JP2015096280A - Machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a machine tool which can reduce impact at the time of mounting a tool on a main shaft thereof when replacing the tool.SOLUTION: After a tool magazine is rotated (S6: YES), a position of a taper mounted part of a tool holder may be displaced relative to a position of a taper hole of a main shaft. A main shaft head starts to descend from an ATC original point (S7), and when the main shaft head reaches a predetermined position (S8: YES), a CPU switches a position control for a magazine motor 55 to a second control (S9). The predetermined position is a position immediately before a position where the taper mounted part enters the taper hole and the outer peripheral face of the taper mounted part contacts the inner peripheral face of the taper hole. Torque imparted by the magazine motor to a decelerator by the second control is lowered further than torque imparted to the decelerator by a first control. The tool magazine is set to be rotatable by external energizing force so that the outer peripheral face of the taper mounted part slides along the inner peripheral face of the taper hole. The taper mounted part can be easily mounted to the taper hole.

Description

  The present invention relates to a machine tool capable of tool change.

  The machine tool includes a spindle head, a spindle, and a tool changer. The spindle head is provided so as to be able to move up and down along a column standing on the base, and supports the spindle in a rotatable manner. Patent Document 1 discloses a tool changer provided with a tool magazine. The tool magazine is a disk-like shape that rotates around one axis and is arranged in front of the spindle head, and has a plurality of grip arms on the outer periphery. The grip arm grips the tool detachably. The magazine motor is connected to the tool magazine via a reduction gear. The reducer transmits the rotation of the magazine motor to the tool magazine. The machine tool performs indexing of the rotation of the tool magazine through the speed reducer by controlling the position of the magazine motor.

  When changing the tool, the spindle head rises from the machining position of the workpiece through the Z-axis origin. The grip arm grips the used current tool attached to the spindle. The spindle head rises further, removes the tool from the spindle, and rises to the ATC origin. The tool magazine is rotated by the position control of the magazine motor, and the grip arm that holds the tool to be used next is moved directly below the spindle. The spindle head descends from the ATC origin, and the grip arm mounts the next tool to be used on the spindle. The spindle head descends to the Z-axis origin.

JP 2012-206227 A

  The accuracy of the relative position of the spindle and tool magazine is important. The accuracy of the relative position greatly depends on the speed reducer. If the position of the next tool to be gripped by the grip arm shifts with respect to the spindle after the tool magazine rotates, the impact when the tool is mounted on the spindle becomes large. The cause is due to the rigidity of the spindle and tool magazine. The spindle, the tool magazine, and the reducer are subjected to a large load, which may cause a failure.

  An object of the present invention is to provide a machine tool capable of reducing an impact when a tool is mounted on a main shaft at the time of tool replacement.

  A machine tool according to a first aspect of the present invention includes a spindle for mounting a tool to process a workpiece, a storage unit for storing the tool to be mounted on the spindle, and the tool stored in the storage unit at a predetermined position. A transport mechanism for transporting, a transport motor for driving the transport mechanism, torque control means for controlling a torque applied to the transport mechanism of the transport motor, and the tool transported to the predetermined position by the transport mechanism. In the machine tool provided with the mounting means to be mounted on, the torque control means transfers the torque to the transfer mechanism at least during transfer of the tool after the tool is transferred to the predetermined position by the transfer mechanism. It is characterized by having a torque lowering means for lowering than that. After the transport mechanism transports the tool to a predetermined position, the torque reducing means lowers the torque of the transport motor below the transport torque. Therefore, even when the position of the tool transported to a predetermined position with respect to the main shaft is shifted in tool replacement, the position of the tool can be moved in accordance with the position of the main shaft. Therefore, the machine tool can reduce the load applied to the transport mechanism. Since the machine tool can reduce the impact on the spindle, the storage unit, and the transport mechanism when a tool is mounted on the spindle, failure of each part can be prevented. Since the machine tool can satisfactorily mount the tool on the spindle even with the conventional positioning accuracy of the transport mechanism, the cost for improving the positioning accuracy of the transport mechanism can be reduced.

  A machine tool according to a second aspect of the present invention is the machine tool according to the first aspect, wherein the torque reducing means transports the tool to the predetermined position by the transport mechanism, and then the mounting means moves to the predetermined position. Immediately before mounting the tool transported to the main shaft, the torque is made lower than the transport torque. The torque lowering means lowers the torque below the conveying torque immediately before mounting the tool on the main shaft, so that the conveying torque is applied to the conveying mechanism until just before mounting the tool at a predetermined position on the main shaft. Therefore, the machine tool can prevent the transport mechanism from being unstablely moved by an external impact until immediately before the tool is mounted on the spindle.

  A machine tool according to a third aspect of the present invention is the machine tool according to the first or second aspect, wherein the storage portion is a disc-shaped main body rotatable around a single axis, and an outer periphery of the main body. And a plurality of grip arms for holding the tool, wherein the transport mechanism reduces the rotational speed of the transport motor to rotate the tool magazine in the circumferential direction, and A reduction device that positions the tool held by one grip arm of the grip arms at the predetermined position, wherein the main shaft performs a machining operation on the workpiece on the workpiece side with respect to the workpiece in the axial direction. It is possible to move between a machining area to be performed and a tool exchange area for exchanging the tool with the tool stored in the storage unit in an area opposite to the machining area from the origin position, and the mounting Means In serial tool change area, the main shaft, by moving toward the tool which the conveying mechanism is conveyed to the predetermined position, characterized by mounting the tool on the spindle. The present invention can be applied to a machine tool including a turret type tool magazine. Even with the positioning accuracy of the conventional reduction gear, the tool can be mounted on the main shaft satisfactorily.

