JP2014140867A - Spot welder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spot welder capable of reducing time required until a predetermined pressing force acts on a welding target member and thereby shortening welding cycle time.SOLUTION: A spot welder 1 for pressing and holding a workpiece 2 between a fixed electrode 7 and a movable electrode 33 and spot-welding the workpiece 2, calculates an elastic displacement amount of a compression coil spring 44 as a predetermined-pressing-force-corresponding elastic displacement amount S when a pressing force applied from the fixed electrode 7 and the movable electrode 33 to a to-be-welded region is equal to a predetermined pressing force F in response to a pressing force generated by feed mechanisms 17, 21, and 25 on three orthogonal axes and transmitted to the movable electrode 33 via the compression coil spring 44, and controls the feed mechanisms 17, 21, and 25 on three orthogonal axes so that the elastic displacement amount of the compression coil spring 44 is equal to the pre-calculated, predetermined-pressing-force-corresponding elastic displacement amount S.

Description

  The present invention relates to a spot welder that sandwiches and presses a member to be welded with a pair of electrodes to perform spot welding.

  Conventionally, for example, in the production of automobile parts, spot welding is performed by pressing and pressing a welding gun electrode against a member to be welded that is overlapped at least two sheets, and supplying a current to generate resistance heat between the members to be welded. Has been done. The quality of the joint formed by spot welding can be stabilized by appropriately managing the current value, current supply time, applied pressure, and electrode tip state.

As said welding gun, what was proposed by patent document 1, for example is widely used generally.
The welding gun according to this Patent Document 1 includes a pair of gun arms that are opened and closed by a servo motor with a joint member as a fulcrum, and electrodes are attached to the tip portions of these gun arms that face each other. The portion is sandwiched between a pair of electrodes, pressurized, and spot welded.

  By the way, in the thing of the structure which obtains pressurization using a servomotor like the welding gun which concerns on said patent document 1 as a drive source, the relationship between the electric current of a servomotor and pressurization is calculated | required, and it respond | corresponds to predetermined pressurization. For example, Japanese Patent Application Laid-Open No. H10-228707 is known that controls the motor current to control the pressure applied to the member to be welded.

JP-A-11-291062 JP-A-6-312273

  However, in the above-mentioned Patent Document 2, in order to apply a predetermined pressurizing force to the welded member, the actual pressurizing force (motor current value) actually applied to the welded member is fed back in real time. There is a problem that the time required for obtaining the predetermined pressure force becomes longer and the cycle time of spot welding becomes longer.

  The present invention has been made in view of the above-described problems, and can shorten the time until a predetermined pressure is applied to a member to be welded, thereby shortening the welding cycle time. An object of the present invention is to provide a spot welder capable of performing the above.

In order to achieve the above object, a spot welder according to the present invention comprises:
In a spot welding machine that sandwiches and pressurizes at least two or more members to be welded between a first electrode and a second electrode that can move relative to the first electrode to perform spot welding,
A pressing force generation mechanism that generates a pressing force to be pressed by the second electrode against a portion of the welded member that is scheduled to be spot welded;
An elastic body provided between the pressing force generation mechanism and the second electrode and elastically displaced according to the pressing force from the pressing force generation mechanism;
The pressing force applied from the first electrode and the second electrode to the planned welding site by transmitting the pressing force from the pressing force generating mechanism to the second electrode through the elastic body. A predetermined applied pressure equivalent elastic displacement amount calculating means for calculating an elastic displacement amount of the elastic body at a predetermined applied force as a predetermined applied force equivalent elastic displacement amount;
A pressing force generation mechanism control means for controlling the pressing force generation mechanism so that an elastic displacement amount of the elastic body becomes a predetermined pressing force equivalent elastic displacement amount calculated by the predetermined pressing force equivalent elastic displacement amount calculation means;
It is characterized by providing.

  In the present invention, the pressing force generation mechanism includes an X-axis feed mechanism that linearly moves the second electrode along the horizontal X-axis direction, and a horizontal Y-axis that is orthogonal to the horizontal X-axis direction. A Y-axis feed mechanism that linearly moves along the direction, and a Z-axis feed mechanism that linearly moves the second electrode along the vertical Z-axis direction perpendicular to the horizontal X-axis direction and the horizontal Y-axis direction, It is preferable that a θ-axis rotation mechanism that rotates the second electrode around a vertical θ-axis and an α-axis rotation mechanism that rotates the second electrode around a horizontal α-axis are provided (second invention).

  In the present invention, a pressure detection means for detecting an actual pressure applied from the first electrode and the second electrode to the welding planned site, and a pressure detected by the pressure detection means A pressure appropriateness determining means for determining whether or not the value is within a preset allowable range for the predetermined pressure, and when the pressure is determined to be inappropriate by the pressure appropriateness determining means It is preferable to provide an operation stop means for stopping the operation of the spot welder (third invention).

  According to the spot welding machine of the present invention, the pressing force generating mechanism is controlled so that the elastic displacement amount of the elastic body becomes the elastic displacement amount corresponding to the predetermined pressing force calculated in advance, whereby the predetermined pressing force is applied to the member to be welded. Therefore, there is no need to feed back the actual applied pressure (for example, motor current value) actually applied to the welded member in real time to correct the applied pressure. The time until the pressure is applied can be shortened as compared with the conventional one, whereby the welding cycle time can be shortened.

