Electrode tip shaping device for resistance spot welding electrodes

Abstract

To provide an electrode tip shaping device capable of stabilizing shaping quality of an electrode tip.SOLUTION: A load current of an electric motor is monitored during shaping of a tip end of an electrode tip, in an electrode tip shaping device for shaping a tip end of an electrode tip according to plastic deformation. In the case that the load current attains a first load current or higher, a shaping pressurizing force is increased (steps ST1, ST2). Accordingly, shaping of a tip end of an electrode tip is satisfactorily performed. Further, if the load current of the electric motor increases additionally and attains a second load current or higher, a lubricant is supplied toward a gap between a tip end of an electrode tip and a processing surface of a shaping tool (steps ST3, ST4). Thus, frictional resistance between the tip end of the electrode tip and the processing surface of the shaping tool decreases, so that the load current is prevented from exceeding an allowable load current of the electric motor.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention Resistance spot welding electrode tips In particular, the present invention relates to an electrode tip shaping device. For resistance spot welding This relates to measures to stabilize the quality of electrode tip shaping. [Background technology]

[0002] Conventionally, resistance spot welding has been used as a means for joining multiple metal plates together. For resistance spot welding Electrode Tip (Hereinafter, it may be simply called the electrode tip.) Multiple metal plates (workpieces) are clamped together while an electric current is passed through them, and the Joule heat generated by the electrical resistance of the metal plates themselves is used to melt and join the metal plates.

[0003] The tip of the electrode tip (hereinafter, sometimes simply referred to as the electrode tip tip) wears and deforms as welding is repeated. If the tip surface of the electrode tip becomes larger due to the wear and deformation of the electrode tip tip, the welding current changes (for example, the current density decreases), and the welding quality deteriorates. For this reason, as disclosed in Patent Document 1, for example, an electrode tip shaping device is used to shape the electrode tip tip into a predetermined shape.

[0004] In the electrode tip shaping device disclosed in Patent Document 1, the electrode tip tip is fitted into a shaping tool, and the shaping tool is rotated around the axis of the electrode tip by an electric motor, and the electrode tip is pressed toward the shaping tool along the axial direction, thereby moving the electrode tip tip and the shaping tool relatively to shape the electrode tip tip. Patent Document 1 also discloses that the shaping rotation speed of the shaping tool is increased stepwise, and the pressure applied to the electrode tip is increased in synchronization with the increase in the shaping rotation speed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-223814 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when resistance spot welding (hereinafter sometimes simply referred to as spot welding) and shaping of the electrode tip end (hereinafter sometimes referred to as electrode tip shaping) are repeated, the contact state between the electrode tip end and the shaping tool changes. In other words, the excess material of the electrode tip end flows toward the side during shaping, increasing the contact area between the electrode tip and the shaping tool (for example, the side of the electrode tip also comes into contact with the shaping tool), which may cause poor shaping of the electrode tip or overload abnormality in the electric motor. For this reason, there is room for improvement in stabilizing the quality of electrode tip shaping.

[0007] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an electrode tip shaping device capable of stabilizing the shaping quality of an electrode tip. [Means for solving the problem]

[0008] The solution of the present invention to achieve the above object is as follows: For resistance spot welding A shaping tool for shaping the tip of the electrode tip, an electric motor for rotating the shaping tool, For resistance spot welding a pressure applying means for applying pressure to a tip of an electrode tip toward a processing surface of the shaping tool, For resistance spot welding The tip of the electrode tip is pressed against the processing surface of the shaping tool while the shaping tool is rotated. For resistance spot welding The tip of the electrode tip is plastically deformed to shape it. Resistance spot welding electrode tips The electrode tip shaping device is the premise. Resistance spot welding electrode tips The electrode tip shaping device For resistance spot welding The load current of the electric motor when shaping the tip of the electrode tip, or For resistance spot weldinga monitoring unit that monitors an integrated value of the amount of wear at the tip of the electrode tip as a parameter for changing a shaping operation; and a pressure setting unit that increases the pressure applied by the pressure means when the parameter monitored by the monitoring unit becomes equal to or greater than a predetermined value. For resistance spot welding The present invention is characterized by comprising a lubricant supplying means for supplying a lubricant between the tip of the electrode tip and the processing surface of the shaping tool.

