Screw tightening device

Abstract

In a screw tightening device (800), a rotary driving machine (130) rotates a bit (140). A bit cover (220) is formed in a cylindrical shape surrounding the bit (140). A slide shaft (210) is fixed to the bit cover (220). A guide member (150) slides in the axial direction along the slide shaft (210). The guide member (150) is fixed to the rotary driving machine (130). When tightening a screw, the position of the bit cover (220) relative to a workpiece (910) is defined in a state in which a front end surface (222a) of the bit cover (220) is in contact with the workpiece (910) or the end surface (222a) faces the workpiece (910) with a gap therebetween. The bit (140) and the screw (920) advance forward toward the workpiece (910) through the inside of the bit cover (220), the position of which relative to the workpiece (910) has been defined.

Description

Screw tightening device

[0001] The present disclosure relates to a screw tightening device.

[0002] As disclosed in Patent Document 1, a screw tightening device is known that includes a rod-shaped bit whose tip fits into the head of a screw and a rotary driver that rotates the bit. The rotary driver that rotates the bit is given a thrust force that moves it toward the workpiece. As a result, the bit moves toward the workpiece together with the rotary driver, thereby tightening the screw into the workpiece.

[0003] JP 2008-302482 A

[0004] Conventional screw tightening devices have room for improvement in terms of safety, since the screw is tightened in a state in which the bit and the screw are exposed to the outside.

[0005] An object of the present disclosure is to provide a screw tightening device that can improve safety when tightening screws compared to conventional devices.

[0006] The screw fastening device according to the present disclosure includes a rod-shaped bit, a rotary driver, a bit cover, a slide shaft, and a guide member. The tip of the bit fits into the head of the screw. The rotary driver rotates the bit about an imaginary central axis that extends in the length direction of the bit and passes through the bit. The rotary driver is moved toward a workpiece into which the screw is to be driven. The bit, which moves together with the rotary driver toward the workpiece, performs fastening by driving the screw into the workpiece. The bit cover extends in an axial direction parallel to the imaginary central axis and is formed in a cylindrical shape surrounding the bit. The slide shaft is fixed to the bit cover and extends in the axial direction. The guide member is fixed to the rotary driver. The guide member slides axially along the slide shaft while in contact with the slide shaft, thereby guiding axial movement of the rotary driver and the bit relative to the slide shaft and the bit cover. When tightening a screw, the position of the bit cover relative to the work is determined with the front end face of the bit cover, which is closest to the work in the axial direction, in contact with the work or with the end face facing the work with a gap, and the bit and screw move forward toward the work inside the bit cover whose position relative to the work is determined.

[0007] According to the above configuration, the bit cover can prevent the operator, other members, etc. from coming into contact with the bit when tightening a screw, thereby improving safety when tightening a screw compared to conventional methods.

[0008] FIG. 1 is a conceptual diagram showing the configuration of a screw fastening device according to a first embodiment;

[0009] Hereinafter, a screw fastening device according to an embodiment will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals.

[0010] [Embodiment 1] As shown in Figure 1, a screw tightening device 800 according to this embodiment includes a main body 710 that performs screw tightening by screwing a screw 920 into a workpiece 910, and a screw holder 720 that holds the screw 920 used for screw tightening.

[0011] The screw holder 720 holds a plurality of aligned screws 920. The screw holder 720 is placed beside the workpiece 910. The workpiece 910 and the screw holder 720 are placed on the surface of a table 930 (hereinafter referred to as the "placing surface").

[0012] The screw tightening device 800 also includes a robot 810 as an example of a moving device that moves the main body 710 , and a robot control device 820 that controls the robot 810 .

[0013] The robot 810 is a collaborative robot. In this specification, the term "collaborative robot" refers to a robot that can work in collaboration with humans. Specifically, the robot 810, which is a collaborative robot, performs work related to screw tightening in an area close to a worker. A safety fence surrounding the robot 810 is not required. The robot control device 820 causes the robot 810 to perform the following operations.

[0014] First, the robot 810 moves the position of the main body 710 in the in-plane direction of the mounting surface of the table 930 (hereinafter simply referred to as the in-plane position) to a position facing the screw holder 720. At that position, the main body 710 obtains the screw 920 held in the screw holder 720.

[0015] Next, the robot 810 moves the in-plane position of the main body 710 while holding the screw 920 to a position facing the workpiece 910. Next, the robot 810 moves the main body 710 closer to the workpiece 910 while maintaining the in-plane position of the main body 710.

[0016] As the main body 710 approaches the workpiece 910, it screws the screw 920 into the workpiece 910. The screw fastening device 800 according to this embodiment is most characterized by the configuration of the main body 710. The configuration of the main body 710 will now be described in detail.

[0017] 2 and 3 , the main body 710 includes a base member 300 fixed to the robot 810, a connectable member 100 connected to the base member 300, and a relative displacement member 200 that is displaceable relative to the connectable member 100. In this embodiment, the connectable member 100 is fixed to the base member 300.

[0018] The connected member 100 has a bracket 110 fixed to the base member 300, a rotary drive holding member 120 fixed to the bracket 110, a rotary drive 130 held by the rotary drive holding member 120, and a rod-shaped bit 140 held by the rotary drive 130.

[0019] A tip 141 of the rod-shaped bit 140 is fitted into the head 921 of the screw 920 shown in Fig. 1. A rear end of the rod-shaped bit 140 opposite to the tip 141 in the length direction is held by the rotary driver 130.

[0020] To facilitate the following description, an imaginary central axis VL is defined that extends in the length direction of the rod-shaped bit 140 and passes through the bit 140. The rotary driver 130 rotates the bit 140 about the imaginary central axis VL.

[0021] Hereinafter, the direction parallel to the imaginary central axis VL is also referred to as the “axial direction.” Furthermore, with respect to the axial direction, the direction away from the workpiece 910 shown in FIG. 1 is defined as the “rearward direction,” and the direction toward the workpiece 910 shown in FIG. 1 is defined as the “forward direction.”