According to the spot welding machine of the second aspect of the invention, the pressing force generating mechanism functions as a pressurizing actuator for generating a pressurizing force on the planned welding site, and a moving mechanism for moving the second electrode in three orthogonal axes. As a configuration that also has a function as a device, it is possible to simplify the apparatus and to reduce the weight around the electrode as compared with the conventional one in which a pressurizing actuator is provided in the vicinity of the electrode. Speeding up of positioning can be achieved.
In addition, since a total of five axes including a horizontal X axis, a horizontal Y axis, a vertical Z axis, a vertical θ axis, and a horizontal α axis are provided as control axes, the second to the welding scheduled portion regardless of the shape of the member to be welded. The second electrode can be positioned so that the electrodes are in contact with each other in a vertical direction, and good spot welding can be performed regardless of the shape of the member to be welded.

  According to the spot welding machine of the third invention, when the value of the actual pressurizing force applied to the welding scheduled site is a value outside the allowable range set in advance for the predetermined pressurizing force, Therefore, the production of defective products can be surely avoided.

1 is an overall perspective view of a spot welder according to a first embodiment of the present invention. It is a top view of the spot welder of a 1st embodiment. (A) is a figure which fractures | ruptures and represents by the A arrow directional view of FIG. 2, (b) is a figure which fracture | ruptures and represents a part by the B arrow directional view of FIG. FIG. 4 is a view broken away and represented by a view in the direction of arrow C in FIG. 3. FIG. 4 is a cross-sectional view of an enlarged part D of FIG. 3. It is a functional block diagram of a control device. It is a figure showing the mode of positioning of the movable electrode with respect to a workpiece | work. It is a figure showing the mode of the action of the pressurization force of the movable electrode with respect to a workpiece | work. It is explanatory drawing of teaching operation | movement, predetermined pressurizing force equivalent elastic displacement calculation operation, and spot welding processing operation, (a) is a standby position state figure, (b) is an electrode contact position state figure, (c) is predetermined pressure equivalent elasticity. It is a displacement state figure. It is explanatory drawing of the spot welder which concerns on the 2nd Embodiment of this invention, (a) is a standby position state figure, (b) is the E section enlarged view of (a). It is explanatory drawing of the spot welding machine which concerns on the 2nd Embodiment of this invention, (a) is an electrode contact state figure, (b) is the G section enlarged view of (a). It is explanatory drawing of the spot welder which concerns on the 2nd Embodiment of this invention, (a) is a predetermined pressurizing force equivalent elastic displacement state figure, (b) is the H section enlarged view of (a).

  Next, specific embodiments of the spot welder according to the present invention will be described with reference to the drawings.

[First Embodiment]
<Overview of spot welder>
The spot welder 1 shown in FIG. 1 uses two (two or more) welded members 2a and 2b partially overlapped with each other as workpieces 2 to be spot welded, and these welded members 2a and 2b. Spot welding is performed on a predetermined portion to be welded in the superposed portion, and a bed 3 constituting the basis of the machine main body portion of the spot welder 1 is provided.

<Description of bed>
The bed 3 has a quadrangular shape in a plan view extending along the horizontal X axis and the horizontal Y axis perpendicular to each other in the horizontal direction, and has a required thickness along the vertical Z axis perpendicular to the X axis and the Y axis. Have.

<Description of index table>
On the bed 3, an index table 5 that can be rotated and indexed in the horizontal direction by an indexing motor 4 is installed.
A workpiece support 6 is installed on the index table 5, and the workpiece 2 is placed on the workpiece support 6.
A required fixed electrode 7 is fixed to the work support 6 so as to come into contact with the work to be welded on the work 2.

<Explanation of fixed electrode electrical wiring>
The fixed electrode 7 is connected to the negative pole of the power supply device (both not shown) through the index table 5, the bed 3 and a required cable by a bus bar (bar-shaped conductor) (not shown) from the work support 6.
In addition, although detailed description by illustration is abbreviate | omitted, in the current path | route from a power supply device to the fixed electrode 7, a current path | route is carried out between two members which move relatively, such as the bed 3 and the index table 5, for example, and other important points. A breaker is provided for mechanically connecting and disconnecting.

<Description of X-axis beam member and X-axis slider>
On one side of the bed 3 in the horizontal Y-axis direction, a pair of column members 8 are erected and fixed so as to be positioned on both sides in the horizontal X-axis direction, and the horizontal X-axis extends across the column members 8. An X-axis beam member 9 extending in the direction is fixed to the column members 8.
On the X-axis beam member 9, a pair of linear guides 10 extending in the horizontal X-axis direction and disposed at a predetermined interval in the horizontal Y-axis direction are provided, and the X-axis is linearly guided by these linear guides 10. A slider 11 is attached to be movable in the horizontal X-axis direction.