[0009] Due to this specification, when the tip of the electrode tip is shaped after spot welding, the tip of the electrode tip is pressed toward the processing surface of the shaping tool and the shaping tool is rotated to plastically deform the tip of the electrode tip. When spot welding and shaping of the tip of the electrode tip are repeated, the contact state between the tip of the electrode tip and the shaping tool changes (for example, the side surface of the electrode tip also comes into contact with the shaping tool), and the load current of the electric motor increases when shaping the tip of the electrode tip. Or, the amount of wear of the tip of the electrode tip increases due to the repetition of spot welding and shaping of the tip of the electrode tip. The monitoring unit monitors parameters for changing the shaping operation, such as the load current of the electric motor or the integrated value of the amount of wear of the tip of the electrode tip, and when the parameter becomes equal to or greater than a predetermined value, the pressure setting unit increases the pressure applied by the pressure means. That is, the pressure applied to press the tip of the electrode tip toward the processing surface of the shaping tool is increased. This allows the tip of the electrode tip to be in reliable contact with the machining surface of the shaping tool, resulting in good shaping (the tip of the electrode tip is properly shaped to fit the machining surface of the shaping tool). In addition, when the pressure is increased in this way, the load current may further increase, possibly exceeding the allowable load current of the electric motor, but the lubricant supply means supplies lubricant between the tip of the electrode tip and the machining surface of the shaping tool, thereby reducing the frictional resistance between them and preventing the load current from exceeding the allowable load current. Effect of the Invention

[0010] In the present invention, for an electrode tip shaping device that shapes an electrode tip by applying pressure to the machining surface of a rotating shaping tool, parameters for changing the shaping operation, such as the load current of an electric motor or the integrated value of the wear amount of the electrode tip, are monitored, and when the parameter becomes equal to or exceeds a predetermined value, the pressure force for pressing the electrode tip toward the machining surface of the shaping tool is increased. Also, a lubricant is supplied between the electrode tip and the machining surface of the shaping tool. This allows the electrode tip to be shaped well, and the shaping quality of the electrode tip can be stabilized. Also, it is possible to prevent the load current of the electric motor from exceeding the allowable load current. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a welding gun of a resistance spot welding device according to an embodiment. FIG. [Diagram 2] FIG. 2 is a block diagram showing a schematic configuration of a control device. [Diagram 3] FIG. 2 is a perspective view of the electrode tip of the upper electrode as viewed from below. [Figure 4] FIG. 2 is a side view of the electrode tip of the upper electrode. [Diagram 5] 1A and 1B are schematic diagrams for explaining the configuration of an electrode tip shaping device according to an embodiment and an electrode tip shaping operation. [Figure 6] FIG. 2 is a perspective view showing the periphery of an upper working surface of a shaping tool. [Figure 7] FIG. 13 is a diagram showing a state in which each electrode tip is pressed against each machining surface of the shaping tool. [Figure 8] 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. [Figure 9] 8 is a cross-sectional view taken along line IX-IX in FIG. 7. [Figure 10] 11A and 11B are cross-sectional views for explaining changes in the tip of the electrode tip due to spot welding and shaping operations. [Figure 11] FIG. 11 is a flow chart showing the procedure of an electrode tip shaping operation. [Figure 12]11A and 11B are diagrams showing changes in the load current and shaping pressure of an electric motor and the timing of supplying lubricant when shaping of an electrode tip is repeated. [Figure 13] FIG. 13 is a diagram showing the transition of the amount of change in the surface condition of the tip of the electrode tip when the shaping of the electrode tip is repeated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a case where the present invention is applied as an electrode tip shaping device for shaping an electrode tip used in a resistance spot welding device that performs resistance spot welding (hereinafter, sometimes simply referred to as welding) between multiple iron or aluminum alloy plate materials will be described. In this embodiment, a case where the "parameter for changing the shaping operation" in the present invention is the load current of an electric motor will be described.

[0013] - Configuration of resistance spot welding equipment - Before describing the electrode tip shaping device, the configuration of the resistance spot welding device will be described.

[0014] Fig. 1 is a schematic diagram showing the configuration of a welding gun G of a resistance spot welding device according to this embodiment. Fig. 2 is a block diagram showing the schematic configuration of a control device 10 used for controlling the welding gun G and for a shaping operation (shaping control) of an electrode tip, which will be described later.

