Chucking device and chucking method for machine tool

Patent metadata

Field	Value
Publication number	US-9475126-B2
Application number	US-201414299420-A
Country	US
Kind code	B2
Filing date	Jun 9, 2014
Priority date	Jul 10, 2013
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

In a chucking device and a chucking method for a machine tool which grip a workpiece that serves as a target object to be processed by the machine tool, a first cylinder and a second cylinder are controlled based on the position of a piston of the first cylinder detected by a length measuring sensor, and the position of a piston of the second cylinder detected by a length measuring sensor. In this manner, the workpiece is gripped by respective gripping members at a predetermined position, i.e., the axial center, of a chuck main body.

First claim

What is claimed is:

1. A chucking device for a machine tool for gripping a workpiece as a target object to be processed by the machine tool, comprising:
a chuck main body;
a first cylinder attached to the chuck main body and in which a first piston rod connected to a first piston is displaced in a direction toward the workpiece to thereby position the workpiece;
a second cylinder attached to the chuck main body and in which a second piston rod connected to a second piston is displaced in a direction toward the workpiece to thereby press the positioned workpiece;
a first position detecting sensor that detects a position of the first piston;
a second position detecting sensor that detects a position of the second piston;
a control mechanism that controls the first cylinder and the second cylinder based on the position of the first piston and the position of the second piston, which have been detected, such that the workpiece is gripped at a predetermined position of the chuck main body by the first piston rod and the second piston rod;
a first cylinder controller that displaces the first piston rod by controlling the first cylinder;
a second cylinder controller that displaces the second piston rod by controlling the second cylinder; and
an end position calculating unit, which calculates a position of an end of the first piston rod based on the detected position of the first piston, and calculates a position of an end of the second piston rod based on the detected position of the second piston, wherein:
the first piston rod is displaced toward an axial center of the chuck main body in accordance with a control performed by the first cylinder controller to thereby position the workpiece at a predetermined position on the chuck main body;
the second piston rod is displaced toward the axial center of the chuck main body in accordance with a control performed by the second cylinder controller to thereby press the workpiece;
the first cylinder controller displaces the first piston rod toward the axial center, until the calculated position of the end of the first piston rod reaches a first position configured to position the workpiece; and
the second cylinder controller displaces the second piston rod toward the axial center, until the calculated position of the end of the second piston rod reaches a second position configured to press the workpiece.

2. The chucking device for a machine tool according to claim 1 , the control mechanism further comprising a positional shift calculating unit, which calculates an amount of positional shift between the axial center and a center position of the workpiece that is gripped by the first piston rod and the second piston rod, based on the position of the first piston and the position of the second piston, which have been detected,
wherein the first cylinder controller displaces the first piston rod based on the amount of positional shift, and the second cylinder controller displaces the second piston rod based on the amount of positional shift, whereby the center position of the workpiece is corrected to the axial center.

3. The chucking device for a machine tool according to claim 1 , wherein:
the first cylinder controller displaces the first piston rod toward the axial center while adjusting a velocity of the first piston rod, based on the first position and the position of the end of the first piston rod; and
the second cylinder controller displaces the second piston rod toward the axial center while adjusting a velocity of the second piston rod, based on the second position and the position of the end of the second piston rod.

4. The chucking device for a machine tool according to claim 1 , wherein the control mechanism further comprises a lock-up unit that fixes and holds the first piston rod when the position of the end of the first piston rod reaches the first position.

5. The chucking device for a machine tool according to claim 1 , wherein the first cylinder controller maintains the position of the end of the first piston rod at the first position, after the position of the end has reached the first position.

6. The chucking device for a machine tool according to claim 1 , wherein a gripping force detecting sensor, which detects a gripping force applied to the workpiece by the first piston rod and the second piston rod, is disposed on an end of the first piston rod that contacts the workpiece and/or an end of the second piston rod that contacts the workpiece.

7. The chucking device for a machine tool according to claim 1 , wherein:
the first cylinder and the second cylinder are fluid pressure cylinders;
the first cylinder controller comprises a pressure fluid supply device that displaces the first piston rod by supplying a pressure fluid to the first cylinder; and
the second cylinder controller comprises a pressure fluid supply device that displaces the second piston rod by supplying a pressure fluid to the second cylinder.

8. The chucking device for a machine tool according to claim 7 , wherein:
a first pressure chamber and a second pressure chamber, which are separated by the first piston, are formed in an interior of the first cylinder;
a third pressure chamber and a fourth pressure chamber, which are separated by the second piston, are formed in an interior of the second cylinder,
the chucking device for a machine tool further comprising:
a first pressure sensor that detects a first pressure of the first pressure chamber;
a second pressure sensor that detects a second pressure of the second pressure chamber;
a third pressure sensor that detects a third pressure of the third pressure chamber; and
a fourth pressure sensor that detects a fourth pressure of the fourth pressure chamber,
wherein the control mechanism further comprises a gripping force calculating unit that calculates a gripping force applied to the workpiece by the first piston rod and the second piston rod, based on the detected first pressure and the detected second pressure, and/or the detected third pressure and the detected fourth pressure.

9. The chucking device for a machine tool according to claim 8 , wherein:
the gripping force calculating unit calculates, as a gripping force target value, a gripping force corresponding to a weight of the workpiece;
the first cylinder controller controls the first pressure and the second pressure such that the calculated gripping force becomes the gripping force target value; and
the second cylinder controller controls the third pressure and the fourth pressure such that the calculated gripping force becomes the gripping force target value.

10. The chucking device for a machine tool according to claim 1 , wherein the first cylinder and the second cylinder are attached to the chuck main body in such a way that a direction of a positioning force that acts on the workpiece from the first piston rod, and a direction of a pressing force that acts on the workpiece from the second piston rod lie on substantially the same axis.

11. The chucking device for a machine tool according to claim 10 , wherein the first cylinder and the second cylinder are attached to the chuck main body in confronting relation to each other with the axial center sandwiched therebetween.

12. The chucking device for a machine tool according to claim 11 , wherein, in a case that one first cylinder and one second cylinder, which are disposed in confronting relation to each other sandwiching the axial center therebetween, form one pair, plural pairs of the cylinders are attached to the chuck main body at a predetermined angular interval in a radiating manner with respect to the axial center.

13. The chucking device

Assignees

• Smc Corp

Inventors

• Fujiwara Atsushi
• Nishino Junji

Classifications

• B23Q3/12

  for securing to a spindle in general (B23Q3/152 takes precedence; chucks B23B31/02) · CPC title

• B23B31/30

  using fluid-pressure means in the chuck {(B23B31/10 and B23B31/40 take precedence)} · CPC title

• B23Q3/18 Primary

  for positioning only · CPC title

• Y10T279/1208

  with measuring, indicating or control means · CPC title

• Y10T29/49998

  Work holding · CPC title