Rebar tying tool
A rebar tying tool includes: a feed mechanism ( 24 ), which includes a first brushless motor ( 32 ) and performs an advancing process that advances a wire (W) and a draw-back process that draws back the wire (W); a first inverter circuit ( 212 ), which is electrically connected to the first brushless motor; and a control unit ( 202 ), which controls the first brushless motor via the first inverter circuit. The first brushless motor comprises a first Hall-effect sensor ( 180 ), which is disposed on a first sensor board ( 178 ). In the advancing process, the control unit performs lead-angle control on the first brushless motor at a first lead angle. In the draw-back process, the control unit performs lead-angle control on the first brushless motor at a second lead angle. The first lead angle is set to be larger than the second lead angle.
1. A rebar tying tool comprising:
a feed mechanism comprising a first brushless motor and configured to perform an advancing process that advances a wire and then perform a draw-back process that draws back the wire;
a first inverter circuit electrically connected to the first brushless motor; and
a control unit configured to control the first brushless motor via the first inverter circuit;
wherein:
the first brushless motor comprises a first Hall-effect sensor disposed on a first sensor board;
in the advancing process, the control unit is configured to perform lead-angle control on the first brushless motor at a first lead angle;
in the draw-back process, the control unit is configured to perform lead-angle control on the first brushless motor at a second lead angle; and
the first lead angle is larger than the second lead angle.
2. The rebar tying tool according to claim 1 , wherein:
the first Hall-effect sensor is disposed on the first sensor board such that the first Hall-effect sensor outputs first Hall-effect sensor signals at either the first lead angle or the second lead angle; and
the sum of the first lead angle and the second lead angle is 60°.
3. The rebar tying tool according to claim 1 , further comprising:
a twisting mechanism comprising a second brushless motor and configured to perform a twisting process that twists together end portions or an intermediate portion of the wire and then perform an initial-state returning process that returns the twisting mechanism to an initial state after the wire has been twisted; and
a second inverter circuit electrically connected to the second brushless motor;
wherein:
the control unit is configured to also control the second brushless motor via the second inverter circuit;
the second brushless motor comprises a second Hall-effect sensor, which is disposed on a second sensor board;
in the twisting process, the control unit is configured to perform lead-angle control on the second brushless motor at a third lead angle;
in the initial-state returning process, the control unit is configured to perform lead-angle control on the second brushless motor at a fourth lead angle; and
the third lead angle is smaller than the fourth lead angle.
4. The rebar tying tool according to claim 3 , wherein:
the second Hall-effect sensor is disposed on the second sensor board such that the second Hall-effect sensor outputs second Hall-effect sensor signals at either the third lead angle or the fourth lead angle; and
the sum of the third lead angle and the fourth lead angle is 60°.
5. The rebar tying tool according to claim 1 , further comprising:
a twisting mechanism comprising a second brushless motor and configured to perform a twisting process that twists together end portions or an intermediate portion of the wire and then perform an initial-state returning process that returns the twisting mechanism to an initial state after the wire has been twisted; and
a second inverter circuit electrically connected to the second brushless motor;
wherein:
the control unit is configured to also control the second brushless motor via the second inverter circuit;
the second brushless motor comprises a second Hall-effect sensor, which is disposed on a second sensor board;
in the twisting process, the control unit is configured to perform lead-angle control on the second brushless motor at the second lead angle; and
in the initial-state returning process, the control unit is configured to perform lead-angle control on the second brushless motor at the first lead angle.
6. The rebar tying tool according to claim 5 , wherein:
the first Hall-effect sensor is disposed on the first sensor board such that the first Hall-effect sensor outputs first Hall-effect sensor signals at one of the first lead angle or the second lead angle;
the second Hall-effect sensor is disposed on the second sensor board such that the second Hall-effect sensor outputs second Hall-effect sensor signals at the one of the first lead angle or the second lead angle; and
the sum of the first lead angle and the second lead angle is 60°.
7. A rebar tying tool comprising:
a feed mechanism that includes a first brushless motor;
a first inverter circuit electrically connected to the first brushless motor; and
a control unit configured to supply motor control signals to the first inverter circuit to drive the first brushless motor;
wherein the control unit is configured to:
generate first motor-control signals for driving the first brushless motor to cause the feed mechanism to advance a wire for tying a plurality of rebars by performing lead-angle control at a first lead angle; and
generate second motor-control signals for driving the first brushless motor to retract the wire by performing lead-angle control at a second lead angle that is smaller than the first lead angle.
8. The rebar tying tool according to claim 7 , wherein:
the first brushless motor comprises a first Hall-effect sensor disposed on a first sensor board such that the first Hall-effect sensor outputs first Hall-effect sensor signals at one of the first lead angle or the second lead angle; and
the sum of the first lead angle and the second lead angle is 60°.
9. The rebar tying tool according to claim 8 , further comprising:
a twisting mechanism that includes a second brushless motor; and
a second inverter circuit electrically connected to the second brushless motor;
wherein the control unit is configured to supply motor control signals to the second inverter circuit to drive the second brushless motor; and
the control unit is further configured to:
generate third motor-control signals for driving the second brushless motor to cause the twisting mechanism to twist together ends of the wire for tying the plurality of rebars by performing lead-angle control at a third lead angle; and
generate fourth motor-control signals for driving the second brushless motor to return the twisting mechanism to its initial state by performing lead-angle control at a fourth lead angle that is larger than the third lead angle.
10. The rebar tying tool according to claim 9 , wherein:
the second brushless motor comprises a second Hall-effect sensor disposed on a second sensor board such that the second Hall-effect sensor outputs second Hall-effect sensor signals at either the third lead angle or the fourth lead angle; and
the sum of the third lead angle and the fourth lead angle is 60°.
11. The rebar tying tool according to claim 10 , wherein:
the first lead angle is the same as the fourth lead angle; and
the second lead angle is the same as the third lead angle.
12. The rebar tying tool according to claim 11 , wherein both of the first Hall-effect sensor and the second Hall-effect sensor respectively output the first and second Hall-effect sensor signals at the same one of the first lead angle or the second lead angle.