[0015] The welding gun G is configured with the following main components: a gun body 1 held by a robot arm RA, an upper electrode 2, a lower electrode 3 erected on a lower portion 1a of the gun body 1, an electrically-operated upper electrode lifting device (hereinafter simply referred to as an electrode lifting device) 4 for holding and lifting the upper electrode 2, an electrode position detection device 5, and a current adjustment device 6 for adjusting a welding current value (hereinafter also simply referred to as a current value) flowing between the upper electrode 2 and the lower electrode 3. The electrodes 2, 3 are provided at their tips with electrode tips 21, 31 (hereinafter, the electrode tip 21 of the upper electrode 2 may be referred to as the upper electrode tip 21, and the electrode tip 31 of the lower electrode 3 may be referred to as the lower electrode tip 31) shaped by an electrode tip shaping device 100 (see FIG. 5) described later. In FIG. 1, W1 and W2 are metal plates (iron plates or aluminum alloy plates).

[0016] 1, the gun body 1 is a roughly U-shaped member, and a lower electrode 3 is detachably provided on the upper surface of the lower part 1a. An electrode lifting device 4 is attached to the tip of the upper part 1b of the gun body 1.

[0017] The electrode lifting device 4 includes a servo electric motor 41 attached to the tip of the upper part 1b of the gun body 1, and a lifting member 42 coupled to a drive shaft (not shown) of the servo electric motor 41, and the upper electrode 2 is detachably attached to a lower end portion 42a of the lifting member 42. The electrode lifting device 4 corresponds to the pressurizing means in the present invention.

[0018] The electrode position detection device 5 is constituted by, for example, an encoder, and is attached to the upper end portion 41a of the servo electric motor 41. The detection value is then transmitted to the control device 10.

[0019] The current adjusting device 6 adjusts the value of the current flowing between the upper electrode 2 and the lower electrode 3 in response to a current command value transmitted from the control device 10. As the current adjusting device 6, for example, a well-known device including a variable resistor or a converter is used.

[0020] The control device 10 controls the welding gun G and the welding robot (not shown) (controls the rotation angle of each joint of the robot arm RA, etc.), and includes a processor such as a CPU (Central Processing Unit), a ROM (Read-Only Memory) for storing a control program, a RAM (Random-Access Memory) for temporarily storing data, and an input / output port. As shown in Fig. 2, the control device 10 includes an input unit 11, an electrode position calculation unit 12, a current value calculation unit 13, a pressure setting unit 14, a robot arm control unit 15, and an output unit 16 as functional units realized by the control program. The control device 10 also includes a monitoring unit 17 as a functional unit that operates during the shaping operation of each electrode tip 21, 31.

[0021] The input unit 11 acquires information from the input device 7 that inputs the thickness of the metal plate materials W1, W2, etc. The electrode position calculation unit 12 calculates the electrode position based on the detection value of the electrode position detection device 5. The current value calculation unit 13 calculates the current value when current is applied between the upper electrode 2 and the lower electrode 3. The pressure setting unit 14 sets the pressure required for welding (pressure applied to the metal plate materials W1, W2 by the upper electrode 2 and the lower electrode 3). The pressure setting unit 14 also sets the pressure of each electrode tip 21, 31 against a shaping tool 110 (see FIG. 5) when shaping each electrode tip 21, 31, which will be described later. The robot arm control unit 15 controls the rotation angle of each joint of the robot arm RA, and stores information on the position and posture of the welding gun G during spot welding and the position and posture of the welding gun G during shaping each electrode tip 21, 31 by teaching in advance, and controls the robot arm RA according to the information. The output unit 16 outputs information on the current value calculated by the current value calculation unit 13, information on the pressing force set by the pressing force setting unit 14, and instruction information such as the rotation angle of each joint of the robot arm RA from the robot arm control unit 15. The RAM also temporarily stores information such as the detection value from the electrode position detection device 5 and the plate thickness. Note that other configurations of the control device 10 are similar to those used for conventional welding guns G, and therefore detailed description thereof will be omitted. Among the functional units in the control device 10, a functional unit (monitoring unit 17) related to the shaping operation of each electrode tip 21, 31 will be described later.

[0022] Fig. 3 is a perspective view of the upper electrode tip 21 of the upper electrode 2 as viewed from below. The upper electrode tip 21 is made of a copper alloy such as Cu-Cr or Cu-Cr-Zr, or a copper material in which a hard material such as Al2O3 is dispersed. As shown in Fig. 3, the upper electrode tip 21 is a member having a substantially cylindrical shape, and the shape of the tip (the surface of the tip) for clamping the metal plate materials W1, W2 is a circular flat surface (or a curved surface with a slightly convex shape) having a predetermined radius. The lower electrode tip 31 of the lower electrode 3 has a similar structure.

