JP2015058500A - Screw fastening device and screw fastening method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw fastening device and a screw fastening method in which abnormal biting to each other of a male screw and a female screw can be prevented and an operation rate can be improved.SOLUTION: A screw fastening device 1 related to the present invention comprises a motor 11 which generates drive force, a driver bit 18 which is rotated by the drive force of the motor 11, torque detection means 13 which detects rotation torque, and a screw fastening control part 20 which drives the motor 11 and makes the driver bit 18 fasten a screw 2. The screw fastening control part 20 compares the torque detected by the torque detection means 13 with a predetermined torque in a case that the driver bit 18 is fastening the screw 2 to a screw hole 4, and stops the motor 11 in a case that the torque detected by the torque detection means 13 exceeds the predetermined torque.

Description

  The present invention relates to a screw tightening device and a screw tightening method.

  The operation of the conventional screw tightening device is as follows. The screw supply mechanism supplies a male screw. When the adsorption comb is operated, the male screw is adsorbed into the adsorption pipe from below. The conventional screw fastening device moves the adsorbed male screw to a point where it contacts the female screw hole. And the conventional screw fastening apparatus sets the vertical-axis thrust which presses down a male screw. Due to the vertical axis thrust, the conventional screw tightening device lowers the bit shaft to a position where the bit shaft tip and the male screw head, and the male screw tip and the female screw hole come into contact with each other.

  After the bit shaft is lowered to a predetermined position, the conventional screw tightening device stops the rotation by driving the bit shaft reversely by 90 degrees. When the reverse rotation driving is finished, the conventional screw tightening device determines whether or not the fitting state between the bit shaft tip and the cross hole of the male screw is appropriate. The conventional screw tightening device permits screw tightening as it is when the fitting state is appropriate. When the conventional screw fastening device is not properly fitted, the reverse rotation drive of 90 degrees is executed again. The conventional screw tightening device executes an actual screw tightening process after proper fitting between the bit shaft tip and the cross hole of the male screw is completed (see Patent Document 1).

JP-A-7-223130 (for example, paragraphs 0043-0056, FIG. 1 and FIG. 5)

  In the screw tightening operation of the screw tightening device, the male screw or the female screw hole of the workpiece may be damaged. This is because the male screw may be in an abnormal meshing state with the female screw hole. A workpiece that is damaged due to abnormal engagement between the male screw and the female screw hole is a defective product. For this reason, the work needs to be replaced. Since it takes time to replace the workpiece, the operating rate of the screw tightening device decreases. Therefore, in order to increase the operating rate, the screw tightening device needs to prevent the male screw and the female screw hole from being in an abnormal meshing state in the screw tightening operation.

  The screw tightening device described in Patent Literature 1 determines whether or not the tip of the bit shaft is properly fitted to the screw head of the male screw based on the axial movement direction position data after the reverse rotation drive. Further, whether or not the tip of the bit shaft is properly fitted to the screw head of the male screw is determined based on the data of the axial movement direction position of the tip of the bit shaft. However, it is difficult to correctly determine the fitting state based on the data of the axial movement direction position of the tip of the bit shaft corresponding to the screw having a large variation in the total screw length. For this reason, the screw fastening apparatus described in Patent Document 1 cannot prevent the male screw and the female screw hole from being in an abnormal meshing state in the screw fastening operation. Therefore, the screw tightening device described in Patent Document 1 has a problem that a screw tightening failure occurs and the operating rate is reduced.

  An object of the present invention is to provide a screw tightening device and a screw tightening method that can prevent the male screw and the female screw hole from being in an abnormal meshing state and improve the operating rate.

  The screw tightening device according to the present invention includes a motor that generates a driving force, a driver bit that is rotated by the driving force of the motor, a torque detection unit that detects rotational torque, and a motor that is driven to tighten the screw on the driver bit. And a screw tightening control unit that compares the torque detected by the torque detecting means with a predetermined torque when the driver bit is tightening the screw into the screw hole, and the torque detecting means The motor is stopped when the detected torque exceeds a predetermined torque.

  The screw tightening method according to the present invention includes a screw supply step in which the tip of a driver bit that is rotated by driving a motor is fitted to the screw head of the male screw, the driver bit is lowered, and the driver bit is rotated to tighten the male screw into the screw hole A screw tightening operation for detecting rotation torque, comparing the detected torque with a predetermined torque, and a screwing step for stopping the motor when the detected torque exceeds the predetermined torque. Prepare.

  INDUSTRIAL APPLICABILITY The present invention can provide a screw tightening device and a screw tightening method capable of improving the operating rate in order to prevent the male screw and the female screw hole from being in an abnormal meshing state.

It is the schematic which shows the structure of the screw fastening apparatus which concerns on Embodiment 1. FIG. It is a figure which shows an example of the data set as a parameter in each process of the screw fastening which concerns on Embodiment 1. FIG. It is a figure which shows the change condition of the speed and torque in each process of the screw fastening which concerns on Embodiment 1. FIG. It is a figure which shows the flowchart of the screw fastening method which concerns on Embodiment 1. FIG. It is a figure which shows the judgment criteria of the appropriateness | suitability / inappropriateness of the screw adsorption state which concerns on Embodiment 1. It is a figure shown about the fitting state of the external thread and internal thread hole which concerns on Embodiment 1. FIG. It is a figure shown about the fitting state of the front-end | tip of the driver bit which concerns on Embodiment 1, and the screw head of a male screw. It is a figure which shows the screw-tightening state which concerns on Embodiment 1. FIG. 3 is a diagram illustrating a simplified screw according to Embodiment 1. FIG. It is a figure which shows the meshing state of the screw which concerns on Embodiment 1. FIG.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram illustrating a configuration of a screw fastening device 1 according to the first embodiment. With reference to FIG. 1, the structure of the screw fastening apparatus 1 is demonstrated. As shown in FIG. 1, the screw tightening device 1 includes a screw tightening mechanism unit 10 and a screw tightening control unit 20.

  The screw tightening mechanism 10 includes a servo motor 11, an output shaft 111, an encoder 12, a torque converter 13, a torque converter housing 131, a support body 14, an upper arm 141a, a lower arm 141b, a bearing 142a, a bearing 142b, and a cup. The ring 15, the shaft 16 a, the shaft 16 b, the universal joint 17, the driver bit 18, the electromagnetic coil 19, and the robot 30 are configured.

  The servo motor 11 has an output shaft 111. The servo motor 11 is an electric motor. The servo motor 11 is provided with an encoder 12 that detects the rotational position of the output shaft 111. The servo motor 11 and the encoder 12 are connected to each other.

  A torque converter housing 131 that is a housing of the torque converter 13 is connected to the servo motor 11. The lower part of the torque converter housing 131 is connected to the support 14. The support body 14 has a U-shape as shown in FIG. The support 14 is supported in the vertical direction by a robot 30 that can move in the horizontal and vertical directions.

  The output shaft 111 is connected to the shaft 16 a via the coupling 15. Further, the shaft 16 a and the shaft 16 b are connected by a universal joint 17. The universal joint 17 is configured to transmit the rotational force of the shaft 16a to the shaft 16b even when the axis of the shaft 16a and the axis of the shaft 16b do not coincide with each other.

