JP2002219581A - Method and apparatus for detecting dressing abnormality of electrode tip - Google Patents

Abstract

(57) [Problem] To easily and reliably detect dressing abnormality of an electrode tip with a simple process and configuration, and to perform a high-precision welding operation. A control device includes a CPU and a memory.
The CPU 60 includes a wear amount detection processing unit 72 for detecting the wear amount of the electrode tip, and whether a dressing abnormality has occurred in the electrode tip based on each wear amount detected before and after the dressing operation. And an abnormality determining unit 74 for detecting whether or not there is no error.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting an abnormal dressing of an electrode tip for detecting an abnormal dressing of an electrode tip provided on a welding gun.

[0002]

2. Description of the Related Art For example, a resistance welding machine for automatically and continuously performing a welding operation by sequentially moving a welding gun mounted on a robot to a plurality of welding points of a workpiece has been widely used. In this type of resistance welding machine, a plurality of welding operations are performed on the work while sandwiching each welding point of the work with a pair of electrode tips. At this time, the electrode tip is dressed every predetermined number of welding points so that the electrode tip can perform a better welding operation.

[0003] Therefore, usually, the limit wear amount (wear amount) of the electrode tip is set in advance, and the wear amount of each electrode tip is detected. When one of the electrode tips reaches the limit wear amount, An operation of replacing the electrode tip is being performed. The detection of the amount of wear of the electrode tip is performed after a dressing operation is performed on the electrode tip.

In this detection of the amount of wear, the distance between the electrode tips is corrected in accordance with the length of wear of the electrode tips, and the pressurizing distance of the electrode tips is maintained constant to maintain the pressurizing time constant. Doing, in order to keep the surface pressure difference between the pair of electrode tips during pressurization constant, to move the robot by the amount of wear of the fixed-side electrode tips, and to detect the replacement time of the electrode tips, And so on.

[0005]

In this case, the above-described detection of the amount of wear is based on the premise that the dressing operation of the electrode tip is always performed accurately. However, in a general dressing apparatus, when the grinding process is continued, clogging or chipping of the dresser blade is caused to cause insufficient dressing (insufficient dress), and the dressing time becomes longer and the dressing time becomes longer. Excessive dressing (excess dress) due to poor position or the like is likely to occur.

However, the above-described detection of the amount of wear cannot detect such a dressing defect, and a suitable dressing operation may not be reliably performed on the electrode tip. As a result, a problem has been pointed out that welding accuracy is significantly reduced in a welding gun incorporating an electrode tip in which a dressing defect has been caused.

The present invention solves this kind of problem. An electrode capable of easily and reliably detecting a dressing defect of an electrode tip with a simple process and configuration and performing a high-precision welding operation. An object of the present invention is to provide a method and an apparatus for detecting a dressing abnormality of a chip.

[0008]

According to the electrode tip dressing abnormality detecting method and apparatus according to the present invention, when the electrode tip is subjected to a predetermined number of welding operations, after the electrode tip is subjected to the dressing operation, A wear amount of the electrode tip is detected. Next, it is determined whether or not the detected wear amount is within a reference wear range set based on the electrode tip wear amount detected before the dressing operation. Then, when the detected wear amount is outside the reference wear range, it is detected that a dressing abnormality has occurred in the electrode tip.

As described above, by detecting the amount of wear of the electrode tip before and after the dressing operation, a dressing defect of the electrode tip can be easily and reliably detected with a simple process and configuration.

Further, the wear ratio of one electrode tip and the other electrode tip with respect to the wear amount is set in advance, and after the electrode tips are idled and the wear amount is detected, each of the electrode tips is determined based on the wear ratio. The wear limit and dressing abnormality of each electrode tip are detected. This eliminates the need to individually detect the wear amount for each electrode tip, effectively simplifies control and configuration, and accurately and quickly detects the wear limit and dressing abnormality of each electrode tip. It becomes possible.

Further, the wear amount of the electrode tip detected after the dressing operation is stored, and the wear amount of the electrode tip detected after the previous dressing operation and the electrode tip wear detected after the current dressing operation are stored. Based on the wear amount, it is detected whether or not a dressing abnormality has occurred in the electrode tip. Therefore, the dressing abnormality of the electrode tip is easily and reliably detected.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic structural explanatory view of a resistance welding system 10 incorporating a dressing abnormality detecting device for carrying out a method for detecting a dressing abnormality of an electrode tip according to an embodiment of the present invention.

