JP7656820B2 - How to remove the screws - Google Patents

Description

This invention relates to a method for removing screws that, when using a screw loosening tool held by a robot arm to loosen and remove a screw that has been tightened, can be used when the screw's threads (e.g., male threads) get caught on the threads of the component being tightened (e.g., female threads), or when the screw cannot be removed by simply turning it in the loosening direction and remains in the female threaded hole of the component being tightened.

Loosening and removing screws is a task that is frequently used in assembly and disassembly work, and automation using robots is becoming more common to make work more efficient and faster.

A common method for loosening screws using a robot is to have the robot arm hold a screw-loosening tool such as an electric screwdriver or air impact driver, and calculate position information from image information captured by an image recognition camera. Alternatively, the screw's position information is taught to align it, and the screw is then rotated in the loosening direction to loosen it.

Figure 7A shows a state in which a plate-like member 102 is fastened to a fixed part 103 by a screw 101 with a constant diameter male thread portion 101c. Figure 7B shows a state in which a driver 104 is inserted into a drive portion (e.g., a Phillips-shaped groove) 101b machined into the head 101a of the screw 101, and the screw 101 is rotated in the loosening direction, causing the screw 101 to come out of the female thread 103b of the fixed part 103. Figure 7C shows a state in which the screw 101 has come out of the fixed part 103 and fallen over, unable to stand on its own, causing the screw 101 to come off.

In the case of a screw 101 with a constant diameter of the male thread portion 101c, the threads of the female thread 103b of the fixed portion 103 and the threads of the male thread portion 101c of the screw 101 remain engaged until the screw 101 comes out of the fixed portion 103, so the screw 101 comes out only by the amount of rotation in the loosening direction.

Figure 8A shows the state in which the plate-like member 102 is fastened to the fixed part 103 by a tapping screw 105, the diameter of which becomes smaller toward the tip of the male threaded part 105c. The tapping screw 105 is used to fasten a housing or an exterior cover made of a thin metal plate material.

Figure 8B shows the state in which the driver 104 is inserted into the drive part 105b of the tapping screw 105 and rotated in the loosening direction, causing the tapping screw 105 to come out of the fixed part 103. At this time, in order to prevent the tip of the driver 104 from coming off the drive part 105b of the tapping screw 105 and causing the tapping screw 105 to spin freely, it is necessary to rotate the driver 104 in the loosening direction while it is in close contact with the drive part 105b of the tapping screw 105 with the pressing force 106.

The thread meshing portion 107 indicates the portion where the threads of the male thread portion 105c of the tapping screw 105 and the threads of the female thread portion 103b of the fixing portion 3 mesh. At the beginning of loosening, there are a sufficient number of meshed threads, so even if the tapping screw 105 is pressed with a pressing force 106, the tapping screw 105 will come out by rotating in the loosening direction. However, as shown in FIG. 8C, the thread meshing portion 107 also decreases in proportion to the amount of the tapping screw 105 coming out. In addition, since the tapping screw 105 has a shape in which the diameter becomes smaller toward the tip, at a certain point, the force 108 that comes out due to the meshing of the threads becomes smaller than the pressing force 106 of the driver 104, and even if the tapping screw 105 is rotated in the loosening direction, the tapping screw 105 does not come out but is pushed back, causing it to spin freely.

Figure 8C shows the state in which the tapping screw 105 spins freely and cannot be removed, remaining in the female screw hole 103b of the fixed part 103. Even if the fastening state between the plate-shaped member 102 and the fixed part 103 is released, with the tapping screw 105 remaining in the female screw part 103b of the fixed part 103, the plate-shaped member 102 and the fixed part 103 cannot be separated.

When a human being performs a task of separating members fastened by such a tapping screw 105, the left-behind tapping screw 105 can be easily removed by pinching it with the fingertips and moving on to the next task. However, when performing the task using a robot, in order to remove the left-behind tapping screw 105, an additional task is required to change to a tool that can pinch the head 105a of the tapping screw 105 and continue the task after capturing the state of the tapping screw 105 with an image recognition camera and acquiring the position information. In addition, when pinching and pulling out the head 105a of the tapping screw 105, even if the head 105a of the tapping screw 105 is pulled out linearly in the axial direction of the tapping screw 105, the threads of the male screw portion 105c of the tapping screw 105 and the threads of the female screw portion 103b of the fixing portion 103 interfere with each other and become caught. Therefore, it is necessary to program complex robot operations such as swinging the tapping screw 105 left and right and pushing and pulling it in the axial direction while pinching it, which is an issue in reducing the work time in automation.

