JP2017177249A - Workpiece gripping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a workpiece gripping device which can satisfactorily grip a workpiece.SOLUTION: A workpiece gripping device comprises a gripping part 11C, a push rod 12, and a mandrel 14. The gripping part 11C is cylindrical, and has a second inclined plane 11G which is provided on an inner periphery of a left end part and is inclined toward a left end in a direction separating from a central axis, and a first inclined plane 11H which is provided on an inner periphery of a right end part and is inclined toward a right end in a direction separating from the central axis. The gripping part 11C is inserted in a cylindrical workpiece W. An outer periphery of a right end part of the cylindrical push rod 12 expands the gripping part 11C in a direction separating from the central axis via the second inclined plane 11G. A left end part of the columnar mandrel 14 is inserted in the workpiece W so as to face the right end part of the push rod 12, and an outer periphery thereof expands the gripping part 11C in a direction separating from the central axis via an inner periphery of the workpiece W while centering the workpiece W.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a workpiece gripping device.

  Patent Document 1 discloses a conventional workpiece gripping device. In this work gripping device, the base end of a cylindrical collet chuck is coaxially connected to a cylindrical spindle stock. The collet chuck is provided with a cylindrical collet portion coaxially with the collet chuck at the tip. The collet chuck is provided with a cylindrical actuating rod at the center. The headstock is arranged with a cylindrical pressing rod inserted through the center. One end of the pressing rod faces the other end of the operating rod. The other end of the pressing rod is connected to the forward / backward drive cylinder. In this workpiece gripping device, first, the collet portion is inserted into one end of a cylindrical workpiece. Then, the advance / retreat drive cylinder pushes the pressing rod toward the tip side of the collet chuck. Then, the operating rod is pushed by the pressing rod and pushed toward the collet portion of the collet chuck. As a result, the chuck portion is expanded by the operating rod. A tailstock center is in contact with the other end of the cylindrical workpiece. Thus, the workpiece gripping device can grip a cylindrical workpiece. However, since this workpiece gripping device cannot grip the central portion of the cylindrical workpiece in the longitudinal direction, chattering occurs when machining the outer peripheral surface of the longitudinal center portion of the workpiece, and the workpiece is excellent. There is a risk that it cannot be processed.

  Patent Document 2 discloses another conventional workpiece gripping device. This workpiece gripping device can center and grip a workpiece with respect to the mandrel bar by inserting a columnar mandrel bar into a cylindrical workpiece. That is, this workpiece gripping device can grip the center portion of the workpiece in the longitudinal direction with certainty.

  By replacing the tailstock center of the workpiece gripping device of Patent Document 1 with a mandrel bar, chattering and the like when processing the outer peripheral surface of the central portion in the longitudinal direction of the workpiece can be suppressed. In this case, a columnar mandrel bar is inserted into the cylindrical workpiece from the other end of the cylindrical workpiece. At this time, it is necessary to position the tip of the inserted mandrel bar in the central axis direction. For this reason, the tip of the mandrel bar comes into contact with one end, is inserted through the center of the chuck part, and is provided with a receiving part with which the other end of the operating rod comes into contact with the other end to receive the thrust of the mandrel bar with the rod through the receiving part Can be considered. By doing so, even if the mandrel bar is inserted into the workpiece, the mandrel bar can be positioned in the central axis direction without the tip of the mandrel bar hindering the operation of the chuck portion.

Japanese Utility Model Publication No. 55-129739 JP 2001-212606 A

  However, since the workpiece gripping device receives the thrust of the mandrel bar by the rod through the receiving portion, the operating rod may be pushed back in the direction of the forward / backward drive cylinder. As a result, the workpiece gripping device may not be able to grip the workpiece by moving the chuck portion that is spread by the operating rod in a direction approaching the central axis.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a workpiece gripping device that can grip a workpiece satisfactorily.

