Screw fastening device

Abstract

To provide a screw fastening device which has low energy consumption, and further, can be driven with easy control configuration.SOLUTION: A screw fastening device 10 comprises: a driver unit 20 for rotationally driving a fastening tool 23 capable of fitting to a screw S and a movement unit 40 for moving the driver unit 20 in an axial direction of the fastening tool 23; and a control unit 50 which can control drive of the driver unit 20 and the movement unit 40. The movement unit 40 has: a movement block 43 connected to the driver unit 20; a ball screw 41 to which the movement block 43 is screwed; and a movement motor 42 for rotationally driving the ball screw 41 and a controller 44 for controlling drive of the movement motor 42. The controller 44 controls rotation of the movement motor 42 on the basis of an advancement signal or a retreat signal transmitted from the control unit 50.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a screw fastening device for fastening a screw into a fastened member. [Background technology]

[0002] Conventionally, as disclosed in Patent Document 1, a screw fastening device for fastening a screw into a workpiece is known that includes a tool unit having a bit and a motor for rotating the bit, and an air cylinder as a lifting drive source for lifting and lowering the tool unit, as disclosed in Patent Document 1. In this screw fastening device, the tool unit is connected to the piston rod of the air cylinder, and the tool unit can be lifted and lowered by the air cylinder driving the piston rod to extend and retract. The air cylinder of such a screw fastening device is provided with solenoid valves at the forward and backward air vents, respectively, and the air inflow direction is changed depending on whether the drive signal input to these solenoid valves is turned on or off, thereby switching the extension and retraction movement of the piston rod. For this reason, the screw fastening device has an advantage that the control device can control the lifting and lowering movement of the tool unit simply by switching the drive signals to the two solenoid valves to turn on or off. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 55-096277 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional screw fastening devices that use an air cylinder as a lifting drive source have problems such as high energy consumption because compressed air is used to drive the air cylinder.

[0005] Therefore, an object of the present invention is to provide a screw fastening device that consumes little energy and can be driven with a simple control configuration. [Means for solving the problem]

[0006] In order to achieve this object, the present invention comprises a driver unit that rotates and drives a fastening tool that can be engaged with a screw, a moving unit that moves the driver unit in the axial direction of the fastening tool, and a control device that can control the driving of the driver unit and the moving unit, wherein the moving unit has a moving block connected to the driver unit, a ball screw that screws into the moving block, a moving motor that rotates and drives the ball screw, and a controller that controls the driving of the moving motor, and the controller controls the rotation of the moving motor based on a forward signal or a backward signal transmitted from the control device. In addition, it is preferable that when the controller receives the forward signal, it moves the driver unit toward a pressing end position set on the side of the fastened member, and when the controller receives the backward signal, it moves the driver unit toward a standby position set in a direction away from the fastened member. In addition, it is preferable that the driver unit has a cylindrical screw guide that contains the fastening tool so that it can rotate and move axially, and a chuck unit that holds the screw is arranged on an extension of the screw guide, and when the controller receives both the forward signal and the backward signal, it moves the driver unit toward an suction position that is set so that the screw guide is located just before the screw held by the chuck unit. In addition, it is preferable that the controller switches the rotation speed of the movement motor to a low speed when the tip of the advancing driver unit reaches a pressing start position that is set immediately before the tip of the advancing driver unit collides with the fastened member. Effect of the Invention

[0007] According to the above invention, the controller controls the drive of the moving motor based on the forward and backward signals sent from the control device, and moves the driver unit to a predetermined position. This has the advantages of being able to operate with a simple control configuration and of reducing energy consumption because no air cylinder is used. In addition, when the controller receives the forward signal, it moves the driver unit forward, and when it receives the backward signal, it moves the driver unit backward. Therefore, it can be operated with the same control configuration as a conventional screw tightening device using an air cylinder, and has the advantage of being easily replaceable. In addition, when the controller receives both a forward signal and a backward signal, it moves the driver unit toward the suction position set so that the screw guide is positioned just before the screw held in the chuck unit, which has the advantage of making it possible to stably suction and hold the screw at the suction position. In addition, it is preferable that the controller switches the rotation speed of the movement motor to a low speed when the tip of the advancing driver unit reaches a pressing start position that is set immediately before the tip of the advancing driver unit collides with the fastened member. In addition, the rotational speed of the moving motor is switched to a low speed just before the advancing driver unit collides with the fastened part, which has the advantage of reducing the impact that occurs when the driver unit comes into contact with the fastened part. [Brief description of the drawings]

