Screw tightening device

Abstract

To provide a screw tightening device which can control a position of a screw and a screw pressing force, reduces a time needed for screw tightening, and inhibits occurrence of defects.SOLUTION: A screw tightening device includes: a rotary tool unit 10 having a rotation output shaft 45 of a first motor 12, a rotary tool 11, and a rotary tool attachment part 18 which connects the rotation output shaft 45 with the rotary tool 11; a tool position displacement part 3 which moves the rotary tool unit along a rotation axis direction; a control unit 2 which controls the first motor and the tool position displacement part; a first distance measurement part 51 which measures a distance between a screw 90 and an object to be fastened (a fastened object) 99; and a second distance measurement part 52 which measures positions of the rotation output shaft and the rotary tool attachment part. The rotation output shaft and the rotary tool attachment part slide in the rotation axis direction and are connected by a flexible connection member 38. The control unit controls, based on measurement values from the first distance measurement part and the second distance measurement part, a screw pressing force P and a position of the rotary tool with the first motor and the tool position displacement part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] One control method for screw tightening devices is a torque control method that ends temporary tightening based on the torque applied to the screw. Patent Document 1 describes, as an example of a screw tightening device using a torque control method, a screw tightening device that has a rotary tool, a first motor, a second motor, and a control unit. The rotary tool rotates the screw. The first motor rotates the rotary tool. The second motor moves the rotary tool in the axial direction. The control unit sets the first motor to a predetermined rotation speed and causes the second motor to move the rotary tool until the torque reaches a threshold torque, thereby executing a first step for screwing the screw into the screw hole, and a second step for increasing the torque until it reaches a predetermined torque for final tightening of the screw. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 261021 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the screw tightening device described in Patent Document 1, the faster the screw is tightened into the screw hole (pre-tightening), the more likely it is that a delay will occur between the detection that the torque has reached a specified value and the cessation of pre-tightening. This can result in an excessively large torque being applied to the screw, which can cause defects such as deformation of the screw and the object being fastened. This has led to the problem that it is difficult to reduce the time required for screw tightening while suppressing defects in screw tightening.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a screw tightening device that has a mechanism that can constantly control the screw position and screw pressing force, and that can reduce the time required for screw tightening while suppressing the occurrence of defects in screw tightening. [Means for solving the problem]

[0006] The screw tightening device according to the present disclosure comprises a rotary tool unit having a motor, a rotary output shaft of the motor, a rotary tool that rotates a screw, and a rotary tool mounting part that connects the rotary output shaft and the rotary tool, a tool position displacement part that moves the rotary tool unit along the direction of the rotation axis, a control part that controls the motor and the tool position displacement part, a first distance measurement part that measures the distance between the screw and a workpiece to which the screw is attached, and a second distance measurement part that measures the relative position of the rotary output shaft and the rotary tool mounting part, wherein the rotary output shaft and the rotary tool mounting part slide in the direction of the rotation axis and are connected by a flexible connecting member, and the control part controls the pressing force of the screw and the position of the rotary tool using the motor and the tool position displacement part based on the measured values ​​from the first distance measurement part and the second distance measurement part. [Effects of the Invention]

[0007] The screw tightening device according to the present disclosure can reduce the time required for screw tightening while suppressing the occurrence of defects during screw tightening. Furthermore, the screw tightening operation can be performed while exerting the desired screw pressing force during both preliminary tightening and final tightening. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing the configuration of a main part of a screw fastening device according to a first embodiment. [Figure 2] 1 is an enlarged cross-sectional view showing the configuration of a main part of a screw fastening device according to a first embodiment. [Figure 3]1 is an enlarged side view showing the configuration of a main part of a screw fastening device according to a first embodiment. [Figure 4] 1 is a block diagram showing a schematic configuration of a screw fastening device according to a first embodiment. [Figure 5] 4 is a flow chart showing an outline of the operation of the screw fastening device according to the first embodiment. [Figure 6] 10 is a schematic diagram showing the operation of the screw fastening device according to the second embodiment. FIG. [Figure 7] 10 is a diagram showing the relationship between time and the amount of descent in the screw fastening device according to the second embodiment. FIG. [Figure 8] 10 is a flow chart schematically showing the operation of the screw fastening device according to the fourth embodiment. [Figure 9] 10 is a flow chart showing an outline of the operation of the screw fastening device according to the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Embodiment 1 The configuration of a screw fastening device 100 according to embodiment 1 will be described using Fig. 1 to Fig. 4. Fig. 1 is a cross-sectional view showing the configuration of a main part of the screw fastening device according to embodiment 1. Fig. 2 is an enlarged cross-sectional view showing region I in Fig. 1, and Fig. 3 is an enlarged side view showing region I in Fig. 1. The cross section shown in Fig. 1 is a cross section including rotation axis A. Fig. 4 is a block diagram showing a schematic configuration of the screw fastening device 100.

