Elliptical vibration cutting method and elliptical vibration cutting apparatus

• US 20020152851A1
• Filed: 03/27/2001
• Published: 10/24/2002
• Est. Priority Date: 08/12/1998
• Status: Active Grant

• Current Assignee: Eiji Shamoto, Makoto Matsuo, Toshimichi Moriwaki
• Original Assignee: Eiji Shamoto, Makoto Matsuo, Toshimichi Moriwaki
• Inventors: Shamoto, Eiji, Matsuo, Makoto, Moriwaki, Toshimichi
• Granted Patent: US 6,637,303 B2
• Time in Patent Office: Days
• US Class Current: 82/1.11
• CPC Class Codes: B23B 2260/108 Piezoelectric elements
• CPC Class Codes: B23B 2265/16 Elliptical
• CPC Class Codes: B23B 2270/10 Use of ultrasound
• CPC Class Codes: B23B 25/02 Arrangements for chip-breaking in turning-machines on cutting tools B23B27/22
• CPC Class Codes: B23B 29/125 Vibratory toolholders
• CPC Class Codes: Y10S 82/904 Vibrating method or tool
• CPC Class Codes: Y10T 82/10 Process of turning
• CPC Class Codes: Y10T 82/125 Tool simultaneously moving axially
• CPC Class Codes: Y10T 82/2591 Tool post
• CPC Class Codes: Y10T 82/30 Miscellaneous

Abstract

A workpiece is cut by a cutting tool that is attached to a cylindrical support body vibrated by at least two piezoelectric drive elements. The efficiency of the mechanical vibration is improved by attaching the piezoelectric drive elements to a cylindrical body portion (7,7.1,7.2) of the tool support body (2) and by providing the support body with a plurality of necked-down end sections. At least the cylindrical body portion (7,7.1,7.2) is a cylinder with a substantially circular cross-section or with a circular cross-section to provide a constant or a substantially constant bending rigidity of the cylindrical tool support body.

Claims

1. A method for cutting a workpiece by a vibratory action, comprising the following steps:

(a) securing at least a first and a second piezoelectric element (9, 10) with a 90°

angular, circumferential, on-center spacing between said at least first and second piezoelectric elements to a cylindrical body portion (7, 7.1 or 7.2) of a support body (2) for a cutting tool (6), said support body having a central longitudinal axis, said cylindrical body portion having a circular or substantially circular cross-section;

(b) securing a cutting tool (6) to at least one outer end of said support body (2);

(c) applying electrical power to said at least first and second piezoelectric elements for vibrating said support body with a vibration having an elliptical or circular vibration locus (16); and

(d) engaging said cutting tool (6) and said workpiece (5) with each other for cutting said workpiece.

2. The method of claim 1, further comprising the steps of:

(e) sensing at least one vibration characteristic of said support body (2),

(f) producing a feedback signal in response to said vibration characteristic, and

(g) controlling said applying of electrical power to said at least first and second piezoelectric elements in response to said feedback signal for stabilizing said elliptical or circular vibration locus.

3. An elliptical vibration cutting method employing an elliptical vibrator elliptically vibrating a cutting tool with respect to a workpiece for performing cutting on said workpiece, wherein

said elliptical vibrator comprises at least two piezoelectric drive elements including a first and a second piezoelectric drive element for driving said elliptical vibrator, and a cylindrical body portion having a substantially circular or circular cross-section to which said first and second piezoelectric drive elements are attached, wherein

said second piezoelectric drive element is arranged at a position spaced circumferentially by 90°

from said first piezoelectric element along an outer peripheral direction of said cylindrical body portion having said substantially circular or circular cross-section, wherein

an outer peripheral surface of said body portion positioned between said first and second piezoelectric elements has an outer peripheral shape with a circular or substantially circular cross-sectional configuration having a central longitudinal axis forming a central axis of said cutting tool,

said method comprising the step of elliptically vibrating said elliptical vibrator by applying a voltage to said piezoelectric drive elements to cut said workpiece.

4. The elliptical vibration cutting method of claim 3, further comprising tracking said elliptical vibration, and controlling said elliptical vibration in response to said tracking for stabilizing a locus of elliptical vibration on the cutting edge of said cutting tool.

