JP2005231006A - Chuck and workpiece gripping method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chuck attaining high accuracy machining by stably holding a workpiece even when a gripped surface of the workpiece is distorted. <P>SOLUTION: The chuck is provided with a workpiece gripper 50 having slit forming parts 52 provided with slits 51 for diameter enlargement; a pressure transmission member 60 abutting on the inner diameter or outer diameter of the slit forming parts 52; and an auxiliary shaft 70 clamping the pressure transmission member 60 between the workpiece gripper 50 and the auxiliary shaft 70. The pressure transmission member 60 is pressed in an axial direction to convert axial pressure into radial pressure which is dispersedly transmitted to each part of the slit forming parts 52. The slit forming parts 52 are thereby deformed elastically to generate gripping force. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a machining chuck and a workpiece gripping method using the chuck.

  Generally, when a workpiece is gripped and machined, a spring collet is used as a gripping tool. The spring collet includes an inner diameter spring collet and an outer diameter spring collet.

  FIG. 1 shows an example of a chuck using an inner diameter spring collet. The inner diameter spring collet grips the inner diameter when the work has an opening. When the draw bar 20 passing through the axial center of the collet 10 is pulled, the slit forming portion at the tip of the collet expands and grips the workpiece W by the action of a tapered sliding surface between the collet 10 and the draw bar 20.

  FIG. 2 shows an example of a chuck using an outer diameter spring collet. The outer diameter spring collet grips the outer diameter of the workpiece. Similarly to the inner diameter spring collet, the slit forming portion at the tip of the collet is reduced in diameter by the action of a tapered sliding surface between the collet 30 and the support shaft 40 to grip the workpiece W.

  However, these chucks have the following problems. That is, these chucks slide the draw bar or support shaft and the collet directly, and do not have a medium between the draw bar or support shaft and the collet for distributing and transmitting the pressure. Therefore, if the gripping surface of the workpiece is not uniform, for example, if the gripping surface of the workpiece inner diameter is deformed and distorted due to heat shrinkage after casting or sintering, the slit forming part at the tip of the collet is distorted. Cannot be absorbed, and the slit forming portion and the workpiece are in a local contact state. Since the relative positional relationship between the collet and the workpiece is determined by the contact state, there has been a problem that processing accuracy such as roundness, flatness, and runout is reduced due to distortion of the workpiece.

  Further, even if the pressure for reducing or expanding the collet diameter is increased in order to avoid the local contact state, deformation of the workpiece due to the gripping force is increased, and it is difficult to ensure machining accuracy.

  Here, a chuck using an elastic body such as rubber is known as a chuck that can be held while suppressing deformation of the workpiece (see, for example, Patent Document 1). However, since the elastic body compressed and expanded directly grips the workpiece, there is a problem that the elastic body is easily damaged.

JP-A-8-243815

  The problem to be solved by the present invention is to provide a chuck and a work gripping method capable of stably holding a work even when the gripped surface of the work is not uniform and enabling highly accurate processing. .

  In order to solve the above-mentioned problem, a work gripping tool provided with a slit forming portion provided with a slit to enable reduction and expansion, a pressure transmission member in contact with the inner diameter or outer diameter of the slit forming portion, An auxiliary shaft that sandwiches the pressure transmission member between the workpiece gripping tool, and the pressure transmission member is pressed in the axial direction to convert the axial pressure into a radial pressure and is distributed to each part of the slit forming portion And a chuck configured to elastically deform the slit forming portion to generate a gripping force.

Such a chuck becomes more preferable when the following configuration is added.
1) The workpiece gripping tool and the auxiliary shaft are provided with surfaces facing each other in the axial direction with the pressure transmission member interposed therebetween, and the workpiece gripping tool and the auxiliary shaft press the pressure transmission member in the axial direction. The configuration.
2) The pressure transmission member is made of rubber.
3) The axial length of the slit forming portion of the workpiece gripping tool and the pressure transmission member is set to be 1 to 2 times the axial dimension of the gripped surface of the workpiece.

  In addition, the pressure transmission member sandwiched between the workpiece gripper and the auxiliary shaft is pressed in the axial direction, and the axial pressure is converted into the radial pressure by the pressure transmission member, and the slit forming portion of the workpiece gripper is The above problem can be solved by a workpiece gripping method in which the slit forming portion is elastically reduced in diameter or expanded to grip the workpiece while being dispersedly transmitted to each portion.

