JP6241539B2 - Screw tightening system and screw tightening method - Google Patents

Description

  The disclosed embodiments relate to a screw tightening system and a screw tightening method.

  2. Description of the Related Art Conventionally, there is a screw tightening system in which an articulated robot having a hand at a tip grips a screw tightening device that automatically tightens a screw such as a nutrunner and performs assembly work including a screw tightening process (see, for example, Patent Document 1). .

  In a screw tightening device of such a screw tightening system, a bit engaged with a screw is rotated around an axis. In addition, in the screw tightening device, a reduction gear is provided in the bit driving unit that applies a rotational driving force to the bit to reduce the rotational speed of the motor, thereby securing a torque necessary for the final tightening of the screw from the motor having a high rotational speed.

  In the screw tightening process in such a screw tightening system, the screw is placed in the screw hole, then temporarily tightened until the screw is seated, and finally tightened until the screw reaches the specified torque. From tightening to final tightening is performed using a bit drive unit with a reduction gear.

JP 2006-95624 A

  However, the screw tightening system as described above has a problem that the output speed of the bit drive unit is slow and it takes time to tighten the screw because the bit drive unit has a speed reducer. In particular, when the number of screws is large, the time required for tightening the screws greatly affects the tact time of the entire assembly process.

  One aspect of the embodiments has been made in view of the above, and an object of the present invention is to provide a screw tightening system and a screw tightening method capable of reducing the tact time of the entire assembly process including the screw tightening process. .

A screw tightening system according to an aspect of an embodiment includes a robot, a control device, a first bit driving unit, a second bit driving unit, a bit holding unit, a dedicated control device, and a torque detector . The robot is an articulated robot having a hand at the tip. The control device drives and controls the robot. The first bit driving unit is selectively held by the hand and directly outputs a rotational driving force by a motor. The second bit driving unit is selectively gripped by the hand and outputs a rotational driving force by a motor via a speed reducer. The bit holding unit is attached to at least one of the first bit driving unit and the second bit driving unit, and holds a bit that rotates around an axis by the input rotational driving force. The dedicated control device drives and controls the second bit driving unit. The torque detector is provided in the second bit drive unit, detects the torque of a screw tightened and loosened by the second bit drive unit, and outputs the detected torque value to the dedicated control device.

  According to one aspect of the embodiment, the tact time of the entire assembly process including the screw tightening process can be shortened.

FIG. 1A is a schematic explanatory diagram of a screw tightening system according to an embodiment. FIG. 1B is a schematic explanatory diagram of a bit driving unit and a bit holding unit. FIG. 2A is a front view of the screw tightening device. FIG. 2B is a right side view of the screw fastening device. 2C is a cross-sectional view taken along line BB shown in FIG. 2B. FIG. 3A is a cross-sectional view showing the attachment / detachment mechanism. FIG. 3B is a cross-sectional view showing the attachment / detachment mechanism. FIG. 4 is an explanatory diagram of the operation of each part during screw gripping. FIG. 5 is a cross-sectional view of the bit holding portion when gripping a screw. FIG. 6 is a system configuration diagram of the screw tightening system. FIG. 7 is a control configuration diagram of the screw tightening system. FIG. 8 is a functional block diagram of the screw tightening system. FIG. 9 is a flowchart showing the procedure of the screw tightening method.

  Hereinafter, embodiments of a screw fastening system and a screw fastening method disclosed in the present application will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

  FIG. 1A is a schematic explanatory diagram of a screw tightening system according to an embodiment. In the screw tightening system described below, not only the screws are tightened, but also the work of loosening the tightened screws is performed.

  Moreover, the screw tightened and loosened by such a screw tightening system includes a bolt and the like. Here, the term “screw” is used as a general term for a fastening member provided with a spiral groove such as a bolt.

  As shown in FIG. 1A, in the screw tightening system 1, the robot 70 performs an operation of tightening or loosening a screw using a screw tightening device. The screw fastening device includes a bit driving unit 11 and a bit holding unit 18. In addition, such a screw fastening apparatus can be used for any operation | work which tightens or loosens a screw.

  As shown in FIG. 1A, there are two types of bit driving units 11, a first bit driving unit 11a and a second bit driving unit 11b. Both the first bit driving unit 11a and the second bit driving unit 11b output the rotational driving force around the axis to the bit holding unit 18 via the output shaft.

  The first bit driving unit 11a includes a motor Ma, and directly outputs a rotational driving force by the motor Ma. Since the rotational driving force by the motor Ma is directly output from the first bit driving unit 11a, a rotational driving force having a high rotational speed is output.

  On the other hand, the second bit drive unit 11b includes a motor Mb and a speed reducer G, and outputs a rotational driving force by the motor Mb via the speed reducer G. From such a second bit drive unit 11b, the rotational driving force of the motor Mb is decelerated by the speed reducer G, and a rotational driving force of high torque (low rotational speed) is output. Here, it is assumed that the capabilities of the motor Ma and the motor Mb are equal.

  As shown in FIG. 1A, the bit holding part 18 holds the bit 20 engaged with the screw to be tightened on the tip side. Further, the bit holding unit 18 is attached to the bit driving unit 11 at the end side. Specifically, the bit holding unit 18 is attached to at least one of the first bit driving unit 11a and the second bit driving unit 11b.

  In the bit holding unit 18, when the rotational driving force output from the first bit driving unit 11 a or the second bit driving unit 11 b is input, the bit 20 rotates around the axis by the input rotational driving force.

  As shown in FIG. 1A, the screw tightening system 1 includes a robot 70. The robot 70 is a multi-joint robot having a plurality of arm portions and a hand 71 at the tip. In the robot 70, when the hand 71 holds the bit driving unit 11, a screw tightening device can be provided as an external shaft of the robot 70.

  The screw tightening system 1 further includes a control device 80. In addition to driving and controlling each joint portion of the robot 70, the control device 80 drives and controls the motor Ma of the first bit driving portion 11 a gripped by the hand 71 as an external axis of the robot 70. Therefore, it is not necessary to separately provide a control device for controlling the first bit driver 11a.

