Screw tightening device

Abstract

To provide a screw fastening apparatus which can measure the total length of a fastening component to be supplied and supply the fastening component regardless of the length.SOLUTION: A screw fastening apparatus 10 comprises: a component supply device 30 which includes measurement means 43 for measuring the length of a fastening component N and is configured to make the fastening component N stand by at a prescribed standby position after length measurement by the measurement means 43; a driver unit 20 which takes out the fastening component N from the standby position and fastens the fastening component to a prescribed workpiece; a position control mechanism 24 which moves the driver unit 20; and a control unit 50 which is configured to perform quality determination on the length of the fastening component N by comparing the measurement value of the measurement means 43 with the preset setting value and control the drive of the position control mechanism 24 on the basis of the determination result.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a screw tightening device equipped with a component supply device capable of inspecting the overall length of fastening components. [Background technology]

[0002] Conventionally, screw tightening devices equipped with a driver unit that engages with a screw and a component supply device that supplies the screw to the driver unit have been known. Patent Document 1 in particular discloses a component supply device capable of measuring the overall length of a screw. This component supply device has a suspension member that suspends and supports the screw and a pair of photoelectric sensors positioned to sandwich the legs of the screw suspended and supported by the suspension member. One of the photoelectric sensors emits laser light, and the other receives it, and the length of the fastening part is determined to be good or bad based on the amount of light received. Furthermore, after the photoelectric sensors determine whether the screw is good or bad, this component supply device is able to pressure-feed good screws to the driver unit through a screw supply hose. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-95328 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional screw tightening devices have a structure in which the component supply device pressure-feeds screws to the driver unit. Therefore, while good screws could be removed by pressure-feeding them to the driver unit as described above, defective screws had to be removed individually by the operator. This resulted in problems such as a long downtime and reduced work efficiency, as the next stage of screws could not be supplied until the operator removed the defective screws. Furthermore, because the component supply device pressure-feeds screws, there were problems such as the inability to use some screws, such as short screws that tend to reverse in the supply hose connecting the component supply device and the chuck unit, and plastic screws that are damaged by the impact of a collision with the chuck unit. [Means for solving the problem]

[0005] The present invention was conceived in view of the above-mentioned problems, and aims to provide a screw tightening device with good work efficiency. To achieve this aim, the present invention is characterized by comprising: a component supply device including a measuring means for measuring the length of a fastening component and configured to wait for the fastening component at a predetermined waiting position after the length measurement by the measuring means; a driver unit for removing the fastening component from the waiting position and fastening it to a workpiece; a position control mechanism for moving the driver unit; and a control unit configured to compare the measurement value of the measuring means with a preset value to determine whether the length of the fastening component is good or bad, and to control the drive of the position control mechanism based on the determination result. Note that it is preferable that the control unit controls the drive of the position control mechanism so that if the length of the fastening component is good, the driver unit is moved to a predetermined fastening position, and if the length of the fastening component is bad, the driver unit is moved to a predetermined ejection position.

[0006] Furthermore, it is preferable that the component supply device includes a suspension member that suspends and supports the fastening components, a push-up means that pushes the fastening components suspended from the suspension member upward from below, and a restricting lid that is fixed above the push-up means and restricts the fastening components pushed up by the push-up means so that they cannot be pushed up beyond a predetermined height, the measuring means measures a dimension corresponding to the entire length of the fastening components restricted by the restricting lid, and the suspension member waits at a predetermined standby position with the fastening components suspended and supported after the measuring means measures the length of the fastening components.Furthermore, it is preferable that the component supply device includes a detection sensor that detects fastening components that have reached the standby position, and a reciprocating drive source that moves the suspension member based on a signal from the detection sensor. [Effects of the Invention]

[0007] According to the above invention, the driver unit is configured to retrieve fastening components transported by the component supply device to a standby position and move them to a predetermined position, and since the screws are not pressure-fed, it has the advantage of being able to supply screws that are difficult to pressure-fed, such as short screws and plastic screws. Furthermore, the control unit is configured to determine whether the length of the fastening components is good or bad and to control the drive of the position control mechanism based on the determination result, so the screw tightening device does not need to wait until the worker removes the screw, which has the advantage of improving work efficiency. Furthermore, the control unit is configured to transport good screws to a predetermined fastening position while ejecting defective screws to a predetermined ejection position, which has the advantage of allowing defective screws to be smoothly removed even if they are mixed in.