Patent Document 1 describes a fixed member dismantling system that uses a robot and a camera to detect screws and automatically loosen them. However, this system was developed for screws 101 with a constant diameter of the male thread portion as described in Figure 7A, and does not provide a solution to the problem of tapping screws 105 being left behind as shown in Figure 8C.

Patent No. 6051501

Although it is possible to automate the screw removal process using a robot by applying the method described in Patent Document 1, in order to remove the tapping screw 105 remaining in the female screw hole, an additional process is required, such as replacing the tool held by the robot or having an operator remove the screw in a later process, and there remain issues with reducing the work time required for automation.

The present invention aims to provide a method for removing screws that allows the user to grasp and pull out loose screws without changing tools, shortening the time required to remove screws using a robot, and reducing the number of workers required when introducing robots, while improving work efficiency.

That is, a screw removal method according to one aspect of the present invention includes the following steps:
The tip of the bit is brought into contact with the driving portion of the head of the screw screwed into the female screw hole of the engagement portion, and the bit is rotated in a direction to loosen the screw,
The head of the screw coming out of the female screw hole of the engagement portion is gripped by a collet chuck,
A screw removal method, comprising the steps of: loosening the screw held by the collet chuck while the driving portion of the head of the screw and the tip of the bit are in contact with each other; and removing the screw held by the collet chuck from the female thread hole of the engagement portion.
The bit and the collet chuck are attached to the tip of a robot arm, and the head of the screw is held by the collet chuck. When pulling out the screw, the robot arm repeatedly swings the collet chuck in the direction in which the screw is pulled out and moves it forward and backward in the axial direction relative to the direction in which the screw is pulled out, thereby pulling out the screw.
A screw removal method according to another aspect of the present invention includes the steps of:
The tip of the bit is brought into contact with the driving portion of the head of the screw screwed into the female screw hole of the engagement portion, and the bit is rotated in a direction to loosen the screw,
The head of the screw coming out of the female screw hole of the engagement portion is gripped by a collet chuck,
A screw removal method, comprising the steps of: loosening the screw held by the collet chuck while the driving portion of the head of the screw and the tip of the bit are in contact with each other; and removing the screw held by the collet chuck from the female thread hole of the engagement portion.
the bit and the collet chuck are attached to a tip of a robot arm, and the head of the screw is gripped by the collet chuck. When the screw is pulled out, a pull-out resistance force generated by the male thread of the screw and the female thread of the engagement portion getting caught is measured by a sensor;
The pulling out operation is performed to a predetermined position by repeating the swinging motion of the tip of the robot arm in the pulling out direction of the screw and the forward and backward movements within the range of resistance force below a specified value .

By using the screw removal method according to the above aspect of the present invention, it is possible to remove screws that are left partially loose in the female threads because the threads of the screws are caught and cannot be separated, even though there is no fastening force to fasten the components together, without replacing the robot hand. As a result, it is possible to shorten the time required for screw removal work, and to reduce the number of people required and improve work efficiency when introducing robots.

