Chuck device

Abstract

In a chuck device for gripping a workpiece, it is necessary to firmly grip the workpiece while suppressing the distortion generated in the workpiece. 【Solution means】The chuck device 1 includes a main body portion 11, at least three master jaws 12A - 12F each configured to be movable in the radial direction of the workpiece, at least three centering portions 13A - 13C each of which moves together with the master jaw and aligns the central axis of the workpiece with the reference position in the machine tool by contacting the workpiece, a plurality of clamping portions 14A - 14F provided at positions shifted in the circumferential direction of the workpiece from the master jaws 12A - 12F and gripping the inner peripheral surface and the outer peripheral surface of the workpiece, and a plurality of fixing members each fixing the corresponding clamping portion to the main body portion 11.

Description

Technical Field

[0001] The present invention relates to a chuck device for gripping a workpiece in a machine tool.

Background Art

[0002] As an example of a chuck device for fixing a cylindrical workpiece to a machine tool, a scroll chuck is known. In a scroll chuck, claws are attached to each of three or more master jaws that move synchronously in the radial direction of the workpiece. The scroll chuck presses each claw against the outer peripheral surface of the workpiece by moving each master jaw, and grips the workpiece. When machining the workpiece, a machining load is applied to the workpiece. Therefore, it is desirable for the scroll chuck to firmly grip the workpiece.

[0003] However, for example, if a scroll chuck firmly grips a workpiece having a large outer diameter or a thin wall thickness from the outer peripheral surface side, the workpiece is likely to be greatly deformed and the workpiece is likely to be deformed. In this case, it is necessary to perform a finishing process to finish the workpiece to a predetermined machining accuracy, and it is difficult to improve the machining efficiency. On the other hand, if the scroll chuck weakly grips the workpiece, the workpiece is likely to move due to the machining load. As a result, it is difficult to perform a predetermined process, and the workpiece is likely to vibrate during machining.

[0004] In contrast, Patent Document 1 discloses a chuck device that grips a workpiece from both the inner peripheral surface and the outer peripheral surface of a cylindrical workpiece. In this chuck device, an inner claw portion that contacts the inner peripheral surface of the workpiece and an outer claw portion that contacts the outer peripheral surface of the workpiece are provided on the master jaw. The inner claw portion is fixed to the master jaw and moves in the radial direction of the workpiece together with the master jaw. The outer claw portion is attached to the master jaw but is configured to be able to approach and separate from the inner claw portion. When gripping a workpiece with this chuck device, first, the inner claw portion and the outer claw portion are separated, and the workpiece is placed between the inner claw portion and the outer claw portion. Next, the master jaw is moved radially outward of the workpiece, and all the inner claw portions are brought into contact with the inner peripheral surface of the workpiece. Thereby, the centering of the workpiece is performed. Subsequently, the outer claw portion is moved radially inward of the workpiece, and all the outer claw portions are brought into contact with the outer peripheral surface of the workpiece. Thereby, the workpiece is clamped between the inner claw portion and the outer claw portion.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The chuck device of Patent Document 1 sandwiches the workpiece from both the outer peripheral surface and the inner peripheral surface of the workpiece. Therefore, compared with a scroll chuck that applies gripping force only from the outer peripheral surface, it is less likely for the workpiece to be distorted. However, in this chuck device, the inner claw portion and the outer claw portion are attached to the master jaw. The master jaw moves in the radial direction of the workpiece by a feed screw. Therefore, there is backlash between the master jaw and the feed screw. For example, assume that the inner claw portion and the outer claw portion are separated and the workpiece is placed between the inner claw portion and the outer claw portion. From this state, when the feed screw is operated and the master jaw is moved outward in the radial direction of the workpiece, the master jaw is pressed against the feed screw so as to move outward in the radial direction of the workpiece. On the other hand, a gap, that is, backlash occurs between the surface of the master jaw on the side opposite to the surface pressed against the feed screw and the feed screw. Even if the outer claw portion is brought into contact with the outer peripheral surface of the workpiece and the workpiece is gripped by the inner claw portion and the outer claw portion from this state, the master jaw can move inward in the radial direction of the workpiece by the amount of backlash. In order to suppress the rattling of the master jaw due to backlash, it is necessary to machine the workpiece while pressing the master jaw against the feed screw so as to move outward in the radial direction of the workpiece. However, in this case, the inner claw portion fixed to the master jaw is strongly pressed against the inner peripheral surface of the workpiece, and there is still a possibility that the workpiece may be distorted.