The resistance welding system 10 includes a multi-indirect welding robot 12, a control device 14 which is a dressing abnormality detection device according to the present embodiment, and receives a dressing abnormality from the control device 14 to display the dressing abnormality. In addition, the operating device 16 for the operator to perform various operations such as data input, and the electrode tips 20a and 20b constituting the electric welding gun 18 mounted on the welding robot 12.
And a tip dresser 22 for performing a dressing operation.

An equalizing mechanism 26 having springs 24a and 24b is provided at the distal end of the welding robot 12, and an electric welding gun 18 is mounted via the equalizing mechanism 26. The electric welding gun 18 is
A movable electrode tip 20a which is set in a so-called C-shaped welding gun structure and is driven vertically by an internal servomotor 28, and a fixed electrode tip which is fixed to a substantially C-shaped arm 30 20b, and the work P can be gripped by the pair of electrode tips 20a and 20b.

As shown in FIG. 2, the servo motor 28
A motor housing 32, a plurality of electromagnets 34 arranged annularly inside the lower portion of the motor housing 32, a hollow rotor 38 to which an annular permanent magnet 36 facing the electromagnet 34 is fixed, and a housing cover 40. have. The rotor 38 is rotatably supported via a plurality of bearings 42.

A nut member 44 is inserted into the rotor 38, and the upper end of the hollow rod 46 is fixed to the nut member 44. At the lower end of this hollow rod 46,
The electrode tip 20a is mounted via the holder 48. A feed screw 50 screwed with the nut member 44 is inserted into the hollow rod 46, and the rotation of the rotor 38 is controlled by the nut member 44 and the feed screw 50.
A feed screw mechanism 52 for converting the vertical movement into the vertical movement 6 is constituted.

A rotor 38 is provided above the servo motor 28.
An encoder 54 for detecting the rotation angle of the electrode chip 20a is provided via the encoder 54.
Is detected.

As shown in FIG. 3, the control device 14 has a CPU
A memory 62 is connected to the CPU 60. The CPU 60 receives position data 66 of the electrode tip 20 a from the encoder 54 via the encoder interface 64. The position data 66 is also input to a chip position control unit 68 for controlling the servomotor 28, and the chip position control unit 68
Connected to U60. The CPU 60 outputs an abnormal signal to the operation device 16 via the external interface 70.

The CPU 60 includes the electrode chips 20a, 20b
After the dressing operation, the electrode tip 20
a, a wear amount detection processing unit (wear amount detection means) 72 for detecting the wear amount of the electrode tip 20a, wherein the detected wear amount is detected before the dressing operation;
It is determined whether it is within a reference wear range set based on the wear amount of 20b, and when it is outside the reference wear range,
An abnormality determination unit (an abnormality determination unit) 74 that detects that a dressing abnormality has occurred in the electrode tips 20a and 20b.
And

The memory 62 includes the electrode chips 20a, 20b
A dressing grinding amount storage unit 78 for storing the dressing grinding amount of the electrode tip 20a which has not been used before the welding operation;
A tip position initial state storage unit 80 that stores the initial position states of the electrode tips 20a and 20b based on the position data 66 from the encoder 54 when the blanks 20b are hit with each other;
Each electrode tip 20a detected after the dressing operation,
Tip position previous state storage unit 8 for storing the wear amount of 20b
2 and a wear ratio storage unit 84 for storing the wear ratio of one electrode tip 20a and the other electrode tip 20b with respect to the amount of wear.

The resistance welding system 1 configured as described above
Operation 0 will be described below with reference to the flowcharts shown in FIGS. 4 and 5 in relation to the dressing abnormality detection method according to the present embodiment.

First, the unused electrode tips 20a, 20b
Is mounted on the welding gun 18, and the wear limit and wear ratio of the electrode tips 20a and 20b are set in advance (step S1). The wear ratio of the electrode tips 20a and 20b is set, for example, to 6: 4 for the movable-side electrode tip 20a and the fixed-side electrode tip 20b.

Then, the electric welding gun 18 is driven by a command from the control device 14, and the electrode tips 20a, 20
b performs an idle shot before the start of welding (step S2). Specifically, a drive signal is sent from the chip position control unit 68 to the servomotor 28, and as shown in FIG.
4, a magnetic field is generated under the action of the electromagnet 34 and the permanent magnet 36. Therefore, the rotor 38 of the servo motor 28 rotates, and the feed screw 50 constituting the feed screw mechanism 52 rotates.