  The workpiece gripping device of the present invention includes a gripping member, a first pressing member, and a second pressing member. This workpiece gripping device grips the inner periphery of a cylindrical workpiece. The gripping member has a cylindrical shape extending in the central axis direction. The first inclined surface is provided on the inner periphery of one end of the grip member, and is inclined in a direction away from the central axis toward the one end. The second inclined surface is provided adjacent to the first inclined surface, and is inclined in a direction away from the central axis toward the other end. The gripping member is inserted into the cylindrical workpiece. The first pressing member extends in the central axis direction, and the outer periphery of the tip portion widens the gripping member in a direction away from the central axis via the first inclined surface. The second pressing member extends in the central axis direction, the distal end portion is arranged to face the distal end portion of the first pressing member, and the outer periphery of the distal end portion widens the gripping member in a direction away from the central axis via the second inclined surface. .

  The workpiece gripping device widens the gripping member in a direction away from the central axis by the first pressing member and the second pressing member. As a result, in this work gripping device, the outer periphery of the gripping member is uniformly expanded in diameter in the central axis direction, so that the entire outer periphery of the gripping member can be uniformly pressed against the inner periphery of the work. For this reason, a workpiece | work can be hold | gripped more uniformly using the thrust of the 1st press member which opposes the thrust of a 2nd press member.

  Therefore, the workpiece gripping device of the present invention can grip the workpiece satisfactorily.

  The first pressing member of the present invention may be a centering member that centers the workpiece by contacting the inner periphery of the workpiece. In this case, the workpiece gripping device can expand the diameter of the gripping member by using the thrust inserted into the workpiece of the centering member facing the thrust of the second pressing member. As a result, the workpiece gripping device can simultaneously center and grip the workpiece without wasting thrust for inserting the centering member into the workpiece.

  The workpiece gripping device of the present invention is provided between the tip of the first pressing member and the gripping member, and the third inclined surface that contacts the first inclined surface and the tip of the first pressing member are in contact with each other. And a cylindrical portion that is movable in the central axis direction. In this case, the workpiece gripping device has a contact portion interposed between the centering member and the gripping member. That is, in this work gripping device, the centering member and the gripping member do not come into contact with each other, so that the gripping member is not damaged by the centering member. This workpiece gripping device can protect the gripping member with the cylindrical portion by providing the cylindrical portion between the tip portion of the first pressing member and the gripping member. For this reason, if the cylindrical part is damaged by the centering member, it is only necessary to replace only the cylindrical part, not the entire apparatus. That is, this work gripping device can facilitate maintenance.

  The 1st press member of this invention can comprise a 4th inclined surface. The fourth inclined surface is inclined in a direction in which the distal end portion of the first pressing portion approaches the central axis toward the distal end, and comes into contact with the contact portion. In addition, the inclination angle of the third inclined surface with respect to the central axis can be smaller than the inclination angle of the fourth inclined surface with respect to the central axis. In this case, a larger surface pressure can be applied to the third inclined surface than when there is no angular difference between the third inclined surface and the fourth inclined surface. For this reason, this work gripping apparatus can grip a work more reliably.

It is an end view which shows the workpiece | work holding apparatus of Embodiment 1. It is the side view which looked at the workpiece holding device of Embodiment 1 from the right side. It is an end view which shows the state which inserted the mandrel in the workpiece | work attached to the workpiece holding apparatus of Embodiment 1. FIG. It is an end view which shows the state which inserted the mandrel in the workpiece | work attached to the workpiece | work holding apparatus of Embodiment 1, and made the left end part of the mandrel contact the contact part of a cylindrical part.

<Embodiment 1>
As shown in FIG. 1, the workpiece gripping apparatus according to the first embodiment includes a drive unit 10, a collet 11, a push rod 12 that is a second pressing member, a cylindrical portion 13, and a first pressing member (centering member). A mandrel 14 is provided. This workpiece gripping device can grip the workpiece W while centering it.

  The drive unit 10 includes a cylinder 10A, a piston 10B, and a closing unit 10C. The cylinder 10A has a cylindrical shape and extends in the left-right direction. The cylinder 10 </ b> A is provided with a first protrusion 10 </ b> D that extends in a direction approaching the central axis at the left end of the inner periphery. The cylinder 10A is provided with a flow path 10E. One end of the channel 10E is provided on the cylindrical left end surface of the cylinder 10A, and the other end is provided on the left and right intermediate portion of the inner peripheral surface of the cylinder 10A.

