JP2000301474A - Automatic bolt fastening method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge fastening state of a bolt in real time to reduce poor fastening by pressing a bolt by a socket, then reversely rotating the socket to detect that the bolt is put in the socket utilizing displacement of the socket by nearly socket hole depth. SOLUTION: When a nut runner 103 is reversely rotated, by the lead angle of the contact face of the screw thread of the male screw on the lowermost part of a bolt 106 and the female screw on the uppermost part of a fastened object 104, the bolt 106 is gradually elevated, and when the screw reaches a point beginning engagement, the screw suddenly falls by the length of one pitch. At this time, displacement in a fixed time becomes nearly equal to the length of one pitch of the screw, and the beginning point of screwing-in is detected. Because the position of surely meeting the thread ridge and the root of the male screw and the female screw can be detected as the beginning point of screwing-in, a trouble such as oblique insert of a bolt or seizure of screw thread as the most popular troubles in the case of automatic bolt fastening is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic bolt tightening method, and more particularly to an automatic bolt tightening method that controls a bolt tightening state in a stable and high-speed manner by controlling not only a torque but also a displacement of a socket. It relates to the fastening method.

[0002]

2. Description of the Related Art A conventional bolt tightening method is disclosed in
No. -1263. The configuration of this conventional technique will be described with reference to FIG.

As shown in FIG. 9, a holding plate 1 integrally includes a drive motor 2 and a torque sensor 3 and is vertically movable. A casing 4 is integrally provided below the holding plate 1. A drive shaft 5 of the drive motor 2 is provided in the casing 4. The drive shaft 5 is provided with a moving shaft 8 to which a socket 7 for rotating a bolt 6 is connected via a sliding portion 9 so as to be vertically movable and rotatable.

Since the spring 10 is mounted in a compressed state between the upper end 4a of the casing 4 and the upper end of the moving shaft 8, the moving shaft 8 is constantly urged downward. A movable sensor 20 made of a magnetic material core is provided on the outer periphery of the upper end of the upper moving shaft 8, and an inner wall 4 a of the casing 4 is provided.
A is provided to face the fixed sensor 21 including three ring-shaped coils provided in A. A linear sensor 22 is constituted by the movable sensor 20 and the fixed sensor 21, and the linear sensor 22 can detect the vertical movement of the moving shaft 8, that is, the socket 7. The linear sensor 22 is connected to a processing circuit unit 24, and is configured so that the position of the movable sensor 20 can be extracted as a voltage by the processing circuit unit 24.

Next, the operation of the conventional technique will be described. The drive motor 2 rotates at the same time that the socket 7 is fitted to the bolt 6 on the base 11 such as an engine, and the bolt 6 is instantly tightened. In this case, the linear sensor detects the lowering of the moving shaft 8 which moves down together with the socket 7, and confirms that the predetermined amount of lowering has been performed, and detects the completion of the tightening of the bolt 6. Further, simultaneously with confirming the lowering of the socket 7 by the linear sensor 22, the completion of the tightening of the bolt 6 can be confirmed by detecting the signal of the torque sensor 3.

[0006]

However, according to the prior art, the drive motor 2 rotates at the same time when the socket 7 is fitted to the bolt 6 on the base 11 such as an engine, and the bolt 6 is instantly tightened. Therefore, for example, when the male and female threads of the base 11 of the engine or the like do not match with the peaks and valleys of the bolt, there is a problem that a fastening failure such as an oblique insertion of the bolt or seizure of the thread occurs.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problem, the present invention judges the tightening state of a bolt in real time, and tightens the bolt at a high speed in accordance with the tightening state to reduce an inferior tightening. It is intended to provide a bolt tightening method.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, a bolt is automatically tightened by a socket which is rotated by a nut runner and pressed downward by a biasing force of a spring. In the above automatic bolt tightening method, after the bolt is pressed by the socket, when the socket is rotated in the reverse direction, the socket is displaced downward substantially by the depth of the socket hole, so that the bolt enters the socket. The automatic bolt tightening method is characterized in that the automatic bolt tightening method is adapted to detect that

According to the automatic bolt tightening method having such a configuration, there is an excellent effect that it is possible to reliably detect that the bolt has entered the socket. In addition, since the socket is rotated not in the forward direction but in the reverse direction so that the bolt is inserted into the socket, the bolt is not tightened. This has an excellent effect that no troubles that lead to the problem occur.

