controller 309 monitors the output of the sensors 324a and 324b when the nut is tightened and when the axial force test is performed after tightening, and when the difference in the outputs of these sensors increases, it can be determined that one of the sensors has failed. In other words, since the sensors each have their own inherent error, the sensor outputs differ under normal conditions. This difference in the sensor outputs under normal conditions is stored as an error, and when the difference in the sensor outputs detected when the bolt is tightened and during the axial force test exceeds the error and becomes greater than a predetermined value, it can be determined that one of the sensors has failed.

The fastening inspection device 310 can be equipped with a notification unit 308, similar to the first embodiment.

In this way, by monitoring the difference between the outputs of the two different sensors 324a and 324b, sensor abnormalities can be detected early. After a sensor abnormality is detected, the use of the fastening inspection device 310 can be stopped, thereby preventing a large number of fastening or inspection defects from occurring.

Here, one of sensors 324a and 324b can be used for axial force management during tightening, and the other can be used for axial force management during axial force inspection. In this embodiment, sensor 324a is used as the axial force management sensor during tightening, and sensor 324b is used as the axial force management sensor during inspection. However, sensor 324b can also be used as the axial force management sensor during tightening, and sensor 324a can be used as the axial force management sensor during inspection.

Here, if the above-mentioned failure (increase in the sensor output difference) is detected when the nut is tightened, the faulty sensor can be identified based on the rotation angle detected by the rotation angle sensor RS2. This point will be specifically described. The relationship between the rotation angle of the nut 312 and the sensor output until the nut 312 is normally tightened is checked in advance as relationship information (hereinafter also referred to as normal data) and stored in the memory unit 309a. If the relationship between the sensor output (in this embodiment, the output of sensor 324a) and the rotation angle during actual tightening deviates from the normal data, it is determined that the control sensor during tightening (in this embodiment, sensor 324a) is faulty, and if the relationship between the sensor output (in this embodiment, the output of sensor 324a) and the rotation angle during actual tightening does not deviate from the normal data, it is determined that the control sensor during inspection (in this embodiment, sensor 324b) is faulty.

It is also possible to identify the faulty sensor from the tightening time rather than the rotation angle. That is, the time it takes for the nut 312 to be tightened normally (hereinafter also referred to as the normal tightening time) is checked in advance, and if the tightening operation is completed before the normal tightening time or is not completed even after the normal tightening time has elapsed, it can be determined that the control sensor during tightening (sensor 324a in this embodiment) is faulty. On the other hand, if the tightening operation is completed within the normal tightening time, it can be determined that the control sensor during inspection (sensor 324b in this embodiment) is faulty. The normal tightening time is a period that has a range from minimum to maximum. The normal tightening time can be stored in the memory unit 309a.

Here, if the above-mentioned failure (increase in the sensor output difference) is detected during the axial force inspection, the failed sensor can be identified based on the rotation angle detected by the rotation angle sensor RS1. This point will be specifically described. The relationship between the rotation angle and the sensor output until the axial force inspection of the bolt 311 is completed is checked in advance as relationship information (hereinafter also referred to as normal data) and stored in the memory unit 309a. If the relationship between the sensor output (in this embodiment, the output of sensor 324b) and the rotation angle during the actual axial force inspection deviates from the normal data, it is determined that the control sensor during the axial force inspection (in this embodiment, sensor 324b) is broken, and if the relationship between the sensor output (in this embodiment, the output of sensor 324b) and the rotation angle during the actual axial force inspection does not deviate from the normal data, it is determined that the control sensor during tightening (in this embodiment, sensor 324a) is broken. Note that a method of identifying the failed sensor based on the inspection time may be adopted, as in the case of tightening.

In this way, by providing separate sensors for tightening the nut and for inspecting the axial force, the independence of the inspections can be ensured. In other words, if there is only one sensor, the same sensor must be used to measure the axial force during tightening and during inspection, and therefore the independence of the inspections cannot be guaranteed. According to the configuration of this embodiment, the sensors are provided separately, so the independence of the inspections can be guaranteed.

(Description of the fastening process)
The fastening process of the bolt and nut fastener 301 by the fastening inspection dual-purpose device 310 will be described below.