[0007] An object of the present invention is to firmly grip a workpiece while suppressing distortion occurring in the workpiece in a chuck device for gripping the workpiece.

Means for Solving the Problem

[0008] (1) The chuck device of the present invention is a chuck device used in a machine tool for gripping a cylindrical workpiece, and includes a main body portion, at least three master jaws provided on the main body portion and each configured to be movable in the radial direction of a reference axis, a drive mechanism provided on the main body portion corresponding to the at least three master jaws and configured to move each of the at least three master jaws in conjunction with each other in the radial direction of the reference axis, at least three centering portions each attached to a corresponding one of the master jaws and moving together with the master jaw, and configured to align the central axis of the workpiece with the reference axis by contacting the workpiece at at least three points, a plurality of clamping portions provided at positions shifted in the circumferential direction of the reference axis from the at least three master jaws and configured to clamp the inner circumferential surface and the outer circumferential surface of the workpiece after the central axis has been aligned with the reference axis by the at least three centering portions, and a fixing structure provided between the clamping portion and the main body portion and configured to be able to switch between a temporary fixing state in which the clamping portion is movable in the radial direction of the reference axis and a final fixing state in which the clamping portion is fixed to the main body portion.

[0009] In the above-described chuck device, an aligning portion for aligning the workpiece and a clamping portion for clamping the workpiece are provided separately. The aligning portion is attached to a master jaw that moves by a feed screw mechanism. However, the workpiece alignment operation can be performed by each aligning portion merely lightly contacting the workpiece. Therefore, each aligning portion does not need to be strongly pressed against the workpiece in order to cancel out the rattling due to the backlash of the feed screw mechanism. On the other hand, the clamping portion needs to firmly clamp the workpiece so that the workpiece does not move due to the machining load. In the above-described chuck device, each clamping portion is not attached to a master jaw that moves by a feed screw mechanism. Therefore, each clamping portion can clamp the workpiece without being affected by the backlash of the feed screw mechanism. Moreover, each clamping portion clamps the workpiece by applying forces from both the inner peripheral surface and the outer peripheral surface of the workpiece. Therefore, the force applied to the workpiece by the clamping portion is suppressed as compared with the case where the workpiece receives force only from the outer peripheral surface and the case where the workpiece receives force only from the inner peripheral surface. That is, with the above fixing structure, the inner peripheral surface and the outer peripheral surface of the cylindrical workpiece aligned with respect to the reference axis with the clamping portion in a temporarily fixed state are clamped. Then, since the clamping portion is movable in the radial direction with respect to the reference axis, it naturally moves in the radial direction in accordance with the workpiece until the inner peripheral surface and the outer peripheral surface of the workpiece are evenly clamped. And it can be fixed to the holding portion in a state where the clamping portion is aligned in accordance with the workpiece aligned by the above fixing structure. Therefore, according to the above chuck device, the inner peripheral surface and the outer peripheral surface of the workpiece can be evenly clamped by the clamping portion regardless of the diameter of the aligned workpiece, and the workpiece can be firmly gripped while suppressing the strain generated in the workpiece.

[0010] (2) In the chuck device of (1) above, each of the plurality of clamping portions includes an inner claw portion that contacts the inner peripheral surface of the workpiece and an outer claw portion that is provided on the moving member to be paired with the inner claw portion and contacts the outer peripheral surface of the workpiece. The fixing structure may include a base member fixed to the main body portion, a moving member to which the clamping portion is fixed, an engaging structure formed between the base member and the moving member to engage the moving member linearly movably with respect to the base member, and a fixing member that fixes the moving member to the base member or the main body portion.

[0011] In the chuck device of (2) above, the fixing structure can be easily formed at an arbitrary position of the main body portion. For example, when the diameter of the workpiece is large and it is desired to clamp the workpiece at multiple points with more than three of the clamping portions, the fixing structure can be easily added to each clamping portion.

[0012] (3) In the chuck device of (2) above, the inner claw portion may include a spherical surface that contacts the inner peripheral surface of the workpiece, and the outer claw portion may include a spherical surface that contacts the outer peripheral surface of the workpiece.