[0010] As shown in FIG. 1, the screw fastening device 100 mainly has a screw fastening unit 1 and a unit position displacement section 4. The screw fastening unit 1 moves the screw 90 while rotating the screw 90. The unit position displacement section 4 moves the screw fastening unit 1. The screw fastening device 100 fastens the screw 90 into a fastened object 99. A female thread 98 is provided on a main surface 97 of the fastened object 99. The screw 90 has a head 91 and a male thread portion 92. The male thread portion 92 is connected to the head 91. The head 91 forms a bearing surface 93. The bearing surface 93 is a surface that contacts the main surface 97.

[0011] The screw tightening unit 1 mainly has a rotary tool unit 10, a tool position displacement unit 3, a chuck unit 6, and a first distance measurement unit 51. The rotary tool unit 10 rotates the screw 90. The rotary tool unit 10 is fixed to the tool position displacement unit 3. The tool position displacement unit 3 is fixed to the unit position displacement unit 4. The tool position displacement unit 3 moves the rotary tool unit 10. The chuck unit 6 is fixed to the unit position displacement unit 4. The chuck unit 6 is spaced apart from the tool position displacement unit 3. The chuck unit 6 holds the screw 90. The first distance measurement unit 51 is fixed to the unit position displacement unit 4. The first distance measurement unit 51 measures the distance between the screw 90 and the workpiece 99.

[0012] The rotary tool unit 10 has a rotary tool 11, a first motor 12, a rotary output shaft 45, a rotary tool attachment portion 18, a linear bushing 14, and a motor fixing portion 19. The first motor 12 rotates the rotary output shaft 45. The first motor 12 is, for example, a servo motor. The rotary tool 11 is fixed to the rotary tool attachment portion 18. The first motor 12 and the linear bushing 14 are fixed to the motor fixing portion 19. The motor fixing portion 19 is fixed to the tool position displacement portion 3.

[0013] The rotary tool 11 can be engaged with the head 91 of the screw 90. The rotary tool 11 is rod-shaped. The rotary tool 11 is a tool such as a Phillips or flathead screwdriver or a hexagonal wrench. The direction from the rotary tool 11 toward the workpiece 99 is defined as a first direction 101. Conversely, the direction from the workpiece 99 toward the rotary tool 11 is defined as a second direction 102. The second direction 102 is opposite to the first direction 101. A rotation axis A of the rotary tool 11 extends along the first direction 101.

[0014] A connecting member 38 that is flexible in the first direction 101 is provided between the rotary output shaft 45 and the rotary tool mounting portion 18. The rotary output shaft 45 and the rotary tool mounting portion 18 are fixed relative to each other in the direction of rotation about the rotation axis A, and are supported so as to be able to slide relative to each other along the first direction 101. From another perspective, the rotation of the rotary output shaft 45 can be transmitted to the rotary tool mounting portion 18, and the displacement of the rotary output shaft 45 in the first direction 101 can be transmitted to the rotary tool mounting portion 18 via the connecting member 38.

[0015] As shown in FIGS. 2(a) and 2(b), a sliding pin 34 is fixed to the rotation output shaft 45 in a direction perpendicular to the first direction 101, and the rotary tool mounting part 18 is provided with a sliding groove 35 extending in the first direction 101. When the sliding pin 34 and the sliding groove 35 engage with each other, the rotation output shaft 45 and the rotary tool mounting part 18 slide relative to each other in the first direction 101, and rotation of the rotation output shaft 45 can be transmitted to the rotary tool mounting part 18 via the sliding pin 34. The connecting member 38 is a spring member such as a coil spring or a leaf spring. The connecting member 38 may have a structure that generates a reaction force by contracting in the first direction 101.

[0016] The linear bushing 14 holds the rotary tool attachment portion 18 so that the rotary tool attachment portion 18 can slide along a first direction 101 and rotate around a rotation axis A. The linear bushing 14 has an annular shape.

[0017] The tool position displacement unit 3 is a linear motion mechanism such as an electric actuator. The tool position displacement unit 3 has a second motor 31, a first linear motion unit 32, and a first slide unit 33. The second motor 31 is, for example, a servo motor. The first linear motion unit 32 converts the rotational motion generated by the second motor 31 into linear motion. The first linear motion unit 32 has, for example, a first ball screw (not shown) and a first linear guide (not shown). The first ball screw is connected to the second motor 31. The first slide unit 33 is attached to each of the first ball screw and the first linear guide. The first slide unit 33 is attached to the rotary tool unit 10. The first slide unit 33 is movable along a first direction 101.