First, as shown in FIG. 10(a), the nut 312 fitted to the drive socket 331 is placed on the tip of the bolt 311 by a user or the like. In this state, the controller 309 receives an instruction to execute the fastening process from the user via an input device (not shown).

(Temporary fastening process)
The controller 309 first performs a provisional tightening process for the nut 312. As shown in Fig. 10(a) and Fig. 10(b), the controller 309 simultaneously drives the first motor 322 and the second motor 332. This allows the controller 309 to rotate the drive socket 331 and the tension rod 321 by the same number of rotations in the screwing direction, thereby enabling synchronous control. Since the pitch of the female threads of the nut 312 and the tension rod 321 is the same, synchronous control of the drive socket 331 and the tension rod 321 allows the drive socket 331 and the nut 312 to be simultaneously screwed into the bolt 311 by the same amount.

As shown in FIG. 10(c), when the nut 312 is seated, the force acting on the second motor 332 to rotate the second motor 332 increases rapidly, causing a rapid increase in the feedback torque. When the controller 309 determines that the nut 312 is seated from the feedback torque of the second motor 332, it stops driving the first motor 322 and the second motor 332.

To release the axial force in the tensile direction of the bolt 311 generated by the seating of the nut 312, the controller 309 drives only the second motor 332 as shown in FIG. 11(d). The controller 309 drives the second motor 332 in the reverse direction to rotate the drive socket 331 in the loosening direction. As a result, the nut 312 moves upward and, as shown in FIG. 11(e), separates from the fastened body 313 and abuts against the bottom 433 of the nut holder 323. The drive amount of the second motor 332 is set to a set amount.

(Addition of tensile force P)
Next, the controller 309 performs a process (first step) of applying a tensile force P to the threaded portion of the bolt 311. As shown in Fig. 11(f) , with the nut 312 floating above the fastened body 313, the controller 309 drives only the first motor 322 to rotate the tension rod 321 in the screwing direction. This causes an upward force to act on the bolt 311. Here, the nut holder 323 restricts the upward movement of the nut 312, and therefore the nut 312 restricts the upward movement of the bolt 311.

As shown in the enlarged view of FIG. 11(f), the threads of bolt 311 are held down by the threads of nut 312, restricting upward movement. Therefore, the upward force acting on the threads of bolt 311 acts on the threads of bolt 311 as tensile force P. In addition, the threads of nut 312, which restrict the upward movement of the threads of bolt 311, are positioned on the lower side between the threads of bolt 311. Therefore, backlash occurs between the upper surface of the threads of nut 312 and the lower surface of the threads of bolt 311.

The controller 309 drives the first motor 322 while monitoring the tensile force P with the sensor 324a until it determines that the tensile force P is equal to the target tightening force Fc. In this process (addition process of the tensile force P), if the output difference between the sensor 324a and the sensor 324b is large, it can be determined that one of the sensors has failed. Also, the failed sensor may be identified based on the output of the rotation angle sensor RS2 or the like. This point will not be described again. When the controller 309 determines that the tensile force P is equal to the target tightening force Fc, it stops the first motor 322. At this time, in reality, due to the overshoot of the first motor 322, the tensile force P becomes an excessive target tightening force Fc' that is greater than the target tightening force Fc. For example, when the target tightening force Fc is 10 kN, the first motor 322 stops at the point when the tensile force P becomes 11 kN, which is the excessive target tightening force Fc'.

(Seating process of the nut 312 with the tensile force P applied)
Next, the controller 309 performs a seating process (second step) of the nut 312 with the tensile force P applied. First, in order to set the tensile force P of the threaded portion of the bolt 311 to the target tightening force Fc, the controller 309 first drives the second motor 332 and rotates only the drive socket 331 in the screwing direction, as shown in Fig. 12(g). This moves the nut 312 downward, and the tensile force P decreases from the excessive target tightening force Fc'.

When the tensile force P decreases to the target tightening force Fc, the controller 309 also drives the first motor 322, as shown in FIG. 12(h), and synchronously controls the drive socket 331 and the tension rod 321. Through synchronous control, the tension rod 321 and the nut 312 approach the fastened body 313 while maintaining a distance from each other. Therefore, during this time, the tensile force P does not decrease.

