Machine tool and machining system equipped with a workpiece changing device

Abstract

[Problem] To provide a machine tool equipped with a workpiece changer capable of reducing machining cycle time by reducing non-machining time, and also provide a corresponding machining system. [Solution] A workpiece changer 4 comprises: first and second hands 5A, 5B having a pair of fingers 51, 52 that grip a workpiece 9 and an actuator 53 that rotates the pair of fingers 51, 52; an arm 61 to which the first and second hands 5A, 5B are attached; a rotary drive device 8 that rotates the arm 61 about a rotary axis O3; and a workpiece change control unit 302 that controls the actuator 53 and the rotary drive device 8. The workpiece change control unit 302 controls the rotary drive device 8 to rotate the arm 61 a half-turn between a first rotary position where the workpiece 9 can be set on first and second headstocks 35, 36 by the first hand 5A and a second rotary position where the workpiece 9 can be set on the first and second headstocks 35, 36 by the second hand 5B.

Description

Technical Field

[0001] The present invention relates to a machine tool provided with a workpiece exchange device for exchanging a workpiece before processing and a workpiece after processing, and a processing system using the machine tool.

Background Art

[0002] Patent Document 1 describes a lathe provided with a workpiece loading / unloading device for carrying out a processed workpiece after processing outside the machine and carrying in a next processing workpiece inside the machine. The workpiece loading / unloading device has a workpiece holder for supporting the processed workpiece and the next processing workpiece, and a workpiece loader for carrying out the processed workpiece supported by the workpiece holder and supplying the next processing workpiece to the workpiece holder. The workpiece holder is configured such that a support member having a first support portion for supporting the processed workpiece and a second support portion for supporting the next processing workpiece moves between a workpiece receiving position for receiving the processed workpiece and a position outside the processing region. When the processing of the workpiece is completed, the support member moves to the workpiece receiving position to receive the processed workpiece on the first support portion and moves to the outside of the machine. The workpiece loader has a first workpiece gripping portion for gripping the processed workpiece supported by the first support portion and a second workpiece gripping portion for placing the previously gripped next processing workpiece on the second support portion, and performs the transfer of the processed workpiece and the next processing workpiece with the support member of the workpiece holder. Thereafter, the support member moves and the next processing workpiece placed on the second support portion is mounted on the main spindle, and the processing of the next processing workpiece is performed.

[0003] Patent Document 2 describes a lathe in which two steady rests for gripping a workpiece during processing are attached to both ends of a mounting arm. During the processing of the workpiece, one of the two steady rests grips the workpiece, and the other steady rest grips the workpiece sent by a conveyor. When the processing of the workpiece is completed, the mounting arm rotates 180°, the workpiece sent by the conveyor is carried to the processing position, and the processed workpiece is carried onto the conveyor.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2007-105846 [Patent Document 2] Japanese Patent Application Laid-Open No. 61-121852 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the method described in Patent Document 1, the time spent transferring a processed workpiece and the next workpiece between the workpiece holder and the workpiece loader constitutes non-processing time during which the workpiece cannot be processed. In the method described in Patent Document 2, the workpiece before processing and the workpiece after processing can be swapped by rotating the mounting arm, thus shortening the workpiece exchange time. However, because interference between the steady rest and tools must be avoided, there is a risk of restrictions on the processing location of the workpiece.

[0006] Therefore, the present invention aims to provide a machine tool and a machining system equipped with a workpiece changing device that can easily avoid interference between the workpiece changing device and tools, etc., while shortening the machining cycle time by reducing non-machining time. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a machine tool comprising a tool for machining a workpiece, a workpiece holding device for holding the workpiece and rotating it about a horizontal axis of rotation, and a feed device for moving the tool closer to and further away from the workpiece held by the workpiece holding device in a horizontal direction intersecting the axis of rotation of the workpiece, wherein the machine tool comprises a workpiece exchange device for exchanging the workpiece with the workpiece holding device, the workpiece exchange device comprising first and second hands having a pair of fingers for gripping the workpiece and actuators for rotating the pair of fingers, an arm to which the first and second hands are attached, a rotation drive device for rotating the arm about an axis of rotation parallel to the axis of rotation of the workpiece, and a control unit for controlling the actuators and the rotation drive device, wherein the first and second hands are attached to two positions on the arm that are symmetrical with respect to the axis of rotation of the arm, and the control unit has a first rotation position to which the workpiece can be set in the workpiece holding device by the first hand, and a second rotation position to which the workpiece can be set in the workpiece holding device by the second hand The rotary drive device is controlled to rotate the arm half a turn between a second rotation position in which it is possible to perform a certain operation, and after setting the workpiece before processing in the workpiece holding device, the pair of fingers that were gripping the workpiece are opened to a position that avoids interference with the components of the machine tool, including the tool, and after processing of the workpiece is completed and the tool is separated from the workpiece by the feed device, the actuator is controlled to close the pair of fingers to grip the processed workpiece, the arm is a flat plate-shaped long plate whose longitudinal direction is perpendicular to the rotation axis of the arm, the control unit controls the actuator so that the longitudinal direction of the arm is vertical at the first rotation position and the second rotation position, the position in which the workpiece holding device holds the workpiece is on the tool side of the vertical line passing through the rotation axis of the arm, the first hand is mounted inclined with respect to the longitudinal direction of the arm so that the gripping position of the workpiece at the first rotation position is on the tool side of the vertical line passing through the rotation axis of the arm, and the second hand is,The present invention provides a machine tool equipped with a workpiece changing device, wherein the arm is mounted at an inclination with respect to the longitudinal direction of the arm such that the gripping position of the workpiece at the second rotational position is on the tool side of the vertical line passing through the rotation axis of the arm.

