Power tool

Abstract

It is an object of the invention to provide an effective technique for avoiding the influence of reaction during tightening operation in the rotary fastening tool. Representative rotary fastening tool includes a tool body, a motor housed within the tool body, a driving-side rotating member that is rotationally driven by the motor, a driven-side rotating member that is disposed coaxially with the driving-side rotating member, a tip-end side rotating member that is disposed coaxially with the driven-side rotating member and rotationally driven via the driven-side rotating member, the tip-end side rotating member driving a tool bit to perform a tightening operation and a rotation control mechanism that allows the tip-end side rotating member to rotate in the tightening direction during the tightening operation of the tool bit, wherein, when the tip-end side rotating member is fixed to a workpiece with the tool bit during the tightening operation and when torque transmission from the driving-side rotating member to the driven-side rotating member is interrupted, the rotation control mechanism locks the tip-end side rotating member and the tool body together against rotation with respect to each other to prevent the tool body from rotating in the tightening direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view schematically showing an entire electric screwdriver according to an embodiment of the invention.

FIG. 2 is a sectional view of an essential part of the screwdriver, showing the construction of a torque limiter, a first spindle, a second spindle and a one-way clutch.

FIG. 3 is a schematic view of the torque limit in development.

FIG. 4 is a side view of a driven-side clutch member of the torque limiter.

FIG. 5 is a side view of a driving-side clutch member of the torque limiter.

FIG. 6 is a sectional view taken along line A-A in FIG. 2.

FIG. 7 is a sectional view taken along line B-B in FIG. 2.

FIG. 8 is a sectional view taken along line C-C in FIG. 2.

FIG. 9 is a graph showing the relationship between the torque and time during tightening operation (normal rotation).

FIG. 10 is a view illustrating the operations of the torque limiter, the first and second spindles and the one-way clutch during tightening operation (normal rotation).

FIG. 11 is a view illustrating the operations of the torque limiter, the first and second spindles and the one-way clutch during tightening operation (normal rotation).

FIG. 12 is a view illustrating the operations of the torque limiter, the first and second spindles and the one-way clutch during tightening operation (normal rotation).

FIG. 13 is a view illustrating the operations of the torque limiter, the first and second spindles and the one-way clutch during loosening operation (reverse rotation).

FIG. 14 is a view illustrating the operations of the torque limiter, the first and second spindles and the one-way clutch during loosening operation (reverse rotation).

FIG. 15 is a view illustrating the operations of the torque limiter, the first and second spindles and the one-way clutch during loosening operation (reverse rotation).

Claims

1. A rotary fastening tool comprising: a tool body,a motor housed within the tool body,a driving-side rotating member that is rotationally driven by the motor,a driven-side rotating member that is disposed coaxially with the driving-side rotating member,a tip-end side rotating member that is disposed coaxially with the driven-side rotating member and rotationally driven via the driven-side rotating member, the tip-end side rotating member driving a tool bit to perform a tightening operation anda rotation control mechanism that allows the tip-end side rotating member to rotate in the tightening direction during the tightening operation of the tool bit, wherein, when the tip-end side rotating member is fixed to a workpiece with the tool bit during the tightening operation and when torque transmission from the driving-side rotating member to the driven-side rotating member is interrupted, the rotation control mechanism locks the tip-end side rotating member and the tool body together against rotation with respect to each other to prevent the tool body from rotating in the tightening direction.

2. The rotary fastening tool as defined in claim 1 further comprising a torque limiter that transmits torque of the driving-side rotating member to the driven-side rotating member when the torque acting upon the driven-side rotating member is lower than a predetermined set value, while interrupting the torque transmission when the torque acting upon the driven-side rotating member exceeds the set value.

3. The rotary fastening tool as defined in claim 1 wherein the motor is driven either in a normal direction to perform a tightening operation or a reverse direction of rotation to perform a loosening operation by mode-selecting operation and wherein, during the loosening operation of the tool bit, the rotation control mechanism is disabled from locking the tip-end side rotating member and the tool body by utilizing a rotation of the driven-side rotating member in the loosening direction to allow the loosening operation of the tool bit.

4. The rotary fastening tool as defined in claim 1 further comprising a torque limiter that transits torque of the driving-side rotating member to the driven-side rotating member when the torque acting upon the driven-side rotating member is lower than a predetermined set value, while interrupting the torque transmission when the torque acting upon the driven-side rotating member exceeds the set value, wherein the motor is driven either in a normal direction to perform a tightening operation or a reverse direction of rotation to perform a loosening operation by mode-selecting operation andwherein, during the loosening operation of the tool bit, the rotation control mechanism is disabled from locking the tip-end side rotating member and the tool body by utilizing a rotation of the driven-side rotating member in the loosening direction to allow the loosening operation of the tool bit.

5. The rotary fastening tool as defined in claim 4, wherein the rotation control mechanism comprises: a rotation control member disposed between the tool body and the tip-end side rotating member, the rotation control member being provided with an actuated position and a released position wherein the rotation control member in the actuated position locks the tip-end side rotating member and the tool body when the tip-end side rotating member is rotated in the loosening direction during the tightening operation, while the rotation control member in the released position releases prohibits the locking between the tip-end side rotating member and the tool body.

6. The rotary fastening tool as defined in claim 5, wherein the rotation control mechanism comprises a retainer that is disposed between the tool body and the tip-end side rotating member such that the retainer is allowed to rotate with respect to the tool body and the tip-end side rotating member and wherein the retainer moves the rotation control member between the actuated position and the released position and retains the rotation control member in that position,

7. The rotary fastening tool as defined in claim 6, wherein, when the motor is driven in the normal direction and the driven-side rotating member is rotated in the tightening direction, the driven-side rotating member rotates the retainer in the tightening direction before rotationally driving the tip-end side rotating member and the retainer moves the rotation control member to the actuated position.