A nut member 44 is screwed into the feed screw 50, and the hollow rod 46 fixed to the nut member 44 moves in the direction of arrow A along the axial direction of the feed screw 50. Therefore, the electrode tip 20a held by the holder 48 fixed to the distal end of the hollow rod 46 abuts on the electrode tip 20b, and the electrode tips 20a, 20
The blanking of b is performed.

At this time, an encoder 54 disposed above the servo motor 28 detects the rotation angle of the rotor 38 constituting the servo motor 28 and
The stroke amount of a is detected. The pulse signal from the encoder 54 is converted into position data 66 by an encoder interface 64, and the position data 66
60 and the chip position control unit 68. CPU6
0, the input position data 66 is
It is stored in the chip position initial state storage unit 80 as the initial position states a and 20b (step S3).

Next, the welding robot 12 is operated, and the electric welding gun 18 is moved to a predetermined welding portion of the work P. Then, the electrode tip 20a mounted on the electric welding gun 18 advances and retreats with respect to the workpiece P under the action of the servomotor 28, thereby the electrode tip 20a,
A welding operation is started on the work P via the line 0b (step S4).

When a predetermined number of welding operations are performed on the workpiece P via the electrode tips 20a and 20b (step S).
5, YES), the welding gun 12 moves to the tip dresser 22, and the electrode tips 20a, 20b are dressed (step S6). This electrode tip 2
The tip portions of 0a and 20b are dressed simultaneously or individually via the tip dresser 22.

After the dressing operation is completed, the electrode tips 20a and 20b are idled in the same manner as described above (step S7), and based on the pulse signal from the encoder 54,
The wear amount of the electrode tips 20a, 20b is calculated (step S8). Here, the wear amount calculated by the wear amount detection processing unit 72 of the CPU 60 is determined by the electrode tip 20a,
It is the amount of wear of the entire 20b.

For this reason, the wear amount of each of the electrode tips 20a and 20b is calculated based on the wear ratio set in advance in step S1. Specifically, when the detected overall wear amount is 10 mm, the electrode tips 20a, 2a
Since the wear ratio of Ob is set to 6: 4, the wear amount of the electrode tip 20a is recognized as 6 mm, and the wear amount of the electrode tip 20b is recognized as 4 mm.

Next, it is determined whether or not one of the electrode tips 20a is at the wear limit (step S9). As shown in FIG. 6, after the welding operation is performed a predetermined number of times (W1 to W4), a dressing operation (D
1), the wear amount T1 of the electrode tip 20a
Is determined to exceed a predetermined wear limit T0. When the wear amount T1 of the electrode tip 20a is equal to or less than the wear limit T0 (NO in step S9),
Proceeding to step S10, it is determined whether or not a wear abnormality has occurred in the electrode tip 20a.

That is, in FIG. 6, the wear amount T1 of the electrode tip 20a detected by the wear amount detection (K1) after the dressing operation (D1) and the wear amount detection (Ka) (or the initial state detection) before the dressing operation are performed. The difference from the wear amount T2 of the electrode tip 20a detected in (K0)) is
It is determined whether it is within a preset reference wear range.

Specifically, if the wear amount T1 after the dressing operation is within the range of the wear amount T3 to the wear amount T4 set based on the wear amount T2 before the dressing operation, the dressing of the electrode tip 20a is performed. It is determined that the operation is normally performed (see FIG. 7A). On the other hand, when the wear amount T1 is equal to or smaller than the wear amount T3 or equal to or larger than the wear amount T4, it is determined that a dressing abnormality has occurred in the electrode tip 20a.

When the wear amount T1 after the dressing operation is equal to or less than the wear amount T3, a shortage of dress is caused due to chipping of the tip dresser 22 (see FIG. 7B). on the other hand,
When the wear amount T1 after the dressing operation is equal to or larger than the wear amount T4, it is detected that the dressing time is long or the dressing position is defective, and that the dressing is abnormal (excessive dress) (FIG. 7C).

If an abnormal wear has occurred in the electrode tip 20a, the operation proceeds to step S11, in which the CPU 60 transmits a dressing abnormality to the operating device 16 via the external interface 70, and the operating device 16 detects the abnormal dressing. Display and notify the operator. On the other hand, when the wear limit and the wear abnormality do not occur in the electrode tip 20a, the process proceeds to step S12, and the other electrode tip 20b
It is determined whether or not a wear limit has occurred.