[0018] The chuck unit 6 is provided in a first direction 101 relative to the first motor 12. The chuck unit 6 is spaced apart from the rotary tool unit 10. The chuck unit 6 has a first chuck 61 and a second chuck 62. The first chuck 61 and the second chuck 62 are fixed to the unit position displacement unit 4.

[0019] The first chuck 61 can hold the screw 90 at a position where the bearing surface 92 of the screw 90 and the rotation axis A are perpendicular to each other and the rotation axis A passes through the center axis of the male thread portion 92. The first chuck 61 adjusts the posture of the screw 90. The first chuck 61 holds the head 91 of the screw 90 so that it faces the second direction 102 and the male thread portion 92 so that it faces the first direction 101. The first chuck 61 is made up of two or more conical chucks with a slope that narrows in the first direction 101.

[0020] The second chuck 62 is provided in a first direction 101 relative to the first chuck 61. The second chuck 62 is spaced apart from the first chuck 61. The second chuck 62 supports the screw 90 at a seating surface 93. The second chuck 62 is located between the first chuck 61 and the workpiece 99.

[0021] The first distance measurement unit 51 is fixed to the unit position displacement unit 4. The first distance measurement unit 51 measures the distance (workpiece distance D) between the bearing surface 93 and the main surface 97 in the first direction 101. The workpiece distance D is the distance between the bearing surface 93 and the main surface 97 when the screw 90 is supported by the second chuck 62.

[0022] The second distance measurement unit 52 is fixed to the motor fixing unit 19. The second distance measurement unit 52 measures the relative distance L1 between the rotation output shaft 45 and the rotary tool mounting unit 18 in the first direction 101. Here, a laser displacement meter is used as the second distance measurement unit 52.

[0023] When the rotary tool 11 is engaged with the screw 90, the position of the screw 90 in a first direction 101 is restricted, and the screw 90 is in contact with the workpiece 99, when the tool position displacement unit 3 moves in the first direction 101, the rotary tool 11 engaged with the screw 90 and the rotary tool mounting unit 18 to which the rotary tool 11 is fixed cannot move in the first direction because their positions are restricted.

[0024] On the other hand, the rotation output shaft 45 moves in the first direction 101 because the connecting member 38 contracts in the first direction 101. A difference occurs between the amount of movement of the rotation output shaft 45 and the rotary tool attachment part 18 in the first direction 101, and by measuring the change in the relative distance L1 using the second distance measuring part 52, the amount of contraction L2 of the connecting member 38 along the first direction 101 can be obtained.

[0025] Furthermore, due to the amount of contraction L2 occurring in the connecting member 38, a reaction force (pressing force P) is generated in the first direction 101 on each of the rotation output shaft 45 and the rotary tool mounting portion 18. By measuring the relationship between the amount of contraction L2 of the connecting member 38 and the pressing force P in advance, the output of the second distance measuring unit 52 can be converted into the pressing force P.

[0026] In addition, the second distance measurement unit 52 can measure the difference in the amount of movement in the first direction 101 between the tool position displacement unit 3 and the screw 90, so the current position of the screw 90 in the first direction 101 can be calculated from the output of the second distance measurement unit 52.

[0027] The unit position displacement unit 4 is a linear motion mechanism such as an electric actuator. The unit position displacement unit 4 has a third motor 41, a second linear motion unit 42, and a second slide unit 43. The third motor 41 is, for example, a servo motor. The second linear motion unit 42 converts the rotational motion generated by the third motor 41 into linear motion. The second linear motion unit 42 has a second ball screw (not shown) and a second linear guide (not shown). The second ball screw is connected to the third motor 41. The second slide unit 43 is attached to both the second ball screw and the second linear guide. The second slide unit 43 is fixed to both the tool position displacement unit 3 and the chuck unit 6. The second slide unit 43 is movable along the first direction 101.

[0028] A block diagram showing a schematic configuration of the screw fastening device 100 is shown in Fig. 4. As shown in Fig. 4, the screw fastening device 100 has a control unit 2. The control unit 2 is electrically connected to a first distance measurement unit 51, a second distance measurement unit 52, a first motor 12, a tool position displacement unit 3, and a unit position displacement unit 4. The control unit 2 is formed by, for example, a programmable logic controller and a servo driver.

[0029] The control unit 2 can control and operate the first motor 12 by outputting a signal to the first motor 12. The control unit 2 can rotate the rotary tool 11 by outputting a signal to the first motor 12. Specifically, the control unit 2 can control the start and stop of rotation of the rotary tool 11, the amount of rotation of the rotary tool 11, the angular velocity and angular acceleration of the rotary tool 11, etc. The control unit 2 can also control the current supplied to the first motor 12.

