Tailstock unit and machine tool

Abstract

To provide a tailstock unit that prevents falling-off of a center unit used for a workpiece tail stop in a machine tool during conveyance for automatic exchanging, and the machine tool using the same.SOLUTION: A tailstock unit 50 comprises: a center unit 51 including a center pin 70 which extends about a prescribed axis 160 and used for a workpiece tailstock in a machine tool; and a conveyance body 56 detachably connected to the center unit 51 and conveyed together with the center unit 51. The center unit 51 is provided with a groove 80. The conveyance body 56 includes a projected part 90 engaged with the groove 80 so as to be restricted in the movement in the axial direction of the axis 160 and the peripheral direction of the axis 160 when the center unit 51 and the conveyance body 56 are connected.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This invention relates to a centering unit and a machine tool.

Background Art

[0002] For example, Japanese Patent Application Laid-Open No. 2018-69423 (Patent Document 1) discloses a center device including a rotating center detachably attached to a chuck for gripping a workpiece and a center changer connected to a tool holder and capable of coupling and separating the rotating center with respect to the tool holder. The tool holder is transported between a chuck and a tool magazine together with the rotating center by a tool changing device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As disclosed in the above Patent Document 1, a center device (centering unit) in which a rotating center (center unit) used for centering a workpiece in a machine tool is automatically replaceable is known. However, in the center device in Patent Document 1, when the rotating center is transported by the tool changing device, inertial forces such as excessive centrifugal force may act on the rotating center, or vibration may be applied. In this case, if the rotating center is not sufficiently held by the center changer, the rotating center may fall off.

[0005] An object of this invention is to provide a centering unit that prevents a center unit used for centering a workpiece in a machine tool from falling off during transportation for automatic replacement, and a machine tool using such a centering unit.

Means for Solving the Problem

[0006] The center-pressing unit according to this invention has a center pin extending around a predetermined axis, and includes a center unit used for center-pressing a workpiece in a machine tool, and a carrier detachably connected to the center unit and transported together with the center unit. A groove portion is provided on either one of the center unit and the carrier. The other of the center unit and the carrier has a convex portion that is engaged so that movement in the axial direction of the predetermined axis and in the circumferential direction of the predetermined axis with respect to the groove portion is restricted when the center unit and the carrier are connected.

[0007] The machine tool according to this invention includes the above-described center-pressing unit, a center unit holding portion that detachably holds the center unit, and a conveying device that detachably holds the carrier and conveys the carrier together with the center unit.

Advantages of the Invention

[0008] According to this invention, it is possible to provide a center-pressing unit that prevents a center unit used for center-pressing a workpiece in a machine tool from falling off during conveyance for automatic exchange, and a machine tool using such a center-pressing unit.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Embodiments for Carrying Out the Invention

[0010] Embodiments of this invention will be described with reference to the drawings. In the drawings referred to below, the same or corresponding members are given the same numbers.

[0011] FIG. 1 is a front view showing a machine tool in an embodiment of this invention. In FIG. 1, the inside of the machine tool is shown by seeing through the cover body forming the appearance of the machine tool.

[0012] Referring to FIG. 1, the machine tool 100 is a composite machine tool equipped with both a milling function for performing work machining by bringing a rotating tool into contact with a stationary work, and a turning function for performing work machining by bringing a tool into contact with a rotating work.

[0013] The machine tool 100 is an NC (Numerically Controlled) machine tool in which various operations for workpiece machining are automated by numerical control by a computer.

[0014] In this specification, for the sake of convenience in explaining the configuration of the machine tool 100, an axis parallel to the rotation axis of the workpiece and extending in the horizontal direction is referred to as the "Z-axis", an axis orthogonal to the Z-axis and extending in the horizontal direction is referred to as the "Y-axis", and an axis extending in the vertical direction is referred to as the "X-axis". The right direction in FIG. 1 is referred to as the "+Z-axis direction", and the left direction is referred to as the "-Z-axis direction". The front direction of the paper surface in FIG. 1 is referred to as the "+Y-axis direction", and the back direction is referred to as the "-Y-axis direction". The upward direction is referred to as the "+X-axis direction", and the downward direction is referred to as the "-X-axis direction".

[0015] The machine tool 100 includes a bed 16, a workpiece spindle 21, an opposed workpiece spindle 26, a tool spindle 41, and a tool rest 30. The workpiece spindle 21, the opposed workpiece spindle 26, the tool spindle 41, and the tool rest 30 are arranged in a working area 210. The working area 210 is a space where workpiece machining is performed, and is sealed by a cover body (not shown) so that foreign matters such as chips or cutting oil accompanying workpiece machining do not leak outside the working area 210.