[0013] In the chuck device of (3) above, the workpiece is gripped by spherical surfaces from both the inner peripheral surface side and the outer peripheral surface side. As a result, the workpiece is substantially clamped point by point, and the clamping portion can firmly clamp the workpiece.

[0014] (4) In the chuck device of (1) above, each of the plurality of fixing members may fix the corresponding clamping portion to the main body portion by applying a force in a direction pressing the clamping portion against the main body portion.

[0015] For example, when the fixing member is a bolt, if a force is applied in the radial direction of the workpiece to the corresponding clamping portion for fixing, an unnecessary radial force is likely to be applied to the workpiece gripped by the clamping portion. On the other hand, in the chuck device of the above (4), the fixing member fixes the clamping portion to the main body portion by applying a force in a direction different from the radial direction of the workpiece. Therefore, according to the above chuck device, the workpiece can be firmly clamped while suppressing the distortion generated in the workpiece.

[0016] (5) In the chuck device of the above (1), the plurality of clamping portions and / or at least three centering portions may be arranged at equal intervals in the circumferential direction of the workpiece.

[0017] According to the chuck device of the above (5), each clamping portion can stably clamp the workpiece. Also, according to the above chuck device, each centering portion can accurately center the workpiece.

[0018] (6) In the chuck device of the above (1), at least three centering portions each include a contact member that aligns the central axis of the workpiece with the reference position in the machine tool by contacting the inner peripheral surface or the outer peripheral surface of the workpiece, and the contact member may include a curved surface that contacts the inner peripheral surface or the outer peripheral surface of the workpiece.

[0019] In the chuck device of the above (6), during the centering operation of the workpiece, the curved surface of the contact member contacts the workpiece at each centering portion. Thereby, the contact member contacts the workpiece substantially at a point. Therefore, each centering portion can accurately center the workpiece and can contact the workpiece so as not to apply an unnecessary force to the workpiece.

[0020] (7) In the chuck device of the above (1), at least three centering portions each include a seating surface on which the workpiece is placed, and the seating surface may be provided at a position closer to the main body portion than the position where the plurality of clamping portions clamp the inner peripheral surface and the outer peripheral surface of the workpiece.

[0021] For example, assume that the chuck device is placed on the table of a machine tool. In the chuck device of (7) above, when attaching a workpiece to the chuck device placed on the table, the workpiece can be placed on the seating surface of each centering portion. Further, each seating surface is provided below (a position closer to the main body portion) than the gripping position by each gripping portion. Therefore, the end of the workpiece comes to be positioned below the gripping position, and the workpiece can be gripped only by moving each gripping portion in the radial direction of the workpiece. Thus, according to the above chuck device, the efficiency of the setup work for attaching the workpiece to the chuck device is increased.

[0022] (8) In the chuck device of (1) above, the workpiece may have a scale on at least a part of its inner peripheral surface and / or outer peripheral surface.

[0023] A steel workpiece is manufactured, for example, by forging or casting. An oxide film, that is, a scale may adhere to the surface of the manufactured workpiece. In a machine tool, there may be cases where a workpiece with the scale left unremoved is processed. The surface of a workpiece with a scale is rough. Therefore, for example, when gripping a workpiece with a scale using a chuck device that holds the workpiece by applying a force toward the outer or inner side in the radial direction of the workpiece, the force of each gripping portion is likely to vary, and the workpiece is likely to be deformed. On the other hand, in the above chuck device, the workpiece can be held firmly without substantially applying a force toward the outer or inner side in the radial direction of the workpiece. Thus, the above chuck device is particularly suitable for gripping a workpiece having a scale.

[0024] (9) In the chuck device of (1) above, the workpiece may be a large-diameter thin-wall workpiece. In other words, the workpiece is a workpiece in which the ratio of the thickness dimension to the diameter dimension is a predetermined value or less.

[0025] When the thickness of the workpiece is thin, if a force acting radially outward or inward is applied to the workpiece, the workpiece is likely to be distorted. Also, it is difficult for an operator to attach a large-diameter workpiece to the chuck device while performing centering work. In contrast, with the above-described chuck device, the workpiece can be held without substantially applying a force acting radially outward or inward to the workpiece. Further, since the centering operation can be performed by moving each centering portion in the radial direction, the operator only needs to temporarily place the workpiece on the chuck device and does not need to attach it while performing the centering operation. Therefore, the above-described chuck device is particularly suitable for gripping large-diameter thin-walled workpieces. A large-diameter thin-walled workpiece is, for example, a workpiece having an outer diameter of 500 mm or more. A large-diameter thin-walled workpiece is, for example, a workpiece having a thickness of 30 mm or less. However, these workpiece dimensions are merely examples. The above-described chuck device is suitable for gripping workpieces generally referred to as large-diameter thin-walled workpieces and is also applicable to gripping workpieces other than large-diameter thin-walled workpieces.