  The piston 10B has a cylindrical shape and extends in the left-right direction. The piston 10B is provided with a first flange 10F extending in a direction away from the central axis at the right end of the outer periphery. The piston 10B is provided with a second projecting portion 10G projecting in a direction approaching the central axis at the right end portion of the inner periphery. In the piston 10B, the outer periphery of the first flange portion 10F is in contact with the right end portion of the inner periphery of the cylinder 10A. The piston 10B is in contact with the inner periphery of the first protrusion 10D of the cylinder 10A at the left end of the outer periphery. In this way, the drive unit 10 forms a space 10H surrounded by the inner periphery of the cylinder 10A, the right side of the first protrusion 10D, the outer periphery of the piston 10B, and the left side of the first flange 10F. The other end of the flow path 10E of the cylinder 10A communicates with the space 10H.

  The closing portion 10C has a disk shape. The closing portion 10C abuts the disc-shaped left surface against the right end surface of the cylinder 10A. The closing portion 10C is connected to the cylinder 10A by a plurality of bolts 10J. The closing part 10C is penetrated in the left-right direction in the center part of disk shape, and the insertion hole 10K is provided.

  The collet 11 has a cylindrical shape and extends in the left-right direction. The collet 11 includes a first base portion 11A, a flexure portion 11B, and a grip portion 11C that is a grip member. 11 A of 1st base parts are provided with 2nd collar part 11D extended in the direction away from a central axis in the left end part of outer periphery. The first base portion 11A is provided with a first step portion 11E having an outer diameter smaller than the outer diameter of the second flange portion 11D adjacent to the right side of the second flange portion 11D. The first base portion 11A is provided with a second step portion 11F having an outer diameter smaller than the outer diameter of the first step portion 11E adjacent to the right side of the first step portion 11E.

  The bending portion 11B extends in the right direction from the right end of the first base portion 11A. The outer diameter of the bent portion 11B is smaller than the outer diameter of the first base portion 11A. The inner diameter of the bending portion 11B is slightly larger than the inner diameter of the first base portion 11A. The grip portion 11C extends in the right direction from the right end of the bending portion 11B. The grip portion 11C has an outer diameter slightly larger than the outer diameter of the bending portion 11B and smaller than the outer diameter of the first base portion 11A. The inner diameter of the grip portion 11C is smaller than the inner diameter of the first base portion 11A. The holding portion 11C is provided with a first inclined surface 11H on the right side of the inner periphery. The first inclined surface 11H is inclined in a direction away from the central axis toward the right end of the grip portion 11C. The first inclined surface 11H has an inclination angle with respect to the central axis of the collet 11 of 15 degrees. The grip portion 11C is provided with a second inclined surface 11G on the left side of the inner periphery. The second inclined surface 11G is inclined in a direction away from the central axis toward the left end of the grip portion 11C. The inclination angle of the second inclined surface 11G with respect to the central axis of the collet 11 is 10 degrees. Between the left end of the first inclined surface 11H and the right end of the second inclined surface 11G, an inner peripheral surface that is parallel to the outer peripheral surface of the grip portion 11C is provided. That is, the first inclined surface 11H and the second inclined surface 11G are separated from each other. The gripper 11C is knurled on the outer periphery. That is, the grip portion 11C has a cylindrical shape extending in the central axis direction, is provided on the inner periphery of one end portion, and is inclined in the direction away from the central axis toward the one end portion. The second inclined surface 11G is provided adjacent to the first inclined surface 11H and is inclined in the direction away from the central axis toward the other end.