In order to achieve the above object, an invention according to a second aspect of the present invention is directed to an automatic bolt tightening method wherein a bolt is automatically tightened by a socket which is rotated by a nut runner and pressed downward by the urging force of a spring. In the above, when the socket is rotated in the reverse direction after detecting that the bolt is inserted into the socket, the amount of downward displacement of the socket within a predetermined time is equal to one pitch of the female screw screwed into the male screw of the bolt. The automatic bolt tightening method is characterized in that the screwing start point is detected by being substantially equal to the following.

According to the automatic bolt tightening method having such a configuration, a position at which the ridges and valleys of the male screw and the female screw match reliably can be detected as a screwing start point. It has an excellent effect that defects such as oblique insertion of bolts and seizure of threads are less likely to occur.

In order to achieve the above object, an invention according to a third aspect of the present invention is directed to an automatic bolt tightening method in which a bolt is automatically tightened by a socket which is rotated by a nut runner and pressed downward by the urging force of a spring. In the above, when the socket is reversely rotated after detecting that the bolt is inserted into the socket, the amount of downward displacement of the socket within a predetermined rotation angle is equal to one of the internal threads of the female screw engaged with the male screw of the bolt. An automatic bolt tightening method characterized in that a screwing start point is detected by being substantially equal to a pitch.

[0013] In the automatic bolt tightening method having such a configuration, the position where the ridges and valleys of the male screw and the female screw are surely matched can be detected as the screwing start point as in the case of the second aspect. In the case of tightening, there is an excellent effect that troubles such as oblique insertion of bolts and seizure of screw threads, which occur most frequently, are unlikely to occur.

According to a fourth aspect of the present invention, there is provided an automatic bolt tightening method in which a bolt is automatically tightened by a socket which is rotated by a nut runner and pressed downward by the urging force of a spring. Wherein the nut runner is rotated forward at a low speed when the amount of downward displacement of the socket within a predetermined time period becomes zero after the nut runner is rotated at a high speed forward and screwed therein. It is a method of attaching.

According to the automatic bolt tightening method having such a configuration, the nut runner is switched from the high-speed normal rotation to the low-speed normal rotation immediately before the bolt is seated, thereby preventing occurrence of a tightening failure such as torque over. It has an excellent effect that it can be performed.

In order to achieve the above object, an invention according to a fifth aspect of the present invention is directed to an automatic bolt tightening method wherein a bolt is automatically tightened by a socket which is rotated by a nut runner and pressed downward by the urging force of a spring. Wherein the nut runner is rotated forward at a low speed when the amount of downward displacement of the socket within a predetermined rotation angle becomes zero after the nut runner is rotated forward at a high speed and screwed into the nut. This is the tightening method.

According to the automatic bolt tightening method having such a structure, the nut runner is switched from the high-speed normal rotation to the low-speed normal rotation immediately before the bolt is seated, as in the case of the fourth aspect, so that the torque is reduced. It has an excellent effect that the occurrence of tightening failure such as over can be prevented.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an automatic bolt tightening device mounted on the robot 100. The automatic bolt tightening device is a bolt tightening unit 1 having a nut runner 103.
01 and a socket 107 disposed below the bolting unit 101. It goes without saying that the present invention is also applicable to a single automatic bolt tightening device.

FIG. 2 shows an essential part of the automatic bolt tightening device and an object to be tightened. Bolt tightening unit 1
Numeral 01 denotes a nut runner 103 rotated and moved up and down by a rotation drive motor (not shown) and a vertical drive motor (not shown), and a drive connected to the lower portion of the nut runner 103 and rotating and moving up and down in conjunction with the nut runner 103. A shaft 105 is provided. A linear sensor 122 that can detect the amount of displacement as the movable part 123 expands and contracts is also attached to the bolting unit 101.

The linear sensor 122 measures a linear displacement, but as a modified example, a rotation angle detector such as a rotary encoder for detecting a rotation angle may be used. When a rotation angle detector is used, it is necessary to convert a linear displacement of the linear portion 114 into a rotational displacement via a gear or the like and detect the rotational displacement.

Below the bolting unit 101, the moving shaft 108 is connected to the driving shaft 105 so that the rotating operation is integral with the driving shaft 105, and the moving shaft 108 can move freely within a certain range. A spring 1 is provided between the drive shaft 105 and the moving shaft 108.
The drive shaft 105 and the moving shaft 108 are pressed by the spring 110 in a direction away from each other. A socket 107 is integrally fitted to a lower portion of the moving shaft 108. A bearing 112 is arranged between the upper outer periphery of the moving shaft 108 and the annular portion 113, and the moving shaft 108 and the annular portion 113 are connected so that the vertical movement is integral and the rotation is free. . A linear portion 114 is connected to the annular portion 113, and the linear portion 114 is connected to the linear sensor 12.
The second movable portion 123 is configured to be in contact with the second movable portion 123.