Figure 14 shows the relationship between the tensile force P when the nut 312 is rotated in the screwing direction together with the drive socket 331 from a seated state, and the tightening force F of the bolt-nut fastener 301. Note that the controller 309 detects only the tensile force P, and does not detect the tightening force F.

When the nut 312 is seated (FIG. 12(i)), a tightening force F is generated, and as the nut 312 rotates in the tightening direction, the tightening force F increases. When the tightening force F (reaction force from the fastened body 313) acting upward on the nut 312 reaches a certain level in comparison with the tensile force P (reaction force from the nut holder 31) acting downward on the nut 312, the nut 312 starts to move upward relative to the bolt 311. That is, as shown in FIG. 12(j), the threads of the nut 312 start to move upward. Then, the distance between the tension rod 321 and the nut 312 becomes shorter, and the tensile force P starts to rise rapidly (see FIG. 14).

When the controller 309 detects a sudden increase in the tensile force P and determines from the detected tensile force that the tightening force F is in a seated state of the nut 312 similar to the target tightening force Fc, it stops driving the first motor 322 and the second motor 332, as shown in FIG. 13(k). At this time, the thread of the nut 312 is positioned away from the threads of the bolts 311 that sandwich the thread above and below. In addition, when performing the final tightening process as in this embodiment, this determination is made at the point where the tightening force F becomes slightly smaller than the target tightening force Fc. The controller 309 may detect a sudden increase in the tensile force P when dP/dθ continues to fall within a certain range, or when dP/dθ becomes larger than a set value.

As described above, in this process, the tensile force P is set to the target tightening force Fc, and then the nut 312 is tightened, and tightening is terminated when the tightening force F becomes the same as the target tightening force Fc (tensile force P). As a result, in this embodiment, the bolt-nut tightening body 301 can be tightened with high precision at the target tightening force Fc.

However, when the tension rod 321 is removed from the bolt 311 after this process is completed, the downward tensile force P (reaction force from the nut holder 31) acting on the nut 312 disappears, and an upward tightening force F (reaction force from the fastened body 313) acts on the nut 312. Because there is a gap between the threads of the nut 312 and the threads of the bolt 311 above the threads, the tightening force F moves the nut 312 upward by the amount of the gap. And, as the nut 312 moves upward, the tightening force F decreases from a state similar to the target tightening force Fc.

(Final tightening process)
Therefore, the controller 309 performs a final tightening process to eliminate any gap between the thread of the nut 312 and the thread of the bolt 311 above the thread of the nut 312. As shown in FIG. 13( l ), the controller 309 drives only the second motor 332 to rotate only the drive socket 331 in the screwing direction to tighten the nut 312.

Figure 15 shows the relationship between the tensile force P and the tightening force F when only the nut 312 is tightened after the tightening force F has reached the target tightening force Fc.

When only the nut 312 is tightened, the tightening force F increases, which causes the threads of the nut 312 to move upward relative to the threads of the bolt 311. While the threads of the nut 312 move upward and fill the gap with the threads of the bolt 311, the tensile force P and the tightening force F remain almost constant. In detail, the tightening force F increases slightly because the nut 312 is tightened slightly. Also, the distance between the tension rod 321 and the nut 312 in the bolt 311 increases slightly, so the tensile force P decreases.

When the threads of the nut 312 move upward and the gap between them disappears, and the threads of the bolt 311 come into close contact with the threads of the bolt 311, the threads of the nut 312 and the bolt 311 begin to elastically deform. At the time when this elastic deformation starts, the tightening force F becomes the target tightening force Fc. In order to achieve this state, a judgment point is set for stopping the drive of the tension rod 321 and the nut 312 in the seating process of the nut 312 in the previous stage. When the elastic deformation starts, the distance between the nut 312 and the tension rod 321 begins to increase, causing the tensile force P to suddenly decrease. Also, the tightening force F suddenly increases. The controller 309 detects the sudden decrease in the tensile force P and stops the drive of the second motor 332. This process allows the threads of the nut 312 to be held down by the threads of the bolt 311 above, while maintaining the tightening force F at approximately the target tightening force Fc.