  The collet 11 is provided with four slits 11J in the bent portion 11B and the grip portion 11C in parallel to the central axis (see FIG. 2). These slits 11J are provided from the left end of the bending portion 11B to the right end of the gripping portion 11C. These slits 11J divide the bent portion 11B and the grip portion 11C into four equal parts in the circumferential direction. The collet 11 abuts the right surface of the second collar portion 11D against the left surface of the closing portion 10C of the drive unit 10. In the collet 11, the outer periphery of the first step portion 11E is in contact with the inner periphery of the insertion hole 10K of the closing portion 10C, and the second step portion 11F, the bending portion 11B, and the gripping portion 11C are located on the right side of the closing portion 10C. ing. The collet 11 is provided with an annular member 11K having an annular shape on the outer periphery of the second step portion 11F. The annular member 11K penetrates in the radial direction on the outer periphery and is provided with four screw holes 11L. The annular member 11K is in contact with the outer periphery of the second step portion 11F of the collet 11 at the inner periphery, and the left surface is in contact with the right surface of the closing portion 10C. In the annular member 11K, a bolt 11M is screwed into each of the four screw holes 11L, and the tip of the bolt 11M is in contact with the outer periphery of the second step portion 11F. Thus, the collet 11 is connected to the closing portion 10 </ b> C of the driving unit 10.

  Further, the collet 11 is provided with a cylindrical member 11N on the outer periphery. The cylinder member 11N includes a first cylinder part 11P and a second cylinder part 11Q. The first cylinder portion 11P has a cylindrical shape and extends in the left-right direction. The first cylinder portion 11P penetrates in the left-right direction and is provided with eight bolt insertion holes 11R. These bolt insertion holes 11R are arranged on the same circumference of the cylindrical end surface of the first cylinder portion 11P. These bolt insertion holes 11R are equal in size between adjacent ones (see FIG. 2). The first cylinder portion 11P is in contact with the right surface of the second step portion 11F of the collet 11 at the left end surface. Further, the first cylinder portion 11P is in contact with the right end portion of the outer periphery of the first base portion 11A of the collet 11 at the inner periphery. The second cylinder portion 11Q has a cylindrical shape and extends in the right direction from the right end portion of the inner periphery of the first cylinder portion 11P. The right end of the second tube portion 11Q extends to the left end portion of the grip portion 11C of the collet 11. The second cylinder portion 11Q has a slightly larger inner diameter than the outer diameter of the grip portion 11C of the collet 11. In the cylindrical member 11N, the bolt 11S is inserted into each of the eight bolt insertion holes 11R. These bolts 11S are screwed into screw holes 11T provided in the second step portion 11F of the collet 11. Thus, the cylindrical member 11N is connected to the collet 11 by the bolt 11S.

  The push rod 12 includes a second base portion 12A and a cylindrical portion 12B. The second base 12A has a cylindrical shape and extends in the left-right direction. The second base portion 12A is provided with a third flange portion 12C extending in the direction away from the central axis at the left end portion of the outer periphery. The third collar portion 12C is provided with a convex portion 12D extending in the direction away from the central axis on the right side of the outer periphery. The cylindrical portion 12B has a cylindrical shape and extends rightward from the right end of the second base portion 12A. The cylindrical portion 12B includes a fifth inclined surface 12E that is inclined in a direction approaching the central axis toward the right end at a right end portion that is a distal end portion of the outer periphery. The push rod 12 has a second base portion 12 </ b> A and a cylindrical portion 12 </ b> B inserted into the collet 11. In the push rod 12, the fifth inclined surface 12E is in surface contact with the second inclined surface 11G of the grip portion 11C of the collet 11. The push rod 12 abuts the left surface of the convex portion 12D on the right surface of the second projecting portion 10G of the piston 10B, and is connected to the piston 10B by a plurality of bolts 12F.