[0030] The control unit 2 can control and operate the tool position displacement unit 3 by outputting a signal to the tool position displacement unit 3. The control unit 2 can move the rotary tool unit 10 along the first direction 101 by outputting a signal to the tool position displacement unit 3. Specifically, the control unit 2 can control the start and stop of movement of the rotary tool unit 10, the movement distance of the rotary tool unit 10, the speed of the rotary tool unit 10, the acceleration of the rotary tool unit 10, etc. The control unit 2 can also control the current supplied to the second motor 31.

[0031] The control unit 2 can control and operate the unit position displacement unit 4 by outputting a signal to the unit position displacement unit 4. The control unit 2 can move the screw tightening unit 1 along the first direction 101 by outputting a signal to the unit position displacement unit 4. The control unit 2 can control the start of movement of the screw tightening unit 1, the stop of movement of the screw tightening unit 1, the movement distance of the screw tightening unit 1, the speed of the screw tightening unit 1, and the acceleration of the screw tightening unit 1. The control unit 2 can also control the current supplied to the third motor 41.

[0032] The control unit 2 has an input unit 21, a memory unit 22, a calculation unit 23, and an output unit 24. The input unit 21 receives signals output from the first distance measurement unit 51, the second distance measurement unit 52, the first motor 12, the tool position displacement unit 3, and the unit position displacement unit 4. The memory unit 22 stores the signals input to the input unit 21.

[0033] The calculation unit 23 performs a predetermined calculation based on the data input to the input unit 21 and the data stored in the memory unit 22. The output unit 24 outputs control commands to each of the first motor 12, the tool position displacement unit 3, and the unit position displacement unit 4.

[0034] Next, the operation of the screw fastening device 100 according to the first embodiment will be described with reference to Fig. 5. Fig. 5 is a flow chart that schematically shows the operation of the screw fastening device 100 according to the first embodiment.

[0035] First, the screw 90 is supplied to the chuck unit 6 of the screw fastening device 100 (step S501). The chuck unit 6 orients the head 91 of the screw 90 in the second direction 102 and the male thread portion 92 in the first direction 101, with the bearing surface 93 supported by the second chuck 62 and held by the first chuck 61.

[0036] Subsequently, the rotary tool unit 10 is moved in the first direction 101 (step S502), and the rotary tool 11 of the rotary tool unit 10 is fitted onto the screw 90 (step S503).

[0037] Next, the screw 90 is pressed against the second chuck 62 (step S504), and the second distance measurement unit 52 measures the distance L1 to the uppermost measurement surface 15 of the rotary tool attachment unit 18 as the relative distance between the rotary output shaft 45 and the rotary tool attachment unit 18 (step S505). The amount of contraction L2 of the connecting member 38 is obtained from the measured distance L1.

[0038] In parallel with the processes from step S502 to step S505, first, the first distance measurement unit 51 measures the fastened object distance D, which is the distance between the bearing surface 93 of the screw 90 and the main surface 97 of the fastened object 99 (step S506).

[0039] Next, the moving distance of the screw tightening unit 1 is calculated (step S507), and the screw tightening unit 1 is moved at high speed until just before the screw 90 and the workpiece 99 come into contact with each other (step S508).

[0040] Next, the screw tightening unit 1 is moved at a low speed until the screw 90 and the workpiece 99 come into contact with each other (step S509), and when the screw 90 and the workpiece 99 come into contact with each other, the movement of the screw tightening unit 1 is stopped (step S510).

[0041] Next, the movement distance of the screw tightening unit 1 is stored (step S511), and then the movement distance of the rotary tool is calculated (step S512).

[0042] Next, the screw 90 is temporarily tightened until the bearing surface 93 of the screw 90 and the main surface 97 of the workpiece 99 are just about to come into contact with each other (step S513).

[0043] Finally, the screws 90 are tightened until the specified torque is reached (step S514).

[0044] In conventional screw tightening devices, when pre-tightening is terminated based on the torque applied to the screw 90, the head 91 of the screw 90 is in contact with the workpiece 99 at the time pre-tightening is terminated. For this reason, if there is a delay between detecting the torque applied to the screw 90 and stopping pre-tightening, the torque applied to the screw may become excessively large (torque over), which may cause a defect in which the screw 90 and the workpiece 99 are deformed. In particular, if pre-tightening is performed too quickly, defects in which the screw 90 and the workpiece 99 are deformed are more likely to occur.