  According to a fourth aspect of the present invention, in the machine tool according to the third aspect, in addition to the configuration of the third aspect, the torque control means may be configured such that the torque changing means reduces the torque below the conveying torque, and then the tool change area. And a torque return means for returning the torque to at least the transport torque when the actuator moves to the origin position. ) Torque lowered when the tool is mounted returns at the origin position. After the movement to the origin position, since the conveyance torque is applied to the conveyance mechanism, it is possible to prevent the conveyance mechanism from being unstablely moved by an external impact.

  A machine tool according to a fifth aspect of the present invention is the machine tool according to the first aspect, wherein after the tool is transported to the predetermined position by the torque detection means for detecting the torque applied to the transport mechanism and the transport mechanism. Determining means for determining whether or not the torque detected by the torque detecting means is greater than or equal to a predetermined value, and the torque reducing means is configured to determine whether the torque is greater than or equal to the predetermined value. Is at least lower than the conveying torque. When the torque detection means detects a torque greater than or equal to a predetermined value, the position of the tool transported to a predetermined position with respect to the spindle may be displaced. When a torque greater than a predetermined value is detected, the machine tool lowers the torque at least below the conveying torque. The position of the tool can be moved according to the position of the spindle. Therefore, the machine tool can reduce the load applied to the transport mechanism.

1 is a perspective view of a machine tool 1. FIG. 3 is a partially cutaway view around the spindle head 7. FIG. 3 is a block diagram showing an electrical configuration of the machine tool 1 and the numerical control device 30. The block diagram for demonstrating the outline | summary of the position control of the magazine motor 55 by CPU31 and the drive circuit 55A. The flowchart of a tool exchange process. The figure which shows the raising / lowering operation | movement of the spindle head 7 in a tool exchange operation | movement. A partially cutaway view around the spindle head 7 of Z490. The partially broken view around the spindle head 7 of Z500. FIG. 10 is a partially cutaway view around the spindle head 7 of Z510. A partially broken view around the spindle head 7 at Z615 (ATC origin). The flowchart of the modification of a tool exchange process.

  An embodiment of the present invention will be described with reference to the drawings. The following description uses up and down, left and right, and front and back indicated by arrows in the figure. The left-right direction, the front-rear direction, and the up-down direction of the machine tool 1 are the X-axis direction, the Y-axis direction, and the Z-axis direction of the machine tool 1, respectively.

  The structure of the machine tool 1 will be described with reference to FIG. The machine tool 1 includes a base 2, a machine body 3, a table 10, a tool changer 20, and the like. The base 2 is a substantially rectangular parallelepiped base made of iron. The machine body 3 is provided at the upper rear of the base 2 and cuts a work (not shown) held on the upper surface of the table 10. The table 10 is provided at the upper center of the base 2 and can be moved in the X-axis direction and the Y-axis direction by an X-axis motor 53, a Y-axis motor 54 (see FIG. 3), and a guide mechanism (not shown). The tool changer 20 is fixed to a frame 8 provided on the upper part of the machine main body 3, and the tool 4 mounted on the main shaft 9 of the machine main body 3 is exchanged with another tool.

  The machine tool 1 includes an operation panel (not shown). The operation panel includes an input unit 24 and a display unit 25 (see FIG. 3). The operator inputs an NC program, a tool type, tool information, various parameters, and the like through the input unit 24. When the operator operates the input unit 24, the display unit 25 displays various input screens or operation screens.

  The configuration of the machine body 3 will be described with reference to FIG. The machine body 3 includes a column 5, a spindle head 7, a spindle 9, a control box 6, and the like. The column 5 is erected on the upper rear side of the base 2. The spindle head 7 can move up and down in the Z-axis direction along the front surface of the column 5. The spindle head 7 supports the spindle 9 rotatably inside. The spindle 9 is equipped with a tool holder 17 (see FIG. 2) and rotates at high speed by driving a spindle motor 52 (see FIGS. 2 and 3). The spindle motor 52 is provided on the spindle head 7. The tool holder 17 holds the tool 4. The control box 6 stores a numerical control device 30 (see FIG. 3). The numerical control device 30 controls the operation of the machine tool 1.

  As shown in FIG. 2, the spindle head 7 is moved up and down in the Z-axis direction by a Z-axis moving mechanism provided on the front surface of the column 5. The Z-axis moving mechanism includes a pair of Z-axis linear guides (not shown), a Z-axis ball screw 26 (see FIG. 2), and a Z-axis motor 51 (see FIG. 3). The Z-axis linear guide extends in the Z-axis direction and guides the spindle head 7 in the Z-axis direction. The Z-axis ball screw 26 is disposed between a pair of Z-axis linear guides and is rotatably provided by an upper bearing portion 27 and a lower bearing portion (not shown). The spindle head 7 includes a nut 29 (see FIG. 2) on the back surface. The nut 29 is screwed into the Z-axis ball screw 26. The Z-axis motor 51 rotates the Z-axis ball screw 26 in the forward and reverse directions. Therefore, the spindle head 7 moves in the Z-axis direction together with the nut 29.

  The internal structure of the spindle head 7 will be described with reference to FIG. The spindle head 7 rotatably supports the spindle 9 inside the lower front part. The main shaft 9 has a rotation axis in the vertical direction. The main shaft 9 is connected to the drive shaft of the main shaft motor 52 via a coupling 23. Therefore, the main shaft 9 is rotated by the rotation drive of the main shaft motor 52. The main shaft 9 includes a tapered hole 18, a holder clamping member 19, and a draw bar 81. The tapered hole 18 is provided at the tip (lower end) of the main shaft 9. The holder clamping member 19 is provided above the tapered hole 18. The draw bar 81 is provided by being coaxially inserted into a shaft hole passing through the center of the main shaft 9.