  Since the pressure transmission member converts the axial pressure into radial pressure and distributes it to each part of the slit forming part of the work gripper, the slit forming part is easy to follow along the surface to be gripped of the work. Even when the gripped surface is not uniform, the workpiece can be stably held as compared with the conventional art. Accordingly, it is possible to reduce the deviation between the axis of the workpiece and the axis of the machine tool while suppressing deformation of the workpiece due to the gripping force, and it is possible to perform highly accurate machining. Further, even in the end surface processing perpendicular to the axis, processing with high accuracy of the perpendicularity of the end surface with respect to the axial direction becomes easier.

  FIG. 3 shows a side view and a front view of the chuck according to the first embodiment, and FIG. 4 shows a cross-sectional view thereof. The chuck is an inner diameter chuck that grips the inner diameter of the workpiece W, and includes a workpiece gripper 50, a pressure transmission member 60 that contacts the inner diameter of the workpiece gripper 50, and an auxiliary shaft 70 that contacts the inner diameter of the pressure transmission member 60. Yes.

  The work gripper 50 is provided with a slit 51 so that the distal end side thereof can be elastically deformed to expand its diameter. The number of slits 51 is preferably eight or less (four in the present embodiment) in order to maintain the rigidity of the workpiece gripper 50.

  The length of the slit 51 is preferably about 1 to 2 times the axial dimension of the surface to be gripped of the workpiece W (1.5 times in this embodiment). This is because the slit forming part 52 can sufficiently expand in diameter by setting it to 1 or more times, and the rigidity of the work gripping tool does not decrease by setting it to 2 times or less and the workpiece W can be stably held.

  In the present embodiment, the slit 51 is provided in a direction parallel to the axis, but any slit that divides the slit forming portion 52 into a plurality of portions in the circumferential direction may be used, and it is not essential to be parallel to the axis.

  The pressure transmission member 60 is in contact with the inner diameter of the slit forming portion 52. The pressure transmission member 60 may be any member that converts axial pressure into radial pressure when it is pressed in the axial direction and transmits the pressure in a distributed manner to each part of the slit forming portion 52, but is preferably made of rubber. (Urethane rubber in this embodiment). In addition, as shown in FIG. 7, a fluid such as oil or a gel such as silicon gel may be enclosed in a deformable cylindrical hollow container or bag.

  The auxiliary shaft 70 is in contact with the inner diameter of the pressure transmission member 60, and the pressure transmission member 60 is sandwiched between the work gripper 50.

  The work gripper 50 has a surface 53 on its inner diameter, the auxiliary shaft 70 has a surface 71 on its outer diameter, and these surfaces 53 and 71 face each other in the axial direction with the pressure transmission member 60 in between. Therefore, when the auxiliary shaft 70 is moved in the axial direction, the work gripper 50 and the auxiliary shaft 70 press the pressure transmission member 60 in the axial direction.

  FIG. 5 shows an example of use of the chuck according to the first embodiment. The workpiece W is, for example, a flange joint, and its inner diameter is deformed and distorted into a convex shape.

  When the auxiliary shaft 70 is moved in the axial direction and the pressure transmitting member 60 is pressed in the axial direction, the axial pressure is converted into radial pressure by the pressure transmitting member 60 and transmitted to the slit forming portion 52, and the slit forming portion is expanded in diameter. Then, the inner diameter of the workpiece W is gripped. At this time, since the pressure is distributed and transmitted to each part of the slit forming part 52, the slit forming part 52 can easily follow the distorted gripped surface of the work W, and can stably hold the work W. . Further, even if the inner diameter of the workpiece W is distorted from the two-dot chain line state to the solid line state as shown in FIG. 6, the pressure transmission member 60 tries to absorb the distortion, and the axis of the workpiece W and the axis of the machine tool Reduce the deviation from the mind.

  In addition, there is no part that slides directly on the tapered sliding surface like a conventional chuck using a collet, so there is little loss of force due to friction, and the workpiece W can be gripped with less force than before. Can do. Further, since the sliding surface is hardly worn, the tool life is long and economical.

  3 and 4, the tip 54 of the workpiece gripper 50 and the tip 72 of the auxiliary shaft 70 are oriented in the same direction, but the present invention is not limited to this. That is, as shown in FIG. 8, the tip 54 of the workpiece gripper 50 and the tip 72 of the auxiliary shaft 70 may be peeled in opposite directions.

  FIG. 9 shows a side view and a front view of the chuck according to the second embodiment, and FIG. 10 shows a cross-sectional view thereof. This chuck is an outer diameter chuck for gripping the outer diameter of the workpiece W, and includes a workpiece gripper 50, a pressure transmission member 60 in contact with the outer diameter of the workpiece gripper 50, and an auxiliary shaft (in contact with the outer diameter of the pressure transmission member 60). Hollow shaft) 70.

