Welding device

Abstract

To form a cooling passage that allows a cooling medium to properly flow to each electrode.SOLUTION: An indirect spot-welding device 1 includes a first welding electrode 12, a second welding electrode 13, and a cooling passage 14 for allowing a coolant to flow therethrough. The cooling passage 14 includes a single flow passage that passes through the first welding electrode 12 and the second welding electrode 13.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a welding device. [Background technology]

[0002] For example, in the welding process for automobiles, spot welding is performed by passing an electric current through the parts to be welded while they are pressed together.When an electric current is passed through a welding electrode, it generates heat due to its own resistivity, heat due to the resistance of the current path due to the small contact area with the part, and heat conduction due to resistance heating from the joint between the parts, resulting in high temperatures.Therefore, welding equipment has traditionally been configured to cool the electrode by providing a cooling path inside the conductive path to the electrode and sending a cooling medium (cooling water) through it.

[0003] For example, the spot welder described in Patent Document 1 includes an upper electrode and a lower electrode for clamping and applying pressure to a base material and a workpiece to be welded, and for passing an electric current through them. Also, separate cooling water flow paths are provided for cooling each electrode. These cooling water flow paths branch off upstream, flow toward the respective electrodes, and then merge again downstream. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-230967 Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of a configuration in which the cooling path is branched to flow to each electrode as in Patent Document 1, the flow path resistance is not constant in each branched flow path, and the cooling medium does not flow evenly.

[0006] An object of the present invention is to form cooling paths that allow a cooling medium to flow appropriately through each electrode. [Means for solving the problem]

[0007] In order to solve the above problem, the present invention provides a welding device having a plurality of electrodes and a cooling path through which a cooling medium flows, characterized in that the cooling path has a single flow path passing through the plurality of electrodes.

[0008] According to the welding device of the present invention, a single cooling path passes through multiple electrodes without forming branch paths for the cooling medium to flow to each electrode. This prevents the cooling medium from not flowing through one cooling path, and allows the cooling medium to pass through each electrode appropriately. Furthermore, since only one flow meter can detect whether the cooling medium is flowing to each electrode, the cost of the welding device can be reduced compared to a configuration in which a cooling path branches for each electrode and a flow meter is provided for each.

[0009] The welding device of the present invention can also be configured to have a holding portion that holds the electrode, and as the electrodes, a first welding electrode that extends to one side of the holding portion and sandwiches the holding portion therebetween, and a second welding electrode that extends to the other side opposite the one side. [Effects of the Invention]

[0010] According to the present invention, a cooling passage that allows a cooling medium to flow appropriately to each electrode can be formed. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a plan view of the welding equipment for the car body. [Figure 2] FIG. 1 is a side view of an indirect spot welding apparatus according to an embodiment of the present invention. [Figure 3] FIG. 2 is a side view of a welding gun. [Figure 4] FIG. 4 is a cross-sectional view showing a state in which welding is performed using a first welding electrode. [Figure 5] FIG. 4 is a cross-sectional view showing a state in which welding is performed using a second welding electrode. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] 1 is a plan view of welding equipment used in a welding process for an automobile body. In this welding process, multiple welding devices (five on each side in the illustrated example) are arranged on each side of the vehicle width direction of the vehicle body W. These welding devices are indirect spot welding devices 1, which are single-sided spot welding devices according to one embodiment of the present invention.

[0014] As shown in FIG. 2 , an indirect spot welding apparatus 1 (hereinafter simply referred to as “welding apparatus 1”) according to this embodiment includes a multi-axis robot arm 2, a welding gun 3 attached to the tip of the robot arm 2, and a ground electrode 21. The welding gun 3 includes a mounting unit 4 attached to the tip of the robot arm 2, a cylinder 5, an arm 6, and an electrode unit 7. In response to the movement of the robot arm 2, the welding gun 3 is moved to a specified joining point on the vehicle body W at any three-dimensional position and in any orientation within its movable range. The ground electrode 21 is fixed in contact with a predetermined position on the vehicle body W. The electrode unit 7 and the ground electrode 21 are electrically connected to a transformer 22, a control device 23, and a power source 24.

[0015] As shown enlarged in FIG. 3, the cylinder 5 is a means for pressing the electrode against the welding point and applying the pressure required for spot welding. The cylinder 5 includes a cylinder body 5a fixed to the mounting portion 4 and a rod 5b that is movable forward and backward relative to the cylinder body 5a. The rod 5b is capable of reciprocating along its own axis. An air cylinder, hydraulic cylinder, electric cylinder, or the like can be used as the cylinder 5; in this embodiment, an air cylinder is used. Hereinafter, the movement direction of the rod 5b (the up-down direction in FIG. 3) will be referred to as the "axial direction." In the description using FIG. 3, the side where the rod 5b protrudes from the cylinder body 5a in the axial direction (the lower side in FIG. 3) will be referred to as the lower side, and the opposite side (the upper side in FIG. 3) will be referred to as the upper side. However, this is not intended to limit the manner in which the welding gun 3 can be used.