[0045] In the screw fastening device 100 according to the first embodiment of the present disclosure, the control unit 2 provisionally fastens the screw 90 to the workpiece 99 based on the outputs of the first distance measurement unit 51 and the second distance measurement unit 52 so that the head 91 of the screw 90 does not come into contact with the workpiece 99. Therefore, even if the provisional fastening is performed quickly, the head 91 of the screw 90 can be prevented from coming into contact with the workpiece 99. This makes it possible to prevent defects such as deformation of the screw 90 and the workpiece 99. As a result, it is possible to reduce the time required for screw fastening while preventing defects from occurring during screw fastening.

[0046] Furthermore, in the screw fastening device 100 according to the first embodiment, by measuring the contraction amount L2 of the connecting member 38 with the second distance measurement unit 52, it is possible to simultaneously measure the pressing force P applied to the screw 90 and its position in the first direction 101 using only one mechanism from the output from the second distance measurement unit 52. Compared to a case where a force meter for measuring the pressing force P and a displacement meter for measuring the position of the screw 90 are separately provided, the screw fastening device 100 can be simplified and made lighter.

[0047] Furthermore, in the screw fastening device 100 according to the first embodiment, the pressing force P of the screw 90 can be controlled simply by controlling the tool position displacement unit 3 based on the output of the second distance measurement unit 52. Generally, to control the pressing force, a motor capable of controlling the pressing force, such as a servo motor, must be used and a complex control system must be constructed, but the screw fastening device 100 does not require additional components or complex control such as motor torque control.

[0048] Furthermore, in the screw fastening device 100 according to the first embodiment, even if the pressing force P fluctuates due to vibrations during pre-tightening at high speed, the connecting member 38 is flexible and can absorb the vibrations and continue to exert a stable pressing force during pre-tightening. This prevents defects such as the rotary tool 11 lifting off the screw 90 due to vibrations during pre-tightening, making the screw 90 unable to rotate.

[0049] Furthermore, in the screw fastening device 100 according to the first embodiment, in the process of fitting the screw 90 and the rotary tool 11, the tool position displacement unit 3 is controlled in advance, and the rotary tool 11 exerts a pressing force P on the screw 90, pressing the rotary tool 11 against the screw 90. This allows the rotary tool 11 to be fitted to the screw 90 simply by rotating the rotary tool 11. The pressing force P of the rotary tool 11 is obtained as a reaction force against the contraction amount L2 of the connecting member 38, and therefore, as the rotary tool 11 rotates and the connecting member 38 expands in the first direction 101, the rotary tool 11 drops into the fitting portion of the head 91, thereby achieving fitting. Control of the displacement unit is not necessary, and stable fitting can be achieved by exerting the pressing force required for fitting.

[0050] Although the configuration of the screw fastening device 100 according to the first embodiment has been described, the configuration of the screw fastening device 100 is not limited to the above configuration. For example, in addition to a laser displacement meter, an ultrasonic displacement meter, a contact displacement meter, or a capacitance displacement meter can be used as the second distance measurement unit 52. The second distance measurement unit 52 can also be configured inside the rotary output shaft 45 and the rotary tool mounting unit 18. Another method is to determine the position by providing slits and patterns in the rotary tool mounting unit 18 and reading them with the second distance measurement unit 52 fixed to the motor fixing unit 19.

[0051] The memory unit 22 may also store in advance the pressing force P required for each of the multiple screws 90. The control unit 2 reads out the pressing force P required for the screw 90 to be fastened from the memory unit 22. This allows multiple types of screws 90 to be fastened using a single screw fastening device 100, even if the type of screw 90 to be fastened is changed.

[0052] Furthermore, the tool position displacement unit 3 may be a drive mechanism such as an air cylinder, a hydraulic cylinder, or an articulated robot. When the tool position displacement unit 3 is an articulated robot, the posture of the rotary tool unit 10 can be changed. This allows the screw tightening to be performed with a single screw tightening device 100 even when the workpiece 99 has multiple female threads 98 and the directions in which the multiple female threads 98 extend are different.

[0053] As described above, the screw fastening device 100 according to the first embodiment includes the rotary tool unit 10 having the first motor 12, the rotary output shaft 45 of the first motor 12, the rotary tool 11 that rotates the screw 90, and the rotary tool attachment part 18 that connects the rotary output shaft 45 and the rotary tool 11, the tool position displacement part 3 that moves the rotary tool unit 10 along the direction of the rotation axis, the control part 2 that controls the first motor 12 and the tool position displacement part 3, the first distance measurement part 51 that measures the distance between the screw 90 and the workpiece 99 to which the screw 90 is attached, and the rotary tool attachment part 18 that connects the rotary output shaft 45 and the rotary tool 11. The rotary output shaft 45 and the rotary tool attachment part 18 slide in the direction of the rotation axis and are connected by a flexible connecting member 38. The control part 2 controls the pressing force of the screw 90 and the position of the rotary tool 11 using the first motor 12 and the tool position displacement part 3 based on the measurements from the first distance measurement part 51 and the second distance measurement part 52. This makes it possible to provide a screw tightening device that can reduce the time required for screw tightening and suppress the occurrence of defects in screw tightening. Furthermore, the screw tightening operation can be performed while exerting the desired screw pressing force during both preliminary tightening and final tightening.