FIG. 1 is a diagram of a screw removal mechanism according to an embodiment of the present invention. FIG. 1 is a diagram showing a collet chuck in an open state according to an embodiment of the present invention; FIG. 1 is a diagram showing a collet chuck in a closed state according to an embodiment of the present invention. FIG. 1 is a diagram of a screw removal device according to an embodiment of the present invention. FIG. 1 shows a state after bit alignment according to an embodiment of the present invention. FIG. 1 is a diagram showing a state in which a bit and a driving part of a tapping screw are in contact with each other in an embodiment of the present invention. FIG. 1 is a diagram showing a state in which a tapping screw is being loosened according to an embodiment of the present invention. FIG. 1 is a diagram showing a state in which a collet chuck is being advanced in an embodiment of the present invention. FIG. 1 is a diagram showing a state in which the collet chuck grips the head of a tapping screw in an embodiment of the present invention. FIG. 1 is a diagram showing a state in which a tapping screw is being pulled out in the embodiment of the present invention. FIG. 1 is a diagram showing a state in which the collet chuck releases the grip on the head of the tapping screw in the embodiment of the present invention. Flowchart of a screw removal method according to an embodiment of the present invention Diagram of components fastened using screws with a constant diameter male thread Diagram of a screw with a constant diameter male thread being loosened Diagram of a screw with a constant diameter male thread that has been pulled out Diagram of parts fastened with tapping screws Diagram of tapping screws being loosened Diagram of the tapping screw left behind in the fixing part

The following describes an embodiment of the present invention with reference to the drawings.

Figure 1 is a diagram of a screw removal mechanism 40 capable of implementing the screw removal method according to an embodiment of the present invention.

The screw removal mechanism 40 is attached to a force sensor 21 attached to the tip of the robot arm 9 via a robot arm shock absorber mechanism 10. As an example, the robot arm shock absorber mechanism 10 includes a guide shaft 10a that guides the axial movement of the screw removal mechanism 40, and a spring 10b that is disposed around the guide shaft 10a and has an upper end fixed to the force sensor 21 and a lower end fixed to the screw removal mechanism connecting member 11 described below.

The screw removal mechanism 40 includes at least a screw rotation drive device, such as an air impact driver 12, that rotates the screw 5, a bit 13, a collet chuck 41, and an air cylinder 19 for the collet chuck.

More specifically, the upper end of the screw removal mechanism 40 is equipped with a screw removal mechanism connecting member 11, which is a plate-like member with an upside-down L-shaped side, and the upper surface of the horizontal plate of this screw removal mechanism connecting member 11 is connected to the spring 10b of the robot arm shock absorber mechanism 10.

The upper end of an air impact driver 12 is attached to the underside of the horizontal plate of the screw removal mechanism connecting member 11 as a tool for loosening the screws 5. In the embodiment of the present invention, an air impact driver 12 powered by compressed air is used as an example of a screw rotation drive device, but if it is necessary to finely adjust the rotation speed of the bit 13 when loosening, an electric driver powered by a servo motor may be used instead of the air impact driver 12.

The base end of a bit 13, for example, with a Phillips convex shape (i.e., a Phillips screwdriver shape) that matches the shape of the drive part 5b of the head 5a of the screw 5, is inserted into the lower end of the air impact driver 12. The bit 13 is subject to breakage during use or wear due to contact between the screw head 5a and the drive part 5b over long periods of use, so it is desirable for the tip of the air impact driver 12 to be attached in a way that allows easy replacement.

At the tip of the bit 13, a collet chuck 41 for gripping the head 5a of the screw 5 is arranged, which consists of a collet 16 in the form of a conical tube member made up of multiple claw members, and a flange body 15 in the form of a cylindrical member partially overlapping the outside of the collet 16, so that they can move axially coaxially around the periphery of the bit 13. The procedure by which the collet chuck 41 grips the head 5a of the screw 5 will be described later.

Figure 2A shows the collet chuck 41, which is composed of the flange body 15 and collet 16, in an open state.

The flange body 15 has a central opening 15c on the upper surface of the bottom of the cylindrical member (e.g., the upper end surface in Fig. 2A) through which the bit 13 passes freely in the axial direction, and on the inside of the tip opening edge (e.g., the lower end opening edge in Fig. 2A), there is a ring-shaped protrusion 15b on which a conical inclined surface 15a is formed that narrows from the outer edge along the axial direction toward the inside.

