Machine tool

Abstract

This machine tool comprises: a first workpiece main spindle device that is fixed to a bed and that imparts rotation to a workpiece gripped by a first main spindle chuck; a second workpiece main spindle device that is assembled so as to be capable of moving in a direction parallel to the main spindle with respect to the bed and that imparts rotation to the workpiece being gripped by a second main spindle chuck coaxial with the first main spindle chuck; a turret device that is assembled so as to be capable of moving in a direction parallel to the main spindle with respect to the bed, and which is configured such that a turret tool post to which a tool used for machining the workpiece gripped by the first main spindle chuck and the second main spindle chuck is attached moves in a direction parallel to or orthogonal to a main spindle of each of the first workpiece main spindle device and the second workpiece main spindle device; and a tail stock provided with a retraction mechanism for displacing a freely rotatable center rod which is equipped with a center at both ends and which is brought into contact with the center of rotation of the workpiece from a direction facing each of the first main spindle chuck and the second main spindle chuck, to a position away from the center of rotation.

Description

machine tools

[0001] The present invention relates to a machine tool equipped with a tailstock for a workpiece spindle device.

[0002] In machine tools, when rotating and machining a long shaft workpiece, a tailstock is provided opposite the spindle unit that grips the shaft workpiece to stabilize the rotation. Patent Document 1 below also discloses a machine tool having such a tailstock. In this first conventional example, a first tailstock and a second tailstock are provided back-to-back between the first spindle unit and the second spindle unit. Both the first and second tailstocks are movably attached to their respective guide rails, allowing an operator to adjust the distance from the first spindle unit or the second spindle unit.

[0003] Furthermore, the first and second spindle units are provided with first and second turret units, each with a plurality of turret tools mounted at equal intervals on its turret tool rest. A specific turret tool is then indexed according to the machining content, and machining of the workpiece is performed. For example, when machining a shaft workpiece with the first spindle unit, both ends are supported by the spindle chuck and first tailstock of the first spindle unit. In addition to this first conventional example, Patent Document 2 below discloses a machine tool similarly having a tailstock. In this second conventional example, in addition to opposing first and second spindle units and first and second turrets that cooperate with these spindles to machine the workpiece, both center jigs equivalent to the tailstock are provided on a third turret mounted in one location in a tool station.

[0004] Japanese Patent Laid-Open No. 5-285702 Japanese Patent Laid-Open No. 2003-205401

[0005] However, because the machine tool of the first conventional example is configured such that the first and second tailstocks simply move along guide rails, it is conceivable that the first or second turret device will interfere with the first and second tailstocks when machining workpieces other than shaft workpieces. Avoiding such interference would require expanding the range of movement of the first and second tailstocks, which would result in an increase in the size of the machine tool. This would also impose restrictions such as requiring a smaller turret tool post. Furthermore, although the entire machine body of the second conventional example, in which both center jigs are attached to the third turret, is not disclosed, the configuration requiring a turret to set the center would result in an increase in the size of the machine tool.

[0006] SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a machine tool equipped with a tailstock for a work spindle device.

[0007] In one aspect of the present invention, a machine tool comprises a work spindle device that imparts rotation to a work held by a spindle chuck, a turret device in which a turret tool rest on which tools used to machine the work held by the spindle chuck are attached is configured to move in a direction parallel to or perpendicular to the spindle of the work spindle, and a core stock equipped with a retraction mechanism that displaces a rotatable center rod that abuts against the center of rotation of the work from a direction opposite the spindle chuck to a position away from the center of rotation.

[0008] In another aspect of the present invention, a machine tool comprises: a first work spindle unit fixed to a bed and rotating a workpiece held by a first spindle chuck; a second work spindle unit assembled so as to be movable relative to the bed in a direction parallel to the spindle and rotating a workpiece held by a second spindle chuck coaxial with the first spindle chuck; a turret unit assembled so as to be movable relative to the bed in a direction parallel to the spindle and having a turret tool rest, to which tools used for machining workpieces held by the first spindle chuck and the second spindle chuck are attached, configured to move in a direction parallel to or perpendicular to the spindles of the first work spindle unit and the second work spindle unit; and a tailstock equipped with a retraction mechanism that displaces a rotatable center rod, which has centers on both ends and is brought into contact with the center of rotation of the workpiece from directions facing the first spindle chuck and the second spindle chuck, to a position deviated from the center of rotation.