  The tool holder 17 holds the tool 4 on one end side, and includes a taper mounting portion 17A and a pull stud 17B on the other end side. The taper mounting portion 17A is substantially conical. The pull stud 17B protrudes in the axial direction from the top of the taper mounting portion 17A. The tapered mounting portion 17A is mounted in the tapered hole 18 of the main shaft 9. When the taper mounting portion 17A is mounted in the taper hole 18, the holder clamping member 19 clamps the pull stud 17B. When the draw bar 81 presses the holder holding member 19 downward, the holder holding member 19 releases the pull stud 17B.

  The spindle head 7 is provided with a crank lever 60 inside the rear upper part. The crank lever 60 is substantially L-shaped and can swing around a support shaft 61. The spindle 61 is fixed in the spindle head 7. The crank lever 60 includes a vertical lever 63 and a horizontal lever 62. The longitudinal lever 63 extends obliquely upward from the support shaft 61 to the column 5 side, bends upward at the intermediate portion 65, and further extends upward. The lateral lever 62 extends substantially horizontally from the support shaft 61 to the front of the column 5. The front end of the lateral lever 62 can be engaged from above with a pin 58 projecting perpendicularly to the draw bar 81. The vertical lever 63 includes a plate cam body 66 on the back surface of the upper end portion. The plate cam body 66 has a cam surface on the column 5 side. The cam surface of the plate cam body 66 can be brought into and out of contact with a cam follower 67 fixed to the upper bearing portion 27. The cam follower 67 slides on the cam surface of the plate cam body 66. A tension coil spring (not shown) is elastically provided between the longitudinal lever 63 and the spindle head 7. When the crank lever 60 is viewed from the right side, the tension coil spring constantly urges the crank lever 60 clockwise. Therefore, the crank lever 60 always releases the downward pressing of the pin 58 by the lateral lever 62.

  With reference to FIGS. 6 to 9, the operation of detaching the tool holder 17 from the tapered hole 18 of the main shaft 9 will be described. As shown in FIG. 6, the spindle head 7 ascends with the taper mounting portion 17 </ b> A of the tool holder 17 installed in the tapered hole 18 of the spindle 9. The plate cam body 66 provided on the crank lever 60 contacts the cam follower 67 and slides. As shown in FIG. 7, the grip portion 91 of the grip arm 90 described later grips the tool holder 17, and the cam follower 67 slides along the cam shape of the plate cam body 66. The crank lever 60 rotates counterclockwise around the support shaft 61 when viewed from the right side. The lateral lever 62 engages with the pin 58 from above and presses the draw bar 81 downward. The draw bar 81 urges the holder holding member 19 downward. The holder clamping member 19 releases the pull stud 17B. As shown in the order of FIGS. 8 and 9, the spindle head 7 is further raised to the ATC origin. The tool holder 17 comes out of the tapered hole 18 of the main shaft 9. Removal of the tool holder 17 is completed with respect to the tapered hole 18 of the main shaft 9.

  When the spindle head 7 reaches the ATC origin, a magazine base 71 (to be described later) of the tool changer 20 rotates, and the tool changer 20 determines the tool specified by the NC program control command at the tool change position. The tool change position is the lowest position of the tool magazine 21 and a position facing the spindle 9 in the vicinity. The tool indexed to the tool change position is located below the spindle head 7 that has moved to the ATC origin.

  Next, as shown in the order of FIGS. 9 and 8, the spindle head 7 descends from the ATC origin, and the tapered mounting portion 17 </ b> A of the tool holder 17 enters the tapered hole 18 of the spindle 9. With the taper mounting portion 17A of the tool holder 17 inserted into the taper hole 18 of the main shaft 9, the main shaft head 7 is further lowered. The plate cam body 66 provided on the crank lever 60 slides on the cam follower 67. A cam follower 67 slides along the cam shape of the plate cam body 66. As shown in FIG. 7, the crank lever 60 rotates clockwise about the support shaft 61 when viewed from the right side. Therefore, the lateral lever 62 is separated from the pin 58 to release the downward pressing of the draw bar 81. The draw bar 81 releases the downward biasing of the holder clamping member 19, and the holder clamping member 19 clamps the pull stud 17B. As shown in FIG. 6, the mounting of the tool holder 17 is completed in the tapered hole 18 of the main shaft 9.

  The structure of the tool changer 20 will be described with reference to FIG. The tool changer 20 includes a tool magazine 21. The tool magazine 21 is a turret type. The tool magazine 21 includes a magazine base 71 and a plurality of grip arms 90. The magazine base 71 has a disk shape. The plurality of grip arms 90 are provided so as to be swingable in the front-rear direction along the outer periphery of the magazine base 71. The magazine support 45 is fixed to the frame 8. The frame 8 is fixed to the column 5 and arranged close to the spindle head 7. The magazine support 45 supports the support shaft 75 in a rotatable manner. The support shaft 75 extends obliquely downward with respect to the front of the machine tool 1. The support shaft 75 rotatably supports the magazine base 71. The magazine base 71 is arranged with the front side facing the front of the machine tool 1.

  The structure of the magazine base 71 will be described with reference to FIG. The magazine base 71 includes a boss portion 73 and a collar portion 72. The boss 73 is cylindrical. The support shaft 75 is inserted into the boss portion 73. The flange portion 72 is provided on the front end side of the outer peripheral surface of the boss portion 73 so as to be orthogonal to the axial direction. The boss 73 fixes the indexing disc 77 to the rear end. The indexing disc 77 has a plurality of cam followers (not shown) on the back side (surface facing the spindle head 7) with the support shaft 75 as the center. The plurality of cam followers are arranged corresponding to the positions of the plurality of grip arms 90, respectively.