[0008] In addition, since the measuring means is configured to measure the overall length of the fastening part, it has the advantage of being able to detect foreign products with different head heights. Furthermore, since it is equipped with a detection sensor that can detect when the screw has reached a predetermined standby position, it is possible to immediately detect when the screw is not supported by the hanging member, which has the advantage of shortening the cycle time. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a side view showing a screw fastening device according to the present invention; [Figure 2] 1 is a plan view showing a screw fastening device according to the present invention; [Figure 3] 1A and 1B are enlarged views of essential parts showing the operation of the component supply device according to the present invention, in which (a) is a plan view showing a state in which the hanging member is located at a receiving position, (b) is a plan view showing a state in which the hanging member is located at an inspection position, and (c) is a plan view showing a state in which the hanging member is located at a standby position. [Figure 4] 4A and 4B are enlarged views of essential parts showing the operation of the component supply device according to the present invention, in which (a) is a cross-sectional side view taken along line AA in FIG. 3, (b) is a cross-sectional side view taken along line BB in FIG. 3, and (c) is a cross-sectional side view taken along line BB in FIG. 3 for explaining the operation of transitioning from the state in (b) to the next state. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1 to 4, a screw tightening device 10 tightens a screw N, which is an example of a fastening part, into a predetermined workpiece, and includes a driver unit 20 that tightens the screw N, a position control mechanism 24 that moves the driver unit 20, a component supply device 30 that supplies the screw N to the driver unit 20, and a control unit 50 that controls the driving of these devices.

[0011] 1, the driver unit 20 includes a driver bit 21 that can be fitted with a screw N, a tightening motor 22 that rotates and drives the driver bit 21, and a screw guide 23 that houses the driver bit 21 so that it can move back and forth in the axial direction. The screw guide 23 is biased toward the workpiece by a cushion spring (not shown), and is configured so that, when the cushion spring flexes, the screw guide 23 moves axially relative to the driver bit 21 and the tightening motor 22. In addition, a suction means such as a vacuum generator is connected to the screw guide 23, and when the suction means is driven, the screw N can be sucked and held at the opening at its lower end.

[0012] The position control mechanism 24 is composed of a linear arm 25 that can move linearly in the front-to-rear direction, a swivel arm 26 that is rotatably attached to the linear arm 25, and an elevation drive unit 27 that is attached to the tip of the swivel arm 26. The elevation drive unit 27 includes a ball screw 271 that extends in the up-down direction, an elevation motor 272 that rotates the ball screw 271, and a drive nut 273 that screws into the ball screw 271, and the driver unit 20 is connected to the drive nut 273. By driving the position control mechanism 24, the driver unit 20 can move up and down as shown by the two-dot chain line in FIG. 1 and can move within a movable range 201 shown in FIG. 2.

[0013] The component supply device 30 includes a chute rail 31 for transporting the screws N forward, and a feed unit 32 for receiving the foremost screw N on the chute rail 31. The feed unit 32 includes a frame 33, a hanging member 36 disposed within the frame 33, and a push-up means 40 for pushing up the screw N supported by the hanging member 36.

[0014] The chute rail 31 is composed of two plates extending in the front-to-rear direction, and these plates are installed with a predetermined gap between them that is slightly wider than the outer diameter of the shank of the screw N but narrower than the outer diameter of the head. Therefore, the chute rail 31 can support the screw N in a suspended state with the head seating surface of the screw N abutting against its upper surface. A vibrator (not shown) is connected to the chute rail 31, and the suspended and supported screw N is transported forward by the vibration of the vibrator. A storage section (not shown) that can store a large number of screws N is connected to the rear of the chute rail 31, and this storage section is configured to supply the screws N in a line onto the chute rail 31.