[0023] Fig. 4 is a side view of the upper electrode tip 21. The dimension φa in Fig. 4 is the diameter dimension of the tip surface of the upper electrode tip 21, and in order to obtain good welding quality, it is necessary that the dimension (diameter dimension) φa of this tip surface be obtained stably. Similarly, the diameter dimension of the tip surface of the lower electrode tip 31 must also be obtained stably. The diameter dimension of the tip surface of each electrode tip 21, 31 is set in advance according to the target nugget diameter during welding. The shaping of the tip of each electrode tip 21, 31 to stably obtain the diameter dimension of the tip surface is performed by a shaping operation by an electrode tip shaping device 100 described later.

[0024] Conventionally, when the tip surface of the electrode tip becomes larger due to wear or deformation of the electrode tip as welding is repeated, the welding current changes (for example, the current density decreases) and the welding quality decreases, so a shaping operation is performed by an electrode tip shaping device to shape the electrode tip into a predetermined shape. However, when spot welding and shaping of the electrode tip are repeated, the contact state between the electrode tip tip and the shaping tool changes. For example, the excess material of the electrode tip tip flows toward the side during shaping, increasing the contact area between the electrode tip and the shaping tool (for example, the side of the electrode tip also comes into contact with the shaping tool), which may cause poor shaping of the electrode tip (for example, poor shaping due to insufficient contact between the electrode tip tip and the shaping tool), and may cause an overload abnormality in the electric motor that rotates the shaping tool. In particular, when the contact between the electrode tip tip and the shaping tool is insufficient, a circular depression (also called a damage diameter) may occur in the center of the electrode tip tip. When such a dent occurs, as the diameter of the dent increases, the amount of heat generated during spot welding becomes insufficient, which causes defective welding.

[0025] In view of this, the present embodiment provides an electrode tip shaping device 100 that can stabilize the shaping quality of an electrode tip.

[0026] -Electrode tip shaping device- Next, the electrode tip shaping device 100 will be described with reference to FIG.

[0027] The electrode tip shaping device 100 includes a shaping head 101 , an electric motor 102 , a frame 103 , and a guide rail 104 .

[0028] The shaping head 101 is equipped with a shaping tool 110. The shaping tool 110 will be described in detail later. The shaping head 101 is supported by a guide rail 104 so as to be movable in the vertical direction in FIG. 1. The shaping tool 110 is rotatably attached to the tip of the shaping head 101.

[0029] The electric motor 102 is configured to rotate the shaping tool 110 attached to the tip of the shaping head 101. For example, the rotation of the output shaft of the electric motor 102 is transmitted to the shaping tool 110 by a plurality of gears (not shown) so that the shaping tool 110 rotates around a vertical axis. The frame 103 includes plates 103a and 103b facing each other in the vertical direction. The guide rail 104 is provided between the facing plates 103a and 103b. The shaping head 101 is supported between the plates 103a and 103b so as to be movable up and down by receiving a biasing force from a compression coil spring 105 attached to the guide rail 104. The support structure of the shaping head 101 in the electrode tip shaping device 100 is not limited to the above-mentioned one.

[0030] Here, a description will be given of the shaping tool 110. As described above, the shaping tool 110 is rotatably attached to the tip of the shaping head 101, and receives the driving force of the electric motor 102 to rotate about a vertical axis.

[0031] Fig. 6 is a perspective view showing the periphery of the upper processing surface 111a of the shaping tool 110. Fig. 7 is a view showing a state in which the electrode tips 21 and 31 are pressed against the processing surfaces 111a and 111b of the shaping tool 110.

[0032] As shown in these figures, the shaping tool 110 includes a main body 111 extending in the horizontal direction, upper extensions 112, 112 extending upward from both ends of the main body 111 in the extending direction (horizontal direction), and lower extensions 113, 113 extending downward from both ends of the main body 111 in the extending direction. The inner surfaces of the upper extensions 112, 112 are inclined surfaces that slope outward as they extend upward. Similarly, the inner surfaces of the lower extensions 113, 113 are inclined surfaces that slope outward as they extend downward. The inclination angles of these inclined surfaces are approximately equal to the inclination angles of the side surfaces near the tips of the electrode tips 21, 31. The main body 111 and each upper extension portion 112, 112 form a recess (a recess open to the upward direction) into which the upper electrode tip 21 is inserted, and the main body 111 and each lower extension portion 113, 113 form a recess (a recess open to the downward direction) into which the lower electrode tip 31 is inserted.