  The speed reducer 41 is fixed to the upper part of the magazine support 45. The speed reducer 41 has a plurality of gears and a cam (not shown). The magazine motor 55 is fixed to the upper part of the speed reducer 41. The rotation shaft of the magazine motor 55 is connected to the speed reducer 41. The plurality of cam followers of the indexing disc 77 are fitted into cam grooves (not shown) formed in the cam of the speed reducer 41, respectively. Therefore, the indexing disc 77 can index one of the plurality of grip arms 90 and move to the lowest position of the magazine base 71.

  The magazine base 71 fixes a plurality of fulcrum stands 78 along the outer periphery of the back surface. The fulcrum stand 78 supports the grip arm 90 so that it can swing around a pivot shaft 85. The grip arm 90 includes a grip portion 91 at one end. The grip part 91 can grip a tool. The grip arm 90 rotatably supports the cam follower 93 in the vicinity of the pivot shaft 85 toward the spindle head 7 side. The cam follower 93 slides on the inclined surface of the cam body 11 fixed to the front surface of the spindle head 7 as the spindle head 7 moves up and down. The grip arm 90 swings around the pivot shaft 85. The grip portion 91 of the grip arm 90 that is indexed to the tool change position of the magazine base 71 can swing between the proximity position and the retracted position. The proximity position is a position that is close to and faces the main shaft 9. The retreat position is a position away from the main shaft 9 forward.

  The grip arm 90 holds the steel ball 92 at the other end opposite to the grip portion 91 in a state where the steel ball 92 is urged outward by a compression coil spring (not shown). The boss portion 73 extrapolates a cylindrical grip support collar 80 around which a guide surface 83 having an arcuate cross section is provided. A part of the steel ball 92 protruding and retracting from the other end of the grip arm 90 elastically contacts the guide surface 83 of the grip support collar 80. The guide surface 83 guides the other end side of the grip arm 90. Therefore, the grip arm 90 can swing stably.

  The guide surface 83 includes a first notch groove 98 and a second notch groove 99. The first notch groove 98 is provided on the front side of the magazine base 71 in the guide surface 83. The second notch groove 99 is provided on the guide head 83 on the spindle head 7 side. When the steel ball 92 is fitted in the first notch groove 98, the grip arm 90 maintains the posture in a state where the grip 91 is moved to the close position. When the steel ball 92 is fitted in the second notch groove 99, the grip arm 90 maintains the posture in a state where the grip portion 91 is moved to the retracted position.

  With reference to FIG. 3, the electrical configuration of the numerical controller 30 and the machine tool 1 will be described. The numerical control device 30 includes a CPU 31, a ROM 32, a RAM 33, a nonvolatile storage device 34, an input / output unit 35, drive circuits 51A to 55A, and the like. The CPU 31 performs overall control of the numerical control device 30. The ROM 32 stores a control program, a tool change program, and the like. The control program analyzes and executes the NC program. The tool change program executes a tool change process (see FIG. 5) described later. The RAM 33 temporarily stores various data during execution of various processes. The non-volatile storage device 34 stores a plurality of NC programs and the like registered by the operator through the input unit 24. The NC program is composed of a plurality of blocks including various control commands, and controls various operations including axis movement of the machine tool 1, tool change, and the like in units of blocks.

  The drive circuit 51A is connected to the Z-axis motor 51 and the encoder 51B. The drive circuit 52A is connected to the spindle motor 52 and the encoder 52B. The drive circuit 53A is connected to the X-axis motor 53 and the encoder 53B. The drive circuit 54A is connected to the Y-axis motor 54 and the encoder 54B. The drive circuit 55A is connected to the magazine motor 55 and the encoder 55B. The drive circuits 51A to 55A receive commands from the CPU 31 and output drive currents to the corresponding motors 51 to 55, respectively. The drive circuits 51A to 55A receive feedback signals from the encoders 51B to 55B and perform position and speed feedback control. The feedback signal is a pulse signal. The input / output unit 35 is connected to the input unit 24 and the display unit 25, respectively.

  The user can select one NC program from among a plurality of NC programs with the input unit 24. The CPU 31 displays the selected NC program on the display unit 25. The CPU 31 controls the operation of the machine tool 1 based on the NC program displayed on the display unit 25.

  The outline of the position control of the magazine motor 55 by the CPU 31 and the drive circuit 55A will be described with reference to FIG. The drive circuit 55A includes a subtracter 100, a speed converter 101, a subtractor 102, an accumulator 103, an adder 104, a proportional controller 105, a speed converter 106, and a position converter 107. The CPU 31 determines a target position around the axis of the magazine motor 55. The target position is set to a specific position of the magazine motor 55 at which the next tool becomes the tool change position when changing the tool. The next tool is a tool designated by the control command of the NC program. The target position set by the CPU 31 and the detected position of the magazine motor 55 output by the position conversion unit 107 are input to the subtracter 100. The subtracter 100 calculates the target position-detected position, and gives a difference value as a calculation result to the speed conversion unit 101.

  The speed conversion unit 101 converts the difference value into a speed and outputs the speed to the subtracter 102 as a target speed. The CPU 31 periodically gives a command to the magazine motor 55 to control the rotational position. The speed conversion unit 101 calculates and outputs a target speed in the current period based on the difference value and the period for giving the command.