If the wear limit has not occurred in the electrode tip 20b (NO in step S12), step S13
Then, it is determined whether or not a wear abnormality has occurred in the electrode tip 12b. If a wear abnormality has occurred, the process proceeds to step S11, and a wear abnormality alarm is issued. If no wear abnormality has occurred, the process proceeds to step S14, in which the wear state of the electrode tips 20a, 20b is changed to the previous state. Stored as state. Further, step S5
After the welding of the workpiece P by the electrode tips 20a and 20b is performed a predetermined number of times (W5 to W8), the dressing operation (D2) of the electrode tips 20a and 20b is performed via the tip dresser 22.

Next, it is determined whether or not the electrode tips 20a and 20b are abnormally worn (K2) based on the previous state stored in the tip position previous state storage unit 82, that is, the wear amount T1 and the current time. (See FIG. 6). The wear amount T5 is equal to the wear amount T6 to T6.
7, the electrode tips 20a, 20
It is detected that no abnormal wear has occurred in b.

Similarly, after the welding and dressing work of the electrode tips 20a and 20b are performed, the wear limit (T0) is applied to the electrode tip 20a (or the electrode 20b).
Occurs (YES in step S9 or YES in step S12), the process proceeds to step S15, and a limit warning is issued. For this reason, the worker performs an operation of replacing the electrode tip 20a or 20b with a new electrode tip 20a or 20b (step S16).

In this case, in this embodiment, the welding operation by the electrode tips 20a and 20b constituting the electric welding gun 18 is performed a predetermined number of times.
After the dressing operation is performed on the electrode tips 20b via the tip dresser 22, the wear amount of the electrode tips 20a and 20b is detected. Then, it is determined whether or not the detected wear amount is within a reference wear range set based on the wear amount of the electrode tips 20a and 20b detected before the dressing operation. Detection of whether a dressing abnormality has occurred is performed.

As described above, since the presence or absence of a dressing abnormality is detected in addition to the wear limit (T0) of the electrode tips 20a and 20b, clogging or chipping of the tip dresser 22 is caused, resulting in insufficient dressing (FIG. 7B). (See FIG. 7C) or an excessive dress (see FIG. 7C) due to a longer dressing time or a defective dressing position, this kind of dressing defect can be easily and reliably detected.

Thus, the work of welding the work P is not performed using the electrode tips 20a and 20b in which the dressing defect has occurred, and the welding accuracy by the electric welding gun 18 can be constantly maintained high. The effect that it becomes possible is obtained. Moreover, the electrode tips 20a, 20b
It is only necessary to detect the amount of wear before and after the dressing work and compare the wear amounts, effectively simplifying the control and configuration, quickly detect dressing abnormalities, and perform highly accurate and efficient welding work Will be possible.

Further, the wear ratio of the electrode tips 20a, 20b is set in advance, and based on the pulse signal obtained from the encoder 54, the electrode tips 20a, 20b
Only by detecting the entire wear amount, each electrode tip 20a,
The wear amount of each of the 20b is easily and reliably detected.
Thus, there is an advantage that the wear limit (T0) and the wear abnormality (dressing abnormality) of each of the electrode tips 20a and 20b can be easily and quickly detected.

In this embodiment, as shown in FIG. 6, the wear amount T5 detected in the wear amount detection (K2) performed after the dressing operation (D2) is the wear amount detection (the previous wear amount). Although it is compared with the wear amount T1 detected in K1), instead of this, the wear amount detected in the wear amount detection (Kb) immediately before the dressing operation (D2) may be used as the previous wear amount. Good.

In the present embodiment, as shown in the flowchart of FIG. 5, after detecting the presence or absence of the wear limit (T0), the presence or absence of the wear abnormality (dressing abnormality) is detected. Alternatively, the wear limit may be detected after the abnormal wear is detected.

Further, in the present embodiment, the electrode tip 20
Although the abrasion amounts of a and 20b are detected based on the pulse signal from the encoder 54, the present invention is not limited to this. For example, a detection unit such as a photoelectric tube or a touch sensor attached to the outside may be used. it can. Furthermore, the explanation has been made using the electric welding gun 18 set in a C-type welding gun structure as the welding gun, but an X-type in which an electrode tip is attached to each of a pair of gun arms that can be opened and closed under the action of a pressurizing cylinder. A welding gun structure or the like may be used.