5. An apparatus for cutting a workpiece by vibratory action, said apparatus comprising a vibratory tool support body (2) having a cylindrical body portion (7,7.1,7.2) with a circular or substantially circular cross-section wherein said cylindrical body portion (7,7.1,7.2) comprises a circumferential, peripheral surface forming a cylinder that has said circular or substantially circular cross-section, at least two piezoelectric drive elements including a first and a second piezoelectric drive element (9, 10) secured to said cylindrical body portion (7,7.1,7.2) of said vibratory tool support body (2) with a 90°

angular on-center circumferential spacing between said at least first and second piezoelectric drive elements (9, 10), a mounting surface (20) for securing a tool (6) to one end of said vibratory tool support body, and means (11) for energizing said at least first and second piezoelectric drive elements for vibrating said vibratory tool support body (2) by a vibration having an elliptical or circular locus.

6. The apparatus of claim 5, wherein said cylindrical body portion (7,7.1,7.2) of said vibratory tool support body (2) has a first diameter and a central longitudinal axis, said vibratory tool support body (2) further comprising first body sections (8, 12) extending from said cylindrical body portion (7,7.1,7.2) coaxially relative to said central longitudinal axis, said first body sections having a second diameter smaller than said first diameter to provide a first stepped or necked-down configuration for amplifying said vibratory action, and second body sections (8A, 13) extending from said first body sections (8, 12) coaxially relative to said central longitudinal axis, said second body sections (8A, 13) having a third diameter smaller than said second diameter to provide a second stepped or necked-down configuration, and wherein said mounting surface (20) is positioned at an outer end of one of said second body sections (8A).

7. The apparatus of claim 6, further comprising at least one sensor (21) positioned relative to said vibratory tool support body (2) for sensing a vibration characteristic of said vibratory tool support body (2), a feedback circuit (22) having an input connected to said at least one sensor (21) and an output connected to an input of said means (11) for energizing said piezoelectric drive elements (9, 9A, 10, 10A) in response to an output signal from said at least one sensor.

8. The apparatus of claim 6, wherein said at least one sensor (21) is positioned on said cylindrical central body portion (7,7.1,7.2) for sensing said vibration characteristic.

9. The apparatus of claim 7, comprising at least two sensors (21) positioned circumferentially spaced relative to one of said first body sections (8) between said cylindrical body portion (7,7.1,7.2) and said one second body section (8A) to which said tool (6) is secured.

10. The apparatus of claim 7, comprising three sensors (21) including a first sensor positioned relative to said cylindrical central body portion (7,7.1,7.2) and second and third sensors positioned circumferentially spaced relative to one of said first body sections (8) between said cylindrical central body portion and said one second body section (8A) to which said tool (6) is secured.

11. The apparatus of claim 6, further comprising a first support member (3A) and a second support member (3B) for supporting said vibratory tool support body (2), wherein said first and second support members (3A, 3B) are spaced from each other by an on-center spacing (L) which corresponds to a spacing between vibration nodes of said vibratory tool support body (2).

12. The apparatus of claim 11, wherein said first and second support members (3A, 3B) support said first body sections (8, 12) having a second diameter smaller than said first diameter.

13. The apparatus of claim 5, comprising four piezoelectric drive elements (9, 9A;

10, 10A) secured to said cylindrical body portion (7,7.1,7.2) having said circular or substantially circular cross-section, with said angular on-center spacing of 90°

between neighboring piezoelectric drive elements, so that four circumferential peripheral surface sections are formed.

14. The apparatus of claim 5, wherein said cylindrical body portion (7,7.1,7.2) of said vibratory tool support body (2) has a circular cross-section and a geometric moment of inertia (Ic) which is constant for 360 °

around a central longitudinal axis of said vibratory tool support body (2).

15. The apparatus of claim 14, wherein said at least first and second piezoelectric drive elements have a radially inwardly curved surface matching said circumferential peripheral surface of said cylindrical body portion (7,7.1,7.2) having said circular cross-section.

16. The apparatus of claim 14, comprising four piezoelectric drive elements (9′

, 9A′

;

10′

, 10A′

) each having a radially inwardly curved surface matching said circumferential, peripheral surface of said cylindrical body portion (7,7.1,7.2) having said circular cross-section.

17. The apparatus of claim 5, wherein said cylindrical body portion (7) of said vibratory tool support body (2) has a substantially circular cross-section and a substantially constant geometric moment of inertia (I) for 360°

around a central longitudinal axis of said circular cross-section.

18. The apparatus of claim 17, wherein said cylindrical body portion (7) comprises at least two flattened areas (14,15) in said circumferential, peripheral surface whereby said cross-section is substantially circular, said first piezoelectric drive element being secured to one of said at least two flattened areas, said second piezoelectric drive element being secured to the other flattened area of said at least two flattened areas.

19. The apparatus of claim 18, wherein each of said at least two flattened areas has a surface area size just sufficient for the mounting of the respective piezoelectric drive element.