[0009] According to the above configuration, when a workpiece held by the spindle chuck is machined using a tool on a turret tool post, the rotation of a long shaft workpiece can be stabilized during machining by a tailstock with a center rod abutting against its center of rotation. On the other hand, when a workpiece that does not require a tailstock is machined using the turret device, or when a workpiece is transferred between a first workpiece spindle device and a second workpiece spindle device, the retraction mechanism displaces the center rod of the tailstock to a position away from the center of rotation of the spindle (which corresponds to the center of rotation of the workpiece being machined), thereby preventing each device from interfering with the tailstock.

[0010] FIG. 1 is a perspective view showing an embodiment of the machine tool, particularly the internal structure of the machine body. FIG. 2 is a perspective view showing an embodiment of the machine tool, the internal structure of which is partially equipped with a cover member for coolant. FIG. 3 is a perspective view showing a tailstock that tailstocks a workpiece of a first workpiece spindle device. FIG. 4 is a perspective view showing the tailstock. FIG. 5 is a sectional view showing the configuration of a center part of the tailstock. FIG. 6 is a view showing the state of the tailstock during first machining. FIG. 7 is a view showing the state of the tailstock during workpiece transfer between the first and second workpiece spindle devices. FIG. 8 is a view showing the state of the tailstock during second machining.

[0011] An embodiment of a machine tool according to the present invention will be described below with reference to the drawings. Fig. 1 is a perspective view of the machine tool of this embodiment, particularly showing the internal structure of the machine body. The machine tool 1 of this embodiment is a small NC lathe in which various processing devices for processing a workpiece are mounted on a slant-type bed 6. The upper surface of the bed 6 is tilted forward, and mounted thereon are a first workpiece spindle unit 3 that rotatably grips a workpiece, a second workpiece spindle unit 4 that is disposed opposite the first workpiece spindle unit 3 and also rotatably grips a workpiece, and a turret unit 5 that has a plurality of turret tools T.

[0012] A first work spindle device 3 is disposed on the left side in front of the bed 6, and a second work spindle device 4 is disposed on the opposite right side. The first and second work spindle devices 3, 4 have spindles that are horizontal and in the machine body width direction, and furthermore, the spindles are disposed coaxially. In this embodiment, the direction parallel to the spindles of the first and second work spindle devices 3, 4 (the left-right width direction of the bed 6) will be described as the Z axis. The second work spindle device 4, which is coaxial with the first work spindle device 3, is configured to move in the machine body width direction, which is parallel to the Z axis.

[0013] The first work spindle device 3 has a spindle rotatably mounted on a casing 11, and a spindle chuck 12 integral with the spindle is rotated by a spindle motor to impart rotation to the gripped workpiece. The second work spindle device 4 is similarly configured to have a rotatable spindle mounted on a casing 15, and a spindle chuck 16 integral with the spindle is rotated by a spindle motor. In the first work spindle device 3, the casing 11 is integral with a headstock 13, and the headstock 13 is fixed to the bed 6, but in the second work spindle device 4, the casing 15 is mounted on a slidable headstock 14 and is configured to move in the Z-axis direction.

[0014] Two guide rails 18 parallel to the Z-axis for the second workpiece spindle device 4 are fixed to the bed 6. The headstock 14 is mounted integrally on a spindle table 17, and a guide block is fixed to the underside of the spindle table 17. The guide block engages with the guide rails 18 to form a linear guide. A screw shaft 19 parallel to the Z-axis is journaled between the two guide rails 18, and the rotation shaft of a Z-axis servo motor 20 is connected to the screw shaft 19. A nut member through which the screw shaft 19 passes is fixed to the underside of the spindle table 17, and a ball screw mechanism is formed in which the rotation output of the Z-axis servo motor 20 causes the spindle table 17 to move linearly in the Z-axis direction.

[0015] A turret device 5 is disposed behind the second workpiece spindle device 4. The turret device 5 has a plurality of turret tools T mounted at equal intervals in the circumferential direction on a disk-shaped turret tool rest 21, and the turret tool T to be used for machining can be selected by rotation indexing. The turret device 5 is configured so that the turret tool rest 21 moves in the Z-axis direction, a vertical direction perpendicular to the Z-axis, and a 45-degree direction that coincides with the inclination of the upper surface of the bed 6. In this embodiment, the direction of this vertical plane is referred to as the Y-axis, and the direction of inclination of the assembly surface 60 is referred to as the X-axis.

[0016] Two guide rails 23 parallel to the Z-axis are fixed to the right rear portion of bed 6, and a linear guide is formed by these and a guide block fixed to the underside of turret table 24. Turret table 24 is capable of moving in the Z-axis direction by a ball screw mechanism. That is, a screw shaft 25 parallel to the Z-axis is supported between the two guide rails 23 via bearings, and this screw shaft 25 passes through a nut member fixed to the underside of turret table 24. The rotating shaft of a Z-axis servo motor 26 is connected to the screw shaft 25, and the rotation output of this screw shaft moves turret table 24 linearly in the Z-axis direction.