[0054] Embodiment 2 The screw fastening device 100 according to the second embodiment is characterized in that, during pre-tightening, the speed at which the rotation output shaft 45 descends in the first direction 101 is controlled to be faster than the speed at which the screw 90 descends in the first direction 101. The other configurations of the screw fastening device 100 according to the second embodiment are the same as those of the screw fastening device 100 according to the first embodiment, and corresponding parts are given the same reference numerals and their description will be omitted.

[0055] FIG. 6 is a schematic diagram showing the operation of the screw fastening device according to the second embodiment. FIG. 7 is a diagram showing the relationship between time t and descent amount z in the screw fastening device according to the second embodiment. As shown in FIG. 6, in the pre-tightening process, the tool position displacement unit 3 is moved in the first direction 101, thereby moving the rotation output shaft 45 in the first direction 101. At this time, the tool position displacement unit 3 is displaced until the pressing force required for pre-tightening is reached. After the pressing force required for pre-tightening is exerted, the pre-tightening process begins. The tool position displacement unit 3 descends to a target descent position based on the outputs of the first distance measurement unit 51 and the second distance measurement unit 52. At this time, the descent speed V2 of the rotation output shaft 45 is controlled to be faster than the descent speed V1 of the screw 90. As a result, the rotation output shaft 45 descends to the target descent position faster than the screw 90, as shown in FIG. 7.

[0056] From another perspective, this means that the amount of contraction L2 of the connecting member 38 becomes larger during pre-tightening than at the start of pre-tightening because the rotation output shaft 45 descends before the screw 90 and the rotary tool attachment portion 18. As a result, during pre-tightening, the screw 90 is tightened while constantly exerting a pressing force greater than the pressing force P required for the initial pre-tightening.

[0057] As a result, with the screw fastening device 100 according to the second embodiment, the pressing force, which fluctuates due to vibrations and the like, can be constantly maintained at or above the minimum required pressing force during pre-tightening. This makes it possible to prevent defects such as the rotary tool 11 coming off the screw 90 due to insufficient pressing force. Furthermore, during pre-tightening when the rotary tool 11 rotates at high speed, real-time position control and rotation control are not required, which allows for even faster device operation.

[0058] Furthermore, in the screw fastening device 100 according to the second embodiment, even if the type of screw 90 to be fastened is changed, it is possible to accommodate this by changing the pressing force control value and the connecting member 38.

[0059] As described above, in the screw fastening device 100 according to the second embodiment, the control unit 2 controls the rotation output shaft 45 to move the screw 90 closer to the workpiece 99 at a speed faster than the screw 90 based on the outputs from the first distance measurement unit 51 and the second distance measurement unit 52. This allows the pressing force, which may fluctuate due to vibration or other factors, to be maintained at a minimum required level during pre-tightening, thereby preventing defects such as the rotary tool becoming disengaged from the screw due to insufficient pressing force. Furthermore, real-time position and rotation control is not required during pre-tightening, when the rotary tool rotates at high speed, allowing for increased device speed. Furthermore, even if the type of screw to be fastened is changed, this can be accommodated by changing the pressing force control value and the connecting member.

[0060] Embodiment 3 The screw fastening device 100 according to the third embodiment is characterized in that it uses a non-contact distance measuring device for the second distance measuring unit 52. Examples of non-contact displacement meters include a laser displacement meter, a magnetic displacement meter, a capacitance displacement meter, and an ultrasonic displacement meter. The other configuration of the screw fastening device 100 according to the third embodiment is the same as that of the screw fastening device 100 according to the first embodiment, and corresponding parts are designated by the same reference numerals and their description will be omitted.

[0061] The screw tightening device 100 according to the third embodiment uses a non-contact displacement meter, which improves responsiveness compared to a contact displacement meter. This allows for faster screw tightening. Furthermore, if there is a contact area, it is susceptible to the influence of the measurement surface, for example, if a foreign object gets caught between the contact area and the screw, which can cause the accuracy of the pressing force and screw position to deteriorate. Therefore, the use of a non-contact displacement meter improves the accuracy of the pressing force and screw position.