[0008] [Figure 1] 1 is a front view showing a structure of a screw fastening device according to the present invention; [Diagram 2] 1 is a side view showing a structure of a screw fastening device according to the present invention. [Diagram 3] 1 is a cross-sectional side view showing a structure of a screw fastening device according to the present invention. [Figure 4] 4 is a cross-sectional side view showing a state transitioned from FIG. 3 to the next state. FIG. [Diagram 5] 5 is a cross-sectional side view showing a state transitioned from FIG. 4 to the next state. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to Fig. 1 to Fig. 5. In Fig. 1 and Fig. 2, reference numeral 10 denotes a screw fastening device that fastens a screw S into a workpiece W. This screw fastening device 10 has a driver unit 20 that fastens the screw S, and a moving unit 40 that raises and lowers this driver unit 20. The driver unit 20 and the moving unit 40 are connected to a control device 50.

[0010] The driver unit 20 has a hollow cylindrical housing 21 as shown in FIG. 3. An AC servo motor 22 (hereinafter referred to as the fastening motor 22) is held in the upper part of the housing 21 so that its output shaft (not shown) is inserted into the housing 21, and a driver bit 23 is configured to be integrally connected to the output shaft of the fastening motor 22 via a shaft coupling (not shown). A hollow cylindrical screw guide 24 that rotatably contains the driver bit 23 is provided in the lower part of the housing 21, and the screw guide 24 is configured to be movable in the axial direction relative to the housing 21 and the driver bit 23. A hose coupling 25 is attached to the screw guide 24, and an intake hose (not shown) that continues to an intake means such as an external vacuum generating device is connected to the hose coupling 25. Therefore, when the intake means is driven, the inside of the screw guide 24 becomes negative pressure, and the screw S can be attracted and held at the lower end opening of the screw guide 24. The screw guide 24 is constantly biased downward by a guide spring (not shown) enclosed within it, and is configured to be able to move axially relative to the housing 21 and the driver bit 23 as the guide spring flexes.

[0011] 1, the screw guide 24 is provided with two dogs 261, 262, and the housing 21 is provided with two optical sensors 271, 272 above the dogs 261, 262. Each of the optical sensors 271, 272 is integrally provided with a light-emitting section that outputs detection light and a light-receiving section that receives the detection light, and the dogs 261, 262 enter between them to block the detection light, thereby enabling detection of the relative positional relationship between the screw guide 24, the housing 21, and the driver bit 23. The dogs 261, 262 are provided at different heights, and one of the dogs 261 is disposed at a height capable of blocking the detection light of the optical sensor 271 when the screw guide 24 is in contact with the upper surface of the workpiece W and the screw S fitted to the tip of the driver bit 23 is screwed into the workpiece W by several threads. Moreover, the other dog 262 is disposed at a height capable of blocking the detection light of the optical sensor 272 when the screw guide 24 is in contact with the upper surface of the fastened workpiece W and the screw S fitted into the tip of the driver bit 23 is normally fastened into the fastened workpiece W. With this structure, if the detection light of the optical sensors 271, 272 is blocked when the fastening motor 22 detects a predetermined output, the screw fastening device 10 determines that the screw S is normally seated in the fastened workpiece W and no screw float is occurring.

