Miter saw
A miter saw includes a base assembly and a saw unit pivotably coupled to the base assembly. The saw unit includes a saw arm, a brushless motor supported by the saw arm, and power electronics positioned outside the motor for supplying power to the motor. The power electronics are coupled to a structural component of the miter saw to utilize the entire mass of the structural component as a heat sink to dissipate heat generated by the power electronics.
1. A miter saw comprising:
a base assembly including
a base,
a turntable pivotably coupled to the base about a vertical miter axis, and
a bevel arm pivotably coupled to the turntable about a horizontal bevel axis; and
a saw unit including
a saw arm pivotably coupled to the bevel arm about a chop axis,
a brushless motor supported by the saw arm,
a plate coupled to the saw arm,
a circuit board electrically coupled to the brushless motor, the circuit board positioned relative to the plate as to be encapsulated by a potting material on the plate;
a bracket directly attached to the saw arm, the bracket having a length transverse to the chop axis of the saw arm, the bracket spaced from and oriented perpendicular to the circuit board, and
field-effect transistors for supplying power to the motor, the field-effect transistors electrically coupled to the circuit board, the field-effect transistors directly attached to the bracket at a location away from the motor and the circuit board to utilize the saw arm as a heat sink to dissipate heat generated by the field-effect transistors.
2. The miter saw of claim 1 , wherein heat from the field-effect transistors is conducted into the saw arm via the bracket, and into the bevel arm via a joint defining the chop axis.
3. The miter saw of claim 1 , wherein the saw arm includes a cavity in which the field-effect transistors and the bracket are positioned.
4. The miter saw of claim 3 , wherein the circuit board and the plate are positioned within the cavity.
5. The miter saw of claim 4 , wherein the cavity of the saw arm is between the chop axis and the brushless motor in a direction transverse to the chop axis.
6. The miter saw of claim 1 , wherein the bracket is made from aluminum.
7. The miter saw of claim 1 , further comprising a power tool battery pack electrically connected with the field-effect transistors and operable to power the brushless motor.
8. The miter saw of claim 7 , wherein the field-effect transistors are positioned outside the power tool battery pack.
9. The miter saw of claim 7 , wherein the saw unit includes a battery pack mounting portion that selectively receives the power tool battery pack along an insertion direction for the power tool battery pack to power the field-effect transistors, and wherein the insertion direction is perpendicular to the longitudinal axis of the bracket.
10. The miter saw of claim 9 , wherein the insertion direction is perpendicular to the plate.
11. The miter saw of claim 10 , wherein the insertion direction is parallel to a rotational axis of the brushless motor.
12. The miter saw of claim 1 , wherein the saw unit includes a handle to be gripped by an operator for pivoting the saw unit about the chop axis.
13. The miter saw of claim 12 , wherein the brushless motor is positioned between the handle and the field-effect transistors in a direction transverse to the chop axis.
14. The miter saw of claim 1 , wherein the field-effect transistors are positioned along the length of the bracket.
15. The miter saw of claim 14 , wherein heat generated by the field-effect transistors is conducted into the saw arm via the bracket, and into the bevel arm via a joint defining the chop axis.