[0022] In this embodiment, when tightening the screw, the axial direction coincides with the vertical direction, the rear coincides with the vertically upward direction, and the front coincides with the vertically downward direction.

[0023] The rotary driver 130 is moved forward by the robot 810 toward the workpiece 910 shown in Fig. 1 while rotating the bit 140 engaged with the screw 920 shown in Fig. 1. Then, the bit 140, which moves forward together with the rotary driver 130 toward the workpiece 910, performs screw tightening by screwing the screw 920 into the workpiece 910.

[0024] The connected member 100 also has a guide member 150 that guides the axial displacement of the relative displacement member 200 relative to the connected member 100. The guide member 150 is formed in a tubular shape that extends in the axial direction. The guide member 150 that extends in the axial direction is fixed to the rotary driver holding member 120.

[0025] The connected member 100 according to this embodiment includes a pair of guide members 150 each extending in the axial direction. The pair of guide members 150 are disposed opposite each other with the rotary driver 130 interposed therebetween.

[0026] For ease of understanding, a right-handed XYZ Cartesian coordinate system is defined in which the direction in which the pair of guide members 150 face each other is the X-axis direction and the axial direction is the Z-axis direction. The front is the positive direction of the Z-axis and the rear is the negative direction of the Z-axis.

[0027] On the other hand, the relative displacement member 200 has a slide shaft 210 inserted through each guide member 150, a bit cover 220 fixed to the front end of the slide shaft 210, and a stopper 230 provided at the rear end of the slide shaft 210.

[0028] The slide shaft 210 extends in the axial direction like a rod. The slide shaft 210 and the guide member 150 through which the slide shaft 210 is inserted are slidable relative to each other in the axial direction. This allows the relative displacement of the relative displacement member 200 with respect to the connected member 100 in the axial direction.

[0029] Specifically, the guide member 150 can slide in the axial direction along the slide shaft 210 while in contact with the slide shaft 210 that is inserted through the guide member 150. As described above, the slide shaft 210 is fixed to the bit cover 220, and the guide member 150 is fixed to the rotary driver 130. Therefore, by sliding along the slide shaft 210, the guide member 150 serves to guide the axial movement of the rotary driver 130 and the bit 140 relative to the slide shaft 210 and the bit cover 220.

[0030] 2 illustrates a configuration in which the screw fastening device 800 includes two pairs of slide shafts 210 and guide members 150 slidably connected to the slide shafts 210. The screw fastening device 800 may include three or more pairs of slide shafts 210 and guide members 150, or may include only one pair.

[0031] However, providing multiple pairs of slide shafts 210 and guide members 150 on the main body 710 can improve the accuracy of the axial relative displacement of the relative displacement member 200 with respect to the connected member 100 compared to when there is only one pair of slide shafts 210 and guide members 150.

[0032] The stopper 230 limits the amount of forward relative displacement of the relative displacement member 200 with respect to the connected member 100. In other words, when the relative displacement member 200 moves forward with respect to the connected member 100 and the axial distance between the bit cover 220 and the rotary driver holding member 120 reaches a maximum limit distance that is less than the axial length of the slide shaft 210, the stopper 230 comes into contact with the rear end face of the guide member 150. This prevents the relative displacement member 200 with respect to the connected member 100 from further moving forward.

[0033] In this embodiment, as described above, the axial direction coincides with the vertical direction during screw tightening. Therefore, in a state where the entire load of the relative displacement member 200 acts on the robot 810 through the connected member 100 (hereinafter referred to as the natural state), the entire load of the relative displacement member 200 acts on the guide member 150 through the stopper 230. In other words, the guide member 150 plays a role in supporting the relative displacement member 200 in the natural state. Note that Figures 2 and 3 show the natural state.

[0034] The bit cover 220 has a base end 221 and an extension 222 that extends forward from the base end 221. Both the base end 221 and the extension 222 extend in the axial direction and are formed in a tubular shape, specifically a cylindrical shape, that surrounds the bit 140.

[0035] However, the base end 221 is formed in a cylindrical shape with a larger diameter than the extending portion 222. The base end 221 has a step plate 221a that faces the table 930 or the workpiece 910 shown in Fig. 1. The extending portion 222 extends forward from the step plate 221a.

[0036] The base end portion 221 surrounds not only the bit 140 but also the pair of slide shafts 210 that are arranged opposite each other in the X-axis direction with the rotary driver 130 interposed therebetween. On the other hand, the extension portion 222 surrounds only the bit 140 out of the bit 140 and the pair of slide shafts 210.

[0037] The base end portion 221 is fixed to the front ends of the pair of slide shafts 210. Specifically, the front ends of the pair of slide shafts 210 are fixed to the inner surface of the step plate 221 a at the base end portion 221, which faces the rotary drive machine holding member 120.

[0038] 4 and 5 show the external appearance of the main body 710. Although the inside of the bit cover 220 is shown in FIGS. 2 and 3, the bit 140 shown in FIGS. 2 and 3 is covered and hidden by the bit cover 220 shown in FIGS. 4 and 5.

[0039] Therefore, at the site where the screw is being tightened, the bit cover 220 prevents workers, other members, etc. from unintentionally coming into contact with the bit 140. Here, "other members" refers to members other than the bit 140 (however, excluding the screw 920 and bit cover 220 fitted into the bit 140).

[0040] Next, with reference to FIG. 6, the function of the main body 710 during screw tightening will be described.

[0041] 1 is already obtained by the bit 140 from the screw holder 720 shown in FIG. 1. That is, the bit 140 holds the screw 920 with the tip 141 fitted into the head 921 of the screw 920.

[0042] In this embodiment, when the bit 140 acquires the screw 920 and when the bit 140 holds the screw 920, the tip 141 of the bit 140 and the head 921 of the screw 920 are attached to each other by magnetic force. That is, the screw 920, which is a ferromagnetic material, is attached to the bit 140, which has been magnetized by an electromagnet (not shown), by magnetic force.