Advantages of the Invention

[0026] According to the processing system of the present invention, in a chuck device for gripping a workpiece, the workpiece can be firmly gripped while suppressing the strain generated in the workpiece.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0028] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0029] FIG. 1 is a perspective view of a chuck device. The chuck device 1 is used to grip a cylindrical workpiece in a machine tool. In the present embodiment, the machine tool is a vertical machining center (composite machining machine) having a turning function in addition to a milling function. The machine tool may be a turning center having only a turning function, or a machining center having only a milling function. In short, the machine tool is not particularly limited as long as it can machine a cylindrical workpiece. In the figure, the chuck device 1 is shown in a state of being provided on a rotary table 2 in the machining chamber of the machine tool. The chuck device 1 includes a main body portion 11, six master jaws 12A - 12F, three centering portions 13A - 13C, and a plurality of clamping portions 14A - 14F.

[0030] The main body portion 11 has a disk shape. The main body portion 11 includes a circular recess 111 at its central portion and a panel portion formed around the recess 111 to which various devices are attached. The main body portion 11 is fixed on the rotary table 2 of the machine tool. The central axis of the main body portion 11 coincides with or substantially coincides with the rotation axis of the rotary table 2. The main body portion 11 rotates together with the rotary table 2. The main body portion 11 constitutes the base of the chuck device 1, and the respective master jaws 12A - 12F, the respective centering portions 13A - 13C, and the plurality of clamping portions 14A - 14F are provided thereon. When the chuck device 1 grips a workpiece, the reference axis CL that coincides with the central axis of the main body portion 11 and the central axis of the workpiece coincide or substantially coincide. Therefore, the circumferential direction and the radial direction of the main body portion 11 are synonymous with the circumferential direction and the radial direction of the workpiece, and the circumferential direction and the radial direction of the reference axis CL. Also, the reference axis CL is orthogonal to the virtual plane including the panel portion of the main body portion 11.

[0031] The six master jaws 12A - 12F are arranged side by side along the circumferential direction of the main body 11. The six master jaws 12A - 12F are arranged at equal intervals along the circumferential direction of the main body 11. Each of the six master jaws 12A - 12F has the same configuration. Therefore, hereinafter, unless otherwise specified, one master jaw 12A will be described. The master jaw 12A has a substantially rectangular parallelepiped shape. The master jaw 12A is provided such that its longitudinal direction is along the radial direction of the main body 11. The master jaw 12A is provided on the main body 11 such that at least a part of its upper surface is exposed from the main body 11. The master jaw 12A is provided on the main body 11 so as to be movable in the radial direction of the main body 11. Each of the six master jaws 12A - 12F moves in the radial direction of the main body 11 by a feed screw mechanism provided on the main body 11 corresponding to each master jaw.

[0032] Figure 2 is a partial cross-sectional view of a chuck device schematically showing a feed screw mechanism. The chuck device 1 of the present embodiment includes six feed screw mechanisms, but since each feed screw mechanism has the same configuration, hereinafter, unless otherwise specified, one feed screw mechanism will be described.

[0033] The feed screw mechanism 15 is provided inside the main body 11. The feed screw mechanism 15 extends in the radial direction of the main body 11. The feed screw mechanism 15 has a rotation axis parallel to the radial direction of the main body 11. The feed screw mechanism 15 is fixed to the main body 11 so as to be rotatable around the rotation axis. In the feed screw mechanism 15, the end portion on the outer side in the radial direction of the main body 11 extends to the handle hole 112 provided on the side surface of the main body 11. The feed screw mechanism 15 rotates around the rotation axis by operating the chuck handle attached to the handle hole 112. In the feed screw mechanism 15, the end portion on the inner side in the radial direction of the main body 11 extends to the recess 111 of the main body 11. In the feed screw mechanism 15, the end portion on the inner side in the radial direction of the main body 11 is connected to another feed screw mechanism via an interlocking mechanism (not shown). Thereby, the six feed screw mechanisms 15 rotate synchronously around the rotation axis of each screw mechanism. The feed screw mechanism 15 is connected to the corresponding master jaw 12A. When the feed screw mechanism 15 rotates around the rotation axis, the master jaw 12A moves in the radial direction of the main body 11.

