Tool position detection device and tool position detection system

Abstract

A tool position detection device (3) is provided with: a photoelectric sensor (7) that is capable of detecting a timing of cutting off an optical path (L) by a wire (10b); a support frame (8) that supports the photoelectric sensor (7); and a rotary actuator (12) that rotates the support frame (8) by 90° forward and backward about the rotation axis (C1) orthogonal to the optical path (L). A deviation amount calculation unit (6a) calculates, on the basis of the movement velocity V of the wire (10b) and the difference Δt between the reference value t1 and an actual measurement value t2 of the timing of cutting off the optical path (L) by the wire (10b), the positional deviation amount ΔS of the wire (10b) = V×Δt.

Description

Tool position detection device and tool position detection system

[0001] The present invention relates to a tool position detection device and a tool position detection system for detecting the position of a tool attached to the end of an arm of an industrial robot.

[0002] In recent years, many production lines in factories have been using a large number of industrial robots to efficiently carry out production. Various tools necessary for performing tasks are attached to the ends of the arms of these industrial robots, and productivity is increased by having the robots perform tasks repeatedly using these tools. However, the tools attached to such industrial robots may unexpectedly come into contact with surrounding objects during use or may deviate from a predetermined standard state due to maintenance, etc., which may cause subsequent production to be hindered.

[0003] To address this, devices that detect whether the position of a tool is deviated from a reference state are commonly known. For example, a tool position detection device disclosed in Patent Document 1 is capable of detecting the position of a tool attached to the end of an arm of an industrial robot, and includes two sets of photoelectric sensors each having a light-projecting unit that projects light and a light-receiving unit that receives the light projected from the light-projecting unit, and a support frame that supports the two sets of photoelectric sensors. The support frame is generally U-shaped in plan view and is composed of a first frame extending horizontally and a pair of second frames extending horizontally in the same direction parallel to each other from each end of the first frame. The light-emitting unit of one photoelectric sensor is provided on the tip side of one second frame, while the light-receiving unit of one photoelectric sensor is provided on the base end side of the other second frame, the light-emitting unit of the other photoelectric sensor is provided on the base end side of one second frame, while the light-receiving unit of the other photoelectric sensor is provided on the tip side of the other second frame, and a first optical path formed by light projected by one photoelectric sensor and a second optical path formed by light projected by the other photoelectric sensor intersect at a predetermined position. Each photoelectric sensor is capable of detecting timing at which the tool interrupts the first optical path or the second optical path. After controlling the industrial robot so that the tool crosses and interrupts the first optical path and the second optical path, a difference between a reference value and an actual value for the timing at which the tool interrupts the first optical path or the second optical path is calculated to detect the amount of positional deviation of the tool from a reference position in two directions.

[0004] European Patent No. 1722935

[0005] However, in the tool position detection device of Patent Document 1, because two sets of photoelectric sensors are arranged so that the first optical path and the second optical path intersect in a plan view, the support frame that supports each of the photoelectric sensors has a wide horizontal structure. This limits the area in which the tool can move around the device, restricting the operation of the industrial robot or making the teaching of tool operation complicated. Furthermore, two sets of photoelectric sensors are required to detect the amount of misalignment of the tool in two directions, which increases costs.

[0006] To avoid this, one possible method is to use a single photoelectric sensor and use an industrial robot to change the orientation of the tool relative to the optical path of the photoelectric sensor in two ways, crossing and blocking the optical path in each direction, thereby detecting the amount of positional deviation of the tool in two directions.

[0007] However, in the case of articulated industrial robots, which are often used on production lines, changing the tool orientation between two different positions requires complex rotation of the axes of all of the joints on the arm, which takes time to change the tool orientation and increases the time required to detect the amount of misalignment.

[0008] The present invention has been made in view of the above points, and an object of the present invention is to provide a low-cost tool position detection device and a tool position detection system including the same, which enable wide and effective use of the space around the device, and which can efficiently detect the amount of tool misalignment.

[0009] In order to achieve the above object, the present invention is characterized in that a mechanism is provided that can change the optical path of one photoelectric sensor in two directions.

[0010] Specifically, the target is a tool position detection device that detects the position of a tool attached to the end of an arm of an industrial robot, and the following measures have been taken.