[0062] As described above, according to the screw tightening device 100 of the third embodiment, the second distance measurement unit uses a non-contact position measurement method, which improves responsiveness compared to a contact-type displacement meter and can also be used when speeding up screw tightening. In addition, the accuracy of the pressing force and screw position can be improved.

[0063] Embodiment 4 The screw fastening device 100 according to the fourth embodiment is characterized by performing control to determine defects in screw fastening by referring to the records of the first distance measurement unit 51 and the second distance measurement unit 52 during and after pre-tightening. The other configurations of the screw fastening device 100 according to the fourth embodiment are the same as those of the screw fastening device 100 according to the first embodiment, and corresponding parts are given the same reference numerals and their description will be omitted.

[0064] The operation of the screw fastening device 100 according to the fourth embodiment will be described with reference to Fig. 8. Fig. 8 is a flow diagram that schematically shows the operation of the screw fastening device 100 according to the fourth embodiment. Note that the first half of the operation of the screw fastening device 100 according to the fourth embodiment is the same as steps S501 to S513 of the operation of the screw fastening device 100 according to the first embodiment (see Fig. 5).

[0065] Time series data of the pressing force and screw position during pre-tightening is measured and recorded until just before the seating surface 93 of the screw 90 comes into contact with the main surface 97 of the workpiece 99, and after pre-tightening is completed (step S513), the records are referred to determine whether the pressing force and screw position are within specified values ​​and whether the pre-tightening process was successful (step S801).

[0066] If the pressing force and screw position are not within the specified values ​​(No in step S801), that is, if there is a significant deviation between the standard time history waveform of the pressing force when the screw is successfully tightened and the waveform of the screw position, it is determined that an abnormality has occurred during pre-tightening, the subsequent process is stopped, and the product is rejected as a defective product (step S802).

[0067] Defects that may occur during pre-tightening include, for example, the rotary tool 11 coming off the screw 90, the oblique insertion of the screw 90, the entry of foreign matter, and deformation of the screw 90. In the case where the rotary tool 11 comes off the screw 90, the pressing force drops suddenly when the rotary tool 11 comes off the screw 90, so by monitoring the output of the second distance measurement unit 52 during pre-tightening, the timing of the occurrence of the abnormality and its cause can be analyzed.

[0068] If the pressing force and screw position are within the specified values ​​(Yes in step S801), the screw 90 is tightened until the specified torque is reached (step S803).

[0069] As described above, according to the screw fastening device 100 of the fourth embodiment, the control unit 2 determines whether the screw fastening operation is defective during and after pre-tightening based on the outputs of the first distance measurement unit 51 and the second distance measurement unit 52. Therefore, if it is determined that an abnormality has occurred, the subsequent process can be stopped and the product can be rejected as defective. In addition, the timing of the abnormality and its cause can be analyzed.

[0070] Embodiment 5 The screw fastening device 100 according to the fifth embodiment is characterized by performing control to determine defects in screw fastening by referring to the records of the second distance measurement unit 52 and the torque detection unit 17 during and after final fastening. The torque detection unit 17 is provided on the rotation output shaft 45 so as to measure the torque generated in the rotation output shaft 45. The other configurations of the screw fastening device 100 according to the fifth embodiment are the same as those of the screw fastening device 100 according to the first embodiment, and corresponding parts are given the same reference numerals and their description will be omitted.

[0071] The operation of the screw fastening device 100 according to the fifth embodiment will be described with reference to Fig. 9. Fig. 9 is a flow diagram that schematically shows the operation of the screw fastening device 100 according to the fifth embodiment. Note that the first half of the operation of the screw fastening device 100 according to the fifth embodiment is the same as steps S501 to S513 and steps S801 to S803 of the operation of the screw fastening device 100 according to the first and fourth embodiments (see Figs. 5 and 8).

[0072] During and after final tightening (step S803), the success or failure of the screw tightening is determined by determining whether the pressing force, screw position, and torque are within specified values ​​(step S901). Defects during final tightening include, for example, exceeding the specified torque and screw damage. If the output of torque detection unit 17 indicates that the specified torque upper limit is exceeded or that the torque is below the specified torque lower limit (No in step S901), the output from torque detection unit 17 is recorded and the product is rejected as a defective product (step S902).

[0073] If the pressing force, screw position, and torque are within the specified values ​​(Yes in step S901), the pressing force, screw position, and torque data are recorded (step S903).

[0074] As a result, in the screw tightening device 100 according to the fifth embodiment, after final tightening is completed, the position of the screw 90 can be determined from the outputs of the first distance measurement unit 51 and the second distance measurement unit 52, eliminating the need for a separate measurement of the screw height. In a typical screw tightening process, a separate inspection process for measuring the screw height may be provided after the screw tightening is completed to check whether the screw has been tightened to a predetermined position. Even in such a case, the position of the screw 90 can be recorded when final tightening is completed without the need for additional devices or equipment.