[0012] Further, below the driver unit 20, a chuck unit 30 capable of holding a screw S pressure-fed from an external parts supply device is provided. The chuck unit 30 has a chuck body 31 fixed on the moving path of the screw guide 24 and the driver bit 23, and a guide hole 32 that includes the tip of the screw guide 24 is formed through the chuck body 31. A pair of chuck jaws 33, 33 are attached to the chuck body 31 so as to be able to swing, and a holding hole 34 that is located on an extension line of the guide hole 32 and capable of holding a screw S is formed separately on the opposing surface of the chuck jaws 33, 33. Further, the chuck body 31 is provided with a supply pipe 35 that can swing in a direction perpendicular to the swinging surface of the chuck jaws 33, 33. The tip of the supply pipe 35 is configured to be connected to the holding hole 34 and to close the opening of the guide hole 32, while a screw supply hose that continues to a parts supply device (not shown) is connected to the base end side. Therefore, the screw S pressure-fed from the part supply device can be supplied to the holding hole 34 through the screw supply hose and the supply pipe 35 .

[0013] The chuck body 31 is fitted with a regulating plate 36 which can swing in conjunction with the supply pipe 35. A regulating claw is provided at the tip of the regulating plate 36, which abuts against the outer surface of the chuck jaws 33 in the closed state and regulates the swinging of the chuck jaws 33. The regulating claw is set so that it gradually moves away from the chuck jaws 33 by swinging along the supply pipe 35, and can completely move away from the chuck jaws 33 before the screw guide 24 starts to push the chuck jaws 33 open. The supply pipe 35 and the regulating plate 36 are constantly biased toward the chuck jaws 33 by a torsion coil spring 37, and the torsion coil spring 37 elastically deforms in accordance with the swinging of the supply pipe 35 and the regulating plate 36.

[0014] The moving unit 40 has a ball screw 41 extending in the vertical direction, a pulse motor 42 (hereinafter referred to as the moving motor 42) that rotates the ball screw 41, and a moving block 43 that is screwed into the ball screw 41 and moves up and down as the ball screw 41 rotates, and the housing 21 of the driver unit 20 is connected to the moving block 43. Therefore, the driver unit 20 can be raised and lowered integrally with the moving block 43 by being driven by the moving motor 42.

[0015] In addition, the moving unit 40 is provided with a controller 44 integral with the moving motor 42, which controls the driving of the moving motor 42. The controller 44 controls the driving of the moving motor 42 based on two driving signals (hereinafter referred to as a forward signal and a backward signal) transmitted from the control device 50, and is configured to drive the moving motor 42 in the forward direction to lower the moving block 43 toward a pressing end position described later when a forward signal is input from the control device 50, and to drive the moving motor 42 in the reverse direction to raise the moving block 43 toward a standby position described later when a backward signal is input. Furthermore, the controller 44 is configured to move the moving block 43 toward a suction position described later when both the forward signal and the backward signal are input from the control device 50. Furthermore, the controller 44 constantly measures the amount of rotation of the moving motor 42, and when the moving block 43 is located at the waiting position or the suction position, it continues to output a predetermined arrival signal to the control device 50, and when the moving block 43 reaches a pressing start position described below while a forward movement signal is being sent from the control device 50, it is configured to switch the movement of the moving block 43 to a low speed and a thrust force (hereinafter referred to as pressing thrust) that does not cause the driver bit 23 to cam out of the screw S when the screw tightening is completed.

[0016] In this embodiment, the standby position is set at a position where the driver bit 23 and the screw guide 24 of the driver unit 20 do not come into contact with the supply pipe 35 of the chuck unit 30 as shown in Fig. 3, and the suction position is set at a position where the tip of the screw guide 24 swings the suction pipe and where the tip of the screw guide 24 is located just before the head of the screw S held in the holding hole 34 of the chuck jaws 33, 33 as shown in Fig. 4. Furthermore, the pressing start position is set at a position where the screw guide 24 and the screw S held by suction at the tip of the screw guide 24 reach a predetermined distance above the fastened member W as shown in Fig. 5, and the pressing end position is set at a position where the lower end of the screw guide 24 reaches below the fastened member W as shown by the two-dot chain line in Fig. 3.

[0017] The control device 50 is connected to the fastening motor 22, optical sensors 271, 272, a controller 44, and external devices such as the vacuum generator and supply device, and is configured to output various drive signals to the fastening motor 22 and the controller 44 based on signals received from these devices.