[0011] That is, a tool position detection device according to a first aspect of the present invention includes a photoelectric sensor configured to project light to form an optical path and capable of detecting when the tool interrupts the optical path; a support frame supporting the photoelectric sensor; an optical path switching mechanism capable of switching the direction of the optical path by rotating the support frame forward and backward by a predetermined angle around a rotation axis perpendicular to the optical path; and a control unit connected to the photoelectric sensor and the optical path switching mechanism and controlling the forward and reverse rotation of the optical path switching mechanism. The control unit is characterized by including a deviation amount calculation unit that calculates the amount of position deviation of the tool based on the moving speed of the tool and the difference between a reference value and an actual value of the timing when the tool interrupts the optical path. This tool position detection device operates by consolidating the photoelectric sensor into a single device. Furthermore, this increases the tool's movable area around the device, thereby reducing restrictions on the operation of industrial robots. Furthermore, the rotation of the optical path switching mechanism about one axis changes the orientation of the tool relative to the optical path of the photoelectric sensor.

[0012] A tool position detecting device according to a second aspect of the present invention is the tool position detecting device of the first aspect of the present invention, wherein the support frame includes a first frame extending horizontally and having the rotation axis extending vertically at the center, and a pair of second frames extending upward from each end of the first frame, and the photoelectric sensor includes a light-projecting unit provided on one of the second frames for projecting the light, and a light-receiving unit provided on the other second frame for receiving the light from the light-projecting unit, the light-projecting unit and the light-receiving unit facing each other in the horizontal direction. A tool position detecting device configured in this manner acts to make it easier for a tool to access the optical path of the photoelectric sensor not only from the side but also from above.

[0013] A tool position detecting device according to a third aspect of the present invention is the tool position detecting device of the second aspect, characterized in that a continuous hollow portion is formed inside the first frame and the second frame, a communication hole is formed in the lower center of the first frame that communicates with the hollow portion, and a pair of signal lines are arranged in the hollow portion, one end of which is connected to the light-emitting unit and the other end of which is extended outside the first frame via the communication hole and connected to the control unit. This tool position detecting device prevents the signal lines connected to the photoelectric sensor from being exposed around the device. Furthermore, the signal lines are gathered around the rotation center of the support frame and extended outside the support frame.

[0014] A fourth aspect of the present invention is a tool position detection device according to any one of the first to third aspects, wherein the optical path switching mechanism is a rotary actuator driven by compressed air supplied and exhausted via an electromagnetic valve. The tool position detection device configured in this manner operates to enable quick forward and reverse rotation of the support frame.

[0015] The present invention also relates to a tool position detection system, and provides the following solution. That is, a tool position detection system according to a fifth aspect of the present invention includes any one of the first to third tool position detection devices and the industrial robot connected to the control unit, wherein the control unit controls the optical path switching mechanism to rotate in a forward direction so that the optical path is in a first direction, and controls the industrial robot to move the tool at a constant speed in a horizontal direction from a predetermined first reference position to block the optical path by the tool, and then controls the optical path switching mechanism in a reverse direction so that the optical path is in a second direction different from the first direction, and controls the industrial robot to move the tool at a constant speed in a horizontal direction from a predetermined second reference position to block the optical path by the tool, and the deviation amount calculation unit is configured to calculate a first positional deviation amount of the tool when the optical path is in the first direction and a second positional deviation amount of the tool when the optical path is in the second direction. The tool position detection system configured in this manner operates to detect the amount of deviation in two directions while minimizing the movement of the tool.

[0016] The tool position detection device of the first invention includes only one photoelectric sensor, resulting in a compact structure in a predetermined horizontal direction. This allows for more efficient use of the space around the device. Furthermore, the compact structure of the device in a predetermined horizontal direction increases the tool's movable area around the device. This reduces restrictions on the operation of the industrial robot and allows for more efficient teaching of tool operation. Furthermore, since only one photoelectric sensor is required for the device, the manufacturing cost of the device can be reduced. Furthermore, since the tool orientation relative to the optical path of the photoelectric sensor is changed by rotating a single axis of the optical path switching mechanism, rather than by rotating multiple axes of the industrial robot, the tool orientation relative to the optical path of the photoelectric sensor can be changed by rotating a single axis of the optical path switching mechanism, thereby enabling detection of tool misalignment in two directions in a short time.

[0017] In the tool position detection device of the second invention, the tool can easily access the optical path of the photoelectric sensor not only from the side but also from above, thereby eliminating unnecessary movement in the tool operation controlled by the industrial robot when the tool crosses and blocks the optical path, and efficiently detecting the amount of deviation of the tool in two directions.