  The encoder 55B outputs a signal corresponding to the position of the magazine motor 55 around the axis. The input signal of the encoder 55B is input to the speed conversion unit 106 and the position conversion unit 107. The speed converter 106 converts the input signal from the encoder 55B into the speed of the magazine motor 55. The target speed output from the speed converter 101 and the detected speed output from the speed converter 106 are input to the subtractor 102. The position converter 107 converts the input signal from the encoder 55B into the position of the magazine motor 55. The detection position output from the position conversion unit 107 is input to the subtracter 100. The subtractor 102 calculates target speed-detected speed and outputs a difference as a calculation result. The difference calculated by the subtracter 102 is a value corresponding to the difference between the target position of the magazine motor 55 and the current position.

  The difference output from the subtracter 102 is given to the accumulator 103 and the adder 104. The accumulating unit 103 calculates the accumulated value by repeatedly adding the difference between the target speed and the detected speed calculated by the subtracter 102, and gives the calculated accumulated value to the adder 104. In the position control of the magazine motor 55, the CPU 31 performs switching control as to whether or not to use the accumulated value calculated by the accumulating unit 103. The control for inputting the accumulated value calculated by the accumulating unit 103 to the adder 104 is the first control. Control that does not input the accumulated value calculated by the accumulating unit 103 to the adder 104 is second control. When switching to the second control, the accumulating unit 103 initializes the accumulated value to zero. The CPU 31 switches between the first control and the second control according to the state of the machine tool 1.

  When the control is switched to the first control, the adder 104 adds the difference calculated by the subtracter 102 and the accumulated value calculated by the accumulating unit 103, and gives the total value to the proportional control unit 105 as a speed command. When switching to the second control, the adder 104 gives only the difference calculated by the subtractor 102 to the proportional control unit 105 as a speed command. The proportional control unit 105 calculates a torque proportional to the speed based on the speed command, and outputs the calculated torque to the magazine motor 55 as a torque command. The magazine motor 55 rotates to a specific position around the axis based on the torque command. The magazine motor 55 rotates the tool magazine 21 via the speed reducer 41 and conveys the next tool to the tool change position. As described above, the CPU 31 and the drive circuit 55A perform feedback control of the magazine motor 55.

  A tool change process executed by the CPU 31 will be described with reference to FIGS. In the following description, the Z-axis mechanical origin is referred to as the Z-axis origin. The machine origin is a position where the X-axis and Y-axis machine coordinates are zero, and the Z-axis machine coordinate is a position at which the workpiece can be machined. In this embodiment, for convenience of explanation, Z180 is a machining position, Z480 is a Z-axis origin, and Z615 is an ATC origin. An area on the table 10 side from the Z-axis origin is a machining area, and an area on the opposite side to the machining area from the Z-axis origin is a tool change area. The machining area is an area for performing a workpiece machining operation. The tool change area is an area for performing tool change by the tool changer 20.

  In the present embodiment, Z510 is set as a predetermined position. The predetermined position is that when the spindle head 7 is lowered from the ATC origin, the taper mounting portion 17A of the tool holder 17 enters the taper hole 18 of the main shaft 9, and the taper mounting portion 17A is inserted into the inner peripheral surface of the taper hole 18. The position immediately before the outer peripheral surface comes into contact. The arrows in FIG. 6 indicate the movement of the spindle head 7. The Z axis uses the upper surface of the table 10 as a reference (zero). Z490 indicates a position 490 mm higher than the upper surface of the table 10, and other numerical values after Z such as Z180 and Z480 indicate the height from the upper surface of the table. FIG. 5 starts when a tool change command in the NC program is executed.

  When the machine tool 1 is started, the CPU 31 switches the position control of the magazine motor 55 to the first control and performs origin detection. The CPU 31 executes an NC program for each block as a control program, and performs cutting of a workpiece fixed on the table 10. When the control command for instructing the tool change is read, the CPU 31 reads the tool change program from the ROM 32 and executes the tool change process. The tool change process executes a tool change operation. The tool change operation is executed in the order of an ascending process, a magazine rotating process, and a descending process.

[Rising process]
The CPU 31 starts the movement of the spindle head 7 to the Z-axis origin and executes the orientation operation of the spindle 9 (S1). The orientation operation is an operation for stopping the rotation angle position of the main shaft 9 at a position where the tool is changed. The CPU 31 rotates the Z axis motor 51. The CPU 31 starts to raise the spindle head 7 from Z180, which is the machining position. The CPU 31 determines whether or not the movement to the Z-axis origin (Z480) has been completed (S2). Until the movement to the Z-axis origin is completed (S2: NO), the CPU 31 returns to S2 and continues to raise the spindle head 7.

  When the movement to the Z-axis origin is completed (S2: YES), the CPU 31 subsequently starts moving the spindle head 7 to the ATC origin (S3). While the spindle head 7 is raised from the Z-axis origin to the ATC origin, the plate cam body 66 abuts against the cam follower 67 as shown in FIG. As shown in the order of FIGS. 7 to 8, the cam follower 93 slides on the inclined surface of the cam body 11 fixed to the front surface of the spindle head 7 downward from the upper part as the spindle head 7 rises. The grip arm 90 swings around the pivot shaft 85. The grip portion 91 of the grip arm 90 that has been indexed to the tool change position that is the lowest position of the magazine base 71 moves to a position close to the spindle 9. The grip portion 91 grips the tool holder 17 attached to the main shaft 9.

