Friction stir welding apparatus

Abstract

To provide a friction stir welding apparatus which can simplify a device configuration, and can reduce each workload of an assembly work and a maintenance work.SOLUTION: A friction stir welding apparatus 100 includes a processing head 101 having a welding tool 103 to be pressed against stacked workpieces WK1 and WK2 in a rotationally driven state. A Z-axis driving motor 109 is connected to the processing head 101 through a ball screw mechanism 107, and the welding tool 103 is pressed against the workpieces WK1 and WK2. The Z-axis driving motor 109 is operated and controlled by a control device 130. When pressing the welding tool 103 against the workpieces WK1 and WK2, the control device 130 executes pressing force constant control of controlling operation of the Z-axis driving motor 109 so as to always press the welding tool 103 against the workpieces WK1 and WK2 at constant pressing force regardless of the change in the magnitude of reaction force.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a friction stir welding apparatus that presses a welding tool against stacked or butted workpieces while being rotationally driven, thereby welding stacked or butted workpieces by frictional heat. [Background technology]

[0002] Conventionally, there has been known a friction stir welding (FSW) apparatus that uses frictional heat to weld stacked or butted workpieces by pressing a welding tool against the stacked or butted workpieces while rotating and driving the tool. For example, the following Patent Document 1 discloses a friction stir welding apparatus in which a load cell is provided in a ball screw mechanism that displaces a spindle unit that holds the friction stir welding tool in the vertical direction, thereby controlling the pressing load with which the friction stir welding tool presses the workpieces. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6372615

[0004] However, in the friction stir welding apparatus shown in Patent Document 1, the load cell is disposed between the nut in the ball screw mechanism and the mounting member extending from the moving table that supports the spindle unit, resulting in a complex apparatus configuration, and therefore problems with assembly and maintenance work being cumbersome and resulting in a heavy workload.

[0005] The present invention has been made to address the above-mentioned problems, and its object is to provide a friction stir welding apparatus that can simplify the apparatus configuration and reduce the workload of each assembly and maintenance task. Summary of the Invention

[0006] In order to achieve the above-mentioned object, the present invention is characterized in that in a friction stir welding apparatus for joining stacked or butted workpieces, the apparatus comprises a processing head having a joining tool that is pressed against stacked or butted workpieces while being rotationally driven, Z-axis displacement means having a prime mover for reciprocatingly displacing the processing head in the Z-axis direction to approach or move away from the workpieces and for pressing the joining tool against the workpieces, and a control device for controlling the operation of the prime mover, the Z-axis displacement means comprises a ball screw that is rotationally driven by the prime mover, and a displacement body that is screwed into the ball screw and displaced in the axial direction by the rotational drive of the ball screw to reciprocately displace the processing head in the Z-axis direction, and the control device performs constant pressing force control for controlling the operation of the prime mover so that when the joining tool is pressed against the workpieces, the joining tool is always pressed against the workpieces with a constant pressing force regardless of changes in the magnitude of the reaction force from the workpieces.

[0007] According to the features of the present invention configured as described above, in the friction stir welding apparatus, the Z-axis displacement means for displacing the processing head in the Z-axis direction is configured by a so-called ball screw mechanism, and the control device executes constant pressing force control for controlling the operation of the prime mover so that the welding tool is always pressed against the workpiece with a constant pressing force regardless of changes in the magnitude of the reaction force from the workpiece. Therefore, in the friction stir welding apparatus, the ball screw mechanism operates in a forward or reverse manner in response to changes in the magnitude of the reaction force from the workpiece, causing the welding tool to approach or move away from the workpiece, so that the pressing force with which the welding tool presses the workpiece can be kept constant. In other words, the friction stir welding apparatus according to the present invention can keep the pressing force with which the welding tool presses the workpiece constant without using a load cell for detecting the pressing force with which the welding tool presses the workpiece, as in the above-mentioned conventional technology, and can simplify the apparatus configuration and reduce the workload of each of the assembly work and maintenance work.

[0008] Another feature of the present invention is that, in the friction stir welding apparatus, the Z-axis displacement means further includes a reaction force detector which detects the magnitude of a reaction force from the workpiece when the welding tool is pressed against the workpiece and outputs the reaction force to the control device, and when the welding tool is pressed against the workpiece, the control device selectively executes the constant pressing force control and a constant pressing force control which controls the operation of the prime mover so as to always press the welding tool against the workpiece with a constant pressing force based on a detection signal from the reaction force detector.

[0009] According to another feature of the present invention configured in this manner, the friction stir welding apparatus is provided with a reaction force detector that detects the magnitude of the reaction force from the workpiece when the welding tool is pressed against the workpiece. Therefore, constant pressing force control using a ball screw mechanism and constant pressing force control in which the operation of the prime mover is controlled based on the detection signal from the reaction force detector so that the welding tool is always pressed against the workpiece with a constant pressing force can be appropriately selected and executed according to the specifications of the welding process.

[0010] In order to achieve the above object, the present invention is characterized in that in a friction stir welding apparatus for joining stacked or butted workpieces, the apparatus comprises a processing head having a welding tool that is pressed against stacked or butted workpieces while being rotationally driven, a work table for supporting the workpieces, Z-axis displacement means having a prime mover for reciprocatingly displacing the processing head in the Z-axis direction to move the processing head closer to or away from the workpieces and pressing the welding tool against the workpieces, and a control device for controlling the operation of the prime mover, the Z-axis displacement means comprising a ball screw that is rotationally driven by the prime mover, and a screw threadedly fitted to the ball screw to which the processing head or the work table is connected. The apparatus is provided with a displacement body which is axially displaced by the rotational drive of the ball screw to reciprocate the machining head in the Z-axis direction, and a reaction force detector which detects the magnitude of the reaction force from the workpiece when the joining tool is pressed against the workpiece and outputs the detection signal to the control device. The reaction force detector is provided on a bolt which connects the machining head or the work table to the displacement body, and outputs a detection signal corresponding to the distortion of the bolt to the control device. The control device performs constant pressing force control which controls the operation of the prime mover so that the joining tool is always pressed against the workpiece with a constant pressing force based on the detection signal from the reaction force detector when the joining tool is pressed against the workpiece.