[0016] The bed 16 is a base member for supporting the workpiece spindle 21, the opposed workpiece spindle 26, the tool spindle 41, the tool rest 30, etc., and is installed on the floor surface of a factory or the like. The bed 16 is made of metal such as a casting.

[0017] The workpiece spindle 21 and the opposed workpiece spindle 26 can hold a workpiece. The workpiece spindle 21 is rotationally driven (C-axis rotation) by a motor about a rotation center axis 110 parallel to the Z-axis. A chuck 22 that operates by hydraulic pressure or the like and detachably holds the workpiece is provided on the workpiece spindle 21.

[0018] The opposed work spindle 26 is arranged to face the work spindle 21 in the Z-axis direction. The opposed work spindle 26 is rotationally driven by a motor about a rotation center axis 120 that is parallel to the Z-axis and extends in a straight line with the rotation center axis 110. The opposed work spindle 26 is provided with a chuck 27 that operates by hydraulic pressure or the like and detachably holds the work.

[0019] The work spindle 21 is fixed to the bed 16. The opposed work spindle 26 is movable in the Z-axis direction by various feed mechanisms, guide mechanisms, and motors.

[0020] The tool spindle 41 can hold a tool. The tool spindle 41 is rotationally driven by a motor about a rotation center axis 140 that is parallel to the X-axis in a reference posture described later. The tool spindle 41 incorporates a clamp mechanism (not shown) for detachably holding the tool.

[0021] The tool spindle 41 is further pivotable about a pivot center axis 150 parallel to the Y-axis (B-axis pivot). The pivot center axis 150 intersects the rotation center axis 140. The pivot range of the tool spindle 41 is, for example, in the range of ±120° with reference to a reference posture in which the spindle end face 42 of the tool spindle 41 faces downward (the posture of the tool spindle 41 shown in FIG. 1).

[0022] The tool spindle 41 is movable in the X-axis direction, Y-axis direction, and Z-axis direction by various feed mechanisms, guide mechanisms, and motors. Although not shown in FIG. 1, around the work spindle 21, an automatic tool changer (ATC: Automatic Tool Changer) for automatically exchanging the tool held by the tool spindle 41 and a tool magazine for accommodating the replacement tool are provided.

[0023] The tool rest 30 can hold a tool. In FIG. 1, the tool rest 30 with a vibration damping device 31 attached for preventing the vibration of the work is shown. The tool rest 30 is movable in the X-axis direction and Z-axis direction by various feed mechanisms, guide mechanisms, and motors.

[0024] The machine tool 100 further has a center unit 51 (51A, 51B). The center unit 51 is used for centering the workpiece in the machine tool 100. The center unit 51 is held by the workpiece spindle 21 or the opposing workpiece spindle 26. The center unit 51 has a center pin 70 (see FIG. 3 to be described later) extending on the axes of the rotation center axes 110, 120, and supports the end face of the workpiece by the center pin 70.

[0025] In FIG. 1, as an example of workpiece machining using the center unit 51, a state of workpiece machining in which both end faces of the workpiece W are centered using the center unit 51A and the center unit 51B is shown.

[0026] The center unit 51A is held by the workpiece spindle 21. The center unit 51A is called a workpiece driving center or a face driver, and can transmit the rotation from the workpiece spindle 21 to the workpiece. The center unit 51A supports the end face of the workpiece W on the axis of the rotation center axis 110 by the center pin 70, and grasps the end face of the workpiece W by a drive key 68 (see FIG. 3 to be described later).

[0027] The center unit 51B is held by the opposing workpiece spindle 26. The center unit 51B supports the end face of the workpiece W on the axis of the rotation center axis 120 by the center pin 70.

[0028] In such a configuration, while rotating the workpiece W centered by the center unit 51A and the center unit 51B at both ends in the Z-axis direction about the rotation center axes 110, 120, the turning process of the workpiece W is performed by bringing the tool T held by the tool spindle 41 into contact with the workpiece W.

[0029] A tool magazine (not shown) houses a replacement center unit 51 together with various tools. The center unit 51 is automatically exchanged between the tool magazine and the work spindle 21 or the opposing work spindle 26 by using the tool spindle 41 as a transport device for transporting the center unit 51. Subsequently, the structure of the centering unit 50 in the present embodiment will be described.

[0030] FIG. 2 is a diagram showing a centering unit in an embodiment of the present invention. In FIG. 2, typically, a center unit 51A held by the tool spindle 41 is shown.

[0031] FIG. 3 is a diagram showing the center unit in FIG. 2. FIG. 4 is a diagram showing the center holder in FIG. 3. In FIG. 3, a cross-section of the center holder 61 as viewed in the arrow direction on the line III-III in FIG. 4 is shown. FIG. 5 is a diagram showing the center holder as viewed in the direction indicated by the arrow V in FIG. 4.