  On the other hand, as shown in the order of FIGS. 7 to 8, the plate cam body 66 contacts the cam follower 67 and slides upward. The crank lever 60 swings along the cam shape of the plate cam body 66. The crank lever 60 rotates counterclockwise about the support shaft 61 when viewed from the right side. The lateral lever 62 engages with the pin 58 and presses the draw bar 81 downward. The draw bar 81 urges the holder holding member 19 downward. The holder clamping member 19 releases the pull stud 17B. The tool holder 17 can be removed from the tapered hole 18 of the main shaft 9. As shown in FIG. 9, the spindle head 7 is further raised. The grip portion 91 of the grip arm 90 pulls out the tool holder 17 from the tapered hole 18 of the main shaft 9. The spindle head 7 is further raised toward the ATC origin.

  The CPU 31 determines whether or not the spindle head 7 has been moved to the ATC origin (Z615) (S4). Until the movement to the ATC origin is completed (S4: NO), the CPU 31 returns to S4 and continues raising the spindle head 7.

[Magazine rotation process]
When the movement to the ATC origin is completed (S4: YES), since the ascending process of the spindle head 7 is completed, the CPU 31 controls the position of the magazine motor 55 and continues until the next tool is indexed to the tool change position. Is rotated (S5). As described above, the position control of the magazine motor 55 is performed by the first control using the accumulated value of the accumulating unit 103. Therefore, the rotation until the next tool of the tool magazine 21 is indexed to the tool change position can be increased in speed and accuracy. The CPU 31 determines whether or not the rotation of the tool magazine 21 is completed (S6). Until the rotation of the tool magazine 21 is completed (S6: NO), the CPU 31 returns to S6 and continues to rotate the tool magazine 21.

[Descent process]
When the rotation of the tool magazine 21 is completed (S6: YES), the CPU 31 starts moving the spindle head 7 that stops at the ATC origin to the Z-axis origin (Z480) (S7). The spindle head 7 descends from Z615. In this section, as shown in FIG. 9, the plate cam body 66 slides downward with respect to the cam follower 67, but the crank lever 60 does not swing.

  The CPU 31 determines whether or not the spindle head 7 has reached a predetermined position (S14). As shown in FIG. 9, when the spindle head 7 reaches a predetermined position, the taper mounting portion 17 </ b> A of the tool holder 17 enters the tapered hole 18 of the spindle 9, and the taper is formed on the inner peripheral surface of the tapered hole 18. This is a state immediately before the outer peripheral surface of the mounting portion 17A comes into contact. Until the spindle head 7 reaches a predetermined position (S8: NO), the CPU 31 returns to S8 and continues to lower the spindle head 7. When the spindle head 7 reaches a predetermined position (S8: YES), the CPU 31 switches the position control of the magazine motor 55 from the first control to the second control (S9).

  At the time of tool change, the position of the taper mounting portion 17A of the tool holder 17 that rotates the tool magazine 21 and transports it to the tool change position with respect to the taper hole 18 of the main shaft 9 may shift. When the taper mounting portion 17A enters the taper hole 18 in a state where there is a deviation, the inner peripheral surface of the taper hole 18 and the outer peripheral surface of the taper mounting portion 17A interfere with each other. Therefore, as described above, the CPU 31 switches the position control of the magazine motor 55 to the second control immediately before the inner peripheral surface of the tapered hole 18 and the outer peripheral surface of the taper mounting portion 17A abut.

  In the second control, since the accumulated value calculated by the accumulating unit 103 is not input to the adder 104, the torque command torque output from the proportional control unit 105 to the magazine motor 55 is lower than the conveyance torque. The conveyance torque is a torque command torque output by the proportional control unit 105 when the tool magazine 21 is rotated in the first control to convey the next tool. Therefore, the tool magazine 21 can be rotated against the torque of the speed reducer 41 according to the external bias. The outer peripheral surface of the taper mounting portion 17A slides along the inner peripheral surface of the tapered hole 18. The tool magazine 21 is urged by the taper mounting portion 17A and rotates in a direction to correct the positional deviation. Therefore, the tool magazine 21 can align the position of the tool holder 17 with respect to the tapered hole 18. The tapered mounting portion 17A is normally mounted in the tapered hole 18.

  As described above, when the torque applied from the magazine motor 55 to the speed reducer 41 decreases, when the reverse torque is applied from the tool magazine 21 to the speed reducer 41, the speed reducer 41 follows the reverse torque. Hold. Therefore, the machine tool 1 can reduce the load applied to the speed reducer 41. Furthermore, since the position of the taper mounting portion 17A is aligned with the position of the taper hole 18, the machine tool 1 can reduce the load applied to the main shaft 9. Furthermore, since the tool magazine 21 rotates in the direction for correcting the positional deviation, the machine tool 1 can reduce the load applied to the grip arm 90 of the tool magazine 21.

  After the taper mounting portion 17A is mounted to the taper hole 18, the grip portion 91 of the grip arm 90 moves to the retracted position, and the spindle head 7 continues to descend toward the Z-axis origin (Z480). The CPU 31 determines whether or not the spindle head 7 has passed the Z-axis origin (S10). Until the spindle head 7 reaches the Z-axis origin (S10: NO), the CPU 31 returns to S10 and continues to descend the spindle head 7. When the spindle head 7 reaches the Z-axis origin (S10: YES), the taper mounting portion 17A is securely mounted in the taper hole 18. The CPU 31 switches the position control of the magazine motor 55 to the first control again (S11). In the first control, the accumulated value calculated by the accumulating unit 103 is input to the adder 104, so that the torque command torque output from the proportional control unit 105 to the magazine motor 55 increases. Therefore, the tool magazine 21 can stably hold its own position without rotating even if there is an external bias. The CPU 31 ends the tool change process.