The collet 16 is configured such that the bit 13 penetrates the center of the conical tube member in the axial direction so as to be relatively movable. The conical tube member is divided into a plurality of claw members 16a in the circumferential direction (e.g., three in FIG. 2A) with a plurality of notches 16e in the radial direction with respect to the circumferential direction. At the inner tip (e.g., the lower end in FIG. 2A) of each claw member 16a, there is a claw portion 16b that protrudes radially inward in a partially annular shape. The claw portions 16b have inner circumferential surfaces that are curved along the axial direction, and are arranged to face each other toward the center, so that they can grip the side of the head 5a of the screw 5, as described later. The outer circumferential surface of each claw member 16a has a conical inclined surface 16c on which the conical inclined surface 15a of the flange body 15 can slide and which approaches the center as it moves from the lower end to the upper end along the axial direction. The base end of each claw member 16a (for example, the upper end in FIG. 2A) is separated from the bit 13 so as not to come into contact with the bit 13, and each claw member 16a is freely movable in the axial direction relative to the bit 13.

A coil spring for the flange body 14 is disposed between the inner peripheral surface of the central opening 15c of the flange body 15 and the upper end of the claw member 16a of the collet 16, and around the bit 13. When the flange body 15 descends relative to the bit 13, a downward force is elastically applied to the collet 16 via the flange body spring 14.

A coil spring for collet 17 is disposed around the bit 13, between a ring-shaped stopper 18 near the tip of the bit 13 and the upper end of the claw member 16a of the collet 16. When the collet 16 descends relative to the bit 13, the collet spring 17 contracts, but when the downward force is no longer acting, the spring force of the collet spring 17 allows it to return to its original position.

In order to slide the collet 16 and flange body 15 in the forward and backward directions relative to the screw 5 on the same axis as the bit 13, an air cylinder 19 for the collet chuck is installed on the outer surface of the vertical plate of the screw removal mechanism connecting member 11. That is, the tip of the piston rod 19a of the air cylinder 19 for the collet chuck is connected to the bottom of the upper end of the flange body 15 via a plate-shaped collet chuck connecting member 20, and in FIG. 1, when the piston rod 19a descends, the flange body 15 descends relative to the collet 16 and comes into contact with the collet 16, and the flange body 15 and collet 16 descend.

By moving the flange body 15 axially toward the tip end, i.e., lowering it in FIG. 1, the notch 16e of the collet 16 closes toward the center, making it possible to firmly grip an object (such as a screw) inside the notch 16e. FIG. 2B shows the collet chuck 41 in a closed state.

Figure 3 is a diagram of a screw removal device 50 according to an embodiment of the present invention. The screw removal device 50 includes the screw removal mechanism 40 described in Figure 1 and a robot arm 9. The screw removal mechanism 40 is attached to the tip of the robot arm 9. A robot with vertical articulations is used as the robot arm 9 to remove the screws 5 arranged on the front, side, and top surface of the workpiece 23.

In addition, since the workpiece 23 is fixed onto the workpiece mounting table 24 that has a rotation mechanism, it is possible to remove the screws 5 on the right side, left side, and back by changing the orientation of the workpiece 23 so that the side with the screws 5 faces the robot arm 9.

When loosening a screw, it is necessary to align the center of the drive part 5b of the screw 5 with the center of the bit 13 of the screw removal mechanism 40. To do this, the workpiece 23 is rotated 90 degrees at a time, and the front, left and right sides, back, and top plane are each imaged by the screw position recognition camera 22. The screw position recognition camera 22 is located at the tip of the robot arm 9. The control unit 60 calculates the coordinates of the screws 5 from the image information captured by the screw position recognition camera 22, making it possible to determine the position of each screw 5. For example, if the workpiece 23 has a housing structure made of thin sheet metal members, the rigidity of the housing decreases as the screws 5 are removed, and the shape of the housing changes due to impact or vibration during removal, and the position of the screws 5 may change from the position when imaged by the screw position recognition camera 22. For this reason, it is desirable to perform screw position confirmation imaging as appropriate in accordance with the change in the shape of the housing (for example, before (just before) removing the screws on each side, or after the end of the rotation operation when rotating the workpiece 23 by 90 degrees).

The control unit 60 is provided to control the screw removal operation, and controls the operation of the robot arm 9, the air cylinder 19 for the collet chuck, and the air impact driver 12 based on input information from the force sensor 21, the screw position recognition camera 22, the robot arm 9, the air impact driver 12, etc.

Next, we will explain the screw removal procedure with reference to the diagram.