[0008] Furthermore, in order to achieve the above objectives, the present invention provides a machining system comprising a machine tool equipped with the above-described workpiece exchange device and a loader for transporting the workpiece between a plurality of machine tools, wherein the control unit controls the actuator of the other of the first and second hands to transfer the workpiece between the loader and the other hand, after the workpiece has been set in the workpiece holding device by one of the first and second hands and until the machining of the workpiece set in the workpiece holding device is completed. [Effects of the Invention]

[0009] According to the machine tool and machining system equipped with the workpiece changing device of the present invention, interference between the workpiece changing device and tools, etc., can be easily avoided, while the machining cycle time can be shortened by reducing non-machining time. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing an example of the configuration of a processing system according to an embodiment of the present invention. [Figure 2A] Figure 2A is a diagram showing some of the components of a machine tool, indicated by dashed lines. [Figure 2B] Figure 2B is a diagram showing the configuration of a machine tool with some of its components omitted. [Figure 3] This is a diagram showing some of the components of a machine tool, including a workpiece changing device, viewed from a direction parallel to the rotation axis of the workpiece. [Figure 4] This is a diagram showing some of the components of a machine tool, including a workpiece changing device, viewed from a direction parallel to the rotation axis of the workpiece. [Figure 5A]Figure 5A is a diagram showing one end of the first hand and arm. [Figure 5B] Figure 5B is a diagram showing one end of the first hand and arm. [Figure 6A] Figure 6A is a cross-sectional view showing an example of the configuration of a rotary drive device. [Figure 6B] Figure 6B is a cross-sectional view showing an example of the configuration of a rotary drive device. [Figure 7A] Figure 7A is a diagram showing an example of the configuration of a rotation stopper section for positioning the arm in the rotational direction. [Figure 7B] Figure 7B is a cross-sectional view along line AA in Figure 7A. [Figure 8] This is a cross-sectional view showing the configuration of the fixing mechanism. [Modes for carrying out the invention]

[0011] [Embodiment] Embodiments of the present invention will be described with reference to the drawings. The embodiments described below are shown as preferred specific examples for carrying out the present invention, and some parts specifically illustrate various technically preferable technical matters, but the technical scope of the present invention is not limited to these specific embodiments.

[0012] Figure 1 is a configuration diagram showing an example of the configuration of a processing system 1 according to an embodiment of the present invention. Figure 2A is a configuration diagram showing some of the components of the processing system 1 with dashed lines. Figure 2B is a configuration diagram showing some of the components of the processing system 1 omitted.

[0013] The processing system 1 comprises a plurality of machine tools and a loader 10 for transporting the workpiece 9 between the plurality of machine tools. The plurality of machine tools in the processing system 1 include machine tools 21 and 22 that perform pre- and post-grinding processes, and a grinding machine 3 that performs the grinding process. The grinding machine 3 is controlled by a control device 300 and performs the grinding process of the workpiece 9. The grinding machine 3 is also equipped with a workpiece exchange device 4 for transferring the workpiece 9 to and from the loader 10.

[0014] The loader 10 conveys the workpiece 9 from the machine tool 21 that performs the pre-grinding process to the grinding machine 3, and conveys the workpiece 9 that has been grinding-processed by the grinding machine 3 to the machine tool 22 that performs the post-process.

[0015] The grinding machine 3 performs grinding by pressing a grinding wheel 30 as a tool against the workpiece 9 while rotating the workpiece 9. Hereinafter, the horizontal direction along the rotation axis O1 of the workpiece 9 is defined as the Z-axis direction, the horizontal direction perpendicular to the Z-axis direction is defined as the X-axis direction. Also, the vertical direction perpendicular to the Z-axis direction and the X-axis is defined as the Y-axis direction. The grinding machine 3 performs grinding of the workpiece 9 by moving the grinding wheel 30 forward and backward in the X-axis direction with respect to the workpiece 9.

[0016] The grinding machine 3 includes a bed 31 as a base, a traverse table 32 movable in the Z-axis direction with respect to the bed 31, a grinding wheel base 33 movable in the X-axis direction with respect to the traverse table 32, a grinding wheel base body 34 attached to the grinding wheel base 33, first and second spindle heads 35, 36 as a workpiece holding device that holds and rotationally drives the workpiece 9, and a dimension measuring device 37 that measures the outer diameter of the workpiece 9.

[0017] The first and second spindle heads 35, 36 each have a spindle head motor 351, 361 that generates torque for rotating the workpiece 9, and centers 352, 362 that sandwich and hold the workpiece 9 in the axial direction. The pair of centers 352, 362 are fitted into center holes formed in the axial end faces of the workpiece 9 at their tip ends to position the workpiece 9, and rotate the workpiece 9 by the torque of the spindle head motors351, 361.