[0033] The upper surface of the main body 111 is an upper processed surface 111a for shaping the tip of the upper electrode tip 21, and is machined into a predetermined shape designed in advance (a predetermined shaping shape defined for the tip of the upper electrode tip 21). Similarly, the lower surface of the main body 111 is a lower processed surface 111b for shaping the tip of the lower electrode tip 31, and is machined into a predetermined shape designed in advance (a predetermined shaping shape defined for the tip of the lower electrode tip 31).

[0034] As shown in Fig. 5, the electrode tip shaping device 100 according to this embodiment is provided with a lubricant supply device (lubricant supply means) 120 that supplies a lubricant (lubricant oil) between the tips of the electrode tips 21, 31 and the processing surfaces 111a, 111b of the shaping tool 110. The lubricant supply device 120 includes a tank (not shown) that stores the lubricant and a lubricant supply pipe 121 connected to the tank. Fig. 5 shows only the lubricant supply pipe 121 that supplies the lubricant between the tip of the upper electrode tip 21 and the upper processing surface 111a of the shaping tool 110, but the lubricant supply device 120 according to this embodiment may include a lubricant supply pipe that supplies the lubricant between the tip of the lower electrode tip 31 and the lower processing surface 111b of the shaping tool 110.

[0035] The tank is provided with an on-off valve (not shown) for switching between supplying and not supplying lubricant to the lubricant supply pipe 121. That is, when the on-off valve is in a closed state, lubricant is not supplied to the lubricant supply pipe 121, and when the on-off valve is in an open state, lubricant is supplied to the lubricant supply pipe 121. The configuration of the lubricant supply device 120 is not limited to the one described above.

[0036] As shown in FIG. 2, the control device 10 is electrically connected to the electric motor 102 and the lubricant supply device 120. The control device 10 includes a monitoring unit 17 in addition to the input unit 11, electrode position calculation unit 12, current value calculation unit 13, pressure setting unit 14, robot arm control unit 15, and output unit 16 described above. This monitoring unit 17 monitors the load current of the electric motor 102 when shaping the tip of each electrode tip 21, 31. As a specific method for monitoring this load current, it is calculated by a known method based on a current value measured by an ammeter provided in the electric circuit of the electric motor 102. This load current of the electric motor 102 is an example of the "parameter for changing the shaping operation" referred to in the present invention.

[0037] When the load current of the electric motor 102 monitored by the monitoring unit 17 becomes equal to or greater than a preset first load current, a command to increase the pressure is output from the monitoring unit 17, and the command to increase the pressure is output from the output unit 16 to the electrode lifting device 4. This increases the pressure with which the tips of the electrode tips 21, 31 are pressed against the processing surfaces 111a, 111b of the shaping tool 110.

[0038] The first load current is determined in advance by experiment or simulation as a value for detecting an increase in the contact area between the tip of each electrode tip 21, 31 and each machining surface 111a, 111b of the shaping tool 110 (an increase in the tip area of ​​each electrode tip 21, 31). Also, the amount of increase in the pressing force is determined in advance by experiment or simulation as an amount of increase in the pressing force that allows the tip of each electrode tip 21, 31 to be reliably brought into contact with each machining surface 111a, 111b of the shaping tool 110.

[0039] Furthermore, when the load current of the electric motor 102 being monitored by the monitoring unit 17 increases and becomes equal to or greater than a preset second load current, the monitoring unit 17 opens the on-off valve of the lubricant supplying device 120 to supply lubricant between the tips of the electrode tips 21, 31 and the machining surfaces 111a, 111b of the shaping tool 110. This reduces the frictional resistance between the tips of the electrode tips 21, 31 and the machining surfaces 111a, 111b of the shaping tool 110. The second load current is a value higher than the first load current and less than the allowable load current of the electric motor 102, and is determined in advance by experiments or simulations.