At the bottom of the socket 107, a bolt 106
Is provided with a socket leg 107a having a hole into which the bolt head 106a can be fitted. Socket 107
The bolt 106 is arranged below the upper part of the female screw 116 of the base 111 of the engine or the like through the workpiece 104.

The lengths before bolt tightening are as follows. The top surface of the bolt head 106a and the workpiece 104
The length between the upper surfaces of the socket legs 107a is L0.
Is L1. Socket leg 107a
Of the bolt head 106a is L2. The axial length of the bolt head 106a is L3, and L1 is set to be somewhat longer than L3.

FIG. 3 illustrates a control mechanism of the automatic bolt tightening device. The control mechanism of the automatic bolt tightening device inputs signals of the linear sensor and the torque sensor to the arithmetic processing unit. The arithmetic processing unit is configured to perform the processing described with reference to FIG. 4 and output to the vertical drive motor and the rotary drive motor. A rotation angle detector may be used instead of the linear sensor.

The flowchart shown in FIG. 4 and FIGS.
The automatic bolt tightening method according to the present invention will be described with reference to FIGS. When the process is started, the sensor displacement amount S, which is the vertical displacement amount detected by the linear sensor 122, is reset in ST1 (abbreviation of Step 1; the same applies hereinafter). The state at this time is shown in FIG. That is, the bolting unit 10
When 1 is at the rising end and the length between the lower surface of the socket leg 107a and the upper surface of the workpiece 104 is L0 + L2, the sensor displacement amount S is reset.

When the process of ST1 is completed, the process proceeds to ST2.
In ST2, the bolt fastening unit 101 is lowered.
The lowering amount of the bolting unit 101 is
L0 + L2, which is the length between the lower surface of the workpiece 07a and the upper surface of the workpiece 104. The bolting unit 101 is L
When it descends about 0 + L2 to the descending end, the linear sensor 1
22 also interlocks and falls about L0 + L2. Therefore, when the lower surface of the socket leg 107a is in contact with the upper surface of the workpiece 104, the displacement S is set to zero,
When the object 7 is separated from the workpiece 104, a value corresponding to the length of the separated object is detected as the displacement amount S. The displacement amount S displayed by the linear sensor 122 has a mode as described in ST3 and ST4 depending on the positional relationship between the socket 107 and the bolt 106 and the like.

When the process of ST2 is completed and the process proceeds to ST3,
In ST3, it is determined whether or not the displacement amount S is equal to L0-L1 at the lower end of the bolting unit 101. If Y, that is, the same amount, the process proceeds to ST8. If N is not the same, the process proceeds to ST4. Displacement S is L0-L
1 means that the socket leg 107a of the socket 107 and the bolt 106 as shown in FIG.
Is just fitted with the bolt head 106a.

When the process of ST3 is completed, the process proceeds to ST4.
In ST4, it is determined whether the displacement amount S is equal to L0 at the lower end of the bolting unit 101. If Y, that is, the same amount, the process proceeds to ST6. If N is not the same, the process proceeds to ST5. The case where the displacement amount S is the same as L0 means that the socket legs 1 as shown in FIG.
07a and the bolt head 106a are pressed by the spring 110 without being fitted. Conversely, the displacement S
Is not the same as L0, as shown in FIG. 5D, because the bolt 106 is out of stock and the socket leg 107a
And the object to be fastened 104 are pressed and contacted by the spring 110.

When the process proceeds to ST5, it becomes NG (defective), so that NG is displayed and the apparatus is stopped.

In ST6, an instruction for reverse rotation of the nut runner is issued. FIG. 6A shows the state when the nutrunner reverse rotation instruction is given. This instruction causes the nut runner 103 to rotate in the reverse direction.

Since the socket 107 is rotated not in the normal direction but in the reverse direction so that the bolt 106 is inserted into the socket 107, it is possible to prevent an inconvenience such as an oblique insertion of the bolt 106 and the like, which may lead to a failure in tightening. It works.

When ST6 ends, the process proceeds to ST7. ST7
Then, it is determined whether or not the displacement amount ΔS within a predetermined time is equal to L1. When the nut runner 103 rotates in the reverse direction, the socket 107 is pressed by the spring 110 and
06a, rotating while sliding on the upper surface, and finally FIG.
Bolt head 1 on the socket leg 107a as indicated by
06a is fitted. At this time, the displacement amount ΔS within a predetermined time is equal to L1. If Y is the same amount in ST7, the process proceeds to ST8, and if N is not the same amount, the process returns to ST6.