[0018] The bed 31 is provided with Z-axis guide rails 321 and 322 that guide the traverse table 32 in the Z-axis direction, and the traverse table 32 moves along the Z-axis guide rails 321 and 322 by the rotation of a ball screw 324 driven by a Z-axis motor 323. The traverse table 32 is provided with X-axis guide rails 331 and 332 that guide the grinding wheel base 33, and the grinding wheel base 33 moves along the X-axis guide rails 331 and 332 relative to the traverse table 32 by the rotation of a ball screw 334 driven by an X-axis motor 333. The X-axis guide rails 331 and 332, the X-axis motor 333, and the ball screw 334 constitute a feed device that moves the grinding wheel 30 closer to and further away from the workpiece 9.

[0019] The grinding wheel holder body 34 has a housing 340 fixed to the grinding wheel holder base 33, and a grinding wheel motor 341 is housed as a built-in motor within the housing 340. The grinding wheel motor 341 rotates the grinding wheel 30 via a grinding wheel shaft 342 supported by bearings within the housing 340. The grinding wheel 30 is rotationally driven by the grinding wheel motor 341 to grind the workpiece 9. The rotation axis O2 of the grinding wheel 30 is parallel to the rotation axis O1 of the workpiece 9.

[0020] Figures 3 and 4 show a portion of the loader 10, grinding wheel 30, grinding wheel base 33, grinding wheel motor 341, first headstock 35, sizing device 37, workpiece 9, and workpiece changing device 4 as viewed from the Z-axis direction, along with a coolant nozzle 19 that supplies coolant to the grinding area of ​​the workpiece 9. The coolant nozzle 19 moves in the X-axis and Z-axis directions together with the grinding wheel base 33. Figure 3 shows the state of the workpiece 9 just before grinding. Figure 4 shows the state during grinding.

[0021] As shown in Figure 1, the loader 10 has three drive motors 101 to 103 and travels along the rail 100, and is capable of moving the loader hand 104 vertically and horizontally perpendicular to the rail 100. The rail 100 crosses above the machine tool 2, and a portion of the rail 100 is omitted from the illustration in Figure 1.

[0022] The loader hand 104 of the loader 10 has first and second gripping parts 105 and 106 for gripping workpieces 9, and it is possible to transport two workpieces 9 simultaneously using the first and second gripping parts 105 and 106. The loader 10 also has a loader arm 107 that extends in the vertical direction, and a wrist part 108 that can rotate the loader hand 104 180° relative to the lower end of the loader arm 107. The rotation axis O of the loader hand 104 by the wrist part 108 is inclined at 45° with respect to the vertical direction. When the loader hand 104 is rotated 180° by the wrist part 108, the first gripping part 105 and the second gripping part 106 are swapped. When the loader hand 104 is rotated by the wrist part 108, the loader arm 107 rises to prevent interference.

[0023] The measuring device 37 comprises a measuring device body 370, a first measuring head 371 having a first measuring probe 371a at its tip, a second measuring head 372 having a second measuring probe 372a at its tip, and a moving mechanism 38 that moves the measuring device body 370 together with the first measuring head 371 and the second measuring head 372. The measuring device 37 places the workpiece 9 between the first measuring head 371 and the second measuring head 372, and detects the outer diameter of the workpiece 9 by bringing the first measuring probe 371a and the second measuring probe 372a into contact with the surface of the workpiece 9. The detection result information from the measuring device 37 is sent to the control device 300. Grinding of the workpiece 9 is performed while measuring the outer diameter of the grinding area by the grinding wheel 30 using the measuring device 37.

[0024] The moving mechanism 38 moves the main body of the measuring device 370 in the Z-axis direction, and also moves the main body of the measuring device 370 closer to and further away from the workpiece 9 along a direction of movement that is inclined with respect to the X-axis and Y-axis directions. In Figures 3 and 4, the direction of approach and separation of the main body of the measuring device 370 is indicated by arrow D1. This direction of approach and separation of the main body of the measuring device 370 is inclined downward in the vertical direction as it moves away from the workpiece 9, with respect to the X-axis direction, which is the direction of approach and separation of the grinding wheel 30 due to the rotation of the X-axis motor 333. In addition, as the main body of the measuring device 370 moves away from the workpiece 9, it moves away from the rotation axis O3 of the arm 61 in the Y-axis direction.

[0025] As shown in Figure 2B, the moving mechanism 38 comprises a moving platform 381, a ball screw 382, ​​a guide rail 383, a motor 384 for moving the fixed-size device that rotates the ball screw 382, ​​and a first slide table 385. Furthermore, as shown in Figures 3 and 4, the moving mechanism 38 includes a ball screw nut 386, a hydraulic cylinder 387, and a second slide table 388 that moves in the direction of arrow D1 by the hydraulic cylinder 387. The ball screw nut 386 is screwed onto the ball screw 382 via a plurality of balls.