[0032] Referring to FIGS. 2 to 5, the centering unit 50 in the present embodiment has a center unit 51 and a carrier 56. The carrier 56 is detachably connected to the center unit 51. The carrier 56 is transported together with the center unit 51. When the center unit 51 held by the tool spindle 41 is replaced, the carrier 56 is connected to the center unit 51. The carrier 56 is held by the tool spindle 41 and transported together with the center unit 51.

[0033] As shown in FIGS. 3 and 4, the center unit 51 has a center 66 and a center holder 61.

[0034] Center 66 has a center pin 70. The center pin 70 extends around a predetermined axis 160. The predetermined axis 160 is an imaginary straight line forming the central axis of the center pin 70. The center pin 70 has a pin shape extending on the axis of the predetermined axis 160. When the center unit 51(51A) is held by the work spindle 21, the predetermined axis 160 extends in a straight line with the rotation center axis 110 of the work spindle 21 in the Z-axis direction. The center pin 70 is supported by a center body 67, which will be described later, so as to be able to move forward and backward in the axial direction of the predetermined axis 160.

[0035] Center 66 further has a center body 67 and a plurality of drive keys 68. The center body 67 extends around a predetermined axis 160. The center pin 70 protrudes from the center body 67 in the axial direction of the predetermined axis 160.

[0036] The plurality of drive keys 68 are attached to the center body 67. The plurality of drive keys 68 are arranged on the outer side in the radial direction of the predetermined axis 160 with respect to the center pin 70. The plurality of drive keys 68 are provided at intervals in the circumferential direction of the predetermined axis 160. The drive key 68 has a cutting edge shape and grasps the end face of the work in the circumferential direction of the predetermined axis 160 (rotation center axis 110) by contacting the end face of the work in the axial direction of the predetermined axis 160 (rotation center axis 110).

[0037] Center 66 further has an elastic member 72. The elastic member 72 is built into the center body 67. The elastic member 72 is, for example, a coil spring extending around a predetermined axis 160. The elastic member 72 generates an elastic force for pressing the center pin 70 toward the work. The elastic member 72 acts on the center pin 70 with an elastic force in the axial direction of the predetermined axis 160.

[0038] When the center unit 51 is alone, the protruding length of the center pin 70 from the center body 67 is Ha. The workpiece is provided with a pin insertion hole that is recessed from the workpiece end face and can receive the center pin 70. When the workpiece is centered by the center unit 51, the center pin 70 is inserted into the pin insertion hole. The center pin 70 is retracted into the center body 67 while resisting the elastic force of the elastic member 72 by the workpiece. At this time, the protruding length of the center pin 70 from the center body 67 becomes a value smaller than Ha.

[0039] The center body 67 has a shaft portion 69. The shaft portion 69 extends axially about a predetermined axis 160. The shaft portion 69 has a tapered shape in which the diameter of the shaft portion 69 decreases as it moves away from the center pin 70 in the axial direction of the predetermined axis 160.

[0040] As shown in FIGS. 3 to 5, the center holder 61 has a cylindrical shape centered on a predetermined axis 160 as a whole. The center holder 61 is provided with a shaft insertion hole 76. The shaft insertion hole 76 is a through hole extending about the predetermined axis 160. The shaft insertion hole 76 has a tapered shape capable of receiving the shaft portion 69. By inserting the shaft portion 69 into the shaft insertion hole 76, the center 66 is assembled to the center holder 61.

[0041] The center holder 61 has a shank portion 62 and a holder body 63. The shank portion 62 and the holder body 63 are provided continuously in the axial direction of the predetermined axis 160. The shank portion 62 is a portion that is gripped by the chuck 22 when the center unit 51 is held by the workpiece spindle 21. The holder body 63 is disposed between the center pin 70 and the shank portion 62 in the axial direction of the predetermined axis 160.

[0042] The center holder 61 (holder body 63) has an outer peripheral surface 64, a first holder end face 65, and a second holder end face 77.

[0043] The outer peripheral surface 64 extends in the axial direction of the predetermined axis 160 while having a constant diameter centered on the predetermined axis 160. Each of the first holder end surface 65 and the second holder end surface 77 consists of a plane orthogonal to the predetermined axis 160. The first holder end surface 65 and the second holder end surface 77 respectively constitute the end surfaces of the holder body 63 at one end and the other end in the axial direction of the predetermined axis 160. The outer peripheral edge of the first holder end surface 65 intersects with the outer peripheral surface 64 at a corner. The center body 67 protrudes in the axial direction of the predetermined axis 160 from the first holder end surface 65. The inner peripheral edge of the second holder end surface 77 intersects with the outer peripheral surface of the shank portion 62 at a corner.

