Chuck device

Abstract

To firmly grip a workpiece while suppressing strain generated in the workpiece in a chuck device for gripping the workpiece.SOLUTION: The chucking device 1 includes the main body 11, at least three master jaw 12A and 12F configured to be movable in the radial direction of the workpiece, at least three centering portions 13A and 13C configured to move together with the master jaws and come into contact with the workpiece to align the center axes of the workpiece with the reference position in the machine tool, a plurality of gripping portions 14A and 14F provided at positions shifted from the master jaw 12A and 12F in the circumferential direction of the workpiece and configured to grip the inner peripheral surface and the outer peripheral surface of the workpiece, and a plurality of fixing members configured to fix the corresponding gripping portions to the main body 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A scroll chuck is known as an example of a chuck device that secures a cylindrical workpiece to a machine tool. In a scroll chuck, a jaw is attached to each of three or more master jaws that move synchronously in the radial direction of the workpiece. The scroll chuck grips the workpiece by pressing each jaw against the outer circumferential surface of the workpiece by moving each master jaw. When the workpiece is machined, 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 with a large outer diameter or a thin wall thickness from the outer peripheral surface, the workpiece is likely to be significantly distorted and deformed. In this case, finishing processing is required to finish the workpiece to a specified machining accuracy, making it difficult to improve machining efficiency. On the other hand, if the scroll chuck loosely grips the workpiece, the workpiece is likely to move due to the machining load. As a result, it is difficult to perform the specified machining, and the workpiece is likely to vibrate during machining.

[0004] In contrast, Patent Document 1 discloses a chuck device that grips a cylindrical workpiece from both its inner and outer peripheral surfaces. In this chuck device, inner jaws that contact the inner peripheral surface of the workpiece and outer jaws that contact the outer peripheral surface of the workpiece are provided on a master jaw. The inner jaws are fixed to the master jaw and move radially along with the master jaw. The outer jaws are attached to the master jaw but are configured to move toward and away from the inner jaws. When gripping a workpiece with this chuck device, the inner and outer jaws are first separated, and the workpiece is placed between the inner and outer jaws. Next, the master jaw is moved radially outward from the workpiece, bringing all of the inner jaws into contact with the inner peripheral surface of the workpiece. This centers the workpiece. Next, the outer jaws are moved radially inward from the workpiece, bringing all of the outer jaws into contact with the outer peripheral surface of the workpiece. This clamps the workpiece between the inner and outer jaws. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 57-163003 Summary of the Invention [Problem to be solved by the invention]

[0006] The chuck device of Patent Document 1 clamps a workpiece from both its outer and inner peripheral surfaces. Therefore, compared to a scroll chuck, which applies a gripping force only from the outer peripheral surface, distortion of the workpiece is less likely to occur. However, in this chuck device, the inner and outer jaws are attached to a master jaw. The master jaw moves radially around the workpiece using a feed screw. Therefore, backlash exists between the master jaw and the feed screw. For example, suppose the inner and outer jaws are separated and a workpiece is placed between them. From this state, if the feed screw is operated to move the master jaw radially outward from the workpiece, the master jaw is pressed against the feed screw toward the radially outward direction of the workpiece. Meanwhile, a gap, i.e., backlash, occurs between the feed screw and the surface of the master jaw opposite the surface pressed against the feed screw. Even if the outer jaws are brought into contact with the outer peripheral surface of the workpiece and the workpiece is gripped between the inner and outer jaws, the master jaw can still move radially inward from the workpiece by the amount of backlash. To prevent the master jaw from rattling due to backlash, it is necessary to machine the workpiece while pressing the master jaw against the feed screw so that it faces outward in the radial direction of the workpiece. However, in this case, the inner jaws fixed to the master jaw are pressed strongly against the inner peripheral surface of the workpiece, which can still cause distortion in the workpiece.

[0007] An object of the present invention is to provide a chuck device for gripping a workpiece that can firmly grip the workpiece while suppressing distortion that occurs in 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; at least three master jaws provided on the main body, each configured to be movable radially along a reference axis; a drive mechanism provided on the main body corresponding to the at least three master jaws, for moving each of the at least three master jaws in conjunction with the radial direction of the reference axis; at least three centering units, each attached to the corresponding master jaw, moving together with the master jaw and contacting the workpiece at at least three points to align the central axis of the workpiece with the reference axis; a plurality of clamping units provided at positions offset from the at least three master jaws in the circumferential direction of the reference axis and clamping the inner and outer peripheral surfaces of the workpiece after the central axis has been aligned with the reference axis by the at least three centering units; and a fixing structure provided between the clamping units and the main body, capable of switching between a temporary fixing state in which the clamping units are movable radially along the reference axis and a final fixing state in which the clamping units are fixed to the main body.