[0015] As shown in FIGS. 3 and 4 , the frame 33 is formed with a supply port 331 that opens rearward. The chute rail 31 enters this supply port 331, and a notched groove 332 that extends in a direction perpendicular to the chute rail 31 (hereinafter referred to as the lateral direction) is continuous in front of the supply port 331. Both lateral sides of the notched groove 332 are closed by side walls 334, 335. An inspection hole 333 that penetrates vertically is formed in the bottom surface of the notched groove 332 at a position closer to the side wall 334 than the supply port 331. Meanwhile, a fixed regulating lid 34 disposed above the inspection hole 333 and a detection sensor 35 disposed closer to the side wall 334 than the regulating lid 34 are fixed to the upper surface of the frame 33. The regulating lid 34 is a plate that prevents the screw N from rising above a predetermined height when a push-up means 40, which will be described later, pushes up the screw N. A passage groove 341 configured to allow the head of the screw N to pass through is formed through the lower surface of the regulating lid 34. Furthermore, the detection sensor 35 is a pair of optical sensors that emit detection light from a light-emitting portion to a light-receiving portion, and is disposed at a predetermined height where the detection light is blocked by the head of the screw N that has reached the gap between the light-emitting portion and the light-receiving portion, as shown in FIG. 3(c). The detection sensor 35 is connected to the control unit 50, and is configured to output a detection signal for the screw N to the control unit 50 when the light from the detection sensor 35 is blocked by the screw N as described above. The dimensions of the passage groove 341 of the regulating cover 34 are set so that the gap with the upper end of the head is shorter than the dimension of the leg of the screw. Therefore, when the screw N is pushed up by the push-up means 40 during driving, as described below, the lower end of the leg of the screw N is prevented from slipping out of the hanging groove 361.

[0016] The hanging member 36 is disposed within the notched groove 332, and its thickness in the front-to-rear direction is configured to be approximately the same dimension as the groove width of the notched groove 332. A roughly U-shaped hanging groove 361 that penetrates in the vertical direction is cut out in the rear surface of the hanging member 36, and the groove width of this hanging groove 361 is configured to be slightly wider than the outer diameter of the shank of the screw N but narrower than the outer diameter of the head, similar to the chute rail 31. This allows the hanging member 36 to slide freely along the notched groove 332 and to suspend and support the screw N received from the chute rail 31.

[0017] Further, reciprocating cylinders 371, 372 that reciprocate suspending member 36 along notched groove 332 are attached to side walls 334, 335. Reciprocating cylinder 371 is an air cylinder fixed to side wall 334, and its piston rod is connected to suspending member 36. The stroke of this reciprocating cylinder 371 is designed so that when the piston rod is contracted, suspending groove 361 of suspending member 36 is continuous with chute rail 31 as shown in FIG. 3(a), and when the piston rod is extended, suspending groove 361 is located between detection sensors 35 as shown in FIG. 3(c). In other words, the suspending member is configured to reciprocate, driven by reciprocating cylinder 371, between a position where suspending groove 361 is continuous with chute rail 31 (hereinafter referred to as the receiving position) and a position where suspending groove 361 is located between the light receiving unit and light emitting unit of detection sensor 35 (hereinafter referred to as the standby position).

[0018] On the other hand, reciprocating cylinder 372 is an air cylinder fixed to side wall 335, and its piston rod is disposed so as to be able to abut against the hanging member 36. This reciprocating cylinder 372 has a larger cylinder diameter than reciprocating cylinder 371, and its stroke is shorter than that of reciprocating cylinder 371. As a result, when both reciprocating cylinders 371 and 372 extend their piston rods, the hanging member is pressed against reciprocating cylinder 372 and stops at a predetermined position (hereinafter referred to as the inspection position) between the receiving position and the standby position, as shown in Figure 3(b). Note that inspection hole 333 of frame 33 is positioned so as to communicate with hanging groove 361 of hanging member 36 that has reached the inspection position, as shown in Figures 4(b) and 4(c).

[0019] As described above, the suspending member 36 is positioned at one of three positions: the receiving position, the standby position, and the inspection position, by being driven by the reciprocating cylinders 371 and 372. Furthermore, the component supply device 30 is arranged so that, as shown in FIG. 3(c), at least the suspending groove 361 of the suspending member 36 that has reached the standby position is positioned within the movable range 201 of the driver unit 20.

[0020] 4(a), a push-up means 40 for pushing up the screw N is provided on the underside of the frame 33. The push-up means 40 includes a push-up cylinder 41, which is an example of a push-up drive source, fixed to the frame 33. A drive unit 411 of the push-up cylinder 41 is connected to a push-up rod 42 disposed directly below the inspection hole 333 and a measuring means 43 linked to the push-up rod 42. The push-up rod 42 has approximately the same diameter as the inspection hole 333, and is set to a length that allows it to come into contact with the lower end of the screw N suspended from the suspension member 36 when the drive unit 411 of the push-up cylinder 41 rises, as shown in FIG. 4(c). The measuring means 43 is a contact sensor equipped with a contact 431 that contracts in a contracting direction upon contact with the frame 33, and is configured to output the amount of contraction of the contact 431 to the control unit 50.