Figure 4A is a diagram after alignment of the bit 13 and the drive part 5b of the tapping screw 5 in the embodiment of the present invention. Figure 4A is a diagram showing a state in which a plate-shaped member 2 is fastened to a fixing part 3, which is an example of an engagement part of an object to be assembled or disassembled, by a tapping screw 5 in which the diameter of the male thread part 5c becomes smaller toward the tip. The tapping screw 5 is used, for example, to fasten a housing or an exterior cover made of a thin metal plate material. Under the control of the control unit 60, the robot arm 9 is driven and controlled based on the image information from the screw position recognition camera 22 to align the center of the bit 13 with the center position of the drive part 5b of the tapping screw 5, and after the bit 13 waits above the tapping screw 5, the robot arm 9 is advanced (i.e., descended in Figure 4A) to bring the tip of the bit 13 into contact with the drive part 5b of the tapping screw 5.

Figure 4B is a diagram showing the state in which the tip of the bit 13 and the drive part 5b of the tapping screw 5 are in contact in the embodiment of the present invention. Figure 4C is a diagram showing the state in which the tapping screw 5 is being loosened in the embodiment of the present invention. When the tip of the bit 13 and the drive part 5b of the tapping screw 5 are in contact with each other, and air is supplied to the air impact driver 12 under the control of the control part 60 to rotate the bit 13 in the direction in which the tapping screw 5 is loosened, the tapping screw 5 comes out upward from the fixed part 3, which is an example of an engagement part, as shown in Figure 4C. As the tapping screw 5 comes out, the entire screw removal mechanism 40 is pushed up, but the spring 10b of the robot arm buffer mechanism 10 contracts by the same amount as the push-up stroke, allowing the robot arm 9 to maintain the position it was in before the screw 5 was loosened.

In the embodiment of the present invention, the spring 10b is used in the robot arm shock absorbing mechanism 10, but instead of the spring 10b, an elastic body that generates a repulsive force while absorbing the upward stroke, such as a rubber material, may be used.

Next, the process of removing the tapping screw 5 that has come out of the fixed part 3 from the female threaded hole 3a of the fixed part 3 will be explained with reference to the drawings.

The tapping screw 5 will come out of the fixed part 3 when rotated in the loosening direction, but as mentioned above, if the force that causes the tapping screw 5 to come out when it is loosened becomes smaller than the force that brings the bit 13 into close contact with the drive part 5b of the tapping screw 5 due to a reduction in the number of meshing threads between the male thread 5c of the tapping screw 5 and the female thread 3c of the fixed part 3, the screw 5 will not come out even when the tapping screw 5 is rotated in the loosening direction.

To detect this state, a force sensor 21 installed between the robot arm 9 and the screw removal mechanism 40 is used. The spring 10b of the robot arm shock absorber mechanism 10 is compressed in proportion to the amount of the tapping screw 5 that is removed, so the force sensor 21 detects the reaction force of the spring 10b, and the reaction force does not increase even though the bit 13 is rotating for a certain period of time. Alternatively, if the control unit 60 detects that the reaction force is decreasing as the tapping screw 5 is pushed back, the control unit 60 can determine that the tapping screw 5 is spinning freely without being removed.

When the control unit 60 detects this free-spinning state of the tapping screw 5, the air cylinder 19 for the collet chuck is driven under the control of the control unit 60 to move the collet chuck 41 forward (i.e., downward in Figure 4C).

Figure 5A is a diagram showing a state in which the collet chuck 41 in an embodiment of the present invention is advanced (i.e., lowered in Figure 5A). The collet chuck connecting member 20 is connected to the cylinder rod 19a of the collet chuck air cylinder 19 and the flange body 15. In conjunction with the downward stroke of the cylinder rod 19a of the collet chuck air cylinder 19, the flange body 15 descends toward the tapping screw 5. The flange body 15 and collet 16 are separate parts, but when the flange body spring 14 built into the flange body 15 is pressed by the flange body 15, the collet 16 also descends together with the flange body 15.

When the collet 16 descends, the collet spring 17 built into the collet 16 is compressed in conjunction with the downward stroke of the collet 16. The collet spring 17 has a stopper 18 attached near the tip of the bit 13, so that the collet spring 17 does not fall off the bit 13 when the collet 16 descends, and holds the position of the downward end, stopping the collet 16 at a specified downward position.