[0018] In the tool position detection device of the third invention, the signal wires connected to the photoelectric sensors are not exposed around the device, so that the signal wires connected to the photoelectric sensors can be prevented from coming into contact with objects around the device when the support frame is rotating. This prevents device failure due to signal wire breakage. Furthermore, because the signal wires are gathered at the rotation center of the support frame and extended outside the support frame, the two signal wires do not become intricately entangled when the support frame is rotating, and signal wire breakage can be reliably prevented.

[0019] In the tool position detecting device of the fourth invention, the support frame can be quickly rotated forward and backward, so that the amount of deviation of the tool in two directions can be detected efficiently.

[0020] The tool position detection system of the fifth aspect of the present invention can detect misalignment in two directions while minimizing tool movement, thereby reliably reducing the time required for misalignment detection and enabling efficient tool misalignment detection work.

[0021] 5 is a perspective view showing a tool position detection system according to an embodiment of the present invention; FIG. 6 is a view equivalent to FIG. 1 with a sensor unit rotated 90°; FIG. 7 is a cross-sectional view taken along line III-III in FIG. 2; FIG. 8 is a diagram illustrating a method for detecting a tool misalignment and illustrating a calculation formula; FIG. 9 is a first half of a flowchart showing a procedure for detecting a tool misalignment using a tool position detection system according to an embodiment of the present invention; FIG. 10 is a second half of a flowchart showing a procedure for detecting a tool misalignment using a tool position detection system according to an embodiment of the present invention; FIG. 5 is a perspective view showing a tool position detection device according to an embodiment of the present invention, illustrating details of the operation of the tool position detection device performed in steps S1 to S5 of FIG. 5; FIG. 6 is a perspective view showing a tool position detection device according to an embodiment of the present invention, illustrating details of the operation of the tool position detection device performed in steps S6 to S8 of FIG. 5; FIG. 7 is a perspective view showing a tool position detection device according to an embodiment of the present invention, illustrating details of the operation of the tool position detection device performed in steps S9 to S13 of FIG. 5 and FIG. 8; FIG. 9 is a perspective view showing a tool position detection device according to an embodiment of the present invention, illustrating details of the operation of the tool position detection device performed in steps S14 to S18 of FIG. 6. 7 is a perspective view showing a tool position detection device according to an embodiment of the present invention, and shows details of the operation of the tool position detection device performed in steps S19 to S23 of FIG. 6.

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description of the preferred embodiment of the present invention is merely exemplary in nature.

[0023] 1 and 2 show a tool position detection system 1 according to an embodiment of the present invention. This tool position detection system 1 is composed of a six-axis articulated industrial robot 2 having a welding torch 10 (tool) for arc welding attached to the end of its arm, and a tool position detection device 3 capable of detecting the position of a wire 10b being paid out from the end of a contact tip 10a attached to the welding torch 10.

[0024] The tool position detection device 3 includes a sensor unit 4 that is approximately U-shaped and opens upward when viewed from the side, a device main body 5 that supports the sensor unit 4, and a control unit 6 that is connected to the sensor unit 4 and the device main body 5.

[0025] As shown in Figures 1 to 3, the sensor unit 4 includes a photoelectric sensor 7 having a light-projecting portion 7a that projects light and a light-receiving portion 7b that receives the light projected from the light-projecting portion 7a, and a support frame 8 that supports the photoelectric sensor 7.

[0026] The support frame 8 comprises a first frame 8a which extends horizontally and is a thick plate-like member, and a pair of second frames 8b which extend upward from each end of the first frame 8a and are also thick plate-like members, and the central portion of the first frame 8a has a bow-shaped shape in plan view that protrudes on both sides in the horizontal direction perpendicular to the longitudinal direction of the first frame 8a.

[0027] As shown in Figure 3, a groove portion 8c extending vertically and continuously opening from the upper end surface to the outer surface is formed on the upper (tip) portion of each second frame 8b, and a light guide hole 8d communicating with the corresponding groove portion 8c is formed on the opposing surfaces of the upper portion of each second frame 8b so as to extend along the direction in which both second frames 8b are arranged side by side.

[0028] The light-emitting portion 7a of the photoelectric sensor 7 is arranged in one groove portion 8c, while the light-receiving portion 7b of the photoelectric sensor 7 is arranged in the other groove portion 8c, with the light-emitting portion 7a and the light-receiving portion 7b arranged opposite each other in the horizontal direction.