[0034] Referring to FIG. 1, the three centering portions 13A - 13C are respectively attached to the corresponding master jaws. That is, the centering portion 13A is attached to the master jaw 12A, the centering portion 13B is attached to the master jaw 12C, and the centering portion 13C is attached to the master jaw 12E. In this embodiment, no centering portion is attached to the remaining master jaws 12B, 12D, 12F. The three centering portions 13A - 13C each have the same configuration. Therefore, hereinafter, unless otherwise particularly mentioned, one centering portion 13A will be described. The centering portion 13A includes a block member 131 and a contact member 132.

[0035] The block member 131 has a substantially rectangular parallelepiped shape. The block member 131 is provided such that its longitudinal direction is along the radial direction of the main body portion 11. The block member 131 is fixed to the upper surface of the corresponding master jaw 12A. The block member 131 moves in the radial direction of the main body portion 11 together with the master jaw 12A. The block member 131 includes a seating surface 1311 provided on its upper surface for placing the workpiece. The seating surface 1311 is provided in a predetermined range from the inner end in the radial direction of the main body portion 11 on the upper surface of the block member 131. The seating surface 1311 is a flat surface.

[0036] The contact member 132 is fixed to the block member 131. The contact member 132 is, for example, a pin. The contact member 132 is provided such that at least a part of it protrudes from the upper surface of the block member 131. The contact member 132 has a cylindrical shape. That is, the side surface of the contact member 132 is a curved surface. The contact member 132 is provided outside the seating surface 1311 in the radial direction of the main body portion 11. As will be described later, the contact member 132 has a centering function of aligning the central axis of the workpiece with the reference position in the machine tool by contacting the outer peripheral surface of the workpiece.

[0037] The reference position is a position that coincides with the rotation center axis of the rotary table 2 in the machine tool in a top view. In short, when the machine tool has a turning function, the reference position is a position defined by the rotation axis of the workpiece spindle that rotates the workpiece. When the machine tool has only a milling function, the reference position is the control reference position of the tool spindle that holds the tool in the machine tool.

[0038] The plurality of clamping parts 14A - 14F are arranged side by side along the circumferential direction of the main body part 11. The plurality of clamping parts 14A - 14F are arranged at equal intervals along the circumferential direction of the main body part 11. Each of the plurality of clamping parts 14A - 14F is provided so as to face another one of the clamping parts in the radial direction of the main body part 11. Each of the plurality of clamping parts 14A - 14F is provided at a position shifted in the circumferential direction of the main body part 11 from the six master jaws 12A - 12F in the main body part 11. Each of the plurality of clamping parts 14A - 14F is provided between two adjacent master jaws in the circumferential direction. Each of the plurality of clamping parts 14A - 14F is provided so as not to overlap the six master jaws 12A - 12F when viewed in the central axis direction of the main body part 11. Each of the plurality of clamping parts 14A - 14F is not interlocked with the radial movement of the six master jaws 12A - 12F. Each of the plurality of clamping parts 14A - 14F is configured to be movable in the radial direction of the main body part 11 independently of the six master jaws 12A - 12F. Each of the plurality of clamping parts 14A - 14F is, for example, a centering vise.

[0039] Figure 3(A) is an exploded view of the clamping part seen obliquely from above. Each of the plurality of clamping parts 14A - 14F has the same configuration. Therefore, hereinafter, unless otherwise particularly mentioned, one clamping part 14A will be described. The clamping part 14A includes a vise main body 143, an inner claw part 144, and an outer claw part 145. Further, between the clamping part 14A and the main body part 11, a fixing structure FA is provided that can switch between a temporarily fixed state in which the clamping part 14A is movable in the radial direction of the reference axis CL and a fixed state in which the clamping part 14A is fixed to the main body part 11.

[0040] The base member 141 is fixed to the main body part 11. The base member 141 has a plate shape. The base member 141 includes a guide rail 1411 on its upper surface. The guide rail 1411 has a groove shape. The guide rail 1411 is provided along the radial direction of the main body part 11. A moving member 142 is attached on the base member 141.