<Description of Y-axis beam member and Y-axis slider>
A Y-axis beam member 12 extending in the horizontal Y-axis direction is fixed to one end of the X-axis slider 11 in the horizontal X-axis direction.
On the surface of the Y-axis beam member 12 facing the other side in the horizontal X-axis direction, a pair of linear guides 13 extending in the horizontal Y-axis direction and arranged at a predetermined interval in the vertical Z-axis direction are provided. A Y-axis slider 14 that is linearly guided by these linear guides 13 is attached so as to be movable in the Y-axis direction.

<Description of Z-axis beam member and Z-axis slider>
As shown in FIG. 3A and FIG. 4, a Z-axis slider 15 is disposed on the other side of the Y-axis slider 14 in the horizontal X-axis direction, and between these Z-axis slider 15 and the Y-axis slider 14. Are provided with a pair of linear guides 16 extending in the vertical Z-axis direction and arranged at a predetermined interval in the horizontal Y-axis direction, and the Z-axis slider 15 is linearly guided by these linear guides 16 to move the Z-axis slider 15 to the Y-axis slider. 14 is movable in the vertical Z-axis direction.

<Description of X-axis feed mechanism>
As shown in FIG. 2, the X-axis feed mechanism 17 that moves the X-axis slider 11 in the horizontal X-axis direction includes a ball screw shaft 18 that extends in the horizontal X-axis direction. The ball screw shaft 18 is attached to the X-axis beam member 9 so as to be rotatable about its axis.
A ball nut 19 fixed to the X-axis slider 11 is screwed onto the ball screw shaft 18, and an X-axis feed motor 20 is connected to one end of the ball screw shaft 18 so as to transmit rotational power.
When the ball screw shaft 18 is rotationally driven by the operation of the X-axis feed motor 20, the ball nut 19 is linearly moved in the horizontal X-axis direction, and the X-axis slider 11 is moved to the horizontal X along with the linear movement of the ball nut 19. It is designed to move linearly in the axial direction.

<Description of Y-axis feed mechanism>
The Y-axis feed mechanism 21 that moves the Y-axis slider 14 in the horizontal Y-axis direction includes a ball screw shaft 22 that extends in the horizontal Y-axis direction. The ball screw shaft 22 is attached to the Y-axis beam member 12 so as to be rotatable about its axis.
A ball nut 23 fixed to the Y-axis slider 14 is screwed onto the ball screw shaft 22, and a Y-axis feed motor 24 is connected to one end of the ball screw shaft 22 so as to transmit rotational power.
When the ball screw shaft 22 is rotationally driven by the operation of the Y-axis feed motor 24, the ball nut 23 is linearly moved in the horizontal Y-axis direction, and the Y-axis slider 14 is moved horizontally in accordance with the linear movement of the ball nut 23. It is designed to move linearly in the axial direction.

<Description of Z-axis feed mechanism>
As shown in FIGS. 3A and 3B, the Z-axis feed mechanism 25 that moves the Z-axis slider 15 in the vertical Z-axis direction includes a ball screw shaft 26 that extends in the vertical Z-axis direction. . The ball screw shaft 26 is attached to the Y-axis slider 14 so as to be rotatable about its axis.
A ball nut 27 fixed to the Z-axis slider 15 is screwed onto the ball screw shaft 26, and a driven timing pulley 28 is fixed to one end portion (upper end portion) of the ball screw shaft 26.
The Y-axis slider 14 is provided with a Z-axis feed motor 29 at a predetermined inter-axis distance on one side in the horizontal X-axis direction with respect to the ball screw shaft 26. The drive timing pulley 30 is fixed.

  A timing belt 31 is wound around the drive timing pulley 30 and the driven timing pulley 28, and the rotational power of the Z-axis feed motor 29 is driven from the drive timing pulley 30 by the operation of the Z-axis feed motor 29. When transmitted to the ball screw shaft 26 via the timing belt 31 and the driven timing pulley 28, the ball nut 27 is linearly moved in the vertical Z-axis direction, and the Z-axis slider 15 is vertically moved along with the linear movement of the ball nut 27. It is designed to move linearly in the Z-axis direction.

<Description of welding gun>
A welding gun 32 is attached to the Z-axis slider 15.
The welding gun 32 is configured by mounting a movable electrode 33 on a welding gun main body 32a constituting the main body portion thereof.
The welding gun body 32 a is equipped with a θ-axis rotation mechanism 34 and an α-axis rotation mechanism 35.

<Description of movable electrode>
As shown in FIG. 5, the movable electrode 33 is configured by mounting an electrode tip 33 b that is substantially used for spot welding on the tip of a shank 33 a that constitutes the main body portion of the movable electrode 33. . The movable electrode 33 is attached to a movable electrode attachment 37 through a holder 36.

<Description of the θ-axis rotation mechanism>
The θ-axis rotating mechanism 34 rotates the movable electrode 33 around the vertical θ-axis, and is attached to the distal end portion of the welding gun main body 32a so as to be rotatable around the vertical θ-axis and supports the movable electrode attachment 37. A θ-axis rotation bracket 38 is provided. Rotational power from a θ-axis rotation motor 39 (see FIG. 3A) built in the welding gun main body 32 a is transmitted to the θ-axis rotation bracket 38. When the θ-axis rotating bracket 38 is rotationally driven by the operation, the movable electrode 33 is rotated around the vertical θ axis.
In the present embodiment, the rotation angle of the θ-axis rotating bracket 38 around the vertical θ axis is limited to a range of 0 ° to 180 °.