[0075] As described above, the screw tightening device 100 according to embodiment 5 is equipped with a torque detection unit 17 that detects the torque generated on the rotary output shaft 45, and judges whether the screw tightening operation is defective based on the outputs of the first distance measurement unit 51, the second distance measurement unit 52 and the torque detection unit 17 during and after final tightening. Therefore, after the screw tightening is completed, there is no need for additional devices and equipment for a screw height measurement inspection process to check whether the screw has been tightened to the specified position, and the position of the screw can be recorded when final tightening is completed.

[0076] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0077] Various aspects of the present disclosure are summarized below as appendices.

[0078] (Appendix 1) a rotary tool unit including a motor, a rotary output shaft of the motor, a rotary tool that rotates the screw, and a rotary tool attachment portion that connects the rotary output shaft and the rotary tool; a tool position displacement unit that moves the rotary tool unit along a rotation axis direction; a control unit that controls the motor and the tool position displacement unit; a first distance measuring unit that measures the distance between the screw and a fastened object to which the screw is attached; a second distance measurement unit that measures the relative position between the rotary output shaft and the rotary tool attachment unit; Equipped with The rotary output shaft and the rotary tool attachment portion slide in the direction of the rotary shaft and are connected by a flexible connecting member, The control unit controls the screw pressing force and the position of the rotary tool using the motor and the tool position displacement unit based on the measured values ​​from the first distance measurement unit and the second distance measurement unit. (Appendix 2) The screw tightening device described in Appendix 1, characterized in that the control unit controls the rotating output shaft to move the screw closer to the workpiece at a speed faster than that of the screw due to compression of the connecting member, based on outputs from the first distance measurement unit and the second distance measurement unit. (Appendix 3) The screw tightening device according to claim 1 or 2, wherein the second distance measurement unit uses a non-contact position measurement method. (Appendix 4) The screw tightening device according to any one of Supplementary Note 1 to Supplementary Note 3, characterized in that the control unit determines whether the screw tightening operation is defective based on the measurement values ​​of the first distance measurement unit and the second distance measurement unit during and after pre-tightening. (Appendix 5) a torque detection unit that detects torque generated on the rotation output shaft, A screw tightening device as described in any one of Supplementary Note 1 to Supplementary Note 4, characterized in that a fault determination is made on the screw tightening operation based on the outputs of the first distance measurement unit, the second distance measurement unit, and the torque detection unit during and after final tightening. [Explanation of symbols]

[0079] 2 Control unit, 3 Tool position displacement unit, 10 Rotary tool unit, 11 Rotary tool, 18 Rotary tool mounting unit, 31 Second motor, 38 Connecting member, 45 Rotation output shaft, 51 First distance measurement unit, 52 Second distance measurement unit, 90 Screw, 99 Fastened object, P Pressing force, 100 Screw tightening device.

Claims

1. a rotary tool unit including a motor, a rotary output shaft of the motor, a rotary tool that rotates the screw, and a rotary tool attachment portion that connects the rotary output shaft and the rotary tool; a tool position displacement unit that moves the rotary tool unit along a rotation axis direction; a control unit that controls the motor and the tool position displacement unit; a first distance measuring unit that measures the distance between the screw and a fastened object to which the screw is attached; a second distance measurement unit that measures the relative position between the rotation output shaft and the rotary tool attachment unit; Equipped with The rotary output shaft and the rotary tool attachment portion slide in the direction of the rotary shaft and are connected by a flexible connecting member, The control unit controls the screw pressing force and the position of the rotary tool using the motor and the tool position displacement unit based on the measured values ​​from the first distance measurement unit and the second distance measurement unit.

2. The screw tightening device according to claim 1, characterized in that the control unit controls the rotation output shaft to move the screw closer to the workpiece at a speed faster than that of the screw due to compression of the connecting member, based on the measured values ​​from the first distance measurement unit and the second distance measurement unit.

3. 3. The screw tightening device according to claim 1, wherein the second distance measuring unit uses a non-contact position measuring method.

4. The screw tightening device according to claim 1 or claim 2, characterized in that the control unit determines whether the screw tightening operation is defective based on the measured values ​​from the first distance measurement unit and the second distance measurement unit during and after pre-tightening.

5. a torque detection unit that detects torque generated on the rotation output shaft, The screw tightening device according to claim 1 or 2, characterized in that a fault in the screw tightening operation is determined based on the outputs of the first distance measurement unit, the second distance measurement unit, and the torque detection unit during and after final tightening.

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