Technique for dissipating heat in electric work machine

Patent metadata

Field	Value
Publication number	US-12519376-B2
Application number	US-202217852065-A
Country	US
Kind code	B2
Filing date	Jun 28, 2022
Priority date	Jul 6, 2021
Publication date	Jan 6, 2026
Grant date	Jan 6, 2026

Abstract

An electric work machine in one aspect of the present disclosure includes an electric power input terminal, a motor, a circuit board, a first heat dissipation plate, and a second heat dissipation plate. The circuit board includes a first surface and an electronic circuit on the first surface. The electronic circuit controls supply of AC power to the motor. The electronic circuit includes an electronic component that generates Joule heat. The first heat dissipation plate is spaced from the first surface by a first distance in parallel to the first surface. The second heat dissipation plate is spaced from the first surface by a second distance in parallel to the first surface. The second heat dissipation plate is thermally coupled with the first heat dissipation plate. The second distance is smaller than the first distance.

First claim

What is claimed is:

1 . A hand-held grinder comprising:
a power plug configured to receive an AC power; a brushed AC motor configured to be driven with the AC power received through the power plug; a spindle configured to be detachably attached to a grinding wheel, the spindle being configured to receive a rotational force of the brushed AC motor to thereby rotate; a circuit board including: a first surface, a motor driving circuit on the first surface, the motor driving circuit being configured (i) to operate with a first electric power, and (ii) to control supply of the AC power to the motor, and a first power-supply circuit on the first surface, the first power-supply circuit being configured to receive the AC power to generate the first electric power from the AC power, the first power-supply circuit including a resistor being configured to receive the AC power and to thereby generate a Joule heat; a first heat dissipation plate spaced from the first surface by a first distance in parallel to the first surface; and a second heat dissipation plate spaced from the first surface by a second distance in parallel to the first surface, the second distance being smaller than the first distance, the second heat dissipation plate including a part facing the resistor, and the second heat dissipation plate being (i) included in a single member together with the first heat dissipation plate and (ii) configured such that no portion of the second heat dissipation plate faces the first heat dissipation plate along a direction perpendicular to the first surface; and a third heat dissipation plate spaced from the first surface by a third distance in parallel to the first surface, the third distance being greater than the second distance, the third heat dissipation plate (i) being thermally coupled with the second heat dissipation plate and (ii) including a first part facing the second heat dissipation plate along the direction perpendicular to the first surface.

2 . An electric work machine comprising:
an electric power input terminal configured to receive an AC power; a motor configured to be driven with the AC power received through the electric power input terminal; a mounting part (i) configured to be detachably attached to a tool or (ii) fixed to the tool, the mounting part being configured to transmit a rotational force of the motor to the tool; a circuit board including: a first surface, and an electronic circuit on the first surface, the electronic circuit being configured to control supply of the AC power to the motor, the electronic circuit including an electronic component configured to generate a Joule heat; a first heat dissipation plate spaced from the first surface by a first distance in parallel to the first surface; and a second heat dissipation plate spaced from the first surface by a second distance in parallel to the first surface, the second distance being smaller than the first distance, and the second heat dissipation plate being (i) thermally coupled with the first heat dissipation plate and (ii) configured such that no portion of the second heat dissipation plate faces the first heat dissipation plate along a direction perpendicular to the first surface; and a third heat dissipation plate spaced from the first surface by a third distance in parallel to the first surface, the third distance being greater than the second distance, the third heat dissipation plate (i) being thermally coupled with the second heat dissipation plate and (ii) including a first part facing the second heat dissipation plate along the direction perpendicular to the first surface.

3 . The electric work machine according to claim 2 ,
wherein the second heat dissipation plate includes a second part, the second part facing the electronic component.

4 . The electric work machine according to claim 2 , further comprising:
a coupling member thermally coupling the first heat dissipation plate with the second heat dissipation plate; and a single member including the first heat dissipation plate, the second heat dissipation plate, and the coupling member.

5 . The electric work machine according to claim 2 , further comprising:
a coupling member thermally coupling the second heat dissipation plate with the third heat dissipation plate; and a single member including the first heat dissipation plate, the second heat dissipation plate, the third heat dissipation plate, and the coupling member.

6 . The electric work machine according to claim 5 ,
wherein the second heat dissipation plate, the coupling member, and the third heat dissipation plate form a U-shaped cross-section perpendicular to the first surface.

7 . The electric work machine according to claim 2 ,
wherein the third distance is equal to the first distance.

8 . The electric work machine according to claim 7 ,
wherein the third heat dissipation plate is spaced from the first heat dissipation plate.

9 . The electric work machine according to claim 2 ,
wherein the electronic component includes a resistor, and wherein the first heat dissipation plate and the second heat dissipation plate are spaced from the resistor.

10 . The electric work machine according to claim 2 ,
wherein the electronic circuit includes: a current path configured to electrically connect the electric power input terminal to the motor; and a switch on the current path, configured to complete or interrupt the current path, and thermally coupled with the first heat dissipation plate or with the second heat dissipation plate.

11 . The electric work machine according to claim 10 ,
wherein the switch is thermally coupled with the first heat dissipation plate.

12 . The electric work machine according to claim 2 ,
wherein the first heat dissipation plate and/or the second heat dissipation plate include/includes a leg fixed to the circuit board.

13 . The electric work machine according to claim 12 , further comprising:
a single member including the leg together with the first heat dissipation plate or the second heat dissipation plate.

14 . The electric work machine according to claim 2 ,
wherein the first heat dissipation plate and/or the second heat dissipation plate have/has a thermal conductivity higher than a thermal conductivity of air.

15 . The electric work machine according to claim 2 ,
wherein the first heat dissipation plate and/or the second heat dissipation plate contain/contains a metal.

16 . A method for dissipating a heat generated in an electric work machine, the method comprising:
providing a first heat dissipation plate in parallel to a first surface of a circuit board of the electric work machine such that the first heat dissipation plate is spaced from the first surface by a first distance; providing a second heat dissipation plate in parallel to the first surface such that the second heat dissipation plate is (i) spaced from the first surface by a second distance smaller than the first distance, (ii) thermally coupled with the first heat dissipation plate, and (iii) configured such that no portion of the second heat dissipation plate faces the first heat dissipation plate along a direction perpendicular to the first surface; and providing a third heat dissipation plate spaced from the first surface by a third distance in parallel to the first surface, the third distance being greater than the second distance, the third heat dissipation plate (i) being thermally coupled with the second heat dissipation plate and (ii) including a first part facing the second heat dissipation plate along the d

Assignees

• Makita Corp

Inventors

• Chen Jie
• Fujinami Katsuhito
• Pang hong jun
• Wang Ya
• Luan Fuchao
• Naito Akira

Classifications

• H02K11/33

  Drive circuits, e.g. power electronics (H02K11/38 takes precedence) · CPC title

• H02K2211/03

  Machines characterised by circuit boards, e.g. pcb · CPC title

• B25F5/008

  Cooling means · CPC title

• H02P27/02

  using supply voltage with constant frequency and variable amplitude · CPC title

• B24B47/12

  by mechanical gearing or electric power (B24B47/16 takes precedence) · CPC title