  By the way, in the screw tightening process in the screw tightening system 1 described above, the screw is arranged in the screw hole, and then temporarily tightened until the screw is seated (hereinafter referred to as “temporary tightening process”), and finally the screw is defined. This is a flow of final tightening until the torque is reached (hereinafter referred to as “final tightening process”). Each of these steps is performed by the robot 70 using a screw tightening device.

  Conventionally, in order to obtain a prescribed torque by final tightening, tightening of screws (temporary tightening step and final tightening step) has been performed by a bit drive unit with a speed reducer. In addition, since the bit drive part needs to reach a regulation torque by this fastening, it usually has a reduction gear.

  However, when a bit drive unit having a speed reducer is used, the number of rotations output from the bit drive unit is slow (low rotation number), and it takes time to tighten the screws. For example, when the output rotational speed is 600 rpm, it takes 5 seconds / screw to fasten a screw having a pitch of 1 mm and a length of 50 mm, and the time required to fasten 30 screws is about 150 seconds. Thus, when the number of screws is large, the time required for tightening is prolonged. In addition, since the tightening time of the screw is prolonged, the tact time of the entire assembly process is prolonged.

  Therefore, in the screw tightening system 1 according to the embodiment, the hand 71 changes the first bit driving unit 11a and the second bit driving unit 11b. That is, in the temporary fastening step described above, the first bit driving unit 11a having a high rotational speed is used, and in the final fastening step, the second bit driving unit 11b having a high torque is used. Thereby, screwing can be performed with the rotation speed and torque suitable for each process.

  In the screw tightening system 1, the bit holding unit 18 is detachably attached to the first bit driving unit 11a or the second bit driving unit 11b. Further, the bit holding unit 18 is shared by the first bit driving unit 11a and the second bit driving unit 11b. Thereby, the number of parts can be reduced.

  Here, the bit holding unit attached to the bit driving unit (the first bit driving unit or the second bit driving unit) will be described with reference to FIG. 1B. FIG. 1B is a schematic explanatory diagram of a bit driving unit and a bit holding unit. In FIG. 1B, for each bit type, the bit and the code of the bit holding unit are numbered in the form of “−number”.

  As described above, the bit holding unit 18 is detachably attached to the first bit driving unit 11a or the second bit driving unit 11b. The bit holding portion 18 can be replaced according to the size and type of the screw to be tightened or loosened.

  As shown in FIG. 1B, the bit 20 held by the bit holding unit 18 varies depending on the size and type of the screw. FIG. 1B shows three bit holding units 18-1, 18- that hold three types of bits 20-1, 20-2, 20-3 corresponding to the nominal diameters of screws (for example, M6, M8, M10). 2, 18-3.

  Three bit holding units 18-1 to 18-3 are detachably attached to the first bit driving unit 11a and the second bit driving unit 11b, respectively. That is, the three bit holding units 18-1 to 18-3 are shared by the first bit driving unit 11a and the second bit driving unit 11b.

  In the screw tightening system 1, the bit holding unit 18 includes a rotating unit, a linear motion unit, and a pressing unit. In the bit holding part 18, the bit 20 can be made to follow the screw | screw which moves to an axial direction by pressing the bit 20 to a front end side with a press part. The configuration of such a bit holding unit 18 will be described later with reference to FIG. 2A and the like.

  Further, in the screw tightening system 1, as described above, the robot 70 uses the first bit drive unit 11a for temporary tightening of screws and uses the second bit drive unit 11b for final tightening. In this case, in the temporary tightening of the screw, the first bit driving unit 11a is used because a high rotational speed is preferable to a high torque in order to fasten the screw quickly. Further, in the final tightening, since a high torque is required to securely tighten the screw, the second bit driving unit 11b is used. As a result, the screws can be temporarily tightened at a high speed. The time required for the entire screw tightening can be shortened.

  In the screw tightening system 1, the robot 70 holds the first bit driving unit 11 a with the hand 71, and then attaches the bit holding unit 18 to the first bit driving unit 11 a to temporarily tighten the screws. In addition, the robot 70 removes the bit holding unit 18 from the first bit driving unit 11 a and releases the grip of the first bit driving unit 11 a by the hand 71.

  Further, after gripping the second bit driving unit 11b, the robot 70 attaches the bit holding unit 18 to the second bit driving unit 11b and performs final screw tightening. That is, the robot 70 temporarily tightens the screw with the first bit driving unit 11a, and when the temporary tightening is finished, the robot 70 switches from the first bit driving unit 11a to the second bit driving unit 11b, and with the second bit driving unit 11b. Perform final tightening. When there are a plurality of screws, for example, all the screws are temporarily tightened by the first bit driving unit 11a, and then the second bit driving unit 11b is moved to the final tightening of all the screws. By doing in this way, the tact time as the whole screw fastening operation can be shortened.

  In the screw tightening system 1 according to the embodiment, the robot 70 is a single-arm multi-joint robot. However, the present invention is not limited to this, and the robot 70 may be a double-arm robot. By using a double-arm robot, for example, the first bit driving unit 11a is gripped by one arm, the second bit driving unit 11b is gripped by the other arm, and a screw is temporarily tightened by one arm. Tightening can be done with the other arm.

  Thus, by making the robot 70 a double-arm robot, it is possible to eliminate the time required for switching from the first bit driving unit 11a to the second bit driving unit 11b. As a result, the time required for screw tightening can be further shortened.

  Further, in the screw tightening system 1 according to the embodiment, the control device 80 drives and controls the motor Ma of the first bit driving unit 11a held by the hand 71 as an external shaft of the robot 70, but the first bit driving unit 11a. In addition, the second bit driver 11b may be driven and controlled. Thereby, the drive control of the robot 70, the 1st bit drive part 11a, and the 2nd bit drive part 11b is attained by the single control apparatus 80, and it becomes a simple structure.

  In the second bit drive unit 11b, precise control relating to torque application is required in the final tightening of the screw. Therefore, dedicated control devices 81 and 82 (see FIG. 7) for driving and controlling the second bit driving unit 11b may be separately provided.

  Below, with reference to FIG. 2A-FIG. 2C, a screw fastening apparatus is demonstrated in detail. FIG. 2A is a front view of the screw tightening device. FIG. 2B is a right side view of the screw fastening device. FIG. 2C is a cross-sectional view taken along line BB in FIG. 2B. 2B is a cross section taken along the line AA shown in FIG. 2A.