(Removal process of the fastening inspection device 310)
Finally, the controller 309 performs a process of removing the fastening inspection dual-purpose device 310. As shown in Fig. 13(m), the controller 309 drives only the first motor 322. The controller 309 drives the first motor 322 in the reverse direction to rotate the tension rod 321 in the loosening direction until it is removed from the bolt 311. This releases the tensile force P applied to the threaded portion of the bolt 311.

When the tensile force P is released, an upward tightening force F (a reaction force from the fastened body 313) is applied to the nut 312. However, because the threads of the nut 312 are held down from above by the threads of the bolt 311, the nut 312 does not move upward, and the tightening force F, which has increased due to elastic deformation, disappears and is maintained at the target tightening force Fc.

Therefore, by performing the above fastening process, the fastening inspection device 310 can automatically fasten the bolt and nut fastener 301 with the target tightening force Fc. After that, the user removes the fastening inspection device 310 from the bolt 311, as shown in FIG. 13(o).

(effect)
In the present invention, the bolt-nut fastener 301 can be precisely fastened with a target tightening force by controlling the rotation of the tension rod 321 and the nut 312 while holding the nut 312 with the nut holder 323. In the present invention, the fastening process of the bolt-nut fastener 301 can be executed by controlling the drive of the first and second motors 22, 32 for rotating the tension rod 321 and the nut 312 while monitoring the tensile force P detected by the sensor 324. Therefore, the present invention can be easily automated.

In the present invention, the first motor 322, tension rod 321, nut holder 323, and drive socket 331 are arranged coaxially, making it possible to make the fastening inspection device 310 compact.

In the present invention, the controller 1 performs a process of applying a tensile force P to the threaded portion of the bolt 311 (first step) as a process of fastening the bolt-nut fastener 301. In this process, the controller 1 rotates the tension rod 321 in the tightening direction relative to the bolt 311 until it is determined that the tensile force P is equal to the target tightening force Fc while the nut 312 is floating from the fastened object 313. In addition, the controller 1 performs a process of seating the nut 312 (second step) as a fastening process. In this process, the controller 1 rotates the tension rod 321 and the nut 312 in the tightening direction while applying the tensile force Fc to the threaded portion of the bolt 311 until it is determined that the tightening force F is equal to the target tightening force Fc based on the detected tensile force P. In this way, in the present invention, the bolt-nut fastener 301 can be automatically fastened with a tightening force F equal to the target tightening force Fc.

In the present invention, in the process of adding the tensile force P (first step), the controller 1 stops driving the first motor 322 when the tensile force P reaches the target tightening force Fc. At this time, due to overshooting of the first motor 322, the tensile force P becomes an excessive target tightening force Fc' that is greater than the target tightening force Fc. Therefore, in the process of seating the nut 312 (second step), the controller 1 first rotates only the nut 312, and when it is determined that the tensile force P has decreased to the target tightening force Fc, it also starts rotating the tension rod 321. As a result, in the present invention, the correction of the tensile force P to the target tightening force Fc and the seating and fastening of the nut 312 can be performed continuously, thereby shortening the processing time.

(Modification)
The bottom 433 of the nut holder 323 may have any shape as long as it can hold the nut 312 from above and allow the bolt 311 to pass through. The bottom 433 may have, for example, a plurality of protrusions extending from the edge of the opening at the lower end of the nut holder 323 toward the vicinity of the central axis.

(Operation during inspection)
Next, the operation of the fastening inspection dual-purpose device 310 during inspection will be described. First, as shown in FIG. 16A, the controller 309 drives only the first motor 322 of the first motor 322 and the second motor 332 to rotate the tension rod 321 in the direction of the arrow and screw it downward. That is, the tension rod 321 is screwed downward while the threaded portion of the bolt 311 is screwed into the screw hole 411 of the tension rod 321. When the tension rod 321 is further screwed, the nut holder 323 is seated on the upper surface of the nut 312, and the feedback torque increases rapidly. The controller 309 detects that the nut holder 323 is seated from the feedback torque of the first motor 322 and stops the first motor 322.

