Screw fastening device

Abstract

To provide a screw fastening device configured to be able to easily set an operation switching point.SOLUTION: This screw fastening device comprises: a screw fastening tool 30 having a rotary-driving source 31 for rotary-driving a fastening tool 32; moving means 20 for moving the screw fastening tool 30 in an axial direction; and control means 40 for position-controlling the moving means 20. The screw fastening tool 30 is position-controlled so as to sequentially move to a standby position, a screw fastening start position, and a screw fastening completion position. The control means 40 includes a storage table in which the screw fastening completion position, a screw length, and a retreating distance can be set as control parameters in advance and stored, and an arithmetic operation unit that can arithmetically operate a screw fastening start position from the screw fastening completion position and the screw length, and the standby position from the screw fastening start position and the retreating position.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a screw tightening device for tightening a screw into a workpiece. [Background technology]

[0002] A conventional screw tightening device for tightening screws into a workpiece is disclosed in Patent Document 1. This screw tightening device is equipped with a screw tightening tool that includes a driver bit that fits with the screw and a rotary drive source that rotates the driver bit, and a drive robot that moves the screw tightening tool in three directions, and is characterized by being able to tighten screws at multiple seating positions by having the mobile robot move the screw tightening tool.

[0003] The mobile robot of the screw tightening device described above has a plurality of pre-set operation switching points, such as an origin, which is the reference position of the screw tightening tool, a receiving position where the screw is received from an external supply device, etc. In particular, during the screw tightening process, switching points are set, such as a seating position where the screw is located when it is normally fastened to the workpiece, a descent start position set above this seating position, and a bit rotation start position set between the seating position and the descent start position.After receiving the screw at the receiving position, the screw is fastened to the workpiece in the following procedure. K01: The screw tightening tool is moved to the lowering start position shown in Figure 2(a). K02: When the screw tightening tool reaches the descent start position, it waits for a predetermined time. K03: The screw tightening tool is lowered at a predetermined speed to the screw tightening start position shown in Figure 2 (b). K04: When the screw tightening tool reaches the screw tightening start position, the fastening motor is driven to rotate. K05: Switch to low speed and a specified thrust and descend to the seating position shown in Figure 2 (c). K06: When the torque of the fastening motor increases, check whether the screw tightening tool has reached the seating position shown in Figure 2 (c). K07: Raise to the evacuation position

[0004] In the operation of the screw tightening device as described above, the program is created in the following procedure. L01: Teach the starting position of the descent L02: Setting the descent speed L03: Setting the standby time L04: Teach the screw tightening start position L05: Thrust setting during descent L06: Driver start L07: Set the action when OK L08: Set the action to be taken when NG occurs L09: Timeout setting L10: Set the action to take when timeout occurs L11: Teach the evacuation position L12: High speed ascent setting

[0005] In the above-mentioned screw tightening device, the seating position is instructed by fitting a driver bit into a screw tightened in a workpiece and detecting the coordinate data at that time, while the descent start position and the screw tightening start position are instructed by reaching the seating position, moving the screw tightening tool in the axial direction of the screw, and calculating the coordinates from the amount of movement. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3797598 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, the screw fastening device fastens screws while appropriately switching its movement direction and movement speed at multiple preset switching points, so it was necessary to teach the multiple switching points before creating a control program for the screw fastening device.As a result, when fastening screws at multiple locations, even for the same screw, it was necessary to set the coordinates of multiple switching points for each fastening position, making program creation even more difficult.

[0008] Therefore, an object of the present invention is to provide a screw tightening device that can easily teach a switching point. [Means for solving the problem]