  The cylindrical portion 13 includes a shaft portion 13A and a contact portion 13B. The shaft portion 13A has a cylindrical shape and extends in the left-right direction. The shaft portion 13A has the same outer diameter as the inner diameter of the cylindrical portion 12B of the push rod 12. 13 A of shaft parts are provided with the 3rd protrusion part 13C which protruded in the direction approaching a center axis | shaft in the left-right center part of inner periphery. The abutting portion 13B is provided at the right end portion, which is the distal end portion of the outer periphery of the shaft portion 13A, so as to protrude in a hook shape in a direction away from the central axis. That is, the contact portion 13B is provided on the outer periphery of the right end portion of the shaft portion 13A. The contact portion 13B is provided with a third inclined surface 13D that is inclined in a direction away from the central axis as the outer periphery thereof toward the right end. The contact portion 13B is provided with a sixth inclined surface 13E that is inclined in a direction away from the central axis toward the right end at the right end portion of the inner periphery. The sixth inclined surface 13E has an inclination angle of 30 degrees with respect to the central axis of the cylindrical portion 13.

  The cylindrical portion 13 is inserted into the cylindrical portion 12B of the push rod 12 with the shaft portion 13A on the left side and the contact portion 13B on the right side. Thus, the cylindrical portion 13 forms a space R surrounded by the left surface of the third projecting portion 13C, the inner peripheral surface of the shaft portion 13A, and the right surface of the second base portion 12A. In the cylindrical portion 13, the third inclined surface 13 </ b> D is in surface contact with the first inclined surface 11 </ b> H of the collet 11. That is, the shaft portion 13 </ b> A of the cylindrical portion 13 is inserted through the grip portion 11 </ b> C of the collet 11 and the push rod 12. In the cylindrical portion 13, a gap is provided between the left end surface of the shaft portion 13 </ b> A and the right end surface of the second base portion 12 </ b> A of the push rod 12. In the cylindrical portion 13, a gap is provided between the left surface of the contact portion 13 </ b> B and the right end surface of the cylindrical portion 12 </ b> B of the push rod 12. The cylindrical portion 13 has a bolt 13F inserted through the third protruding portion 13C. The bolt 13F is screwed into a screw hole 12G provided in the right end portion of the second base portion 12A of the push rod 12. Thereby, it can prevent that the cylindrical part 13 falls off from 12 A of 2nd base parts. Further, the bolt 13F has a seating surface at the head separated from the right end surface of the third projecting portion 13C of the cylindrical portion 13 in the right direction. Thereby, the cylindrical part 13 is movable in the left-right direction with respect to the cylindrical part 12B of the push rod 12. That is, the cylindrical portion 13 has a cylindrical shape and is movable in the central axis direction. Further, the cylindrical portion 13 does not fall off from the cylindrical portion 12B of the push rod 12. The cylindrical portion 13 is provided with a buffer member 13G in the space R. The buffer member 13G is a compression coil spring. One end of the buffer member 13G is connected to the left surface of the third protruding portion 13C of the cylindrical portion 13. The other end of the buffer member 13G is connected to the right surface of the second base portion 12A of the push rod 12.

  The mandrel 14 has a columnar shape and extends in the left-right direction. The mandrel 14 has a central axis disposed on the central axis of the collet 11. The mandrel 14 has a left end portion, which is a tip portion, facing the right end portion of the abutting portion 13B of the cylindrical portion 13. The mandrel 14 includes a fourth inclined surface 14A that is inclined in a direction approaching the central axis toward the left end at the left end portion of the outer periphery. The inclination angle of the fourth inclined surface 14A with respect to the central axis is 30 degrees, which is the same as the inclination angle of the sixth inclined surface 13E of the cylindrical portion 13 with respect to the central axis. That is, the inclination angle of the cylindrical portion 13 with respect to the central axis of the third inclined surface 13D is smaller than the inclination angle of the mandrel 14 with respect to the central axis of the fourth inclined surface 14A.

  In the gripping state where the mandrel 14 grips the workpiece W, the fourth inclined surface 14A comes into surface contact with the sixth inclined surface 13E of the cylindrical portion 13 (see FIG. 4). That is, the mandrel 14 includes a fourth inclined surface that is inclined in a direction in which the tip portion approaches the center axis toward the tip and comes into contact with the contact portion 13B of the tubular portion 13. Further, the mandrel 14 is disposed on the right side of the cylindrical portion 13 without the fourth inclined surface 14 </ b> A contacting the sixth inclined surface 13 </ b> E of the cylindrical portion 13 in a non-holding state where the workpiece W is not gripped.