[0029] The light projected from the light-projecting unit 7a passes through a light guide hole 8d formed in one of the second frames 8b, and then passes through a light guide hole 8d formed in the other of the second frames 8b to be received by the light-receiving unit 7b. In other words, an optical path L is formed between the light-projecting unit 7a and the light-receiving unit 7b, and the photoelectric sensor 7 can detect the timing when the optical path L is interrupted by the wire 10b of the welding torch 10.

[0030] A hollow portion S1 is formed between the inside of the first frame 8a and the inside of each second frame 8b from the middle to the lower part thereof.

[0031] A first communication hole 8e is formed in the upper part of each second frame 8b, connecting the groove portion 8c to the hollow portion S1, and a second communication hole 8f is formed in the lower center of the first frame 8a, connecting to the hollow portion S1.

[0032] A pair of signal wires 9 are arranged in the hollow portion S1, one end of which is connected to the light-emitting unit 7a and the light-receiving unit 7b via each of the first communication holes 8e, and the other end of each signal wire 9 is extended to the outside of the first frame 8a via the second communication hole 8f.

[0033] The device main body 5 comprises a main body case 11 having an approximately rectangular block shape extending horizontally, and a rotary actuator 12 (optical path switching mechanism) and an electromagnetic valve 13 housed in the internal space S2 of the main body case 11, with the rotary actuator 12 and the electromagnetic valve 13 arranged in order from top to bottom in the internal space S2.

[0034] An upper surface through-hole 11a communicating with the internal space S2 is formed in the center of the top surface of the main body case 11. Furthermore, a side surface through-hole 11b communicating with the internal space S2 is formed in the approximate center of one longitudinal end surface of the main body case 11, and a rubber wiring hole cap 11c is fitted into the side surface through-hole 11b.

[0035] The rotary actuator 12 is driven by compressed air supplied and exhausted via an electromagnetic valve 13, and comprises a thick, plate-shaped actuator body 12a, and a disk-shaped rotary table 12b provided at the center of the upper surface of the actuator body 12a and rotatable around a rotation axis C1 extending vertically.

[0036] The rotary table 12b is positioned facing the outside of the actuator body 12a through the upper surface through-hole 11a, and the first frame 8a is fixed to the upper surface of the rotary table 12b so that the rotation axis C1 is located in the center portion.

[0037] The rotary actuator 12 is capable of rotating the rotary table 12b forward and backward at an angle of 90° around the rotation axis C1, and this rotational movement switches the support frame 8 between a first state in which the parallel arrangement direction of both second frames 8b coincides with the horizontal direction perpendicular to the longitudinal direction of the main body case 11, and a second state in which the parallel arrangement direction coincides with the longitudinal direction of the main body case 11, as shown in Figures 1 and 2, thereby switching the direction of the optical path L between the first direction d1 and the second direction d2, respectively.

[0038] As shown in Figure 3, a central hole 12c that penetrates vertically is formed in the center of the actuator main body 12a and the rotary table 12b, and the other ends of both signal lines 9 pass through the central hole 12c and the side through-hole 11b of the main body case 11 in that order, and are connected to the control unit 6 located outside the main body case 11.

[0039] The control unit 6 controls the forward and reverse rotation of the rotary actuator 12. As shown in Fig. 4, the control unit 6 is provided with a deviation amount calculation unit 6a that calculates a positional deviation amount ΔS = V × Δt of the wire 10b based on the moving speed of the wire 10b, i.e., the moving speed V of the industrial robot 2, and the difference Δt between a reference value (time t1) and an actual measured value (time t2) of the timing at which the light path L is interrupted by the wire 10b, and a display unit 6b that displays the results calculated by the deviation amount calculation unit 6a.

[0040] For example, as shown in Figure 4, after the wire 10b is moved to a predetermined position and measurement is started at the same time, the time t until the timing at which the light path L is blocked is t = 3 seconds when there is no positional misalignment of the wire 10b, but t = 3.2 seconds when there is a positional misalignment of the wire 10b.In this case, the timing at which the light path L is blocked by the wire 10b is off by 0.2 seconds, and if the robot movement speed V is 20 mm / s, the positional misalignment amount ΔS is 20 x 0.2 = 4 mm.

