JP3700390B2 - Spot welding gun tip wear detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spot welding gun tip wear amount detecting apparatus capable of detecting the wear amount of a spot welding gun while polishing the tip of the spot welding gun.
[0002]
[Prior art]
A spot welder is generally used for the production of automobiles and the like. This spot welder performs spot welding by pressurizing a work to be welded with a pair of tips provided in a spot welding gun and energizing between the tips.
[0003]
In the spot welding process, in order to improve the reliability of welding, the spot welding gun is managed so that constant welding conditions can be maintained at all times (for example, tip dressing, tip advance / retraction correction, etc.)
[0004]
For example, the tip is worn while being used for spot welding, and its tip is roughened. For this reason, in the spot welding process, every time welding is performed a predetermined number of times, the tip is shaped and polished by a polishing device (tip dresser) so that the tip has a constant shape and area, and the tip is smoothened. I'm doing dress work.
[0005]
Recently, a servo gun is frequently used as a spot welding gun. However, since this servo gun adjusts the applied pressure according to the advance / retreat position of the tip, it is necessary to accurately grasp the wear amount of the tip. For example, when a new chip is attached, the origin position in the forward / backward direction of the chip is determined, how much the tip is advanced from this original position, and how much pressure is applied from the contacted position. However, after the tip is worn out or the tip dressing operation is performed, the workpiece cannot be pressurized to the initially planned pressure with the specified advance / retreat amount. For this reason, in the spot welding process, the tip wear amount is periodically detected, and the advance / retreat amount is corrected in accordance with the wear amount so that the applied pressure of the workpiece becomes a specified pressure.
[0006]
Such detection of the amount of chip wear and the correction of the amount of advancement / retraction associated therewith are usually performed at the same time as the above-described chip dressing operation. As known techniques for detecting the chip wear amount, for example, Japanese Patent Application Laid-Open No. 7-284957 and Japanese Patent Application No. 10-000513 are listed.
[0007]
[Problems to be solved by the invention]
In the inventions described in Japanese Patent Application Laid-Open Nos. 7-284957 and 10-000513, the chip dressing operation and the chip wear amount detecting operation are separately performed. For this reason, a dedicated place and equipment are required for each process.
[0008]
In addition, as described above, since the chip wear amount detection and the chip dress are performed every time a predetermined number of times welding is performed, the cycle time of the spot welding process is extended by the time required for both, As a result, the productivity of spot welding is adversely affected.
[0009]
The present invention has been made in view of the above points, and can reduce and reduce the space and equipment required for chip dress work and chip wear amount detection work, as well as chip dress and chip wear. An object of the present invention is to provide a spot welding gun tip wear amount detection device capable of shortening the amount detection time and realizing spot welding with higher production efficiency.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is configured as follows.
That is, according to the first aspect of the present invention, the tip dressing part that shapes and polishes the pair of tips while being sandwiched by the pair of tips provided in the spot welding gun, and the tip is sandwiched by the tips when the tip is polished. The chip dress part is configured integrally with the chip dress part so that the position of the chip dress part can be detected, the position of the chip dress part when the chip is shaped and polished, and when the chip is unused And a wear amount detecting unit that detects a displacement of the tip dress portion as a wear amount of a fixed tip fixed to a welding gun among the pair of tips.
[0011]
With this configuration, when the tip dressing operation is completed, the wear amount can be detected while the tip is kept in this state, and the tip dressing operation and the wear amount can be detected simultaneously. Further, since the tip dress portion and the wear amount detection portion are integrally configured, the space occupied by both in the work area can be made common, and the work area can be reduced.
[0012]
According to a second aspect of the present invention, the wear amount detection unit includes a displacement sensor that detects a position of the chip dress portion sandwiched by the chip when the chip is shaped and polished, and the chip is shaped. A position detector that detects the position of a movable tip that moves up and down with respect to the welding gun when polished, and an initial position of the tip dress portion when sandwiched by the tip when the tip is unused, and A storage unit that stores an initial position of the movable chip, a detection result of the displacement sensor, and an error of an initial position of the chip dress unit that is stored in the storage unit are calculated to calculate the wear amount of the fixed chip. The amount of wear of the fixed tip is subtracted from the detection result of the position detector and the error of the initial position of the movable tip stored in the storage unit. It is characterized in that it has a wear amount calculating unit for calculating the amount of a.