  Next, the operation of the workpiece gripping device will be described with reference to FIGS.

  First, the workpiece W is attached to the apparatus. Specifically, as shown in FIG. 3, the workpiece W is inserted from the right side of the collet 11 to the left side through the outer periphery of the grip portion 11 </ b> C of the collet 11. Then, the left end surface of the workpiece W is brought into contact with the right end surface of the second cylindrical portion 11Q of the cylindrical member 11N. That is, the holding part 11C of the collet 11 is inserted into the cylindrical workpiece W.

  Next, the push rod 12 is moved rightward. Specifically, the hydraulic oil is caused to flow into the space 10H of the drive unit 10 through the flow path 10E (see FIG. 1). Then, the space 10H is expanded by the hydraulic oil flowing into the space 10H, and the piston 10B moves in the right direction. Then, the push rod 12 also moves in the right direction together with the piston 10B. Then, the fifth inclined surface 12E of the cylindrical portion 12B of the push rod 12 presses the second inclined surface 11G of the collet 11. Thereby, the bending part 11B of the collet 11 is bent and the gripping part 11C moves in a direction away from the central axis. In other words, the outer periphery of the right end of the push rod 12 abuts on the second inclined surface 11G of the gripping part 11C of the collet 11 to widen the gripping part 11C of the collet 11 away from the central axis. Then, the outer periphery of the grip portion 11C is pressed against the inner periphery of the workpiece W. Thus, the gripping part 11C of the collet 11 grips the workpiece W. At this time, while the piston 10B is always pushed rightward by the hydraulic oil flowing into the space 10H, the fifth inclined surface 12E of the cylindrical portion 12B of the push rod 12 is changed to the second inclined surface 11G of the holding portion 11C of the collet 11. Press and hold.

  Next, the mandrel 14 is inserted into the workpiece W. Specifically, the mandrel 14 is inserted from the right side of the workpiece W. The outer diameter of the mandrel 14 is the same as the inner diameter of the workpiece W. That is, the outer periphery of the mandrel 14 abuts on the inner periphery of the workpiece W to center the workpiece W. Then, as shown in FIG. 4, the fourth inclined surface 14 </ b> A of the mandrel 14 is in surface contact with the sixth inclined surface 13 </ b> E of the tubular portion 13. At this time, the buffer member 13G provided in the space R softens the impact when the fourth inclined surface 14A of the mandrel 14 comes into surface contact with the sixth inclined surface 13E of the cylindrical portion 13. Further, by pushing the mandrel 14 leftward, the cylindrical portion 13 is pushed leftward. Then, the buffer member 13G is pushed leftward via the third projecting portion 13C of the cylindrical portion 13 and contracts. Then, the third inclined surface 13 </ b> D of the cylindrical portion 13 presses the first inclined surface 11 </ b> H of the gripping portion 11 </ b> C of the collet 11. At this time, while the cylindrical portion 13 is being pushed leftward by the mandrel 14, the third inclined surface 13D of the cylindrical portion 13 continues to push the first inclined surface 11H of the gripping portion 11C of the collet 11. At this time, the contact portion 13B is interposed between the left end portion of the mandrel 14 and the grip portion 11C of the collet 11. The contact portion 13B is provided between the tip portion of the mandrel 14 and the grip portion 11C, and the third inclined surface 13D that contacts the first inclined surface 11H and the tip portion of the mandrel 14 contact each other. Thereby, the bending part 11B of the collet 11 is bent and the gripping part 11C moves in a direction away from the central axis. That is, the outer periphery of the mandrel 14 widens the gripping portion 11C of the collet 11 away from the central axis via the first inclined surface 11H. Then, the outer periphery of the grip portion 11C is pressed against the inner periphery of the workpiece W. Thus, the workpiece gripping device grips the workpiece W while centering the workpiece W.

