The present invention relates to printed circuit board assemblies, and more particularly to printed circuit board assemblies for use in power tools.
Power tools include motors configured to move a tool bit. Motors are operated by controlling supply of electrical current from a power source. Flow of current to energize the motor can be controlled by one or more switches which are actuated during energization of the motor. Actuation of the switches generates heat. Some power tools include impellers to dispel heat generated by the switches. Some power tools include heat sinks configured to conduct heat from the switches to a heat sink fin for subsequent convection by the airflow generated by the impeller to dispel the heat generated by the switches to the surroundings of the power tool.
The invention provides, in one aspect, a printed circuit board assembly for use in a power tool including a motor and a power source. The printed circuit board assembly includes a potting boat, a printed circuit board, a thermally conductive gap pad, potting material, and a secondary heat sink. The potting boat includes a plurality of primary heat sink fins, an interior surface, and at least one stand-off extending away from the interior surface. The printed circuit board includes a plurality of electronic components mounted on a first surface thereof, the electronic components being in electrical communication with the motor and the power source and being configured to pass electrical current from the power source to the motor to activate the motor. The thermally conductive gap pad is positioned between an in contact with the electronic component and the stand-off. The potting material at least partially encapsulates the printed circuit board within the potting boat. The secondary heat sink is positioned at least partially within the potting boat in contact with a second surface of the printed circuit board opposite the first surface. The secondary heat sink includes a plurality of secondary heat sink fins projecting from the potting boat. Heat generated by the electronic components is transferred through a primary conduction path passing through the gap pad, the stand-off, and the primary heat sink fins. Heat generated by the electronic components is also transferred through a secondary conduction path passing through the secondary heat sink and the secondary heat sink fins. Heat generated by the electronic components is dissipated along the primary conduction path and the secondary conduction path to the surroundings of the printed circuit board assembly.
The invention provides, in another aspect, a power tool coupled to a power source. The power tool includes a housing, a motor, an impeller, and a printed circuit board assembly. The housing includes an inlet opening and an exhaust opening. The impeller is rotated by the motor and configured to generate an airflow within the housing, the airflow passing from the inlet opening to the exhaust opening. The printed circuit board assembly includes a potting boat, a printed circuit board, a thermally conductive gap pad, potting material, and a secondary heat sink. The potting boat includes a plurality of primary heat sink fins, an interior surface, and at least one stand-off extending away from the interior surface. The printed circuit board includes a plurality of electronic components mounted on a first surface thereof. The plurality of electronic components are in electrical communication with the motor and the power source, and a configured to pass current from the power source to the motor to activate the motor. The thermally conductive gap pad is positioned between and in contact with both the electronic component and the stand-off. The potting material at least partially encapsulates the printed circuit board within the potting boat. The secondary heat sink is positioned at least partially within the potting boat in contact with a second surface of the printed circuit board opposite the first surface. The secondary heat sink includes a plurality of secondary heat sink fins projecting from the potting boat. Heat generated by the electronic components is transferred through a primary conduction path passing through the gap pad, the projections, and the primary heat sink fins. Heat is also transferred through a secondary conduction path passing through the secondary heat sink and the secondary heat sink fins. The heat is dissipated along the primary conduction path, the secondary conduction path, and via convection from the airflow to the surroundings of the power tool.