[0018] Next, the operation of the screw fastening device 10 configured as above will be described. When a start signal is input to the screw fastening device 10 in a state where the driver unit 20 is waiting at the standby position and the controller 44 is outputting an arrival signal to the control device 50, the control device 50 transmits a drive signal to the component supply device to pressure-feed the screw S toward the chuck unit 30. After the screw S is supplied, the control device 50 transmits a forward signal and a backward signal to the controller 44. As a result, the controller 44, which has received both the forward signal and the backward signal, drives the moving motor 42 in the forward direction to lower the driver unit 20 to the suction position. The control device 50 transmits drive signals to the fastening motor 22 and the vacuum generating device at the same time as transmitting the forward signal and the backward signal, and the fastening motor 22 rotates the driver bit 23 and sucks air from the lower end of the screw guide 24 at the same time as the driver unit 20 descends.

[0019] As described above, when the driver unit 20 starts to descend, the screw guide 24 swings the supply pipe 35 and enters the holding hole 34. After that, when the moving block 43 descends to the adsorption position as shown in FIG. 4, the controller 44 transmits an arrival signal to the control device 50 and stops driving the moving motor 42. At this time, the lower end of the screw guide 24 is located just before the screw S held in the holding hole 34, so the screw S is sucked into the screw guide 24 from the lower end opening. By stopping once at the adsorption position in this way, it is possible to prevent poor adsorption of the screw S. After stopping at the adsorption position for a certain period of time in this way, the control device 50 stops the retreat signal. As a result, the controller 44 receives only the forward signal.

[0020] As described above, the controller 44, which receives only the forward signal, rotates the moving motor 42 in the forward direction to lower the moving block 43 and the driver unit 20 toward the fastened member W. When the lowered moving block 43 reaches the pressing start position, the controller 44 switches the rotation of the moving motor 42 to low-speed driving. After that, the lower end of the screw guide 24 of the driver unit 20, which has further lowered, abuts against the fastened member W and stops, while the motor and the driver bit 23, which are lowered by the drive of the moving motor 42, are lowered relative to the screw guide 24, so that the driver bit 23 abuts against the screw S inside the screw guide 24. At this time, since the driver bit 23 is rotating by the drive of the fastening motor 22, its lower end engages with the screw S, and the screw S can be fastened to the fastened member W with a predetermined screw tightening torque.

[0021] During the above-mentioned screw tightening, when the screw tightening motor outputs a predetermined tightening torque, the control device 50 stops the fastening motor 22, stops the forward signal output to the controller 44, and transmits a backward signal. This causes the controller 44 to drive the moving motor 42 in the reverse direction, and raises the moving block 43 and the driver unit 20 to the standby position.

[0022] Furthermore, in the screw fastening process as described above, the control device 50 constantly monitors whether the optical sensors 271, 272 are blocked or not, and when the optical sensor 271 is blocked, it determines that the screw S has been fastened into the fastened workpiece W by several threads and can stop the vacuum generating device. This makes it possible to reduce energy consumption. Furthermore, when the fastening motor 22 outputs a predetermined screw fastening torque, it can be determined whether the screw S has been normally fastened into the fastened workpiece W from whether the optical sensor 272 is blocked or not.

[0023] During the screw tightening operation, if the workpiece W is not present at the fastening position and the moving block 43 reaches the pressing end position, the controller 44 stops driving the moving motor 42. After that, when a predetermined time has elapsed, the control device 50 stops the forward signal output to the controller 44 and sends a backward signal. This causes the controller 44 to drive the moving motor 42 in the reverse direction to raise the moving block 43 and the driver unit 20 to the standby position.

[0024] The screw fastening device 10 as described above is configured such that the controller 44 controls the driving of the moving motor 42 based on the forward and backward signals output from the control device 50, and moves the moving block 43 and the driver unit 20 toward any of the preset standby position, suction position, and pressing end position. Such a simple control configuration has the advantage that the control device 50 can be manufactured relatively inexpensively. In addition, as with the screw fastening device using an air cylinder described in Prior Art Document 1, etc., the driving of the moving motor 42 is controlled based on the forward and backward signals output from the control device 50, so that it can be easily replaced. On the other hand, since the controller 44 can move the moving block 43 at a preset predetermined speed and thrust, the driving of the moving motor 42 can be switched to a low speed and the pressing thrust just before the screw guide 24 and the screw S hit the fastened member W, thereby preventing damage to these. As a result, despite the simple control configuration, there are advantages such as the ability to perform screw fastening with a short cycle time and a small load on the fastened member W, the screw S, and the driver bit 23. Furthermore, since no air cylinder is used for raising and lowering the driver unit 20, there is an advantage that energy consumption is smaller than that of a screw fastening device that uses an air cylinder.