[0041] Figure 3(B) is an exploded view of the clamping portion as seen from diagonally below. The moving member 142 has a plate shape. The moving member 142 includes a plurality of convex portions 1421 protruding from its lower surface. The plurality of convex portions 1421 are provided side by side in the radial direction of the main body portion 11. The plurality of convex portions 1421 are configured to fit into the guide rail 1411. The plurality of convex portions 1421, together with the guide rail 1411, regulate the moving direction of the moving member 142. With such a configuration, the moving member 142 is configured to be movable in the radial direction of the main body portion 11 with respect to the main body portion 11. The moving member 142 includes two long holes 1422 for inserting a fixing member 16, which will be described later. Each long hole 1422 extends in the radial direction of the main body portion 11. A vice main body 143 is provided on the moving member 142.

[0042] Referring to Figure 3(A), the vice main body 143 is fixed to the moving member 142. The vice main body 143 supports the inner claw portion 144 and the outer claw portion 145 respectively via a feed mechanism 146. The inner claw portion 144 is provided opposite to the outer claw portion 145 in the radial direction of the main body portion 11. The inner claw portion 144 and the outer claw portion 145 are provided in pairs. The feed mechanism 146 is composed of, for example, a feed screw. The feed mechanism 146 extends in the radial direction of the main body portion 11. By operating the head portion 1461 provided at its end, the inner claw portion 144 and the outer claw portion 145 are moved in the radial direction of the main body portion 11 with respect to the vice main body 143 (moving member 142). The part of the feed mechanism 146 responsible for the movement of the inner claw portion 144 and the part responsible for the movement of the outer claw portion 145 have opposite threads. Thereby, by operating the head portion 1461, the inner claw portion 144 and the outer claw portion 145 are configured to be able to approach and separate along the radial direction of the main body portion 11.

[0043] The outer claw portion 145 includes a spherical bolt 1451 protruding from the surface facing the inner claw portion 144. The head of the spherical bolt 1451 contacts the inner peripheral surface of the workpiece. The head of the spherical bolt 1451 is spherical. It is preferable that the radius of curvature of the spherical surface is smaller than the radius of the workpiece. The head of the spherical bolt 1451 is provided above the seating surface 1311 of each centering portion 13A - 13C. The inner claw portion 144 is configured in the same way.

[0044] The chuck device 1 further includes two fixing members 16 that fix the moving member 142 to the base member 141. Since the two fixing members 16 have the same configuration, hereinafter, unless otherwise specifically mentioned, one fixing member 16 will be described. The fixing member 16 is, for example, a bolt. The fixing member 16 makes the moving member 142 movable and immovable with respect to the main body portion 11. When the fixing member 16 is inserted into the long hole 1422 and not fastened, the moving member 142 is movable with respect to the base member 141 (main body portion 11). When the fixing member 16 is inserted into the long hole 1422 and fastened, the moving member 142 is fixed to the base member 141. That is, the moving member 142 becomes immovable with respect to the main body portion 11. Further, the fixing member 16 fixes the moving member 142 to the base member 141 by applying a force in a direction different from the radial direction of the main body portion 11. The fixing member 16 fixes the moving member 142 with respect to the main body portion 11 by applying a force in the direction of pressing the moving member 142 against the base member 141 (main body portion 11).

[0045] In this embodiment, the configuration in which the two fixing members 16 fix the clamping portion 14A to the main body portion 11 has been described. The same applies to the remaining five clamping portions 14B - 14F. Also, in this embodiment, the two fixing members 16 fix one clamping portion 14A to the main body portion 11. However, the number of fixing members 16 for one clamping portion 14A is not particularly limited.

[0046] Subsequently, the method of gripping a workpiece by the chuck device 1 of this embodiment will be described.

[0047] FIG. 4 is a view showing the chuck device and the workpiece in the direction of the central axis of the workpiece. First, the chuck device 1 is placed and fixed on the rotary table 2 of the machine tool. Next, the workpiece W is placed on the three centering portions 13A - 13C. In this state, the workpiece W is supported by the seating surfaces 1311 of the three centering portions 13A - 13C and is positioned between the inner claw portions 144 and the outer claw portions 145 of each clamping portion 14A - 14F. Next, by moving the master jaws 12A, 12C, 12E, each of the three centering portions 13A - 13C is moved toward the inner side in the radial direction of the workpiece W, and the contact members 132 of each centering portion are brought into contact with the outer peripheral surface of the workpiece W. At this time, each of the three centering portions 13A - 13C contacts the outer peripheral surface of the workpiece W so as not to cause or substantially not to cause distortion in the workpiece W. Thereby, the central axis of the workpiece W comes to coincide with the reference position (the rotation axis of the rotary table 2) in the machine tool, and the so-called centering operation is completed.