[0043] Also, it is assumed that the main body 710 has been moved by the robot 810 to a position (hereinafter referred to as the screw tightening position) facing the workpiece 910. When the in-plane position of the main body 710 is set to the screw tightening position, the screw 920 held by the bit 140 faces a screw hole (not shown) formed in the workpiece 910.

[0044] The robot 810 moves the main body 710, which is in the natural state described above, in the axial direction at the screw tightening execution position toward the workpiece 910. In the natural state, not only the bit 140 but also the entire length of the screw 920 is covered and hidden by the bit cover 220.

[0045] When the main body 710 in its natural state is brought close to the workpiece 910 and the front end surface 222a of the bit cover 220 comes into contact with the workpiece 910, the position of the bit cover 220 relative to the workpiece 910 is determined. Thereafter, until the screw tightening is completed, the positional relationship between the bit cover 220 and the workpiece 910 is maintained with the front end surface 222a of the bit cover 220 in contact with the workpiece 910.

[0046] Even after the position of the bit cover 220 relative to the workpiece 910 has been determined, the connected member 100, including the bit 140 and the rotary driver 130, is moved forward toward the workpiece 910. At this time, the bit 140 holding the screw 920 is rotated by the rotary driver 130. In this manner, the screw 920 rotated by the bit 140 is screwed into the workpiece 910.

[0047] When the position of the bit cover 220 relative to the workpiece 910 is determined, the bit cover 220 can be displaced rearward relative to the connected member 100 including the bit 140 and the rotary driver 130 .

[0048] Therefore, after the position of the bit cover 220 relative to the workpiece 910 is determined, the fixing member 110 moves forward relative to the bit cover 220. In other words, during screw tightening, the bit 140 and the screw 920 move forward toward the workpiece 910 inside the bit cover 220 whose position relative to the workpiece 910 has been determined.

[0049] The connected member 100 moving forward by a distance L1 relative to the workpiece 910, i.e., the bit 140 and screw 920 moving forward by a distance L1 inside the bit cover 220, is equivalent to the bit cover 220, whose position relative to the workpiece 910 is determined, being displaced backward by a distance L1 relative to the connected member 100.

[0050] In this embodiment, while the screw 920 is being screwed into the workpiece 910, the load of the relative displacement member 200 including the bit cover 220 acts on the workpiece 910 through the end surface 222 a of the bit cover 220. In other words, the workpiece 910 supports the relative displacement member 200 including the bit cover 220.

[0051] When the screw 920 is screwed into the workpiece 910 by a predetermined amount, the screw tightening is completed. Note that Fig. 6 illustrates an example in which the predetermined amount of screwing is L1 + L2. When the screw tightening is completed, the robot 810 moves the main body 710 away from the position facing the workpiece 910 into which the screw has been tightened.

[0052] As described above, according to this embodiment, a screw can be tightened with the end surface 222a of the bit cover 220 in contact with the workpiece 910. In other words, the screw can be tightened with the bit 140 and the screw 920 covered by the bit cover 220. Therefore, when tightening the screw, the bit cover 220 can serve to prevent the worker, other members, and the like from coming into contact with the bit 140 and the screw 920. This makes it possible to improve safety when tightening the screw compared to conventional methods.

[0053] 2 and 3 show an example of a configuration in which the connected member 100 is directly fixed to the base member 300. A mechanism that allows the connected member 100 to move rearward relative to the base member 300 may be interposed between the base member 300 and the connected member 100. Specific examples of this mechanism will be described below.

[0054] As shown in FIG. 7, the main body 710 according to this embodiment further includes a connecting mechanism 410 that connects the base member 300 and the connected member 100 together.

[0055] 8 , the connecting mechanism 410 is interposed between the base member 300 and the rotary drive unit holding member 120 to which the rotary drive unit 130 is fixed, and connects the base member 300 and the rotary drive unit holding member 120. During screw tightening, the robot 810 moves the connected member 100 and the relative displacement member 200 toward the workpiece 910 via the base member 300 and the connecting mechanism 410.

[0056] The connecting mechanism 410 has a guide member 411 fixed to the base member 300 and a slider 412 fixed to the rotary drive device holding member 120. The guide member 411 extends in the axial direction and stands upright from the base member 300.

[0057] The connecting mechanism 410 connects the base member 300 and the connected member 100 in a state where the connected member 100 is allowed to move rearward relative to the base member 300. Specifically, the guide member 411 holds the slider 412 so that it can slide freely in the axial direction.

[0058] However, when no rearward resistance is acting on the connected member 100, the entire load of the connected member 100 acts on the base member 300 through the slider 412. At this time, due to this entire load, the slider 412 remains at the front end of the guide member 411. Furthermore, when the relative displacement member 200 is in the natural state described above, the load of the relative displacement member 200 also acts on the base member 300 through the slider 412.

[0059] Even if a rearward resistance force is acting on the connected member 100, if the magnitude of the resistance force is less than a predetermined value, the slider 412 remains at the front end of the guide member 411. In this embodiment, normal screw tightening is performed in a state in which the slider 412 remains at the front end of the guide member 411, that is, in a state in which the connected member 100 is kept immovable in the axial direction relative to the base member 300.

[0060] On the other hand, when a rearward resistance force of a predetermined value or greater acts on the connected member 100, specifically when a rearward resistance force of a predetermined value or greater acts on the rotary driver 130 through the bit 140, the connected member 100 is displaced rearward relative to the base member 300 through the connecting mechanism 410. In other words, the slider 412 slides rearward along the guide member 411.

[0061] In this embodiment, the axial direction coincides with the vertical direction when the screw is tightened. Therefore, when the load of the relative displacement member 200 is not acting on the connected member 100, the above-mentioned "resistance force of a magnitude equal to or greater than a predetermined value" in this embodiment means a resistance force of a magnitude equal to or greater than the total load of the connected member 100.