[0044] FIG. 6 is a view showing a groove portion provided in the center unit in FIG. 4. In FIG. 6, the outer peripheral surface 64 of the center holder 61 is developed in the vertical direction of the paper surface showing FIG. 6.

[0045] As shown in FIGS. 3 to 6, a groove portion 80 is provided in the center unit 51. The groove portion 80 is provided in the center holder 61 (holder body 63). The groove portion 80 has a groove shape recessed from the outer peripheral surface 64.

[0046] A plurality of groove portions 80 are provided in the center unit 51. The plurality of groove portions 80 are provided at intervals from each other in the circumferential direction of the predetermined axis 160. The plurality of groove portions 80 are provided at equal intervals in the circumferential direction of the predetermined axis 160.

[0047] The groove portion 80 includes a first section portion 81, a second section portion 82, and a third section portion 83. The first section portion 81, the second section portion 82, and the third section portion 83 extend continuously. The second section portion 82 is disposed between the first section portion 81 and the third section portion 83. Each of the groove width B and the groove depth D of the groove portion 80 is constant across the first section portion 81, the second section portion 82, and the third section portion 83. The groove portion 80 is configured to have a groove width B and a groove depth D into which a convex portion 90 described later can be inserted.

[0048] The first section 81 extends in the axial direction of the predetermined axis 160. The first section 81 is open at one end in the axial direction of the predetermined axis 160. The first section 81 is open at the first holder end face 65.

[0049] The second section 82 extends in the circumferential direction of the predetermined axis 160. The second section 82 extends in the circumferential direction of the predetermined axis 160 at a position axially away from the first holder end face 65 with respect to the predetermined axis 160. The second section 82 is connected to the first section 81. The second section 82 is connected to the first section 81 at one end in the circumferential direction of the predetermined axis 160. The second section 82 is connected to the third section 83. The second section 82 is connected to the third section 83 at the other end in the circumferential direction of the predetermined axis 160.

[0050] The third section 83 extends in the axial direction of the predetermined axis 160. The third section 83 has a closed end portion 86. The closed end portion 86 is closed at one end in the axial direction of the predetermined axis 160. The closed end portion 86 is provided at a position surrounded by a groove wall 86a disposed at one end of the third section 83 in the axial direction of the predetermined axis 160, and groove walls 86b and 86c facing each other in the circumferential direction of the predetermined axis 160. The groove wall 86a extends in an arc shape corresponding to the shape of the convex portion 90 described later. The groove wall 86b extends in the axial direction of the predetermined axis 160 from one end of the groove wall 86a that extends in an arc shape. The groove wall 86c extends in the axial direction of the predetermined axis 160 from the other end of the groove wall 86a that extends in an arc shape. The third section 83 is connected to the second section 82 at the other end in the axial direction of the predetermined axis 160.

[0051] The length of the third section 83 in the axial direction of the predetermined axis 160 is smaller than the length of the first section 81 in the axial direction of the predetermined axis 160. The angle θ centered on the predetermined axis 160 between the groove center of the first section 81 and the groove center of the third section 83 is, for example, 45°.

[0052] FIG. 7 is a view showing the carrier in FIG. 2. In FIGS. 2 and 7, the base portion 93 and the extending portion 96 of the carrier 56 are shown by cross-sectional shapes. FIG. 8 is a view showing an enlarged view of the range surrounded by the two-dot chain line VIII in FIG. 7.

[0053] Referring to FIGS. 2, 7 and 8, the carrier 56 has a shank portion 91, a base portion 93, and an extending portion 96. The carrier 56 extends about a predetermined axis 160 in a state of being connected to the center unit 51.

[0054] As shown in FIG. 7, the shank portion 91 is a portion that is gripped by the clamping mechanism of the tool spindle 41 when the carrier 56 is held by the tool spindle 41. The specification of the shank portion 91 is not particularly limited, and for example, it may be CAPTO, BT, or HSK.

[0055] The base portion 93 is connected to the shank portion 91. The base portion 93 is fastened to the shank portion 91 using bolts or the like. The base portion 93 has a disk shape centered on the predetermined axis 160, with the axial direction of the predetermined axis 160 being the thickness direction. The base portion 93 has an end face 94. The end face 94 is composed of a plane orthogonal to the predetermined axis 160.

[0056] A pin insertion hole 95 is provided in the base portion 93. The pin insertion hole 95 is recessed from the end face 94 and has a concave shape capable of receiving the center pin 70. The pin insertion hole 95 is provided on the axis of the predetermined axis 160.