  The support 14 is provided with a bearing 142a in the upper arm 141a. The bearing 142a has an annular shape that covers the periphery of the shaft 16a. The bearing 142a supports the shaft 16a from the radial direction. The radial direction is a direction perpendicular to the axis of the shaft 16a. As a result, the shaft 16 a can rotate in the horizontal direction with respect to the support 14.

  The support 14 is provided with a bearing 142b in the lower arm 141b. The bearing 142b has an annular shape that covers the periphery of the shaft 16b. The bearing 142b supports the shaft 16b from the radial direction. The radial direction is a direction perpendicular to the axis of the shaft 16b. As a result, the shaft 16 b can rotate in the horizontal direction with respect to the support 14.

  A driver bit 18 is connected to the lower end of the shaft 16b. The driver bit 18 is held by the shaft 16b. A hole is provided in the screw head of the male screw 2 used for screw tightening. For this reason, the driver bit 18 has a tip shape that matches the shape of the hole. If the shape of the screw head hole of the male screw 2 is a cross, the driver bit 18 having a cross at the tip is used. If the shape of the screw head hole of the male screw 2 is one character, the driver bit 18 having a single tip shape is used.

  An electromagnetic coil 19 is attached to the lower arm 141 b of the support 14. The electromagnetic coil 19 covers the driver bit 18. The electromagnetic coil 19 is connected to a power source (not shown). The electromagnetic coil 19 magnetizes the driver bit 18 when current is supplied from the power source.

  The driver bit 18 is connected to the output shaft 111 via the coupling 15, the shaft 16a, the universal joint 17, and the shaft 16b. When the output shaft 111 rotates by driving the servo motor 11, the driver bit 18 rotates together with the output shaft 111.

  The rotating shaft of the screw tightening mechanism unit 10 includes an output shaft 111, a coupling 15, a shaft 16a, a universal joint 17, a shaft 16b, and a driver bit 18. The torque converter 13 is a sensor that converts a torsion amount corresponding to the rotational torque of the rotating shaft into an electric amount. The torque converter 13 uses, for example, a strain gauge as a sensor. Note that the amount of twist according to the rotational torque refers to surface shear stress.

  The rotational torque of the driver bit 18 is the same as the rotational torque of the rotational shaft of the screw tightening mechanism unit 10. For this reason, the rotational torque of the driver bit 18 can be detected by detecting the rotational torque of the rotational shaft of the screw tightening mechanism unit 10.

  The screw tightening control unit 20 includes a sequencer 21, a servo controller 22, and a robot controller 23. The torque converter 13 outputs the detected rotational torque of the driver bit 18 to the sequencer 21. The sequencer 21 takes in the rotational torque of the driver bit 18 from the torque converter 13 and uses it for screw tightening control.

  In the robot controller 23, position data of the robot 30 is set in advance. In response to a command from the sequencer 21, the robot controller 23 moves the robot 30 based on preset position data. As a result, the robot controller 23 controls the position of the screw tightening mechanism unit 10.

  The sequencer 21 outputs a command for driving the servo motor 11 to the servo controller 22. The command for driving the servo motor 11 is a command such as a rotation direction, a rotation speed, a rotation start acceleration / deceleration time, a rotation time, and a rotation end acceleration / deceleration time. The servo controller 22 drives the servo motor 11 based on commands from the sequencer 21 such as the rotation direction, rotation speed, rotation start acceleration / deceleration time, rotation time, and rotation end acceleration / deceleration time. The rotation start acceleration / deceleration time is a time required for the rotation speed to reach a predetermined rotation speed from zero. The rotation time is the time for which the rotation is continued at a predetermined rotation speed. The rotation end acceleration / deceleration time is a time required for the rotation speed to become 0 from a predetermined rotation speed.

  Next, operation | movement of the screw fastening apparatus 1 which concerns on Embodiment 1 is demonstrated. The details of the screw tightening method using the screw tightening device 1 will be described later. As shown in FIG. 1, the screw tightening device 1 of the first embodiment performs screw tightening of the male screw 2 on the female screw hole 4 of the workpiece 3. The tightening of the male screw 2 with respect to the female screw hole 4 of the workpiece 3 is hereinafter referred to as a screw tightening operation.

  Before starting the screw tightening operation, the screw tightening device 1 fits the tip of the driver bit 18 into the hole of the screw head of the male screw 2. In this state, the screw fastening device 1 supplies a current from the power source to the electromagnetic coil 19 to magnetize the driver bit 18. The magnetized driver bit 18 attracts the male screw 2.

  Then, the robot controller 23 controls the horizontal position of the screw tightening mechanism unit 10. The robot controller 23 moves the screw tightening mechanism 10 above the female screw hole 4 of the workpiece 3 by controlling the robot 30. Further, the robot controller 23 controls the vertical position of the screw tightening mechanism unit 10. The robot controller 23 controls the robot 30 to lower the driver bit 18 and bring the male screw 2 attracted to the tip of the driver bit 18 into contact with the female screw hole 4. The robot 30 is in a state where the male screw 2 is pressed against the female screw hole 4 with a constant thrust.

  The sequencer 21 transmits commands such as a rotation direction, a rotation speed, a rotation start acceleration / deceleration time, a rotation time, and a rotation end acceleration / deceleration time to the servo controller 22 as a parameter set. The servo controller 22 drives the servo motor 11 based on this command.

  The servo motor 11 rotates according to a command from the servo controller 22. The rotating shaft of the screw tightening mechanism unit 10 rotates as the output shaft 111 of the servo motor 11 rotates. Thereby, the male screw 2 adsorbed on the tip of the driver bit 18 rotates.

  The sequencer 21 always takes in the rotational torque of the driver bit 18 from the torque converter 13. The sequencer 21 changes the parameter set according to the rotational torque of the driver bit 18 and the rotation time in the parameter set. The sequencer 21 transmits the rotation direction, rotation speed, rotation start acceleration / deceleration time, rotation time, rotation end acceleration / deceleration time, and the like of the changed parameter set to the servo controller 22 as commands. The servo controller 22 drives the servo motor 11 based on this command. Then, the torque converter 13 detects the rotational torque of the driven driver bit 18 and outputs it to the sequencer 21.

  The screw tightening control unit 20 repeatedly executes such control to rotate the rotating shaft of the screw tightening mechanism unit 10. Thereby, the male screw 2 adsorbed on the tip of the driver bit 18 rotates. In this way, the screw fastening device 1 can fasten the male screw 2 in the female screw hole 4 of the workpiece 3. The sequencer 21 automatically changes the parameter set as appropriate. Thereby, the screw fastening apparatus 1 which concerns on Embodiment 1 can implement the screw fastening of arbitrary sequences.

  The screw tightening control unit 20 rotates the driver bit 18 when the sequencer 21 and the servo controller 22 command the servo motor 11 to be driven. The screw tightening control unit 20 stops the driver bit 18 when the sequencer 21 and the servo controller 22 command the servo motor 11 to stop.