[0026] The mobile table 381 is fixed to the bed 31. The ball screw 382 and guide rail 383 extend in the Z-axis direction and are supported on the mobile table 381. A ball screw nut 386 is fixed to the first slide table 385, and the motor 384 for moving the measuring device rotates the ball screw 382, ​​causing the first slide table 385 to move in the Z-axis direction, guided by the guide rail 383. The upper surface 385a of the first slide table 385 is a guide surface inclined with respect to the X-axis and Y-axis directions, and the second slide table 388 moves along this upper surface 385a. The main body 370 of the measuring device is fixed to the second slide table 388.

[0027] The moving mechanism 38 moves the measuring device 37 between the retracted position shown in Figure 3 and the measuring position shown in Figure 4. When moving the measuring device 37 from the retracted position to the measuring position, the hydraulic cylinder 387 advances the second slide table 388 along the upper surface 385a of the first slide table 385 toward the workpiece 9. During this advance, the measuring device 37 also moves in the Y-axis direction and rises vertically as it approaches the workpiece 9.

[0028] The measuring device 37 has a center line C perpendicular to the alignment direction of the first measuring head 371 and the second measuring head 372, which is inclined with respect to the X-axis and Y-axis directions, similar to the upper surface 385a of the first slide table 385. This inclined position of the measuring device 37 helps to avoid interference with the first and second hands 5A and 5B of the workpiece changing device 4, which will be described later.

[0029] The control device 300 includes a machining control unit 301 that controls each movable part of the grinding machine 3 to machine the workpiece 9, and a workpiece exchange control unit 302 that controls each movable part of the workpiece exchange device 4. The machining control unit 301 controls the Z-axis motor 323, X-axis motor 333, grinding wheel motor 341, headstock motors 351, 361, sizing device movement motor 384, and hydraulic cylinder 387. In this embodiment, the machining control unit 301 and the workpiece exchange control unit 302 are included in one control device 300, but the machining control unit 301 and the workpiece exchange control unit 302 may be separate and independent units. The workpiece exchange control unit 302 is a component of the workpiece exchange device 4.

[0030] As shown in Figure 2B, the workpiece 9 integrally comprises a first workpiece portion 91 and a second workpiece portion 92 that are ground by the grinding wheel 30, an intermediate portion 93 between the first workpiece portion 91 and the second workpiece portion 92, a cylindrical portion 94 at one end on the first headstock 35 side, and a cylindrical portion 95 at the other end on the second headstock 35 side. The first workpiece portion 91 and the second workpiece portion 92 are concentric cylinders centered on the rotation axis O1. The intermediate portion 93 is an unprocessed portion that is not ground, and its outer diameter is smaller than the outer diameters of the first workpiece portion 91 and the second workpiece portion 92. During machining of the workpiece 9, after grinding the first workpiece portion 91, the traverse table 32 is moved in the Z-axis direction to grind the second workpiece portion 92.

[0031] The workpiece changing device 4 receives the unprocessed workpiece 9 from the loader 10 and sets it on the first and second headstocks 35 and 36. The workpiece changing device 4 also removes the processed workpiece 9 from the first and second headstocks 35 and 36 and hands it over to the loader 10.

[0032] The workpiece changing device 4 comprises first and second hands 5A and 5B, an arm 61 to which the first and second hands 5A and 5B are attached, a shaft 62 that rotates integrally with the arm 61, a fixing mechanism 7 that fixes the arm 61 to the shaft 62, a rotary drive device 8 that rotates the arm 61 and shaft 62 together with the fixing mechanism 7 about a rotation axis O3, and a workpiece changing control unit 302. The rotation axis O3 of the arm 61 and shaft 62 is parallel to the rotation axis O1 of the workpiece 9 and is located vertically above the rotation axis O1 of the workpiece 9.

[0033] The arm 61 is a long, flat plate whose longitudinal direction is perpendicular to the rotation axis O3. The position of the rotation axis O3 of the arm 61 in the X-axis direction is further from the grinding wheel 30 than the positions of the pair of centers 352, 362 of the first and second headstocks 35, 36 in the X-axis direction, i.e., the holding position of the workpiece 9. The workpiece 9 is set between the grinding wheel 30 and the rotation axis O3 of the arm 61 in the X-axis direction.

[0034] The first and second hands 5A and 5B are attached to two positions on the arm 61, respectively, which straddles the axis of rotation O3. In this embodiment, the first hand 5A is fixed to one end of the arm 61, and the second hand 5B is fixed to the other end of the arm 61. The distance from the axis of rotation O3 to the first hand 5A is equal to the distance from the axis of rotation O3 to the second hand 5B, and the first hand 5A and the second hand 5B are swapped when the arm 61 rotates half a turn.

[0035] Figures 5A and 5B are configuration diagrams showing the first hand 5A and one end of the arm 61. Figure 5A shows the first hand 5A gripping the workpiece 9, and Figure 5B shows the first hand 5A not gripping the workpiece 9. In Figures 5A and 5B, a portion of the first hand 5A is cut away to show its internal structure. The second hand 5B is configured similarly to the first hand 5A.