Next, as shown in FIG. 16(b), the controller 309 drives the first motor 322 in the same direction to apply a force to the tension rod 321 to rotate it in the direction of the arrow. At this time, the nut 312 is pressed down by the nut holder 323, so a compressive force acts on the nut holder 323, and the axial force of the bolt can be detected. That is, as shown in FIG. 13(k), the axial force of the bolt can be detected based on the output of the sensor 324b detected when the bolt 311 and the nut 312 are driven to a position where the threads of the bolt 311 and the nut 312 are no longer in contact with each other. At this time, if the output difference between the sensors 324a and 324b exceeds the error range and is equal to or greater than a predetermined value, the controller 309 can determine that one of the sensors is broken, but this point has been described above and will not be described in detail.

The above-mentioned inspection makes it possible to confirm the axial force of the bolt 70. Note that as a theory for detecting the axial force, for example, the method described in Patent No. 4028254 can be used.

5 Controller 10 First motor 20 Second motor 100 Fastening inspection device

Claims (8)

A fastening inspection device having a mechanism capable of performing a fastening process of fastening a fastening member to a fastening object and an inspection process of inspecting the axial force of the fastening member fastened to the fastening object,
a first sensor used to monitor the clamping force during the fastening process;
a second sensor, independent of the first sensor, used to monitor axial force during the inspection process;
a controller that receives output signals from the first and second sensors;
a notification unit that notifies of a failure of the fastening inspection device;
A storage unit;
having
The storage unit stores in advance, as relationship information, a relationship between a sensor output during the fastening process and a rotation angle of a motor that generates power for performing the fastening process,
the controller, when a sensor output difference increases to a predetermined value or more during the fastening process, determines that the first sensor has failed and notifies the failure via the notification unit if a relationship between the output of the first sensor and the rotation angle deviates from the relationship information, and determines that the second sensor has failed and notifies the failure via the notification unit if a relationship between the output of the first sensor and the rotation angle does not deviate from the relationship information;
The fastening member is a bolt, a bolt head male thread portion is formed on a side surface of the head of the bolt, and an engaged portion is formed on a top surface of the head,
The mechanism comprises:
A tension rod having a rod female thread portion that screws into the bolt head male thread portion;
a bit disposed inside the tension rod so as to be movable up and down and having an engaging portion that engages with the engaged portion, the bit rotating the bolt around an axis extending up and down when the engaged portion and the engaging portion are engaged with each other;
a supporter that is arranged at a position surrounding the tension rod in the circumferential direction and has a lower end that protrudes downward beyond the lower end of the tension rod;
The bit and the tension rod are rotatable independently of each other.
A fastening inspection device characterized by the above. A fastening inspection device having a mechanism capable of performing a fastening process of fastening a fastening member to a fastening object and an inspection process of inspecting the axial force of the fastening member fastened to the fastening object,
a first sensor used to monitor the clamping force during the fastening process;
a second sensor, independent of the first sensor, used to monitor axial force during the inspection process;
a controller that receives output signals from the first and second sensors;
a notification unit that notifies of a failure of the fastening inspection device;
having
When the output difference of the sensors increases to a predetermined value or more during the engagement process, if the time required for the engagement process does not satisfy a predetermined engagement time, the controller determines that the first sensor has failed and notifies the failure via the notification unit, and if the predetermined engagement time is satisfied, determines that the second sensor has failed and notifies the failure via the notification unit;
The fastening member is a bolt, a bolt head male thread portion is formed on a side surface of the head of the bolt, and an engaged portion is formed on a top surface of the head,
The mechanism comprises:
A tension rod having a rod female thread portion that screws into the bolt head male thread portion;
a bit disposed inside the tension rod so as to be movable up and down and having an engaging portion that engages with the engaged portion, the bit rotating the bolt around an axis extending up and down when the engaged portion and the engaging portion are engaged with each other;
a supporter that is arranged at a position surrounding the tension rod in the circumferential direction and has a lower end that protrudes downward beyond the lower end of the tension rod;
The bit and the tension rod are rotatable independently of each other.
A fastening inspection device characterized by the above. A fastening inspection device having a mechanism capable of performing a fastening process of fastening a fastening member to a fastening object and an inspection process of inspecting the axial force of the fastening member fastened to the fastening object,
a first sensor used to monitor the clamping force during the fastening process;
a second sensor, independent of the first sensor, used to monitor axial force during the inspection process;