  In the screw tightening control unit 20, the sequencer 21 inputs the rotational torque of the driver bit 18 from the torque converter 13. The sequencer 21 inputs information on the rotational position of the output shaft 111 from the encoder 12. The sequencer 21 makes a determination using these pieces of information. In this way, the screw tightening control unit 20 controls the screw tightening operation.

  Next, the screw tightening failure in the screw tightening operation will be described. One example of screw tightening failure is screwing. For example, the male screw 2 may collide with the outer end portion of the female screw hole 4 of the work 3 in a state where the male screw 2 is overturned or inclined. In this case, the male screw 2 may break the female screw hole 4 and be in an abnormal meshing state with the female screw hole 4. Hereinafter, the fact that the male screw 2 breaks the female screw hole 4 and is in an abnormal meshing state with the female screw hole 4 is referred to as screw galling. When screwing occurs, the workpiece 3 is scratched or destroyed.

  When screwing occurs during screw tightening, the workpiece 3 needs to be replaced. The screw tightening device 1 performs the screw tightening again after exchanging the workpiece 3. For this reason, in the case of screw tightening failure due to screwing, the screw tightening device 1 takes time to recover. Therefore, the operating rate of the screw fastening device 1 is greatly reduced.

  That is, in order to improve the operating rate, the screw tightening device 1 is required not to cause screwing. For this purpose, it is necessary to quickly detect the sign of screwing and to stop the rotation of the driver bit 18 so as not to advance the screwing.

  Next, a screw tightening method using the screw tightening device 1 according to the first embodiment will be described. In the screw tightening method according to the first embodiment, each screw tightening process includes a screw supply process, a blending process, a screwing process, a temporary tightening process, a final tightening process, and a retry process. In addition, about the screw fastening method which concerns on Embodiment 1, the detailed procedure in each process is mentioned later.

  FIG. 2 is a diagram illustrating an example of data set as a parameter in the sequencer 21 in each screw tightening process according to the first embodiment. The screw tightening device 1 according to the first embodiment registers various data as parameters for each screw tightening condition. FIG. 2 shows an example of the A model and the B model corresponding to each screw tightening condition.

  In addition, normal rotation is rotation of the direction which tightens a screw. The reverse rotation is rotation that is opposite to the direction in which the screw is tightened. In FIG. 2, positive values of speed and torque indicate the forward direction. Negative values of speed and torque indicate the reverse direction.

  The conforming speed −V1, the screwing speed V2, the temporary tightening speed V3, the final tightening speed V4, and the retry reverse speed −V5 correspond to the rotational speed in the parameter set used by the screw tightening control unit 20 described above. The blending time t1 and the screwing time t2 correspond to the rotation time in the parameter set used by the screw tightening control unit 20 described above. Further, the forward rotation direction or the reverse rotation direction in each process corresponds to the rotation direction in the parameter set used by the screw tightening control unit 20 described above.

  FIG. 3 is a diagram illustrating changes in speed and torque in each step in the screw tightening method according to the first embodiment. As shown in FIG. 3, each step of the screw tightening method according to the first embodiment is in the order of a blending step, a screwing step, a temporary tightening step, and a final tightening step. Although not shown in FIG. 3, there may be a retry process and a screwing process between the screwing process and the temporary tightening process.

  Of the parameter set used by the screw tightening control unit 20 described above, the rotation start acceleration / deceleration time is the time until the rotation speed increases to the acclimation speed −V1 after the driver bit 18 starts rotating in the acclimation process. It's about time. The rotation start acceleration / deceleration time is a time until the rotation speed increases to the screwing speed V2 after the driver bit 18 starts rotating in the screwing process. The rotation start acceleration / deceleration time is the time from when the driver bit 18 starts to rotate until the rotation speed increases to the temporary tightening speed V3 in the temporary tightening process. The rotation start acceleration / deceleration time is a time until the rotation speed increases to the final fastening speed V4 after the driver bit 18 starts rotating in the final fastening process.

  Further, the rotation end acceleration / deceleration time is a time required for the rotation speed to become zero from the acclimation speed −V1 when the driver bit 18 is stopped in the acclimation process. The rotation end acceleration / deceleration time is the time until the rotational speed becomes 0 from the screwing speed V2 when the driver bit 18 is stopped in the screwing process. The rotation end acceleration / deceleration time is a time until the rotation speed becomes 0 from the temporary fastening speed V3 when the driver bit 18 is stopped in the temporary fastening process. The rotation end acceleration / deceleration time is a time until the rotational speed becomes 0 from the final fastening speed V4 when the driver bit 18 is stopped in the final fastening process.

  FIG. 4 is a flowchart of the screw tightening method according to the first embodiment. A screw tightening method according to the first embodiment will be described with reference to FIGS.

(1) Screw supply process In FIG. 4, the screw supply process is a process of supplying the male screw 2 used for screw tightening. The male screw 2 is mounted on a screw supply plate (not shown). The male screw 2 is arranged on the screw supply plate so that the screw head faces upward.

  In the screw supply process, the screw tightening control unit 20 moves the screw tightening mechanism unit 10 above the screw supply plate. Thereafter, the screw tightening control unit 20 lowers the screw tightening mechanism unit 10 toward the male screw 2. The screw tightening control unit 20 fits the tip of the driver bit 18 into the screw head hole of the male screw 2. As a result, the screw tightening device 1 fits the tip of the driver bit 18 to the screw head of the male screw 2.

  Then, the screw tightening control unit 20 controls the current to flow through the electromagnetic coil 19. The electromagnetic coil 19 magnetizes the driver bit 18. Thereby, the screw fastening apparatus 1 adsorb | sucks the external thread 2 to the front-end | tip of the driver bit 18 (S1).

  Next, as shown in FIG. 1, the screw tightening control unit 20 moves the screw tightening mechanism unit 10 above the female screw hole 4 of the workpiece 3. Then, in the screw supply step of FIG. 4, the screw tightening control unit 20 confirms the suction state of the male screw 2 (S2). FIG. 5 is a diagram illustrating criteria for determining whether the screw adsorption state is appropriate or not according to the first embodiment. With reference to FIG. 5, the determination of the suction state of the male screw 2 will be described.

  In FIG. 5, SenA, SenB, and SenC represent the positions of the optical axes of the photoelectric sensor 40a, the photoelectric sensor 40b, and the photoelectric sensor 40c, respectively. As shown in FIG. 5, the photoelectric sensor 40 a detects whether light is transmitted or shaded on the right side of the threaded portion of the male screw 2. As shown in FIG. 5, the photoelectric sensor 40 b detects whether the left side of the thread portion of the male screw 2 is transmitted or shielded. As shown in FIG. 5, the photoelectric sensor 40 c detects whether the lower side of the threaded portion of the male screw 2 is transmitted or blocked.

  The transmission of the optical axis of the photoelectric sensor 40a, the photoelectric sensor 40b, and the photoelectric sensor 40c means that there is no thread portion of the male screw 2 at that position. That the optical axes of the photoelectric sensor 40a, the photoelectric sensor 40b, and the photoelectric sensor 40c are shielded from light means that the threaded portion of the male screw 2 exists at that position.