[0016] An end of the rod 5b of the cylinder 5 is connected to the arm 6. In the illustrated example, the end of the rod 5b is connected to the arm 6 via a floating joint 9. The floating joint 9 transmits the axial force of the rod 5b to the arm 6 while allowing the rod 5b and the arm 6 to tilt relative to each other.

[0017] The welding gun 3 is provided with a guide mechanism 10 that guides the movement direction of the arm 6. In the illustrated example, guide mechanisms 10 are provided on both sides of the cylinder 5. Each guide mechanism 10 has a guide pin 10a fixed to the arm 6 and a guide member 10b fixed to the mounting part 4. The guide pin 10a is supported by the guide member 10b, and relative axial movement between the two is permitted, thereby guiding the arm 6 in the axial direction (up and down in the figure). The guide mechanism 10 can be, for example, a linear guide mechanism such as a ball spline.

[0018] Arm 6 is formed of a metal, such as an aluminum alloy, and is generally C-shaped in side view as shown in FIG. 3 because it must relay the current path wired in robot arm 2 to welding gun 3 and establish a conductive path that transmits electricity as compactly as possible to the electrode tip of welding gun 3. Specifically, arm 6 integrally includes a first portion 6a extending in a direction perpendicular to the axial direction, a second portion 6b extending downward from one end of first portion 6a, and a third portion 6c extending from the lower end of second portion 6b in a direction generally parallel to first portion 6a. The C-shape of arm 6 ensures a space inside arm 6 for placing a workpiece. However, the shape of arm 6 is not limited thereto, and it may be formed, for example, in an L-shape in side view.

[0019] An electrode portion 7 is fixed to the third portion 6c of the arm 6. The current flowing through the arm 6 is directly conducted to the electrode portion 7. The electrode portion 7 has a holding portion 11, a first welding electrode 12, and a second welding electrode 13. The first welding electrode 12 extends to one side of the holding portion 11, and the second welding electrode 13 extends to the other side. The holding portion 11 is a portion provided between both welding electrodes 12, 13. The holding portion 11, the first welding electrode 12, and the second welding electrode 13 are formed, for example, from a copper alloy (chromium copper).

[0020] Holding portion 11 is generally T-shaped and includes a horizontal portion 11a extending in a direction perpendicular to the axial direction, a first holding portion 11b extending from one end of horizontal portion 11a to one side in the axial direction, and a second holding portion 11c extending from one end of horizontal portion 11a to the other side in the axial direction. The other end of horizontal portion 11a is held by arm 6. First holding portion 11b holds one end of first welding electrode 12 at the end opposite second holding portion 11c. Second holding portion 11c holds one end of second welding electrode 13 at the end opposite first holding portion 11b.

[0021] The first welding electrode 12 extends upward in FIG. 3 relative to the holding portion 11, and its other end tip facing upward is the welding portion that applies pressure to the workpieces. The second welding electrode 13 extends downward in FIG. 3 relative to the holding portion 11, and its other end tip facing downward is the welding portion that applies pressure to the workpieces. In other words, the first welding electrode 12 extends upward in FIG. 3, and the second welding electrode 13 extends downward in FIG. 3, with the holding portion 11 sandwiched therebetween. In the illustrated example, the axes of the first welding electrode 12 and the second welding electrode 13 are parallel to the axial direction. Also, in the illustrated example, the first welding electrode 12 and the second welding electrode 13 are arranged coaxially. However, the shape of the holding portion 11 is not limited to this, and for example, the horizontal portion 11a may extend in a direction other than the direction shown in FIG. 3. Furthermore, the direction in which the first welding electrode 12 and the second welding electrode 13 extend is not limited to this, and the welding electrodes may not be arranged coaxially, or may be arranged in directions other than opposite directions (180 degrees apart).

[0022] The electrode part 7 also has a cooling water passage 14 inside thereof. Cooling water passes through the inside of the cooling water passage 14 as a cooling medium. Cooling water is an example of a fluid cooling medium. The cooling water passage 14 has a first flow path 14a and a fourth flow path 14d provided along the horizontal part 11a, a second flow path 14b that passes mainly inside the first welding electrode 12, and a third flow path 14c that passes mainly inside the second welding electrode 13.

