MACHINE TOOL

Description

FIELD

[0001] The present invention relates to a machine tool comprising two rotary feed axes which control the posture of a tool and three linear feed axes which move the position of a workpiece relative to the tool.BACKGROUND

[0002] There are various types of multi-axis machine tools comprising at least one rotary feed axis in addition to orthogonal three-axis linear feed axes, depending on the configuration of the feed axes. Patent Literature 1 describes an example of a machine tool comprising two rotary feed axes which control the posture of a tool, and three linear feed axes which move the position of a workpiece relative to the tool. In such a machine tool, the two rotary feed axes are moved relative to the workpiece in the linear direction along with a spindle head which rotatably supports the spindle on which the tool is mounted. Thus, the weight of the moving body including the two rotary feed axes and the spindle heads increases, and the column that movably supports the moving body with respect to a fixed part such as a bed of a machine tool may deform.

[0003] In particular, in the machine tool of Patent Literature 1, the carriage, saddle, head holder and spindle head constituting the moving body protrude with a significant overhang in the X-axis direction from a cross rail which is laterally mounted near the upper end of the column. Thus, in the machine tool of Patent Literature 1, the column and the cross rail may torsionally deform, whereby machining accuracy is reduced.

[0004] A known example of a machine tool comprising a linear feeding system is described in EP 1114694 A1, on which the preamble of appended claim 1 is based.

[0005] A known example of a machining center for round workpieces is described in EP 1291130 A2.

[0006] A known example of a multiple axle pivoting head assembly for a processing machine is described in EP 2305418 A1.[CITATION LIST][PATENT LITERATURE]

[0007] [PTL 1] Japanese Unexamined Patent Publication (Kokai) No. 2015-182170SUMMARY[TECHNICAL PROBLEM]

[0008] The object of the present invention is to solve such problems of the prior art and to provide a machine tool comprising two rotary feed axes which control the posture of a tool, and three linear feed axes which move the position of a workpiece relative to the tool, in which the position of the center of gravity of the moving body including the spindle head that rotatably supports the spindle to which the tool is attached is located so as to reduce the overhang from a fixed part such as the bed of the machine tool.[SOLUTION TO PROBLEM]

[0009] In order to achieve the above objects, according to the present invention, there is provided a machine tool as defined in claim 1.[ADVANTAGEOUS EFFECTS OF INVENTION]

[0010] According to the present invention, in a machine tool comprising two rotary feed axes which control the posture of a tool, and three linear feed axes which move the position of a workpiece relative to the tool, the overhang of a moving body comprising the two rotary feed axes and the spindle head can be reduced by inclining one of the two rotary feed axes, whereby deformation of the machine tool due to the weight of the moving body can be reduced.BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. 1 is a partially broken side view of a machine tool according to a preferred embodiment of the present invention. FIG. 2 is a front view of the machine tool of FIG. 1. DESCRIPTION OF EMBODIMENTS

[0012] A preferred embodiment of the present invention will be described below.

[0013] FIGS. 1 and 2 show an example of a machine tool comprising two rotary feed axes which control the posture of a tool, and three linear feed axes which move the position of a workpiece relative to the tool. The machine tool 10 comprises a bed 12 as a base which is secured to the floor of a factory, a column 14 which stands on and is secured to an upper surface of the bed 12 on a rear end side thereof (the right side in FIG. 1), a table 26 which is provided on an upper surface of a front portion of the bed 12 (the left side in FIG. 1) so as to be movable in the forward and rearward directions or the Y-axis direction (the left and right directions in FIG. 1) and to which a workpiece W is secured, a spindle head 22 which is provided above the table 26 and which rotatably supports a spindle 24, a saddle 16 which is provided on the top of the column 14 so as to be movable in the left and right directions or the X-axis direction (the direction perpendicular to the sheet of FIG. 1), and a spindle head support part which is provided on the saddle 16 and which supports the spindle head 22 so as to be rotatable around an axis of rotation Oa. The spindle head support part comprises a Z-axis slider 18 which is attached to the front surface of the saddle 16 so as to be movable in the upward and downward directions or the Z-axis direction, and a C-axis pivot shaft 20 which is supported on the Z-axis slider 18 so as to be rotatable around an inclination axis Oc as a second axis of rotation in the C-axis direction.