[0062] The main body 710 according to this embodiment also includes a rear relative displacement sensor 420 that detects the rearward relative displacement of the connected member 100 with respect to the base member 300 (hereinafter referred to as rearward relative displacement).

[0063] The rear relative displacement sensor 420 has a first sensor part 421 fixed to the slider 412 and a second sensor part 422 fixed to the base member 300. As the connected member 100 undergoes a relative rear displacement, the first sensor part 421 is displaced rearward relative to the second sensor part 422, so that the rear relative displacement of the connected member 100 can be detected.

[0064] As shown in FIG. 9 , the main body 710 according to this embodiment also includes a movement stop control unit 430 that acquires the detection result from the rear relative displacement sensor 420 .

[0065] The operation of the main body 710 according to this embodiment will be described below using as an example a case where an obstacle 940 that prevents normal screw tightening is placed on the workpiece 910.

[0066] When the obstacle 940 is placed on the workpiece 910, the bit cover 220 and the screw 920, which are moved forward by the robot 810 toward the workpiece 910, come into contact with the obstacle 940. When the robot 810 attempts to move the bit cover 220 and the screw 920 further forward, the bit cover 220 is supported by the obstacle 940, and the connected member 100 is also supported by the obstacle 940 via the screw 920.

[0067] As a result, as the robot 810 moves the base member 300 forward, the connected member 100 is displaced rearward relative to the base member 300 through the connecting mechanism 410. Then, the rearward relative displacement of the connected member 100 with respect to the base member 300 is detected by the rearward relative displacement sensor 420.

[0068] The movement stop control unit 430 causes the robot 810 to stop the movement of the main body 710 when the rear relative displacement sensor 420 detects a rear relative displacement of the connected member 100 .

[0069] If the connecting mechanism 410 is not provided and the connected member 100 is fixed to the base member 300, the action of the robot 810 moving the main body 710 forward may cause a thrust force to act on the obstacle 940 that exceeds the total load of the connected member 100 and the relative displacement member 200.

[0070] In contrast, according to this embodiment, when a rearward resistance equal to or greater than a predetermined value acts on the connected member 100, the connecting mechanism 410 allows the connected member 100 to move rearward relative to the base member 300. Furthermore, when the connected member 100 moves rearward relative to the base member 300, the movement stop control unit 430 stops the movement of the main body 710.

[0071] This prevents a thrust force exceeding the total load of the connected member 100 and the relative displacement member 200 from acting on the obstacle 940. This not only contributes to further improving safety during screw tightening, but also contributes to preventing failure of the main body 710.

[0072] 8 and 9 illustrate a configuration in which the connected member 100 is displaced rearward relative to the base member 300 when the magnitude of the rearward resistance acting on the connected member 100 reaches or exceeds a value equal to the total load of the connected member 100. That is, Figures 8 and 9 illustrate a configuration in which the predetermined value is equal to the total load of the connected member 100.

[0073] However, the predetermined value is not limited to the total load of the connected member 100. As an example, the predetermined value may be a value greater than the total load of the connected member 100. Specifically, a magnetic coupler that magnetically couples the slider 412 and the base member 300 in the axial direction may be added to the configuration shown in Figures 8 and 9. In that case, the predetermined value is determined as the sum of the total load of the connected member 100 and the magnetic coupling force between the slider 412 and the base member 300.

[0074] When one of the north and south poles is defined as the first pole and the other as the second pole, the magnetic coupler has a first pole fixed to the slider and a second pole fixed to the base member 300. The first pole and the second pole are magnetically coupled in the axial direction. The magnet of the first pole may be attached to the slider 412, or if the slider 412 is made of a magnetic material, the slider 412 may be magnetized. The magnet of the second pole may be attached to the base member 300, or if the base member 300 is made of a magnetic material, the base member 300 may be magnetized.

[0075] [Embodiment 3] A device for suppressing the rearward relative displacement of the connected member 100 with respect to the base member 300 may be added to the configuration according to the above-described embodiment 2. A specific example thereof will be described below.

[0076] 10 , the main body 710 according to the present embodiment further includes a pressing device 510 in addition to the configuration according to the second embodiment. The pressing device 510 is fixed to the base member 300. The pressing device 510 suppresses the rearward relative displacement of the connected member 100 by pressing the connected member 100 forward.

[0077] The pressing device 510 has a feeding device 511 fixed to the base member 300 and a feeding rod member 512 that is fed forward from the feeding device 511 by the feeding device 511 .

[0078] The feeding device 511 is disposed rearward of the rear end of the guide member 411. An axially extending feeding rod member 512 extends forward from the feeding device 511. The front end of the feeding rod member 512 abuts against the slider 412. The feeding device 511 feeds the feeding rod member 512 forward.

[0079] As a result, a forward pressing force is applied to the connected member 100 including the rotary driver 130 through the slider 412 by the feeding rod member 512, whose front end is in contact with the slider 412. At that time, a backward reaction force of the same magnitude as the pressing force acts on the base member 300 through the feeding device 511.

[0080] The payout device 511 can be switched between (a) a pressing state in which a pressing force is applied to the connected member 100, and (b) a non-pressing state in which the application of the pressing force to the connected member 100 is released.

[0081] In the pressed state, a backward reaction force acts on the base member 300, and a forward pressing force of the same magnitude as the reaction force is applied to the connected member 100 through the payout rod member 512. In the non-pressed state, the payout of the payout rod member 512 is stopped.

[0082] In the non-pressed state, the feeding rod member 512, whose front end is in contact with the slider 412, is free to slide rearward together with the slider 412. At this time, the feeding device 511 receives the feeding rod member 512 that has slid rearward.

[0083] The main body 710 according to this embodiment also includes a pressing control device 520 that controls the feeding device 511. The pressing control device 520 switches the feeding device 511 between a pressing state and a non-pressing state.