The lowering position of the collet 16 is adjusted by changing the thickness of the stopper 18 or the length of the collet spring 17 so that, when the collet 16 is closed, it can be stopped below the tip of the bit 13 and at a position where it can grip the head 5a of the tapping screw 5.

When the collet 16 has been lowered to a position where it grips the head 5a of the tapping screw 5, the flange body 15 is further lowered, causing the notch 16e of the collet 16 to close and the collet 16 to grip the head 5a of the tapping screw 5.

Figure 5B is a diagram of the collet chuck 41 gripping the head 5a of the tapping screw 5 in an embodiment of the present invention. The collet 16 grips the head 5a of the tapping screw 5 with the drive portion 5b of the tapping screw 5 and the tip of the bit 13 in a state of tight contact. Therefore, even if there is a discrepancy in the timing at which each of the multiple notches 16e of the collet 16 closes and grips the head 5a of the tapping screw 5 with the claw member 16a, the tapping screw 5 can be securely gripped without causing a phenomenon such as it flying off.

Next, with the head 5a of the tapping screw 5 still held by the collet 16, the tip of the robot arm 9 is moved backward in the direction of removal (i.e., upward in Fig. 5B). At this time, the male thread 5c of the tapping screw 5 may get caught on the female thread 3c of the fixed part 3, or the male thread 5c of the tapping screw 5 may get caught on the plate-like member 2, causing resistance to be generated when the tapping screw 5 is pulled straight upward. If such a catch is present, forcing the tip of the robot arm 9 backward (i.e., moving upward in Fig. 5B) may result in an overload causing the entire screw removal device to report an error and stop, or the plate-like member 2 and the tapping screw 5 may be lifted together in a caught state, or the screw removal mechanism 40 may be damaged. For this reason, the force sensor 21 detects the pull-out resistance when the tip of the robot arm 9 is moved backward (i.e., moved upward in FIG. 5B ), and if the control unit 60 detects that the pull-out resistance is equal to or greater than a specified value, the control unit 60 temporarily stops the backward movement of the tip of the robot arm 9 (i.e., moved upward in FIG. 5B ) under the control of the control unit 60, and moves the tip of the robot arm 9 backward (i.e., moved upward in FIG. 5B ) while swinging it in small increments from side to side relative to the direction of pulling out the screw 5. Alternatively, the tip of the robot arm 9 is pulled back little by little (i.e., moved upward in FIG. 5B ) while repeatedly pulling out and advancing (i.e., moving downward in FIG. 5B ). In this case, the force sensor 21 continues to measure the pull-out resistance, and if the control unit 60 detects that the pull-out resistance has a tendency to increase relative to the amount of pulling out, the left-right swing and/or forward and backward movement (i.e., moving downward or upward in FIG. 5B ) are further repeated, and the tapping screw 5 is pulled out while releasing the hook between the tapping screw 5 and the fixing part 3 or the plate-like member 2. FIG. 5C shows the tapping screw 5 being pulled out in an embodiment of the present invention.

Next, when the tapping screw 5 has been completely removed and the tip of the robot arm 9 has been returned to the standby position shown in FIG. 5D (an example of a predetermined position during removal), the collet chuck air cylinder 19 is operated to pull the flange body 15 back to its original position, opening the notch 16e of the collet 16, releasing the grip on the tapping screw 5, causing the tapping screw 5 to fall out, and completing the removal of the tapping screw 5. Furthermore, the collet chuck air cylinder 19 is operated to pull the flange body 15 back, releasing the compression of the collet spring 17, and pushing the collet 16 back to its original position.