[0009] In order to achieve this object, the present invention provides a screw tightening device comprising a screw tightening tool having a rotary drive source that rotates a fastening tool that can be fitted with a screw, a moving means that moves the screw tightening tool in the axial direction of the fastening tool, and a control means that controls the position of the moving means, wherein the screw tightening tool is position-controlled to move in the following order: a standby position where it begins to move in the axial direction of the fastening tool, a screw tightening start position where the rotary drive source begins to drive, and a screw tightening completion position where the screw is seated on a workpiece; the control means is characterized by having a memory table that can store and pre-set the screw tightening completion position, the length dimension of the screw, and a retraction distance as control parameters, and an arithmetic processing unit that can calculate the screw tightening start position from the screw tightening completion position and the length dimension of the screw, and that can calculate the standby position from the screw tightening start position and the retraction distance. It is preferable that the control means has, as the memory tables, a screw data table capable of storing the length dimension and retraction distance of the screw, a seating position table capable of storing the position at the completion of screw tightening, and a switching point table that stores the standby position and the screw tightening start position, and that the control means controls the moving means based on the values ​​stored in the switching point table. Furthermore, it is preferable that the screw data table has a field in which the maximum movement speed of the screw tightening tool by the movement means can be input in advance, and that the control means controls the movement means so that the screw tightening tool does not move at a speed greater than the maximum movement speed. [Effects of the Invention]

[0010] According to the above invention, the coordinates of the descent start position and screw tightening start position are calculated based on the length dimension and retraction distance of the screw and the seating position of the screw that are input in advance, which has the advantage that the operator does not need to provide instructions every time, thereby improving work efficiency. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a side view showing the structure of a screw fastening device according to the present invention. [Figure 2] 1A and 1B are enlarged, partially cutaway side views of essential parts showing the operational switching points of the screw tightening device of the present invention, in which (a) shows the state where the screw tightening unit has reached the lowering start position, (b) shows the state where the screw tightening unit has reached the screw tightening start position, and (c) is an enlarged side view of essential parts showing the state where the screw tightening unit has reached the seated position. [Figure 3] 1A and 1B are schematic diagrams showing the configuration of the control unit of the screw fastening device according to the present invention, in which (a) shows a screw data table, (b) shows a seating position table, (c) shows a switching point table, (d) shows a limit torque table, and (e) shows a schematic diagram showing the configuration of the limit speed table. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will now be described with reference to the drawings. In Fig. 1, 10 is a screw tightening device 10 that tightens a screw S into a workpiece W. This screw tightening device 10 is composed of an articulated robot 20, a screw tightening tool 30 that is attached to the tip of the articulated robot 20 and can be moved to any position, control means 40 that controls the driving of the articulated robot 20 and the screw tightening tool 30, and a supply device (not shown) that supplies the screw S to a predetermined receiving position that is set within the range of movement of the screw tightening tool 30 by the articulated robot 20.

[0013] The articulated robot 20 of the screw fastening device 10 is composed of a plurality of arms 21 and a plurality of joint drive units 22 connecting the arms 21. The joint drive units 22 have a swing drive source for swinging the arms 21 and a rotation drive source for rotating the arms 21, and are configured to be able to move a screw fastening tool 30 fixed to the most distal arm 21 in three dimensions by driving these drive sources. The screw fastening tool 30 also has an AC servo motor 31 (hereinafter referred to as the fastening motor 31) attached to the tip of the articulated robot 20, and a driver bit 32 connected to the output shaft of the fastening motor 31 and configured to be able to rotate integrally with the fastening motor 31 by receiving the rotational drive of the fastening motor 31. The driver bit 32 has a fitting portion at its tip that can be fitted with a screw S, and an annular magnet 33 attached near the fitting portion so that the screw S fitted in the fitting portion can be magnetized and held.

[0014] The control means 40 includes a tool controller 41 that controls the drive of the fastening motor 31, a robot controller 42 that controls the drive of the articulated robot 20, and an arithmetic processing unit that performs arithmetic processing based on signals from these controllers.

[0015] The tool controller 41 is provided with a driver table that stores the output torque of the fastening motor 31 during the screw fastening process. This driver table has fields for the names of the operating parameters of the fastening motor 31 (hereinafter referred to as driver CH), and the torque when pre-tightening the screw S (hereinafter referred to as pre-tightening torque) and the torque when finally fastening (hereinafter referred to as final fastening torque), and is configured so that the pre-tightening torque and final fastening torque can be set for each driver CH.