[0023] The first flow path 14a constitutes the inlet portion of the cooling water passage 14 that passes inside the electrode portion 7. The cooling water in the cooling water passage 14 first flows from the first flow path 14a to the second flow path 14b as indicated by arrows A1, A2, and A3, to cool the first welding electrode 12 from its inside. Then, as indicated by arrows A4, A5, and A6, the cooling water flows from the second flow path 14b to the third flow path 14c to cool the second welding electrode 13 from its inside, and then flows from the fourth flow path 14d to the outside of the electrode portion 7. The fourth flow path 14d constitutes the outlet portion of the cooling water passage 14 that passes inside the electrode portion 7. The first flow path 14a, the second flow path 14b, the third flow path 14c, and the fourth flow path 14d are continuous, and the cooling water passage 14 formed by these is a single flow path. In other words, the cooling water passage 14 is a cooling path that passes through multiple welding electrodes without branching.

[0024] In this embodiment, cooling water passes through multiple welding electrodes 12, 13 through a single cooling water passage 14 to cool these welding electrodes. If the cooling passage were configured to branch off for each welding electrode, differences in flow path resistance would result in differences in the amount of cooling water flowing to each welding electrode, and one welding electrode may not be sufficiently cooled. With the configuration of this embodiment, the same amount of cooling water can flow through each welding electrode, ensuring sufficient cooling for each welding electrode.

[0025] The cooling water circulates through the cooling water passage 14, flowing from the upstream side of the first flow passage 14a to the downstream side of the fourth flow passage 14d, and then back to the cooling water passage 14. A flow meter 15 is provided downstream of the fourth flow passage 14d. Because a single cooling water passage 14 passes through multiple welding electrodes 12, 13, a single flow meter 15 for each cooling water passage 14 can be used to detect whether cooling water has properly passed through each welding electrode 12, 13. This reduces the cost of the welding equipment compared to a configuration in which a cooling passage and a separate flow meter are provided for each welding electrode. Furthermore, by measuring the flow rate of the cooling water passage 14 with the flow meter 15, if a blockage occurs somewhere in the passage, making it difficult to cool the electrode, or if the electrode becomes detached from its holder due to welding to the workpiece, the flow meter located downstream of the cooling passage can detect this abnormality and immediately shut down the welding equipment, preventing damage to the welding equipment and welding defects.

[0026] In this embodiment, during a series of welding steps, specifically during the step of moving arm 6 to the welding portion and the step of pressing first welding electrode 12 or second welding electrode 13 against the welding portion to weld, cooling water circulates through the above-described circulation path and passes through cooling water passage 14. By flowing cooling water even when not in actual welding operation, first welding electrode 12 and second welding electrode 13 can be sufficiently cooled.

[0027] In this embodiment, the first welding electrode 12 is shorter than the second welding electrode 13. In other words, the tip of the electrode (the welding portion) of the first welding electrode 12 is positioned farther from the holder 11 than the second welding electrode 13. The cooling water passage 14 passes through the first welding electrode 12 before the second welding electrode 13. In this way, the cooling water passage is also shorter for the short first welding electrode 12. Therefore, by passing through the first welding electrode 12 first, the cooling water can be sent to the second welding electrode 13 at a higher pressure. Therefore, each welding electrode 12, 13 can be sufficiently cooled. However, the cooling passage may be configured to pass through the longer welding electrode first.

[0028] Incidentally, the horizontal portion of the horizontal portion 11a between one end connected to the first holding portion 11b and the second holding portion 11c and the other end held by the arm 6 is a portion of the holding portion 11 with low rigidity and strength, and this portion is easily deflected when the first welding electrode 12 or the second welding electrode 13 applies pressure to the welded portion. Furthermore, to ensure flexibility in the shape of the area around the weld point on the vehicle body, the electrode portion 7 is required to have as simple and compact a shape as possible. Unlike the present embodiment, when a cooling water channel is provided for each of the welding electrodes 12 and 13, the number of cooling water channels passing through the horizontal portion 11a may be two sets of four. In this case, ensuring the strength of the horizontal portion 11a inevitably increases the size of the holding portion 11, which reduces the flexibility in the shape of the vehicle body W. In contrast, by providing a single cooling water channel 14 for the welding electrodes 12 and 13 as in the present embodiment, the number of cooling water channels passing through the horizontal portion 11a can be reduced to one set of two, ensuring the strength of the horizontal portion 11a and reducing the size of the holding portion 11.