[0041] For convenience, the longitudinal direction of the main body case 11 is defined as the X direction, the horizontal direction perpendicular to the longitudinal direction of the main body case 11 as the Y direction, and the vertical direction as the Z direction.

[0042] As shown in Figure 7, the control unit 6 controls the industrial robot 2 so that the tip of the wire 10b moves at a constant speed in the Z direction from a predetermined reference position P1 located on the rotation axis C1 to a reference position P2 located directly below this reference position P1, thereby blocking the light path L with the wire 10b.

[0043] At this time, the deviation amount calculation unit 6a calculates the amount of vertical positional deviation H of the wire 10b.

[0044] The control unit 6 controls the rotary actuator 12 to rotate in the normal direction so that the optical path L is in a first direction d1 along the Y direction, and controls the industrial robot 2 so that the wire 10b moves in the X direction from a predetermined reference position P3 (first reference position) at a constant speed as shown in FIG. 8, thereby blocking the optical path L with the wire 10b, or controls the industrial robot 2 so that the wire 10b moves in the X direction from a predetermined reference position P5 (first reference position) at a constant speed as shown in FIG. 9, thereby blocking the optical path L with the wire 10b, and then controls the industrial robot 2 to move in the X direction from a predetermined reference position P5 (first reference position) at a constant speed as shown in FIG. 10. As shown in FIG. 11 , the rotary actuator 12 is controlled to rotate in the reverse direction so that the light path L is oriented in a second direction d2 along the X direction different from the first direction d1, and the industrial robot 2 is controlled so that the wire 10b moves in the Y direction from a predetermined reference position P8 (second reference position) at a constant speed, thereby blocking the light path L with the wire 10b. Alternatively, as shown in FIG. 11 , the industrial robot 2 is controlled so that the wire 10b moves in the Y direction from a predetermined reference position P10 (second reference position) at a constant speed, thereby blocking the light path L with the wire 10b.

[0045] At this time, the deviation amount calculation unit 6a calculates a first positional deviation amount D of the wire 10b when the optical path L is in the first direction d1. １ (First positional deviation amount D １ '), and the second positional deviation amount D of the wire 10b when the optical path L is in the second direction d2. ２ (First positional deviation amount D ２ ') and are calculated respectively.

[0046] Next, a detailed description will be given of a procedure for detecting the amount of misalignment in two directions of the wire 10b of the welding torch 10 by the tool position detection system 1. The misalignment detection operation is started in a state in which the control unit 6 controls the rotary actuator 12 to rotate forward so that the light path L is in the first direction d1.

[0047] As shown in FIG. 5, first, in step S1, the control unit 6 controls the industrial robot 2 to move the arm so that the tip of the wire 10b of the welding torch 10 reaches a position P1 located on the rotation axis C1 (see FIG. 7).

[0048] Next, in step S2, the control unit 6 controls the industrial robot 2 to start moving the arm along the Z direction so that the tip of the wire 10b of the welding torch 10 reaches position P2 located on the rotation axis C1, and receives a measurement start signal from the industrial robot 2, proceeding to step S3.

[0049] In step S3, it is determined whether or not the optical path L is interrupted before the wire 10b reaches position P2, i.e., whether or not the control unit 6 has received an interruption timing signal from the photoelectric sensor 7. If the determination in step S3 is YES, i.e., if the wire 10b has interrupted the optical path L, the process proceeds to step S4, where the deviation amount calculation unit 6a calculates the positional deviation amount H in the Z direction, and then the process proceeds to step S5.

[0050] On the other hand, if the determination in step S3 is NO, that is, if the wire 10b does not block the light path L, it is determined that the position of the wire 10b is significantly deviated from the normal state, and the detection of the amount of deviation is terminated.

[0051] In step S5, the control unit 6 controls the industrial robot 2 to move the arm, thereby causing the tip of the wire 10b of the welding torch 10 to reach position P3, which is significantly away from the light path L to one side in the X direction, and then proceeds to step S6.

[0052] In step S6, the control unit 6 controls the industrial robot 2 to start moving the arm along the X direction so that the tip of the wire 10b of the welding torch 10 reaches position P4 located on the other side of the X direction, and then receives a measurement start signal from the industrial robot 2 and proceeds to step S7 (see FIG. 8).