[0036] The first hand 5A has a pair of fingers 51, 52 for gripping the workpiece 9, an actuator 53 for rotating the pair of fingers 51, 52, and a case 54 for housing the actuator 53. The actuator 53 includes a rack shaft 531 positioned between the pair of fingers 51, 52, and a cylinder 532 for moving the rack shaft 531 back and forth, and is configured such that the pair of fingers 51, 52 rotate as the rack shaft 531 moves back and forth. The same applies to the second hand 5B. The case 54 is fastened to the arm 61, for example, by bolts.

[0037] The direction of movement of the rack axis 531 is inclined with respect to the longitudinal direction of the arm 61. In Figure 5A, the direction of movement of the rack axis 531 relative to the case 54 is shown by the dashed line D2, and the longitudinal direction of the arm 61 perpendicular to the rotation axis O3 is shown by the dashed line D3. The inclination angle θ1 of the direction of movement of the rack axis 531 with respect to the longitudinal direction of the arm 61 is set to an angle that avoids interference between the first hand 5A and the sizing device 37 and the coolant nozzle 19. When the direction of movement of the rack axis 531 is the central axis direction of the first and second hands 5A and 5B, the direction of the inclination of the first and second hands 5A and 5B with respect to the longitudinal direction of the arm 61 is such that the workpiece 9 is set at a position on the grinding wheel 30 side in the X-axis direction relative to the rotation axis O3 of the arm 61, and the transfer of the workpiece 9 to the loader 10 is performed at a position on the opposite side of the grinding wheel 30 in the X-axis direction relative to the rotation axis O3 of the arm 61.

[0038] Each pair of finger portions 51 and 52 has multiple claw portions 511 and 521 for gripping the workpiece 9. Pinion gears 512 and 522 are integrated into the base ends of each pair of finger portions 51 and 52 by welding or the like. The pinion gears 512 and 522 have pinion teeth 512a and 522a that mesh with the rack teeth 531a of the rack shaft 531. A bifurcated support portion 541 and 542 is formed at one end of the case 54, protruding away from the rack shaft 531. The pinion gears 512 and 522 are housed in the space between the bifurcated support portions 541 and 542. Support shafts 543 and 544 are press-fitted and fixed into the support portions 541 and 542, and the support shafts 543 and 544 are gap-fitted into the pinion gears 512 and 522. The pair of finger portions 51 and 52 are rotatably supported on the support portions 541 and 542 via support shafts 543 and 544. As the rack shaft 531 moves, the pair of finger portions 51 and 52 rotate in opposite directions around the support shafts 543 and 544.

[0039] The closing operation of the first hand 5A is performed by moving the rack shaft 531 to its retracted end, as shown in Figure 5A. The opening operation of the first hand 5A is performed by moving the rack shaft 531 to its forward end, as shown in Figure 5B. The cylinder 532 houses the piston portion 531b provided on the rack shaft 531. Compressed air is supplied as a working medium to one side of the piston portion 531b, causing the rack shaft 531 to retract, and compressed air is supplied as a working medium to the other side of the piston portion 531b, causing the rack shaft 531 to advance. As shown in Figure 5B, the opening angle θ2 of the pair of fingers 51, 52 when the first hand 5A is opened is greater than 180°. As a result, when the pair of fingers 51, 52 open and release the workpiece 9, the pair of fingers 51, 52 rotate to a side further away from the workpiece 9 than the support shafts 543, 544. In the example shown in Figure 5B, the opening angle θ2 of the pair of finger parts 51 and 52 is 300°. When the pair of finger parts 51 and 52 are opened, a portion of each of the pair of finger parts 51 and 52 overlaps with the arm 61 in a view along the Z-axis.

[0040] In this embodiment, the workpiece exchange control unit 302 controls the actuators 53 of the first and second hands 5A and 5B by supplying compressed air to the cylinder 532. However, the actuator 53 is not limited to one that uses compressed air; for example, it may use hydraulic oil as a working fluid, or it may use an electric motor.

[0041] Figures 6A and 6B are cross-sectional views showing an example configuration of the rotary drive device 8. Figure 7A is a configuration diagram showing an example configuration of the rotary stopper portion 80 for positioning the arm 61 in the rotational direction. Figure 7B is a cross-sectional view along line AA in Figure 7A. In this embodiment, as with the first and second hands 5A and 5B, compressed air is used as the working medium to operate the rotary drive device 8.

[0042] The rotary drive unit 8 includes a housing 81 in which first and second cylinder chambers 811 and 812 are formed, a first piston member 82 housed in the first cylinder chamber 811, a second piston member 83 housed in the second cylinder chamber 812, a pinion gear 84 positioned between the first piston member 82 and the second piston member 83, and first and second ports 851 and 852 to which compressed air is supplied.

[0043] As shown in Figures 1 and 2A, the housing 81 is fixed to the front of the bed 31 on the worker side by a support member 311. In the example shown in Figures 1 and 2A, the mounting portion 311a of the support member 311 is directly fixed to the bed 31, but the support member 311 may be fixed to the bed 31 via other members.