[0057] The extending portion 96 extends in the axial direction of the predetermined axis 160 from the base portion 93. The extending portion 96 extends from the base portion 93 in a direction away from the shank portion 91 in the axial direction of the predetermined axis 160. The extending portion 96 is provided at a position radially outward from the predetermined axis 160. The extending portion 96 has a cylindrical shape centered on the predetermined axis 160. The extending portion 96 is connected to the outer peripheral edge of the end face 94 at one end of the predetermined axis 160. The extending portion 96 has a tip portion 96p. The tip portion 96p is disposed at a position away from the base portion 93 in the axial direction of the predetermined axis 160.

[0058] As shown in FIGS. 7 and 8, the carrier 56 further has a convex portion 90. The convex portion 90 has a convex shape protruding radially inward from the inner peripheral surface 97 of the extension portion 96 toward the predetermined axis 160. The convex portion 90 has a pin shape extending cylindrically about the central axis 170. The central axis 170 is parallel to the radial direction of the predetermined axis 160. An O-ring groove 98 is provided in the convex portion 90. The O-ring groove 98 is recessed from the outer peripheral surface of the convex portion 90 and has a groove shape that circulates about the central axis 170. An O-ring 92 is fitted in the O-ring groove 98.

[0059] The carrier 56 has a plurality of convex portions 90. The plurality of convex portions 90 are provided at intervals in the circumferential direction of the predetermined axis 160. The plurality of convex portions 90 are provided at equal intervals in the circumferential direction of the predetermined axis 160. The plurality of convex portions 90 are respectively provided at angular positions corresponding to the plurality of groove portions 80 in the circumferential direction of the predetermined axis 160.

[0060] Note that a configuration may be adopted in which a plurality of extension portions 96 are provided at intervals in the circumferential direction of the predetermined axis 160, and each extension portion 96 extends in an arm shape in the axial direction of the predetermined axis 160 from the base portion 93 at the angular position where each convex portion 90 is provided.

[0061] FIG. 9 is a view showing the groove portion in FIG. 6 and the convex portion engaged with the groove portion. With reference to FIGS. 2 and 9, the form of the center unit 51 and the carrier 56 connected to each other will be described.

[0062] The center body 67 and the base portion 93 face each other in the axial direction of the predetermined axis 160. The tip portion 96p of the extension portion 96 is disposed on the outer periphery of the center holder 61 (holder body 63). The tip portion 96p faces the outer peripheral surface 64 of the holder body 63.

[0063] The center pin 70 is positioned between the center holder 61 and the base 93 in the axial direction of the predetermined axis 160, and is disposed at a position surrounded by the extending portion 96 from the outer periphery of the predetermined axis 160. A space 220 is formed at a position surrounded by the holder body 63, the base 93, and the extending portion 96. The center pin 70 is disposed in the space 220.

[0064] The carrier 56 (base 93) is in contact with the center pin 70 in the axial direction of the predetermined axis 160. The center pin 70 is inserted into the pin insertion hole 95. The center pin 70 is retracted into the center body 67 by the carrier 56 (base 93) against the elastic force of the elastic member 72. At this time, the protruding length of the center pin 70 from the center body 67 becomes Hb which is smaller than Ha (Hb < Ha).

[0065] The convex portion 90 is engaged with the groove portion 80. The convex portion 90 has a convex shape extending from the tip end portion 96p of the extending portion 96 toward the outer peripheral surface 64 of the holder body 63. The convex portion 90 is engaged with the groove portion 80 so that movement in the axial direction of the predetermined axis 160 and in the circumferential direction of the predetermined axis 160 is restricted.

[0066] More specifically, the convex portion 90 is disposed at the closing end portion 86 in the third section portion 83 (the convex portion 90 disposed at the first position Pa in FIG. 9). The convex portion 90 is in contact with the arc-shaped groove wall 86a in the axial direction and the circumferential direction of the predetermined axis 160. When the center pin 70 is retracted into the center body 67 by the carrier 56, the elastic force from the elastic member 72 is applied to the carrier 56 through the center pin 70. As a result, the convex portion 90 is pressed against the groove wall 86a of the closing end portion 86 in the axial direction of the predetermined axis 160.

[0067] Note that the groove wall 86a may be composed of a plane orthogonal to the predetermined axis 160. In this case, the convex portion 90 is in contact with the groove wall 86a in the axial direction of the predetermined axis 160, and is in contact with the groove walls 86b and 86c in the circumferential direction of the predetermined axis 160.

[0068] Figures 10 to 14 are diagrams showing the process of mounting the center unit to the work spindle.