<Explanation of α axis rotation mechanism>
The α-axis rotation mechanism 35 rotates the movable electrode 33 around the horizontal α-axis, and includes an α-axis rotation housing 40 that constitutes a main body portion of the movable electrode attachment 37. The α-axis rotating housing 40 is attached to the θ-axis rotating bracket 38 so as to be rotatable around the horizontal α-axis.
Rotational power from the α-axis rotary motor 41 is transmitted to the α-axis rotary housing 40, and the α-axis rotary housing 40 is rotated around the horizontal α-axis by the operation of the α-axis rotary motor 41. Then, the movable electrode 33 is rotated around the horizontal α axis.
In the present embodiment, the rotation angle around the horizontal α-axis of the α-axis rotation housing 40 is limited to a range of 0 ° to 180 °.

<Description of movable electrode fixture>
The movable electrode fixture 37 is configured by incorporating the movable electrode support rod 42 into the α-axis rotating housing 40 described above.
In the movable electrode support rod 42, a holder 36 is screwed to the distal end portion thereof, and a retaining nut 43 is screwed to the proximal end portion thereof, and a shaft portion extending from the spring seat portion of the intermediate portion toward the proximal end side. A compression coil spring 44 is externally fitted.

<Description of support structure for movable electrode fixture>
The movable electrode support rod 42 is fitted into the α-axis rotation housing 40 with the compression coil spring 44 fitted on the outside.
A proximal end side of the compression coil spring 44 is in contact with the load cell 45, and a retainer 46 is pressed against the proximal end side of the load cell 45. The load cell 45 and the retainer 46 are fastened to the α-axis rotating housing 40 by bolts 91, so that the load cell 45 is fixed to the α-axis rotating housing 40.
The proximal end side of the movable electrode support rod 42 passes through the load cell 45 and the retainer 46 and protrudes from the retainer 46, and a retaining nut 43 is screwed to the protruded portion to be latched on the retainer 46. As a result, the movable electrode support rod 42 is prevented from coming out of the α-axis rotation housing 40.

<Description of electric wiring of movable electrode>
The movable electrode 33 is not shown through the holder 36, the movable electrode attachment 37, the welding gun body 32 a, the Z-axis slider 15, the Y-axis slider 14, the Y-axis beam member 12, the X-axis slider 11, and the X-axis beam member 9. It is connected to a positive pole of a power supply device (not shown) via a bus bar and a required cable (not shown).
In addition, although detailed description by illustration is abbreviate | omitted, in the electric current path from a power supply device to the movable electrode 33, it is between two members which move relatively, such as the X-axis beam member 9 and the X-axis slider 11, and other important points, for example. A breaker for mechanically connecting and disconnecting the current path is provided.

  Next, a control device for controlling the spot welder of this embodiment will be described below with reference to the functional block diagram of FIG.

As shown in FIG. 6, the control device 50 that controls the spot welder 1 includes a main CPU 51 and a servo CPU 52.
The main CPU 51 functions as an overall arithmetic processing unit of the control device 50, while the servo CPU 52 includes the index motor 4, the X-axis feed motor 20, the Y-axis feed motor 24, the Z-axis feed motor 29, It functions as an arithmetic processing unit for each servo motor of the θ-axis rotary motor 39 and the α-axis rotary motor 41.
These CPUs 51 and 52 are mutually connected to a welding current controller 54 including a welding condition calculation unit 55, a storage device 56, and an input device 57 via a system bus 53.

The main CPU 51 gives a position command signal and the like to the servo CPU 52.
The servo CPU 52 controls the servo motors 4, 20, 24, 29, 39, 41 via the servo amplifier 58 according to the position command signal and the like given from the main CPU 51.
A signal from an encoder 59 corresponding to the rotation amount of each servo motor 4, 20, 24, 29, 39, 41 is input to the servo CPU 52, and each servo motor 4, 20, 24, 29 is input to the servo amplifier 58. , 39, 41 is input with a signal from a current detector 60 that detects currents flowing through the terminals.

The welding current controller 54 controls the current supplied from the welding power supply device 61 to the movable electrode 33 of the welding gun 32.
The welding condition calculation unit 55 calculates welding conditions based on the welding data stored in the storage device 56.
The input device 57 is used for inputting various data, switching between a processing mode and a teaching mode, and the like.

In the spot welder 1 configured as described above, as shown in FIG. 7, the workpiece is controlled by 5-axis control of the horizontal X axis, horizontal Y axis, vertical Z axis, vertical θ axis, and horizontal α axis. 2 so that the movable electrode 33 is in vertical contact with the planned welding portion (where the fixed electrode 7 is disposed) in the horizontal surface portion, the inclined surface portion, and the vertical surface portion 2 regardless of the shape of the work 2. Can be positioned. Further, as shown in FIG. 8, the X-axis direction pressing force fx by the X-axis feeding mechanism 17, the Y-axis direction pressing force fy by the Y-axis feeding mechanism 21, and the Z-axis direction pressing force fz by the Z-axis feeding mechanism 25. Thus, a predetermined pressure F can be applied perpendicularly to the planned welding site from the movable electrode 33.
In this spot welder 1, after performing a teaching operation and a predetermined applied pressure-equivalent elastic displacement calculation operation, spot welding is performed on the workpiece 2 of a predetermined lot.
Hereinafter, a teaching operation, a predetermined applied pressure equivalent elastic displacement calculation operation, and a spot welding processing operation will be described in order.