[0009] The above-described chuck device includes a centering unit that performs workpiece centering and a clamping unit that clamps the workpiece. The centering unit is attached to a master jaw that moves via a feed screw mechanism, but the workpiece can be centered by simply lightly contacting the centering unit with the workpiece. Therefore, the centering unit does not need to be pressed firmly against the workpiece to offset backlash caused by the feed screw mechanism. On the other hand, the clamping unit must firmly clamp the workpiece to prevent it from moving due to the machining load. In the above-described chuck device, the clamping units are not attached to the master jaw that moves via the feed screw mechanism. Therefore, the clamping units can clamp the workpiece without being affected by backlash caused by the feed screw mechanism. Furthermore, each clamping unit clamps the workpiece by applying force from both the inner and outer peripheral surfaces of the workpiece. Therefore, the force applied to the workpiece by the clamping unit is reduced compared to when the workpiece receives force only from the outer peripheral surface or only from the inner peripheral surface. That is, the clamping portion is temporarily fixed by the fixing structure to clamp the inner and outer peripheral surfaces of the cylindrical workpiece centered relative to the reference axis. Since the clamping portion is movable radially relative to the reference axis, it naturally moves radially in accordance with the workpiece until it evenly clamps the inner and outer peripheral surfaces of the workpiece. The fixing structure then allows the clamping portion to be fixed to the support portion while being aligned with the centered workpiece. Therefore, the above-described chuck device allows the clamping portion to evenly clamp the inner and outer peripheral surfaces of the workpiece regardless of the diameter of the centered workpiece, thereby enabling the workpiece to be firmly gripped while suppressing distortion of 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 movable member to form a pair with the inner claw portion and contacts the outer peripheral surface of the workpiece, and the fixing structure may include a base member that is fixed to the main body portion, a movable member to which the clamping portions are fixed, an engagement structure that is formed between the base member and the movable member and engages the movable member so that it can move linearly relative to the base member, and a fixing member that fixes the movable member to the base member or the main body portion.

[0011] In the chuck device (2) described above, the fixing structure can be easily formed at any position on the main body. 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 clamping parts, the fixing structure can be easily added to each clamping part.

[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 the spherical surfaces from both the inner and outer peripheral sides, which essentially sandwiches the workpiece between points, allowing the clamping portion to firmly grip the workpiece.

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

[0015] For example, if the fastening member is a bolt, applying force to the corresponding clamping portion in the radial direction of the workpiece to fasten it tends to apply unnecessary radial force to the workpiece being gripped by the clamping portion. In contrast, in the chuck device of (4) above, the fastening member applies force in a direction different from the radial direction of the workpiece to fasten the clamping portion to the main body. Therefore, with the above chuck device, it is possible to firmly clamp the workpiece while suppressing distortion occurring in the workpiece.

[0016] (5) In the chuck device of (1) above, the plurality of clamping portions and / or the 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 (5) above, each clamping portion can stably clamp the workpiece, and the centering portion can accurately center the workpiece.

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

[0019] In the chuck device of (6) above, when centering a workpiece, the curved surface of the contact member contacts the workpiece at each centering portion. This allows the contact member to contact the workpiece essentially at a point. Therefore, each centering portion can center the workpiece with high precision and can contact the workpiece without applying unnecessary force.

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

[0021] For example, suppose the chuck device is placed on the table of a machine tool. In the chuck device described in (7) above, when a workpiece is attached to the chuck device placed on the table, the workpiece can be placed on the seating surfaces of the centering units. Furthermore, each seating surface is provided below (closer to the main body) the gripping positions of the clamping units. Therefore, the edge of the workpiece is positioned below the gripping positions, and the clamping units can grip the workpiece simply by moving in the radial direction of the workpiece. Therefore, the above chuck device improves the efficiency of the setup work for attaching the workpiece to the chuck device.