The invention provides, in another aspect, a printed circuit board assembly for use in a power tool including a motor and a power source. The printed circuit board assembly includes a potting boat, a printed circuit board, a thermally conductive gap pad, potting material, and a secondary heat sink. The potting boat includes an interior surface from which at least one stand-off extends, and an exterior surface with a finless section, a full length heat sink fin section from which at least one full length primary heat sink fin extends, and a partial length heat sink fin section from which at least one partial length primary heat sink fin extends. The printed circuit board includes a plurality of electronic components mounted on a first surface thereof, the electronic components being in electrical communication with the motor and the power source and being configured to pass electrical current from the power source to the motor to activate the motor. The thermally conductive gap pad is positioned between an in contact with the electronic component and the stand-off. The potting material at least partially encapsulates the printed circuit board within the potting boat. The secondary heat sink is positioned at least partially within the potting boat in contact with a second surface of the printed circuit board opposite the first surface. The secondary heat sink includes a plurality of secondary heat sink fins projecting from the potting boat. Heat generated by the electronic components is transferred through a primary conduction path passing through the gap pad, the stand-off, and both the primary heat sink fins and the partial length primary heat sink fins. Heat generated by the electronic components is also transferred through a secondary conduction path passing through the secondary heat sink and the secondary heat sink fins. Heat generated by the electronic components is dissipated along the primary conduction path and the secondary conduction path to the surroundings of the printed circuit board assembly.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
In the illustrated embodiment, the motor 18 is configured as a brushless direct current (BLDC) motor that receives power from an on-board power source 29 (e.g., a battery). The battery may include any of a number of different nominal voltages (e.g., 12V, 18V, etc.), and may be configured having any of a number of different chemistries (e.g., lithium-ion, nickel-cadmium, etc.). In some embodiments, the battery is a battery pack removably coupled to the housing 14. In other embodiments, the motor 18 may be powered by a remote power source (e.g., a household electrical outlet) through a power cord (not shown). The motor 18 is selectively activated by depressing an actuating member, such as a trigger 30, which in turn actuates an electrical switch 33. The switch 33 is electrically connected to the motor 18 via a printed circuit board assembly (PCBA) 200 (i.e., an electronic control unit 200). The PCBA 200 may include, for example, a microprocessor and/or one or more circuits for controlling operation of the motor 18.
The rotary hammer 10 further includes an impact mechanism 32 which is shiftable between a plurality of operating modes by moving a mode selection dial 130 between various positions. The mode selection dial 130 is configured to operate a mode selection assembly 300 to adjust operation of the impact mechanism 32. Depending on the position of the mode selection dial 130, the impact mechanism 32 is configured to axially and/or rotationally move the tool bit 25. In some instances, while operating the rotary hammer 10, the trigger 30 may be depressed and released to selectively activate the motor 18 at various speeds. In other instances, the trigger 30 may be held in a depressed position to continuously run the rotary hammer 10. In some embodiments, the rotary hammer 10 may include one or more control signal-based electrical overrides relating to driving the motor 18 in a direction opposite a prescribed direction. Various permutations of operating the rotary hammer 10 are possible.
As shown in
With continued reference to
The PCBA 200 also includes a printed circuit board (PCB) 216 within the potting boat 204. Electronic components (e.g., a microprocessor, field effect transistors or FETs 220, etc.) are mounted on the PCB 216. The illustrated PCBA 200 includes a plurality (e.g., six) FETs 220 mounted on the PCB 216 and configured to control the supply of electrical current to the motor 18 from the battery pack 29. The FETs 220 are switched on and off in rapid succession during operation of the motor 18, which generates heat. In some exemplary embodiments, the FETs 220 may be mounted to the PCB 216 in an H-bridge motor driver circuit. The FETs 220 are mounted on the PCB 216 at positions corresponding with the stand-offs 212.
A gap pad 224 having high thermal conductivity is positioned between the FETs 220 and the stand-offs 212. In some embodiments, a single gap pad 224 may be positioned between each of the FETs 220 and the stand-offs 212. In other embodiments, a plurality of gap pads 224 are provided, with each of the gap pads 224 positioned between a corresponding one of the FETs 220 and a corresponding one of the stand-offs 212. Heat generated by the FETs 220 is transferred through the gap pad(s) 224 and into the potting boat 204 (via the stand-offs 212). The potting boat 204 and the primary fins 208 are also be made of a heat conductive material (e.g., Aluminum) such that heat generated by the FETs 220 may be conducted (e.g., via a first conduction path) through the potting boat 204 to the primary fins 208. As the airflow AF passes the PCBA 200, heat is transferred from the primary fins 208 to the airflow AF (more specifically, a first airflow path AF1 that passes along the primary fins 208) via convection, and the heat is carried by the airflow AF through the exhaust openings 16 and to the surroundings of the rotary hammer 10. Optionally, the gap pad 224 may include at least one side having adhesive applied thereto. The adhesive may secure the gap pad 224 to either the stand-off(s) 212, one or more FETs 220, or both the stand-off(s) 212 and one or more FETs 220. The adhesive may be configured to improve efficiency of assembling the PCBA 200 without affecting thermal conductivity of the gap pad 224 and/or the PCBA 200 as a whole. In the illustrated embodiment, adhesive is not applied to the gap pad(s) 224. In some embodiments, the gap pad(s) 224 may be deformable (e.g., elastically deformable).