  The sequencer 21 takes in information on whether the optical axis is transmitted or blocked from the photoelectric sensor 40a, the photoelectric sensor 40b, and the photoelectric sensor 40c. In FIG. 5A, the photoelectric sensor 40a, the photoelectric sensor 40b, and the photoelectric sensor 40c are transmissive. As shown in FIG. 5A, when all of the photoelectric sensor 40a, the photoelectric sensor 40b, and the photoelectric sensor 40c are transmissive, the sequencer 21 determines that the screw adsorption state is appropriate.

  In FIG. 5B, the photoelectric sensor 40a and the photoelectric sensor 40c are transmissive. In FIG. 5- (b), the photoelectric sensor 40b is light-shielded. As shown in FIG. 5B, when any one of the photoelectric sensor 40a, the photoelectric sensor 40b, and the photoelectric sensor 40c shields light, the sequencer 21 determines that the screw adsorption state is not appropriate.

  In FIG. 5C, the photoelectric sensor 40a and the photoelectric sensor 40b are transmissive. In FIG. 5- (c), the photoelectric sensor 40c is light-shielded. As shown in FIG. 5C, when any one of the photoelectric sensor 40a, the photoelectric sensor 40b, and the photoelectric sensor 40c shields light, the sequencer 21 determines that the screw adsorption state is not appropriate. The screw adsorption state detecting means of the present invention is the photoelectric sensor 40a, the photoelectric sensor 40b, and the photoelectric sensor 40c.

  In FIG. 4, when the screw adsorption state is not appropriate, the screw tightening control unit 20 determines that the screw loading abnormality has ended (S3). The abnormal end of screw loading means that the suction state of the male screw 2 is not appropriate, so the flow of the screw tightening method is stopped halfway, and the screw tightening is not completed normally and is terminated abnormally.

  In step S <b> 2, when the screw suction state is appropriate, the screw tightening control unit 20 lowers the driver bit 18 into the female screw hole 4 of the work 3. The screw tightening control unit 20 controls the position of the screw tightening mechanism unit 10 in the vertical direction so that the male screw 2 is pressed against the female screw hole 4 of the work 3 with a constant thrust (S4). Thereby, the screw fastening apparatus 1 makes the male screw 2 and the female screw hole 4 of the workpiece | work 3 contact. After step S4, the screw tightening device 1 starts screw tightening (S5). In addition, the above is description about Claim 4 and Claim 10.

(2) Blending process In FIGS. 3 and 4, the blending process is a process for easily fitting the male screw 2 into the female screw hole 4 of the workpiece 3.

  4, the screw tightening control unit 20 reverses the driver bit 18 at a low speed as shown in FIG. 3 (S6). The rotational speed at this time is a blending speed −V1 shown in FIG. In the blending step of FIG. 4, the screw tightening control unit 20 rotates the male screw 2 reversely by about 360 degrees while bringing the male screw 2 and the female screw hole 4 of the workpiece 3 into contact with each other. At this time, the tip of the driver bit 18 is fitted to the screw head of the male screw 2.

  FIG. 6 is a diagram illustrating a fitting state between the male screw 2 and the female screw hole 4 of the workpiece 3. At the start of the blending process, as shown in FIG. 6A, the screw tightening device 1 may not properly fit the male screw 2 and the female screw hole 4 of the workpiece 3. In this case, the screw tightening control unit 20 reverses the male screw 2 while bringing the male screw 2 and the female screw hole 4 of the workpiece 3 into contact with each other in step S6. Accordingly, the screw tightening control unit 20 can appropriately fit the male screw 2 and the female screw hole 4 of the workpiece 3 as shown in FIG. Therefore, the screw tightening device 1 can suppress the occurrence of screwing.

  In step S2, it is assumed that the screw suction state is determined to be appropriate. However, the tip of the driver bit 18 and the screw head of the male screw 2 may not actually be completely fitted. FIG. 7 is a diagram illustrating a fitting state between the tip of the driver bit 18 and the screw head of the male screw 2. At the start of the blending process, as shown in FIG. 7- (a), the screw tightening device 1 may not completely fit the tip of the driver bit 18 and the screw head of the male screw 2. Even in such a case, the screw tightening control unit 20 drives the driver bit 18 in the reverse direction while bringing the tip of the driver bit 18 into contact with the screw head of the male screw 2 in step S6. As a result, the screw tightening control unit 20 can appropriately fit the tip of the driver bit 18 and the screw head of the male screw 2 as shown in FIG. Therefore, the screw tightening device 1 can suppress the occurrence of screwing.

  In the blending step of FIG. 4, the screw tightening control unit 20 checks whether the rotational torque of the driver bit 18 exceeds a predetermined torque (S7). This predetermined torque is the familiarization monitoring torque -T1 shown in FIG. In step S7 of FIG. 4, when the conforming monitoring torque −T1 is exceeded, the screw tightening control unit 20 terminates screw tightening abnormally (S8). If it is determined in step S7 that the running-in monitoring torque −T1 has not been exceeded, the screw tightening control unit 20 checks whether or not a predetermined time has elapsed after starting rotation at the running-in speed −V1 in step S6 (S9). This predetermined time is the habituation time t1 shown in FIG. Note that the case where the conforming monitoring torque −T1 is exceeded means that the rotational torque of the driver bit 18 is less than the conforming monitoring torque −T1.

  In step S9 of FIG. 4, when the habituation time t1 has not elapsed, the process returns to step S6. In step S9, when the familiarizing time t1 has elapsed, the screw tightening control unit 20 stops the driver bit 18 as shown in FIGS. 3 and 4 (S10). And it transfers to the screwing process which is the next process. In addition, the above is description about Claim 6 and Claim 12.

(3) Screwing process In FIGS. 3 and 4, the screwing process is a process of detecting a sign of screw galling that occurs in the initial stage of screw tightening.

  In the screwing process of FIG. 4, the screw tightening control unit 20 causes the driver bit 18 to rotate normally at a low speed as shown in FIG. 3 (S11). The rotational speed at this time is the screwing speed V2 shown in FIG. In the screwing process of FIG. 4, the screw tightening control unit 20 checks whether the rotational torque of the driver bit 18 exceeds a predetermined torque (S12). This predetermined torque is the screwing monitoring torque T2 shown in FIG.

  Here, detection of screwing will be described. In the screwing process, it is necessary to quickly detect a sign of screwing so as not to generate screwing. A sign of screwing is detected when the rotational torque of the driver bit 18 exceeds the screwing monitoring torque T2 set in the screwing process.

  As a method of detecting the rotational torque of the driver bit 18, there is a method of using the current value of the servo motor 11. Further, as a method for detecting the rotational torque of the driver bit 18, there is a method in which the torque converter 13 is incorporated in the rotating shaft of the screw tightening mechanism 10 and a voltage value output from the torque converter 13 is used. Either method can be used for the torque detection means.