[0040] - Electrode tip shaping operation - Next, a description will be given of the shaping operation of each electrode tip 21, 31 by the electrode tip shaping device 100 configured as described above. This shaping operation of the electrode tips 21, 31 is performed every time a predetermined number of spot welding operations are completed, and is performed to ensure welding quality by shaping, through plastic deformation, the tip of the electrode tip 21, 31 that is worn, deformed, has weld material (iron, zinc, etc.) attached, etc.

[0041] 7, when shaping the tips of the electrode tips 21 and 31, the tip of the upper electrode tip 21 is abutted against the upper machining surface 111a of the shaping tool 110, the tip of the lower electrode tip 31 is abutted against the lower machining surface 111b of the shaping tool 110, and the shaping tool 110 rotates around the vertical axis under the driving force of the electric motor 102 while the main body 111 of the shaping tool 110 is clamped from above and below with a predetermined pressure (initialized pressure). For example, the tips of the electrode tips 21 and 31 are abutted against the machining surfaces 111a and 111b of the rotating shaping tool 110 and pressed with a predetermined pressure.

[0042] Fig. 8 is a cross-sectional view taken along line VIII-VIII in Fig. 7. Fig. 9 is a cross-sectional view taken along line IX-IX in Fig. 7. The arrow in Fig. 9 indicates the rotation direction of the shaping tool 110. By this shaping operation, the tip of the upper electrode tip 21 and the upper processing surface 111a of the shaping tool 110 are moved relative to each other, and the tip of the lower electrode tip 31 and the lower processing surface 111b of the shaping tool 110 are moved relative to each other, so that the tips of the electrode tips 21, 31 are shaped into shapes (shaping shapes) corresponding to the shapes of the processing surfaces 111a, 111b, respectively.

[0043] Fig. 10 is a cross-sectional view for explaining the change in the electrode tip tip due to spot welding and shaping operations in this embodiment. Fig. 10(a) is a cross-sectional view of the tip of the electrode tip 21 when a predetermined number of spot weldings have been performed (when shaping operations are not performed). In Fig. 10(a), an alloy layer La and an adhesion layer Lb of the welded material are formed at the tip of the electrode tip (e.g., the upper electrode tip) 21. The alloy layer La is, for example, a layer made of an alloy of copper and zinc. The adhesion layer Lb is, for example, a layer made of iron or zinc.

[0044] If further spot welding is performed from this state, as shown in FIG. 10(b), this may result in deformation or deterioration of the tip of the electrode tip 21 (deformation of the adhesion layer Lb in FIG. 10(b)), potentially resulting in a deterioration in the welding quality.

[0045] Then, when the electrode tip shaping device 100 performs a shaping operation on the electrode tip 21 from this state, the tip of the electrode tip 21 is plastically deformed (plastically deformed along the upper processing surface 111a of the shaping tool 110) as shown in Fig. 10(c), so that the tip of the electrode tip 21 is shaped into a predetermined shape, and a tip shape of the electrode tip 21 that improves welding quality can be obtained. In the case shown in Fig. 10(c), shaping is performed in which the adhesion layer Lb is deformed by a dimension (amount of change) A1.

[0046] In this embodiment, the pressure applied to the tips of the electrode tips 21, 31 toward the machining surfaces 111a, 111b of the shaping tool 110 is changed and the lubricant supply device 120 is operated according to the load current of the electric motor 102 monitored by the monitoring unit 17 as described above. Fig. 11 is a flowchart showing the procedure of these operations. The operations shown in this flowchart are performed every time the electrode tip shaping device 100 performs a shaping operation of the electrode tips 21, 31.

[0047] First, in step ST1, it is determined whether or not the load current of the electric motor 102 monitored by the monitoring unit 17 has become equal to or greater than the first load current. If the load current of the electric motor 102 has not reached the first load current and the determination is NO in step ST1, the pressing force is not changed and the process returns.

[0048] On the other hand, when the load current of the electric motor 102 becomes equal to or greater than the first load current and YES is determined in step ST1, the process proceeds to step ST2, where the pressing force of the electrode tips 21, 31 is increased. Specifically, a pressing force increase command is output from the monitoring unit 17, and the pressing force increase command is output from the output unit 16 to the electrode lifting device 4. This increases the pressing force with which the tips of the electrode tips 21, 31 are pressed against the machining surfaces 111a, 111b of the shaping tool 110, making it possible to reliably bring the tips of the electrode tips 21, 31 into contact with the machining surfaces 111a, 111b of the shaping tool 110.