[0017] A turret X-axis slide 27 is attached to the turret table 24 so as to slide on an X-axis guide rail formed on the upper surface of the turret table 24. A Y-axis guide rail is formed on the vertical front surface of the turret X-axis slide 27, and a turret main body 28, including the turret tool post 21 and the indexing servo motor 22, is attached to slide thereon. A screw shaft (not shown) connected to an X-axis servo motor 29 is supported on the turret table 24 via a bearing, and the screw shaft passes through a nut member fixed to the turret X-axis slide 27. Similarly, a screw shaft (not shown) connected to a Y-axis servo motor 30 is supported on the turret X-axis slide 27 via a bearing, and the screw shaft passes through a nut member fixed to the turret main body 28. Therefore, the rotational outputs of the X-axis servo motor 29 and the Y-axis servo motor 30 cause the turret X-axis slide 27 to move linearly in the X-axis direction, and the turret main body 28 to move linearly in the Y-axis direction.

[0018] Next, the machine tool 1 is provided with a tailstock 7 between the opposing first and second workpiece spindle devices 3, 4. The tailstock 7 stabilizes the rotation of one of the shaft workpieces W held by the first and second workpiece spindle devices 3, 4 during machining. The tailstock 7 in this embodiment is provided with a retraction mechanism that displaces the center that abuts against the center of rotation of the shaft workpiece W to a position away from that center of rotation. This is because it is necessary to avoid interference with other devices mounted on the bed 6, for example, so as not to interfere with the direct transfer of workpieces between the first and second workpiece spindle devices 3, 4.

[0019] Here, Fig. 2 is a perspective view showing the internal structure of the machine tool 1, similar to Fig. 1, with a coolant cover added to one portion. Fig. 3 is an enlarged view of the tailstock 7 shown in Fig. 2, showing the tailstock supporting the shaft workpiece W of the first work spindle device 3 at the center of rotation. Fig. 4 is a perspective view of the tailstock 7 shown from the opposite side of Fig. 3. The tailstock 7 has a center section 50 that supports the shaft workpiece W for rotation at the upper end of a displacement block 55. Fig. 5 is a cross-sectional view showing the configuration of the center section 50.

[0020] The center section 50 comprises a single center rod 51, which has conical centers 51L and 51R at both ends, integrated with a holder 53, and is rotatably attached to the upper end of a displacement block 55 by means of a plurality of radial bearings 54 provided in the axial direction. The displacement block 55 has a mountain-shaped section 551 formed at its upper part, into which the center section 50 is incorporated. The displacement block 55 also has a bifurcated section 552 formed below the mountain-shaped section 551, which extends parallel to both the left and right sides of the rotation center O of the center rod 51. A hydraulic cylinder 61 is provided inside the bifurcated section 552 to raise and lower the center section 50.

[0021] The hydraulic cylinder 61 has a rectangular parallelepiped cylinder tube that fits inside the bifurcated portion 552 and is fixed to the tailstock table 62. The piston rod 611 protrudes upward and extends toward the center portion 50, with its tip connected to the displacement block 55. The tailstock 7 has an elevation support base 63 fixed perpendicular to the tailstock table 62, and two guide blocks 64 fixed parallel to the outer upright plane. Two parallel guide rails 65 are fixed to the bifurcated portion 552 of the displacement block 55, forming a linear guide that can slide between the meshed guide blocks 64. Thus, the displacement block 55 is maintained in the upright position shown in the figure by the guide blocks 64 and guide rails 65, and can be raised and lowered using the hydraulic cylinder 61 as a driving source.

[0022] Figure 3 and other figures show the center rod 51 that rotatably supports the shaft workpiece W, and when the center of rotation O of this center rod 51 is positioned so that it coincides with the center of rotation of the spindle, this is the state in which tailstock 7 can perform tailstocking. In this state in which tailstocking is possible, the hydraulic cylinder 61 extends, and the displacement block 55 is positioned in a raised position, as shown in Figure 4. In contrast, the tailstock 7 is in a retracted state when the center of rotation O of the center rod 51 is displaced from the center of rotation of the spindle. In this retracted state, the hydraulic cylinder 61 retracts, and the displacement block 55 is positioned in a lowered position, as shown by the dashed line in Figure 4.

