Assist arm device and control method thereof

Abstract

To reduce a burden of an operator who performs work using an assistance arm without increasing costs.SOLUTION: An assistance arm device 1 includes: an arm part 3 having joints (rotation shafts 7 to 9); a nut runner 4 mounted on a distal end of the arm part 3; angle sensors 21 to 23 that detect a position of the nut runner 4; and brakes 31 to 33 provided in the joints of the arm part 3. When the nut runner 4 is moved to a work position (nut N), upon detecting proximity of the nut runner 4 to the work position by the angle sensors 21 to 23, the brakes 31 to 33 are actuated to brake rotation of the joints of the arm part 3.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an assisting arm device and a control method thereof. [Background technology]

[0002] In the process of tightening nuts or bolts on an automobile assembly line, an assistant arm is sometimes used to reduce the burden on the worker. In this case, the worker moves a nut runner attached to the assistant arm to the tightening position and then tightens the nut or bolt.

[0003] For example, Patent Document 1 listed below discloses an assisting arm device (work management system) in which a tool position detection means for detecting the position of a tool and a resistance adjustment means for adjusting the brake of the assisting arm joint are provided at the joint of the assisting arm. In this assisting arm device, the brake of the joint is released when the tool is approaching the next work position, and the brake of the joint is activated when the tool is away from the next work position. This is said to enable the tool operated by the worker to be naturally guided to the next work position. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-799 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the output of the tool (for example, the tightening torque) is large or when the tool has a wide movable range and a long assisting arm, it is necessary to increase the size of the assisting arm to increase its strength. Such a large assisting arm is heavy, so the inertial force increases when the worker starts or stops moving the tool, which places a burden on the worker.

[0006] For example, if the assisting arm is driven by power such as a motor, the burden on the worker can be reduced. However, in this case, to ensure safety, it is necessary to separate the worker from the power-driven assisting arm, which requires a huge capital investment such as extending the process.

[0007] Therefore, an object of the present invention is to reduce the burden on workers who perform work using an assistance arm without increasing costs. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides an assisting arm device including an arm having a joint, a tool attached to the tip of the arm, position detection means for detecting the position of the tool, and a brake provided at the joint of the arm, When the tool is moved to a working position, if the position detection means detects that the tool has approached the working position, the assist arm device activates the brake to stop the rotation of the joint of the arm portion.

[0009] In the above-mentioned assisting arm device, when a worker moves a tool attached to the tip of the arm to a working position, the brake is activated to stop the rotation of the joint when the tool approaches the working position. This cancels out the inertial force of the moving body including the arm and the tool, reducing the force required to decelerate the tool and easing the burden on the worker.

[0010] As the position detection means, for example, a proximity switch can be provided on the arm. In this case, the proximity switch needs to be provided in a position on the arm where it can detect the proximity of the tool to the work position. Therefore, when the vehicle model or work position changes, it may be necessary to change the attachment position of the proximity switch on the arm. In contrast, if the position detection means detects the position of the tool based on the rotation angle of the joint of the arm, changes in the vehicle model or work position can be accommodated simply by changing the control program, making it possible to flexibly respond to an increase in vehicle models and changes in work positions.

[0011] In the above-described assistance arm device, when the brake is activated as the tool approaches the work position, if the tool comes to a complete stop before reaching the work position, the tool must be moved again to place it at the work position, which increases the burden on the worker. Therefore, when moving the tool to the work position, it is preferable to activate the brake and then release it before the tool comes to a complete stop. This allows the tool to be placed at the work position while continuing to move, thereby reducing the burden on the worker.

[0012] The present invention can also be characterized as a control method for a conventional assisting arm device having a position detection means and a brake. That is, the present invention is a control method for an assisting arm device that includes an arm portion having a joint, a tool attached to the tip of the arm portion, a position detection means for detecting the position of the tool, and a brake provided at the joint of the arm, This method can also be characterized as a control method for an assisting arm device, in which, when the tool is moved to a working position, if the position detection means detects that the tool has approached the working position, the brake is activated to stop the rotation of the joint of the arm portion. [Effects of the Invention]

[0013] As described above, according to the present invention, the burden on a worker who performs work using an assisting arm can be reduced without increasing costs. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a side view of an assisting arm device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view of the assisting arm device. [Figure 3] FIG. 10 is a plan view showing the state in which the tool is moved toward the nut. [Figure 4] FIG. 10 is a plan view showing a state in which the tool is close to the nut. [Figure 5]FIG. 10 is a plan view showing a state in which the tool is closer to the nut. [Figure 6] FIG. 10 is a plan view showing the tool positioned to tighten the nut. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] As shown in FIGS. 1 and 2, an assisting arm device 1 according to one embodiment of the present invention comprises a base 2, an arm portion 3, and a nut runner 4 as a tool attached to the tip of the arm portion 3.