  Next, the workpiece W is removed from the apparatus. First, the mandrel 14 inserted from the right side of the workpiece W is moved in the right direction. Then, the cushioning member 13G that is pressed and contracted to the left via the third projecting portion 13C of the cylindrical portion 13 expands and pushes the cylindrical portion to the right. That is, the buffer member 13G can return the position of the cylindrical portion 13 to the position before the mandrel 14 is inserted. Then, the mandrel 14 is extracted from the work W. Then, the hydraulic oil is extracted from the space 10H of the drive unit 10. Then, the piston 10B moves in the left direction. Then, the push rod 12 also moves leftward together with the piston 10B. Then, the fifth inclined surface 12E of the cylindrical portion 12B of the push rod 12 is separated from the second inclined surface 11G of the collet 11. Then, the grip portion 11C moves in a direction approaching the central axis. Thus, the outer periphery of the gripping portion 11C is separated from the inner periphery of the workpiece W. Thus, the workpiece gripping device releases the gripping of the workpiece W. Thus, the workpiece gripping device can remove the workpiece W from the device.

  As described above, the workpiece gripping device widens the gripping portion 11 </ b> C in the direction away from the central axis by the push rod 12 and the mandrel 14. As a result, in the workpiece gripping device, the outer periphery of the gripping portion 11C is expanded evenly over the entire center axis direction, so that the entire outer periphery of the gripping portion 11C can be pressed evenly against the inner periphery of the workpiece W. it can. For this reason, the work W can be gripped more evenly by using the thrust of the mandrel 14 facing the thrust of the push rod 12.

  Therefore, the workpiece gripping apparatus of the present invention can grip the workpiece W satisfactorily.

  In addition, the mandrel 14 is a mandrel 14 that centers the work W with the outer periphery contacting the inner periphery of the work W. For this reason, the workpiece gripping device can expand the diameter of the gripping portion 11 </ b> C by using the thrust inserted into the workpiece W of the mandrel 14 facing the thrust of the push rod 12. As a result, the workpiece gripping device can simultaneously center and grip the workpiece W without wasting thrust for inserting the centering member into the workpiece W.

  The workpiece gripping device is provided between the tip of the mandrel 14 and the gripping part 11C, and the third inclined surface 13D that contacts the first inclined surface 11H and the tip of the mandrel 14 contact each other. And a cylindrical portion 13 that has a contact portion 13B and is movable in the central axis direction. For this reason, in this workpiece gripping device, the contact portion 13B is interposed between the mandrel 14 and the gripping portion 11C. That is, in the workpiece gripping device, the mandrel 14 and the gripping part 11C do not come into contact with each other, so that the gripping part 11C is not damaged by the mandrel 14. This workpiece gripping device can protect the gripping portion 11C with the cylindrical portion 13 by providing the cylindrical portion 13 between the tip portion of the mandrel 14 and the gripping portion 11C. For this reason, if the cylindrical part 13 is damaged by the mandrel 14, it is only necessary to replace only the cylindrical part 13 instead of each device. That is, this work gripping device can facilitate maintenance.

  Further, the mandrel 14 of the workpiece gripping device includes a fourth inclined surface 14A. 14 A of 4th inclined surfaces incline in the direction in which the front-end | tip part of the mandrel 14 approaches a central axis toward the front-end | tip, and contact | abut to the contact part 13B. In addition, the inclination angle with respect to the central axis of the third inclined surface 13D is smaller than the inclination angle with respect to the central axis of the fourth inclined surface 14A. For this reason, a larger surface pressure can be applied to the third inclined surface 13D than when there is no angular difference between the third inclined surface 13D and the fourth inclined surface 14A. For this reason, this workpiece gripping apparatus can grip the workpiece W more reliably.