  2A to 2C is an axis common to each part of the screw tightening device 10. In the following description, the upper side (the upper end side of the bit driving unit 11) in the drawing may be referred to as the end side, and the lower side (the lower end side of the bit 20) in the drawing may be referred to as the leading end side. Furthermore, as described above, there are two types of the bit driving unit 11, the first bit driving unit 11 a and the second bit driving unit 11 b (see FIG. 1A). Hereinafter, the bit driving unit 11 will be generically described. To do.

  As shown in FIGS. 2A and 2B, the screw fastening device 10 includes a bit driving unit 11, an attaching / detaching unit 17, a bit holding unit 18, and a pressing unit 27. The screw tightening device 10 is a so-called nutrunner that automatically tightens a screw (or loosens and removes the screw).

  As shown in FIGS. 2A and 2B, the bit driving unit 11 includes a flat base 12 and a cylindrical casing 13 which is provided on the upper surface of the base 12 and is long in the axis AX direction. On the upper surface of the base 12, in addition to the housing 13, a first drive source 28 that drives the attachment / detachment unit 17, a block 14 that is gripped by the hand 71 (see FIG. 6) of the robot 70, and the like are disposed.

  In addition, motors Ma and Mb, a reduction gear G (see FIG. 6), and the like are disposed in the housing 13 from the distal end side of the bit driving unit 11 to the distal end side that is the base 12 side. For example, servo motors are used as the motors Ma and Mb. The illustrated configuration of the bit driver 11 corresponds to the configuration of the second bit driver 11b described above. On the other hand, the first bit driving unit 11a is different in configuration from the second bit driving unit 11b in that the speed reducer is excluded (see FIG. 1A).

  As shown in FIG. 2C, the bit driving unit 11 further includes an output shaft 15 that extends coaxially with the axis AX from the end surface on the front end side, that is, the lower surface of the base 12. The output shaft 15 outputs the rotational driving force around the axis AX output from the motors Ma and Mb (see FIG. 1A) to the bit holding unit 18. The output shaft 15 is formed with a rectangular shaft at the distal end side, and a torque transmission shaft 16 is coaxially connected to the distal end side that becomes the rectangular shaft.

  As described above, the bit driving unit 11 outputs the rotational driving force around the axis AX from the motors Ma and Mb (see FIG. 1A) to the bit holding unit 18 via the output shaft 15 (torque transmission shaft 16). The bit 20 held in the bit holding unit 18 is rotationally driven.

  In the bit driving unit 11 (that is, the second bit driving unit 11b), the driving force from the motor Mb (see FIG. 1A) is output to the bit holding unit 18 via the speed reducer G, thereby tightening the screws. Necessary torque can be obtained. Further, the bit driving unit 11 includes a torque detector TD (see FIG. 6) that detects the torque of the screw to be tightened or loosened.

  As shown in FIGS. 2A and 2B, the bit driver 11 is provided with a detachable portion 17 on the bottom surface of the base 12. The detachable part 17 attaches the bit holding part 18 to the lower surface of the base 12 so as to be coaxial with the bit driving part 11. The attachment / detachment unit 17 includes an attachment / detachment mechanism that allows the bit holding unit 18 to be attached / detached. Details of the attachment / detachment mechanism will be described later with reference to FIGS. 3A and 3B.

  As shown in FIGS. 2A and 2B, the bit holding unit 18 includes a cylindrical housing 19, and holds the bit 20 on the distal end side of the housing 19.

  Bit 20 engages the head of the screw and rotates the screw about axis AX (clockwise or counterclockwise). As described above, the bit 20 is replaceable and may be replaced according to the type and size of the screw, or may be replaced with a new one due to wear or deterioration.

  As shown in FIG. 2C, the bit holding unit 18 further includes a socket 21 and a joint 24. The bit holding unit 18 holds the bit 20 via a socket 21 and a joint 24 disposed inside the housing 19.

  The socket 21 is formed in a cylindrical shape, and is disposed coaxially with the housing 19 inside the housing 19. The front end side of the socket 21 is connected to a joint 24 that is coaxially disposed inside the housing 19 in the same manner as the socket 21.

  A protrusion 19 a that protrudes toward the axis AX is provided on the inner peripheral surface of the housing 19. The protruding portion 19 a is provided to have a slightly larger diameter than the outer peripheral surface of the socket 21. The socket 21 is disposed inside the housing 19 in a state where the socket 21 is regulated so as to be along the axis AX direction by the protruding portion 19a.

  The socket 21 includes a rotating part 22 and a linear motion part 23. The rotating portion 22 is provided between the outer peripheral surface of the cylindrical main body of the socket 21 and the inner peripheral surface of the housing 19 on the end side. The rotating part 22 is a bearing and supports the socket 21 main body so as to be rotatable around the axis AX. For example, a needle bearing can be used as the rotating unit 22.

  The linear motion portion 23 is provided on the inner peripheral surface of the socket 21 body. The linear motion portion 23 enables the socket 21 to move linearly in the axis AX direction with respect to the torque transmission shaft 16 inserted in the axis AX direction from the terminal end side of the socket 21 and cannot rotate about the axis AX. To do.

  The torque transmission shaft 16 transmits the rotational driving force around the axis AX output from the output shaft 15 of the bit driving unit 11 to the bit holding unit 18. A rectangular recess that can be fitted to the rectangular shaft of the output shaft 15 is provided on the upper surface (end-side end surface) of the torque transmission shaft 16.

  A groove extending in the direction of the axis AX, a so-called spline, is provided on the outer peripheral surface of the torque transmission shaft 16. On the other hand, the linear motion part 23 is formed in a cylindrical shape, and a spline that fits with the spline of the torque transmission shaft 16 is provided on the inner peripheral surface of the cylindrical body.

  By the linear motion part 23 having such a spline structure, the socket 21 linearly moves in the axis AX direction following the external force in the axis AX direction. The socket 21 is stationary when no external force is applied. Further, the socket 21 is detachable from the bit driving unit 11 side in the axis AX direction.