The PCBA 200 includes potting material 228 (
On the opposite side of the PCB 216 as the primary fins 208, the PCBA 200 further includes a secondary heat sink 232. The secondary heat sink 232 includes secondary fins 236 and mounting holes 240 (
During assembly of the PCBA 200, the PCB 216 is positioned within the potting boat 204 with the fastener holes 252, 256 of the PCB 216 and potting boat 204 aligned with one another. Gap pad(s) 224 are located between the stand-offs 212 and the FETs 220, optionally utilizing the aforementioned adhesive. The secondary heat sink 232 is positioned on the PCB 216 opposite the potting boat 204 and with the mounting holes 240 aligned with the fastener holes 252, 256. The fasteners 244 are positioned at least partially within the mounting holes 240 and the fastener holes 252, 256, and the fasteners 244 are tightened. During tightening, a clamping force is applied to the PCB 216, and the gap pad(s) 224 are pressed against the stand-offs 212. During tightening of the fasteners 244, the gap pad(s) 224 deform (i.e., deflect) to reduce or take up a gap G1 (
The stacked arrangement of the FETs 220, printed circuit board 216, and secondary heat sink 232 permits heat generated by the FETs 220 to be conducted (e.g., via a second conduction path) through the printed circuit board 216, into the secondary heat sink 232, and to the secondary fins 236 of the secondary heat sink 232. During operation of the rotary hammer 10, the motor 18 rotates to drive the impeller 19 and draw airflow AF into the motor housing 14 via the inlet openings 16. That airflow AF is directed past the PCBA 200 and the motor 18 before being exhausted from the exhaust opening 15. As the airflow AF passes the PCBA 200, heat is transferred from the secondary fins 236 of the secondary heat sink 232 to the airflow AF (more specifically, a second airflow path AF2 that passes along the secondary fins 236) via convection, and the heat is carried by the airflow AF through the exhaust openings 15 and to the surroundings of the rotary hammer 10. Depending on orientation of the PCBA 200, airflow AF generated by the impeller 19 may split between a first airflow path AF1 that passes along the primary fins 208 and a second airflow path AF2 that passes along the secondary fins 236. After passing the PCBA 200, the first airflow path AF1 and the second airflow path AF2 may converge toward one another for exhaust via the exhaust openings 15. Depending at least on orientation of the PCBA 200, sequence of airflow AF passing along the primary fins 208 and the secondary fins 236 may differ. For example, airflow AF may contact either of the primary fins 208 or the secondary fins 236 first. Alternately, the airflow AF may simultaneously contact both the primary fins 208 and the secondary fins 236. As shown in
The potting boat 304 includes a plurality of primary fins 308 that extend away from the exterior surface 304a. More specifically, primary fins 308 extend away from the exterior surface 304a at the full-length heat sink fin section 304b and the partial length fin section 304d. At the full length fin section 304b, at least one full-length primary heat sink fin 308 extends from the exterior surface 304a. The full-length primary heat sink fins 308 extend along an entire width dimension D1 of the potting boat 304 and include thicknesses and spacing from one another in a length dimension D2 of the potting boat 304. In the illustrated embodiment, the full-length primary heat sink fins 308 wrap around sidewalls 306 of the potting boat 304.
At the illustrated partial length fin section 304d, at least one partial length primary heat sink fin 308a extends from the exterior surface 304a. The partial length primary heat sink fins 308a extend a partial width (along width dimension D1) of the potting boat 304 and/or the sidewalls 306. The illustrated finless section 304c is located between adjacent partial length primary heat sink fins 308a. Along the length dimension D2, the illustrated potting boat 304 includes and alternates between a plurality of full-length fin sections 304b and a plurality of partial length fin sections 304d. At a given length dimension D2 corresponding with the partial length fin section 304d, a finless section 304c separates the partial length fins 308a from one another. In other embodiments, along the length dimension D2, the heat sink fin sections 308b, 304b may be separated from each other by the finless section 304c.
With reference to
With reference to
The PCBA 300 also includes a printed circuit board (PCB) 316 within the potting boat 304 like the PCB 216, and will not be described again in detail. The printed circuit board 316 further includes a second surface 316b opposite the first surface 316a, the second surface 316b being capable of contacting a secondary heat sink (such as the secondary heat sink 232) for dissipating heat generated by FETs 332 of the PCBA 300.
Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the invention as described.
Various features of the invention are set forth in the following claims.
This application claims priority to U.S. Provisional Patent Application No. 63/479,574 filed on Jan. 12, 2023, the entire content of which is incorporated herein by reference.
Number | Date | Country | |
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63479574 | Jan 2023 | US |