[0011] According to the features of the present invention configured in this manner, the friction stir welding apparatus has a reaction force detector that detects the magnitude of the reaction force from the workpiece when the welding tool is pressed against the workpiece, which is provided on the bolt connecting the machining head or the work table to the displacement body.This means that the reaction force detector can be installed or replaced without disassembling the ball screw mechanism, simplifying the apparatus configuration and reducing the burden of each assembly and maintenance work.

[0012] Another feature of the present invention is that in the friction stir welding apparatus, the reaction force detector is provided inside the bolt.

[0013] According to this, in the friction stir welding apparatus, since the reaction force detector is provided inside the bolt, it is possible to prevent the reaction force detector from being soiled or damaged.

[0014] Another feature of the present invention is that in the friction stir welding apparatus, the reaction force detector is disposed between the bolt and an object to be fastened to which the bolt is fastened.

[0015] According to this, since the friction stir welding apparatus has a reaction force detector positioned between the object to which the bolt is tightened and the reaction force detector, no processing or work is required to attach the reaction force detector to the bolt itself, and commercially available bolts can be used, thereby making it easier to obtain bolts.

[0016] Another feature of the present invention is that in the friction stir welding apparatus, a plurality of bolts are provided, and the reaction force detector is provided on at least two of the plurality of bolts.

[0017] According to this, the friction stir welding apparatus has reaction force detectors provided on at least two of the multiple bolts, thereby improving the reliability of detecting the magnitude of the reaction force from the workpiece. In this case, at least two reaction force detectors provided on at least two bolts can be provided in a state in which one is connected to the control device and the other reaction force detector is not connected to the control device as a spare. Also, the at least two reaction force detectors are each connected to the control device, and the control device can simultaneously or selectively use the at least two connected reaction force detectors to control the operation of the prime mover.

[0018] Another feature of the present invention is that the friction stir welding apparatus further comprises a Z-axis position detector which detects the position of the welding tool in the Z-axis direction and outputs the detected position to a control device, and when the control device detects that the position of the welding tool in the Z-axis direction has reached a predetermined limit position, it interrupts the constant pressure force control by the prime mover.

[0019] According to this, the friction stir welding apparatus is equipped with a Z-axis position detector which detects the position of the welding tool in the Z-axis direction. Therefore, when the position of the welding tool in the Z-axis direction reaches a predetermined limit position, the constant pressing force control by the prime mover is interrupted, thereby making it possible to prevent the continuation of abnormal processing and to prevent damage to the welding tool or workpiece. [Brief description of the drawings]

[0020] [Figure 1] 1 is a perspective view showing a schematic outline of an external configuration of a friction stir welding apparatus according to a first embodiment and a second embodiment of the present invention. [Diagram 2] 2 is a front view showing a state in which the processing head of the friction stir welding apparatus shown in FIG. 1 is lowered to perform welding. FIG. [Diagram 3] 3 is a side view of the linear guide on the left side viewed from the linear guide on the right side in FIG. 2 for explaining details of the ball screw mechanism on the back side of the processing head in the friction stir welding apparatus shown in FIG. 2. [Figure 4] 2 is a block diagram of a control system for controlling the operation of the friction stir welding apparatus shown in FIG. [Diagram 5] 10 is a side view of the linear guide on the left side viewed from the linear guide on the right side in FIG. 2 for illustrating details of a ball screw mechanism on the back side of the processing head in a friction stir welding apparatus according to a second embodiment of the present invention. FIG. [Figure 6] 3 is a side view of the linear guide on the left side viewed from the linear guide on the right side in FIG. 2 for explaining details of a ball screw mechanism on the back side of the processing head in a friction stir welding apparatus according to a modified example of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] First Embodiment Hereinafter, a first embodiment of the friction stir welding apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view that shows a schematic outline of the external configuration of the friction stir welding apparatus 100 according to the present invention. FIG. 2 is a front view that shows a state in which the processing head 101 in the friction stir welding apparatus 100 shown in FIG. 1 is lowered to perform welding processing. FIG. 3 is a side view of the linear guide 105a seen from the linear guide 105b side in order to explain the details of the ball screw mechanism 107 on the back of the processing head 101 in the friction stir welding apparatus 100 shown in FIG. 2. FIG. 4 is a block diagram of a control system for controlling the operation of the friction stir welding apparatus 100 shown in FIG. 1. Note that the figures referred to in this specification are schematic, such as exaggerated representations of some components, in order to facilitate understanding of the present invention. For this reason, the dimensions and ratios between the components may differ.

[0022] (Configuration of the friction stir welding apparatus 100) The friction stir welding apparatus 100 is a computer-controlled (NC-controlled) processing device that displaces a rotationally driven welding tool 103 while pressing it against one surface of metal workpieces WK1 and WK2 that are stacked or butted together, thereby joining the workpieces WK1 and WK2 to each other by plastic flow. The friction stir welding apparatus 100 is equipped with a processing head 101.