  As shown in FIG. 2C, the joint 24 connected to the distal end side of the socket 21 rotates following the socket 21 and rotates following the socket 21 when the socket 21 moves linearly. The bit 20 is detachably connected to the distal end side of the joint 24.

  Between the inner peripheral surface of the housing 19 and the outer peripheral surface of the socket 21, centering taper members 25, 25 for extending the bit 20 in the axis AX direction are provided. The taper members 25, 25 are formed in an annular shape along the inner peripheral surface of the housing 19 and the outer peripheral surface of the socket 21, and are arranged with their inclined surfaces facing each other.

  Centering taper portions 26 and 26 when the bit 20 is contracted in the axis AX direction are provided on the inner peripheral surface of the housing 19 and the outer peripheral edge of the joint 24, respectively. The tapered portions 26, 26 are provided with their inclined surfaces facing each other along the inner peripheral surface of the housing 19 and the outer peripheral edge of the joint 24.

  In addition, a pressing portion 27 that presses the socket 21 toward the distal end side is provided inside the housing 19. The pressing portion 27 is, for example, a compression coil spring, and is disposed coaxially on the end side of the socket 21.

  The socket 21 is constantly urged toward the distal end side by the spring which is the pressing portion 27 via the linear motion portion 23. That is, the bit 20 integrally connected to the socket 21 and the joint 24 in the axis AX direction is pressed toward the distal end side by the urging force of the pressing portion 27 through the socket 21 and the joint.

  From here, with reference to FIG. 3A and FIG. 3B, the attachment / detachment mechanism of an attachment / detachment part is demonstrated. FIG. 3A is a cross-sectional view showing an attaching / detaching mechanism of the attaching / detaching portion (before attaching the bit holding portion). FIG. 3B is a cross-sectional view showing the attaching / detaching mechanism of the attaching / detaching portion (after the bit holding portion is attached).

  As shown in FIG. 3A, the detachable portion 17 includes a pair of air cylinders 28, 28 as a first drive source. The pair of air cylinders 28 and 28 are disposed on the upper surface of the base 12 on the bit drive unit 11 side with a phase difference of 180 degrees on a concentric circle of the axis AX.

  The telescopic rods 28a, 28a of the pair of air cylinders 28, 28 pass through the base 12 and the distal end side is disposed on the bit holding portion 18 side. The extensible rods 28a and 28a are connected to the floating joints 29 and 29 on the bit holding portion 18 side at the distal end side.

  The floating joints 29 and 29 are connected to a flange portion 31 provided on the outer peripheral surface of the short cylindrical circular receiving portion 30. The circular receiving portion 30 is provided so as to be extendable and contractible in the axis AX direction, and expands and contracts in the axis AX direction following the extension and contraction of the extension rods 28a and 28a.

  The circular receiving portion 30 is provided with a circular concave portion 32 on the end surface on the front end side. The inner peripheral surface of the circular recess 32 is a tapered surface 33 provided to be inclined so as to increase the diameter. The circular receiving part 30 is provided with a communication hole 34 that communicates from the bit driving part 11 side to the bit holding part 18 side.

  A cylindrical portion 35 is fitted into the communication hole 34. The cylindrical portion 35 is inserted with the output shaft 15 of the bit driving portion 11 when the bit holding portion 18 is attached. A tapered surface 36 is provided on the inner peripheral edge on the distal end side of the cylindrical portion 35 so as to increase the diameter.

  A through hole 37 penetrating in the thickness direction is provided on the inner peripheral surface of the cylindrical portion 35. A steel ball 38 is disposed in the through hole 37. The opening diameter on the inner peripheral surface side of the through hole 37 is formed smaller than the diameter of the steel ball 38. When the telescopic rods 28a, 28a of the air cylinders 28, 28 are contracted, the steel ball 38 is in a state of being retracted into the space formed by the tapered surface 36.

  On the other hand, on the bit holding unit 18 side, a flange portion 39 is provided on the end face of the bit holding unit 18. A circular convex portion 40 that can be fitted into the circular concave portion 32 on the main body portion 11 side is provided on the end side end face of the flange portion 39.

  A cylindrical part 41 that can be fitted into the cylindrical part 35 on the main body part 11 side is provided on the end face of the circular convex part 40. A V-shaped groove 42 is provided on the outer peripheral surface of the cylindrical portion 41 on the end side. A tapered surface 43 is provided on the side peripheral surface of the circular convex portion 40 so as to be inclined toward the distal end surface.

  As shown in FIG. 3B, when the bit holding unit 18 is attached to the bit driving unit 11, the cylinder 41 on the bit holding unit 18 side is fitted into the cylinder 35 on the bit driving unit 11 side. The output shaft 15 is inserted through the tube portion 41. The output shaft 15 enters the inside of the housing 19 through the inner peripheral surface of the cylindrical portion 41, and the tip end side is connected to the terminal end side of the torque transmission shaft 16.

  At this time, when the cylindrical portion 41 on the bit holding portion 18 side reaches the position of the steel ball 38, the telescopic rods 28a, 28a are extended toward the bit holding portion 18 side by driving the air cylinders 28, 28.

  In a state where the telescopic rods 28 a and 28 a are extended, the steel ball 38 disposed in the through hole 37 is pushed out to the inner peripheral surface side of the cylindrical portion 35 by the inner peripheral surface of the communication hole 34. In addition, since the diameter of the inner peripheral surface side of the through hole 37 is smaller than the diameter of the steel ball 38, the steel ball 38 is restricted from protruding more than a predetermined dimension.

  The steel ball 38 protruding by a predetermined dimension is fitted into a V-shaped groove 42 provided in the cylinder part 41 on the bit holding part 18 side. When the steel ball 38 is fitted in the V-shaped groove 42, the tapered surface 36 of the cylindrical portion 35 on the bit drive unit 11 side and the tapered surface 43 of the cylindrical portion 41 on the bit holding unit 18 side come into contact with each other.

  As a result, the force by which the steel ball 38 pushes the V-shaped groove 42 and the force by which the tapered surface 36 of the cylindrical portion 35 on the bit driving portion 11 side pushes the tapered surface 43 of the cylindrical portion 41 on the bit holding portion 18 side, The holding unit 18 is locked to the bit driving unit 11. The bit holding unit 18 is detachably attached to the bit driving unit 11 by such a so-called attachment / detachment mechanism having a coupler structure. Further, it can be easily attached and detached by a simple operation.