[0017] The arm unit 3 has a first arm 5 and a second arm 6. The base end of the first arm 5 is attached to the base 2 via a rotation shaft 7. The rotation shaft 7 allows the first arm 5 to rotate in a horizontal plane relative to the base 2. In other words, the connection via the rotation shaft 7 serves as a joint that rotates the first arm 5 in a horizontal plane.

[0018] The tip of the first arm 5 and the base end of the second arm 6 are connected via rotation shafts 8 and 9. In the illustrated example, a bracket 10 is attached to the tip of the first arm 5 via the rotation shaft 8, and the base end of the second arm 6 is attached to this bracket 10 via the rotation shaft 9. The rotation shaft 8 allows the second arm 6 to rotate in a horizontal plane relative to the first arm 5. In other words, the connection via the rotation shaft 8 serves as a joint that rotates the second arm 6 in a horizontal plane relative to the first arm 5. Furthermore, the rotation shaft 9 allows the second arm 6 to rotate in a vertical plane relative to the first arm 5. In other words, the connection via the rotation shaft 9 serves as a joint that rotates the second arm 6 in a vertical plane relative to the first arm 5. By rotating the second arm 6 about the rotation shaft 9 in a vertical plane, the nut runner 4 attached to the tip of the second arm 6 can be raised and lowered.

[0019] In this embodiment, the second arm 6 is made up of two links 6a and 6b. The base end of each of the links 6a and 6b is attached to a bracket 10 via a rotation shaft 9. The tip of each of the links 6a and 6b is attached to a bracket 12 fixed to the nut runner 4 via a rotation shaft 11. In other words, the two links 6a and 6b, the brackets 10 and 12, and the rotation shafts 9 and 11 form a parallel link mechanism. As a result, when the second arm 6 is rotated around the rotation shaft 9, the nut runner 4 can be raised and lowered with its axis parallel to the vertical direction.

[0020] In this embodiment, the second arm 6 is provided with a cylinder 13 as a biasing means. A body 13a of the cylinder 13 is attached to the bracket 10 via a rotary shaft 14, and a pin 13b of the cylinder 13 is attached to the second arm 6 (the lower link 6b in the illustrated example) via a rotary shaft 15. The cylinder 13 is biased by, for example, air pressure in a direction in which the pin 13b extends from the body 13a. The biasing force of this cylinder 13 supports the weight of the nut runner 4 and the second arm 6, thereby reducing the burden on the worker.

[0021] The assisting arm device 1 is provided with a position detection means for detecting the position of the nut runner 4. In this embodiment, the position detection means is an angle sensor for detecting the rotation angle of each joint of the arm unit 3. Specifically, an angle sensor 21 for detecting the rotation angle of a rotating shaft 7 provided at the connection between the first arm 5 and the base 2, and angle sensors 22 and 23 for detecting the rotation angles of rotating shafts 8 and 9 provided at the connection between the first arm 5 and the second arm 6 are provided. In the illustrated example, the angle sensor 23 is provided at a position where it can detect the rotation of the rotating shaft 9 provided at the base end of one link 6a of the second arm 6.

[0022] Each joint of the arm unit 3 is provided with a brake for braking the rotation of the joint. In this embodiment, brakes are provided at all joints except for the joint at the tip of the arm unit 3 (rotational axis 11). Specifically, brake 31 is provided for braking the rotation of rotational axis 7 provided at the connection between the first arm 5 and the base 2, and brakes 32 and 33 are provided for braking the rotation of rotational axes 8 and 9 provided at the connection between the first arm 5 and the second arm 6. In the illustrated example, brake 33 is provided at rotational axis 9 provided at the base end of one link 6a of the second arm 6.

[0023] The assist arm device 1 has a control unit (not shown). The control unit is connected to the angle sensors 21-23, the brakes 31-33, and the switch of the nut runner 4. The control unit calculates the position of the nut runner 4 based on the angles of the rotation shafts 7-9 detected by the angle sensors 21-23. The control unit controls braking and release of the rotation of each joint by the brakes 31-33. ON signals and OFF signals of the switch of the nut runner 4 are transmitted to the control unit.