[0044] As shown in Figure 7B, the shaft 62 is inserted through a through hole 311b formed in the support member 311 and rotates together with the arm 61 about the rotation axis O3. The shaft 62 is a hollow cylindrical shape with a space 620 formed in its center. This space 620 houses a plurality of tubes 530 for supplying compressed air to the actuators 53 of the first and second hands 5A and 5B. As shown in Figures 3 and 4, the plurality of tubes 530 are led out from the end of the shaft 62 opposite to the rotary drive device 8 and connected to the first and second hands 5A and 5B, respectively. Note that the plurality of tubes 530 are not shown in drawings other than Figures 3, 4 and 7B.

[0045] The housing 81 of the rotary drive unit 8 has a partition wall 813 that separates the first cylinder chamber 811 and the second cylinder chamber 812, and a housing portion 813a for housing the pinion gear 74 is formed in this partition wall 813. The pinion gear 74 is coaxially connected to the shaft 62, and the rotation of the pinion gear 74 causes the shaft 62 to rotate. The first and second piston members 82 and 83 each have a plurality of rack teeth 821 and 831 that mesh with the pinion gear 74.

[0046] In Figures 6A and 6B, the left-right direction corresponds to the X-axis direction. The first and second cylinder chambers 811 and 812 are formed extending in the X-axis direction, and the first and second piston members 82 and 83 move toward the grinding wheel 30 in the X-axis direction by compressed air supplied to the first and second ports 851 and 852. Figure 6A shows the state when compressed air is supplied to the first port 851, and Figure 6B shows the state when compressed air is supplied to the second port 852. The first and second piston members 82 and 83 move in opposite directions with the pinion gear 74 in between, causing the pinion gear 74 to rotate. The workpiece exchange control unit 302 controls the rotary drive unit 8 by switching the supply destination of the compressed air between the first port 851 and the second port 852.

[0047] As shown in Figures 7A and 7B, the rotation stopper section 80 includes a disc-shaped disk 800 fixed coaxially to the shaft 62, a stopper 802 fixed to the disk 800 by a plurality of bolts 801, L-shaped first and second mounting brackets 804 and 805 fixed to the support member 311 by a plurality of bolts 803, a first contact member 806 inserted through the first mounting bracket 804, a second contact member 807 inserted through the second mounting bracket 805, a pair of nuts 808 that fix the first contact member 806 to the first mounting bracket 804, and a pair of nuts 809 that fix the second contact member 807 to the second mounting bracket 805.

[0048] The disc 800 and the stopper 802 rotate together with the shaft 62. The arm 61 and the shaft 62 can rotate 180° between a first rotational position in which the stopper 802 abuts against the first contact member 806 and a second rotational position in which the stopper 802 abuts against the second contact member 807. The rotational stopper section 80 can adjust the positions of both ends of the arm 61 and the shaft 62 in the rotational direction by adjusting the fixed position of the first contact member 806 to the first mounting bracket 804 and the fixed position of the second contact member 807 to the second mounting bracket 805. In Figure 7A, the stopper 802 in contact with the first contact member 806 is shown by a solid line, and the stopper 802 in contact with the second contact member 807 is shown by a dashed line.

[0049] When the arm 61 is in the first rotation position, as shown in Figure 3, the first hand 5A can set the unprocessed workpiece 9 on the first and second headstocks 35 and 36. When the arm 61 is in the second rotation position, the second hand 5B can set the unprocessed workpiece 9 on the first and second headstocks 35 and 36. The workpiece exchange control unit 302 controls the rotary drive device 8 to rotate the arm 61 half a turn between the first and second rotation positions each time the machining of one workpiece 9 is completed.

[0050] Figure 8 is a cross-sectional view showing the configuration of the fixing mechanism 7. The fixing mechanism 7 allows the arm 61 to be fixed at any position in the longitudinal direction of the shaft 62, depending on the shape of the workpiece 9. In this embodiment, the arm 61 is fixed in a position that allows the pair of fingers 51, 52 of the first and second hands 5A, 5B to grip the intermediate portion 93 of the workpiece 9 held on the first and second headstocks 35, 36.

[0051] The fixing mechanism 7 is positioned between the inner circumferential surface 611a of the projection 611 of the arm 61 and the outer circumferential surface 62a of the shaft 62, and serves to fix the arm 61 to the shaft 62 so that it can move in the axial direction. The fixing mechanism 7 is composed of a cylindrical outer diameter side fitting member 71 positioned on the inner diameter side of the inner circumferential surface 611a of the projection 611 of the arm 61, an inner diameter side fitting member 72 positioned on the outer diameter side of the outer circumferential surface 62a of the shaft 62, which is axially movable relative to the shaft 62 and is also radially elastically deformable, and a plurality of clamp bolts 73 that move the outer diameter side fitting member 71 in the axial direction relative to the inner diameter side fitting member 72. The outer diameter side fitting member 71 and the inner diameter side fitting member 72 form a double cylindrical structure. The arm 61 has a through hole 61a through which the shaft 62 is inserted, and a cylindrical projection 611 is provided on the outer diameter side of the through hole 61a. The inner circumferential surface 71a of the outer diameter fitting member 71 is a tapered surface inclined with respect to the axial direction of the shaft 62.