  Although not shown, the attachment / detachment unit 17 includes a positioning mechanism for preventing the bit driving unit 11 and the bit holding unit 18 from rotating relative to each other around the axis AX when or after the bit holding unit 18 is installed.

  The detachable part 17 includes a positioning pin and a bush as a positioning mechanism. The positioning pin is formed in a shaft shape protruding from the bottom surface of the base 13 of the bit driving unit 11 toward the tip side. The bush is attached to a through hole provided in the flange portion 39 of the bit holding portion 18 and is provided so that a positioning pin can be inserted. The position where the bush is provided is a position corresponding to the position of the positioning pin after the bit holding portion 18 is mounted.

  Further, when the bit holding portion 18 is mounted, the phase of the distal end side (rectangular shaft) of the output shaft 15 and the rectangular concave portion of the torque transmission shaft 16 needs to match. Although not shown, the attachment / detachment unit 17 includes a phase matching mechanism using a dog or a sensor, for example.

  Here, returning to FIGS. 2A to 2C, the screw holding mechanism will be described. 2A and 2B, the screw tightening device 10 further includes a second drive source 50, an arm 52, and a chuck 54 as a screw gripping mechanism.

  As shown in FIG. 2B, the air cylinder 50 as the second drive source includes an extendable rod 50a that expands and contracts from the cylinder in the axis AX direction. A spring portion 51 is connected to the distal end side of the telescopic rod 50a. The spring portion 51 includes a spring 51a and a rod 51b inside the cylinder. For example, a compression coil spring can be used as the spring 51a.

  Further, the air cylinder 50 and the spring portion 51 are arranged coaxially in parallel with the axis AX direction. In the spring portion 51, the rod 51 b biased by the spring 51 a is connected to the arm 52 on the distal end side.

  As shown in FIGS. 2A and 2B, the arm 52 is formed in a rectangular plate shape. The arm 52 is provided with a bent portion so as to be close to the housing 19 side of the bit holding portion 18. A linear guide 53 is provided between the arm 52 and the housing 19 to guide the linear movement of the arm 52 in the direction parallel to the axis AX direction.

  The arm 52 is connected to the link portion of the chuck 54 on the distal end side. The chuck 54 includes a pair of arm portions 54a and 54a and claw portions 54b and 54b. Each of the arm portions 54a and 54a includes a plurality (three) of shafts. A link part is formed by the arm part 54a, the claw part 54b, and the shaft.

  As shown in FIG. 2B, in the air cylinder 50, the chuck 54 is opened and closed via the arm 52 by the expansion and contraction of the expansion rod 50a. The spring part 51 always urges the chuck 54 to open. As a result, an appropriate grip force can be obtained when the chuck 54 grips the screw.

  The chuck 54 is provided to be rotatable around the axis AX. 2B, the chuck 54 opens and closes in a direction perpendicular to the thickness direction of the arm 52. In FIG. 2B, for example, the chuck 54 can be opened and closed in a direction parallel to the thickness direction of the arm 52. .

  From here, with reference to FIG. 4, operation | movement of each part at the time of screw holding is demonstrated. FIG. 4 is an explanatory diagram of the operation of each part during screw gripping. In FIG. 4, the upper half of the figure shows a state where the bit is engaged with the screw, and the lower half shows a state where the chuck is closed and the screw is gripped from there.

  As shown in FIG. 4 (upper half), when the screw tightening device 10 is moved to the tip side along the axis AX direction and brought close to the screw 60 installed on the screw base 61 (in FIG. The tip side of the bit 20 is engaged with the head (upper end surface) of the screw 60. At this time, the chuck 54 is in an open state. That is, one of the pair of opposing leg portions 54a and 54a and the claw portions 54b and 54b is separated from the other. A screw hole (not shown) is provided at the tip of the screw 60 installed on the screw base 61.

  Then, as shown in FIG. 4 (lower half), when the screw tightening device 10 is further moved to the distal end side, the bit 20 moves to the distal end side by a distance corresponding to the length of the screw 60. At this time, the chuck 54 is in a closed state. That is, the pair of opposing claws 54b and 54b are close to each other, and the claw portions 54b and 54b grip the head of the screw 60 (side circumferential surface side and part of the lower surface).

  When the chuck 54 tightens the screw 60 by the screw tightening device 10, the bit 20 engaged with the screw 60 resists the pressing of the spring 27 (see FIG. 2C) as the pressing portion, and the end side of the bit holding portion 18. It closes in a state where it has moved by the length of the screw 60. Further, the closed chuck 54 is opened before the bit 20 starts rotating to tighten the screw 60.

  Further, when the screw 54 is loosened by the screw tightening device 10, when the loosening of the screw 60 is completed, the chuck 20 resists the pressure of the spring 27 (see FIG. 2C) as the pressing portion, and the end side of the bit holding portion 18. Are closed by the length of the screw 60 and the rotation of the bit stopped.

  In this way, by controlling the opening and closing timing of the chuck 54, when the screw 60 is tightened or loosened by the screw tightening device 10, it is possible to reliably prevent the screw 60 from popping out by pressing by the bit 20.

  Note that the timing for opening and closing the chuck 54 may be configured to be controlled by a control device 80 (see FIG. 6) described later. In addition, a control device dedicated to opening and closing the chuck 54 may be provided separately and controlled by such a control device.

  Next, the operation of each part of the bit holding unit when holding the screw will be described with reference to FIG. FIG. 5 is a cross-sectional view of the bit holding portion when gripping a screw.

  As shown in FIG. 5, when gripping the screw 60, in the bit holding portion 18, the bit 20 moves (linearly moves) toward the end side along the axis AX in the housing 19. As a result, the socket 21 integrally connected in parallel with the bit 20 in the axis AX direction via the joint 24 moves toward the end side.

  At this time, the socket 21 moves linearly while being guided by the linear movement portion 23 of the spline structure. Due to the movement of the socket 21 (the linear motion portion 23) toward the end side, the spring 27 as the pressing portion is compressed, and the bit 20 on the distal end side is pressed through the socket 21 and the joint 24. As a result, the bit 20 is always pressed against the screw 60.