[0049] Then, the process proceeds to step ST3, where it is determined whether or not the load current of the electric motor 102 monitored by the monitoring unit 17 has become equal to or greater than the second load current. If the load current of the electric motor 102 has not reached the second load current and the determination is NO in step ST3, the process returns without supplying the lubricating oil (lubricant).

[0050] On the other hand, when the load current of the electric motor 102 becomes equal to or greater than the second load current and YES is determined in step ST3, the process proceeds to step ST4, where the supply of lubricant by the lubricant supplying device 120 is started. Specifically, a valve open command is output from the monitoring unit 17, and the valve open command is output from the output unit 16 to the lubricant supplying device 120. As a result, the opening / closing valve of the lubricant supplying device 120 is opened, and the lubricant is supplied toward between the tips of the electrode tips 21, 31 and the machining surfaces 111a, 111b of the shaping tool 110, thereby reducing the frictional resistance between the tips of the electrode tips 21, 31 and the machining surfaces 111a, 111b of the shaping tool 110.

[0051] This operation is repeated every time the electrode tips 21, 31 are shaped.

[0052] Fig. 12 is a diagram showing the transition of the load current and the pressing force (shaping pressing force) of the electric motor 102 and the timing of supplying the lubricant when the shaping of the electrode tips 21, 31 is repeated. The horizontal axis in Fig. 12 is the number of shaping operations (shaping number of times), and the vertical axis is the load current and the shaping pressing force of the electric motor 102. In Fig. 12, when the number of shaping operations reaches Na, the load current of the electric motor 102 becomes equal to or greater than the first load current, and control for increasing the shaping pressing force is started. When the number of shaping operations reaches Nb, the load current of the electric motor 102 becomes equal to or greater than the second load current, and supply of the lubricant between the tips of the electrode tips 21, 31 and the processing surfaces 111a, 111b of the shaping tool 110 is started.

[0053] FIG. 13 is a diagram showing the transition of the amount of change in the surface state of the tip of the electrode tip 21, 31 (for example, the amount of expansion of the tip area of ​​the electrode tip 21, 31) when spot welding and the shaping operation of the electrode tip 21, 31 are repeated, where the horizontal axis is the number of weldings and the vertical axis is the amount of change in the surface state. The dashed line in FIG. 13 indicates a value at which the amount of change in the surface state of the electrode tip 21, 31 becomes large enough to deteriorate the welding quality. In this embodiment, the shaping operation of the electrode tip 21, 31 is performed at a point before the amount of change in the surface state of the electrode tip 21, 31 reaches the dashed line (the amount of change at which the welding quality deteriorates) (the shaping operation is performed at each of the timings t1 to t5 in the figure), and the above-mentioned plastic deformation allows multiple shaping operations while keeping the amount of change in the surface state of the electrode tip 21, 31 (the amount of change associated with shaping, A2 in FIG. 13) small, which indicates that the electrode tip 21, 31 can be extended in life.

[0054] -Effects of the embodiment- As described above, the present embodiment can provide the following effects.

[0055] First, in this embodiment, the load current of the electric motor 102 is monitored, and when the load current becomes equal to or greater than a predetermined value (the first load current), the pressure force for pressing the tip of each electrode tip 21, 31 toward each processing surface 111a, 111b of the shaping tool 110 is increased. This makes it possible to reliably bring the tip of each electrode tip 21, 31 into contact with each processing surface 111a, 111b of the shaping tool 110, suppress the occurrence of the above-mentioned depression (damage diameter), and perform good shaping of the electrode tips 21, 31.

[0056] Furthermore, when the load current of the electric motor 102 increases and exceeds a predetermined value (the second load current), the lubricant supply device 120 supplies lubricant between the tip of the electrode tip 21, 31 and the processing surface 111a, 111b of the shaping tool 110. This reduces the frictional resistance between the tip of the electrode tip 21, 31 and the processing surface 111a, 111b of the shaping tool 110, and prevents the load current from exceeding the allowable load current. In addition, this supply of lubricant can prevent foreign matter (so-called shaping debris) from adhering to each processing surface 111a, 111b of the shaping tool 110, and can also prevent the tip of the electrode tip 21, 31 from being locally cut, thereby stabilizing the shaping quality of the electrode tip 21, 31.