[0052] The inner diameter fitting member 72 has an inner cylindrical portion 721 having a tapered outer surface 721a facing the inner circumferential surface 71a of the outer diameter fitting member 71, a wall portion 722 having a plurality of bolt insertion holes 722a through which a plurality of clamp bolts 73 are inserted, and an outer cylindrical portion 723 covering the outer circumferential surface 71b of the outer diameter fitting member 71. The outer diameter fitting member 71 has screw holes 711 formed at positions aligned with each of the plurality of bolt insertion holes 722a of the inner diameter fitting member 72. Each clamp bolt 73 is inserted through the bolt insertion hole 722a of the inner diameter fitting member 72 and screwed into the screw hole 711 of the outer diameter fitting member 71.

[0053] When fixing the arm 61 to the shaft 62, the clamp bolt 73 is tightened, and the axial force of the clamp bolt 73 pulls the projection 611 of the arm 61 and the outer diameter fitting member 71 towards the inner diameter fitting member 72. As a result, the outer diameter fitting member 71 expands in diameter, and its outer peripheral surface 71b is pressed against the inner peripheral surface 611a of the projection 611 of the arm 61, while the inner diameter fitting member 72 contracts in diameter, and the inner peripheral surface 721b of the inner cylindrical portion 721 is pressed against the outer peripheral surface 62a of the shaft 62. The frictional force generated between the inner peripheral surface 721b of the inner cylindrical portion 721 and the outer peripheral surface 62a of the shaft 62 then fixes the arm 61 to the shaft 62.

[0054] Next, the procedure for machining multiple workpieces 9 in succession using the machine tool 2 will be described. The machine tool 2 rotates its arm 61 to quickly swap the workpiece 9 held by the first hand 5A with the workpiece 9 held by the second hand 5B, thereby reducing non-machining time and shortening the cycle time.

[0055] More specifically, for example, while machining the workpiece 9 held by the first hand 5A, the already machined workpiece 9 is transferred to the loader 10 by the second hand 5B. Then, the loader arm 107 is raised and the loader hand 104 is rotated 180° by the wrist portion 108, transferring the unmachined workpiece 9 from the loader 10 to the second hand 5B. At this time, the first hand 5A is positioned vertically below the rotation axis O3, and the second hand 5B is positioned vertically above the rotation axis O3. After the machining of the workpiece 9 held by the first hand 5A is completed, the workpiece 9 is held by the first hand 5A, and the workpiece 9 held by the second hand 5B is set on the first and second headstocks 35 and 36 by the rotation of the arm 61. The workpiece 9, once processed, is handed over from the first hand 5A to the loader 10.

[0056] While the workpiece 9 is being transferred between the second hand 5B and the loader 10, the first hand 5A needs to be kept waiting near the first and second headstocks 35 and 36. As mentioned above, the machining of the workpiece 9 is performed by sequentially moving the traverse table 32 in the Z-axis direction to machine the first workpiece portion 91 and the second workpiece portion 92, which sandwich the intermediate portion 93. Therefore, it is necessary to avoid interference between the grinding wheel 30, the coolant nozzle 19 and the first hand 5A when the traverse table 32 is moving. In addition, as the dimensional measuring device body 370, the first measuring head 371 and the second measuring head 372 also move in the Z-axis direction as the traverse table 32 moves, it is also necessary to avoid interference between the dimensional measuring device body 370, the first measuring head 371 and the second measuring head 372 and the first hand 5A.

[0057] Therefore, the workpiece exchange control unit 302 controls the actuators 53 of the first and second hands 5A and 5B so that after setting the workpiece 9 before machining on the first and second headstocks 35 and 36, the pair of fingers 51 and 52 that were gripping the workpiece 9 are opened to a position that avoids interference with the components of the machine tool 2, and after machining of the workpiece 9 is completed and the grinding wheel 30 is separated from the workpiece 9 by the X-axis motor 333, the pair of fingers 51 and 52 are closed to grip the machined workpiece 9. Here, the components of the machine tool 2 are specifically the grinding wheel 30, the coolant nozzle 19, and the sizing device 37. In other words, after setting the workpiece 9 on the first and second headstocks 35 and 36, the first and second hands 5A and 5B open their pair of fingers 51 and 52 to a position where interference with the grinding wheel 30, coolant nozzle 19, and sizing device 37 is avoided.

[0058] Furthermore, after the workpiece exchange control unit 302 sets the workpiece 9 on the first and second headstocks 35 and 36 using one of the first and second hands 5A and 5B, and while the machining of the set workpiece 9 is being completed, it controls the actuator 53 of the other hand of the first and second hands 5A and 5B to transfer the workpiece 9 to the loader 10. This allows for the quick exchange of an unmachined workpiece 9 with a machined workpiece 9, thereby shortening the cycle time. In other words, according to the embodiment described above, the machining cycle time can be shortened by reducing non-machining time.