  According to such a screw tightening device 10, the bit holding portion 18 is provided with the pressing portion 27 that constantly presses the bit 20 toward the distal end side of the bit holding portion 18, whereby the screw 60 to be tightened or loosened in the axis AX direction. The bit 20 can follow the movement. This eliminates the need for a drive source and a transmission mechanism that have been required to follow the movement of the screw 60 in the axis AX direction, and enables the bit holding portion 18 to have a small diameter. Further, the screw fastening device 10 as a whole is simple in structure and small in size.

  In addition, since the pressing portion 27 is provided inside the bit holding portion 18 (housing 19), the bit holding portion 18 can be further reduced in diameter. In addition, by using a simple member such as a spring for the pressing portion 27, the screw fastening device 10 can be configured simply, compactly, and inexpensively.

  Further, in the screw tightening device 10, since the first drive source (air cylinder) 28 for driving the attaching / detaching portion 17 is provided on the bit drive portion 11 side, the bit holding portion 18 is further reduced in diameter. Furthermore, the structure is simple and small.

  From here, the system configuration | structure of the screw fastening system 1 is demonstrated with reference to FIG. FIG. 6 is a system configuration diagram of the screw tightening system 1. FIG. 6 shows a three-dimensional orthogonal coordinate system including the Z axis with the vertical downward direction as the positive direction for easy understanding.

  As shown in FIG. 6, the screw tightening system 1 further includes a robot 70 and a control device 80 in addition to the screw tightening device 10 described above. Further, the screw tightening system 1 includes a work table 62 for tightening or loosening the screws. In the work table 62, screws 60 are installed on the screw table 61 (see FIG. 4).

  As shown in FIG. 6, the robot 70 is, for example, a single-armed multi-joint robot. Specifically, the robot 70 includes the hand 71, the first arm unit 72, the second arm unit 73, the third arm unit 74, the fourth arm unit 75, and the fifth arm unit 76 described above. And a base part 77. The robot 70 may be a double-arm robot, for example.

  The first arm portion 72 is supported at the base end portion by the second arm portion 73. The second arm portion 73 is supported at the base end portion by the third arm portion 74 and supports the first arm portion 72 at the distal end portion.

  The third arm portion 74 is supported at the base end portion by the fourth arm portion 75 and supports the second arm portion 73 at the distal end portion. The fourth arm portion 75 is supported at the base end portion by the fifth arm portion 76 and supports the third arm portion 74 at the distal end portion.

  The fifth arm portion 76 is supported at the base end portion by a base portion 77 fixed to the floor surface or the like, and supports the fourth arm portion 75 at the front end portion. In addition, actuators such as servo motors are mounted on the joints, which are the connecting parts of the first arm part 72 to the fifth arm part 76, respectively. The robot 70 can perform a multi-axis operation by driving an actuator.

  Specifically, the joint actuator that connects the first arm portion 72 and the second arm portion 73 rotates the first arm portion 72 about the B axis. Further, the joint actuator that connects the second arm portion 73 and the third arm portion 74 rotates the second arm portion 73 about the U axis.

  In addition, the joint actuator that connects the third arm portion 74 and the fourth arm portion 75 rotates the third arm portion 74 about the L axis. Further, the joint actuator that connects the fourth arm portion 75 and the fifth arm portion 76 rotates the fourth arm portion 75 about the S axis.

  The robot 70 also includes individual actuators that rotate the first arm 72 around the T-axis, the second arm 73 around the R-axis, and the third arm 74 around the E-axis.

  That is, the robot 70 has seven axes. Then, the robot 70 can perform various multi-axis operations combining seven axes based on an operation instruction from a control unit 90 (see FIG. 8) of the control device 80 described later.

  The distal end portion of the first arm portion 72 is a distal end movable portion of the robot 70, and a hand 71 is attached to the distal end movable portion. The hand 71 grips the block 14 (see FIG. 2A and the like) of the screw fastening device 10 at the most distal portion of the robot 70.

  As shown in FIG. 6, the control device 80 is a so-called robot controller, and drives and controls the actuators of the joint portions including the hand 71 of the robot 70 and the arm portions 72 to 76. The control device 80 and the robot 70 are connected by a cable 78 or the like.

  The robot controller 80 as a control device drives and controls the first bit driving unit 11a. The robot controller 80 and the first bit driving unit 11a are connected by a cable 79 or the like. The second bit drive unit 11b is driven and controlled by dedicated control devices 81 and 82 (see FIG. 7) described later.

  As shown in FIG. 6, of the two types of bit driving units 11, the first bit driving unit 11 a includes a motor Ma. The second bit drive unit 11b includes a motor Mb, a reduction gear G, and a torque detector TD. In the second bit drive unit 11b, the motor Mb, the reduction gear G, and the torque detector TD are arranged in series.

  Either the first bit driving unit 11 a or the second bit driving unit 11 b is selectively held by the hand 71. FIG. 6 shows an example in which the first bit driver 11a is selected. A bit holding unit 18 holding the bit 20 is attached to the selected first bit driving unit 11a.

  From here, the control configuration of the screw tightening system will be described with reference to FIG. FIG. 7 is a control configuration diagram of the screw tightening system. As shown in FIG. 7, the robot controller 80 as a control device controls the drive of the robot 70 and also controls the first bit driving unit 11a. The robot controller 80 can also drive and control the second bit driving unit 11b.

  As shown in FIG. 7, the robot controller 80 drives and controls each joint portion of the robot 70 and drives and controls the hand 71 via the tip joint portion. Further, the robot controller 80 controls driving of the first bit driving unit 11 a held by the hand 71. Specifically, the motor Ma of the first bit driving unit 11 a is driven and controlled as an external shaft of the robot 70.

  Further, as shown in FIG. 7, the screw tightening system 1 includes a programmable controller 81 and a nutrunner controller 82 between the robot controller 80 and the second bit driving unit 11b as a control device dedicated to the second bit driving unit 11b. Further prepare.

  As described above, since the second bit driving unit 11b outputs a high torque rotational driving force, precise driving control is required. Therefore, the second bit drive unit 11b includes a torque detector TD. The torque value detected by the torque detector TD is output to the programmable controller 81 via the nut runner controller 82.