[0023] The processing head 101 has a function of gripping and rotating the joining tool 103, and mainly includes a spindle 101a, a spindle drive motor 101b, and a spindle housing 102. The spindle 101a is a part that detachably holds the joining tool 103 and rotates, and is made of a metal material formed into a round bar shape. That is, the spindle 101a is a so-called spindle. One end (not shown) of the spindle 101a (upper side in the figure) is connected to the spindle drive motor 101b, and the other end side is supported in the processing head 101 in a state where it hangs down downward in the figure. Here, the vertical direction in the figure in which the spindle 101a extends is the Z-axis direction.

[0024] The spindle drive motor 101b is an electric motor for driving the spindle 101a to rotate, and is attached on the spindle housing 102 of the processing head 101. The operation of this spindle drive motor 101b is controlled by a control device 130, which will be described later.

[0025] The spindle housing 102 is a metal part for supporting the spindle 101a and the spindle drive motor 101b, and is configured as a rectangular parallelepiped box extending in the Z-axis direction in the figure. In this case, the spindle housing 102 houses the spindle 101a with its lower end exposed, and supports the spindle drive motor 101b on its upper surface. In addition, the spindle housing 102 has an attachment part 102a formed on its back surface, which is the surface opposite to the front surface.

[0026] The mounting portion 102a is a portion to which a displacement body 107b (described later) is connected, and is formed in a plate shape that protrudes horizontally from the rear surface of the spindle housing 102. A slider that slides on a linear guide (described later) is attached to the rear surface of the spindle housing 102. This machining head 101 is held by a head base 104 via linear guides 105a and 105b.

[0027] The joining tool 103 is a tool for joining the workpieces WK1 and WK2. More specifically, the joining tool 103 is made of a material having excellent strength, impact resistance, and wear resistance, such as carbon steel, such as tool steel or tungsten steel, or alloy steel, formed into a cylindrical shape. One end (the upper side in the figure) of the joining tool 103 is held by the spindle 101a in a state where it hangs down from the spindle 101a. When the joining tool 103 is not held by the spindle 101a, it is held by a tool magazine 121, which will be described later, in a state where it hangs down.

[0028] The head base 104 is a component for reciprocatingly displacing the processing head 101 in the Z-axis direction and the X-axis direction. Specifically, the head base 104 is configured by forming a metal material into a plate shape extending in the Z-axis direction, and is supported by a column 110 via linear guides 111a and 111b. The head base 104 includes linear guides 105a and 105b, a Z-axis position detector 106, a ball screw mechanism 107, and a Z-axis drive motor 109.

[0029] The linear guides 105a and 105b are components for guiding the machining head 101 in the Z-axis direction, and are composed of two metal rods extending like rails. These linear guides 105a and 105b are attached to the head base 104, arranged parallel to each other in the Z-axis direction on both the left and right sides of the machining head 101 when viewed from the front. Sliders are fitted to the linear guides 105a and 105b, respectively, so as to be slidable in the Z-axis direction, and the machining head 101 is connected via these sliders.

[0030] The Z-axis position detector 106 is a measuring device that detects the position of the machining head 101 in the Z-axis direction and outputs a detection signal to the control device 130, and its operation is controlled by the control device 130. In this embodiment, the Z-axis position detector 106 is configured with a linear scale. This Z-axis position detector 106 is attached on the head base 104 along the linear guides 105a and 105b.

[0031] The ball screw mechanism 107 is a group of parts for guiding the machining head 101 in the Z-axis direction in cooperation with the linear guides 105a and 105b. Specifically, the ball screw mechanism 107 is mainly composed of a feed screw 107a and a displacement body 107b.

[0032] The feed screw 107a is a component for supporting the displacement body 107b and displacing it back and forth along the Z-axis direction, and is configured by forming a male screw on the outer surface of a metal rod. The feed screw 107a is disposed so as to extend in the Z-axis direction, with one end (upper side in the figure) connected to the Z-axis drive motor 109 and the other end (lower side in the figure) held slidably on the head base 104 via a bearing.

[0033] The displacement body 107b is a part that reciprocates along the axial direction of the feed screw 107a while connected to the machining head 101, and is composed of a metallic cylindrical body having a female thread that fits into the feed screw 107a with a small ball screw (not shown). The displacement body 107b is connected to the mounting part 102a provided on the back surface of the machining head 101 via bolts 108. Note that three of the four bolts 108 are shown in FIG. 3.

[0034] The Z-axis drive motor 109 is an electric motor for reciprocatingly displacing the machining head 101 in the Z-axis direction shown in the figure by rotating the ball screw mechanism 107, and its operation is controlled by the control device 130. Therefore, the machining head 101 is reciprocally displaced in the Z-axis direction shown in the figure along the ball screw mechanism 107 by the rotational driving of the Z-axis drive motor 109. In other words, the ball screw mechanism 107 and the Z-axis drive motor 109 correspond to the Z-axis displacement means according to the present invention. Furthermore, the Z-axis drive motor 109 corresponds to the prime mover according to the present invention.

[0035] The column 110 is a component for supporting the machining head 101. Specifically, the column 110 is formed in a gate shape in which both ends of a bridge portion 110a extending in the X-axis direction in the figure are supported by legs 110b each extending upright in the Z-axis direction in the figure, and is fixed in an upright position on a bed 115. The column 110 includes linear guides 111a, 111b, an X-axis position detector 112, a ball screw mechanism 113, and an X-axis drive motor 114 on the bridge portion 110a.

[0036] The linear guides 111a and 111b, like the linear guides 105a and 105b, are components for guiding the machining head 101 in the X-axis direction shown in the figure, and are composed of two metal rods extending in a rail-like shape. These linear guides 111a and 111b are attached to the mounting portion 110a, arranged parallel to each other in the X-axis direction shown in the figure, on both sides in the up-down direction when viewed from the front of the machining head 101. Sliders are fitted to these linear guides 111a and 111b in a state where they can slide freely in the X-axis direction shown in the figure, and the head base 104 is connected via each of these sliders.