[0053] In step S7, it is determined whether the optical path L is interrupted before the wire 10b reaches position P4, i.e., whether the control unit 6 has received an interruption timing signal from the photoelectric sensor 7. If the determination in step S7 is YES, i.e., if the wire 10b has interrupted the optical path L, the process proceeds to step S8, in which the deviation amount calculation unit 6a calculates the first positional deviation amount D in the X direction on the base end side of the wire 10b. １ After calculating, the process proceeds to step S9.

[0054] On the other hand, if the determination in step S7 is NO, that is, if the wire 10b does not block the light path L, it is determined that the position of the wire 10b is significantly deviated from the normal state, and the detection of the amount of deviation is terminated.

[0055] In step S9, the control unit 6 controls the industrial robot 2 to move the arm, thereby causing the tip of the wire 10b of the welding torch 10 to reach position P5, which is located directly above position P4 and spaced a predetermined distance from position P4, and then proceeds to step S10 (see Figure 9).

[0056] In step S10, the control unit 6 controls the industrial robot 2 to start moving the arm along the X direction so that the tip of the wire 10b of the welding torch 10 reaches position P6 located on one side of the X direction, and then receives a measurement start signal from the industrial robot 2 and proceeds to step S11.

[0057] In step S11, it is determined whether or not the optical path L is interrupted before the wire 10b reaches position P6, i.e., whether or not the control unit 6 has received an interruption timing signal from the photoelectric sensor 7. If the determination in step S11 is YES, i.e., if the wire 10b has interrupted the optical path L, the process proceeds to step S12, where the deviation amount calculation unit 6a calculates the first positional deviation amount D in the X direction of the tip end side of the wire 10b. １After calculating ', the process proceeds to step S13 as shown in FIG.

[0058] In step S13, the control unit 6 controls the industrial robot 2 to move the arm, thereby causing the tip of the wire 10b of the welding torch 10 to reach position P7, which is significantly away from the light path L to one side in the Y direction, and then proceeds to step S14.

[0059] In step S14, the industrial robot 2 outputs an optical path switching signal to the control unit 6. Then, the control unit 6 controls the rotary actuator 12 to rotate in the reverse direction so that the optical path L is switched to the second direction d2, and then the process proceeds to step S15 (see FIG. 10).

[0060] In step S15, it is determined whether the optical path L has been switched to the second direction d2, i.e., whether the rotary table 12b of the rotary actuator 12 has been rotated 90° in the reverse direction. If the determination in step S15 is YES, i.e., if the optical path L has been switched to the second direction d2, the process proceeds to step S16.

[0061] In step S16, the control unit 6 controls the industrial robot 2 to start moving the arm along the Y direction so that the tip of the wire 10b of the welding torch 10 reaches position P8 located on the other side of the Y direction, and receives a measurement start signal from the industrial robot 2 and proceeds to step S17.

[0062] In step S17, it is determined whether the optical path L is interrupted before the wire 10b reaches position P8, i.e., whether the control unit 6 has received an interruption timing signal from the photoelectric sensor 7. If the determination in step S17 is YES, i.e., if the wire 10b has interrupted the optical path L, the process proceeds to step S18, in which the deviation amount calculation unit 6a calculates the second positional deviation amount D in the Y direction on the base end side of the wire 10b. ２ After calculating, the process proceeds to step S19.

[0063] On the other hand, if the determination in step S17 is NO, that is, if the wire 10b does not block the light path L, it is determined that the position of the wire 10b is significantly deviated from the normal state, and the detection of the amount of deviation is terminated.

[0064] In step S19, the control unit 6 controls the industrial robot 2 to move the arm, thereby causing the tip of the wire 10b of the welding torch 10 to reach position P9, which is located directly above position P8 and spaced a predetermined distance from position P8, and then proceeds to step S20 (see Figure 11).

[0065] In step S20, the control unit 6 controls the industrial robot 2 to start moving the arm along the Y direction so that the tip of the wire 10b of the welding torch 10 reaches position P10 located on one side of the Y direction, and receives a measurement start signal from the industrial robot 2 and proceeds to step S21.

[0066] In step S21, it is determined whether or not the optical path L is interrupted before the wire 10b reaches the position P10, i.e., whether or not the control unit 6 has received an interruption timing signal from the photoelectric sensor 7. If the determination in step S21 is YES, i.e., if the wire 10b has interrupted the optical path L, the process proceeds to step S22, where the deviation amount calculation unit 6a calculates the second positional deviation amount D in the Y direction at the tip side of the wire 10b. ２ After calculating ', the process proceeds to step S23.