  Here, the screw tightening control requires quick response when detecting the rotational torque. Responsiveness means that a change in rotational torque can be detected immediately. However, the method using the current value of the servo motor 11 is inferior to the method using the torque converter 13 in terms of quick response. Further, the method using the current value of the servo motor 11 may cause an error due to temperature. For this reason, in the first embodiment, the torque detector uses the torque converter 13.

  Further, the screw tightening control unit 20 controls the rotation shaft of the screw tightening mechanism unit 10 by using the rotational torque of the driver bit 18 detected by the torque converter 13. For this reason, the screw tightening device 1 according to the first embodiment can immediately respond to this change after immediately detecting a change in rotational torque in the screw tightening control. This is the explanation for claims 5 and 11.

  In step S12 of FIG. 4, when the rotational torque of the driver bit 18 exceeds the screwing monitoring torque T2, the screw tightening control unit 20 stops the driver bit 18 suddenly (S13).

  Here, when a sign of screwing is detected, the screw tightening control unit 20 instructs the servo motor 11 to stop suddenly. If a sudden stop command is received, the servo motor 11 stops rotating. As a result, the driver bit 18 stops rotating.

  Hereinafter, the angle at which the driver bit 18 rotates after the sign of screwing is actually stopped is referred to as a sudden stop rotation angle. The rotation angle at the time of sudden stop may differ depending on the size, material, fastening application, etc. of the male screw 2 and the female screw hole 4 and the maximum rotation angle that does not cause screwing.

  Further, the screw tightening device 1 takes time until the driver bit 18 actually stops after the screw tightening control unit 20 commands a sudden stop. For this reason, even if the sign of screwing is detected, the screw tightening device 1 may cause screwing before the driver bit 18 actually stops.

  The time required for the driver bit 18 to become 0 from the maximum rotational speed after the screw tightening control unit 20 commands a sudden stop is hereinafter referred to as a sudden stop time. Further, at the time of a sudden stop, the vehicle stops at an acceleration obtained by dividing the maximum speed by the sudden stop time. The sudden stop time should be as short as possible so as not to cause screwing. In addition, the sudden stop time needs to be as short as possible so that the screwing does not proceed when the screwing occurs.

  However, when the sudden stop time is extremely short, a large inertia force is generated in the screw tightening mechanism portion 10. This inertial force has an adverse effect on the mechanical system of the screw tightening mechanism unit 10 including the torque converter 13. For this reason, it is necessary to set the sudden stop time according to the mechanical system of the screw tightening mechanism unit 10.

  That is, the sudden stop time is determined according to the mechanical system of the screw tightening mechanism unit 10. Therefore, the rotation angle at the time of sudden stop can be adjusted by changing the screwing speed V2. In other words, when the driver bit 18 is suddenly stopped, the screwing speed V2 is determined so that the rotation angle at the time of sudden stop is equal to or less than an allowable rotation angle.

  The screw tightening control unit 20 needs to detect a sign of screw galling under any screw tightening condition and to stop the driver bit 18 suddenly when screwing various workpieces. Accordingly, it is necessary to change the screwing speed V2 to various speeds.

  With the screwing speed V2 determined in this way, the screw tightening control unit 20 rotates the driver bit 18 in step S11 of the screwing process. In step S12, when the rotational torque of the driver bit 18 exceeds the screwing monitoring torque T2, the screw tightening control unit 20 stops the driver bit 18 suddenly. At this time, the screw tightening control unit 20 suddenly stops the driver bit 18 so that the rotation angle at the time of sudden stop is equal to or less than an allowable rotation angle. The screw tightening control unit 20 transmits a command to the servo motor 11 so that the driver bit 18 performs such an operation.

  For the A type screw (M3.5 screw, material S12C) in FIG. 2, the allowable rotation angle is 7 degrees, and the time taken to actually stop after commanding a sudden stop is 0. The screwing speed was 200 rpm for 5 msec.

  In step S12 of FIG. 4, if the rotational torque of the driver bit 18 does not exceed the screwing monitoring torque T2, has the screw tightening control unit 20 passed a predetermined time after starting the rotation at the screwing speed V2 in step S11? Confirm (S14). This predetermined time is the screwing time t2 shown in FIG. In step S14 of FIG. 4, if the screwing time t2 has not elapsed, the process returns to step S11. In this way, the screw tightening control unit 20 constantly monitors whether the rotational torque of the driver bit 18 exceeds the screwing monitoring torque T2.

  In step S14, when the screwing time t2 has elapsed, the screw tightening control unit 20 stops the driver bit 18 suddenly as shown in FIGS. 3 and 4 (S15). And it transfers to the temporary fastening process which is the next process. In addition, the above is description about Claim 1, Claim 2, Claim 7, and Claim 8.

(4) Temporary fastening process In FIGS. 3 and 4, the temporary fastening process is a process of efficiently screwing the male screw 2 into the female screw hole 4.

  In the temporary tightening step of FIG. 4, the screw tightening control unit 20 causes the driver bit 18 to rotate forward at high speed as shown in FIG. 3 (S16). The rotational speed at this time is a temporary fastening speed V3 shown in FIG. In the temporary tightening process of FIG. 4, the screw tightening control unit 20 confirms whether the rotational torque of the driver bit 18 exceeds a predetermined torque (S17). This predetermined torque is the temporary fastening end torque T3 shown in FIG.

  In step S17 of FIG. 4, when the temporary tightening end torque T3 is not exceeded, the screw tightening control unit 20 returns to step S16. If the temporary tightening end torque T3 is exceeded in step S17, the screw tightening control unit 20 stops the driver bit 18 suddenly as shown in FIGS. 3 and 4 (S18). And it transfers to the final fastening process which is the next process.

(5) Final tightening process In FIGS. 3 and 4, the final tightening process is a process of finally tightening the male screw 2 into the female screw hole 4.

  In the final tightening step of FIG. 4, the screw tightening control unit 20 causes the driver bit 18 to rotate normally at a low speed as shown in FIG. 3 (S19). The rotational speed at this time is a final fastening speed V4 shown in FIG. In the final tightening step of FIG. 4, the screw tightening control unit 20 confirms whether the rotational torque of the driver bit 18 exceeds a predetermined torque (S20). This predetermined torque is the final tightening end torque T4 shown in FIG.

  In step S20 of FIG. 4, when the final tightening torque T4 is not exceeded, the screw tightening control unit 20 returns to step S19. If the final tightening torque T4 is exceeded in step S20, the screw tightening control unit 20 suddenly stops the driver bit 18 as shown in FIGS. 3 and 4 (S21). Then, the screw tightening control unit 20 ends the screw tightening operation (S22).

  In step S22 of the final tightening step of FIG. 4, the screw tightening method according to the first embodiment ends the screw tightening by ending the screw tightening operation (S23).

(6) Retry Process In FIG. 4, the retry process is a processing process when the screwing monitoring torque T2 is exceeded in the screwing process.

  In the retry process of FIG. 4, the screw tightening control unit 20 checks whether or not the number of times of performing the retry operation is equal to or less than the number of possible retry operations (S24). In step S24, if the number of retry operations exceeds the number of possible retry operations, the screw tightening is abnormally terminated (S25).