[0037] The X-axis position detector 112 is a measuring device that detects the position of the machining head 101 in the X-axis direction shown in the figure and outputs a detection signal to the control device 130, and its operation is controlled by the control device 130. In this embodiment, the X-axis position detector 112 is configured with a linear scale. This X-axis position detector 112 is attached along the linear guides 111a and 111b on the installation part 110a.

[0038] The ball screw mechanism 113 is a group of parts for guiding the machining head 101 in the X-axis direction in cooperation with the linear guides 111a and 111b, similar to the ball screw mechanism 107. Specifically, the ball screw mechanism 113 is composed of a feed screw 113a and a displacement body 113b similar to the feed screw 107a and displacement body 107b constituting the ball screw mechanism 107.

[0039] In this case, the feed screw 113a is disposed so as to extend in the X-axis direction in the figure, with one end (the left side in the figure) connected to the X-axis drive motor 114 and the other end (the right side in the figure) slidably held on the bridge part 110a via a bearing. In addition, the displacement body 113b is connected to the back surface of the head base 104.

[0040] The X-axis drive motor 114 is an electric motor for rotating the ball screw mechanism 113 to reciprocate the machining head 101 in the X-axis direction, and its operation is controlled by the control device 130. Therefore, the machining head 101 is reciprocally displaced in the X-axis direction along the ball screw mechanism 113 by the X-axis drive motor 114 rotating.

[0041] Bed 115 is a component for supporting column 110, work table 120, and tool magazine 121 on the installation surface of friction stir welding apparatus 100, and is made of a casting formed in a rectangular shape in a plan view extending in the Y-axis direction perpendicular to the Z-axis direction and the Y-axis direction. A groove 115a is formed in the upper surface of bed 115, recessed along the Y-axis direction in the center of the Y-axis, and column 110 is provided straddling groove 115a, and linear guides 116a, 116b, Y-axis position detector 117, ball screw mechanism 118, and Y-axis drive motor 119 are provided in groove 115a.

[0042] The linear guides 116a and 116b, like the linear guides 105a and 105b, are components for guiding the work table 120 in the Y-axis direction, and are composed of two metal rods extending like rails. These linear guides 116a and 116b are attached in the groove 115a, arranged parallel to each other in the Y-axis direction on both the left and right sides of the machining head 101 when viewed from the front. Sliders are fitted to the linear guides 116a and 116b so as to be slidable in the Y-axis direction, and the work table 120 is connected via the sliders.

[0043] Y-axis position detector 117 is a measuring device that detects the position of work table 120 in the Y-axis direction in the drawing and outputs a detection signal to control device 130, and its operation is controlled by control device 130. In this embodiment, Y-axis position detector 117 is configured with a linear scale. This Y-axis position detector 117 is attached along linear guides 116a, 116b in groove portion 115a.

[0044] Similar to the ball screw mechanism 107, the ball screw mechanism 118 is a group of parts for guiding the work table 120 in the Y-axis direction in cooperation with the linear guides 116a and 116b. Specifically, the ball screw mechanism 118 is composed of a feed screw 118a and a displacement body (not shown) similar to the feed screw 107a and displacement body 107b constituting the ball screw mechanism 107.

[0045] In this case, feed screw 118a is disposed so as to extend in the Y-axis direction in the figure, with one end (the front side in the figure) connected to Y-axis drive motor 119 and the other end (the rear side in the figure) slidably held in groove 115a via a bearing. In addition, the displacement body is connected to the lower surface of work table 120.

[0046] The Y-axis drive motor 119 is an electric motor for rotating the ball screw mechanism 118 to reciprocately displace the work table 120 in the Y-axis direction in the figure, and its operation is controlled by the control device 130. Therefore, the work table 120 is reciprocally displaced in the Y-axis direction in the figure along the ball screw mechanism 118 by the rotational driving of the Y-axis drive motor 119.

[0047] The work table 120 is a component for supporting the workpieces WK1 and WK2, and is made of a metal material formed into a flat plate. On the upper surface of the work table 120, a clamp 120a is provided for detachably holding the workpieces WK1 and WK2.

[0048] The tool magazine 121 is a mechanical device that can detachably hold a plurality of welding tools 103 or cutting tools (such as end mills or milling cutters) and can transfer the welding tools 103 to the spindle 101a, and its operation is controlled by the control device 130. The tool magazine 121 is provided in an upright position adjacent to the column 110 on the bed 115. The tool magazine 121 is configured to move toward or away from the machining head 101 by the operation control of the control device 130.

[0049] The control device 130 is configured by a microcomputer including a CPU, ROM, RAM, etc., and comprehensively controls the overall operation of the friction stir welding apparatus 100, and performs welding processing on the workpieces WK1 and WK2 by executing a processing program (so-called NC (Numerical Control) program) (not shown) prepared by an operator. Specifically, the control device 130 controls the operation of the main shaft drive motor 101b, the Z-axis drive motor 109, the X-axis drive motor 114, the Y-axis drive motor 119, and the tool magazine 121 to relatively displace the welding tool 103 in three orthogonal axial directions consisting of the X-axis direction, the Y-axis direction, and the Z-axis direction while pressing the welding tool 103 against the workpieces WK1 and WK2, thereby performing welding processing on the workpieces WK1 and WK2.

[0050] This control device 130 is equipped with an operation panel 131 consisting of an input device made up of a group of switches that accept instructions from an operator and input them to the control device 130, and a liquid crystal display device that displays the operating status of the control device 130. The friction stir welding apparatus 100 also includes a power supply unit that supplies electricity for operating the spindle drive motor 101b, the Z-axis drive motor 109, the X-axis drive motor 114, the Y-axis drive motor 119, the tool magazine 121, and the control device 130, but descriptions of these configurations that are not directly related to the present invention will be omitted.