[0048] Next, in the clamping portion 14A, the fixing member 16 is inserted into the moving member 142, and the moving member 142 is temporarily fixed to the base member 141. In this state, the fixing member 16 does not completely fix the moving member 142 to the base member 141, and the moving member 142 is movable in the radial direction of the workpiece W. Next, in the clamping portion 14A, the workpiece W is clamped between the inner claw portion 144 and the outer claw portion 145. Next, the fixing member 16 is fastened to completely fix the moving member 142 to the base member 141. The same applies to the remaining clamping portions 14B - 14F. Thereby, the workpiece W is gripped by the chuck device 1 and becomes in a state where it can be processed.

[0049] As described above, in the chuck device 1 of the present embodiment, the centering portions 13A - 13C for centering the workpiece W and the clamping portions 14A - 14F for clamping the workpiece W are provided separately. The centering portions 13A - 13C are respectively attached to the master jaws 12A, 12C, 12E. However, the centering operation of the workpiece can be performed only by the centering portions 13A - 13C lightly contacting the workpiece. Therefore, each of the centering portions 13A - 13C does not need to be strongly pressed against the workpiece W to cancel out the rattling caused by the backlash of the feed screw mechanism 15. On the other hand, the clamping portions 14A - 14F are not attached to any of the master jaws 12A - 12F. Therefore, each of the clamping portions 14A - 14F can clamp the workpiece without being affected by the backlash of the feed screw mechanism. Moreover, each of the clamping portions 14A - 14F clamps the workpiece by applying forces from both the inner circumferential surface and the outer circumferential surface of the workpiece by the inner claw portion 144 and the outer claw portion 145. Therefore, compared with the case where the workpiece receives force only from the outer circumferential surface or only from the inner circumferential surface, the force applied to the workpiece by the clamping portion is suppressed. Thus, in the chuck device 1, in both the centering operation of the workpiece W and the gripping operation of the workpiece W, it is difficult to load a radial force on the workpiece W. Therefore, according to the above chuck device, the workpiece can be firmly gripped while suppressing the distortion generated in the workpiece.

[0050] In particular, the chuck device 1 is effective when the workpiece to be gripped is a large - diameter thin - walled workpiece. That is, in a large - diameter thin - walled workpiece, distortion is likely to occur when a force is loaded in the radial direction. When distortion occurs in a large - diameter thin - walled workpiece, it is necessary to perform re - machining to adjust the dimensions of the machined workpiece, and it is difficult to improve the machining efficiency. To suppress this, it is conceivable to reduce the gripping force by the chuck device. However, in this case, the workpiece is likely to move or vibrate during machining. On the other hand, in the chuck device 1 of the present embodiment, the workpiece can be firmly gripped while suppressing the distortion generated in the workpiece. Therefore, even when the workpiece to be gripped is a large - diameter thin - walled workpiece, the desired machining can be performed, and the machining efficiency is improved.

[0051] The description of the above-described embodiments is illustrative in all respects and not restrictive. Modifications and variations are appropriately possible for those skilled in the art. The scope of the present invention is indicated not by the above-described embodiments but by the claims. Further, the scope of the present invention includes modifications from the embodiments within the scope equivalent to the claims.

[0052] For example, in the above-described embodiment, the case where the chuck device 1 includes six master jaws 12A - 12F has been described. However, the number of master jaws is not limited to this. The chuck device 1 may include at least three master jaws. Similarly, the chuck device 1 may include at least three feed screw mechanisms for moving the master jaws. The chuck device 1 may include, for example, the same number of feed screw mechanisms as the number of master jaws. Also, in the above-described embodiment, the case where the chuck device 1 includes three centering portions 13A - 13B has been described. However, the chuck device 1 may include three or more centering portions. The chuck device 1 may include, for example, centering portions equal to or less than the number of master jaws.