[0024] The procedure for working using the assisting arm device 1 will be explained below with reference to Figures 3 to 6. Note that in Figures 3 to 6, the arm unit 3 and the like are not shown.

[0025] The worker moves the nut runner 4 attached to the assisting arm device 1 to the work position where the next task will be performed, which in this embodiment is the nut N (or bolt; the same applies below) to be tightened next. Specifically, the worker first moves the nut runner 4 toward the nut N (see FIG. 3). While the nut runner 4 is being moved, the rotation angles of the rotation shafts 7 to 9 detected by the angle sensors 21 to 23 provided at the joints of the arm section 3 are transmitted to the control unit, and the control unit constantly calculates the position (coordinates) of the nut runner 4 from these rotation angles.

[0026] The control unit stores in advance the coordinates of the next nut to be tightened, and determines whether the coordinates of the nut runner 4, calculated based on the rotation angles of the rotating shafts 7-9, are close to the coordinates of the nut N. For example, as shown in FIG. 4, when the center of the nut runner 4 enters a predetermined area P that includes the nut N, specifically when the distance between the coordinates of the nut runner 4 and the coordinates of the nut N becomes equal to or smaller than a predetermined value, it is determined that the nut runner 4 is close to the nut N. When the control unit determines that the nut runner 4 is close to the nut N, it issues a command to operate the brakes 31-33, braking the rotation of the rotating shafts 7-9. This cancels out the inertial force of the moving body including the arm unit 3 and the nut runner 4, and the moving speed of the nut runner 4 is reduced.

[0027] When the tightening torque of the nut runner 4 is large or the arm section 3 is long, the arm section 3 must be large to provide the strength to withstand the torque, which increases the weight of the arm section 3. In this case, the inertial force of the arm section 3 increases, so the force required to move or stop the nut runner 4 increases, increasing the burden on the worker. Therefore, as described above, when the nut runner 4 approaches the next nut to be tightened, the inertial force (particularly the inertial force of the arm section 3) is counteracted to reduce the moving speed of the nut runner 4, thereby reducing the burden on the worker when stopping the nut runner 4.

[0028] Then, the control unit releases the brakes 31 to 33 before the nut runner 4 comes to a complete stop (see FIG. 5). For example, the brakes 31 to 33 are released when a predetermined time has elapsed since the brakes 31 to 33 were activated. The length of time for which the brakes 31 to 33 are activated is set to a length that can sufficiently cancel the inertial force of the arm unit 3 and that does not cause the nut runner 4 to come to a complete stop. By activating the brake 33 for a predetermined time in this manner, the moving speed of the nut runner 4 is reduced from the speed V (see FIG. 4) at the start of braking to v (see FIG. 5). Alternatively, the moving speed of the nut runner 4 may be calculated based on the rotation angles of the rotating shafts 7 to 9 while the brakes 31 to 33 are activated, and the brakes 31 to 33 may be released when the moving speed of the nut runner 4 falls below a predetermined value.

[0029] The worker continues to move the nut runner 4, whose speed has been reduced in this way, without stopping it, and fits the socket of the nut runner 4 onto the next nut to be tightened (see Figure 6). The worker then presses the switch on the nut runner 4 to tighten the nut. At this time, when an ON signal from the switch on the nut runner 4 is transmitted to the control unit, the control unit activates the brakes 31 to 33, restricting the rotation of the joints (rotation axes 7 to 9) of the arm unit 3. This restricts the movement of the joints of the arm unit 3 due to the reaction force generated when the nut is tightened. Then, once tightening of the nut is complete, the switch on the nut runner 4 is turned OFF, and at the same time the brakes 31 to 33 are released, allowing the joints of the arm unit 3 to rotate.

[0030] In this embodiment, the brakes 31 to 33 for fixing the arm section 3 when tightening a nut and the position detection means for detecting the position of the nut runner 4, which are also provided in conventional assisting arm devices, are used to cancel out the inertial force of the arm section 3 when moving the nut runner 4. As a result, simply by incorporating a control program for the brakes 31 to 33 based on the position of the nut runner 4 as described above into the control section of the conventional assisting arm device, it is possible to cancel out the inertial force of the arm section 3 and reduce the burden on the worker.

[0031] The present invention is not limited to the above-described embodiment. Other embodiments of the present invention will be described below, but redundant description of points similar to those of the above-described embodiment will be omitted.