[0051] (Operation of the friction stir welding apparatus 100) Next, the operation of the friction stir welding apparatus 100 configured as described above will be described. First, an operator operates the operation panel 131 to turn on the power supply of the friction stir welding apparatus 100. As a result, the friction stir welding apparatus 100 executes a predetermined control program (not shown) prestored in a ROM in the control device 130, thereby positioning the processing head 101 and the work table 120 at their respective predetermined standby positions, and then goes into a standby state in which it waits for instructions from the operator. Here, the standby position is a position that does not physically interfere with the workpieces WK1, WK2 when the workpieces WK1, WK2 are attached to or detached from the work table 120.

[0052] Specifically, the control device 130 controls the operation of the Z-axis drive motor 109 to position the machining head 101 at the uppermost position (movement limit position), and also controls the operation of the X-axis drive motor 114 to position it at the movement limit position on the tool magazine 121 side. In addition, the control device 130 controls the operation of the Y-axis drive motor 119 to position the work table 120 at the movement limit position on the operator side (the Y-axis drive motor 119 side in this embodiment).

[0053] Next, the worker sets the workpieces WK1 and WK2 in the friction stir welding apparatus 100. Specifically, the worker fixes the workpieces WK1 and WK2, which are stacked together, onto the work table 120 via the clamp 120a. In this embodiment, the workpiece WK1 is set on the work table 120 in a state where it is stacked on the workpiece WK2.

[0054] Next, the operator operates the operation panel 131 to instruct the control device 130 to join the workpieces WK1, WK2. In response to this instruction, the control device 130 executes a control program for joining (not shown) to perform the joining process on the workpieces WK1, WK2. Note that in the following explanation of the operation, it is assumed that the spindle 101a holds the joining tool 103 required for joining the workpieces WK1, WK2.

[0055] First, the control device 130 controls the operation of the X-axis drive motor 114 and the Y-axis drive motor 119 to position the machining head 101 at a machining start position above the workpieces WK1, WK2, and then controls the operation of the spindle drive motor 101b to rotate the spindle 101a. Next, as shown in Fig. 2, the control device 130 controls the operation of the Z-axis drive motor 109 to lower the machining head 101 and press it against the workpieces WK1, WK2.

[0056] In this case, the control device 130 controls the operation of the Z-axis drive motor 109 so that the welding tool 103 always presses the workpieces WK1, WK2 with a constant pressing force. The pressing force with which the welding tool 103 presses the workpieces WK1, WK2 is experimentally obtained in advance according to the materials of the workpieces WK1, WK2 and the processing specifications such as the processing path, and is set in the control program.

[0057] Next, the control device 130 controls the operation of the X-axis drive motor 114 and the Y-axis drive motor 119 so that the machining head 101 is displaced in the X-axis direction and the Y-axis direction, respectively, along a joint line set (programmed) in advance by an operator. This allows the control device 130 to weld the workpieces WK1 and WK2 together along the joint line.

[0058] During such joining, the reaction force from the workpieces WK1, WK2 to the joining tool 103 changes due to defects that occur during the manufacture of the workpieces WK1, WK2 or when the workpieces WK1 and WK2 are superimposed on each other, specifically, warping, deformation, unevenness (variation) in plate thickness, surface roughness, etc. For this reason, the reaction force to the joining tool 103 becomes large when the surfaces of the workpieces WK1, WK2 are raised, and becomes small when the surfaces of the workpieces WK1, WK2 are recessed.

[0059] In such a case, the control device 130 controls the operation of the Z-axis drive motor 109 so that the welding tool 103 always presses the workpieces WK1, WK2 with a constant pressing force regardless of changes in the reaction force that the welding tool 103 receives from the workpieces WK1, WK2. On the other hand, the machining head 101 holding the welding tool 103 is supported by a ball screw mechanism 107.

[0060] Therefore, the machining head 101 is displaced in the illustrated Z-axis direction by the ball screw mechanism 107 performing forward or reverse operation depending on the magnitude of the reaction force from the workpieces WK1, WK2. Specifically, when the reaction force from the workpieces WK1, WK2 becomes smaller (decreased), the machining head 101 is displaced in one direction in the illustrated Z-axis direction (a direction approaching the workpieces WK1, WK2) by the ball screw mechanism 107 performing forward operation depending on the magnitude of the reaction force. Here, forward operation means that the displacement body 107b is linearly displaced in the illustrated Z-axis direction by the rotational drive of the feed screw 107a.

[0061] On the other hand, when the reaction force from the workpieces WK1, WK2 becomes large (increases), the processing head 101 is displaced in the other direction in the illustrated Z-axis direction (direction moving away from the workpieces WK1, WK2) by the ball screw mechanism 107 performing a reverse operation according to the magnitude of the reaction force. Here, the reverse operation means that the feed screw 107a is rotated by the linear displacement of the displacement body 107b in the illustrated Z-axis direction. As a result, the friction stir welding apparatus 100 can perform welding processing by constant pressing force control in which the welding tool 103 is always pressed against the workpieces WK1, WK2 with a constant pressing force regardless of changes in the reaction force that the welding tool 103 receives from the workpieces WK1, WK2. Note that here, the "constant pressing force" naturally includes not only a pressing force of one magnitude but a pressing force within a certain range.