  When the torque detected by the torque detector TD reaches a predetermined torque indicating the end of the final tightening process, a drive stop signal is output from the programmable controller 81 to the motor Mb of the second bit drive unit 11b.

  As shown in FIG. 7, the second bit drive unit 11 b is included in the control system of the robot controller 80. Therefore, the second bit driving unit 11b can be driven and controlled by either the robot controller 80 or the programmable controller 81. The selection may be appropriately set by the user. Further, the drive control of the second bit drive unit 11b may be performed not by the control system of the robot controller 80 but by a separate control system by the programmable controller 81.

  In such a screw tightening system 1, in the screw tightening operation, first, the robot 70 selects the first bit driving unit 11 a and grips the first bit driving unit 11 a with the hand 71. Next, the robot 70 attaches the bit holding unit 18 to the first bit driving unit 11 a held by the hand 71. The bit holding unit 18 is attached and detached by driving and controlling the pair of air cylinders 28 and 28 (see FIG. 3A and the like) as a first drive source by the robot controller 80.

  Then, the robot 70 performs a temporary screw tightening operation. When the temporary fastening is completed, first, the robot 70 removes the bit holding unit 18 from the first bit driving unit 11a. Next, the robot 70 releases the grip of the first bit driving unit 11 a by the hand 71. Next, the robot 70 selects the second bit driving unit 11 b and holds the second bit driving unit 11 b with the hand 71. That is, the robot 70 changes the first bit driving unit 11a to the second bit driving unit 11b.

  Then, the robot 70 performs a final tightening operation of the screw. When the final tightening is completed, that is, when the screw tightening operation is completed, the robot 70 is changed to the first bit drive unit 11a again to shift to the next screw tightening operation, for example.

  From here, the internal configuration of the control device (robot controller), the robot, the first bit driving unit, and the second bit driving unit included in the screw tightening system will be described with reference to FIG. FIG. 8 is a functional block diagram of the screw tightening system. FIG. 8 shows an example of the internal configuration of each part described above, and shows only the components related to screw tightening.

  As shown in FIG. 8, the robot controller 80 as a control device includes a control unit 90. The control unit 90 includes an instruction unit 91, an acquisition unit 92, and a determination unit 93. The instruction unit 91 outputs a signal for operating the hand 71 and the arm units 72 to 76 of the robot 70 based on teaching information from a teaching unit (not shown).

  The instruction unit 91 outputs a drive signal to the motor (for example, servo motor) Ma of the first bit drive unit 11a. In the first bit drive unit 11a, when a drive signal is input, the motor Ma rotates. In the screw tightening system 1, for example, it is determined whether or not the output torque of the motor Ma has reached a set value. Therefore, a detection signal that informs the output torque of the motor Ma is input to the acquisition unit 92.

  The acquisition unit 92 outputs the detection signal to the determination unit 93. The determination unit 93 outputs a signal to the instruction unit 91 when the output torque of the motor Ma reaches a set value. When the signal from the determination unit 93 is input to the instruction unit 91, a stop signal is output to the motor Ma. As a result, the motor Ma stops, and the temporary tightening of the screw is completed.

  As shown in FIG. 8, the programmable controller 81 as a control device dedicated to the second bit drive unit includes an instruction unit 94, an acquisition unit 95, and a determination unit 96. Similarly, the nutrunner controller 82 as a control device dedicated to the second bit drive unit includes an instruction unit 97.

  In the programmable controller 81, the instruction unit 94 outputs a drive signal to the motor Mb of the second bit drive unit 11 b via the instruction unit 97 of the nutrunner controller 82. In the second bit drive unit 11b, when a drive signal is input, the motor Mb rotates. In the screw tightening system 1, when the torque detected by the torque detector TD reaches a specified torque, the final tightening of the screw is finished. Therefore, a detection signal informing the detected torque is output from the torque detector TD to the acquisition unit 95 of the programmable controller 81.

  The acquisition unit 95 outputs the detection signal to the determination unit 96. The determination unit 96 outputs a signal to the instruction unit 94 when the torque reaches the specified torque. When the signal from the determination unit 96 is input, the instruction unit 94 outputs an instruction signal to the instruction unit 97 of the nutrunner controller 82. When the instruction signal is input, the instruction unit 97 of the nutrunner controller 82 outputs a stop signal to the motor Mb.

  As a result, the motor Mb stops and the final tightening of the screw is completed. The instruction unit 94 of the programmable controller 81 outputs a signal notifying the end of the final tightening to the instruction unit 91 of the robot controller 80. Thereby, the robot 70 can move to the operation | movement of the next screw fastening operation | work, for example.

  According to the screw tightening system 1 according to the embodiment, since the robot 70 uses the first bit driving unit 11a having a high rotational speed for temporarily tightening the screws, the screws can be temporarily tightened at a high speed. As a result, the time required for screw tightening can be shortened. For example, when the output rotational speed is 3000 rpm, it takes 1 second / screw to tighten a screw having a pitch of 1 mm and a length of 50 mm, and the time required for tightening 30 screws is about 30 seconds.

  Further, according to the screw tightening system 1, the bit holding unit 18 is detachably attached to the first bit driving unit 11a or the second bit driving unit 11b, and the first bit driving unit 11a and the second bit driving unit 11b By sharing with each other, the number of parts can be reduced.

  Further, according to the screw tightening system 1, the robot controller 80 as a control device drives and controls the motor Ma of the first bit driving unit 11 a gripped by the hand 71 as an external shaft of the robot 70. Become.

  In the screw tightening system 1 described above, the robot 70 is a single-armed multi-joint robot, but is not limited thereto. The robot 70 may be a double arm robot. By using a dual-arm robot, for example, the first bit driving unit 11a is gripped by one arm and the second bit driving unit 11b is gripped by the other arm. Then, the screws can be temporarily tightened with one arm, and the final tightening can be performed with the other arm.

  As a result, the time required for switching from the first bit driving unit 11a to the second bit driving unit 11b can be eliminated, and the time required for screw tightening can be further shortened.