a controller that receives output signals from the first and second sensors;
a notification unit that notifies of a failure of the fastening inspection device;
A storage unit;
having
The storage unit stores in advance, as relationship information, a relationship between a sensor output during the inspection process and a rotation angle of a motor that generates power for performing the inspection process,
the controller, when an output difference between the sensors increases to a predetermined value or more during the inspection process, determines that the second sensor is faulty and notifies the fault via the notification unit if the relationship between the output of the second sensor and the rotation angle deviates from the relationship information, and determines that the first sensor is faulty and notifies the fault via the notification unit if the relationship between the output of the second sensor and the rotation angle does not deviate from the relationship information;
The fastening member is a bolt, a bolt head male thread portion is formed on a side surface of the head of the bolt, and an engaged portion is formed on a top surface of the head,
The mechanism comprises:
A tension rod having a rod female thread portion that screws into the bolt head male thread portion;
a bit disposed inside the tension rod so as to be movable up and down and having an engaging portion that engages with the engaged portion, the bit rotating the bolt around an axis extending up and down when the engaged portion and the engaging portion are engaged with each other;
a supporter that is arranged at a position surrounding the tension rod in the circumferential direction and has a lower end that protrudes downward beyond the lower end of the tension rod;
The bit and the tension rod are rotatable independently of each other.
A fastening inspection device characterized by the above. A fastening inspection device having a mechanism capable of performing a fastening process of fastening a fastening member to a fastening object and an inspection process of inspecting the axial force of the fastening member fastened to the fastening object,
a first sensor used to monitor the clamping force during the fastening process;
a second sensor, independent of the first sensor, used to monitor axial force during the inspection process;
a controller that receives output signals from the first and second sensors;
a notification unit that notifies of a failure of the fastening inspection device;
having
When the output difference of the sensors increases to a predetermined value or more during the inspection process, if the time required for the inspection process does not satisfy a predetermined engagement time, the controller determines that the second sensor has failed and notifies the failure via the notification unit, and if the predetermined engagement time is satisfied, determines that the first sensor has failed and notifies the failure via the notification unit;
The fastening member is a bolt, a bolt head male thread portion is formed on a side surface of the head of the bolt, and an engaged portion is formed on a top surface of the head,
The mechanism comprises:
A tension rod having a rod female thread portion that screws into the bolt head male thread portion;
a bit disposed inside the tension rod so as to be movable up and down and having an engaging portion that engages with the engaged portion, the bit rotating the bolt around an axis extending up and down when the engaged portion and the engaging portion are engaged with each other;
a supporter that is arranged at a position surrounding the tension rod in the circumferential direction and has a lower end that protrudes downward beyond the lower end of the tension rod;
The bit and the tension rod are rotatable independently of each other.
A fastening inspection device characterized by the above. A fastening inspection device having a mechanism capable of performing a fastening process of fastening a fastening member to a fastening object and an inspection process of inspecting the axial force of the fastening member fastened to the fastening object,
a first sensor used to monitor the clamping force during the fastening process;
a second sensor, independent of the first sensor, used to monitor axial force during the inspection process;
a controller that receives output signals from the first and second sensors;
a notification unit that notifies of a failure of the fastening inspection device;
A storage unit;
having
The storage unit stores in advance, as relationship information, a relationship between a sensor output during the fastening process and a rotation angle of a motor that generates power for performing the fastening process,
the controller, when a sensor output difference increases to a predetermined value or more during the fastening process, determines that the first sensor has failed and notifies the failure via the notification unit if a relationship between the output of the first sensor and the rotation angle deviates from the relationship information, and determines that the second sensor has failed and notifies the failure via the notification unit if a relationship between the output of the first sensor and the rotation angle does not deviate from the relationship information;
The fastening members are bolts and nuts,
The mechanism comprises:
A drive socket having a cylindrical shape and having an opening at a lower end side for holding the nut;
a nut holder having a bottomed cylindrical shape, disposed inside the drive socket, with the bolt passing through its bottom, and restricting the movement of the nut held by the drive socket toward the tip end of the threaded portion of the bolt by means of the bottom;
A tension rod is disposed inside the nut holder, and has a screw hole on a lower end surface into which a tip side of the threaded portion is screwed with respect to the nut;
having
The tension rod and the drive socket are rotatable independently of each other.