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

[0023] Steel workpieces are manufactured, for example, by forging or casting. The surface of the manufactured workpiece may develop an oxide film, i.e., black scale. Machine tools sometimes machine workpieces with the black scale remaining without removing it. The surface of a workpiece with black scale is rough. Therefore, for example, when a workpiece with black scale is clamped using a chuck device that applies a radially outward or inward force to the workpiece, the force at each clamping portion tends to vary, making the workpiece prone to distortion. In contrast, the above-described chuck device can firmly hold a workpiece without substantially applying a radially outward or inward force to the workpiece. Therefore, the above-described chuck device is particularly suitable for gripping workpieces with black scale.

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

[0025] When a workpiece has a thin wall thickness, the application of a radially outward or inward force to the workpiece can easily cause distortion. Furthermore, it is difficult for an operator to attach a large-diameter workpiece to a chuck device while performing centering. In contrast, the above-described chuck device can hold a workpiece without substantially applying a radially outward or inward force to the workpiece. Furthermore, since centering can be performed by moving each centering section radially, the operator simply places the workpiece temporarily in the chuck device, eliminating the need to attach it while performing centering. 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 with an outer diameter of 500 mm or more. A large-diameter, thin-walled workpiece is, for example, a workpiece with a wall 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, but it can also be used to grip workpieces other than large-diameter, thin-walled workpieces. [Effects of the Invention]

[0026] According to the machining system of the present invention, the chuck device that grips the workpiece can firmly grip the workpiece while suppressing distortion that occurs in the workpiece. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a perspective view of a chuck device. [Figure 2] FIG. 2 is a half-sectional view of the chuck device, schematically showing the feed screw mechanism. [Figure 3] FIG. 3 is an exploded perspective view of the clamping unit. [Figure 4] FIG. 4 is a diagram showing the chuck device and the workpiece as viewed in the direction of the central axis of the workpiece. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, an embodiment 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 in a machine tool to grip a cylindrical workpiece. In this embodiment, the machine tool is a vertical machining center (multitasking machine) that has a turning function in addition to a milling function. The machine tool may be a turning center that has only a turning function, or a machining center that has 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 mounted on a rotary table 2 in the machining chamber of the machine tool. The chuck device 1 includes a main body 11, six master jaws 12A-12F, three centering portions 13A-13C, and multiple clamping portions 14A-14F.

[0030] The main body 11 has a disk shape. The main body 11 includes a circular recess 111 in its center and a face plate formed around the recess 111 to which various devices are attached. The main body 11 is fixed on the rotary table 2 of the machine tool. The central axis of the main body 11 coincides or substantially coincides with the rotation axis of the rotary table 2. The main body 11 rotates together with the rotary table 2. The main body 11 forms the base of the chucking device 1 and is provided with the master jaws 12A-12F, the centering portions 13A-13C, and multiple clamping portions 14A-14F. When the chucking device 1 grips a workpiece, the reference axis CL, which coincides with the central axis of the main body 11, coincides or substantially coincides with the central axis of the workpiece. Therefore, the circumferential and radial directions of the main body 11 are synonymous with the circumferential and radial directions of the workpiece and the circumferential and radial directions of the reference axis CL. The reference axis CL is perpendicular to an imaginary plane including the face plate 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, unless otherwise specified, the following description will focus on one master jaw 12A. The master jaw 12A has a substantially rectangular parallelepiped shape. The master jaw 12A is provided so 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 so that at least a portion of its upper surface is exposed from the main body 11. The master jaw 12A is provided on the main body 11 so that it is 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 in the main body 11 corresponding to the master jaw.

[0032] 2 is a half-sectional view of the chuck device showing the feed screw mechanisms. The chuck device 1 of this embodiment includes six feed screw mechanisms, but since each feed screw mechanism has the same configuration, the following description will focus on one feed screw mechanism unless otherwise specified.

[0033] The feed screw mechanism 15 is provided within 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. The radially outer end of the feed screw mechanism 15 extends to a handle hole 112 provided on the side of the main body 11. The feed screw mechanism 15 rotates around the rotation axis by operating a chuck handle attached to the handle hole 112. The radially inner end of the feed screw mechanism 15 extends to a recess 111 in the main body 11. The radially inner end of the feed screw mechanism 15 is connected to the other feed screw mechanisms via an interlocking mechanism (not shown). As a result, the six feed screw mechanisms 15 rotate synchronously around their respective rotation axes. The feed screw mechanism 15 is connected to the corresponding master jaw 12 A. When the feed screw mechanism 15 rotates around the rotation axis, the master jaw 12 A moves in the radial direction of the main body 11.