[0067] On the other hand, if the determination in step S21 is NO, that is, if the wire 10b does not block the light path L, it is determined that the position of the wire 10b is significantly deviated from the normal state, and the detection of the amount of deviation is terminated.

[0068] In step S23, the industrial robot 2 outputs an optical path switching signal to the control unit 6. Then, the control unit 6 rotates the rotary actuator 12 forward so that the optical path L is switched to the first direction d1, and returns the sensor unit 4 to its original position, thereby completing the misalignment amount detection operation.

[0069] As described above, according to the embodiment of the present invention, the tool position detecting device 3 includes only one photoelectric sensor 7, so that the tool position detecting device 3 has a compact structure in a predetermined horizontal direction. Therefore, the space around the tool position detecting device 3 can be used widely and effectively.

[0070] Furthermore, the tool position detection device 3 has a compact structure in a predetermined horizontal direction, which increases the movable area of ​​the wire 10b of the welding torch 10 around the tool position detection device 3. This reduces restrictions on the operation of the industrial robot 2 and makes it possible to efficiently teach the operation of the wire 10b of the welding torch 10.

[0071] Furthermore, only one photoelectric sensor 7 is required for the tool position detection device 3, which reduces the manufacturing cost of the tool position detection device 3. In addition, instead of changing the orientation of the wire 10b of the welding torch 10 with respect to the optical path L of the photoelectric sensor 7 by rotating the industrial robot 2 about multiple axes, the orientation of the wire 10b of the welding torch 10 with respect to the optical path L of the photoelectric sensor 7 is changed by rotating the rotary actuator 12 about one axis, so that the amount of deviation of the wire 10b of the welding torch 10 in two directions can be detected in a short time.

[0072] Furthermore, because support frame 8 has a generally U-shape that opens upward in side view, wire 10b of welding torch 10 can easily access optical path L of photoelectric sensor 7 from above as well as from the side. Therefore, when wire 10b of welding torch 10 crosses optical path L of photoelectric sensor 7 and interrupts it, unnecessary movement of wire 10b of welding torch 10 controlled by industrial robot 2 can be eliminated, and the amount of misalignment of wire 10b of welding torch 10 in two directions can be efficiently detected.

[0073] Furthermore, since the signal wire 9 connected to the photoelectric sensor 7 is not exposed around the tool position detection device 3, it is possible to prevent the signal wire 9 connected to the photoelectric sensor 7 from coming into contact with objects around the tool position detection device 3 when the support frame 8 is rotating. This makes it possible to prevent malfunctions of the tool position detection device 3 due to breakage of the signal wire 9. Furthermore, since the signal wires 9 are gathered at the rotation center of the support frame 8 and extended to the outside of the support frame 8, the two signal wires 9 do not become intricately entangled when the support frame 8 is rotating, and breakage of the signal wire 9 can be reliably prevented.

[0074] In addition, since the optical path L is switched by a rotary actuator 12 driven by compressed air, quick forward and reverse rotation of the support frame 8 is possible, and the amount of deviation in two directions of the wire 10b of the welding torch 10 can be detected efficiently.

[0075] Furthermore, since the direction of the optical path L of the photoelectric sensor 7 can be switched between two directions by the rotary actuator 12, it becomes possible to detect the amount of misalignment in two directions while minimizing the movement of the wire 10b of the welding torch 10. Therefore, the time required for detecting the amount of misalignment can be reliably reduced, and the work of detecting the amount of misalignment of the wire 10b of the welding torch 10 can be performed efficiently.

[0076] In the embodiment of the present invention, the light-projecting unit 7a is arranged on one of the second frames 8b, while the light-receiving unit 7b is arranged on the other second frame 8b, thereby forming an optical path L; however, this is not limited to this, and for example, it is also possible to arrange both the light-projecting unit 7a and the light-receiving unit 7b on one of the second frames 8b, while placing a reflector on the other second frame 8b, so that light is projected from the light-projecting unit 7a and reflected back by the reflector and received by the light-receiving unit 7b, thereby forming an optical path L between the two second frames 8b.

[0077] Furthermore, in the embodiment of the present invention, the sensor unit 4 is configured to rotate forward and backward by 90° around the rotation axis C1, but the rotation angle does not have to be 90°. For example, the sensor unit 4 may be configured to rotate forward and backward by 45° around the rotation axis C1, or may be configured to rotate forward and backward by 135°.