[0069] Referring to FIGS. 9 and 10, in a tool magazine (not shown), a center unit 51 is accommodated in a state of being connected to a carrier 56. The convex portion 90 is disposed at the closed end portion 86 in the third section portion 83 (the convex portion 90 disposed at the first position Pa in FIG. 9). The center unit 51 accommodated in the tool magazine is carried into the machining area 210 and mounted on the tool spindle 41. More specifically, while gripping the carrier 56 by an automatic tool changer (not shown), the shank portion 91 of the carrier 56 is inserted into the tool spindle 41. The tool spindle 41 holds the carrier 56 by gripping the shank portion 91 with a clamping mechanism built therein.

[0070] The tool spindle 41 is rotated about the turning center axis 150 (B-axis turning), and is appropriately moved in the X-axis direction, Y-axis direction, and Z-axis direction, so that the center unit 51 faces the work spindle 21 in the Z-axis direction. At this time, the rotation center axis 110 of the work spindle 21, the predetermined axis 160 of the center unit 51, and the rotation center axis 140 of the tool spindle 41 extend in a straight line in the Z-axis direction.

[0071] Referring to FIG. 11, the tool spindle 41 is moved in the -Z-axis direction by cutting feed to a position where the second holder end face 77 abuts against the end face of the chuck 22. The shank portion 62 of the center unit 51 is inserted inside the chuck 22.

[0072] Referring to FIGS. 9 and 12, the tool spindle 41 is further moved in the -Z-axis direction. The convex portion 90 moves from the first position Pa through the third section portion 83 to the second position Pb where the third section portion 83 and the second section portion 82 form a corner (the convex portion 90 disposed at the second position Pb in FIG. 9). At this time, the protruding length of the center pin 70 from the center body 67 becomes Hc which is smaller than Hb (Hc < Hb). The chuck 22 grips the shank portion 62 of the center holder 61.

[0073] Referring to FIGS. 9 and 13, the work spindle 21 is rotated about the rotation center axis 110 (C-axis rotation). The convex portion 90 moves from the second position Pb through the second section 82 to the third position Pc where the second section 82 and the first section 81 form a corner (the convex portion 90 disposed at the third position Pc in FIG. 9). At this time, instead of the C-axis rotation of the work spindle 21, the tool spindle 41 may be rotated about the rotation center axis 140.

[0074] Referring to FIGS. 9 and 14, the work spindle 21 is moved in the +Z-axis direction. The convex portion 90 moves from the third position Pc through the first section 81 to the fourth position Pd outside the groove portion 80 (the convex portion 90 disposed at the fourth position Pd in FIG. 9). Thereby, the connection between the carrier 56 and the center unit 51 is released. After that, the tool spindle 41 is retracted to the ATC position, and the carrier 56 is returned to the tool magazine by the automatic tool changer.

[0075] Note that the process of removing the center unit 51 from the work spindle 21 may be performed in the reverse order of the above-described process of attaching the center unit 51 to the work spindle 21. The release of the gripping of the center holder 61 by the chuck 22 may be performed after the convex portion 90 has moved from the third position Pc to the second position Pb by the C-axis rotation of the work spindle 21.

[0076] Summarizing the configurations of the centering unit 50 and the machine tool 100 in the embodiment of the present invention described above, the centering unit 50 in the present embodiment has a center pin 70 extending about a predetermined axis 160, and is used for centering the work in the machine tool 100. It includes a center unit 51 and a carrier 56 that is detachably connected to the center unit 51 and is transported together with the center unit 51. A groove portion 80 is provided in the center unit 51. The carrier 56 has a convex portion 90 that is engaged so that the movement of the center unit 51 and the carrier 56 in the axial direction of the predetermined axis 160 and in the circumferential direction of the predetermined axis 160 is restricted when they are connected.

[0077] Further, the machine tool 100 in the present embodiment includes a center-pressing unit 50, a work spindle 21 (opposing work spindle 26) as a center-unit holding part that detachably holds the center unit 51, and a tool spindle 41 as a conveying device that detachably holds the carrier 56 and conveys the carrier 56 together with the center unit 51.

[0078] According to the center-pressing unit 50 and the machine tool 100 configured as described above, the convex portion 90 is engaged with the groove portion 80 so that movement in the axial direction of the predetermined axis 160 and in the circumferential direction of the predetermined axis 160 is restricted. Thereby, when the carrier 56 is conveyed together with the center unit 51, even if an excessive inertial force acts on the center unit 51 or excessive vibration is applied, it is possible to more reliably prevent the center unit 51 from falling off the carrier 56.

[0079] Particularly in the present embodiment, when the tool spindle 41 rotates about the B axis, a centrifugal force directed outward in the radial direction of the rotation center axis 150 or an inertial force in the circumferential direction of the rotation center axis 150 acts on the center unit 51. Even in this case, the engagement structure of the convex portion 90 and the groove portion 80 can prevent the center unit 51 from falling off the carrier 56.