[0034] Referring to FIG. 1, the three centering portions 13A-13C are 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, and 12F. The three centering portions 13A-13C each have the same configuration. Therefore, unless otherwise specified, the following description will focus on one centering portion 13A. 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 so that its longitudinal direction is along the radial direction of the main body 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 11 together with the master jaw 12A. The block member 131 is provided on its upper surface and includes a seating surface 1311 on which a workpiece is placed. The seating surface 1311 is provided on the upper surface of the block member 131 within a predetermined range from the radially inner end of the main body 11. 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 so that at least a portion thereof 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 11. As will be described later, the contact member 132 has a centering function of aligning the central axis of the workpiece with a reference position in the machine tool by coming into contact with the outer peripheral surface of the workpiece.

[0037] The reference position is a position that coincides with the central axis of rotation of the rotary table 2 in the machine tool when viewed from above. In other words, if the machine tool has a turning function, the reference position is a position defined by the rotation axis of the work spindle that rotates the workpiece. If the machine tool has only a milling function, the reference position is a control reference position of the tool spindle that holds the tool in the machine tool.

[0038] The multiple clamping portions 14A-14F are arranged side by side along the circumferential direction of the main body 11. The multiple clamping portions 14A-14F are arranged at equal intervals along the circumferential direction of the main body 11. Each of the multiple clamping portions 14A-14F is provided so as to face another clamping portion in the radial direction of the main body 11. Each of the multiple clamping portions 14A-14F is provided at a position offset in the circumferential direction of the main body 11 from the six master jaws 12A-12F of the main body 11. Each of the multiple clamping portions 14A-14F is provided between two circumferentially adjacent master jaws. Each of the multiple clamping portions 14A-14F is provided so as not to overlap with the six master jaws 12A-12F when viewed in the central axial direction of the main body 11. Each of the multiple clamping portions 14A-14F is not linked to the radial movement of the six master jaws 12A-12F. Each of the clamping sections 14A-14F is configured to be movable in the radial direction of the main body section 11 independently of the six master jaws 12A-12F. Each of the clamping sections 14A-14F is, for example, a centering vise.

[0039] FIG. 3(A) is an exploded view of the clamping unit as seen from diagonally above. Each of the clamping units 14A-14F has the same configuration. Therefore, unless otherwise specified, the following description will focus on one clamping unit 14A. The clamping unit 14A includes a vise body 143, an inner claw 144, and an outer claw 145. A fixing structure FA is provided between the clamping unit 14A and the main body 11. This fixing structure FA can switch between a temporary fixing state in which the clamping unit 14A is movable radially about the reference axis CL, and a fixed state in which the clamping unit 14A is fixed to the main body 11.

[0040] The base member 141 is fixed to the main body 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 11. A moving member 142 is attached to the top of the base member 141.

[0041] FIG. 3(B) is an exploded view of the clamping unit as viewed obliquely from below. The moving member 142 has a plate shape. The moving member 142 includes multiple protrusions 1421 protruding from its underside. The multiple protrusions 1421 are arranged side by side in the radial direction of the main body 11. The multiple protrusions 1421 are configured to fit within the guide rails 1411. The multiple protrusions 1421, together with the guide rails 1411, regulate the moving direction of the moving member 142. With this configuration, the moving member 142 is configured to be movable relative to the main body 11 in the radial direction of the main body 11. The moving member 142 includes two elongated holes 1422 for inserting the fixing members 16, which will be described later. Each elongated hole 1422 extends in the radial direction of the main body 11. A vise body 143 is provided on the moving member 142.

[0042] Referring to FIG. 3(A), the vise body 143 is fixed to the moving member 142. The vise body 143 supports the inner claws 144 and the outer claws 145 via a feed mechanism 146. The inner claws 144 are provided facing the outer claws 145 in the radial direction of the body 11. The inner claws 144 and the outer claws 145 are provided in pairs. The feed mechanism 146 is configured with, for example, a feed screw. The feed mechanism 146 extends in the radial direction of the body 11. The feed mechanism 146 operates a head 1461 provided at its end to move the inner claws 144 and the outer claws 145 in the radial direction of the body 11 relative to the vise body 143 (moving member 142). The feed mechanism 146 has a reverse thread in a portion responsible for moving the inner claws 144 and a portion responsible for moving the outer claws 145. As a result, by operating the head portion 1461, the inner claw portion 144 and the outer claw portion 145 can be moved closer to or farther away from each other in the radial direction of the main body portion 11.

