Torque control system for electrically driven rotating tools

• US 6,910,540 B2
• Filed: 04/18/2002
• Issued: 06/28/2005
• Est. Priority Date: 04/25/2001
• Status: Expired due to Fees

• Current Assignee: Katsuyuki Totsu
• Original Assignee: Katsuyuki Totsu
• Inventors: Totsu, Katsuyuki
• Primary Examiner(s): Gerrity, Stephen F.
• Assistant Examiner(s): Nash, Brian
• Application Number:
  US10/476,024
• Publication Number:
  US 20040115014A1
• Time in Patent Office: 1,167 Days
• Field of Search: 173/178, 173/181, 173/6, 173/176, 173/179, 173/180, 173/2, 173/182
• US Class Current: 173/178
• CPC Class Codes: B25B 23/14 Arrangement of torque limiters or torque indicators in wrenches or screwdrivers couplings for transmitting rotation or clutches F16D; devices for measuring torque per se G01L
• CPC Class Codes: B25B 23/147 specially adapted for electrically operated wrenches or screwdrivers
• CPC Class Codes: Y10T 408/89 Tool or Tool with support

Abstract

A torque control system for electrically driven rotating tools capable of always properly and efficiently effecting constant-torque tightening of screws or the like and capable of easily achieving the miniaturization of the whole device and the improvement in torque control accuracy, the torque control system comprising a clutch mechanism that, when a load torque of predetermined value or above acts on a driven shaft joined to the output shaft of an electric motor, operates to cut off the engagement between the output shaft and the driven shaft, a torque setting mechanism that adjusts the engagement point for the clutch mechanism, and a torque detecting mechanism (42) for detecting the clutch operation of the clutch mechanism to effect drive stop control of the electric motor, wherein the torque detecting mechanism (42) is set so that it effects drive stop control of the electric motor simultaneously with the detecting operation thereof in a state in which the clutch operation has been completed as the cam engagement at the cam engagement portion (40a) of the clutch mechanism is completely canceled.

Claims

1. A torque control system for an electrically driven rotating tool, said tool comprising:

a grip portion containing therein an electric motor,

a driven shaft coupled to an output shaft of said electric motor via a speed-reduction mechanism so as to be used as a working shaft,

a clutch mechanism equipped with a cam engaging section which makes a clutch operation that severs a coupling between said output shaft and said driven shaft when a load torque that exceeds a predetermined value acts on said driven shaft,

a torque setting mechanism in which an actuation point of said clutch mechanism to sever a coupling between said output shaft and said driven shaft is adjusted as a set torque value, and

a torque detection mechanism which detects said clutch operation in a cam engaging section of said clutch mechanism to sever a coupling between said output shaft and said driven shaft and which performs a drive stop control of said electric motor wherein

said cam engaging section of said clutch mechanism is comprised of a combination of a clutch cam surface and a steel ball, said clutch cam surface being formed with a projecting portion that makes a clutch operation on a circumference of said driven shaft, and said steel ball facing and elastically engaging with said clutch cam surface via said torque setting mechanism; and

said torque detection mechanism is comprised of a magnet and a magnetic sensor provided on a circumference of said driven shaft, so that said torque detection mechanism detects completion of clutch operation which occurs when a load torque that exceeds a predetermined value acts on said driven shaft and said projecting portion of said clutch cam surface rides over said steel ball to release a cam engagement thus performing said drive stop control of said electric motor.

4. The torque control system for electrically driven rotating tools according to claim 1 or 2, wherein said electric motor of said electrically driven rotating tool is a brushless motor.

2. A torque control system for an electrically driven rotating tool, said tool comprising:

a grip portion containing therein an electric motor,

a driven shaft coupled to an output shaft of said electric motor via a planetary gear speed-reduction mechanism so as to be used as a working shaft,

an internal gear rotatably disposed in a cylindrical grip portion casing that surrounds said planetary gear speed-reduction mechanism, said internal gear engaging with a planetary gear of said speed-reduction mechanism,

a clutch mechanism equipped with a cam engaging section which, in a location between said internal gear and said cylindrical grip portion casing, makes a clutch operation that severs a coupling, between said output shaft and said driven shaft when a load torque that exceeds a predetermined value acts on said driven shaft,

a torque setting mechanism in which an actuation point of said clutch mechanism that severs a coupling between said driven shaft is adjusted as a set torque value, and

a torque detection mechanism which detects said clutch operation of said clutch mechanism to sever a coupling between said output shaft and said driven shaft in said cam engaging section and performs a drive stop control of said electric motor wherein

a cam engaging section of said clutch mechanism is comprised so that a sleeve is concentrically disposed on said driven shaft, an upper end portion of said sleeve is disposed so as to face a closed bottom portion of said internal gear, a clutch cam surface on which a projecting portion that performs said clutch operation is disposed is formed on said closed bottom portion of said internal gear, a steel ball is provided at said upper end portion of said sleeve in a position that corresponds to said projecting portion of said clutch cam surface and said sleeve is elastically held via said torque sitting mechanism, and

said torque detection mechanism is comprised of a magnet which is disposed on one portion of an outside wall of said internal gear and a magnetic sensor which is disposed so as to face said magnet, and said torque detection mechanism detects completion of said clutch operation which occurs when a load torque that exceeds a predetermined value acts on said driven shaft and said projecting portion of said clutch cam surface rides over said steel ball to release a cam engagement, thus performing said drive stop control of said electric motor.

3. The torque control system for electrically driven rotating tools according to claim 2, wherein said clutch mechanism is comprised of:

said clutch cam surface being having said projecting portion used to perform said clutch operation, said clutch cam surface being formed on an outside surface of said closed bottom portion of said internal gear, and said closed bottom portion being in a conical shape, and

said steel ball disposed in said position that corresponds to said projecting portion of said clutch cam surface, and wherein

said steel ball is elastically held, via a torque setting mechanism which is disposed independently from said driven shaft, in an inclined orientation with respect to said driven shaft.