[0014] A pair of X-axis guide rails 28 which extend in the horizontal X-axis direction (the directions perpendicular to the sheet of FIG. 1) are provided on the upper end of the column 14, and a guide block 30 is attached to the column 14 so as to slide on the X-axis guide rails 28. A ball screw 32 which extends in the X-axis direction, and an X-axis servo motor 34 connected to one end of the ball screw are provided as an X-axis feed device for reciprocatively driving the saddle 16 along the X-axis guide rails 28, and a nut (not illustrated) for engagement with the ball screw 32 is attached to the saddle 16. Furthermore, an inclined surface 14a is formed on the upper end of the column 14. The inclined surface 14a extends diagonally upward parallel to the X-axis from the front surface side toward the rear surface side of the machine tool 10. The angle of the inclined surface 14a can be set to, for example, 45° relative to the horizontal plane (the XY plane).

[0015] A pair of Z-axis guide rails 36 extend on a front surface of the saddle 16 in the Z-axis direction (the upward and downward directions in FIGS. 1 and 2), which is the vertical direction, and a guide block 38 is attached to the Z-axis slider 18 so as to slide on the Z-axis guide rails 36. A ball screw 40 which extends in the Z-axis direction, and a Z-axis servo motor 44 connected to one end of the ball screw 40 are provided on the saddle 16 as a Z-axis feed device for reciprocatively driving the Z-axis slider 18 along the Z-axis guide rails 36, and a nut for engagement with the ball screw 40 is attached to the Z-axis slider 18 (a bracket 42 for attachment of the nut is illustrated in FIG. 1).

[0016] The C-axis pivot shaft 20 is rotatably supported on a lower end part of the Z-axis slider 18 by a bearing 50 so as to rotate about the inclination axis Oc. The inclination axis Oc extends diagonally upward from the front surface side to the rear surface side of the machine tool 10 perpendicular to the X-axis and substantially parallel to the inclined surface 14a. Though it is sufficient that the inclination axis Oc and the inclined surface 14a be inclined in the same direction, it is more effective if they are inclined nearly parallel with each other. The Z-axis slider 18 has incorporated therein a C-axis servo motor 52 as a C-axis feed device or a second rotational feed device for rotationally driving the C-axis pivot shaft 20. A pair of left and right arms 20a, 20b which extend parallel to the inclination axis Oc are formed on the tip of the front surface side of the C-axis pivot shaft 20.

[0017] The spindle head 22 supports the spindle 24 so as to be rotatable around the spindle axis Os, and a tool T is mounted on the tip of the spindle 24. The spindle head 22 is arranged between the pair of left and right arms 20a, 20b of the C-axis pivot shaft 20. The spindle head 22 is supported on the arms 20a, 20b of the C-axis pivot shaft 20 of the spindle head support part so as to be rotatable in the A-axis direction about the axis of rotation Oa as a first axis of rotation which is perpendicular to the inclination axis Oc by A-axis pivot shafts 22a, 22b formed on the side parts thereof. An A-axis servo motor 21 as an A-axis feed device or a first rotational feed device which is connected to one of the A-axis pivot shafts 22a, 22b (the A-axis pivot shaft 22a in the present embodiment) is incorporated in one of the arms 20a, 20b (the arm 20a in the present embodiment).

[0018] Note that the inclination axis Oc passes through the vicinity of the intersection O of the spindle axis Os of the spindle 24 and the axis of rotation Oa. Furthermore, as shown in FIG. 2, the rotational position of the C-axis feed device at which the axis of rotation Oa is parallel to the horizontal X-axis is set as the origin position of the C axis. Further, when the X-axis is in the origin position, the rotational position of the A-axis feed device at which the spindle axis Os of the spindle 24 is vertical is set as the origin position of the A-axis.

[0019] When the A-axis and the C-axis are in their origin positions, the end surface of the spindle 24 and the tool T mounted on the spindle 24 face the table 26 on which the workpiece (not illustrated) is attached. A pair of Y-axis guide rails 46 extend on the upper surface of the bed 12 in the horizontal Y-axis direction (the left and right directions in FIG. 1), and a guide block 48 is attached to the table 26 so as to slide on the Y-axis guide rails 46. A ball screw (not illustrated) which extends in the Y-axis direction, and a Y-axis servo motor (not illustrated) connected to one end of the ball screw are provided as a Y-axis feed device for reciprocatively driving the table 26 along the Y-axis guide rails 46, and a nut (not illustrated) for engagement with the ball screw is attached to the table 26.