According to ST6 and ST7, there is an excellent effect that it is possible to reliably detect that the bolt 106 has entered the socket 107.

When ST7 ends, the process proceeds to ST8. ST8
Then, an instruction for reverse rotation of the nutrunner is issued. FIG. 7A illustrates a state where the nutrunner reverse rotation is instructed. This instruction causes the nut runner 103 to rotate in the reverse direction.

When ST8 ends, the process proceeds to ST9. ST9
Then, it is determined whether or not the displacement amount ΔS within a predetermined time is substantially the same as the length of one pitch of the screw. When the nut runner 103 rotates in the reverse direction, the bolt 106 gradually rises due to the lead angle of the contact surface between the screw thread of the male screw at the lowermost part of the bolt 106 and the female screw at the uppermost part of the workpiece 104, and the screw is just lifted. When it comes to the point where it begins to bite, it drops sharply by the length of one pitch of the screw. FIG. 7B shows a state in which the bolt 106 has dropped by the length of one pitch of the screw. At this time, the displacement amount ΔS within a predetermined time period is substantially equal to the length of one pitch of the screw, which means that the screwing start point has been detected. In ST9, when Y, that is, the displacement amount ΔS within a predetermined time is equal to the length of one pitch of the screw, the process proceeds to ST10. If N, that is, the amount of displacement ΔS within the predetermined time is not substantially the same as the length of one pitch of the screw, the process returns to ST8.

According to ST9, it is possible to detect the position where the male screw and the female screw are securely fitted as the starting point of screwing. Therefore, in the case of automatic bolt tightening, the most common problems are the oblique insertion of the bolt and the screw. It has an excellent effect that a problem such as burning of a mountain hardly occurs.

In ST9, it is determined whether or not the displacement ΔS within a predetermined time is substantially the same as the length of one pitch of the screw. As a modification, a rotation angle detection sensor for measuring the rotation angle of the socket 107 is used. There is also a method of determining whether the amount of displacement ΔS within a predetermined rotation angle output by the mounting and rotation angle detection sensor is substantially equal to the length of one screw pitch.

In the case of this modification as well, the position at which the ridges and valleys of the male screw and the female screw match reliably can be detected as a screwing start point. It has an excellent effect that defects such as burning are less likely to occur.

In ST10, an instruction for high-speed normal rotation is issued. In response to this instruction, the nut runner 103 switches to high-speed forward rotation and starts high-speed screwing.

When ST10 ends, the process proceeds to ST11. S
At T11, it is determined whether the displacement ΔS within a predetermined time is zero. This ST11 detects the position immediately before the bolt 106 is seated. The socket 107 is lowered by one pitch of the screw every rotation during the screwing, but the socket hole depth L1 of the socket leg 107a is made slightly longer than the length L3 of the bolt head. Immediately before the bolt 106 is seated, the socket leg 107 a comes into contact with the workpiece 104. At this time, since the lowering of the socket 107 stops, the displacement amount ΔS within a predetermined time is determined to be zero. FIG. 8 shows a state in which the socket leg 107a is in contact with the workpiece 104.

According to the automatic bolt tightening method having such a configuration, immediately before the bolt 106 is seated, the nut runner 1
Since 03 is switched from high-speed normal rotation to low-speed normal rotation, there is an excellent effect that occurrence of tightening failure such as torque over can be prevented.

If it is determined in ST11 that Y is the displacement amount ΔS within a predetermined time is zero, the process proceeds to ST12, and if N is determined that the displacement amount ΔS within a predetermined time is not zero, the process returns to ST10.

In ST12, the nut runner is instructed to rotate at low speed forward. By this instruction, the nut runner 103
Switches from high-speed forward rotation to low-speed forward rotation, ends screwing, and moves to the tightening step.

The length L1 is set according to the rotation speed at the time of screwing, the response speed of the nut runner 103, and the like.
The screw-in speed is low only for a short time between the difference between L1 and L3, so that the influence on the tightening time is small. This value (difference between L1 and L3) is constant irrespective of the variation in the length of the bolt 106 and the machining accuracy of the bearing surface, so that high-speed and stable fastening can be performed.

In ST11, the displacement ΔS within a predetermined time
Is determined to be zero. As a modification, the socket 1
Attach a rotation angle detection sensor that measures the rotation angle of 07,
Displacement Δ within a predetermined rotation angle output by rotation angle detection sensor
There is also a method of determining whether S is zero or not.

Also in this modification, the nut runner 103 is switched from the high-speed normal rotation to the low-speed normal rotation immediately before the bolt 106 is seated, so that it is possible to prevent occurrence of a tightening failure such as torque over. Has excellent effects.