<Description of teaching operation>
The teaching operation is an operation for an operator to input the position, posture, and movement of the movable electrode 33 to the control device 50 using the teaching pendant 62 (see FIG. 6), for example.

In FIG. 9A, the fixed electrode 7 is in contact with the back surface of the workpiece 2 to be welded.
By the operation of the teaching pendant 62 (see FIG. 6), the movable electrode 33 is paired with the fixed electrode 7 so as to sandwich the workpiece 2 and a standby state in which a predetermined gap d exists between the workpiece 2 and the surface. Move to position. By performing this operation for all the planned welding parts, the teaching operation is completed, and data relating to the movement of the movable electrode 33 at this time is stored in the storage device 56 as teaching data.

<Description of operation for calculating a predetermined applied pressure equivalent elastic displacement amount>
The predetermined displacement equivalent elastic displacement calculation operation is performed when the compression force applied from the fixed electrode 7 and the movable electrode 33 to the welding portion of the work 2 becomes the predetermined pressure F. Is calculated as the predetermined applied pressure equivalent elastic displacement amount S. This predetermined applied pressure equivalent elastic displacement amount calculation operation will be described with reference to FIGS.

First, as a first-stage operation, the movable electrode 33 is brought into contact with the planned welding portion of the work 2 in a vertical direction by operating the teaching pendant 62 (see FIG. 6) from the state shown in FIG. 9A. The movable electrode 33 is moved so that the electrode contact position as shown in FIG.
Next, as a second stage operation, the X-axis feed mechanism is configured so as to press the movable electrode 33 vertically against the planned welding portion of the workpiece 2 by operating the teaching pendant 62 from the state shown in FIG. 9B. 17, The feed operation of the Y-axis feed mechanism 21 and the Z-axis feed mechanism 25 is performed. At this time, the load signal from the load cell 45 is fed back in real time, and the value of the actual pressure obtained by the processing calculation based on the load signal has reached a predetermined pressure F as shown in FIG. At this time, the feed operations of the X-axis feed mechanism 17, the Y-axis feed mechanism 21, and the Z-axis feed mechanism 25 are stopped.
Along with the pressing operation of the movable electrode 33, the compression coil spring 44 is compressed by a predetermined amount, and the elastic displacement amount at this time is calculated as the elastic displacement amount S corresponding to the predetermined pressure force. By performing this operation for all the planned welding sites, the predetermined displacement-corresponding elastic displacement calculation operation is completed, and the calculated predetermined displacement-corresponding elastic displacement amount S is stored in the storage device 56.
The predetermined applied pressure equivalent elastic displacement amount calculation operation may be performed together with the teaching operation or may be performed independently of the teaching operation.

<Description of spot welding processing operation>
After performing the above-described teaching operation and the predetermined applied pressure equivalent elastic displacement calculation operation, the actual spot welding operation is performed. This spot welding process operation is demonstrated using FIG. 6 and FIG. 9 (a)-(c).

When actually performing spot welding, the main CPU 51 outputs a position command signal for positioning the movable electrode 33 at the standby position shown in FIG. 9A to the servo CPU 52.
The servo CPU 52 performs position feedback control based on the position command signal from the main CPU 51 and the signal from the encoder 59, and outputs a current command signal (torque command signal) to the servo amplifier 58. The servo amplifier 58 performs feedback control of current based on the current command signal and the signal from the current detector 60, supplies drive current to the servo motors 20, 24, 29, 39, 41, and servo motors. 20, 24, 29, 39 and 41 are driven and controlled.

  Next, the main CPU 51 servos a position command signal for causing the compression coil spring 44 to generate a predetermined applied pressure equivalent elastic displacement amount S as shown in FIG. 9C through the electrode contact position shown in FIG. It gives to CPU52. As a result, the servomotors 20, 24, and 29 are driven and controlled, and a predetermined pressure F is applied from the fixed electrode 7 and the movable electrode 33 to the planned welding portion of the workpiece 2.

  In this embodiment, an allowable range ± f is set before and after the predetermined pressure F as a reference, and the value of the pressure detected by the load cell 45 is outside the range of (F−f) to (F + f). When the main CPU 51 determines that the value is equal to the value, an operation stop signal is transmitted from the main CPU 51 to the servo CPU 52, the welding current controller 54, and the like, whereby the operation of the spot welder 1 is stopped.

<Description of effects>
According to the spot welder of the present embodiment, the X-axis feed mechanism 17, the Y-axis feed mechanism 21, and the Z-axis are set so that the elastic displacement amount of the compression coil spring 44 is equal to the elastic displacement amount S corresponding to the predetermined applied force. Since the predetermined pressing force F is applied to the workpiece 2 by controlling the feed mechanism 25, the actual pressing force (for example, motor current value) actually applied to the workpiece 2 is fed back in real time to correct the pressing force. Therefore, the time required to apply the predetermined pressurizing force F to the workpiece 2 can be shortened as compared with the conventional one, whereby the welding cycle time can be shortened.