[0016] The robot controller 42 uses characteristic points of the movement position of the screw tightening tool 30 during the screw tightening operation process as thrust and speed switching points, and performs screw tightening by setting the necessary switching points among these switching points depending on the type of screw S. For this reason, the control means 40 is provided with a screw data table 43, a seating position table 44, a switching point table 45, a limit torque table 46, and a limit speed table 47 as memory tables for storing necessary control parameters, and each of these memory tables is configured to be able to store a plurality of data. The screw fastening device 10 has the following switching points: Point O: Origin Point A: Standby position of the screw tightening tool 30 during operation (see (a) of FIG. 2) Point B: The position when the screw tightening tool 30 is moved to the point just before the tip of the screw S contacts the workpiece W (hereinafter referred to as the screw tightening start position, see FIG. 2(b)). Point C: The position where the screw is tightened when the workpiece W is in a normal state without any deflection (see (c) in Figure 2). Furthermore, point A is set to restrict the screw tightening tool 30 from returning to the origin (point O) when tightening screws sequentially on multiple workpieces W of the same shape, or when tightening multiple screws S on one workpiece W, so that the screw tightening tool 30 can quickly move on to the screw tightening operation at the next screw tightening point.

[0017] As shown in FIG. 3(a), the screw data table 43 has fields for a screw parameter 431, a driver CH 432 of the tool controller 41, a length 433 of the screw S to be fastened (hereinafter referred to as the screw length 433), a distance 434 (hereinafter referred to as the retraction distance 434) at which the screw S and the driver bit 32 do not come into contact with parts around the fastening point, a maximum speed 435 of the articulated robot 20, a pressing force 436 (hereinafter referred to as the thrust force 436) at which the screw S does not come out when fastening, and a time 437 per cycle (hereinafter referred to as the timeout 437). The screw data table 43 is configured so that the driver CH 432, the screw length 433, the retraction distance 434, the maximum speed 435, the pressing force 436, and the timeout 437 can be set for each screw parameter 431.

[0018] 3(b), coordinate data of the position of the screw tightening tool 30 when the screw S is normally tightened (hereinafter referred to as the seating position) is set in the seating position table 44. Note that this seating position is set by a conventionally known method, such as a method in which an operator operates the articulated robot 20 and directly teaches the screw tightening tool 30 by moving it so that the driver bit 32 fits into the screw S tightened in the workpiece W, or a method in which the screw tightening device 10 is operated in a simulation and the coordinate data of the seating position is calculated from the amount of movement.

[0019] In the switching point table 45, the coordinates and orientations of the screw tightening tool 30 when it reaches the point O, the point A, the point B, and the point C are set as shown in FIG. 3(c).

[0020] In the limit torque table 46, as shown in (d) of Figure 3, a first limit torque 461 which is the driving torque of the articulated robot 20 between point A and point B, a second limit torque 462 which is the driving torque of the articulated robot 20 between point B and point C, and a third limit torque 463 which is the driving torque of the articulated robot 20 between point C and point A are set.

[0021] In the speed limit table 47, as shown in (e) of Figure 3, a first speed 471 which is the driving speed between point A and point B, a second speed 472 which is the driving speed between point B and point C, and a third speed 473 which is the driving speed between point C and point A are set.

[0022] The calculation processing unit of the control unit also has a screw tightening program creation function, which is configured to calculate various parameters to be set in the switching point table 45, the limit torque table 46, and the limit speed table 47 based on the values ​​of the screw data table 43 and the seating position table 44 that are set in advance by the operator, temporarily set these tables, and create a screw tightening program from the values ​​of the switching point table 45, the limit torque table 46, and the limit speed table 47.