[0029] Furthermore, in this embodiment, the first flow path 14a and the fourth flow path 14d, which are portions of the cooling water passage 14 that pass through the horizontal portion 11a, extend for the most part (for example, a portion that is more than half the length in the left-right direction in FIG. 3) or entirely in a direction parallel to the direction in which the horizontal portion 11a extends. This minimizes a decrease in the strength of the horizontal portion 11a that would be caused by forming the first flow path 14a and the fourth flow path 14d inside the horizontal portion 11a. However, the first flow path 14a and the fourth flow path 14d do not necessarily need to extend in a direction strictly parallel to the left-right direction in FIG. 3. Furthermore, the first flow path 14a and the fourth flow path 14d do not necessarily need to be configured to extend in the left-right direction in FIG. 3.

[0030] Furthermore, cooling water passage 14 is provided only in electrode portion 7, and not in arm 6. Arm 6 is the portion through which electricity flows when welding electrodes 12, 13 are energized, and in this embodiment is made of an aluminum alloy. A sufficient cross-sectional area is ensured for arm 6 to suppress heat generation in the passage, and by not flowing cooling water, metal corrosion due to the battery effect can be prevented. Cooling water passage 14 is formed by, for example, a tube connected to electrode portion 7 on the upstream side of first flow passage 14a and the downstream side of second flow passage 14b in FIG. 3, i.e., on the outside of electrode portion 7 of cooling water passage 14.

[0031] Next, a method for welding the intended joining portion of the vehicle body W from the interior side using the above welding device 1 will be described.

[0032] 4, a case where welding is performed using first welding electrode 12 will be described. First, a portion of welding gun 3 is inserted through opening W1 of vehicle body W, and first welding electrode 12 is disposed inside vehicle body W, and cylinder 5 is disposed outside vehicle body W. Then, portion P1 to be joined of vehicle body W is disposed on one axial side of first welding electrode 12 (the cylinder 5 side, right side in the figure), and the tip of first welding electrode 12 is positioned to face portion P1 to be joined of vehicle body W from the interior side.

[0033] Then, by driving rod 5b of cylinder 5 in the retracting direction and retracting first welding electrode 12 to one side in the axial direction (see the hollow arrow in FIG. 4), the tip of first welding electrode 12 presses portion to be joined P1 of the vehicle body W from the interior side to the exterior side (see the dotted line). The internal pressure of the cylinder is controlled so that the welding force required for welding and the resultant force of the component forces in the normal direction of portion to be joined P1 relative to the total weight of the movable members including arm 6, holding unit 11, and electrode unit 7 are balanced. As a result, a nugget is formed at portion to be joined P1, and the multiple metal plates are joined.

[0034] Next, a case where welding is performed using second welding electrode 13 will be described with reference to Figure 5. First, the portion to be joined P2 of the vehicle body W is placed on the other axial side of second welding electrode 13 (the opposite side from cylinder 5, the lower side in the figure), and the tip of second welding electrode 13 is positioned opposite to the portion to be joined P2 of the vehicle body W. Then, rod 5b of cylinder 5 is driven in the protruding direction to push second welding electrode 13 outward in the other axial direction (see the hollow arrow in Figure 5), thereby pressing the portion to be joined P2 of the vehicle body W with the tip of second welding electrode 13 (see the dotted line). The internal pressure of the cylinder is controlled so that the welding force required for welding and the resultant force of the component forces normal to portion to be joined P2 relative to the total weight of the movable members are balanced. In this state, current supplied from power source 24 shown in Fig. 2 is amplified by transformer 22 based on a command from control device 23 and supplied to second welding electrode 13, thereby causing current to flow through a path from second welding electrode 13, vehicle body W (part to be joined P2), and earth electrode 21. As a result, a nugget is formed at part to be joined P2, and the multiple metal plates are joined together.

[0035] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0036] Furthermore, the present invention is not limited to indirect spot welding devices, but can be applied to any one-side spot welding device that contacts welding electrodes with the portions to be joined of multiple metal sheets from only one side in the thickness direction. For example, the present invention can be applied to a series spot welding device that contacts a pair of first welding electrodes with multiple metal sheets from one side in the thickness direction. [Explanation of symbols]

[0037] 1 Indirect spot welding equipment (one-sided spot welding equipment) 2. Robotic Arm 3 welding guns 6 Arm 7 Electrode section 11 Holding part 12 First welding electrode 13 Second welding electrode 14 Cooling Channel (Cooling Channel) 15 Flow meter P1, P2 planned joining area W body

Claims

1. A welding device having a plurality of electrodes and a cooling passage through which a cooling medium flows, The welding device is characterized in that the cooling passage has a single flow path passing through multiple of the electrodes.

2. a holder for holding the electrode; 2. The welding device according to claim 1, wherein the electrodes include a first welding electrode extending to one side of the holding portion and a second welding electrode extending to the other side opposite the first side.

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