[0078] Furthermore, in the embodiment of the present invention, a rotary actuator 12 that operates by supplying or discharging compressed air is used to switch the direction of the optical path L, but this is not limited to this, and it may also be configured, for example, to rotate forward and reverse using a motor with an encoder.

[0079] Furthermore, in the embodiment of the present invention, the sensor unit 4 is configured with a support frame 8 that is approximately U-shaped when viewed from the side, but this is not limited to this, and the sensor unit 4 may also be configured with a support frame 8 that is V-shaped when viewed from the side.

[0080] Furthermore, the tool position detection system 1 of the embodiment of the present invention detects the position of the wire 10b of the welding torch 10, but it can also detect the position of other tools attached to the arm tip of the industrial robot 2.

[0081] The present invention is suitable for a tool position detection device that detects the position of a tool attached to the end of an arm of an industrial robot.

[0082] REFERENCE SIGNS LIST 1 Tool position detection system 2 Industrial robot 3 Tool position detection device 4 Sensor unit 5 Device body 6 Control unit 6a Displacement amount calculation unit 6b Display unit 7 Photoelectric sensor 7a Light emitting unit 7b Light receiving unit 8 Support frame 8a First frame 8b Second frame 8c Groove portion 8d Light guide hole 8e First communication hole 8f Second communication hole 9 Signal line 10 Welding torch 10a Contact tip 10b Wire 11 Body case 11a Top surface through-hole 11b Side surface through-hole 11c Wiring hole cap 12 Rotary actuator (light path switching mechanism) 12a Actuator body 12b Rotary table 12c Central hole 13 Solenoid valve d1 First direction d2 Second direction C1 Rotation axis D １ , D １ ' First positional deviation amount D ２ , D ２ ' Second positional deviation amount H Positional deviation amount in Z direction L Optical path S1 Hollow portion S2 Internal space V Moving speed

Claims

1. A tool position detection device that detects the position of a tool attached to the end of an arm of an industrial robot, comprising: a photoelectric sensor configured to project light to form an optical path and capable of detecting the timing at which the optical path is interrupted by the tool; a support frame that supports the photoelectric sensor; an optical path switching mechanism that can switch the direction of the optical path by rotating the support frame forward and backward at a predetermined angle around a rotation axis that is perpendicular to the optical path; and a control unit that is connected to the photoelectric sensor and the optical path switching mechanism and controls the forward and reverse rotation operation of the optical path switching mechanism, wherein the control unit has a deviation amount calculation unit that calculates the amount of positional deviation of the tool based on the moving speed of the tool and the difference between a reference value and an actual value for the timing at which the optical path is interrupted by the tool.

2. A tool position detection device as claimed in claim 1, wherein the support frame comprises a first frame extending horizontally with the rotation axis extending vertically at the centre, and a pair of second frames extending upward from each end of the first frame, and the photoelectric sensor comprises a light-projecting unit provided on one of the second frames for projecting the light, and a light-receiving unit provided on the other second frame for receiving the light from the light-projecting unit, the light-projecting unit and the light-receiving unit facing each other horizontally.

3. A tool position detection device as described in claim 2, wherein a continuous hollow portion is formed inside the first frame and the second frame, and a communication hole is formed in the lower center of the first frame that communicates with the hollow portion, and a pair of signal lines are arranged in the hollow portion, one end of which is connected to the light-emitting unit and the light-receiving unit, and the other end of which is extended outside the first frame via the communication hole and connected to the control unit.

4. A tool position detection device according to any one of claims 1 to 3, wherein the optical path switching mechanism is a rotary actuator driven by compressed air supplied and exhausted via an electromagnetic valve.

5. A tool position detection system comprising the tool position detection device according to any one of claims 1 to 3 and an industrial robot connected to the control unit, wherein the control unit controls the optical path switching mechanism to rotate in the forward direction so that the optical path is in a first direction, and controls the industrial robot so that the tool moves at a constant speed in a horizontal direction from a predetermined first reference position, thereby causing the tool to block the optical path, and then controls the optical path switching mechanism to rotate in the reverse direction so that the optical path is in a second direction different from the first direction, and controls the industrial robot so that the tool moves at a constant speed in a horizontal direction from a predetermined second reference position, thereby causing the tool to block the optical path, and the deviation amount calculation unit is configured to calculate a first positional deviation amount of the tool when the optical path is in the first direction and a second positional deviation amount of the tool when the optical path is in the second direction, respectively.

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