[0023] The operation of the screw tightening program creation function will be described below. When the operator instructs the seating position and selects the screw parameters 431 to be used, and then executes the screw tightening program creation function, the screw tightening program creation function temporarily sets, at point C in the switching point table 45, the position and orientation of the screw tightening tool 30 when the screw S set in the seating position table 44 is properly tightened. Point B is set to a position spaced a predetermined distance T1 from point C in the axial direction of the screw tightening tool 30. The distance T1 from point C to point B is set to the sum of the length 433 of the screw S set in the screw data table 43 and a fixed value α. The fixed value α is set to a value sufficiently smaller than the difference between the retraction distance 434 and the length 433 of the screw S so that the sum of the fixed value α and the length 433 of the screw S is sufficiently smaller than the retraction distance 434. Point A is set to a position spaced a predetermined distance T2 from point B in the axial direction of the screw tightening tool 30. The distance T2 from point B to point A is set to the same dimension as the retraction distance 434 set in the screw data table 43. Furthermore, the pressing force 436 set in the screw data table 43 is set in the second limit torque 462 of the limit torque table 46. Furthermore, a value lower than the maximum speed 435 of the articulated robot 20 set in the screw data table 43 is set in the first speed 471 of the limit speed table 47. Note that the first limit torque 461 and the third limit torque 463 of the limit torque table 46 are set to values ​​lower than the second limit torque 462. Furthermore, the second speed 472 and the third speed 473 of the limit speed table 47 are set to values ​​that are lower than the first speed 471 and that allow the screw tightening process to be completed within the timeout 437 set in the screw data table 43.

[0024] As described above, the screw tightening program creation function creates a screw tightening program based on the various parameters calculated in the switching point table 45, the limit torque table 46, and the limit speed table 47. This screw tightening program is configured so that the screw tightening device 10, which receives the screw S from the component supply device, tightens the screw in the following order: D01: The screw tightening tool 30 is moved to point A. D02: When the screw tightening tool 30 reaches point A, it waits for a predetermined time. D03: The screw tightening tool 30 is moved to point B at the first speed 471 and the first limit torque 461. D04: When the screw tightening tool 30 reaches point B, the fastening motor 31 is driven to rotate. D05: Switch to the second speed 472 and the second limit torque 462 and move to point C. D06: When the torque of the fastening motor 31 increases, check whether the screw tightening tool 30 has reached point C. D07: The screw tightening tool 30 is moved to point A at the third speed 473 and the third limit torque 463.

[0025] In this case, as described above, it is only necessary to input the parameters that change depending on the screw S to be fastened or the fastening location, such as the screw parameter 431 and the seating position, so there is no need to set error conditions during movement as with the conventional screw fastening device 10, and a screw fastening program can be easily created.

[0026] Next, the operation of the screw fastening device 10 configured as described above will be described. When a start signal is input, the control means 40 drives an external supply device to supply the screw S to a predetermined receiving position, and drives the articulated robot 20 to move the screw tightening tool 30 above the receiving position. When the screw tightening tool 30 reaches above the receiving position, the control means 40 drives the fastening motor 31 to rotate the driver bit 32 with a pre-tightening torque and lowers the screw tightening tool 30 until the driver bit 32 abuts against the screw S. This causes the lower end of the driver bit 32 to engage with the screw S. The screw S engaged with the driver bit 32 is magnetized and held in the engaging portion by the annular magnet 33 attached to the driver bit 32.

[0027] After the screw S is held by the driver bit 32 as described above, the control means 40 stops the fastening motor 31 and drives the articulated robot 20 to move the screw tightening tool 30 toward point A. When the screw tightening tool 30 reaches point A, the control means 40 drives the articulated robot 20 to lower the screw tightening tool 30 at high speed toward point B at a first speed 471 and a first limit torque 461. When the screw tightening tool 30 reaches point B, the fastening motor 31 is driven to rotate the driver bit 32, and the descent of the screw tightening tool 30 is switched from the first speed 471 and the first limit torque 461 to a second speed 472 and a second limit torque 462. At this time, point B is a distance T1 from point C, which is the length 433 of the screw S set in the screw data table 43 plus the fixed value α, preventing the screw S from colliding with the workpiece while maintaining the first speed 471. Therefore, the screw S rotates integrally with the driver bit 32 while descending toward the workpiece at a low speed and being fastened to the workpiece W. After that, when the screw S is seated on the workpiece W, the fastening motor 31 switches from the pre-tightening torque to the final fastening torque to perform the final fastening. When the fastening motor 31 outputs a predetermined tightening torque, the control means 40 checks, based on a signal from the articulated robot 20, whether the screw tightening tool 30 has reached the seating position. If the screw tightening tool 30 has reached the seating position, it determines that the screw S has been properly fastened. However, if the screw tightening tool 30 has reached the seating position, it determines that the screw S has not been seated. The control means 40 then drives the articulated robot 20 again to raise the screw tightening tool 30 to point A at the third speed 473 and the third limit torque 463.