[0023] Furthermore, the tailstock 7 not only displaces the center rod 51 in a direction perpendicular to the spindle, but also moves in the Z-axis direction, enabling it to move to a tailstock position or a retracted position. Therefore, a mechanism for moving in the Z-axis direction relative to the tailstock table 62 is provided. A guide block is fixed to the underside of the tailstock table 62, similar to the spindle table 17, and this guide block meshes with a guide rail 18 shared with the second workpiece spindle unit 4 to form a linear guide. A threaded shaft parallel to the Z-axis for tailstock is supported between the two guide rails 18, and the rotation shaft of a tailstock servomotor (not shown) located on the opposite side of the Z-axis servomotor 20 is connected to this threaded shaft. A nut member through which a threaded shaft passes is fixed to the underside of the tailstock table 62, and a ball screw mechanism for tailstock is configured in which the rotation output of the tailstock servomotor causes linear movement of the tailstock table 62 in the Z-axis direction.

[0024] Incidentally, the machine tool 1 has a machining chamber, which is a closed space inside the machine where workpiece machining is performed, in which coolant is used to wash away chips and cool the machining area, etc. Therefore, as shown in Figure 2, the second workpiece spindle device 4 that moves inside the machining chamber is entirely covered by a spindle cover 41 with the spindle chuck 16 exposed, and the turret device 5 has the turret body 28, excluding the turret tool rest 21, covered by a turret cover 42.

[0025] Because the second work spindle unit 4, turret unit 5, and tailstock 7 of the machine tool 1 are movable, the floor of the machining chamber is composed of a combination of fixed and movable covers, allowing coolant and chips to flow down to the front side of the machine body. The second work spindle unit 4 and tailstock 7 share a guide rail 18, allowing them to move on the same line. A telescopic cover 67 is connected between the spindle cover 41 and the tailstock table 62, and extends and retracts in accordance with changes in the distance between the second work spindle unit 4 and the tailstock 7. In addition, a rectangular movable cover 68 is fixed to the tailstock table 62, similar to the turret table 24, so that they can move together.

[0026] Next, the machine tool 1 performs a first machining operation using the first workpiece spindle device 3 and the turret device 5, and a second machining operation using the second workpiece spindle device 4 and the turret device 5. Here, machining of a long shaft workpiece W shown in FIG. 2 and other figures will be described. Also, FIGS. 6 to 8 are diagrams showing the operations from the first machining operation to the second machining operation in the tailstock 7. First, in the first machining operation, the shaft workpiece W is gripped by the spindle chuck 12 by an operator, and predetermined machining is performed by automatic control of each device. At this time, the center rod 51 (center 51L) of the tailstock 7 is brought into contact with the shaft workpiece W from the opposite side of the spindle chuck 12, thereby performing tailstocking.

[0027] During the first machining operation, the second workpiece spindle device 4 has the spindle chuck 16 located in a fixed position on the right side of the machine body, as shown in Fig. 1. The tailstock 7 has a fixed position indicated by the dashed line in Fig. 6 (the same applies to Figs. 7 and 8), and tailstocking is performed by moving the center section 50 from there to the position indicated by the solid line. That is, the extension of the hydraulic cylinder 61 causes the displacement block 55 to slide upward, and the rotation center O of the center rod 51 coincides with the rotation center of the spindle of the first workpiece spindle device 3. Furthermore, the center rod 51 is moved in the Z-axis direction by drive control of the tailstock servomotor, and the center 51L is brought into contact with the end of the shaft workpiece W, thereby performing tailstocking.

[0028] At this time, the turret device 5 performs rotation indexing of the corresponding turret tool T in accordance with the machining content of the shaft workpiece W. Then, in the first workpiece spindle device 3, rotation is imparted to the shaft workpiece W, and in the turret device 5, the turret tool rest 21 is moved by drive control of the Z-axis servo motor 26 and the like, and the corresponding turret tool T is brought into contact with the rotating shaft workpiece W, thereby carrying out the specified machining.

[0029] Next, when the first machining is completed and the machining is switched to the second machining, the shaft workpiece W is transferred directly from the first workpiece spindle device 3 to the second workpiece spindle device 4 without using a workpiece transfer robot, as shown in Fig. 7. At this time, the second workpiece spindle device 4 approaches the first workpiece spindle device 3 from its home position by drive control of the Z-axis servo motor 20, and the spindle chuck 16 grips the opposite end of the shaft workpiece W gripped by the spindle chuck 12. At this time, the hydraulic cylinder 61 of the tailstock 7 is retracted and the tailstock 7 is moved to the position shown by the solid line in Fig. 7 so as not to interfere with the second workpiece spindle device 4. The turret device 5 has also returned to its home position shown in Fig. 1.