[0059] (Note) The present invention has been described above based on embodiments, but these embodiments do not limit the invention as defined in the claims. It should also be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention. Furthermore, the present invention can be implemented by omitting some components, or by adding or substituting components, without departing from its spirit. In addition, although the above embodiments were described using the case where the machine tool 2 is a grinding machine as an example, the present invention is not limited to this, and can also be applied to cutting machines or assembly machines, for example. [Explanation of symbols]

[0060] 1…Processing system 10... Loader 2…Grinding machine (machine tool) 302...Workpiece Exchange Control Unit 30…Grinding stone (tool) 331, 332… X-axis guide rail (feed device) 333...X-axis motor (feeder) 334...Ball screw (feeder) 35, 36… First and second spindles (workpiece holders) 37…Sizing device 370...Main unit of the measuring device 371...First measuring head 372...Second measuring head 38...Movement mechanism 4…Workpiece changer 51,52...Finger part 53…Actuator 5A... First hand 5B... Second hand 61... Arm 8…Rotary drive device 9...Workpiece

Claims

1. A machine tool comprising a tool for machining a workpiece, a workpiece holding device that holds the workpiece and rotates it about a horizontal axis of rotation, and a feed device that moves the tool closer to and further away from the workpiece held by the workpiece holding device in a horizontal direction intersecting the axis of rotation of the workpiece, The workpiece exchange device is provided for exchanging the workpiece with the workpiece holding device, The aforementioned workpiece exchange device is A first and second hand having a pair of fingers for gripping the workpiece and an actuator for rotating the pair of fingers, Arms to which the first and second hands are attached, A rotational drive device that rotates the arm about a rotation axis parallel to the rotation axis of the workpiece, The system comprises the actuator and a control unit that controls the rotary drive device, The first and second hands are attached to two positions on the arm that are symmetrical with respect to the rotation axis of the arm, The control unit, The rotation drive device is controlled to rotate the arm by half a turn between a first rotation position in which the workpiece can be set in the workpiece holding device by the first hand and a second rotation position in which the workpiece can be set in the workpiece holding device by the second hand, After setting the workpiece before processing in the workpiece holding device, the pair of fingers that were gripping the workpiece are opened to a position that avoids interference with the components of the machine tool, including the tool, and after the processing of the workpiece is completed and the tool is separated from the workpiece by the feed device, the actuator is controlled to close the pair of fingers to grip the processed workpiece. The aforementioned arm is a flat, elongated plate whose longitudinal direction is perpendicular to the axis of rotation of the arm. The control unit controls the actuator so that the longitudinal direction of the arm is vertical at the first rotation position and the second rotation position. The position in which the workpiece holding device holds the workpiece is on the tool side of the vertical line passing through the rotation axis of the arm, The first hand is mounted at an inclination with respect to the longitudinal direction of the arm such that the gripping position of the workpiece at the first rotational position is on the tool side of the vertical line passing through the rotation axis of the arm, The second hand is mounted at an inclination with respect to the longitudinal direction of the arm such that the gripping position of the workpiece at the second rotational position is on the tool side of the vertical line passing through the rotational axis of the arm. A machine tool equipped with a workpiece changing device.

2. The tool is a grinding wheel, and the workpiece is ground while supplying coolant to the grinding area of ​​the workpiece from a coolant nozzle and measuring the outer diameter of the grinding area by the grinding wheel using a measuring device. After setting the workpiece in the workpiece holding device, the pair of fingers are opened by the opening operation to a position where interference with the grinding wheel, the coolant nozzle, and the sizing device is avoided. A machine tool equipped with the workpiece changing device described in claim 1.

3. The measuring device comprises a measuring device body, a first measuring head having a first measuring probe at its tip that contacts the workpiece, a second measuring head having a second measuring probe at its tip that contacts the workpiece, and a moving mechanism that moves the measuring device body closer to and further away from the workpiece, wherein the workpiece is sandwiched between the first measuring head and the second measuring head, and the outer diameter of the workpiece is detected by bringing the first measuring probe and the second measuring probe into contact with the surface of the workpiece. The main body of the measuring device is positioned vertically below the rotation axis of the arm. The approach and separation direction of the main body of the measuring device is inclined downward in the vertical direction as it moves away from the tool. A machine tool equipped with the workpiece changing device described in claim 2.

4. The actuator comprises a rack shaft positioned between the pair of finger parts, a pair of pinion gears having pinion teeth that mesh with the rack teeth of the rack shaft, and a cylinder that moves the rack shaft forward and backward, and is configured such that the pair of finger parts rotate in opposite directions around a support shaft that supports the pair of pinion gears as the rack shaft moves forward and backward. The direction of movement of the rack axis is inclined with respect to the longitudinal direction of the arm. In the direction of the tool's approach and separation by the feed device, the rotation axis of the arm is at a position further from the grinding wheel than the workpiece holding position by the workpiece holding device. A machine tool equipped with a workpiece changing device according to claim 2 or 3.

5. When the pair of fingers are opened, the opening angle is greater than 180°. A machine tool equipped with the workpiece changing device described in claim 4.

6. A machine tool equipped with the workpiece changing device described in claim 1, The system includes a loader that transports the workpiece between multiple machine tools, The control unit controls the actuator of the other hand of the first and second hands to transfer the workpiece between the loader and the other hand, after the workpiece has been set in the workpiece holding device by one of the first and second hands, until the machining of the workpiece set in the workpiece holding device is completed. Processing system.

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