[0084] When the connected member 100 and the relative displacement member 200 are moved forward toward the workpiece 910 to perform screw tightening, the pressing control device 520 takes into consideration the possibility that the aforementioned obstacle 940 may be present, and controls the payout device 511 to a non-pressing state.

[0085] Therefore, even if an obstacle 940 is present, the same effect as in embodiment 2 can be obtained, in that a thrust force exceeding the total load of the connected member 100 and the relative displacement member 200 is prevented from acting on the obstacle 940.

[0086] On the other hand, the pressing control device 520 switches the feeding device 511 to the pressing state while the screw is being tightened normally. Therefore, the screw can be tightened while the relative rearward displacement of the connected member 100 is suppressed by the pressing force.

[0087] [Embodiment 4] A device for gripping the screw 920 in a state where the head 921 is fitted with the tip 141 of the bit 140 may be added to the configuration according to any one of the above-mentioned embodiments 1 to 3. A specific example thereof will be described below.

[0088] 11 , the main body 710 according to this embodiment further includes a screw gripping device 600 in addition to the configuration according to embodiment 1. The screw gripping device 600 grips the screw 920 in a state in which the head 921 is fitted with the tip 141 of the bit 140.

[0089] In this embodiment, a first opening 223 and a second opening 224 are formed in the extension 222 of the bit cover 220. The first opening 223 and the second opening 224 face each other in a direction perpendicular to the axial direction (hereinafter referred to as the perpendicular direction).

[0090] The screw gripping device 600 has a first claw member 611 and a second claw member 612, each of which has a fixed axial position relative to the extension portion 222 of the bit cover 220. The axial positions of the first claw member 611 and the second claw member 612 relative to the extension portion 222 of the bit cover 220 are equal to the axial positions of the first opening 223 and the second opening 224. The first claw member 611 and the second claw member 612 face each other in the perpendicular direction.

[0091] The screw gripping device 600 also has a gripping mechanism 620 that displaces each of the first claw member 611 and the second claw member 612 in the perpendicular direction relative to the extension portion 222 of the bit cover 220. The gripping mechanism 620 is switchable between (A) an open state in which the first claw member 611 and the second claw member 612 are separated from each other, and (B) a screw gripping state in which the first claw member 611 and the second claw member 612 are brought closer to each other in the perpendicular direction.

[0092] Specifically, the open state is a state in which the first claw member 611 is positioned at a first retracted position facing the first opening 223 outside the extension portion 222, and the second claw member 612 is positioned at a second retracted position facing the second opening 224 outside the extension portion 222. Note that Fig. 11 shows the gripping mechanism 620 in the open state.

[0093] Specifically, the screw gripping state is a state in which the first claw member 611 in the first retracted position is pressed against the exposed portion of the screw 920 at the position of the first opening 223, whose head 921 is engaged with the tip 141 of the bit 140, and the second claw member 612 in the second retracted position is pressed against the exposed portion of the screw 920 at the position of the second opening 224.

[0094] As shown in FIG. 12 , in the screw gripping state, specifically, the body portion 922 adjacent to the head portion 921 of the screw 920 is gripped by the screw gripping device 600 .

[0095] The screw gripping device 600 according to this embodiment also includes a gripping control device 630 that controls the gripping mechanism 620. The gripping control device 630 switches the gripping mechanism 620 between an open state and a screw gripping state.

[0096] 1, when the head 921 of the screw 920 is engaged with the tip 141 of the bit 140, the gripping control device 630 switches the gripping mechanism 620 from the open state to the screw gripping state. Thereafter, the screw gripping state is maintained until the screw tightening starts. This prevents the screw 920 from falling out of the bit 140 while the bit 140 is moving after having acquired the screw 920.

[0097] 11 shows an example of a configuration in which a screw gripping device 600 is added to the configuration according to embodiment 1. The screw gripping device 600 according to this embodiment is applicable not only to embodiment 1, but also to the configurations according to embodiments 2 and 3.

[0098] Fifth Embodiment A sensor for measuring the amount of screwing of the screw 920 into the workpiece 910 may be added to the configuration according to any one of the first to fourth embodiments. A specific example will be described below.

[0099] 13 , the main body 710 according to this embodiment further includes a forward movement amount sensor 730 in addition to the configuration according to embodiment 1. The forward movement amount sensor 730 measures the relative axial displacement of the connected member 100 with respect to the bit cover 220.

[0100] Specifically, the forward movement amount sensor 730 is configured with a laser displacement meter. The forward movement amount sensor 730 is fixed to the rotary drive device holding member 120. The forward movement amount sensor 730 measures the distance from the forward movement amount sensor 730 to the inner surface of the step plate 221a using a distance measurement laser beam LB. The amount of change in this distance is equal to the amount of relative axial displacement of the connected member 100 with respect to the bit cover 220.

[0101] Therefore, in this embodiment, the measurement result of the forward movement amount sensor 730 when the position of the bit cover 220 relative to the workpiece 910 is determined at the start of screw tightening is used as the reference value. In this case, at a timing such as during screw tightening or at the completion of screw tightening, the measurement result of the forward movement amount sensor 730 at that timing can be determined by subtracting the known reference value described above.

[0102] In the above manner, the forward movement amount sensor 730 according to this embodiment measures the amount of forward movement of the connected member 100 including the rotary drive 130 and the bit 140 relative to the bit cover 220, whose position relative to the workpiece 910 is determined, during screw tightening, i.e., the amount of screwing of the screw 920 into the workpiece 910.

[0103] The length of the screw 920 used for screw tightening, excluding the head 921, or the correct amount of screwing in of the screw 920 is known. Therefore, by measuring the actual amount of screwing in of the screw 920 using the measurement result of the forward movement amount sensor 730, it is possible to determine whether or not the screw tightening has been completed normally.

[0104] 13 illustrates an example of a configuration in which a front movement amount sensor 730 is added to the configuration according to embodiment 1. The front movement amount sensor 730 according to this embodiment is applicable not only to embodiment 1 but also to any of the configurations according to embodiments 2 to 4.