[0043] The outer claw portion 145 includes a spherical bolt 1451 that protrudes 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. The radius of curvature of the spherical surface is preferably smaller than the radius of the workpiece. The head of the spherical bolt 1451 is located above the seating surfaces 1311 of each of the centering portions 13A-13C. The inner claw portion 144 is configured in a similar manner.

[0044] The chuck device 1 further includes two fixing members 16 that fix the movable member 142 to the base member 141. Because the two fixing members 16 have the same configuration, the following description will focus on one fixing member 16 unless otherwise specified. The fixing member 16 is, for example, a bolt. The fixing member 16 makes the movable member 142 movable and immovable relative to the main body 11. When the fixing member 16 is inserted into the elongated hole 1422 and not fastened, the movable member 142 is movable relative to the base member 141 (main body 11). When the fixing member 16 is inserted into the elongated hole 1422 and fastened, the movable member 142 is fixed to the base member 141. In other words, the movable member 142 is immovable relative to the main body 11. The fixing member 16 also fixes the movable member 142 to the base member 141 by applying a force in a direction different from the radial direction of the main body 11. The fixed member 16 fixes the moving member 142 to the main body 11 by applying a force in a direction that presses the moving member 142 against the base member 141 (main body 11).

[0045] In this embodiment, a configuration has been described in which two fixing members 16 fix the clamping portion 14A to the main body portion 11. The same applies to the remaining five clamping portions 14B-14F. Also, in this embodiment, 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] Next, a method for gripping a workpiece using the chuck device 1 of this embodiment will be described.

[0047] FIG. 4 shows the chucking device and workpiece as viewed in the direction of the workpiece's central axis. First, the chucking device 1 is placed and secured on the rotary table 2 of the machine tool. Next, the workpiece W is placed on the three centering units 13A-13C. In this state, the workpiece W is supported by the seating surfaces 1311 of the three centering units 13A-13C and positioned between the inner claws 144 and outer claws 145 of each of the clamping units 14A-14F. Next, the master jaws 12A, 12C, and 12E are moved to move each of the three centering units 13A-13C radially inward of the workpiece W, bringing the contact members 132 of each centering unit into contact with the outer peripheral surface of the workpiece W. At this time, each of the three centering units 13A-13C contacts the outer peripheral surface of the workpiece W in a manner that does not, or substantially does not, cause distortion in the workpiece W. As a result, the central axis of the workpiece W coincides with the reference position (the rotation axis of the rotary table 2) in the machine tool, and so-called centering work is completed.

[0048] Next, in the clamping unit 14A, the fixed member 16 is inserted into the movable member 142, and the movable member 142 is temporarily fixed to the base member 141. In this state, the fixed member 16 does not completely fix the movable member 142 to the base member 141, and the movable member 142 is movable in the radial direction of the workpiece W. Next, in the clamping unit 14A, the workpiece W is clamped between the inner claw portion 144 and the outer claw portion 145. Next, the fixed member 16 is fastened, and the movable member 142 is completely fixed to the base member 141. The same is true for the remaining clamping units 14B-14F. As a result, the workpiece W is gripped by the chuck device 1 and is ready for processing.

[0049] As described above, the chuck device 1 of this embodiment is provided with separate centering units 13A-13C for centering the workpiece W and clamping units 14A-14F for clamping the workpiece W. The centering units 13A-13C are attached to the master jaws 12A, 12C, and 12E, respectively. However, the centering operation of the workpiece can be performed by simply lightly contacting the centering units 13A-13C with the workpiece. Therefore, the centering units 13A-13C do not need to be pressed firmly against the workpiece W to offset rattles caused by backlash in the feed screw mechanism 15. On the other hand, the clamping units 14A-14F are not attached to any of the master jaws 12A-12F. Therefore, the clamping units 14A-14F can clamp the workpiece without being affected by backlash in the feed screw mechanism. Moreover, each of the clamping portions 14A-14F clamps the workpiece by applying force from both the inner and outer peripheral surfaces of the workpiece using the inner claw portion 144 and the outer claw portion 145. Therefore, the force applied to the workpiece by the clamping portion is reduced compared to when the workpiece receives force only from the outer peripheral surface or only from the inner peripheral surface. In this way, with the chuck device 1, radial force is less likely to be applied to the workpiece W during both the centering and gripping of the workpiece W. Therefore, with the above-mentioned chuck device, it is possible to firmly grip the workpiece while suppressing distortion of the workpiece.