[0062] During this welding process, the control device 130 constantly monitors the position of the welding tool 103 in the Z-axis direction using a detection signal input from the Z-axis position detector 106, and immediately interrupts the welding process when the position of the welding tool 103 reaches a lower limit position or an upper limit position preset in the control device 130. Specifically, the control device 130 separates the welding tool 103 from the workpieces WK1, WK2. This enables the control device 130 to prevent abnormal processing from continuing and to prevent damage to the welding tool 103 or the workpieces WK1, WK2.

[0063] The control device 130 does not control the welding tool 103 to change the pressing force against the workpieces WK1, WK2 when the position of the welding tool 103 in the illustrated Z-axis direction is within a range from the lower limit position to the upper limit position, for example, not less than the lower limit position and not more than the upper limit position. Therefore, as described above, the processing head 101 is displaced in the illustrated Z-axis direction by the ball screw mechanism 107 performing forward or reverse operation depending on the magnitude of the reaction force from the workpieces WK1, WK2. As a result, the friction stir welding apparatus 100 can perform welding processing by constant pressing force control in which the welding tool 103 is always pressed against the workpieces WK1, WK2 with a constant pressing force regardless of changes in the reaction force that the welding tool 103 receives from the workpieces WK1, WK2.

[0064] Next, when the machining head 101 is located at the end position of the joining line, the control device 130 controls the operation of the Z-axis drive motor 109 to displace the machining head 101 upward in the figure so as to move it away from the workpieces WK1 and WK2. Then, the control device 130 controls the operation of the spindle drive motor 101b to stop the rotational drive of the spindle 101a, and then controls the operation of each of the X-axis drive motor 114, the Y-axis drive motor 119, and the Z-axis drive motor 109 to return the machining head 101 and the work table 120 to their respective standby positions. Therefore, the operator can remove the joined workpieces WK1 and WK2 from the work table 120 by releasing the gripping state of the clamp 120a on the work table 120.

[0065] As can be understood from the above description of the operation, according to the first embodiment, the friction stir welding apparatus 100 causes the ball screw mechanism 107 to operate in a forward or reverse direction in response to a change in the magnitude of the reaction force from the workpieces WK1, WK2, thereby moving the welding tool 103 toward or away from the workpieces WK1, WK2, and therefore the pressing force with which the welding tool 103 presses the workpieces WK1, WK2 can be kept constant. That is, the friction stir welding apparatus 100 according to the present invention can keep the pressing force with which the welding tool 103 presses the workpieces WK1, WK2 constant without using a load cell for detecting the pressing force with which the welding tool 103 presses the workpieces WK1, WK2, as in the above conventional technology, and can simplify the apparatus configuration and reduce the workload of each of the assembly and maintenance operations.

[0066] <Second embodiment> Next, a friction stir welding apparatus 200 according to a second embodiment of the present invention will be described with reference to Figures 1, 2, 4 and 5. The friction stir welding apparatus 200 according to the second embodiment differs from the friction stir welding apparatus 100 in the first embodiment in that it is provided with a reaction force detector 210. Therefore, in the second embodiment, the description will be centered on the parts that are different from the first embodiment, and the description of the parts that are common to both embodiments and the corresponding parts will be omitted as appropriate.

[0067] (Configuration of the friction stir welding apparatus 200) The reaction force detector 210 is a component for detecting the magnitude of the reaction force from the workpieces WK1, WK2 when the welding tool 103 is pressed against the workpieces WK1, WK2 to perform welding. Specifically, the reaction force detector 210 is configured such that a piezoelectric effect element or a piezoresistive effect element that exerts a piezoelectric effect or a piezoresistive effect is attached to the inside or the outer surface of a bolt 211 serving as a fastener, and is configured to output a detection signal consisting of an electric signal corresponding to the deformation (strain) of the bolt 211. In the second embodiment, the reaction force detector 210 is provided inside the bolt 211.

[0068] This reaction force detector 210 is disposed by replacing one of the four bolts 108 that connect the displaceable body 107b to the mounting portion 102a of the machining head 101 in the first embodiment with a bolt 211. The reaction force detector 210 is electrically connected to the control device 130 so as to output a detection signal to the control device 130. The control device 130 controls the operation of the Z-axis drive motor 109 in response to the detection signal output from the reaction force detector 210. Note that two bolts 108 are shown in FIG. 6.

[0069] (Operation of the friction stir welding apparatus 200) An explanation will be given of the operation of the friction stir welding apparatus 200 configured as above. In the welding process in which the welding tool 103 is pressed against the workpieces WK1, WK2, the control device 130 performs constant pressing force control to keep the pressing force of the welding tool 103 pressing the workpieces WK1, WK2 constant by controlling the operation of the Z-axis drive motor 109 using a detection signal input from the reaction force detector 210.

[0070] First, when the welding tool 103 starts pressing the workpieces WK1, WK2, the control device 130 controls the operation of the Z-axis drive motor 109 so that the welding tool 103 presses the workpieces WK1, WK2 with a predetermined pressing force. As a result, a force corresponding to the pressing force with which the welding tool 103 presses the workpieces WK1, WK2 acts on the reaction force detector 210, and the reaction force detector 210 outputs a detection signal corresponding to this pressing force to the control device 130.

[0071] The control device 130 constantly monitors the reaction force that the welding tool 103 receives from the workpieces WK1, WK2, i.e., the pressing force with which the welding tool 103 presses the workpieces WK1, WK2, using the detection signal input from the reaction force detector 210, and controls the operation of the Z-axis drive motor 109. Specifically, when the reaction force that the welding tool 103 receives from the workpieces WK1, WK2 becomes smaller (decreased) than a predetermined lower limit value, the control device 130 controls the operation of the Z-axis drive motor 109 in accordance with the magnitude of the reaction force, thereby displacing the welding tool 103 in a direction closer to the workpieces WK1, WK2.