[0021] The control unit 50 is connected to the driver unit 20, the position control mechanism 24, the component supply device 30, and external devices such as suction means, and is configured to be able to control various drives. The control unit 50 is also configured to be able to switch the target position of the driver unit 20 by the position control mechanism 24 based on a signal from the measurement means 43, and is configured to set the target position above a predetermined screw tightening point when the length of the screw N is appropriate, but to switch the target position above a predetermined external discharge position when the length of the screw N is inappropriate.

[0022] Next, the operation of the screw fastening device 10 configured as above will be described. When a drive signal is input, the control unit 50 drives the vibrator of the component supply device 30 and retracts the piston rods of the reciprocating cylinders 371 and 372 as shown in FIG. 3(a). This causes the chute rail 31 to vibrate, and the screw N suspended and supported on the chute rail 31 is vibrated and conveyed forward. At the same time, the hanging groove 361 of the hanging member 36 that has reached the receiving position connects to the terminal end of the chute rail 31. As a result, the leading screw N is transferred from the terminal end of the chute rail 31 to the hanging groove 361. When the screw N is suspended and supported in the hanging groove 361, the control unit 50 drives the reciprocating cylinders 371 and 372 to extend these piston rods. As a result, the hanging member 36 is driven by the reciprocating cylinder 371 and moves toward the side wall 334. At this time, the reciprocating cylinder 372 also extends its piston rod, so that the hanging member 36 comes into contact with the piston rod of the reciprocating cylinder 372 as shown in FIG. 3(b) and stops at the inspection position.

[0023] As described above, when the hanging member 36 reaches the inspection position and the hanging groove 361 connects to the inspection hole 333 as shown in FIG. 4(b), the control unit 50 retracts the push-up cylinder 41 to raise the push-up rod 42 and the measuring means 43. As a result, the upper end of the push-up rod 42 abuts against the lower end of the screw N suspended from the hanging member 36 and pushes it upward. As a result, the screw N is pushed upward until its top surface abuts against the restricting cover 34 as shown in FIG. 4(c). At this time, the measuring means 43 also rises in conjunction with the push-up rod 42 and presses its contact 431 against the lower surface of the frame 33 to retract it. As a result, the measuring means 43 measures the retracted dimension of the contact 431 and outputs the result to the control unit 50. The control unit 50 compares the contracted dimension of the contact 431 output by the measuring means 43 with a predetermined appropriate value, and if the contracted dimension of the contact 431 is the appropriate value, it determines that the contact is a good product, but if it is outside the appropriate value, it determines that the contact is defective.

[0024] As described above, upon receiving a signal from measuring means 43, control unit 50 extends push-up cylinder 41, causing push-up rod 42 to move out of hanging groove 361. Thereafter, reciprocating cylinder 372 is driven to retract. As a result, hanging member 36, which has been pressed down by the piston rod of reciprocating cylinder 372, moves from the inspection position toward the standby position. When hanging member 36 reaches the standby position as shown in FIG. 3(c), the head of screw N suspended and supported in hanging groove 361 blocks the detection light of detection sensor 35.

[0025] When the detection light of detection sensor 35 is blocked as described above, control unit 50 drives linear motion arm 25 and pivot arm 26 of position control mechanism 24 to move driver unit 20 above the standby position. Because position control mechanism 24 is driven when detection sensor 35 detects screw N in this manner, even if driver unit 20 reaches the standby position without screw N being supported by suspending member 36, driving of position control mechanism 24 can be prevented, resulting in high efficiency. Furthermore, when driver unit 20 reaches above the standby position, control unit 50 drives lift drive unit 27 to lower driver unit 20 toward screw N and drives the suction means to suck air from the lower end of screw guide 23. Therefore, when screw guide 23 descends to suspending member 36, screw N suspended and supported in suspending groove 361 is suction-held within screw guide 23. When the screw guide 23 adsorbs and holds the screw N in this way, the control unit 50 drives the lifting drive unit 27, the linear motion arm 25, and the swivel arm 26 to move the driver unit 20 to a predetermined target position. At this time, if the screw N is a good product, as described above, the control unit 50 sets the target position to a predetermined screw fastening point provided on the workpiece and fastens the screw N into the workpiece. On the other hand, if the screw N is defective, the control unit 50 switches the target position to an external ejection position and ejects the screw N. In this way, it is possible to eject both good and defective screws N from the component supply device 30.