A fastening inspection device characterized by the above. A fastening inspection device having a mechanism capable of performing a fastening process of fastening a fastening member to a fastening object and an inspection process of inspecting the axial force of the fastening member fastened to the fastening object,
a first sensor used to monitor the clamping force during the fastening process;
a second sensor, independent of the first sensor, used to monitor axial force during the inspection process;
a controller that receives output signals from the first and second sensors;
a notification unit that notifies of a failure of the fastening inspection device;
having
When the output difference of the sensors increases to a predetermined value or more during the engagement process, if the time required for the engagement process does not satisfy a predetermined engagement time, the controller determines that the first sensor has failed and notifies the failure via the notification unit, and if the predetermined engagement time is satisfied, determines that the second sensor has failed and notifies the failure via the notification unit;
The fastening members are bolts and nuts,
The mechanism comprises:
A drive socket having a cylindrical shape and having an opening at a lower end side for holding the nut;
a nut holder having a bottomed cylindrical shape, disposed inside the drive socket, with the bolt passing through its bottom, and restricting the movement of the nut held by the drive socket toward the tip end of the threaded portion of the bolt by means of the bottom;
A tension rod is disposed inside the nut holder, and has a screw hole on a lower end surface into which a tip side of the threaded portion is screwed with respect to the nut;
having
The tension rod and the drive socket are rotatable independently of each other.
A fastening inspection device characterized by the above. A fastening inspection device having a mechanism capable of performing a fastening process of fastening a fastening member to a fastening object and an inspection process of inspecting the axial force of the fastening member fastened to the fastening object,
a first sensor used to monitor the clamping force during the fastening process;
a second sensor, independent of the first sensor, used to monitor axial force during the inspection process;
a controller that receives output signals from the first and second sensors;
a notification unit that notifies of a failure of the fastening inspection device;
A storage unit;
having
The storage unit stores in advance, as relationship information, a relationship between a sensor output during the inspection process and a rotation angle of a motor that generates power for performing the inspection process,
the controller, when a sensor output difference increases to a predetermined value or more during the inspection process, determines that the second sensor has failed and notifies the failure via the notification unit if the relationship between the output of the second sensor and the rotation angle deviates from the relationship information, and determines that the first sensor has failed and notifies the failure via the notification unit if the relationship between the output of the second sensor and the rotation angle does not deviate from the relationship information;
The fastening members are bolts and nuts,
The mechanism comprises:
A drive socket having a cylindrical shape and having an opening at a lower end side for holding the nut;
a nut holder having a bottomed cylindrical shape, disposed inside the drive socket, with the bolt passing through its bottom, and restricting the movement of the nut held by the drive socket toward the tip end of the threaded portion of the bolt by means of the bottom;
A tension rod is disposed inside the nut holder, and has a screw hole on a lower end surface into which a tip side of the threaded portion is screwed with respect to the nut;
having
The tension rod and the drive socket are rotatable independently of each other.
A fastening inspection device characterized by the above. A fastening inspection device having a mechanism capable of performing a fastening process of fastening a fastening member to a fastening object and an inspection process of inspecting the axial force of the fastening member fastened to the fastening object,
a first sensor used to monitor the clamping force during the fastening process;
a second sensor, independent of the first sensor, used to monitor axial force during the inspection process;
a controller that receives output signals from the first and second sensors;
a notification unit that notifies of a failure of the fastening inspection device;
having
When the output difference of the sensors increases to a predetermined value or more during the inspection process, if the time required for the inspection process does not satisfy a predetermined engagement time, the controller determines that the second sensor has failed and notifies the failure via the notification unit, and if the predetermined engagement time is satisfied, determines that the first sensor has failed and notifies the failure via the notification unit;
The fastening members are bolts and nuts,
The mechanism comprises:
A drive socket having a cylindrical shape and having an opening at a lower end side for holding the nut;
a nut holder having a bottomed cylindrical shape, disposed inside the drive socket, with the bolt passing through its bottom, and restricting the movement of the nut held by the drive socket toward the tip end of the threaded portion of the bolt by means of the bottom;
A tension rod is disposed inside the nut holder, and has a screw hole on a lower end surface into which a tip side of the threaded portion is screwed with respect to the nut;
having
The tension rod and the drive socket are rotatable independently of each other.
A fastening inspection device characterized by the above.