[0080] Further, the groove portion 80 includes a first section portion 81 that extends in the axial direction of the predetermined axis 160 and opens at one end in the axial direction of the predetermined axis 160, a second section portion 82 that extends in the circumferential direction of the predetermined axis 160 and is connected to the first section portion 81, and a closed end portion 86, and includes a third section portion 83 that extends in the axial direction of the predetermined axis 160, the closed end portion 86 is closed at one end in the axial direction of the predetermined axis 160, and is connected to the second section portion 82 at the other end in the axial direction of the predetermined axis 160. When the center unit 51 and the carrier 56 are provided, the convex portion 90 is disposed at the closed end portion 86.

[0081] According to such a configuration, when the center unit 51 and the carrier 56 are provided, since the convex portion 90 is disposed at the closed end portion 86, the convex portion 90 cannot escape from the groove portion 80 unless it sequentially moves through a third section portion 83 extending in the axial direction of the predetermined axis 160, a second section portion 82 extending in the circumferential direction of the predetermined axis 160, and a first section portion 81 extending in the axial direction of the predetermined axis 160. Thereby, the engaged state of the convex portion 90 and the groove portion 80 can be more reliably maintained.

[0082] Particularly in the present embodiment, the center unit 51 is held by a work spindle 21 that is rotatable about a rotation center axis 110 extending in a straight line with the predetermined axis 160, and the carrier 56 is held by a tool spindle 41 that is movable in the Z-axis direction parallel to the predetermined axis 160. According to such a configuration, when connecting the center unit 51 and the carrier 56 and when releasing the connection, the convex portion 90 can be moved along the groove portion 80 (the first section portion 81, the second section portion 82, and the third section portion 83) by the C-axis rotation of the work spindle 21 and the movement of the tool spindle 41 in the Z-axis direction.

[0083] Further, the center pin 70 is supported so as to be able to advance and retreat in the axial direction of the predetermined axis 160. The center unit 51 further has an elastic member 72 that generates an elastic force for pressing the center pin 70 toward the work. When the center unit 51 and the carrier 56 are connected, the carrier 56 abuts against the center pin 70 and retracts the center pin 70 in the axial direction of the predetermined axis 160, whereby the elastic force from the elastic member 72 is applied to the carrier 56 through the center pin 70, and the convex portion 90 is pressed against the groove wall 86a of the closed end portion 86 in the axial direction of the predetermined axis 160.

[0084] According to such a configuration, by utilizing the elastic force generated by the elastic member 72, the convex portion 90 can be more reliably fixed to the closed end portion 86.

[0085] Further, the center unit 51 further includes a center holder 61 having an outer peripheral surface 64 centered on a predetermined axis 160. The carrier 56 has a base portion 93 and an extension portion 96 provided at a position radially outward from the predetermined axis 160 and extending in the axial direction of the predetermined axis 160 from the base portion 93. When the center unit 51 and the carrier 56 are connected, the center pin 70 is disposed between the center holder 61 and the base portion 93 in the axial direction of the predetermined axis 160 and is surrounded by the extension portion 96 from the outer periphery of the predetermined axis 160. On the outer periphery of the center holder 61, the tip portion 96p of the extension portion 96 is disposed facing the outer peripheral surface 64. The center unit 51 is provided with a groove portion 80 having a groove shape recessed from the outer peripheral surface 64. The carrier 56 has a convex portion 90 having a convex shape directed from the tip portion 96p of the extension portion 96 toward the outer peripheral surface 64.

[0086] According to such a configuration, since the center pin 70 is disposed between the center holder 61 and the base portion 93 in the axial direction of the predetermined axis 160 and is surrounded by the extension portion 96 from the outer periphery of the predetermined axis 160, foreign matter is less likely to adhere to the center pin 70 during conveyance. Further, an engaging structure of the groove portion 80 and the convex portion 90 can be provided by using the outer peripheral surface 64 of the center holder 61 and the tip portion 96p of the extension portion 96, which are in a facing arrangement relationship between the center unit 51 and the carrier 56.

[0087] Further, when the center unit 51 and the carrier 56 are connected, a plurality of sets of engaging structures in which the groove portion 80 and the convex portion 90 are paired are provided at intervals in the circumferential direction of the predetermined axis 160. The plurality of sets of engaging structures and the contact portion of the center pin 70 with respect to the carrier 56 (base portion 93) are separated in the axial direction of the predetermined axis 160. According to such a configuration, since the center unit 51 is supported by the carrier 56 at a single point on the axis of the predetermined axis 160 and a plurality of points on the circumference centered on the predetermined axis 160 at a position axially separated from the single point, it is possible to more reliably prevent the center unit 51 from falling off the carrier 56.