  For example, when screwing has progressed, the number of times that the screw tightening device 1 has performed the retry operation exceeds the number of possible retry operations. In addition, when the shape of the screw thread is not appropriate, the number of times that the screw tightening device 1 has performed the retry operation exceeds the number of possible retry operations. In addition, when foreign matter is attached, the number of times that the screw tightening device 1 has performed the retry operation exceeds the number of possible retry operations.

  In consideration of such a case, in the retry process, a limit is set on the number of times the driver bit 18 is reversed by the retry operation. If the number of retries exceeds the limit, the male screw 2 used for screw tightening at this time has a poor quality. The number of possible retries is determined according to the size, material, fastening application, and the like of the male screw 2 and the female screw hole 4 of the work 3 to be used. The number of possible retries is determined to be 3 times, for example.

  In step S24 of FIG. 4, when the number of retry operations is equal to or less than the number of possible retry operations, the screw tightening control unit 20 causes the driver bit 18 to perform a retry operation. In the retry operation, the screw tightening control unit 20 reverses the driver bit 18 at a low speed (S26). The rotational speed at this time is the retry reverse speed −V5 shown in FIG.

  In step S26 of FIG. 4, the screw tightening control unit 20 loosens the male screw 2 more than the amount by which the male screw 2 and the female screw hole 4 are engaged. Thereby, the male screw 2 is completely loosened from the female screw hole 4, and the screw tightening start position is changed.

  In FIG. 4, the screw tightening control unit 20 confirms whether or not the driver bit 18 is reversed by a predetermined rotation amount after the retry operation is started in step S26 (S27). The predetermined rotation amount is the retry reverse rotation amount −R5 shown in FIG.

  If the retry reverse rotation amount −R5 is not reversed at step S27 in FIG. 4, the process returns to step S26. If the retry reverse rotation amount -R5 is reversed in step S27, the screw tightening control unit 20 stops the driver bit 18 (S28). In this case, since the screw tightening start position has been changed, the process returns to the screwing process. After returning to the screwing step, the screw tightening device 1 starts the screw tightening operation again from step S11.

  It is known that screw squeezing frequently occurs immediately after the start of screw tightening in the screwing process. For this reason, the retry process is often performed after detecting a sign of screwing immediately after the start of screw tightening. Here, consider a case where the amount of rotation for loosening the male screw 2 is a multiple of 360 degrees. In this case, the positional relationship between the male screw 2 and the female screw hole 4 after loosening is shifted from several degrees to several tens of degrees with respect to the positional relation before loosening. That is, if the amount of rotation to be loosened is a multiple of 360 degrees, the screw tightening start position is hardly changed after the driver bit 18 is reversed by the retry operation.

  For this reason, the rotation amount for loosening the male screw 2 is a multiple of 360 degrees + 180 degrees. Thereby, the screw tightening start position can be changed through the reverse rotation of the driver bit 18 by the retry operation. In addition, the above is description about Claim 3 and Claim 9.

Next, a situation in which screwing is likely to occur will be described. The following (a) to (d) are known as situations where screwing is likely to occur.
(B) The shape of the thread of the male screw 2 or the female screw hole 4 is not appropriate.
(B) Foreign matter adheres to the tip of the male screw 2, the female screw hole 4, or the driver bit 18.
(C) At the start of screw tightening, the fitting state between the tip of the driver bit 18 and the screw head of the male screw 2 is not appropriate at the position where the male screw 2 and the female screw hole 4 are in contact. Or in the same conditions, the fitting state of the external thread 2 and the internal thread hole 4 is not appropriate. (The posture of the male screw 2 is not vertical.)
(D) In the screw tightening state, the rotational speed of the driver bit 18 immediately after the start of screw tightening is high. FIG. 8 shows the screw tightening state according to the first embodiment. The screw tightened state is a state after the male screw 2 is fitted into the female screw hole 4 and the male screw 2 is rotated forward as shown in FIG. In the screwed state, the male screw 2 is screwed into the female screw hole 4.

Furthermore, in the experiment, it was found that the following (e) and (f) are likely to cause screw galling.
(E) The screw tightening start position is not appropriate. The screw tightening start position is the position of the male screw 2 with respect to the female screw hole 4 at the time when the screwing process is started. The screw tightening start position starts from a position where the male screw 2 and the female screw hole 4 start to engage with each other. Here, the male screw 2 and the female screw hole 4 start to engage with each other when the thread cutting start portion and the valley cutting start portion are caught. Further, the male screw 2 starts to mesh with the female screw hole 4 by rotating by a predetermined angle from the screw tightening start position.
(F) The meshing state of the male screw 2 and the female screw hole 4 is a meshed state of not more than one crest (360 degrees) from the position where meshing starts.

  FIG. 9 is a simplified view of the male screw 2 and the female screw hole 4 according to the first embodiment. FIG. 10 is a view showing the meshing state of the screw by the simplified positional relationship between the male screw 2 and the female screw hole 4. With reference to FIG. 9 and FIG. 10, a situation where the above-described (e) and (f) are likely to be screwed will be described in detail.

  In FIG. 9, the threaded portions of the male screw 2 and the female screw hole 4 can be simplified and considered as having spiral grooves along the surface of the cylinder. As shown in FIG. 9A, the male screw 2 is provided with a screw thread in a spiral shape on the outer side of the cylinder. FIG. 9- (b) is a developed view of the threaded portion of the simplified male screw 2 of FIG. 9- (a). The male screw 2 becomes a right triangle as shown in FIG. 9- (b) when a thread connecting the tops of the threads is developed on a plane.

  As shown in FIG. 9- (c), the female screw hole 4 is provided with a screw thread and a valley between them in a spiral shape inside the cylinder. FIG. 9- (d) is a developed view of the threaded portion of the simplified female screw hole 4 of FIG. 9- (c). The female screw hole 4 becomes a right triangle as shown in FIG.

  In the simplified male screw 2 and female screw hole 4, the engagement of the male screw 2 and the female screw hole 4 means that the right-angled triangles shown in FIGS. 9- (b) and 9- (d) advance while sliding along the hypotenuse. Represented as:

  FIG. 10A is a diagram showing a positional relationship in which the male screw 2 immediately meshes with the female screw hole 4 when the male screw 2 starts normal rotation at the position where the male screw 2 and the female screw hole 4 are in contact with each other. The positional relationship shown in FIG. 10- (a) corresponds to a situation in which the above-described (e) screwing is likely to occur. When normal rotation is started in the positional relationship shown in FIG. 10- (a), screwing is most likely to occur.

  FIG. 10B is a diagram illustrating a positional relationship in which the male screw 2 immediately meshes with the female screw hole 4 when the male screw 2 rotates forward X degrees at a position where the male screw 2 and the female screw hole 4 contact each other. In the case of the positional relationship shown in FIG. 10- (b), screwing is likely to occur, but not as much as in the case of the positional relationship shown in FIG. 10- (a).