  In the above description, the tool magazine 21 corresponds to the storage portion of the present invention, the speed reducer 41 corresponds to the transport mechanism of the present invention, the magazine motor 55 corresponds to the transport motor of the present invention, the spindle head 7 and the grip arm. 90 corresponds to the mounting means of the present invention, the CPU 31 corresponds to the torque control means of the present invention, the CPU 31 that executes the process of S9 corresponds to the torque reducing means of the present invention, and the CPU 31 that executes the process of S11 This corresponds to the torque return means of the invention. The tool change position corresponds to a predetermined position of the present invention.

  As described above, the machine tool 1 according to the present embodiment can change the tool 4 of the tool 4 mounted on the spindle 9 by the tool changing device 20. The tool changer 20 includes a tool magazine 21, a reducer 41, a magazine motor 55, and the like. The tool magazine 21 can rotate around one axis. The reducer 41 rotates the tool magazine 21 by reducing the rotation speed of the magazine motor 55 with a plurality of gears or the like. The machine tool 1 controls the position of the magazine motor 55, controls the rotational position of the tool magazine 21 via the speed reducer 41, and determines the next tool specified by the NC program as the tool change position. The machine tool 1 performs feedback control of the magazine motor 55 based on the difference between the specific position specified by the control command of the NC program and the current position. In the feedback control, a cumulative value of the difference between the specific position and the current position is calculated, and switching between the first control considering the cumulative value and the second control not considering the cumulative value is performed.

  The tool change process is performed in the order of an ascending process, a magazine rotating process, and a descending process. The ascending step is a step in which the spindle head 7 is raised and the tool 4 attached to the spindle 9 is removed while the grip arm 90 of the tool magazine 21 holds the tool 4 attached to the spindle 9. The magazine rotation process is a process of rotating the tool magazine 21 and indexing the next tool to the tool change position. The descending step is a step of lowering the spindle head 7 from the ATC origin and attaching the tapered hole 18 of the spindle 9 to the next tool indexed to the tool change position.

  The machine tool 1 performs the tool change process by the first control in principle. In the magazine rotation process, the taper mounting portion 17A of the tool holder 17 may be displaced from the position of the taper hole 18 of the main shaft 9 in some cases. Therefore, in the lowering process, the machine tool 1 immediately before the taper mounting portion 17A of the tool holder 17 enters the taper hole 18 of the spindle 9 and the outer peripheral surface of the taper mounting portion 17A contacts the inner peripheral surface of the taper hole 18. The position control of the magazine motor 55 is switched from the first control to the second control. The torque that the magazine motor 55 applies to the speed reducer 41 is lower than the conveyance torque when the rotation of the tool magazine 21 is indexed in the first control. The tool magazine 21 becomes rotatable by external bias. The outer peripheral surface of the taper mounting portion 17A slides along the inner peripheral surface of the tapered hole 18. The tool magazine 21 rotates in a direction for correcting the positional deviation. The tool magazine 21 can move the position of the tool holder 17 with respect to the tapered hole 18. The taper mounting portion 17 </ b> A of the tool holder 17 is mounted without difficulty in the taper hole 18 of the main shaft 9.

  Therefore, the machine tool 1 can reduce the load applied to the speed reducer 41. Since the machine tool 1 can reduce the impact applied to the spindle 9, the tool magazine 21, and the speed reducer 41 when the tool 4 is mounted on the spindle 9, failure of each part can be prevented. Since the machine tool 1 can satisfactorily attach the tool 4 to the spindle 9 even with the conventional positioning accuracy of the speed reducer 41, the cost for improving the positioning accuracy of the speed reducer 41 can be reduced.

  Further, in the above-described embodiment, since the torque is lower than the conveying torque immediately before the tool 4 is mounted on the main shaft 9, the conveying torque is applied to the reduction gear 41 until immediately before the tool at a predetermined position is mounted on the main shaft 9. Has been. Therefore, the machine tool 1 can prevent the tool magazine 21 from unstablely moving due to an external impact until immediately before the tool is mounted on the spindle 9.

  Further, in the above-described embodiment, the torque lowered when the tool 4 is mounted on the main shaft 9 returns at the Z-axis origin. After the movement to the Z-axis origin, a conveyance torque is applied to the speed reducer 41, so that it is possible to prevent the tool magazine 21 from being unstablely moved by an external impact.

  The present invention is not limited to the above embodiment, and various modifications can be made. In the above embodiment, the position control of the magazine motor 55 is turned off when the spindle head 7 reaches a predetermined position in the descending step. However, since the spindle head 7 starts moving from the ATC origin to the Z-axis origin, The position control of the magazine motor 55 may be turned off immediately before the taper mounting portion 17A of the tool holder 17 is mounted in the taper hole 18.

  In the above embodiment, when the spindle head 7 reaches a predetermined position in the descending step, the position control of the magazine motor 55 is switched to the second control. The position control of the magazine motor 55 may be switched to the second control when the torque detected by the torque sensor is equal to or greater than a predetermined value.

  A modified example of the tool change process using the torque sensor will be described with reference to the flowchart of FIG. The modified example is different from the flowchart shown in FIG. 5, but the other processes are common, so that the different processes will be mainly described. The CPU 31 starts rotating the tool magazine 21 (S5), and after the rotation is completed (S6: YES), starts to move the spindle head 7 to the Z-axis origin (S7). CPU31 judges whether the torque concerning the reduction gear 41 which the torque sensor detected is more than predetermined value (S20). When the position of the taper mounting portion 17A of the tool holder 17 is shifted from the position of the taper hole 18 of the main shaft 9, the outer peripheral surface of the taper mounting portion 17A interferes with the inner peripheral surface of the taper hole 18. In addition to the torque due to the position control of the magazine motor 55, torque caused by the positional deviation between the tapered hole 18 and the taper mounting portion 17 </ b> A is further applied to the speed reducer 41, so that a torque greater than a predetermined value is applied.