[0025] The specific configuration of each part of the present invention is not limited to the above, and various modifications are possible within the scope of the invention. For example, the driver bit 23 is an example of a fastening tool for fastening the screw S, and there is no problem even if it is a box bit or other fastening tool having a hexagonal fitting hole. In addition, the chuck unit 30 is not limited to the above-mentioned one, and may be any other conventional chuck unit 30, as long as the screw S can be arranged on the axis of the driver bit 23. Furthermore, in the above embodiment, the screw fastening device 10 is provided with a chuck unit 30 that holds the screw S pressure-fed from the part supply device, but is not limited thereto. For example, as detailed in JP 2023-106801 A disclosed by the present applicant, it may be configured to have a multi-joint robot that moves the screw fastening device 10 horizontally and a part supply device that can supply the screw S to a predetermined screw supply position set within the movement range of the screw fastening device 10 by the multi-joint robot. In this way, when the screw S is picked up at a predetermined screw supply position, it is preferable that the suction position is set at the height of the screw supply position. With this, when the screw tightening device reaches above the screw supply position and lowers the driver unit 20 to the suction position, the lower end of the screw guide 24 can suction and hold the screw supplied to the screw supply position. Moreover, the vacuum generating device may be provided with a pressure sensor (not shown) capable of measuring the internal pressure of the screw guide 24, and when the vacuum generating device stops at the suction position, a signal for completing suction of the screw S may be sent to the control device 50 when the air pressure in the screw guide 24 drops. By providing a pressure sensor for detecting that the screw S is suctioned and held at the lower end opening of the screw guide 24, it is possible to more reliably suction and hold the screw S. Furthermore, since the control device 50 can confirm the suction of the screw S by the pressure sensor, it can stop the retreat signal and lower the driver unit 20 immediately after the screw S is suctioned, thereby making it possible to reduce the cycle time. [Explanation of symbols]

[0026] 10 … Screw tightening device 20 ... Driver unit 21 … Housing 22 … Fastening motor 23 ... Driver bit 24 … Screw guide 30 … Chuck unit 40 … Mobile unit 41 ... Ball screw 42 ... Travel motor 43 ... moving block 44 ... Controller 50 ... Control device S: Screw W … Fastened parts

Claims

1. The fastening tool includes a driver unit that rotates a fastening tool that can be fitted with a screw, a moving unit that moves the driver unit in an axial direction of the fastening tool, and a control device that can control the driving of the driver unit and the moving unit, the moving unit includes a moving block connected to the driver unit, a ball screw with which the moving block is screwed, a moving motor that rotates the ball screw, and a controller that controls the driving of the moving motor; The screw fastening device is characterized in that the controller controls the rotation of the movement motor based on a forward signal or a backward signal sent from the control device.

2. The screw fastening device according to claim 1, characterized in that when the controller receives the forward movement signal, it advances the driver unit toward the fastened workpiece, and when the controller receives the backward movement signal, it retreats the driver unit from the fastened workpiece.

3. The driver unit has a cylindrical screw guide that accommodates the fastening tool so as to be rotatable and axially movable, A chuck unit for holding a screw is disposed on an extension line of the screw guide. The screw fastening device according to claim 2, characterized in that, when the controller receives both the forward movement signal and the retraction signal, it moves the driver unit toward a suction position set so that the screw guide is positioned just before the screw held by the chuck unit.

4. The screw fastening device according to claim 1, characterized in that the controller switches the rotational speed of the movement motor to a low speed when the tip of the advancing driver unit reaches a pressing start position set just before colliding with the fastened workpiece.

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