Furthermore, according to the spot welder 1 of this embodiment, the following effects can be obtained.
(1) The X-axis feed mechanism 17, the Y-axis feed mechanism 21, and the Z-axis feed mechanism 25 function as a pressurizing actuator for generating a pressurizing force on the planned welding site, and the second electrode is orthogonal to three axes. Since the device has a function as a moving mechanism for moving the device, the apparatus can be simplified and the weight around the electrode can be reduced as compared with the conventional device in which a pressurizing actuator is provided in the vicinity of the electrode. It is possible to increase the welding positioning speed.
(2) Since a total of five axes including a horizontal X axis, a horizontal Y axis, a vertical Z axis, a vertical θ axis, and a horizontal α axis are provided as control axes, a movable electrode can be applied to a planned welding portion regardless of the shape of the workpiece 2. The movable electrode 33 can be positioned so that the contact 33 forms a vertical contact, and good spot welding can be performed regardless of the shape of the workpiece 2.
(3) Production will be stopped even if the value of the actual pressure applied to the planned welding site deviates from the permissible range ± f of the predetermined pressure F, ensuring the manufacture of defective products. Can be avoided.
(4) A highly rigid support structure for supporting the welding gun 32 can be constructed by the X-axis beam member 9 supported by the column member 8 on the bed 3 and the Y-axis beam member 12 orthogonal thereto. Therefore, it is possible to increase the speed of the feed mechanisms 17, 21, and 25 and increase the combined pressure F by the feed mechanisms 17, 21, and 25. Therefore, it is possible to shorten the welding time, and even if the workpiece 2 is relatively thick (generally, a thick thickness requires a large pressing force) (for example, (Thickness: 1.2 to 4.5 mm), and good spot welding can be performed.

In the present embodiment, the fixed electrode 7 corresponds to the “first electrode” of the present invention, and the movable electrode 33 corresponds to the “second electrode” of the present invention.
The configuration including the X-axis feed mechanism 17, the Y-axis feed mechanism 21, and the Z-axis feed mechanism 25 corresponds to the “pressing force generation mechanism” of the present invention.
The compression coil spring 44 corresponds to the “elastic body” of the present invention.
The load cell 45 corresponds to the “pressing force detecting means” of the present invention.
The main CPU 51 corresponds to “predetermined applied pressure equivalent elastic displacement amount calculating means”, “applied pressure suitability determining means” and “operation stop means” of the present invention.
The configuration including the main CPU 51 and the servo CPU 52 corresponds to the “pressing force generation mechanism control means” of the present invention.

[Second Embodiment]
FIG. 10 is an explanatory view of a spot welder according to the second embodiment of the present invention, and shows a standby position state diagram (a) and an enlarged view (b) of the E part of (a).
In the first embodiment, a spot welding machine 1 that sandwiches and pressurizes a workpiece 2 between a fixed electrode 7 fixed at a predetermined position and a movable electrode 33 that is movable with respect to the fixed electrode 7 by 5-axis control to perform spot welding. However, the present embodiment is an example in which the present invention is applied to a spot welding machine 1 </ b> A having a configuration in which a polar coordinate robot 70 includes a welding gun 71.
In the present embodiment, the same or similar parts as those in the first embodiment will be denoted by the same reference numerals in the drawing, and detailed description thereof will be omitted. Hereinafter, the first embodiment and the first embodiment will be omitted. The explanation will focus on the differences.

<Description of welding gun>
As shown in FIG. 10A, the welding gun 71 includes a welding gun main body frame 74 that is fixed to a distal end portion of an arm 72 in the polar coordinate robot 70 via an attachment bracket 73.
The welding gun body frame 74 has an electric cylinder mounting portion 74a at its base and a gun arm mounting portion 74b at its tip.
An electric cylinder 77 (corresponding to the “pressing force generation mechanism” of the present invention) in which the rod 76 is pushed out and retracted using the servo motor 75 as a drive source is connected to the electric cylinder mounting portion 74 a via a pivot shaft 78. And can be swung. A first gun arm 79 is fixed to the gun arm attachment portion 74b.
A gun arm support member 81 is rotatably attached to the intermediate portion of the welding gun body frame 74 via a support shaft 80. A second gun arm 82 is fixed to the tip of the gun arm support member 81.

<Description of first electrode and second electrode>
The first gun arm 79 and the second gun arm 82 are bent so that the tip portions of the first gun arm 79 and the second gun arm 82 face each other. A second electrode 84 is attached to the distal end of the gun arm 82, and the first electrode 83 and the second electrode 84 are disposed to face each other.

<Description of connecting rod>
A connecting rod 85 is disposed between the electric cylinder 77 and the gun arm support member 81.
The connecting rod 85 includes a housing 86 coupled to the rod 76 of the electric cylinder 77, and a push-pull rod 87 is incorporated into the housing 86.
In the push-pull rod 87, the distal end portion is connected to the intermediate portion of the gun arm support member 81 via the connecting pin 88, and the retaining nut 43 is screwed to the proximal end portion, from the spring seat portion in the intermediate portion. A compression coil spring 44 is fitted on the shaft toward the proximal end.