[0088] In the present embodiment, the configuration in which the groove portion 80 is provided in the center unit 51 and the carrier 56 has the convex portion 90 has been described. However, in the present invention, a configuration in which a concave portion is provided in the carrier and the center unit has a convex portion may be employed. Further, in the present invention, the center unit holding portion that can detachably hold the center unit is not limited to the work spindle, and may be, for example, a steady rest or a tool post. Further, in the present invention, the transfer device that transfers the carrier is not limited to the tool spindle, and may be, for example, a mobile robot such as an IMR (Industrial Mobile Robot) or an AMR (Autonomous Mobile Robot), or a tool post ATC device for automatically exchanging the tool mounted on the tool post.

[0089] Further, in the present embodiment, the configuration in which the convex portion 90 is pressed against the groove wall of the groove portion 80 is realized by using the elastic member 72 for pressing the center pin 70 against the work. However, the present invention is not limited thereto. For example, in a steady rest unit in which the center pin is fixed so as not to be able to move forward and backward in the axial direction of a predetermined axis, a biasing means such as an elastic member for biasing the convex portion toward the groove wall of the groove portion may be provided on the carrier, or may be provided separately from the center unit and the carrier.

[0090] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims be included.

Explanation of Reference Numerals

[0091] 16 bed, 21 work spindle, 22, 27 chuck, 26 opposed work spindle, 30 tool rest, 31 vibration damper, 41 tool spindle, 42 spindle end face, 50 center punch unit, 51, 51A, 51B center unit, 56 carrier, 61 center holder, 62, 91 shank portion, 63 holder body, 64 outer peripheral surface, 65 first holder end face, 66 center, 67 center body, 68 drive key, 69 shaft portion, 70 center pin, 72 elastic member, 76 shaft insertion hole, 77 second holder end face, 80 groove portion, 81 first section portion, 82 second section portion, 83 third section portion, 86 closed end portion, 86a, 86b, 86c groove wall, 90 convex portion, 92 O-ring, 93 base portion, 94 end face, 95 pin insertion hole, 96 extension portion, 96p tip portion, 97 inner peripheral surface, 98 O-ring groove, 100 machine tool, 110, 120, 140 rotation center axis, 150 swivel center axis, 160 predetermined axis, 170 center axis, 210 working area, 220 space.

Claims

1. A center unit having a center pin extending around a predetermined axis and used for centering a workpiece in a machine tool, and a carrier detachably connected to the center unit and carried together with the center unit, comprising a groove portion provided in either one of the center unit and the carrier, and a centering unit, wherein the other of the center unit and the carrier has a convex portion that is engaged so that movement in the axial direction of the predetermined axis and in the circumferential direction of the predetermined axis with respect to the groove portion is restricted when the center unit and the carrier are connected.

2. The groove portion includes a first section extending in the axial direction of the predetermined axis and opening at one end in the axial direction of the predetermined axis, a second section extending in the circumferential direction of the predetermined axis and connected to the first section, and a third section having a closed end, extending in the axial direction of the predetermined axis, the closed end being closed at one end in the axial direction of the predetermined axis and connected to the second section at the other end in the axial direction of the predetermined axis, and when the center unit and the carrier are provided, the convex portion is disposed at the closed end, the centering unit according to claim 1.

3. The center pin is supported so as to be able to advance and retreat in the axial direction of the predetermined axis, the center unit further has an elastic member that generates an elastic force for pressing the center pin toward the workpiece, and when the center unit and the carrier are connected, the carrier abuts against the center pin and retracts the center pin in the axial direction of the predetermined axis, whereby the elastic force from the elastic member is applied to the carrier through the center pin, and the convex portion is pressed against the groove wall of the closed end in the axial direction of the predetermined axis, the centering unit according to claim 2.

4. The center unit further has a center holder including an outer peripheral surface centered on the predetermined axis, the carrier has a base portion and an extension portion provided at a position radially outward from the predetermined axis and extending in the axial direction of the predetermined axis from the base portion, and when the center unit and the carrier are connected, the center pin is disposed between the center holder and the base portion in the axial direction of the predetermined axis and surrounded by the extension portion from the outer periphery of the predetermined axis. On the outer periphery of the center holder, the tip of the extending portion is disposed to face the outer peripheral surface. In the center unit, the groove portion having a groove shape recessed from the outer peripheral surface is provided. The pusher unit according to claim 1 or 2, wherein the carrier has the convex portion having a convex shape directed from the tip of the extending portion toward the outer peripheral surface.

5. The pusher unit according to claim 1 or 2, a center unit holding portion that detachably holds the center unit, and a machine tool comprising a conveying device that detachably holds the carrier and conveys the carrier together with the center unit.

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