[0020] According to the present embodiment, in a machine tool comprising two rotary feed axes for controlling the posture of a tool and three linear feed axes for moving the position of a workpiece relative to the tool, the overhang of the moving body comprising the two rotary feed axes of the A-axis feed device and C-axis feed device and the spindle head 22 with respect to the column 14 can be reduced by inclining the C-axis pivot shaft 20, which forms one of the two rotary feed axes, toward the column 14, whereby the center of gravity of the moving body can be shifted toward the column 14 side. As a result, deformation of the column 14 and saddle 16 can be reduced. Furthermore, when the moving body moves, deformation of the saddle 16 and the Z-axis slider 18 during acceleration and deceleration is reduced.

[0021] A recess 16b is preferably formed in a front surface of the saddle 16, and the Z-axis ball screw 40 can be arranged in the recess 16b. Further, at least a part of the spindle head support part can be arranged in the recess 16b of the saddle 16. As a result, the overhang of the moving body with respect to the column 14 can be further reduced.REFERENCE SIGNS LIST

[0022] 10Machine Tool 12Bed 14Column 14aInclined Surface 16Saddle 16bRecess 18Z-axis Slider 20C-axis Pivot Shaft 20aArm 20bArm 21A-axis Servo Motor 22Spindle Head 22aA-axis Pivot Shaft 22bA-axis pivot shaft 24Spindle 26Table 28X-axis Guide Rail 34X-axis Servo Motor 36Z-axis Guide Rail 42Bracket 44Z-axis Servo Motor 46Y-axis Guide Rail 50Bearing 52C-axis Servo Motor

Claims

1. A machine tool (10) having two rotary feed axes (A, C) which control the posture of a tool (T), and a linear feed axis which moves a position of a workpiece (W) relative to the tool (T), the machine tool (10) comprising: a spindle (24) having a tip on which the tool (T) is mounted, a spindle head (22) which supports the spindle (24) so as to be rotatable around an axis of rotation (Os) of the spindle (24), a spindle head support part which supports the spindle head (22) so as to be rotatable around a first axis of rotation (A) which extends perpendicular to the axis of rotation (Os) of the spindle (24), a first rotary device (21) which is provided on the spindle head support part and which rotates the spindle head (22) around the first axis of rotation (A), a saddle (16) which supports the spindle head support part so as to be rotatable around a second axis of rotation (C) which is perpendicular to the first axis of rotation (A) and which is inclined with respect to the vertical direction, and a second rotary feed axis device (52) which is provided on the saddle (16) and which rotates the spindle head support part around the second axis of rotation (C), wherein the spindle head support part comprises a pair of left and right arms (20a, 20b) formed on a C-axis pivot shaft (20) which is supported so as to be rotatable around the second axis of rotation (C) on a Z-axis slider (18) which is attached to a front surface of the saddle (16) so as to be reciprocatable in the vertical directions, and characterized in that the machine tool further comprises a bed (12) and a column (14) which is provided on the bed (12) and which supports the saddle (16) so as to be horizontally reciprocatable in the left and right directions, wherein the column (14) has an inclined surface (14a) which extends substantially parallel to the second axis of rotation (C), and wherein the saddle (16) is arranged above the inclined surface (14a).

2. The machine tool (10) according to claim 1, wherein the second rotary feed axis device (52) comprises a servo motor which is incorporated in the spindle head support part and which is connected to the C-axis pivot shaft (20).

3. The machine tool (10) according to claim 1, wherein the spindle head (22) comprises an A-axis pivot shaft (22a, 22b) which is supported on the pair of left and right arms (20a, 20b) so as to be rotatable around the horizontal first axis of rotation (A).

4. The machine tool (10) according to claim 3, wherein the first rotary feed axis device (21) comprises a servo motor which is incorporated in one of the pair of left and right arms (20a, 20b) and which is connected to the A-axis pivot shaft (22a, 22b) of the spindle head (22).