The push-pull rod 87 is fitted in the housing 86 in a state where the compression coil spring 44 is fitted.
A proximal end side of the compression coil spring 44 is in contact with the load cell 45, and a retainer 46 is pressed against the proximal end side of the load cell 45. The load cell 45 and the retainer 46 are fastened to the housing 86 by bolts 91, whereby the load cell 45 is fixed to the housing 86.
The proximal end side of the push-pull rod 87 passes through the load cell 45 and the retainer 46 and protrudes from the retainer 46, and a retaining nut 43 is screwed to the protruded portion to be hooked on the retainer 46. Thus, the push-pull rod 87 is prevented from coming out of the housing 86.

When the connecting rod 85 is retracted by the contraction operation of the electric cylinder 77, the gun arm support member 81 is rotated toward the base side of the welding gun body frame 74 with the support shaft 80 as a fulcrum. The second gun arm 82 is moved away from the first gun arm 79, and the relative distance between the first electrode 83 and the second electrode 84 is increased.
On the contrary, when the connecting rod 85 is pushed out by the extension operation of the electric cylinder 77, the gun arm support member 81 is rotated toward the tip end side of the welding gun body frame 74 with the support shaft 80 as a fulcrum. Accordingly, the second gun arm 82 is moved so as to approach the first gun arm 79, and the relative distance between the first electrode 83 and the second electrode 84 is reduced.

  Next, a control device for controlling the spot welder of this embodiment will be described below with reference to the functional block diagram of FIG.

As shown in FIG. 6, in the control device 50 </ b> A that controls the spot welding machine 1 </ b> A, the main CPU 51 functions as an overall arithmetic processing device of the control device 50 </ b> A, while the servo CPU 52 is an electric cylinder 77. It specially works as an arithmetic processing unit for the servo motor 75 that drives the servo motor 89 and the servo motor 89 of the polar coordinate robot 70 drive system.
The main CPU 51 gives a position command signal to the servo CPU 52, and the servo CPU 52 controls the servo motors 75 and 89 via the servo amplifier 58 according to the position command signal given from the main CPU 51.
A signal from the encoder 90 corresponding to the rotation amount of the servo motors 75 and 89 is input to the servo CPU 52, and a signal from the current detector 60 corresponding to the current flowing through the servo motors 75 and 89 is input to the servo amplifier 58. Entered.

In the spot welder 1A configured as described above, spot welding is performed on the workpiece 2 in a predetermined lot after performing the teaching operation and the elastic displacement amount calculation operation corresponding to the predetermined pressure force.
Hereinafter, a teaching operation, a predetermined applied pressure equivalent elastic displacement calculation operation, and a spot welding processing operation will be described in order.

<Description of teaching operation>
As shown in FIG. 10A, the teaching pendant 62 (see FIG. 6) in a state where the relative distance between the first electrode 83 and the second electrode 84 of the welding gun 71 is larger than the plate thickness of the workpiece 2. ) Is moved to a standby position where the first electrode 83 is in contact with the back surface of the planned welding portion of the workpiece 2. By performing this operation for all the planned welding parts, the teaching operation is completed, and data relating to the movement of the welding gun 71 at this time is stored in the storage device 56 as teaching data.

<Description of operation for calculating a predetermined applied pressure equivalent elastic displacement amount>
First, as a first-stage operation, the second electrode 84 comes into contact with the surface of the workpiece 2 to be welded by the operation of the teaching pendant 62 (see FIG. 6) from the state shown in FIG. The electric cylinder 77 is extended to reach the electrode contact position as shown in FIG.
Next, as an operation of the second stage, the electric cylinder 77 is moved so as to press the second electrode 84 against the planned welding portion of the workpiece 2 by operating the teaching pendant 62 from the state shown in FIG. The extension is activated. At this time, the load signal from the load cell 45 is fed back in real time, and the value of the actual pressure obtained by the processing calculation based on the load signal reaches a predetermined pressure F as shown in FIG. At this time, the extension operation of the electric cylinder 77 is stopped.
Along with the pressing operation of the second electrode 84, the compression coil spring 44 is compressed by a predetermined amount, and the elastic displacement amount at this time is calculated as a predetermined applied pressure equivalent elastic displacement amount S (see FIG. 12B). By performing this operation for all the planned welding sites, the predetermined displacement-corresponding elastic displacement calculation operation is completed, and the calculated predetermined displacement-corresponding elastic displacement amount S is stored in the storage device 56.
The predetermined applied pressure equivalent elastic displacement amount calculation operation may be performed together with the teaching operation or may be performed independently of the teaching operation.