  From here, with reference to FIG. 9, the screw fastening method by a screw fastening system is demonstrated. FIG. 9 is a flowchart showing the procedure of the screw tightening method. The screw tightening method described below includes a screw temporary tightening step and a final tightening step.

  As shown in FIG. 9, first, the robot selects the first bit driving unit and holds the first bit driving unit with the hand (step S101). Next, the robot attaches the bit holding unit to the first bit driving unit held by the hand (step S102). Then, the temporary tightening of the screw is started (step S103).

  After the start of temporary fastening, it is determined whether or not the output torque of the motor Ma has reached a set value (step S104). If it is determined that the set value has been reached (step S104, Yes), the temporary tightening of the screw ends (step S105). If it is determined in step S104 that the set value has not been reached (No in step S104), step S104 is repeated until the set value is reached.

  As shown in FIG. 9, when the temporary tightening process of the screw is completed, the robot removes the bit holding unit from the first bit driving unit (step S106). Next, the robot releases the grip of the first bit drive unit gripped by the hand (step S107). Next, the robot selects the second bit driving unit and grips the second bit driving unit with the hand (step S108). That is, the robot switches from the first bit driving unit to the second bit driving unit.

  Next, the robot attaches the bit holding unit removed in step S106 to the second bit driving unit held by the hand (step S109). Then, the final tightening of the screw is started (step S110).

  After the start of the final tightening, it is determined whether or not the output value (screw tightening torque) from the torque detector TD has reached the specified torque (step S111). When it is determined that the specified torque has been reached (step S111, Yes), the final tightening of the screw is finished (step S112). Thereby, the final tightening process of the screw is completed. That is, the screw tightening operation is completed. If it is determined in step S111 that the specified torque has not been reached (No in step S111), step S111 is repeated until the specified torque is reached.

  According to the screw tightening method according to the embodiment, the robot performs temporary tightening of the screw by using the first bit driving unit that outputs a rotational driving force at a high rotational speed, and performs final tightening with a high torque (low rotational speed). This is performed using a second bit driving unit that outputs a rotational driving force. Thereby, the time required for temporary tightening can be significantly shortened, and the time required for screw tightening can be shortened. As a result, the tact time of the entire assembly process including the screw tightening process can be shortened.

  In addition, as a method other than the above-described screw tightening method, for example, when there are a plurality of screws, the robot temporarily tightens all the screws using the first bit driving unit and then the second bit driving unit. There is a method of holding and tightening all screws.

  Further, when the robot is a double-arm robot, the screw is temporarily tightened using the first bit driving unit held by one arm, and the second bit driving unit held by the other arm is used. There is also a method of performing final fastening. According to such a screw tightening method, the operation of switching from the first bit driving unit to the second bit driving unit can be omitted, and the time required for screw tightening can be further shortened.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 Screw fastening system 10 Screw fastening apparatus 11 Bit drive part 11a 1st bit drive part (air cylinder)
11b Second bit drive unit (air cylinder)
DESCRIPTION OF SYMBOLS 15 Output shaft 16 Torque transmission shaft 17 Attaching / detaching part 18 Bit holding part 20 Bit 22 Rotating part 23 Direct acting part 27 Pressing part (spring)
70 Robot 71 Hand 72 First Arm Part 73 Second Arm Part 74 Third Arm Part 75 Fourth Arm Part 76 Fifth Arm Part 80 Control Device (Robot Controller)
81 Control device (programmable controller) dedicated to the second bit drive unit
82 Dedicated control device for the 2nd bit drive unit (Nutrunner controller)
AX Shaft Ma Motor Mb Motor G Reducer TD Torque detector

Claims (8)

An articulated robot having a hand at the tip;
A control device for driving and controlling the robot;
A first bit driving unit that is selectively gripped by the hand and directly outputs a rotational driving force by a motor;
A second bit driving unit selectively gripped by the hand and outputting a rotational driving force by a motor via a speed reducer;
A bit holding unit that is attached to at least one of the first bit driving unit and the second bit driving unit and holds a bit that rotates about an axis by the input rotational driving force ;
A dedicated control device for driving and controlling the second bit driving unit;
A torque detector provided in the second bit driving unit for detecting a torque of a screw tightened or loosened by the second bit driving unit and outputting a value of the detected torque to the dedicated control device;
A screw tightening system characterized by further comprising: The bit holding unit is
The first bit driving unit or the second bit driving unit is detachably attached to the first bit driving unit or the second bit driving unit, and is shared between the first bit driving unit and the second bit driving unit. Screw tightening system. The bit holding unit is
A rotating unit that rotates the bit around an axis by the rotational driving force;
A linear motion portion that linearly moves the bit in the axial direction following external force;
The screw tightening system according to claim 1, further comprising: a pressing portion that presses the linear motion portion toward a tip side of the bit holding portion. The robot is
Using the first bit driving unit, temporarily tighten the screw,
The screw tightening system according to claim 1, wherein the screw that has been temporarily tightened using the second bit driving unit is tightened. The robot is
Holding the first bit driving unit by the hand and attaching the bit holding unit to the first bit driving unit to perform the temporary fastening,
The screw tightening system according to claim 4, wherein the second bit driving unit is gripped by the hand and the bit holding unit is attached to the second bit driving unit to perform the final tightening. The robot is
The screw tightening system according to claim 1, wherein the screw tightening system is a double-arm robot. The controller is
The screw tightening system according to any one of claims 1 to 6, wherein the motor of the first bit driving unit is driven and controlled as an external shaft of the robot. An articulated robot having a hand at the tip, a control device for driving and controlling the robot, a first bit driving unit that is selectively gripped by the hand and directly outputs a rotational driving force by a motor, and selected by the hand A second bit driving unit that is gripped and outputs a rotational driving force by a motor via a speed reducer, and is attached to the first bit driving unit or the second bit driving unit, and the input rotational driving force A bit holding unit that holds a bit that rotates about an axis, and is provided in the second bit driving unit and controlled by the second bit driving unit, and is tightened by the second bit driving unit. the first bit in the screw fastening system further comprises a torque detector for detecting a torque of the screw, and outputs a value of the detected torque to the dedicated control unit being A temporary tightening step of temporarily tighten the screw with moving parts,
And a final tightening step of final tightening the screw temporarily tightened using the second bit driving unit.

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