  When the torque detected by the torque sensor is less than the predetermined value (S20: NO), there is no interference due to the positional deviation between the tapered hole 18 and the tapered mounting portion 17A. Until the spindle head 7 passes the Z-axis origin (S10: NO), the CPU 31 returns to S20 and monitors the torque detected by the torque sensor.

  On the other hand, when the torque detected by the torque sensor is equal to or greater than the predetermined value (S20: YES), since excessive torque is applied to the speed reducer 41, a displacement occurs between the taper hole 18 and the taper mounting portion 17A. There is a high possibility. Therefore, the CPU 31 switches the position control of the magazine motor 55 to the second control (S9). Similar to the above embodiment, the torque applied to the reduction gear 41 by the magazine motor 55 decreases. The tool magazine 21 becomes rotatable by external bias. The outer peripheral surface of the taper mounting portion 17A slides along the inner peripheral surface of the tapered hole 18. The tool magazine 21 rotates in a direction for correcting the positional deviation. The tool magazine 21 can move the position of the tool holder 17 with respect to the tapered hole 18. Therefore, also in this modified example, the taper mounting portion 17A of the tool holder 17 is mounted without difficulty to the taper hole 18 of the main shaft 9.

  When the spindle head 7 passes the Z-axis origin (S10: YES), the CPU 31 determines whether the position control of the magazine motor 55 is the second control (S21). When the position control of the magazine motor 55 is the first control (S21: NO), the process proceeds to S12. When the position control of the magazine motor 55 is the second control (S21: YES), the CPU 31 switches the position control of the magazine motor 55 to the first control again (S11). Therefore, the tool magazine 21 can hold its own position without rotating even if there is an external bias. Thereafter, the CPU 31 executes the same processing as in the above embodiment. Also according to this modification, the machine tool 1 can obtain the same effects as those of the above embodiment. Note that the CPU 31 that executes the process of S20 in FIG. 11 corresponds to a determination unit of the present invention.

  In the above embodiment, the tool is conveyed to the tool change position by the rotation indexing operation of the tool magazine 21, and the tool at the tool change position is moved to the main spindle 9 by the lifting / lowering operation of the spindle head 7 and the swinging operation of the grip arm 90. It is to be attached to. For example, by transporting the tool to a predetermined position with a transport mechanism provided inside the tool magazine for storing the tool, gripping the tool transported to the predetermined position and the tool attached to the spindle, and turning itself, The present invention is also applicable to machine tools that can interchange these tools.

  In the above embodiment, the position control of the magazine motor 55 is switched from the first control to the second control, and the result obtained by subtracting the accumulated value calculated by the accumulating unit 103 from the torque command output by the proportional control unit 105 is obtained. Although the torque command torque output to the magazine motor 55 is reduced, for example, the torque command output by the proportional control unit 105 may be directly changed to be forcibly reduced to a predetermined level.

  In the control using the gain coefficient in the speed conversion unit 101, the torque command value can be changed by changing the gain coefficient.

DESCRIPTION OF SYMBOLS 1 Machine tool 4 Tool 7 Spindle head 9 Spindle 17 Tool holder 17A Taper mounting part 18 Taper hole 20 Tool changer 21 Tool magazine 31 CPU
41 Reducer 55 Magazine motor 55A Drive circuit 90 Grip arm

Claims (5)

A spindle for processing a workpiece by mounting a tool, a storage unit for storing the tool to be mounted on the spindle, a transfer mechanism for transferring the tool stored in the storage unit to a predetermined position, and driving the transfer mechanism In a machine tool comprising: a conveyance motor; torque control means for controlling torque applied to the conveyance mechanism of the conveyance motor; and mounting means for mounting the tool, which has been conveyed to the predetermined position by the conveyance mechanism, to the main shaft. ,
The torque control means includes
A machine tool, comprising: a torque lowering means for lowering the torque at least when the tool is transported to the transport mechanism after the tool is transported to the predetermined position by the transport mechanism. The torque reducing means is
The torque is lowered below the transport torque immediately after the tool is transported to the predetermined position by the transport mechanism and immediately before the mounting unit transports the tool to the predetermined position. Item 1. The machine tool according to Item 1. The storage portion is a tool magazine comprising a disc-shaped main body that can rotate around a single axis, and a plurality of grip arms that are provided on the outer periphery of the main body and hold the tool,
The transport mechanism reduces the rotational speed of the transport motor, rotates the tool magazine in the circumferential direction, and positions the tool held by one grip arm of the plurality of grip arms at the predetermined position. Because
The main shaft is stored in the storage unit in a machining area in which the machining operation is performed on the workpiece on the workpiece side with respect to the original position in the axial direction of the spindle, and an area on the opposite side of the machining area from the origin position. It is possible to move between tool change areas for performing tool change with the tool,
The mounting means mounts the tool on the spindle by moving the spindle toward the tool transported to the predetermined position by the transport mechanism in the tool change region. The machine tool according to 1 or 2. The torque control means includes
The torque reduction means comprises torque return means for returning the torque to at least the conveyance torque when the torque reduction means moves from the tool change area to the origin position after lowering the torque below the conveyance torque. The machine tool according to claim 3. Torque detecting means for detecting torque applied to the transport mechanism;
Determination means for determining whether the torque detected by the torque detection means is equal to or greater than a predetermined value after the tool is conveyed to the predetermined position by the conveyance mechanism;
The torque reducing means is
2. The machine tool according to claim 1, wherein when the determination unit determines that the torque is equal to or greater than the predetermined value, the torque is lowered at least below the conveyance torque.

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