[0053] For example, in the above-described embodiment, the case where the three centering portions 13A - 13C perform centering of the workpiece by contacting the outer peripheral surface of the workpiece has been described. However, the three centering portions 13A - 13C may perform centering of the workpiece by contacting the inner peripheral surface of the workpiece.

[0054] For example, in the above-described embodiment, the case where the chuck device 1 includes six clamping portions 14A - 14F has been described. However, the number of clamping portions is not particularly limited. The chuck device 1 may include at least two clamping portions.

Explanation of Reference Numerals

[0055] 1: Chuck device 11: Main body portion 12A - 12F: Master jaws 13A - 13C: Centering portions 131: Block member 1311: Seating surface 132: Contact member 14A - 14F: Clamping part 141: Base member 142: Moving member 143: Vice body 144: Inner claw part 145: Outer claw part 15: Feed screw mechanism 16: Fixing member 2: Rotating table W: Workpiece

Claims

1. A chuck device that is used in a machine tool and grips a cylindrical workpiece, comprising: a main body portion; at least three master jaws provided on the main body portion and each configured to be movable in the radial direction of a reference axis; a drive mechanism provided on the main body portion corresponding to the at least three master jaws and configured to move each of the at least three master jaws in conjunction with each other in the radial direction of the reference axis; at least three centering portions each attached to a corresponding one of the master jaws, moving together with the master jaw, and aligning the central axis of the workpiece with the reference axis by contacting the workpiece at at least three points; a plurality of clamping portions provided at positions displaced in the circumferential direction of the reference axis from the at least three master jaws and configured to clamp the inner peripheral surface and the outer peripheral surface of the workpiece after the central axis has been aligned with the reference axis by the at least three centering portions; a fixing structure provided between the clamping portion and the main body portion and configured to be capable of switching between a temporary fixing state in which the clamping portion is movable in the radial direction of the reference axis with the clamping portion clamping the inner peripheral surface and the outer peripheral surface of the workpiece, and a permanent fixing state in which the clamping portion is fixed to the main body portion with the clamping portion clamping the inner peripheral surface and the outer peripheral surface of the workpiece.

2. The chuck device according to claim 1, wherein the fixing structure comprises: a base member fixed to the main body portion; a moving member to which the clamping portion is fixed; an engaging structure formed between the base member and the moving member and configured to engage the moving member with the base member so as to be linearly movable; a fixing member for fixing the moving member to the base member or the main body portion, wherein each of the plurality of clamping portions comprises: an inner claw portion that contacts the inner peripheral surface of the workpiece; an outer claw portion provided on the moving member so as to be paired with the inner claw portion and that contacts the outer peripheral surface of the workpiece.

3. The chuck device according to claim 2, wherein the inner claw portion includes a spherical surface that contacts the inner peripheral surface of the workpiece, and the outer claw portion includes a spherical surface that contacts the outer peripheral surface of the workpiece.

4. The chuck device according to claim 2, wherein the fixing structure is provided for each of the plurality of clamping portions, and in each of the plurality of provided fixing structures, the fixing member is A chuck device that fixes the moving member to the main body by applying a force in a direction pressing the moving member against the main body.

5. The chuck device according to claim 1, wherein the plurality of clamping portions and / or the at least three centering portions are arranged at equal intervals in the circumferential direction of the workpiece, a chuck device.

6. The chuck device according to claim 1, wherein each of the at least three centering portions includes a contact member that aligns the central axis of the workpiece with the reference axis by contacting the inner circumferential surface or the outer circumferential surface of the workpiece, the contact member includes a curved surface that contacts the inner circumferential surface or the outer circumferential surface of the workpiece, a chuck device.

7. The chuck device according to claim 1, wherein each of the at least three centering portions includes a seating surface on which the end face portion of the workpiece is placed, the seating surface is provided at a position closer to the main body than the position where the plurality of clamping portions clamp the inner circumferential surface and the outer circumferential surface of the workpiece, a chuck device.

8. The chuck device according to claim 1, wherein the workpiece has a black skin on at least a part of the inner circumferential surface and / or the outer circumferential surface, a chuck device.

9. The chuck device according to claim 1, wherein the plurality of clamping portions are configured to be movable in the radial direction of the reference axis in the temporarily fixed state, so that when the workpiece is clamped, the radial positions of the plurality of clamping portions follow the position of the workpiece whose central axis is aligned with the reference axis, a chuck device.

10. A machine tool comprising the chuck device according to claim 1.

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