[0105] 6 illustrates an example of a configuration in which the load of the relative displacement member 200 including the bit cover 220 acts directly on the workpiece 910 during screw tightening. The relative displacement member 200 including the bit cover 220 may be supported by a member other than the workpiece 910. A specific example of this will be described below.

[0106] 14, the main body 710 according to this embodiment further includes a support member 740 in addition to the configuration according to embodiment 1. The support member 740 is disposed in a fixed state relative to the workpiece 910 prior to screw tightening.

[0107] Specifically, the support member 740 is disposed at a position beside the workpiece 910 on the mounting surface of the table 930. The support member 740 has a support surface 741 that is located behind the surface of the workpiece 910 when the support member 740 is mounted on the table 930 and fixed to the workpiece 910.

[0108] In this embodiment, when the screw is tightened, the outer surface of the step plate 221 a of the bit cover 220 that faces the workpiece 910 comes into contact with the support surface 741. This determines the position of the bit cover 220 relative to the workpiece 910 in a state in which the relative displacement member 200 including the bit cover 220 is supported by the support member 740.

[0109] In this embodiment, the outer surface of the step plate 221 a is an example of a stopper surface that faces the support surface 741 .

[0110] In this embodiment, when the position of the bit cover 220 relative to the workpiece 910 is determined, a gap GP is secured between the end surface 222 a of the bit cover 220 and the surface of the workpiece 910. The axial dimension of the gap GP is small enough to prevent a person's fingers from entering the inside of the bit cover 220.

[0111] Therefore, although the screw can be tightened while keeping the bit cover 220 out of contact with the workpiece 910, the effect is that, as in the case of embodiment 1, safety during screw tightening can be improved compared to conventional methods.

[0112] The end surface 222a of the bit cover 220 supported by the support member 740 may be in contact with the surface of the workpiece 910. In this case, safety during screw tightening is further improved. Even in this case, at least a portion of the total load of the relative displacement member 200 can be applied to the support member 740, so that screw tightening can be performed without the total load of the relative displacement member 200 being applied to the workpiece 910.

[0113] The support member 740 according to this embodiment can be applied to any of the configurations of the first to fifth embodiments.

[0114] 14 illustrates an example of a configuration in which the relative displacement member 200 including the bit cover 220 is supported by a support member 740 during screw tightening. Instead of employing the support member 740, a configuration may be adopted in which the load of the relative displacement member 200 including the bit cover 220 acts on the connected member 100 during screw tightening. A specific example of this is described below.

[0115] 15 and 16 show the configuration of a main body 710 according to this embodiment. The main body 710 according to this embodiment includes a bit cover retraction device 750 that connects the connected member 100 and the relative displacement member 200, instead of the support member 740 shown in FIG.

[0116] During screw tightening, the bit cover retraction device 750 moves the relative displacement member 200 rearward relative to the connected member 100 in such a manner that the load of the relative displacement member 200 acts on the robot 810 through the connected member 100 and the base member 300. The configuration of the bit cover retraction device 750 will be described in detail below.

[0117] The bit cover retraction device 750 has a cylinder portion 751 as a first fixed portion fixed to the rotary drive machine 130 and a rod portion 752 as a second fixed portion fixed to the bit cover 220 .

[0118] Specifically, the cylinder portion 751 is fixed to the rotary driver holding member 120. The rod portion 752 is housed in the base end portion 221 of the bit cover 220, which is located in front of the rotary driver holding member 120. The rod portion 752 is formed in a bar shape extending in the axial direction. The front end portion of the rod portion 752 is fixed to a step plate 221 a at the base end portion 221 that faces the rotary driver holding member 120.

[0119] On the other hand, the rear end of the rod portion 752 is housed in the cylinder portion 751. The rod portion 752 can enter the cylinder portion 751. Specifically, the bit cover retraction device 750 also has an actuator 753 that causes the rod portion 752 to enter the cylinder portion 751.

[0120] The actuator 753 is built into the cylinder portion 751. When the actuator 753 causes the rod portion 752 to enter the cylinder portion 751, the bit cover 220 moves rearward relative to the rotary driver 130. In other words, the actuator 753 is an example of a retraction mechanism that moves the second fixed portion fixed to the bit cover 220 rearward relative to the first fixed portion fixed to the rotary driver 130.

[0121] The actuator 753 can also advance the rod portion 752 from the cylinder portion 751. When the actuator 753 advances the rod portion 752 from the cylinder portion 751, the bit cover 220 moves forward relative to the rotary driver 130. In other words, the rod portion 752 can advance and retreat in the axial direction relative to the cylinder portion 751.

[0122] The bit cover retraction device 750 also has an actuator control unit 754 that controls the actuator 753. The actuator control unit 754 is an example of a retraction mechanism control unit that controls the retraction mechanism.

[0123] 17 , the control performed by the actuator control unit 754 will be described. During screw tightening, the actuator control unit 754 causes the rod portion 752 to enter the cylinder portion 751 as the rotary driver 130, the bit 140, and the screw 920 move forward toward the workpiece 910. In other words, the actuator control unit 754 moves the bit cover 220 rearward relative to the rotary driver 130 as the screw tightening progresses.

[0124] As a result, in the present embodiment as well, as in the sixth embodiment, the axial position of the bit cover 220 with respect to the workpiece 910 is determined in a manner that prevents the entire load of the relative displacement member 200, including the bit cover 220, from acting on the workpiece 910 during screw tightening. Specifically, in the present embodiment, a gap G is secured between the bit cover 220 and the workpiece 910 during screw tightening. In other words, the bit cover 220 is kept out of contact with the workpiece 910.

[0125] 15 and 16 , the bit cover retraction device 750 also has a distance sensor 755 fixed to the bit cover 220. The distance sensor 755 measures the axial distance between the distance sensor 755 and the workpiece 910 using a distance measurement laser beam LB.