[0026] Furthermore, as described above, when the screw N is removed from the hanging member 36 by the screw guide 23, the detection light of the detection sensor 35 is again able to pass through. When the detection light is again able to pass through, the control unit 50 contracts the reciprocating cylinders 371 and 372. This causes the hanging member 36 to return to the receiving position, and the hanging groove 361 is again connected to the chute rail 31, making it possible to receive the next screw N. In this way, the configuration in which the driver unit 20 removes the screw N from the hanging groove 361 eliminates the need to wait for the worker to remove the defective screw N, even if the screw N is defective, and therefore the operating time of the screw fastening device 10 is extended, improving work efficiency.

[0027] Furthermore, because the screw fastening device 10 is structured such that the driver unit 20 comes to the component supply device 30 to retrieve the screw N as described above, there is no need to perform a step of pressure-feeding the screw N after measuring the length of the screw N with the push-up means 40. This makes it possible to deliver even screws that are difficult to pressure-feed, such as short screws that reverse inside the pressure-feed hose or plastic screws that may be damaged by the impact of pressure-feeding, to the driver unit 20. In particular, because the control unit 50 is configured to switch and move the target point between the screw tightening point or an external discharge position based on the length measurement result of the screw N by the push-up means 40, even if screws of different lengths are mixed in, this prevents them from being tightened and also makes it possible to smoothly discharge any mixed screws.

[0028] The screw fastening device 10 according to the present invention is not limited to the above-described configuration and may be modified in various ways without departing from the spirit of the invention. For example, the position control mechanism 24 that moves the driver unit 20 is not limited to the linear arm 25, the swivel arm 26, and the lifting drive unit 27 as described herein, and other means may be used. Furthermore, while the screw fastening device 10 described above is configured to switch the target point between a predetermined screw fastening point and an external discharge position based on the length measurement results of the screw N, the present invention is not limited to this configuration and may be configured to switch between a first screw fastening point and a second screw fastening point for each screw length, or to discharge the mixed screws to different discharge positions for each length. Furthermore, the reciprocating cylinders 371 and 372 are an example of a reciprocating drive source that reciprocates the hanging member 36 along the notch groove 332, and a ball screw mechanism or other reciprocating drive source may also be used. Similarly, the detection sensor 35 is not limited to an optical sensor and may be a proximity sensor or other sensor. [Explanation of symbols]

[0029] 10...Screw tightening device 20...Driver unit 24... Position control mechanism 30... Parts supply device 31 ... Alignment and conveyance means 32 ... Cutting unit 33...frame 34 ... Regulatory cover 35 ... detection sensor 36... Hanging member 361…Suspension groove 371,372... Round-trip transportation 40... Push-up means 41 ... Push-up drive source 42 ... Push-up rod 43 …Measurement means 50 ... Control section N … Fasteners

Claims

1. a component supply device including a measuring means for measuring the length of a fastening component, and configured to make the fastening component wait at a predetermined waiting position after the length is measured by the measuring means; a driver unit for taking out the fastening component from the waiting position and fastening it to a workpiece; a position control mechanism for moving the driver unit; and a control unit configured to compare the measurement value of the measuring means with a preset value to determine whether the length of the fastening component is good or bad, and to control the drive of the position control mechanism based on the determination result; A screw tightening device comprising: a detection sensor that detects a fastening component that has reached the standby position; and a reciprocating drive source that moves the hanging member based on a signal from the detection sensor.

2. The screw tightening device according to claim 1, characterized in that the control unit controls the drive of the position control mechanism so as to move the driver unit to a predetermined fastening position when the length of the fastening part is good, and to move the driver unit to a predetermined ejection position when the length of the fastening part is bad.

3. 3. The screw tightening device according to claim 1, wherein the component supply device includes a hanging member that suspends and supports the fastening component, a push-up means that pushes the fastening component suspended from the hanging member from below upward, and a regulating lid that is fixed above the push-up means and regulates the fastening component pushed up by the push-up means so that it cannot be pushed up beyond a predetermined height, wherein the measuring means measures a dimension equivalent to the overall length of the fastening component regulated by the regulating lid, and the hanging member is configured to wait at a predetermined waiting position in a state where it suspends and supports the fastening component after the measuring means measures the length of the fastening component.

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