  FIG. 10- (c) is a diagram showing a positional relationship in which the male screw 2 and the female screw hole 4 are in contact with each other, and after the male screw 2 and the female screw hole 4 have started to engage with each other, one thread (360 degrees) or less has been engaged. is there. The positional relationship shown in FIG. 10- (c) corresponds to the situation in which the above-mentioned (f) screwing is likely to occur. In the case of the positional relationship shown in FIG. 10- (c), screwing tends to occur, but not as much as in the case of the positional relationship shown in FIG. 10- (a).

  FIG. 10- (d) is a diagram showing a positional relationship in which the male screw 2 and the female screw hole 4 are in contact with each other, and the male screw 2 and the female screw hole 4 are meshed by one or more threads (360 degrees). In the case of the positional relationship shown in FIG. 10- (d), almost no screwing occurs.

  The situation in which the above-mentioned screw galling is likely to occur can be solved by changing the screw tightening start position as can be seen from FIGS. 10- (a) and 10- (b). Further, the situation in which the above-described (f) screw galling is likely to occur, as can be seen from FIG. 10- (c) and FIG. Can be eliminated by screwing at low speed.

  The screw tightening device described in Patent Document 1 is intended to prevent the occurrence of screwing due to the above factor (c). However, the screw tightening device described in Patent Document 1 does not support the occurrence of screwing due to the above factors (e) and (f). The above is an explanation of the situation where screwing is likely to occur.

  The screw tightening device 1 according to the first embodiment includes a torque converter 13 for detecting the rotational torque of the driver bit 18. For this reason, in the screw tightening device 1 according to the first embodiment, the torque converter 13 can immediately detect a change in the rotational torque, and can respond immediately to this change.

  Further, in the fitting process, the screwing process, the temporary tightening process, and the final tightening process in the screw tightening, the screw tightening control unit 20 controls the rotation shaft of the screw tightening mechanism unit 10 using the rotational torque of the driver bit 18. . For this reason, the screw fastening apparatus 1 in Embodiment 1 can perform the optimal screw fastening in each process.

  In the screw supply process according to the first embodiment, the screw tightening device 1 fits the tip of the driver bit 18 and the screw head of the male screw 2. Then, the screw fastening device 1 magnetizes the driver bit 18 to attract the male screw 2. When the screw adsorption state is appropriate, the screw tightening control unit 20 determines that the screw can be tightened. Then, the screw tightening control unit 20 lowers the driver bit 18 into the female screw hole 4 of the work 3. Thereafter, the screw tightening control unit 20 performs screw tightening in each step of screw tightening.

  That is, the screw tightening device 1 confirms the suction state after fitting the tip of the driver bit 18 and the screw head of the male screw 2 before screw tightening. Accordingly, the screw tightening device 1 performs the screw tightening in a state where the posture of the male screw 2 is straight in the vertical direction. For this reason, the screw tightening device 1 and the screw tightening method according to Embodiment 1 can suppress the occurrence of screwing.

  In the conforming process according to the first embodiment, the screw tightening control unit 20 reverses the driver bit 18 in a state where the male screw 2 is pressed against the female screw hole 4 of the work 3 with a constant thrust. At this time, the screw tightening control unit 20 reverses the driver bit 18 at a low speed based on the blending time t1 and the blending speed −V1 shown in FIG. At this time, the screw tightening control unit 20 constantly monitors the rotational torque of the driver bit 18. If the rotational torque of the driver bit 18 exceeds the familiarization monitoring torque −T1 in FIG.

  Thereby, the screw fastening apparatus 1 and the screw fastening method in Embodiment 1 can make the fitting state of the male screw 2 and the female screw hole 4 appropriate at the position where the male screw 2 and the female screw hole 4 are in contact with each other. Further, when the shape of the screw thread is not appropriate, or when foreign matter is attached, it can be flipped as a defect. That is, it is possible to deal with the screwing caused by the factors (a), (b), and (c) among the above-described situations where the screwing is likely to occur.

  Furthermore, the tip end of the driver bit 18 and the screw head of the male screw 2 can be completely fitted by the reversing operation of the blending process. The properly fitted male screw 2 is in a posture perpendicular to the female screw hole 4 of the workpiece 3. For this reason, the male screw 2 can be appropriately screwed into the female screw hole 4. Therefore, the screw tightening device 1 and the screw tightening method according to Embodiment 1 can suppress the occurrence of screwing.

  In the screwing process according to the first embodiment, the screw tightening control unit 20 causes the driver bit 18 to rotate normally at a low speed by the screwing time t2 and the screwing speed V2 shown in FIG.

  Thereby, the screw fastening apparatus 1 and the screw fastening method in Embodiment 1 can appropriately mesh the male screw 2 and the female screw hole 4 with about 1 to 2 threads without generating screwing. That is, in the situation where the above-described screwing is likely to occur, the screwing due to the factors (d) and (f) can be prevented.

  The screw tightening control unit 20 constantly monitors the rotational torque of the driver bit 18. When the rotational torque of the driver bit 18 exceeds the screwing monitoring torque T2 in FIG. 2, the screw tightening control unit 20 stops the driver bit 18 suddenly.

  As a result, the screw tightening device 1 and the screw tightening method according to the first embodiment detects a sign of screw threading and stops the screw tightening, so that screw threading can be prevented in advance. At this time, the screw tightening control unit 20 rotates the driver bit 18 at a low speed and accurately detects a sign that screw screwing will occur. For this reason, the screw tightening device 1 and the screw tightening method according to the first embodiment can avoid damage to the male screw 2 or the female screw hole 4 caused by excessive screw tightening. It should be noted that this screwing step can prevent the occurrence of screwing due to the factors (a) to (f) among the above-described situations where screwing is likely to occur.

  It is known that the screwing does not occur in the subsequent tightening process and the final tightening process when the screwing process does not occur in the screwing process. For this reason, by preventing the occurrence of screwing in the screwing process, the occurrence rate of screwing can be made as close to zero as possible.

  In the temporary tightening process according to the first embodiment, the screw tightening control unit 20 causes the driver bit 18 to rotate forward at high speed at the temporary tightening speed V3 illustrated in FIG. The screw tightening control unit 20 constantly monitors the rotational torque of the driver bit 18. When the rotational torque of the driver bit 18 exceeds the temporary tightening end torque T3 of FIG. 2, the screw tightening control unit 20 causes the driver bit 18 to stop suddenly. Thereby, since the screw tightening apparatus 1 and the screw tightening method in Embodiment 1 perform the screw tightening at high speed until the male screw 2 is seated, the cycle time can be shortened.

  In the final tightening process according to the first embodiment, the screw tightening control unit 20 causes the driver bit 18 to rotate forward at a low speed at the final tightening speed V4 shown in FIG. The screw tightening control unit 20 constantly monitors the rotational torque of the driver bit 18. If the rotational torque of the driver bit 18 exceeds the final tightening end torque T4 in FIG. 2, the screw tightening control unit 20 stops the driver bit 18 suddenly and ends the screw tightening. Thereby, the screw fastening apparatus 1 and the screw fastening method in Embodiment 1 can perform final fastening so that it may become an appropriate fastening torque.