[0126] Specifically, the distance sensor 755 is fixed to the step plate 221 a of the base end portion 221. Therefore, in this embodiment, the distance measured by the distance sensor 755 is equal to the distance between the step plate 221 a and the workpiece 910 facing the step plate 221 a.

[0127] Then, based on the measurement result of the distance sensor 755, the actuator control unit 754 controls the amount of rearward movement of the rod portion 752 relative to the cylinder portion 751 by the actuator 753, i.e., the amount of advancement of the rod portion 752 into the cylinder portion 751. In this way, the actuator control unit 754 suppresses changes in the axial distance between the distance sensor 755 and the workpiece 910 during screw tightening.

[0128] As described above, in this embodiment, the gap G is secured between the bit cover 220 and the workpiece 910. Suppressing the change in the axial distance between the distance sensor 755 fixed to the bit cover 220 and the workpiece 910 is equivalent to suppressing the change in the gap G between the bit cover 220 and the workpiece 910.

[0129] Specifically, the actuator control unit 754 performs control to maintain the axial distance between the distance sensor 755 and the workpiece 910 at a predetermined reference distance. In this embodiment, this reference distance is determined as the sum of the axial length of the extension portion 222 and the axial dimension of the gap G. The axial dimension of the gap GP is set to a value small enough to prevent a person's fingers from entering the inside of the bit cover 220.

[0130] As an example, when the axial distance between the distance sensor 755 and the workpiece 910 decreases by ΔL in a short period of time as the rotary driver 130, the bit 140, and the screw 920 move forward toward the workpiece 910, the actuator control unit 754 pulls the bit cover 220 rearward by the distance ΔL. In other words, the rod portion 752 advances by the distance ΔL into the cylinder portion 751. In this way, the change in the gap G is suppressed.

[0131] 17 illustrates a situation in which the rotary driver 130, bit 140, and screw 920 move a distance L toward the workpiece 910 from the start to the end of screw tightening. The total amount that the bit cover 220 is pulled rearward from the start to the end of screw tightening is also equal to the distance L. Therefore, the same gap G as at the start of screw tightening is maintained not only during screw tightening but also at the end of screw tightening.

[0132] After the screw has been tightened, the actuator control section 754 again advances the rod section 752 forward from the cylinder section 751 by the distance L to prepare for the next screw tightening.

[0133] In this embodiment, as in embodiment 6, the effect is achieved in that screws can be tightened while keeping the bit cover 220 out of contact with the workpiece 910, yet safety during screw tightening can be improved compared to conventional methods.

[0134] 15 to 17 show an example of a configuration in which a gap G is maintained between the bit cover 220 and the workpiece 910 during screw tightening. During screw tightening, the end surface 222 a of the bit cover 220 may be in contact with the surface of the workpiece 910 while the load of the relative displacement member 200 including the bit cover 220 acts on the connected member 100 and the base member 300 through the bit cover retraction device 750.

[0135] In this case, safety during screw tightening is further improved. Even in this case, at least a portion of the total load of the relative displacement member 200 can be applied to the connected member 100 and the base member 300, so screw tightening can be performed without the total load of the relative displacement member 200 being applied to the workpiece 910.

[0136] The bit cover retraction device 750 according to the present embodiment described above can be applied to any of the configurations of the first to fifth embodiments.

[0137] The above has described the first to seventh embodiments. The following modifications are also possible.

[0138] In the first to seventh embodiments, a configuration has been shown in which the axial direction during screw tightening coincides with the vertical direction, the rear coincides with the vertically upward direction, and the front coincides with the vertically downward direction. A configuration in which the rear coincides with the vertically downward direction and the front coincides with the vertically upward direction may also be adopted. Furthermore, the axial direction during screw tightening may be inclined relative to the vertical direction or horizontal.

[0139] By using the screw gripping device 600 according to embodiment 4, the screw 920 can be gripped, so that the screw 920 is less likely to fall off the bit 140 even if the axial direction during screw tightening is inclined relative to the vertical direction or horizontal.

[0140] The material of the bit cover 220 is not particularly limited. The bit cover 220 may be formed from resin or metal. At least the extension portion 222 of the bit cover 220 may be formed from a material that is transparent to visible light. This allows the degree of penetration of the screw 920 into the workpiece 910 to be visually confirmed from the outside.

[0141] The present disclosure allows various embodiments and modifications without departing from the broad spirit and scope of the present disclosure. The above-described embodiments are intended to explain the present disclosure and do not limit the scope of the present disclosure. The scope of the present disclosure is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of the disclosure equivalent thereto are considered to be within the scope of the present disclosure.

[0142] This application is based on Japanese Patent Application No. 2023-116280, filed on July 14, 2023. The entire specification, claims, and drawings of Japanese Patent Application No. 2023-116280 are incorporated herein by reference.

[0143] 100 Connected member, 110 Bracket, 120 Rotary drive machine holding member, 130 Rotary drive machine, 140 Bit, 141 Tip, 150 Guide member, 200 Relative displacement member, 210 Slide shaft, 220 Bit cover, 221 Base end, 221a Step plate (stopper surface), 222 Extension portion, 222a End surface, 223 First opening, 224 Second opening, 230 Stopper, 300 Base member, 410 Connecting mechanism, 411 Guide member, 412 Slider, 420 Rear relative displacement sensor, 421 First sensor portion, 422 Second sensor portion, 430 Movement stop control unit, 510 Pressing device, 511 Feeding device, 512 Feeding rod member, 520 Pressing control device, 600 Screw gripping device, 611 First claw member, 612 Second claw member, 620 gripping mechanism, 630 gripping control device, 710 main body portion, 720 screw holder, 730 forward movement amount sensor, 740 support member, 741 support surface, 750 bit cover retraction device, 751 cylinder portion (first fixed portion), 752 rod portion (second fixed portion), 753 actuator (retraction mechanism), 754 actuator control portion (retraction mechanism control portion), 755 distance sensor, 800 screw tightening device, 810 robot (movement device), 820 robot control device, 910 workpiece, 920 screw, 921 head portion, 922 body portion, 930 table, 940 obstacle, GP gap, LB distance measurement laser light, VL virtual central axis.