Figure 5D is a diagram showing the state in which the collet chuck 41 in the embodiment of the present invention releases the grip of the tapping screw head 5a. It is assumed that in most cases, the tapping screw 5 falls downward as soon as the head 5a of the tapping screw 5 is released from the collet 16. However, if the tip of the bit 13 is worn unevenly or foreign matter adheres to the plus groove hole of the drive part 5b of the tapping screw 5, causing the tip of the bit 13 and the drive part 5b of the tapping screw 5 to be caught in each other, the tapping screw 5 will not fall off even if the collet 16 is released from its grip. In this way, if the tapping screw 5 remains attached to the tip of the bit 13, it is not possible to remove the tapping screw 5 at another position. Therefore, the vicinity of the tip of the bit 13 is imaged by the screw position recognition camera 22, and the presence or absence of a screw at the tip of the bit 13 is confirmed by the control unit 60 using a known method such as pattern matching based on the image information from the screw position recognition camera 22. An example of pattern matching here is to determine the imaging position or angle, take an image in advance at that position with and without the screw, and compare the image data to determine whether or not there is a screw remaining. If the control unit 60 determines that there is a screw, the air impact driver 12 is operated under the control of the control unit 60 to rotate the bit 13 and shake off the tapping screw 5. An additional screw recovery operation is performed by placing a magnet for screw recovery (not shown) near the work setting table 24 and bringing the tapping screw 5 close to it and recovering it by magnetic attraction.

Next, the steps of the screw removal method in an embodiment of the present invention will be explained using a flowchart.

Figure 6 is a flowchart of a screw removal method according to an embodiment of the present invention. The screw removal method can be performed under the control of the control unit 60.

First, in step S1, the tip of the robot arm 9 is moved to move the screw position recognition camera 22 attached to the tip of the robot arm 9 to the opposing surface of the workpiece 23, where it takes an image and obtains the position information of the screw 5.

Next, in step S2, the tip of the robot arm 9 is moved to align the center of the tip of the bit 13 inserted into the air impact driver 12 with the center of the drive part 5b of the tapping screw 5.

Next, in step S3, the robot arm 9 is advanced (i.e., lowered in FIG. 4A) to insert the tip of the bit 13 into the drive part 5b of the tapping screw 5, and then the air impact driver 12 is operated to rotate the bit 13 for a predetermined time to loosen the tapping screw 5.

Next, in step S4, the vicinity of the tip of the bit 13 is imaged by the screw position recognition camera 22, and the control unit 60 checks the presence or absence of a screw at the tip of the bit 13 using a known method such as pattern matching based on the image information from the screw position recognition camera 22. If a screw is found to be remaining when checking, an additional process such as changing the hand was required in the past. However, in the embodiment of the present invention, a screw removal mechanism 40 that has both the function of loosening the screw 5 and the function of pinching and pulling out the screw 5 is attached to the robot arm 9, so that the hand is not replaced and the cylinder rod 19a of the collet chuck air cylinder 19 is lowered to grip the head 5a of the tapping screw 5 in step S5, and the collet 16 is advanced, i.e., lowered, together with the flange body 15, via the flange body spring 14. As a result, the head 5a of the tapping screw 5 is gripped by the collet 16.

Next, in step S6, while the head 5a of the tapping screw 5 is still held by the collet 16, the operation of pulling out the screw 5 in step S7 is performed. The pull-out resistance force at this time is measured in real time by the force sensor 21. If the control unit 60 detects that the resistance force during pulling out is equal to or less than the specified value X Newtons, the control unit 60 determines that the male thread 5c of the tapping screw 5 is not caught, and moves the robot arm 9 upward to the pull-out completion point in step S9. If the control unit 60 detects that the resistance force during removal exceeds a specified value X Newtons, the control unit 60 determines that the male thread 5c of the tapping screw 5 is caught on the female thread 3c of the fixed part 3 of the workpiece 23 or the plate-like member 2, and under the control of the control unit 60, in step S8, the screw head 5a is held by the collet 16, and the screw removal mechanism 40 is swung left and right or moved forward and backward by the robot arm 9, or the bit 13 is rotated in the direction to loosen the screw 5, to perform the removal operation. In parallel with the amount of removal, the force sensor 21 continuously measures the removal resistance force, and if the control unit 60 determines that the removal resistance force has a tendency to increase, the removal operation is stopped once under the control of the control unit 60, and the left and right swinging and forward and backward movements are repeated in small increments to release the threads 3c and 5c from being caught, and the removal operation is completed in step S9.