[0013]
By configuring in this way, the wear amount of the chip can be calculated from the clamping position of the chip at the time of chip dressing, the chip is released from the chip dresser after chip dressing work, and the chip is used as a wear amount detection device for wear amount detection. No need to set again.
[0014]
According to a third aspect of the present invention, the movable chip is moved up and down by a servo motor, and the position detector detects a position of the movable chip based on a rotation amount of the servo motor. It is.
[0015]
With this configuration, when the movable chip is configured to move up and down by a servo motor, it is not necessary to newly provide a position detection unit for the movable chip, and the number of parts of the position detection unit can be reduced. Can do.
[0016]
According to a fourth aspect of the present invention, there is provided a chip dress portion for shaping and polishing the movable tip and the fixed tip while being sandwiched between a pair of tips comprising a movable tip and a fixed tip provided in a spot welding gun driven by a robot. If, while supporting the tip dress portions floated, and the chip address portion float-supporting portion which is displaced in response to a force exerted by the tip dress portions, so as to detect a displacement of the chip address portion float-supporting portion, The displacement sensor configured integrally with the chip dress portion, the position detector for detecting the position of the movable chip when the chip is shaped and polished, the unused movable chip and the fixed chip when clamping the chip address portion, of the displacement detector of the tip dress float-supporting portion which is detected by the displacement A storage unit for storing an initial position of the movable tip detected by the period detection value and the position detector, the error between the initial detection value stored in the detection result and the storage portion of the displacement sensor is calculated The amount of wear of the fixed chip is calculated by subtracting the amount of wear of the fixed chip from the detection result of the position detector and the error of the initial position of the movable chip stored in the storage unit. And a wear amount calculation unit that calculates the wear amount .
[0017]
With this configuration, the wear amount of the movable tip and the wear amount of the fixed tip can be calculated respectively. Further, it is possible to divert the driving amount of the movable tip that is used when the robot drives the welding gun, and it is not necessary to newly provide a configuration for detecting the position of the movable tip. The number of parts can be reduced.
[0020]
【The invention's effect】
According to the first aspect of the present invention, when the chip dressing operation is completed, the wear amount can be detected while the chip is left in this state, and the chip dressing operation and the wear amount can be detected simultaneously. Further, since the tip dress portion and the wear amount detection portion are integrally configured, the space occupied by both in the work area can be made common, and the work area can be reduced.
[0021]
Therefore, the time required for the tip dressing operation and the subsequent tip polishing can be shortened, and consequently the cycle time of spot welding can be shortened. In addition, the work area can be used effectively.
[0022]
According to the second aspect of the present invention, the wear amount of the chip can be calculated from the clamping position of the chip at the time of chip dressing. No need to set again.
[0023]
Therefore, the time required for the tip dressing operation and the subsequent tip polishing can be shortened, and consequently the cycle time of spot welding can be shortened.
[0024]
According to the third aspect of the present invention, when the movable chip is configured to move up and down by a servo motor, it is not necessary to newly provide a position detection unit for the movable chip, and the number of parts of the position detection unit is reduced. As a result, the structure of the tip wear amount detecting device of the spot welding gun can be simplified.
[0025]
The invention according to claim 4 can calculate the wear amount of the movable tip and the wear amount of the fixed tip, respectively, and can detect the wear amount of the tip in more detail. Therefore, if the teaching data at the time of spot welding is corrected using such data, the state of spot welding can be determined more accurately, and spot welding can be performed with high accuracy.
[0026]
Further, it is possible to divert the driving amount of the movable tip that is used when the robot drives the welding gun, and it is not necessary to newly provide a configuration for detecting the position of the movable tip. The number of parts can be reduced.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating the overall configuration of a spot wear gun tip wear amount detection apparatus (hereinafter referred to as a tip dresser) according to the present embodiment. 2 is a perspective view for explaining the chip dresser 41 shown in FIG. 1. FIG. 3 is a block diagram for explaining the configuration of the control device 46. As shown in FIG.