[0057] Furthermore, in this embodiment, the tip of each electrode tip 21, 31 is plastically deformed (plastically deformed to conform to each machining surface 111a, 111b of the shaping tool 110) so that the tip of each electrode tip 21, 31 is shaped into a predetermined shape. Therefore, compared to cutting the electrode tip tip with a general dresser (cutting blade), the dimension by which the length of the electrode tip 21, 31 is shortened can be reduced, and the life of the electrode tip 21, 31 can be extended.

[0058] -Other embodiments- The present invention is not limited to the above-described embodiment, and all modifications and applications encompassed within the scope of the claims and equivalents thereto are possible.

[0059] For example, in the above embodiment, the case where the "parameter for changing the shaping operation" in the present invention is the load current of the electric motor 102 has been described. The present invention is not limited to this, and the integrated value of the wear amount of the tip of the electrode tip 21, 31 (integrated value of the wear amount from the initial state of the electrode tip 21, 31) may be the parameter for changing the shaping operation. In other words, when the integrated value of the wear amount of the tip of the electrode tip 21, 31 reaches a predetermined first wear amount, the pressure force for pressing the tip of the electrode tip 21, 31 toward the processing surface 111a, 111b of the shaping tool 110 is increased, and further, when the wear of the tip of the electrode tip 21, 31 progresses and the integrated value of the wear amount reaches a predetermined second wear amount, the opening and closing valve of the lubricant supply device 120 is opened to supply lubricant toward between the tip of the electrode tip 21, 31 and the processing surface 111a, 111b of the shaping tool 110. The integrated value of the amount of wear at the tip of the electrode tips 21, 31 is calculated based on the electrode position detected by the electrode position detector 5 (for example, the electrode position obtained from the stroke of the lifting member 42).

[0060] In the above embodiment, the timing of increasing the pressure for pressing the tips of the electrode tips 21, 31 toward the processing surfaces 111a, 111b of the shaping tool 110 and the timing of supplying the lubricant between the tips of the electrode tips 21, 31 and the processing surfaces 111a, 111b of the shaping tool 110 are different from each other. However, the present invention is not limited to this, and these timings may be made to coincide with each other.

[0061] In addition, in the electrode tip shaping device 100 in the above embodiment, the tip of each electrode tip 21, 31 is abutted against each machining surface 111a, 111b of the rotating shaping tool 110, but this is not limited to the above, and the start of rotation of the shaping tool 110 and the abutment of the tip of each electrode tip 21, 31 against each machining surface 111a, 111b may be performed at the same time.

[0062] In the above embodiment, the shaping of the tip of the upper electrode tip 21 and the shaping of the tip of the lower electrode tip 31 are performed simultaneously. However, the present invention is not limited to this, and the shaping of the tip of the upper electrode tip 21 and the shaping of the tip of the lower electrode tip 31 may be performed at different times. [Industrial Applicability]

[0063] The present invention relates to For resistance spot welding The quality of electrode tip shaping can be stabilized. Resistance spot welding electrode tips It is applicable to electrode tip shaping devices. [Explanation of symbols]

[0064] 4. Electrode lifting device (pressure means) 14 Pressure setting section 17 Monitoring Department 21 Upper electrode tip 31 Lower electrode tip 100 Electrode tip shaping device 102 Electric motor 110 Shaping tools 111a Upper machined surface 111b Lower machined surface 120 Lubricant supply device (lubricant supply means)

Claims

[Claim 1] An electrode tip shaping device for a resistance spot welding electrode tip, comprising a shaping tool for shaping a tip of an electrode tip for resistance spot welding, an electric motor for rotating the shaping tool, and a pressure means for applying pressure to the tip of the electrode tip for resistance spot welding against a machining surface of the shaping tool, wherein the tip of the electrode tip for resistance spot welding is pressed against the machining surface of the shaping tool while rotating the shaping tool, thereby plastically deforming and shaping the tip of the electrode tip for resistance spot welding, a monitoring unit that monitors a load current of the electric motor during shaping of the tip of the resistance spot welding electrode tip or an integrated value of an amount of wear of the tip of the resistance spot welding electrode tip as a parameter for changing a shaping operation; a pressure setting unit that increases the pressure applied by the pressurizing means when the parameter monitored by the monitoring unit becomes equal to or greater than a predetermined value; a lubricant supplying means for supplying a lubricant to a gap between the tip of the electrode tip for resistance spot welding and the machining surface of the shaping tool.

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