[0072] On the other hand, when the reaction force that the welding tool 103 receives from the workpieces WK1, WK2 becomes larger (increases) than a predetermined upper limit, the control device 130 controls the operation of the Z-axis drive motor 109 in accordance with the magnitude of the reaction force to displace the welding tool 103 in a direction away from the workpieces WK1, WK2. This enables the control device 130 to perform welding by constant pressing force control, in which the welding tool 103 is always pressed against the workpieces WK1, WK2 with a constant pressing force regardless of changes in the reaction force that the welding tool 103 receives from the workpieces WK1, WK2.

[0073] It should be noted that here, the "constant pressing force" naturally includes not only a pressing force of one magnitude but a pressing force within a certain range. In addition, the friction stir welding apparatus 200 includes the ball screw mechanism 107 in the first embodiment, but the control device 130 performs constant pressing force control using the reaction force detector 210 before the ball screw mechanism 107 operates in the forward or reverse direction.

[0074] As can be understood from the above operation description, according to the second embodiment, in the friction stir welding apparatus 200, a reaction force detector 210 that detects the magnitude of the reaction force from the workpieces WK1, WK2 when the welding tool 103 is pressed against the workpieces WK1, WK2 is provided on the bolt 211 that connects the machining head 101 to the displacement body 107b. Therefore, the reaction force detector 210 can be installed or replaced without disassembling the ball screw mechanism 107, thereby simplifying the device configuration and reducing the workload of each assembly and maintenance task.

[0075] Furthermore, the present invention is not limited to the first and second embodiments, and various modifications are possible without departing from the purpose of the present invention. In the following description of each modification and the drawings to which it refers, the same reference numerals are used to designate the same components as those in the above embodiments, and the description thereof will be omitted.

[0076] For example, in the first embodiment, the control device 130 is configured to immediately interrupt the welding process when the position of the welding tool 103 in the Z-axis direction reaches a predetermined lower limit position or upper limit position using the detection signal output from the Z-axis position detector 106. However, in this case, the control device 130 can also be configured to monitor only one of the lower limit position and the upper limit position of the welding tool 103 in the Z-axis direction. Moreover, the control device 130 can omit the monitoring control when the control of monitoring the position of the welding tool 103 in the Z-axis direction is not necessary. Note that the monitoring control of the position of the welding tool 103 in the Z-axis direction using the detection signal output from the Z-axis position detector 106 may be performed or omitted in the control device 130 in the second embodiment.

[0077] In the second embodiment, the friction stir welding apparatus 200 is configured to always execute the constant pressing force control using the detection signal output from the reaction force detector 210. However, the friction stir welding apparatus 200 can also be configured to selectively execute the constant pressing force control by the ball screw mechanism 107 in the first embodiment and the constant pressing force control using the detection signal output from the reaction force detector 210. In this case, the control device 130 may receive a designation of the constant pressing force control from the operator before starting the welding process or during the welding process. In addition, in the case where the friction stir welding apparatus 200 can selectively execute the constant pressing force control by the ball screw mechanism 107 and the constant pressing force control using the detection signal output from the reaction force detector 210, the reaction force detector 210 may be provided at a location other than the bolt 211 as in the conventional technology. For example, the reaction force detector 210 may be arranged to detect the deformation (distortion) of the work table 120.

[0078] In the second embodiment, the reaction force detector 210 is configured by attaching a piezoelectric effect element or a piezoresistive effect element to the inside or the outer surface of the bolt 211 as a fastener. However, the reaction force detector 210 only needs to be configured so that the welding tool 103 can detect the magnitude of the reaction force from the workpieces WK1, WK2. Therefore, the reaction force detector 210 can also be disposed, for example, between the bolt 108 and an object to be fastened that is fastened by the bolt 108.

[0079] 6, the reaction force detector 210 is formed in an annular shape through which the bolt 108 passes, and can be disposed between the bolt 108 and the displacement body 107b (object to be fastened). In this way, the reaction force detector 210 can be easily removed from between the bolt 108 and the displacement body 107b by removing the bolt 108 from the displacement body 107b.

[0080] In the second embodiment, the friction stir welding apparatus 200 is configured to include one reaction force detector 210. However, the friction stir welding apparatus 200 can also be configured to include two or more reaction force detectors 210. In this case, the friction stir welding apparatus 200 can replace at least one of the three bolts 108 other than the bolt 211 with the bolt 211 having the reaction force detector 210.

[0081] In this case, two reaction force detectors 210 by at least two bolts 211 can be selectively connected to the control device 130, so that the remaining reaction force detector 210 can be used as a spare. Also, by connecting all of the at least two reaction force detectors 210 to the control device 130, the control device 130 can perform constant pressing force control using detection signals output by each of the multiple reaction force detectors 210. In this case, the control device 130 can perform constant pressing force control using an average value of reaction forces represented by detection signals output by each of the multiple reaction force detectors 210, and can also selectively use the multiple reaction force detectors 210 by switching them in order.

[0082] In the first and second embodiments, the Z-axis displacement means constituted by the ball screw mechanism 107 and the Z-axis drive motor 109 is configured to displace the machining head 101 in the Z-axis direction relative to the work table 120. However, the displacement relationship between the machining head 101 and the work table 120 is relative. Therefore, the Z-axis displacement means can also be configured to displace the work table 120 in the Z-axis direction relative to the machining head 101. In this case, the reaction force detector 210 in the second embodiment may be provided on a bolt connecting the work table 120 and a displacement body constituting a ball screw mechanism for displacing the work table 120 in the Z-axis direction.