[0032] For example, in addition to the brakes 31 to 33, a brake may be provided on the joint (rotating shaft 11) provided at the tip of the arm unit 3. In this case, when the nut runner 4 tightens the nut, the brakes 31 to 33 restrict the rotation of the rotating shafts 7 to 9, and the brake restricts the rotation of the rotating shaft 11, thereby reliably preventing the arm unit 3 from moving due to the reaction force caused by the tightening of the nut. Meanwhile, since the nut runner 4 is mainly the only part provided on the tip side of the joint (rotating shaft 11) at the tip of the arm unit 3, the inertial force is not very large. Therefore, when the nut runner 4 is moved and approaches the nut N, only the brakes 31 to 33 may be activated as in the above embodiment, and the brake at the tip of the arm unit 3 may not be activated. Of course, all brakes, including the brake at the tip of the arm unit 3, may be activated at this time.

[0033] An elevator mechanism for raising and lowering the base end of the arm unit 3 may also be provided. In this case, the rotary shaft 9 for rotating the second arm 6 in a vertical plane relative to the first arm 5 can be omitted. In this case, a height sensor for detecting the height of the elevator mechanism may be provided in addition to the angle sensors 21 and 22 described above as a position detection means. The position of the nut runner 4 is calculated from the rotation angles of the rotary shafts 7 and 8 detected by the angle sensors 21 and 22 and the height of the base end of the arm unit 3 detected by the height sensor. In this case, an elevator brake for braking the elevation of the elevator mechanism may also be provided. When the nut runner 4 approaches the next nut to be tightened, the brakes 31 and 32 brake the rotation of the rotary shafts 7 and 8, and the elevator brake brakes the elevation of the base end of the arm unit 3, thereby canceling the inertial force of the arm unit 3. Note that at this time, only the joint brakes 31 and 32 may be activated, and the elevator brake may not be activated.

[0034] In the above embodiment, when the nut runner 4 is moved to approach the next nut to be tightened, all of the brakes 31 to 33 provided on the joints of the arm unit 3 are activated, but this is not limiting, and some of the brakes may not be activated. For example, when the nut runner 4 is moved to the tightening position, if it moves mainly in a horizontal plane and the amount of vertical movement is small (i.e., if the amount of rotation of the rotation shaft 9 is small), the brake 33 that brakes the joint for vertical rotation of the nut runner 4 (rotation shaft 9) may not be activated, and only the brakes 31 and 32 that brake the joint for horizontal rotation of the nut runner 4 (rotation shafts 7 and 8) may be activated.

[0035] Furthermore, as a position detection means for detecting the position of the nut runner 4, a proximity sensor that detects without contact when the nut runner 4 approaches the next nut to be tightened may be provided on the tip of the arm portion 3 or on the nut runner 4. In this case, when the nut runner 4 is moved to the next nut to be tightened, if the proximity sensor detects that the distance between the nut runner 4 and the nut is equal to or less than a predetermined value, the brakes 31 to 33 are activated to decelerate the nut runner 4.

[0036] Furthermore, the tool attached to the arm portion 3 is not limited to a nut runner, but may be, for example, an electric screwdriver for tightening screws, or a holder (such as a hook or clamp) for holding a heavy object. [Explanation of symbols]

[0037] 1. Assist arm device 2. Bass 3 Arm section 4 Nutrunner (tool) 5. First Arm 6 Second Arm 7, 8, 9, 11 Rotation axis (joint) 10,12 bracket 13 cylinders 21, 22, 23 Angle sensor (position detection means) 31, 32, 33 Brakes

Claims

1. An assisting arm device comprising an arm having a joint, a tool attached to the tip of the arm, position detection means for detecting the position of the tool, and a brake provided at the joint of the arm, When the tool is moved to a working position, if the position detecting means detects that the tool has approached the working position, the brake is activated to brake the rotation of the joint of the arm portion; an assisting arm device that activates the brake when the tool is moved to the working position and then releases the brake before the tool comes to a complete stop;

2. 2. An assisting arm device according to claim 1, wherein said position detecting means detects the position of said tool based on the rotation angle of the joint of said arm portion.

3. A control method for an assisting arm device including an arm having a joint, a tool attached to the tip of the arm, a position detection means for detecting the position of the tool, and a brake provided at the joint of the arm, When the tool is moved to a working position, if the position detecting means detects that the tool has approached the working position, the brake is activated to brake the rotation of the joint of the arm portion; A control method for an assisting arm device, which activates the brake when moving the tool to the working position and then releases the brake before the tool comes to a complete stop.

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