8. The rotary fastening tool as defined in claim 6, wherein, when the motor is driven in the reverse direction and the driven-side rotating member is rotated in the loosening direction, the driven-side rotating member rotates the retainer in the loosening direction before rotationally driving the tip-end side rotating member and the retainer moves the rotation control member to the released position.

9. The rotary fastening tool as defined in claim 4, wherein: the tip-end side rotating member has a plane region in a predetermined extent in the circumferential direction,the rotation control member comprises a member having a circular section, wherein, during the tightening operation of the tool bit, when the torque limiter interrupts the torque transmission, the rotation control member moves toward one end of the plane region in the circumferential direction and engages with both the plane region and the inner wall surface of the tool body, thereby locking the tip-end side rotating member and the tool body together and controlling rotation of the tool body in the tightening direction with respect to the tip-end side rotating member, andthe retainer has an elastic element that biases the circular member toward the one end of the plane region in the circumferential direction.

10. The rotary fastening tool as defined in claim 4, wherein: the torque limiter includes a plurality of fit torque receiving parts and a plurality of first torque transmitting parts in the circumferential direction, wherein the first torque receiving parts are provided on the driven-side rotating member and the first torque transmitting parts rotate together with the driving-side rotating member and transmit torque of the driving-side rotating member to the driven-side rotating member while being held in contact with the first torque receiving parts, andthe rotary fastening tool further includes:a second torque receiving part that protrudes radially outward from the tip-end side rotating member,a second torque transmitting part having a predetermined phase difference in the circumferential direction with respect to the second torque receiving part, wherein the second torque transmitting part rotates together with the driven-side rotating member and transmits torque of the driven-side rotating member to the tip-end side rotating member while being held in contact with the second torque receiving part,a third torque receiving part that protrudes from the retainer in the direction of a rotation axis of the driven-side rotating member, anda third torque transmitting part having a predetermined phase difference in the circumferential direction with respect to the third torque receiving part, wherein the third torque transmitting part rotates together with the driven-side rotating member and transmits torque of the driven-side rotating member to the retainer while being held in contact with the third torque receiving part,wherein a phase angle between the third torque receiving part and the third torque transmitting part in the circumferential direction is larger than a phase angle between the first torque transmitting parts in the circumferential direction anda phase angle between the third torque receiving part and the third torque transmitting part in the circumferential direction is smaller than a phase angle between the second torque receiving part and the second torque transmitting part in the circumferential direction.

11. The rotary fastening tool as defined in claim 5, wherein the retainer is held by friction by the elastic member in such a manner as to be prevented from rotating with respect to the tip-end side rotating member unless rotated by the driven-side rotating member rotating in the loosening direction.

12. The rotary fastening tool as defined in claim 1, wherein the rotary fastening tool is provided as an electric screw driver to drive a driver bit for tightening and/or loosening a screw.

13. A rotary fastening tool comprising: a tool body,a motor housed within the tool body,a driving-side rotating member that is rotationally driven by the motor,a driven-side member rotationally driven via the driven-side rotating member, the driven-side member driving a tool bit anda rotation control mechanism that allows the tip-end side rotating member to rotate in the tightening direction during the tightening operation of the tool bit, wherein, when torque transmission from the driving-side rotating member to the driven-side member is interrupted, the rotation control mechanism locks the driven-side member and the tool body together against rotation with respect to each other.

14. The rotary fastening tool as defined in claim 1, wherein the driven-side member comprises: a driven-side rotating member that is disposed coaxially with the driving-side rotating member anda tip-end side rotating member to drive a tool bit, the tip-end rotating member being disposed coaxially with the driven-side rotating member and rotationally driven via the driven-side rotating member,wherein the rotation control mechanism allows the tip-end side rotating member to rotate in the tightening direction during the tightening operation of the tool bit, wherein, when the tip-end side rotating member is fixed to a workpiece with the tool bit during the tightening operation and when torque transmission from the driving-side rotating member to the driven-side rotating member is interrupted, the rotation control mechanism locks the tip-end side rotating member and the tool body together against rotation with respect to each other to prevent the tool body from rotating in the tightening direction.

15. A rotary fastening tool comprising: a tool body,a motor that is housed within the tool body and is driven either in a normal direction or a reverse direction of rotation by mode-selecting operation,a driving-side rotating member that is rotationally driven by the motor,a driven-side rotating member that is disposed coaxially with the driving-side rotating member,a torque limiter that transmits torque of the driving-side rotating member to the driven-side rotating member when the torque acting upon the driven-side rotating member is lower than a predetermined set value, while interrupting the torque transmission when the torque acting upon the driven-side rotating member exceeds the set value,a tip-end side rotating member that is disposed coaxially with the driven-side rotating member and rotationally driven via the driven-side rotating member,a tool bit that performs a tightening operation when rotationally driven in the normal direction via the tip-end side rotating member and performs a loosening operation when rotationally driven in the reverse direction, anda rotation control mechanism that allows the tip-end side rotating member to rotate in the tightening direction during the tightening operation of the tool bit, wherein, when the tip-end side rotating member is fixed to a workpiece with the tool bit during the tightening operation and when torque transmission from the driving-side rotating member to the driven-side rotating member is interrupted, the rotation control mechanism locks the tip-end side rotating member and the tool body together against rotation with respect to each other to prevent the tool body from rotating in the tightening direction andwherein, during the loosening operation of the tool bit, the rotation control mechanism is disabled from locking the tip-end side rotating member and the tool body by utilizing a rotation of the driven-side rotating member in the loosening direction to allow the loosening operation of the tool bit.