<Other embodiments>
The present invention is not limited to the first embodiment described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In the first embodiment, the cylindrical portion has the shaft portion. However, the present invention is not limited to this, and the cylindrical portion may be only the contact portion.
(2) In the first embodiment, the operating oil is caused to flow into the space provided in the drive unit to operate the piston. However, the present invention is not limited thereto, and compressed air or the like is caused to flow into the space provided in the drive unit. The piston may be operated.
(3) In the first embodiment, the cylindrical portion is used. However, the present invention is not limited to this, and the cylindrical portion may not be used. In this case, the fourth inclined surface of the mandrel is brought into surface contact with the first inclined surface of the gripping portion of the collet.
(4) In the first embodiment, the inclination angle of the cylindrical portion with respect to the central axis of the third inclined surface is smaller than the inclination angle of the mandrel with respect to the central axis of the fourth inclined surface. The inclination angle with respect to the central axis of the three inclined surfaces may be the same as the inclination angle with respect to the central axis of the fourth inclined surface of the mandrel.
(5) In Embodiment 1, the compression coil spring is used for the buffer member. However, the present invention is not limited to this, and a hydraulic damper, rubber, or the like may be used for the buffer member.
(6) In the first embodiment, the knurl processing is performed on the outer periphery of the collet gripping portion. However, the present invention is not limited to this, and the knurl processing may not be performed on the outer periphery of the collet gripping portion.
(7) In Embodiment 1, the cylindrical member is provided on the outer periphery of the collet. However, the present invention is not limited thereto, and the cylindrical member may not be provided on the outer periphery of the collet.
(8) In the first embodiment, the fifth inclined surface of the push rod and the second inclined surface of the gripping member are in contact, but not limited to this, the fifth inclined surface of the push rod and the second inclined surface of the gripping member. The fifth inclined surface of the push rod and the second inclined surface of the gripping member may not be brought into contact with each other by interposing a cylindrical spacer or the like with the surface.
(9) In Embodiment 1, the left end of the first inclined surface and the right end of the second inclined surface are separated from each other. However, the present invention is not limited to this, and the first inclined surface and the second inclined surface may be adjacent to each other. good.
(10) In the first embodiment, the tubular portion is interposed between the fourth inclined surface of the mandrel and the first inclined surface of the gripping member, and the fourth inclined surface of the mandrel and the first inclined surface of the gripping member are Although it is not made to contact | abut, you may contact | abut not only this but the 4th inclined surface of a mandrel, and the 1st inclined surface of a holding member.

  W ... Work, 11C ... Gripping part (gripping member), 11G ... Second inclined surface, 11H ... First inclined surface, 12 ... Push rod (second pressing member), 13 ... Cylindrical part, 13B ... Abutting part, 13D: Third inclined surface, 14: Mandrel (centering member (first pressing member)), 14A: Fourth inclined surface

Claims (4)

In a workpiece gripping device that grips the inner periphery of a cylindrical workpiece,
A first inclined surface extending in a central axis direction, provided on an inner periphery of one end portion, and inclined in a direction away from the central axis toward the one end portion; and the first A gripping member provided adjacent to the inclined surface and having a second inclined surface inclined in a direction away from the central axis toward the other end, and inserted into the workpiece;
A first pressing member extending in the central axis direction, and an outer periphery of a tip portion extending the gripping member in a direction away from the central axis via the first inclined surface;
Extending in the direction of the central axis, the tip portion is arranged to face the tip portion of the first pressing member, and the outer periphery of the tip portion widens the gripping member in a direction away from the center axis via the second inclined surface. A second pressing member;
A workpiece gripping device comprising: The first pressing member is
The workpiece gripping device according to claim 1, wherein the workpiece gripping device is a centering member that centers the workpiece by contacting an inner periphery of the workpiece.   A third inclined surface that is provided between the distal end portion of the first pressing member and the gripping member and abuts on the first inclined surface, and an abutting portion on which the distal end portion of the first pressing member abuts The workpiece gripping device according to claim 1, further comprising a cylindrical portion that is movable in the central axis direction. The first pressing member is
A distal end portion is inclined in a direction approaching the central axis toward the distal end and includes a fourth inclined surface that contacts the contact portion;
The workpiece gripping device according to claim 3, wherein an inclination angle of the third inclined surface with respect to the central axis is smaller than an inclination angle of the fourth inclined surface with respect to the central axis.

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