  In step S13 in FIG. 4, after the driver bit 18 is suddenly stopped, the screw tightening control unit 20 proceeds to a retry process. If the number of times that the retry operation has been performed is less than or equal to the number of possible retry operations, the screw tightening control unit 20 reverses the driver bit 18. At this time, the screw tightening control unit 20 reverses the driver bit 18 by the retry reverse rotation amount -R5 at the retry reverse rotation speed -V5 shown in FIG. Thus, after loosening the male screw 2 more than the amount engaged in the screwing step, the screw tightening control unit 20 returns to the screwing step. When the number of retry operations exceeds the number of possible retry operations, the screw tightening control unit 20 determines that screw tightening is abnormal.

  As a result, the screw tightening device 1 and the screw tightening method according to Embodiment 1 change the screw tightening start position by completely loosening the male screw 2 in the retry process when a sign of screw twist is detected before the screw twist occurs. To do. For this reason, the screw tightening apparatus 1 and the screw tightening method according to the first embodiment can retighten the screw without causing screwing when the screw tightening is performed again. In addition, this makes it possible to eliminate the factors (c) and (e) in the situation where the above-described screwing is likely to occur.

  In the retry process, the amount of rotation for loosening the male screw 2 is a multiple of 360 degrees + 180 degrees. As a result, the screw tightening device 1 and the screw tightening method according to the first embodiment can change the screw tightening start position even when a sign of screwing is detected immediately after the start of screw tightening.

  There is a limit on the number of retry operations. As a result, the screw tightening device 1 and the screw tightening method according to the first embodiment are poor in quality when the screwing has progressed, when the screw thread shape is not appropriate, or when foreign matter is attached. To do. By doing in this way, it is possible to deal with the screwing caused by the factors (a) and (b) among the situations where the screwing is likely to occur.

  In step S9 of the acclimation process according to the first embodiment, the screw tightening control unit 20 confirms whether the acclimation time t1 has elapsed after the start of rotation at the acclimation speed −V1 in step S6. In step S14 of the screwing process according to the first embodiment, the screw tightening control unit 20 confirms whether the screwing time t2 has elapsed after the start of rotation at the screwing speed V2 in step S11. In step S27 of the retry process according to the first embodiment, the screw tightening control unit 20 confirms whether or not the retry reverse rotation amount—R5 has been made after the retry operation in step S26 is started. However, the screw tightening device 1 and the screw tightening method according to the first embodiment are not limited to this.

  For example, in step S9, the screw tightening control unit 20 may confirm whether or not the driver bit 18 has rotated by the rotation angle corresponding to the blending time t1. In step S14, the screw tightening control unit 20 may confirm whether or not the driver bit 18 has rotated the rotation angle corresponding to the screwing time t2.

  In step S27, the screw tightening control unit 20 may check whether or not the time required for the driver bit 18 to reverse by the retry reverse rotation amount −R5 has elapsed.

DESCRIPTION OF SYMBOLS 1 Screw fastening apparatus, 10 Screw fastening mechanism part, 11 Servo motor, 111 Output shaft, 12 Encoder, 13 Torque converter, 131 Torque converter housing | casing, 14 Support body, 141a Upper arm, 141b Lower arm, 142a Bearing, 142b bearing, 15 coupling, 16a shaft, 16b shaft, 17 universal joint, 18 driver bit, 19 electromagnetic coil, 20 screw tightening control unit, 21 sequencer, 22 servo controller, 23 robot controller, 30 robot, 40a photoelectric sensor, 40b Photoelectric sensor, 40c Photoelectric sensor, 2 male screw, 3 workpiece, 4 female screw hole

Claims (12)

A motor that generates driving force;
A driver bit that is rotated by the driving force of the motor;
Torque detecting means for detecting the torque of the rotation;
A screw tightening control unit for driving the motor and tightening the screw on the driver bit;
The screw tightening control unit is
When the screwdriver bit is tightening the screw in the screw hole, the torque detected by the torque detecting means is compared with a predetermined torque, and the torque detected by the torque detecting means exceeds the predetermined torque. And a screw fastening device for stopping the motor. The screw tightening control unit is
When the torque detected by the torque detection means exceeds a predetermined torque,
The driver bit stops at a predetermined time according to the mechanical system of the screw tightening device,
The rotation angle until the driver bit actually stops is not more than a predetermined rotation angle depending on the size or material of the screw to be used.
The screw tightening device according to claim 1, wherein the motor is stopped. The screw tightening control unit is
After the driver bit stops,
2. The screw tightening device according to claim 1, wherein after the screw tightening operation is started, the motor is driven to rotate the driver bit in the reverse direction by an amount equal to or greater than the amount of the screw engaged with the screw hole. An electromagnetic coil for magnetizing the driver bit;
A screw adsorption state detection means for detecting the posture of the screw adsorbed on the magnetized driver bit;
The screw tightening control unit is
Determining whether the screw posture detected by the screw adsorption state detecting means is appropriate;
The screw tightening device according to claim 1, wherein a screw tightening operation is started when the posture of the screw is appropriate. The torque detecting means includes
The screw tightening device according to claim 1, wherein the screw tightening device is a torque converter that converts a torsion amount according to torque into an electric amount. The screw tightening control unit is
5. The screw tightening device according to claim 4, wherein, after the screw tightening operation is started, the motor is driven to rotate the driver bit in a reverse direction in a state where the screw is in contact with the screw hole. Fit the tip of the driver bit that rotates by driving the motor to the screw head of the male screw,
A screw supplying step for lowering the driver bit;
A screw tightening operation is performed to rotate the driver bit and tighten the male screw into the screw hole, detect the torque of the rotation, compare the detected torque with a predetermined torque, and detect the detected torque in advance. A screw tightening method comprising: a screwing step of stopping the motor when a predetermined torque is exceeded. The screwing step includes
If the detected torque exceeds a predetermined torque,
The driver bit stops at a predetermined time according to the mechanical system of the screw tightening device,
The rotation angle until the driver bit actually stops is not more than a predetermined rotation angle depending on the size or material of the screw to be used.
The screw tightening method according to claim 7, wherein the motor is stopped. After the driver bit stops,
The screw tightening method according to claim 7, further comprising a retry step of driving the driver bit in a reverse direction by an amount equal to or more than an amount of the male screw meshing with the screw hole after the start of the screw tightening operation. The screw supply step includes
Magnetizing the driver bit;
Adsorb the male screw to the magnetized driver bit;
Detecting the posture of the male screw adsorbed to the driver bit;
Judge whether the detected posture of the male screw is appropriate,
When the posture of the male screw is appropriate,
The screw tightening method according to claim 7, wherein the screw tightening operation is started. The screwing step includes
To a torque converter that converts the amount of twist according to torque into an electric quantity,
The screw tightening method according to claim 7, wherein torque of the rotation is detected. Between the screw supplying step and the screwing step,
After the start of the screw tightening operation, the male screw is in contact with the screw hole,
The screw tightening method according to claim 10, further comprising a conforming step of driving the driver bit in a reverse direction.

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