Then, in step S10, the control unit 60 checks for remaining screws in the same manner as in step S4, and if there are no remaining screws, the control unit 60 determines that removal of the screws 5 is complete, and continues removing screws in other positions under the control of the control unit 60. If remaining screws are confirmed in step S10, an error is issued in step S11 under the control of the control unit 60 as an abnormality, the screw removal device 50 is stopped, and measures such as the operator manually removing the screws 5 are taken.

According to the present invention, when removing screws using a robot, the threads 3c, 5c of the screw 5 get caught on each other and cannot be separated even though there is no fastening force to fasten the parts together. Alternatively, it is possible to remove the screw 5 that is left partially loose in the female screw hole 3a without changing the hand of the robot arm 9, shortening the screw removal work time and realizing manpower saving and improved work efficiency when introducing robots.

In addition, by appropriately combining any of the various embodiments or modifications described above, it is possible to achieve the effects of each. In addition, it is possible to combine embodiments with each other, or to combine examples with each other, and it is also possible to combine features of different embodiments or examples.

The screw removal method according to the above aspect of the present invention is suitable for use in the process of automatically dismantling housing covers, which are an example of items to be dismantled, during the dismantling of collected discarded home appliances at home appliance recycling plants, etc., for example.

1 Screw 2 Plate-like member 3 Fixing portion 3c Female thread 4 Driver 5 Tapping screw 5a Head 5b Drive portion 5c Male thread 6 Pressing force 7 Thread meshing portion 8 Pulling out force 9 Robot arm 10 Robot arm buffer mechanism 10a Guide shaft 10b Spring 11 Screw removal mechanism connecting member 12 Air impact driver 13 Bit 14 Flange body spring 15 Flange body 15a Conical inclined surface 15b Center opening 16 Collet 16a Claw member 16b Claw portion 16e Notch portion 17 Collet spring 18 Stopper 19 Collet chuck air cylinder 19a Piston rod 20 Collet chuck connecting member 21 Force sensor 22 Screw position recognition camera 23 Work 24 Work installation table 40 Screw removal mechanism 41 Collet chuck 50 Screw removal device

Claims (3)

The tip of the bit is brought into contact with the driving portion of the head of the screw screwed into the female screw hole of the engagement portion, and the bit is rotated in a direction to loosen the screw,
The head of the screw coming out of the female screw hole of the engagement portion is gripped by a collet chuck,
A screw removal method, comprising the steps of: loosening the screw held by the collet chuck while the driving portion of the head of the screw and the tip of the bit are in contact with each other; and removing the screw held by the collet chuck from the female thread hole of the engagement portion .
This screw removal method comprises the steps of: attaching the bit and the collet chuck to the tip of a robot arm; gripping the head of the screw with the collet chuck; and repeating a swinging motion of the collet chuck by the robot arm in the direction in which the screw is pulled out, and a forward and backward motion in the axial direction relative to the direction in which the screw is pulled out, to pull out the screw . The tip of the bit is brought into contact with the driving portion of the head of the screw screwed into the female screw hole of the engagement portion, and the bit is rotated in a direction to loosen the screw,
The head of the screw coming out of the female screw hole of the engagement portion is gripped by a collet chuck,
A screw removal method, comprising the steps of: loosening the screw held by the collet chuck while the driving portion of the head of the screw and the tip of the bit are in contact with each other; and removing the screw held by the collet chuck from the female thread hole of the engagement portion.
the bit and the collet chuck are attached to a tip of a robot arm, and the head of the screw is gripped by the collet chuck. When the screw is pulled out, a pull-out resistance force generated by the male thread of the screw and the female thread of the engagement portion getting caught is measured by a sensor;
A screw removal method comprising repeating swinging motion and forward and backward motion of the tip of the robot arm in the direction of pulling out the screw within a range of resistance force below a specified value, thereby pulling out the screw to a predetermined position. a sensor is used to measure a pull-out resistance force generated when the male thread of the screw and the female thread of the engagement portion are caught when the screw is pulled out while the head of the screw is held by the collet chuck;
2. The screw removing method according to claim 1 , further comprising repeating swinging and forward and backward movements of the tip of the robot arm in the screw pulling direction within a range of resistance force equal to or less than a specified value to pull out the screw to a predetermined position.

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