[0029]
The apparatus shown in FIG. 1 includes a robot 42 that drives and supports a welding gun 43, a tip dresser 41 that performs tip dressing operation and wear amount detection on the tips 21a and 21b of the welding gun 43, a tip dresser 41, welding. The control unit 46 controls both the gun 43.
In the present embodiment, the control device 46 is shared with the control device for spot welding performed by the welding gun 43.
[0030]
The welding gun 43 has a tip 21 b fixed to the gun arm 43 a and a tip 21 a that moves up and down by a servo motor 44. The rotation amount of the servo motor 44 is detected by a position detector 23 (FIG. 4) such as an encoder, and the rotation amount of the servo motor 44 is converted to detect the position of the chip 21a based on a preset position. are doing. Therefore, the position detector 23 functions as a wear amount detector.
[0031]
In the present embodiment, the encoder of the servo motor 44 is used for the position detection sensor 23, but this position detection sensor is uniquely provided for inputting the position of the chip 21a to the control device 46. It may be.
[0032]
The chip dresser 41 of the present embodiment has both functions of chip dress and chip wear amount detection, and can simultaneously perform chip dress and chip wear amount detection. For this purpose, the chip dresser 41 floats the chip dress part 1, the bracket 9 for fixing the chip dress part 1, the guide 6 provided on the bracket 9, and the chip dress part 1 as shown in FIG. 2. The spring 8 is supported in a state, and a displacement sensor 10 such as an encoder for detecting the vertical displacement of the chip dress portion 1 is provided. The displacement sensor 10 functions as a wear amount detection unit.
[0033]
The chip dress portion 1 includes a cutter blade 2 that polishes the chips 21 a and 21 b, a motor 3 that rotates the cutter blade 2, and a belt 5 and a pulley 4 that transmit the rotation of the motor 3 to the cutter blade 2. Further, the chip dressing part 1 is configured to be sandwiched between the upper and lower chips 21a and 21b and pressurized so that they can be dressed at one time. For this reason, the cutter blade 2 has a chip dressing part as shown in FIG. 1 is provided on the upper and lower surfaces.
[0034]
The control device 46 includes a calculation unit 15 and a storage unit 12 as shown in FIG.
The calculation unit 15 receives a signal a representing the position of the chip 21a from the position detection sensor 23 provided in the servo motor 44 of the robot 42, and a signal c representing the displacement of the chip dressing unit 1 from the chip dresser 41. The result is fed back to the robot 42 as a signal b. The storage unit 12 stores data necessary for the calculation of the calculation unit 15, and the detection values of the displacement sensor 10 and the position detection sensor 23 in a state where the chips 21 a and 21 b are not worn, and further the chip dress. The position coordinates to be performed and the polishing conditions for chip dressing work are also stored here. Therefore, the calculation unit 15 functions as a wear amount calculation unit, and the storage unit 12 functions as a chip initial position storage unit or an initial detection value storage unit.
[0035]
Further, as described above, the control device 46 is shared with the spot welding control device. For this reason, the storage device 12 also stores the position coordinates and movement order of each spot welding spot, the pressing position of the workpiece by the tip (hereinafter collectively referred to as teaching data), and the like.
[0036]
Next, the operation performed by the configuration including the chip dresser 41 described above will be specifically described.
[0037]
When the chip dressing operation of the chips 21 a and 21 b is started, the control device 46 drives the arm of the robot 12 and moves the chips 21 a and 21 b to the coordinates stored in the storage unit 12. For example, the centers of the chips 21a and 21b that are not worn are located at the center of the cutter blade 2 (x, y coordinates), and the chips 21a and 21b apply a predetermined pressure to the cutter blade 2 (z coordinates). ) Is set.
[0038]
Accordingly, the chips 21a and 21b move to the center of the cutter blade 2 with the chips 21a and 21b open, and then the chips 21a are lowered and the cutter blade 2 is clamped with a predetermined pressure.