When ST12 ends, the process proceeds to ST13. S
At T13, it is determined whether the tightening torque has reached a predetermined value. If the predetermined value has been reached, the process proceeds to ST14, and if not, the process returns to ST12.

At ST14, an instruction to remove the socket and raise the bolting unit 101 is issued.

When ST14 ends, the process proceeds to ST15. S
The process ends at T15.

In the flowchart of FIG. 4, when the bolting unit 101 is at the rising end, the sensor displacement S is reset. However, the reset position of the sensor displacement S is a design item that can be appropriately selected. For example, the reset may be performed when the bolting unit 101 is at the lower end. When the reset position is changed in this way, the ST
It is necessary to change the displacement amount S of ST3 and ST4.

[Brief description of the drawings]

FIG. 1 is a perspective view of a robot apparatus to which the present invention is applied.

FIG. 2 is a schematic view of a main part of an automatic bolt tightening device that implements an automatic bolt tightening method according to an embodiment of the present invention.

FIG. 3 is a block diagram of a control mechanism of an automatic bolt tightening device that implements an automatic bolt tightening method according to an embodiment of the present invention.

FIG. 4 shows a flowchart of an automatic bolt tightening method according to an embodiment of the present invention.

FIG. 5 shows an operation state of the automatic bolt tightening device that has performed the automatic bolt tightening method according to the embodiment of the present invention.

FIG. 6 shows an operation state of the automatic bolt tightening device that has performed the automatic bolt tightening method according to the embodiment of the present invention.

FIG. 7 shows an operation state of the automatic bolt tightening device that has performed the automatic bolt tightening method according to the embodiment of the present invention.

FIG. 8 shows an operation state of the automatic bolt tightening device that has performed the automatic bolt tightening method according to the embodiment of the present invention.

FIG. 9 is a schematic view of a conventional automatic bolt tightening device and a control mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Holding plate, 2 ... Drive motor, 3 ... Torque sensor, 4 ... Casing, 4a ... Upper end part, 4aA ... Inner wall, 5 ... Drive shaft, 6 ... Bolt, 7 ... Socket, Reference numeral 8: moving shaft, 9: sliding portion, 10: spring, 11: base, 20: movable sensor, 21: fixed sensor, 22: linear sensor, 24: processing circuit unit, 100: ... Robot, 101 ... Bolt fastening unit, 103 ... Nutrunner, 104 ... Workpiece, 105 ... Drive shaft, 106 ... Bolt, 106a ... Bolt head, 107 ... Socket, 107a ... Socket leg , A moving shaft, 110, a spring, 111, a base, 112, a bearing, 113, an annular portion, 114, a linear portion, 116, a female screw, 122, a linear sensor, 123 ... movable part,

Claims (5)

[Claims] 1. An automatic bolt tightening method in which a bolt is automatically tightened by a socket pressed down by a biasing force of a spring while being rotated by a nut runner. Wherein the socket is displaced downward by approximately the depth of the socket hole when the socket is rotated in the reverse direction, thereby detecting that the bolt has entered the socket. 2. An automatic bolt tightening method in which a bolt is automatically tightened by a socket pressed down by a biasing force of a spring while being rotated by a nut runner, wherein it is detected that the bolt has entered the socket. Thereafter, when the socket is rotated in the reverse direction, the screwing start point is detected by detecting that the amount of downward displacement of the socket within a predetermined time is substantially equal to one pitch of the female screw screwed into the male screw of the bolt. An automatic bolt tightening method characterized in that: 3. An automatic bolt tightening method in which a bolt is automatically tightened by a socket pressed down by a biasing force of a spring while being rotated by a nut runner, wherein it is detected that the bolt has entered the socket. Thereafter, when the socket is rotated in the reverse direction, the screwing start point is detected by detecting that the downward displacement amount of the socket within a predetermined rotation angle is substantially equal to one pitch of the female screw screwed into the male screw of the bolt. Automatic bolt tightening method characterized by the following. 4. An automatic bolt tightening method in which a nut is rotated by a nut runner and the bolt is automatically tightened by a socket pressed downward by the urging force of a spring. An automatic bolt tightening method, wherein the nut runner is rotated at a low speed forward when the amount of downward displacement of the socket within a predetermined time becomes zero. 5. An automatic bolt tightening method wherein a nut is rotated by a nut runner and a bolt is automatically tightened by a socket pressed downward by the urging force of a spring. An automatic bolt tightening method, wherein the nut runner is rotated at a low speed forward when the amount of downward displacement of the socket within a predetermined rotation angle becomes zero.