Claims

1. A screw tightening device comprising: a rod-shaped bit whose tip fits into the head of a screw; and a rotary driver which rotates the bit around an imaginary central axis which extends in the length direction of the bit and passes through the bit, the rotary driver being moved toward a workpiece into which the screw is to be screwed; and wherein the screw is tightened by using the bit which moves toward the workpiece together with the rotary driver to tighten the screw into the workpiece, the screw tightening device further comprising: a bit cover which extends in an axial direction parallel to the imaginary central axis and which is formed in a cylindrical shape surrounding the bit; a slide shaft which is fixed to the bit cover and extends in the axial direction; and a guide member which is fixed to the rotary driver and which slides in the axial direction along the slide shaft while in contact with the slide shaft, thereby guiding the axial movement of the rotary driver and the bit relative to the slide shaft and the bit cover, A screw fastening device in which, during the screw fastening, the position of the bit cover relative to the workpiece is determined with a front end face of the bit cover that is closer to the workpiece in the axial direction in contact with the workpiece or with the end face facing the workpiece with a gap therebetween, and the bit and the screw proceed forward toward the workpiece inside the bit cover whose position relative to the workpiece is determined.

2. The screw fastening device according to claim 1, further comprising a moving device that moves the rotary drive machine toward the workpiece, the moving device being a human-collaborative robot.

3. The screw fastening device according to claim 1, further comprising: a base member fixed to a moving device that moves the rotary drive machine toward the workpiece; and a coupling mechanism interposed between the base member and the rotary drive machine, coupling the base member and the rotary drive machine in a state in which relative displacement of the rotary drive machine relative to the base member in the rearward direction opposite to the forward direction in the axial direction is permitted, wherein during the screw fastening, the rotary drive machine is moved toward the workpiece by the moving device through the base member and the coupling mechanism, and when the magnitude of the rearward resistance acting on the rotary drive machine through the bit is less than a predetermined value, the rotary drive machine is kept immobile in the axial direction relative to the base member, and when the magnitude of the resistance is equal to or greater than the predetermined value, the rotary drive machine is displaced rearward relative to the base member through the coupling mechanism.

4. The screw tightening device as described in claim 3, further comprising: a rear relative displacement sensor that detects a rear relative displacement, which is the rearward relative displacement of the rotary drive machine with respect to the base member; and a movement stop control unit that causes the moving device to stop movement of the rotary drive machine when the rear relative displacement sensor detects the rear relative displacement.

5. The screw tightening device of claim 3 or 4, further comprising a pressing device fixed to the base member, the pressing device being switchable between: (a) a pressing state in which the forward pressing force of the same magnitude as the reaction force acts on the base member, and the pressing device is switchable between: (a) a pressing state in which the rearward reaction force acts on the base member and the forward pressing force is applied to the rotary drive machine; and (b) a non-pressing state in which the application of the pressing force to the rotary drive machine is released.

6. The bit cover is formed with a first opening and a second opening opposed to each other in a direction perpendicular to the axial direction, and a first claw member and a second claw member opposed to each other in the perpendicular direction, each of which has a fixed axial position relative to the bit cover; a gripping mechanism for displacing each of the first claw member and the second claw member in the perpendicular direction relative to the bit cover, the gripping mechanism being switchable between: (A) an open state in which the first claw member is positioned at a first retracted position opposed to the first opening outside the bit cover, and the second claw member is positioned at a second retracted position opposed to the second opening outside the bit cover; and (B) a screw gripping state in which the first claw member in the first retracted position is pressed against a portion of the screw whose head is engaged with the tip of the bit and exposed at the first opening, and the second claw member in the second retracted position is pressed against a portion of the screw exposed at the second opening. The screw fastening device according to claim 1 , further comprising:

7. A screw tightening device as described in any one of claims 1 to 6, further comprising a forward movement amount sensor that measures the forward movement amount of the rotary drive and the bit relative to the bit cover, the position of which is determined relative to the workpiece, during the screw tightening.

8. A screw tightening device as described in any one of claims 1 to 7, further comprising: a support member arranged in a fixed state relative to the workpiece, the support member having a support surface located rearward of the workpiece, opposite the front in the axial direction, wherein the bit cover has a stopper surface facing the support surface, and when the screw is tightened, the stopper surface comes into contact with the support surface, thereby determining the position of the bit cover relative to the workpiece with the bit cover supported by the support member.

9. The screw fastening device according to claim 8, wherein when the position of the bit cover relative to the workpiece is determined, the gap is secured between the end face of the bit cover and the workpiece.

10. A screw fastening device as described in any one of claims 1 to 7, further comprising a bit cover retraction device having a first fixed part fixed to the rotary drive, a second fixed part fixed to the bit cover, and a retraction mechanism that moves the second fixed part rearward relative to the first fixed part in the axial direction opposite to the forward direction, thereby moving the bit cover rearward relative to the rotary drive, wherein during the screw fastening, the bit cover is moved rearward relative to the rotary drive by the retraction mechanism in conjunction with the forward movement of the rotary drive, the bit, and the screw toward the workpiece.

11. The screw fastening device of claim 10, further comprising: a distance sensor fixed to the bit cover that measures the axial distance between the distance sensor and the workpiece; and a retraction mechanism control unit that suppresses changes in the axial distance between the distance sensor and the workpiece by controlling the amount of rearward movement of the second fixed part relative to the first fixed part by the retraction mechanism based on the measurement result of the distance sensor.

12. The screw fastening device according to claim 10 or 11, wherein when the position of the bit cover relative to the workpiece is determined, the gap is secured between the end face of the bit cover and the workpiece.

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