[0045]

According to the electrode tip dressing abnormality detecting method and apparatus according to the present invention, after the electrode tip is dressed, the amount of wear of the electrode tip is detected, and the detected amount of wear is determined as the reference wear. It is determined whether or not the electrode tip is within the range, and when it is within the reference wear range, it is detected that a dressing abnormality has occurred in the electrode tip. For this reason, by simply detecting the wear amount of the electrode tip before and after the dressing operation, it is possible to easily and reliably detect the dressing defect of the electrode tip, and to prevent the occurrence of welding defect as much as possible to achieve high precision. And efficient welding work can be performed. In addition, it is only necessary to detect the wear amount of the electrode tip, and the process and configuration are effectively simplified, and the cost is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic structural explanatory view of a resistance welding system incorporating a dressing abnormality detection device for implementing a method for detecting a dressing abnormality of an electrode tip according to the present invention.

FIG. 2 is a partially sectional explanatory view of an electric welding gun constituting the resistance welding system.

FIG. 3 is a schematic configuration diagram of the dressing abnormality detection device.

FIG. 4 is a flowchart (part 1) illustrating the dressing abnormality detection method.

FIG. 5 is a flowchart (part 2) illustrating the dressing abnormality detection method.

FIG. 6 is an explanatory diagram of the dressing abnormality detection method.

FIG. 7A is an explanatory view of an electrode tip that has been subjected to a normal dressing process, FIG. 7B is an explanatory view of an electrode tip with an insufficient dress, and FIG. 7C is an explanatory view of an electrode tip that is over-dressed. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Resistance welding system 12 ... Welding robot 14 ... Control device 16 ... Operating device 18 ... Electric welding gun 20a, 20
b ... Electrode tip 22 ... Tip dresser 26 ... Equalizing mechanism 28 ... Servo motor 38 ... Rotor 52 ... Feed screw mechanism 54 ... Encoder 60 ... CPU 66 ... Position data 68 ... Tip position control section 72 ... Abrasion amount detection processing section 74 ... Abnormal Judgment unit 78: Dressing grinding amount storage unit 80: Tip position initial state storage unit 82: Tip position previous state storage unit 84: Wear ratio storage unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Nakanishi 1-10-1 Shinsayama, Sayama City, Saitama Honda Engineering Co., Ltd. (72) Hiroshi Miwa 1-10-1 Shinsayama, Sayama City, Saitama Honda Engineering Co., Ltd. (72) Inventor Mitsugu Kaneko 1-10-1 Shinsayama, Sayama City, Saitama Prefecture Honda Engineering Co., Ltd. F-term (reference) 3C047 AA03

Claims (5)

[Claims] 1. An electrode tip dressing abnormality detecting method for detecting a dressing abnormality of an electrode tip provided in a welding gun, comprising: performing a welding operation a predetermined number of times with the electrode tip; Performing a dressing operation on the electrode tip; and, after the dressing operation, detecting a wear amount of the electrode tip; and the detected wear amount is based on the wear amount of the electrode tip detected before the dressing operation. A step of determining whether or not the amount is within a set reference wear range; and a step of detecting that a dressing abnormality has occurred in the electrode tip when the detected wear amount is outside the reference wear range. A method for detecting dressing abnormality of an electrode tip, comprising: 2. The dressing abnormality detecting method according to claim 1, further comprising the steps of: setting a wear ratio of one electrode tip and the other electrode tip to said wear amount; Detecting a wear limit and a dressing abnormality of each of the electrode tips based on the wear ratio after detecting the dressing abnormality. 3. A method for detecting a dressing abnormality according to claim 1 or 2, wherein a wear amount of said electrode tip detected after a dressing operation is stored, and a wear amount of said electrode tip detected after a previous dressing operation. And a step of detecting whether a dressing abnormality has occurred in the electrode tip based on the amount of wear of the electrode tip detected after the current dressing operation, and dressing the electrode tip. Anomaly detection method. 4. An electrode tip dressing abnormality detecting device for detecting a dressing abnormality of an electrode tip provided in a welding gun, wherein after the dressing operation is performed on the electrode tip, a wear amount of the electrode tip is measured. Abrasion amount detecting means for detecting, determining whether the detected abrasion amount is within a reference wear range set based on the abrasion amount of the electrode tip detected before the dressing operation, An abnormality determination unit configured to detect that a dressing abnormality has occurred in the electrode tip when the detected wear amount is outside the reference wear range. 5. The dressing abnormality detecting device according to claim 4, wherein a wear ratio of the one electrode tip and the other electrode tip to the wear amount is stored, and the wear amount of each electrode tip detected after the dressing operation is stored. An electrode chip dressing abnormality detection device comprising a memory for storing.