[0083] In the above first and second embodiments, the workpieces WK1 and WK2 are stacked on top of each other. However, the friction stir welding apparatus 100 can also perform welding on the butted portion where the workpieces WK1 and WK2 are butted against each other on the same plane on the work table 120.

[0084] In the first and second embodiments, the Z-axis position detector 106, the X-axis position detector 112, and the Y-axis position detector 117 for detecting the positions of the machining head 101 in the illustrated Z-axis, X-axis, and Y-axis directions are each configured with a linear scale. However, the Z-axis position detector 106, the X-axis position detector 112, and the Y-axis position detector 117 may be configured with something other than a linear scale as long as they can detect the positions of the machining head 101 in the illustrated Z-axis, X-axis, and Y-axis directions. For example, the Z-axis position detector 106, the X-axis position detector 112, and the Y-axis position detector 117 may be configured with an encoder provided on the Z-axis drive motor 109, the X-axis drive motor 114, and the Y-axis drive motor 119, respectively.

[0085] In the first and second embodiments, the friction stir welding apparatuses 100, 200 are configured as machine tools capable of performing cutting processing using a cutting tool such as an end mill in addition to welding processing. However, it goes without saying that the friction stir welding apparatuses 100, 200 may be configured as machines that perform only welding processing. [Explanation of symbols]

[0086] WK1,WK2…workpiece, 100... friction stir welding apparatus, 101... machining head, 101a... spindle, 101b... spindle drive motor, 102... spindle housing, 102a... mounting portion, 103... welding tool, 104... head base, 105a, 105b... linear guide, 106... Z-axis position detector, 107... ball screw mechanism, 107a... feed screw, 107b... displacement body, 108... bolt, 109... Z-axis drive motor, 110...column, 110a...mounting portion, 110b...leg portion, 111a, 111b...linear guide, 112...X-axis position detector, 113...ball screw mechanism, 113a...feed screw, 113b...displacement body, 114...X-axis drive motor, 115...bed, 115a...groove portion, 116a, 116b...linear guide, 117...Y-axis position detector, 118...ball screw mechanism, 118a...feed screw, 119...Y-axis drive motor, 120... work table, 120a... clamp, 121... tool magazine, 130: control device; 131: operation panel; 200... friction stir welding device, 210... reaction force detector, 211... bolt.

Claims

1. A processing head having a joining tool that is pressed against the stacked or butted workpieces while being rotationally driven; a Z-axis displacement means having a prime mover for reciprocatingly displacing the processing head in a Z-axis direction to approach or move away from the workpiece and for pressing the welding tool against the workpiece; A friction stir welding apparatus for joining the stacked or butted workpieces, comprising: The Z-axis displacement means is A ball screw that is rotationally driven by the prime mover; a displacement body that is threadably fitted to the ball screw and displaced in an axial direction by rotational driving of the ball screw to reciprocate the machining head in the Z-axis direction, The control device includes: A friction stir welding apparatus characterized in that, when the welding tool is pressed against the workpiece, constant pressing force control is executed, which controls the operation of the prime mover so that the welding tool is always pressed against the workpiece with a constant pressing force regardless of changes in the magnitude of the reaction force from the workpiece.

2. The friction stir welding apparatus according to claim 1, further comprising: The Z-axis displacement means is a reaction force detector that detects a magnitude of a reaction force from the workpiece when the welding tool is pressed against the workpiece and outputs the magnitude of the reaction force to the control device, The control device includes: A friction stir welding apparatus characterized in that, when the welding tool is pressed against the workpiece, a constant pressing force control and a constant pressing force control are selectively executed, in which the operation of the prime mover is controlled so that the welding tool is always pressed against the workpiece with a constant pressing force based on a detection signal from the reaction force detector.

3. A processing head having a joining tool that is pressed against the stacked or butted workpieces while being rotationally driven; A work table for supporting the workpiece; a Z-axis displacement means having a prime mover for reciprocatingly displacing the processing head in a Z-axis direction to approach or move away from the workpiece and for pressing the welding tool against the workpiece; A friction stir welding apparatus for joining the stacked or butted workpieces, comprising: The Z-axis displacement means is A ball screw that is rotationally driven by the prime mover; a displacement body to which the machining head or the work table is connected and which is threadably fitted to the ball screw and displaces in an axial direction by rotational driving of the ball screw, thereby displacing the machining head back and forth in the Z-axis direction; a reaction force detector that detects a magnitude of a reaction force from the workpiece when the welding tool is pressed against the workpiece and outputs the magnitude of the reaction force to the control device, The reaction force detector includes: a detection signal corresponding to the strain of a bolt that connects the processing head or the work table to the displacement body is output to the control device, The control device includes: A friction stir welding apparatus characterized in that, when the welding tool is pressed against the workpiece, constant pressing force control is executed, which controls the operation of the prime mover so that the welding tool is always pressed against the workpiece with a constant pressing force based on the detection signal from the reaction force detector.

4. In the friction stir welding apparatus according to claim 3, The reaction force detector includes: A friction stir welding device provided inside the bolt.

5. In the friction stir welding apparatus according to claim 3, The reaction force detector includes: A friction stir welding device, which is disposed between the bolt and an object to be fastened by the bolt.

6. In the friction stir welding apparatus according to claim 3, The bolt is provided in plurality, The reaction force detector includes: A friction stir welding apparatus characterized in that the bolts are provided on at least two of the plurality of bolts.

7. The friction stir welding apparatus according to claim 1, further comprising: a Z-axis position detector that detects a position of the welding tool in the Z-axis direction and outputs the position to the control device; The control device includes: A friction stir welding apparatus, characterized in that, when it is detected that the position of the welding tool in the Z-axis direction has reached a predetermined limit position, the constant pressing force control by the prime mover is interrupted.

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