[0039]
The pressure force between the chips 21a and 21b is detected by utilizing, for example, the fact that the feedback current from the servo motor 44 increases with the rotational torque of the servo motor. That is, the feedback current i corresponding to the predetermined pressure f is stored in the storage unit 12 in advance, and when the detected feedback current reaches the current i stored in advance, between the chips 21a and 21b. It is determined that a predetermined pressure has been applied, and the servo motor 44 is stopped.
[0040]
Next, the motor 3 is rotated to chip-dress the chips 21a and 21b under a predetermined condition. After completion of the chip dressing operation, the control device 46 fixes the chips 21a and 21b at the positions at the end of the chip dressing operation. At this time, the lower tip 21b is in contact with the cutter blade 2 in a state after polishing, and is in a position to displace the tip dress portion 1 supported by the spring 8 by a predetermined amount (B). This position is smaller than the displacement amount A detected by the displacement sensor 10 without performing the chip dressing when the chip is new. The displacement amount A is stored in the storage unit 12.
The computing unit 15 compares the displacement amount B with the displacement amount A stored in the storage unit 12, and stores this difference (A−B) in the storage unit 12 as the wear amount of the chip 21b.
[0041]
Next, the control device 46 detects the amount of rotation of the servo motor 44 with the position detection sensor 23, and detects the position (C) of the chip 21a. The storage unit 12 stores a detection value (referred to as D) of the position detection sensor 23 when the chips 21a and 21b are not worn (when new).
[0042]
The calculation unit 15 compares the detected position C with the position D stored in the storage unit 12. At this time, if the chips 21a and 21b are worn, the position C is positioned below the position D. Further, the difference (C−D) between the position C and the position D includes both wear amounts of the chip 21a and the chip 21b. Therefore, a value CD−A + B obtained by subtracting the wear amount AB of only the tip 21b detected earlier from CD is stored in the storage unit 12 as the wear amount of the chip 21a.
[0043]
By the way, the teaching data stored in the storage unit 12 is set so that the lengths of the chips 21a and 21b are not worn. For this reason, when the chips 21a and 21b are worn, even if the chip 21a is advanced or retracted according to the teaching data, the chip is more than the one when the chip is new and the one when the chip was dressed last time. Since the length is shorter, it becomes impossible to pressurize the workpiece with a predetermined pressure. That is, the applied pressure is reduced by the amount of wear.
[0044]
This seriously affects the welding quality. Therefore, the controller 46 corrects the spot welding teaching data from the wear amounts of the chips 21 a and 21 b stored in the storage unit 12.
[0045]
FIG. 5 is a flowchart for explaining a series of processing for detecting the chip wear amount described above.
When the chip dressing operation is started, first, the robot 42 reaches the original position where the operation starts (S1). Then, the welding gun 43 is approached to the position coordinates for performing the chip dressing operation stored in the storage unit 12, the chip dressing unit 1 is sandwiched and pressed (S2), and the polishing conditions stored in the storage unit 12 are also stored. The chip dressing operation is started at (polishing time etc.) (S3).
[0046]
When the tip dressing operation is completed (S4), the calculation unit 15 detects the amount of displacement detected by the displacement sensor 10 while the welding gun 43 is fixed to the position coordinates stored in the storage unit 12 where the tip dressing operation has been performed. Then, the position of the chip 21a detected by the position detection sensor 23 is input (S5).
[0047]
Then, the displacement amount detected by the displacement sensor 10 among the input values is compared with the displacement amount in the state where the chip 21b stored in the storage unit 12 is not worn, and the wear amount of only the chip 21b is calculated. Next, the position of the chip 21a detected by the position detection sensor 23 is compared with the amount of displacement stored in the storage unit 12 when both the chips 21a and 21b are not worn, and the amount of wear of both the chips 21a and 21b is compared. The sum is calculated, the amount of wear of only the tip 21b calculated previously is subtracted from this value to calculate the amount of wear of the tip 21a (S6), and the robot 42 is returned to the original position again (S7).
After the above processing is completed, the teaching data is corrected based on both the calculated chips 21a and 21b (S8), and the chip dressing operation is completed.