  Similar to the first embodiment, the workpiece gripper 50 is provided with a slit 51 so that the distal end side thereof can be elastically deformed and reduced in diameter. The pressure transmission member 60 converts axial pressure into radial pressure when it is pressed in the axial direction and transmits it in a distributed manner to each part of the slit forming portion 52, such as rubber or a deformable cylindrical shape. A fluid or gel is enclosed in a hollow container or bag. Further, the auxiliary shaft 70 is in contact with the outer diameter of the pressure transmission member 60, and the pressure transmission member 60 is sandwiched between the work gripper 50.

  The workpiece gripper 50 has a surface 53 on its outer diameter, the auxiliary shaft 70 has a surface 71 on its inner diameter, and these surfaces 53 and 71 are opposed to each other in the axial direction with the pressure transmission member 60 therebetween. Therefore, when the auxiliary shaft 70 is moved in the axial direction, the work gripper 50 and the auxiliary shaft 70 press the pressure transmission member 60 in the axial direction.

  FIG. 11 shows an example of use of the chuck according to the second embodiment. The workpiece W is distorted by deforming its outer diameter into a convex shape.

  When the auxiliary shaft 70 is moved in the axial direction and the pressure transmitting member 60 is pressed in the axial direction, the axial pressure is converted into radial pressure by the pressure transmitting member 60 and transmitted to the slit forming portion 52, and the slit forming portion is reduced in diameter. Then, the outer diameter of the workpiece W is gripped. At this time, since the pressure is distributed and transmitted to each part of the slit forming part 52, the slit forming part 52 can easily follow the distorted gripped surface of the work W, and can stably hold the work W. .

Diagram showing an example of a conventional inner diameter chuck Diagram showing an example of a conventional outer diameter chuck (A) is a side view of the chuck according to the first embodiment, and (b) is a front view. 3A is a cross-sectional view taken along line AA in FIG. 3B, and FIG. 3B is a cross-sectional view taken along line BB in FIG. An example of use of the chuck of the first embodiment is shown, (a) is a diagram before gripping a workpiece, (b) is a diagram after gripping the workpiece. Sectional view along line CC in Fig. 5 (b) showing absorption of workpiece distortion by the pressure transmission member The chuck | zipper of the modification of 1st Embodiment is shown, (a) is sectional drawing of the side view of this chuck, (b) is sectional drawing of the front view of this chuck | zipper The figure which shows the other modification of 1st Embodiment. (A) is a side view of the chuck of the second embodiment, (b) is a front view. 9A is a cross-sectional view taken along line DD in FIG. 9B, and FIG. 9B is a cross-sectional view taken along line EE in FIG. An example of use of the chuck of the second embodiment is shown, (a) is a diagram before gripping a workpiece, (b) is a diagram after gripping the workpiece.

Explanation of symbols

10 inner diameter spring collet 20 draw bar 30 outer diameter spring collet 40 support shaft 50 work gripper 51 slit 52 slit forming portion 53 surface 60 pressure transmission member 70 auxiliary shaft 71 surface

Claims (5)

  A workpiece gripping tool provided with a slit forming portion that is provided with a slit to enable reduction and expansion, a pressure transmission member in contact with an inner diameter or an outer diameter of the slit formation portion, and the pressure transmission member as the workpiece gripping tool. An auxiliary shaft sandwiched between them, and the pressure transmitting member is pressed in the axial direction to convert the axial pressure into a radial pressure, and is distributed and transmitted to each portion of the slit forming portion. A chuck configured to generate a gripping force by elastically deforming.   The workpiece gripper and the auxiliary shaft each include a surface facing each other in the axial direction with the pressure transmission member interposed therebetween, so that the workpiece gripper and the auxiliary shaft press the pressure transmission member in the axial direction. The chuck according to claim 1 constituted.   The chuck according to claim 1, wherein the pressure transmission member is made of rubber.   The chuck according to any one of claims 1 to 3, wherein the slit forming portion of the workpiece gripping tool and the axial length of the pressure transmission member are 1 to 2 times the axial dimension of the workpiece gripping surface. .   A pressure transmission member sandwiched between the workpiece gripper and the auxiliary shaft is pressed in the axial direction, and the pressure transmission member converts the axial pressure into a radial pressure, and at each part of the slit forming portion of the workpiece gripper. A workpiece gripping method in which the workpiece is gripped by being distributed and transmitted and elastically reducing or expanding the slit forming portion.

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