[0028] Next, a procedure for creating a screw tightening program when tightening the screw S at the second tightening position will be described. After the operator instructs the second seating position and selects the screw parameters 431 to be used, the program creation function is executed again. A screw tightening program for the screw S for the second seating position is created in the same manner as the screw tightening program for the first seating position described above. Because the screw parameters 431 and the seating position are stored as separate data, when the same screw S is to be fastened in different fastening locations, a screw tightening program can be created in two steps: selecting the screw parameters 431 to be used and setting a new seating position. This eliminates the need to input the screw S parameters and error conditions, etc., every time the fastening location is changed, as in the past, and allows for easy creation of a screw tightening program. Furthermore, because the screw data table 43, which stores the screw parameters 431, is provided separately from the switching point table 45, the limit torque table 46, and the limit speed table 47, which form the basis of the screw tightening program, it is also possible to fine-tune the screw tightening program alone. This has the advantage of allowing fine adjustments to the operation switching points, etc., for each seating position while preventing changes to the screw parameters 431, which form the basis of the screw tightening program.

[0029] The screw fastening device 10 according to the present invention is not limited to the above-described structure and may be modified in various ways without departing from the spirit of the invention. For example, the articulated robot 20 is an example of a moving means. It is acceptable to use other moving means, such as a single-axis moving means that moves the screw fastening tool 30 only in the axial direction or a multi-axis moving means that can move the screw fastening tool 30 in multiple directions. Furthermore, the driver bit 32 is preferably replaced appropriately depending on the screw S to be fastened. The driver bit 32 may have a different shape, such as a hexalobular or rectangular tip, or may be a box bit or other fastening tool. Furthermore, while the screw fastening device 10 described above is configured to retrieve the screw S supplied from the supply device to a predetermined receiving position, this is not limited thereto. For example, as detailed in Japanese Patent Application Publication No. 2018-079554 disclosed by the present applicant, a screw fastening device may also be provided with a chuck unit on the axis of the driver bit 32 that can temporarily hold the screw S pressure-fed from the supply device. [Explanation of symbols]

[0030] 10...Screw tightening device 20...Transportation 30...Screw tightening tool 31 ... Fastening motor 32... Driver bit 40... Control means 41 ... Tool controller 42...Robot controller S...screw W... Work

Claims

1. a screw tightening tool having a rotation drive source that rotates a fastening tool that can be fitted with a screw; a moving means for moving the screw tightening tool in the axial direction of the fastening tool; a control means for controlling the position of the moving means, In a screw tightening device, the screw tightening tool is positionally controlled to move in the following order: a standby position where it starts to move in the axial direction of the fastening tool; a screw tightening start position where the rotation drive source starts to drive; and a screw tightening completion position where the screw is seated on a workpiece. The control means a storage table in which the screw tightening completion position, the length of the screw, and the retraction distance are set and stored in advance as control parameters; A screw tightening device characterized by having an arithmetic processing unit that can calculate a screw tightening start position from the screw tightening completion position and the length dimension of the screw, and that can calculate the waiting position from the screw tightening start position and the retraction distance.

2. the control means has, as the storage tables, a screw data table capable of storing the length dimension and retraction distance of the screw, a seating position table capable of storing the position at the completion of screw tightening, and a switching point table that stores the standby position and the screw tightening start position, 2. The screw tightening device according to claim 1, wherein the moving means is controlled based on values ​​stored in the switching point table.

3. The screw data table is provided with a field in which a maximum movement speed of the screw tightening tool by the movement means can be input in advance, 3. The screw fastening device according to claim 2, wherein the control means controls the movement means so that the screw fastening tool does not move at a speed equal to or greater than the maximum movement speed.

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