[0048]
In the present embodiment described above, the process of detecting the wear amount after the end of the chip dressing process is conventionally performed, but the chip dressing process and the detection of the wear amount can be performed simultaneously. For this reason, the time that the chip dressing operation occupies within the cycle time of spot welding can be made substantially zero, and the productivity of spot welding can be increased.
[0049]
Further, as a chip wear amount detection device, conventionally, a chip dresser and a wear amount detection device have to be provided separately, and a space occupied by two devices has been required. On the other hand, in the configuration of the present embodiment, the chip dresser and the wear amount detection device are integrated, and the installation space of the device can be reduced.
[0050]
Further, by correcting the spot welding teaching data based on the detected amount of wear, spot welding can be performed using the teaching data corresponding to the actual tip state.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an overall configuration to which a chip dresser according to an embodiment of the present invention is applied.
FIG. 2 is a perspective view for explaining the chip dresser shown in FIG. 1;
FIG. 3 is a block diagram for explaining the control device shown in FIG. 1;
4 is a diagram illustrating a state of a chip that is chip-dressed by the chip dresser of FIG. 2; FIG.
FIG. 5 is a flowchart illustrating processing according to an embodiment of the present invention.
[Explanation of symbols]
1 ... Chip dress part
10: Displacement sensor,
12 ... storage unit,
15 ... arithmetic unit,
21a, 21b ... chip 41 ... chip dresser,
43 ... Welding gun,
44. Servo motor,
46: Control device.

Claims (4)

A tip dressing part for shaping and polishing the pair of tips while being sandwiched by the pair of tips provided in the spot welding gun;
The chip dress formed integrally with the chip dress portion so that the position of the chip dress portion sandwiched by the chip can be detected when the chip is shaped and polished, and the chip dress when the chip is shaped and polished A wear amount detection unit that detects a displacement between the position of the tip and the position of the tip dress portion when the tip is not used as the wear amount of a fixed tip fixed to a welding gun among the pair of tips. When,
A tip welding amount detection device for a spot welding gun. The wear amount detector is
A displacement sensor for detecting the position of the chip dress portion held by the chip when the chip is shaped and polished;
A position detector that detects the position of a movable tip that moves up and down with respect to the welding gun when the tip is shaped and polished;
A storage unit that stores an initial position of the chip dress unit and an initial position of the movable chip when sandwiched between the chips when the chip is unused;
The detection result of the displacement sensor and the error of the initial position of the chip dress part stored in the storage part are calculated to calculate the wear amount of the fixed chip, and the detection result of the position detector and the storage part are calculated. A wear amount calculation unit that calculates the wear amount of the movable tip by subtracting the wear amount of the fixed tip from the stored initial position error of the movable tip;
Tip wear amount detecting apparatus of the spot welding gun according to claim 1, wherein a. 3. The spot wear gun tip wear according to claim 2, wherein the movable tip is moved up and down by a servo motor, and the position detector detects the position of the movable tip based on a rotation amount of the servo motor. Quantity detection device. A tip dressing part for shaping and polishing the movable tip and the fixed tip while being sandwiched between a pair of tips comprising a movable tip and a fixed tip provided in a spot welding gun driven by a robot;
A tip dress portion floating support portion that supports the tip dress portion in a floating state while being displaced according to a force applied by the tip dress portion;
A displacement sensor configured integrally with the chip dress portion so as to detect the displacement of the tip dress portion floating support portion;
A position detector for detecting the position of the movable chip when the chip is shaped and polished;
An initial detection value of displacement of the chip dress floating support portion detected by the displacement detection portion and detected by the position detector when the tip dress portion is sandwiched between the unused movable tip and the fixed tip . A storage unit for storing an initial position of the movable chip;
An error between the detection result of the displacement sensor and the initial detection value stored in the storage unit is calculated to calculate the wear amount of the fixed chip, and the detection result of the position detector and the storage unit are stored. A wear amount calculation unit that calculates the wear amount of the movable tip by subtracting the wear amount of the fixed tip from the error of the initial position of the movable tip;
Tip wear amount detecting apparatus of the spot welding gun, characterized in that it comprises a.

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