<Description of spot welding processing operation>
After performing the above-described teaching operation and the predetermined applied pressure equivalent elastic displacement calculation operation, the actual spot welding operation is performed.
This spot welding processing operation will be described with reference to FIGS. 6 and 10 to 12.
When actually performing spot welding, the main CPU 51 outputs a position command signal for positioning the welding gun 71 at the standby position shown in FIG.
The servo CPU 52 performs position feedback control based on the position command signal from the main CPU 51 and the signal from the encoder 90, and outputs a current command signal (torque command signal) to the servo amplifier 58. The servo amplifier 58 performs current feedback control based on the current command signal and the signal from the current detector 60, supplies a drive current to the servo motors 75 and 89, and controls the servo motors 75 and 89. To do.

Next, the main CPU 51 causes the compression coil spring 44 to generate an elastic displacement amount S corresponding to a predetermined pressure as shown in FIGS. 12A and 12B through the electrode contact position shown in FIG. A command signal is given to the servo CPU 52.
Accordingly, the servo motor 75 is driven and controlled, and a predetermined pressure F is applied from the first electrode 83 and the second electrode 84 to the planned welding portion of the workpiece 2.

  Also in the present embodiment, the allowable range ± f is set before and after the predetermined pressure F as a reference, and the value of the pressure detected by the load cell 45 is in the range of (F−f) to (F + f). When the main CPU 51 determines that the value is outside, an operation stop signal is transmitted from the main CPU 51 to the servo CPU 52, the welding current controller 54, and the like, thereby stopping the operation of the spot welding machine 1A.

<Description of effects>
According to the spot welding machine of the present embodiment, the servo motor 75 is controlled so that the elastic displacement amount of the compression coil spring 44 is equal to the elastic displacement amount S corresponding to the predetermined applied force calculated in advance. Since it is applied to the workpiece 2, as in the first embodiment, there is no need to correct the applied pressure by feeding back the actual applied pressure (for example, motor current value) actually applied to the workpiece 2 in real time. Accordingly, the time until the predetermined pressure F is applied to the workpiece 2 can be shortened as compared with the conventional one, whereby the welding cycle time can be shortened.

  As mentioned above, although the spot welder of the present invention has been described based on a plurality of embodiments, the present invention is not limited to the configuration described in the above embodiments, and the configuration is appropriately set within the scope not departing from the gist thereof. It can be changed.

  Since the spot welder of the present invention has a characteristic that it can shorten the time until a predetermined pressure is applied to the member to be welded, it can be used for shortening the cycle time of spot welding. It can be used suitably.

DESCRIPTION OF SYMBOLS 1,1A Spot welding machine 2 Work piece 2a, 2b Welded member 7 Fixed electrode (1st electrode)
17 X-axis feed mechanism (pressing force generation mechanism)
21 Y-axis feed mechanism (pressing force generation mechanism)
25 Z-axis feed mechanism (pressing force generation mechanism)
33 Movable electrode (second electrode)
34 θ-axis rotation mechanism 35 α-axis rotation mechanism 44, compression coil spring (elastic body)
45, load cell (pressure detection means)
50, 50A control device 51, main CPU (predetermined applied pressure equivalent elastic displacement calculation means, pressing force generation mechanism control means)
52, Servo CPU (Pressure generation mechanism control means)
77 Electric cylinder (pressing force generation mechanism)
83 1st electrode 84 2nd electrode

Claims (3)

In a spot welding machine that sandwiches and pressurizes at least two or more members to be welded between a first electrode and a second electrode that can move relative to the first electrode to perform spot welding,
A pressing force generation mechanism that generates a pressing force to be pressed by the second electrode against a portion of the welded member that is scheduled to be spot welded;
An elastic body provided between the pressing force generation mechanism and the second electrode and elastically displaced according to the pressing force from the pressing force generation mechanism;
The pressing force applied from the first electrode and the second electrode to the planned welding site by transmitting the pressing force from the pressing force generating mechanism to the second electrode through the elastic body. A predetermined applied pressure equivalent elastic displacement amount calculating means for calculating an elastic displacement amount of the elastic body at a predetermined applied force as a predetermined applied force equivalent elastic displacement amount;
A pressing force generation mechanism control means for controlling the pressing force generation mechanism so that an elastic displacement amount of the elastic body becomes a predetermined pressing force equivalent elastic displacement amount calculated by the predetermined pressing force equivalent elastic displacement amount calculation means;
A spot welder comprising: The pressing force generation mechanism includes an X-axis feed mechanism that linearly moves the second electrode along the horizontal X-axis direction, and a horizontal Y-axis direction that is orthogonal to the horizontal X-axis direction. A Y-axis feed mechanism that linearly moves, and a Z-axis feed mechanism that linearly moves the second electrode along the vertical Z-axis direction perpendicular to the horizontal X-axis direction and the horizontal Y-axis direction,
2. The spot welder according to claim 1, wherein a θ-axis rotation mechanism that rotates the second electrode around a vertical θ-axis and an α-axis rotation mechanism that rotates the second electrode around a horizontal α-axis are provided. A pressure detection means for detecting an actual pressure applied from the first electrode and the second electrode to the welding planned site, and a value of the pressure detected by the pressure detection means is a predetermined value. A pressure appropriateness determining unit that determines whether or not the pressure is within a preset allowable range, and the spot welder when the pressure is determined to be inappropriate by the pressure appropriateness determining unit. The spot welding machine according to claim 1, further comprising operation stop means for stopping the operation of the spot welder.

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