[0050] The chuck device 1 is particularly effective when the workpiece to be gripped is a large-diameter, thin-walled workpiece. In other words, large-diameter, thin-walled workpieces are prone to distortion due to the radial force applied. When distortion occurs in a large-diameter, thin-walled workpiece, it is necessary to perform corrective machining to adjust the dimensions of the machined workpiece, making it difficult to improve machining efficiency. One way to prevent this is to reduce the gripping force of the chuck device, but this can easily cause the workpiece to move or vibrate during machining. In contrast, the chuck device 1 of this embodiment can firmly grip the workpiece while suppressing distortion in the workpiece. Therefore, even when the workpiece to be gripped is a large-diameter, thin-walled workpiece, desired machining can be performed, improving machining efficiency.

[0051] The above-described embodiments are illustrative in all respects and are not limiting. Modifications and variations are possible for those skilled in the art. The scope of the present invention is defined not by the above-described embodiments but by the claims. Furthermore, the scope of the present invention includes modifications from the embodiments within the scope of the claims and their equivalents.

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

[0053] For example, in the above embodiment, the three centering parts 13A-13C are in contact with the outer peripheral surface of the workpiece to center the workpiece. However, the three centering parts 13A-13C may be in contact with the inner peripheral surface of the workpiece to center the workpiece.

[0054] For example, in the above embodiment, the chucking device 1 includes six clamping portions 14A-14F. However, the number of clamping portions is not particularly limited. The chucking device 1 only needs to include at least two clamping portions. [Explanation of symbols]

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

Claims

1. A chuck device used in a machine tool to grip a cylindrical workpiece, a main body; At least three master jaws provided on the main body portion, each configured to be movable in a radial direction of a reference axis; a drive mechanism provided on the main body portion corresponding to the at least three master jaws, the drive mechanism moving each of the at least three master jaws in a radial direction of the reference axis in conjunction with each other; At least three centering units, each of which is attached to a corresponding one of the master jaws, moves together with the master jaw, and contacts the workpiece at at least three points to align the central axis of the workpiece with the reference axis; a plurality of clamping portions provided at positions shifted from the at least three master jaws in the circumferential direction of the reference axis, and configured to clamp the inner and outer peripheral surfaces of the workpiece after the central axis is aligned with the reference axis by the at least three centering portions; A chuck device comprising: a fixing structure provided between the clamping portion and the main body portion, capable of switching 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.

2. 2. The chuck device according to claim 1, Each of the plurality of clamping units includes: an inner claw portion that contacts the inner peripheral surface of the workpiece; an outer claw portion provided on the moving member to form a pair with the inner claw portion and contacting the outer peripheral surface of the workpiece; The fixing structure includes: a base member fixed to the main body; a moving member to which the clamping unit is fixed; an engagement structure formed between the base member and the moving member, which engages the moving member with the base member so as to be linearly movable; a fixing member that fixes the moving member to the base member or the main body portion.

3. 3. The chuck device according to claim 2, The inner claw portion is a spherical surface that contacts the inner circumferential surface of the workpiece; The outer claw portion is A chuck device including a spherical surface that contacts the outer peripheral surface of the workpiece.

4. 3. The chuck device according to claim 2, Each of the plurality of fixing members is A chuck device that fixes the corresponding moving member to the main body portion by applying a force in a direction pressing the moving member against the main body portion.

5. 2. The chuck device according to claim 1, The plurality of clamping portions and / or the at least three centering portions are Chuck devices arranged at equal intervals around the circumference of the workpiece.

6. 2. The chuck device according to claim 1, Each of the at least three centering portions comprises: a contact member that contacts an inner peripheral surface or an outer peripheral surface of the workpiece to align a central axis of the workpiece with the reference axis line; The contact member is A chuck device including a curved surface that contacts the inner or outer peripheral surface of the workpiece.

7. 2. The chuck device according to claim 1, Each of the at least three centering portions comprises: a seating surface on which an end surface of the workpiece is placed, The seating surface is A chuck device in which the multiple clamping portions are provided at positions closer to the main body portion than positions at which the clamping portions clamp the inner and outer peripheral surfaces of the workpiece.

8. 2. The chuck device according to claim 1, The workpiece is A chuck device having a black scale on at least a portion of the inner circumferential surface and / or the outer circumferential surface.

9. 2. The chuck device according to claim 1, The workpiece is A chuck device for large diameter thin-walled workpieces.

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