[0030] Thereafter, the second work spindle unit 4, which has received the shaft workpiece W, returns to its home position, and the center portion 50 of the tailstock 7 moves to the position shown by the solid line in Fig. 8, with the center 51R abutting against the end of the shaft workpiece W to perform tailstocking. That is, the extension operation of the hydraulic cylinder 61 causes the displacement block 55 to slide upward, and the rotation center O of the center rod 51 overlaps with the center line of the spindle of the second work spindle unit 4. Furthermore, the center rod 51 moves in the Z-axis direction under the drive control of the tailstock servo motor, and the center 51R abuts against the end of the shaft workpiece W. Then, in the turret unit 5, the corresponding turret tool T is swivel-indexed in the same manner as in the first machining, and the specified machining is performed on the shaft workpiece W that has been rotated by the second work spindle unit 4.

[0031] Therefore, according to the machine tool 1 of this embodiment, a retraction mechanism is provided in the tailstock 7 to shift the center of rotation O of the center rod 51 away from the center of rotation of the spindle, making it possible to transfer the shaft workpiece W from the first workpiece spindle device 3 to the second workpiece spindle device 4. This makes it possible to transport a workpiece without providing a workpiece transport robot inside the machine, thereby contributing to the miniaturization of the machine tool 1. Furthermore, the retraction mechanism widens the range in which the tailstock 7 and turret tool rest 21 do not interfere with each other, allowing the turret device 5 to be designed with a larger turret tool rest 21. Furthermore, the tailstock 7 itself does not need to move a large distance in the Z-axis direction to avoid interference with other devices, and in this respect too the retraction mechanism contributes to the miniaturization of the machine tool 1.

[0032] Although one embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications are possible without departing from the spirit of the present invention. For example, while the above embodiment has been described with reference to a machine tool 1 having two opposing axes, the machine tool may be configured without the second workpiece spindle device 4. Furthermore, while the tailstock retraction mechanism has been described with reference to a configuration using linear guides (64, 65) and a hydraulic cylinder 61, for example, the tailstock retraction mechanism may be configured to rotate the displacement block 55. Specifically, the tailstock retraction mechanism may be configured with a link mechanism combined with a hydraulic cylinder, or may be configured to rotate by the rotational output of a motor.

[0033] REFERENCE SIGNS LIST 1...machine tool 3...first workpiece spindle device 4...second workpiece spindle device 5...turret device 7...tailstock 12, 16...spindle chuck 21...turret tool rest 50...center section 51L, 51R...center 55...displacement block 61...hydraulic cylinder T...turret tool W...shaft work

Claims

1. A machine tool having: a work spindle device that imparts rotation to a work held by a spindle chuck; a turret device in which a turret tool rest, on which tools used to machine the work held by the spindle chuck are attached, is configured to move in a direction parallel to or perpendicular to the axis of the work spindle; and a core stock equipped with a retraction mechanism that displaces a rotatable center rod, which is brought into contact with the center of rotation of the work from a direction facing the spindle chuck, to a position away from the center of rotation.

2. A machine tool comprising: a first work spindle device fixed to a bed and rotating a workpiece held by a first spindle chuck; a second work spindle device assembled movably in a direction parallel to the spindle relative to the bed and rotating a workpiece held by a second spindle chuck coaxial with the first spindle chuck; a turret device assembled movably in a direction parallel to the spindle relative to the bed and configured to have a turret tool rest to which tools used for machining workpieces held by the first spindle chuck and the second spindle chuck are attached, the turret tool rest being configured to move in a direction parallel to or perpendicular to the spindles of the first work spindle device and the second work spindle device; and a core stock having centers on both ends and equipped with a retraction mechanism for displacing a rotatable center rod that abuts against the center of rotation of the workpiece from directions facing the first spindle chuck and the second spindle chuck, to a position away from the center of rotation.

3. A machine tool according to claim 1 or 2, wherein the retraction mechanism comprises a displacement block to which the center rod is rotatably attached and supported so as to be displaceable, and an actuator connected to the displacement block.

4. A machine tool as described in claim 3, wherein the retraction mechanism is a hydraulic cylinder in which the displacement block can be raised and lowered by a linear guide, and the actuator is arranged so as to be extendable and retractable in the direction of raising and lowering the displacement block, and is connected to the displacement block.

5. A machine tool according to claim 2, wherein said second work spindle device and said tailstock are mounted so as to be movable along the same guide rail fixed to the bed.

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